full file at http://testbankcorner.eu Exam Name _ MULTIPLE CHOICE Choose the one alternative that best completes the statement or answers the question 1) What is the adequate stimulus for nociceptors? A) change in muscle length B) cold C) touch D) pain E) warmth Answer: D Explanation: 1) A) B) C) D) E) 2) Which of the following best describes ON-center, OFF-surround cells in the retina? A) They are bipolar cells that are excited by light applied in the center of their visual fields and inhibited by light in the surrounding regions of their visual fields B) They are photoreceptors that are excited by light applied in the center of their visual fields and inhibited by light in the surrounding regions of their visual fields C) They are photoreceptors that are excited by light striking the center of the retina and inhibited by light striking the peripheral retina D) They are ganglion cells that are excited by light applied in the center of their visual fields and inhibited by light in the surrounding regions of their visual fields E) They are ganglion cells that are excited by light striking the center of the retina and inhibited by light striking the peripheral retina Answer: D Explanation: A) B) C) D) E) 3) Which of the following synapses with second-order neurons in glomeruli? A) vision B) olfaction C) taste D) touch E) both olfaction and taste Answer: E Explanation: 2) A) B) C) D) E) 3) full file at http://testbankcorner.eu 4) Which of the following cells is the precursor cell for the olfactory cells? A) basal cells B) olfactory receptor cells C) mitral cells D) ciliary cells E) support cells Answer: A Explanation: A) B) C) D) E) 5) An increase in pressure within the eye due to expansion of the aqueous humor that can eventually compromise blood flow to the eye is called A) angiogenesis B) retinitis pigmentosa C) macular degeneration D) diabetic microvascular insufficiency E) glaucoma Answer: E Explanation: 5) A) B) C) D) E) 6) Light striking what region of the retina is not detected by photoreceptors? A) optic disk B) pupil C) zonular fibers D) ciliary muscles E) cornea Answer: A Explanation: 4) A) B) C) D) E) 6) full file at http://testbankcorner.eu Figure 10.1 7) In Figure 10.1, what are the structures, in order from to 5? A) zonular fibers, suspensory ligament, fovea, retina, sclera B) suspensory ligament, aqueous humor, macula, lutea, cornea C) radial muscle, pupil, macula, choroid, sclera D) ciliary muscles, cornea, optic disc, choroid, sclera E) ciliary body, iris, fovea, retina, sclera Answer: E Explanation: A) B) C) D) E) 8) Disks of a photoreceptor are located in the and contain A) outer segment : photopigment B) synaptic terminal : transmitter C) inner segment : transmitter D) outer segment : transmitter E) inner segment : photopigment Answer: A Explanation: 7) A) B) C) D) E) 8) full file at http://testbankcorner.eu 9) receptors are better able to provide information on whether a stimulus has changed, whereas receptors are better adapted to provide information on the extent of that change A) Tonic : phasic B) Slowly adapting : tonic C) Phasic : tonic D) Tonic : clonic E) Rapidly adapting : phasic Answer: C Explanation: A) B) C) D) E) 10) Which of the following is a neurotransmitter responsible for the transmission of a painful stimulus between first- and second-order neurons? A) acetylcholine B) norepinephrine C) bradykinin D) substance P E) histamine Answer: D Explanation: 10) A) B) C) D) E) 11) The closure of sodium channels is mediated by a decrease in the cytosolic concentration of , which is degraded by A) cAMP : transducin B) cAMP : phosphodiesterase C) cGMP : transducin D) cGMP : phosphodiesterase E) cAMP : ATP synthase Answer: D Explanation: 9) A) B) C) D) E) 11) full file at http://testbankcorner.eu 12) In the optic chiasm, ganglion cells from the portion of the retina cross over, whereas the ganglion cells from the portion of the retina remain on the same side A) nasal : center B) nasal : temporal C) temporal : center D) temporal : nasal E) center : nasal Answer: B Explanation: A) B) C) D) E) 13) What is the form of energy associated with a particular stimulus type called? A) modality B) transduction C) appropriation D) perception E) adequate stimulus Answer: A Explanation: 14) A) B) C) D) E) 15) Which sensation has a receptor type that is a chemoreceptor? A) vision B) olfaction C) taste D) touch E) both olfaction and taste Answer: E Explanation: 13) A) B) C) D) E) 14) What is the enlarged area at the base of the semicircular canals, which contains hair cells, called? A) cochlea B) organ of Corti C) basilar membrane D) utricle E) ampulla Answer: E Explanation: 12) A) B) C) D) E) 15) full file at http://testbankcorner.eu 16) The hair cells are embedded within endolymph, thus, when a potassium channel opens, potassium moves the cell, causing it to A) out of : depolarize B) out of : hyperpolarize C) into : hyperpolarize D) equally into and out of : maintain its polarized state E) into : depolarize Answer: E Explanation: A) B) C) D) E) 17) Which of the following structures sits on the basilar membrane and contains the hair cells for sound? A) tympanic membrane B) helicotrema C) tectorial membrane D) organ of Corti E) basilar membrane Answer: D Explanation: 17) A) B) C) D) E) 18) Angiogenesis contributes to the cause of what visual defect in diabetes? A) myopia B) cataracts C) hyperopia D) macular degeneration E) glaucoma Answer: D Explanation: 16) A) B) C) D) E) 18) full file at http://testbankcorner.eu 19) Which receptor type is used to detect free hydrogen ion content of blood? A) chemoreceptors B) baroreceptors C) osmoreceptors D) photoreceptors E) mechanical nociceptors Answer: A Explanation: A) B) C) D) E) 20) The organ of Corti is located on what membrane? A) tympanic membrane B) plasma membrane of hair cells C) basilar membrane D) vestibular membrane E) tectorial membrane Answer: C Explanation: 20) A) B) C) D) E) 21) The primary afferent neurons from taste receptor cells terminate within what structure of the central nervous system? A) gustatory cortex B) medulla oblongata C) cerebellum D) olfactory tubercle E) thalamus Answer: B Explanation: 21) A) B) C) D) E) 22) What transmits sound energy from the outer ear to the middle ear? A) tympanic membrane B) cochlea C) basilar membrane D) ampulla E) external auditory meatus Answer: A Explanation: 19) A) B) C) D) E) 22) full file at http://testbankcorner.eu 23) Ciliary muscle is innervated by what branch of the nervous system? A) sympathetic B) parasympathetic C) somatic D) enteric E) central Answer: B Explanation: A) B) C) D) E) 24) The amplitude of a sound wave is determined by the difference in the A) pitch of the sound B) number of sound waves per second C) air molecule density in the compressed versus rarified regions of the sound wave D) energy embedded in the air molecules E) size of the air molecules in the compressed region of the sound wave Answer: C Explanation: 25) A) B) C) D) E) 26) What type of neuron in the thalamus communicates sensory information to the cerebral cortex? A) first-order B) second-order C) third-order D) forth-order E) afferent Answer: C Explanation: 24) A) B) C) D) E) 25) A refers to a single afferent neuron and all of the sensory receptors associated with that neuron A) motor unit B) sensory unit C) receptive unit D) second-order neuron E) neuronal field Answer: B Explanation: 23) A) B) C) D) E) 26) full file at http://testbankcorner.eu 27) Where is retinal found? A) ganglionic cells B) rods C) cones D) bipolar cells E) both rods and cones Answer: E Explanation: 27) A) B) C) D) E) 28) Which receptor type is used to detect linear acceleration forward or backward? A) baroreceptors B) hair cells in utricle C) hair cells in cochlea D) hair cells in semicircular canals E) osmoreceptors Answer: B Explanation: A) B) C) D) E) 29) The gate-control theory of pain modulation states that A) painful somatic signals can inhibit signals of pain B) non-painful somatic signals can inhibit signals of pain C) pain sensation must be modified within the sensory receptors D) C fibers themselves can act to modify their own pain signal E) the signal that modifies pain sensation in the spinal cord must originate from the nucleus raphe magnus Answer: B Explanation: 28) A) B) C) D) E) 29) full file at http://testbankcorner.eu 30) First-order olfactory neurons synapse with These synapses occur in clusters called A) olfactory neurons : glomeruli B) mitral cells : cribriform areas C) mitral cells : glomeruli D) olfactory neurons : cribriform areas E) bicuspid cells : glomeruli Answer: C Explanation: A) B) C) D) E) 31) What is the location of the gustatory cortex? A) frontal lobe B) temporal lobe C) parietal lobe D) brainstem E) occipital lobe Answer: C Explanation: 31) A) B) C) D) E) 32) What is the location of the medial geniculate body? A) parietal lobe B) brainstem C) thalamus D) frontal lobe E) occipital lobe Answer: C Explanation: 32) A) B) C) D) E) 33) What structure detects rotational acceleration of the head? A) cochlea B) semicircular canals C) basilar membrane D) organ of Corti E) helicotrema Answer: B Explanation: 30) A) B) C) D) E) 10 33) full file at http://testbankcorner.eu 213) Extensive convergence exists from the cones to the bipolar cells within the fovea Answer: True Explanation: False 214) The term modality refers to the form of energy that defines a specific stimulus Answer: True Explanation: 219) False 220) There are separate receptors for warm and cold Answer: True Explanation: 220) False 221) The eighth cranial nerve carries information about hearing and equilibrium from the ear to the central nervous system Answer: True Explanation: 222) False 223) The dorsal column-medial lemniscal pathway carries mechanoreceptive and proprioceptive information to the thalamus, whereas the spinothalamic tract carries thermoreceptive and nociceptive information Answer: True Explanation: 221) False 222) The photoreceptors responsible for resetting the light/dark cycle contains a photopigment called melanopsin Answer: True Explanation: 218) False 219) Taste receptor cells are located only on the tongue Answer: True Explanation: 217) False 218) A decrease in the amplitude of a receptor potential over time in the presence of a continued stimulus is called habituation Answer: True Explanation: 216) False 217) Merkel's disks are superficial mechanoreceptors located in both glabrous and hairy skin Answer: True Explanation: 215) False 216) Transcutaneous nerve stimulation describes a technique whereby current applied to the skin stimulates large diameter afferent axons (A fiber) to inhibit the transmission of a painful stimulus from the C fiber to a second-order neuron Answer: True Explanation: 214) False 215) In order to taste food, the chemicals must be dissolved in mucus Answer: True Explanation: 213) False 55 223) full file at http://testbankcorner.eu 224) Each taste receptor cell is specific to only one of the four primary tastes Answer: True Explanation: False 225) Auditory information is transmitted through the medial geniculate nucleus in the thalamus to the cortex Answer: True Explanation: 224) 225) False ESSAY Write your answer in the space provided or on a separate sheet of paper 226) Describe the process involved in focusing an image onto the retina for objects near and far and how that process is controlled Identify the two common defects in our ability to focus light on the retina and how they can be fixed Answer: As light moves from one transparent material to the next (cornea aqueous humor lens vitreous humor), those wavelengths of light are bent (refracted) Light is refracted as it moves through the interface of two transparent materials of different densities In the human eye, the lens is capable of actively modifying its refractive power through accommodation (the process of modifying the structure of the lens) The thickness of the lens can be altered by ciliary muscles that are attached to the lens by zonular fibers The ciliary muscle forms a ring around the lens such that, when it contracts, the amount of tension on the lens from the zonular fibers is reduced This reduction in radial tension on the lens causes the lens to thicken due to its inherent elasticity As the lens thickens, light is bent to a greater extent in order to focus objects that are close to the eye onto the retina When viewing something at a distance, the ciliary muscle relaxes, which increases the tension on the zonular fibers and thereby causes the lens to flatten Accommodation is under the control of the parasympathetic nervous system, whose activity stimulates ciliary muscle contraction, causing the lens to thicken as it focuses on an object that is near A distant object is brought into focus by the relaxation of the ciliary muscle induced by a decrease in parasympathetic activity However, the lens is not always able to focus the light onto the retina In myopia (near-sightedness), the lens and cornea refract the light such that the image is focused in front of the retina This can be corrected by positioning a concave lens in front of the cornea, which will cause the light to diverge before reaching the eye Hyperopia occurs because the lens cannot accommodate enough for near vision (the light is not refracted enough) Thus, the object is focused behind the retina A convex lens in front of the cornea can correct for this by causing the light to converge before reaching the eye 227) Taste involves a complex mixture of different receptors for particular classes of compounds that can be present in food Describe how taste receptors are able to detect the four primary tastes Answer: The sensation of taste derives from chemoreceptors within the mouth Those chemoreceptors are located within structures called taste buds on the tongue and roof of the mouth Taste sensitive cells are modified epithelial cells with taste receptors that bind selectively to chemicals (tastants) in the food that we ingest In order to bind, the chemical must be dissolved in saliva There are four primary tastes: salt, sour, sweet, and bitter Sour derives from the presence of hydrogen ions that block potassium channels, which causes the cells to depolarize Salty foods are sensed by the increased electrochemical driving force for movement of sodium into the cell, which would cause the cell to depolarize Sweet is mediated by the receptor linked to a G protein called gustducin, which binds to organic molecules such as sucrose to stimulate the production of cAMP This activates a protein kinase that phosphorylates a potassium channel This phosphorylation causes more potassium channels to remain in the closed state, thereby depolarizing the cell Bitter is associated with detection of nitrogenous compounds Bitter substances can be sensed by several different mechanisms: the direct binding to a receptor, which causes the closure of potassium channels, and the binding to a receptor that activates a G protein, called transducin In that case, transducin activates the enzyme phospholipase C, which leads to the production of IP3 An increase in IP3 stimulates the release of calcium from the sarcoplasmic reticulum 56 full file at http://testbankcorner.eu 228) The primary interface between the body and the external environment is the skin Thus, a variety of receptors exist within the skin for the detection of our external environment List the three classes of receptors found in the skin (with an example of each with its function), and the pathways that those stimuli must follow to reach the somatosensory cortex Answer: The three types of skin receptors are mechanoreceptors, thermoreceptors, and nociceptors Mechanoreceptors: Merkel's disks - pressure; Meissner's corpuscles - vibration; free nerve endings - light touch; Pacinian corpuscles - vibration; Ruffini's end organs - pressure Thermoreceptors: cold and warm Nociceptors: mechanical - intense mechanical; thermal - intense thermal; polymodal - intense mechanical or thermal stimuli; or specific chemicals There are two main pathways by which sensory information will travel to the somatosensory cortex: the dorsal column-medial lemniscal pathway and the spinothalamic tract The dorsal column-medial lemniscal pathway carries information from mechanoreceptors and proprioceptors In this pathway, the first-order neurons enter the dorsal horn of the spinal cord where most of the collaterals from that neuron terminate However, the main branch ascends the spinal cord within the dorsal column to the ipsilateral brainstem That first-order neuron synapses in the dorsal column nuclei of the medulla with a second-order neuron The second-order neurons cross over to the contralateral side of the medulla along the medial lemniscus and ascend to the thalamus In the thalamus, the second-order neurons synapse with third-order neurons that transmit the information to the somatosensory cortex The spinothalamic tract carries information from thermoreceptors and nociceptors The first-order neurons enter the spinal cord at the dorsal horn and travel a short distance in either direction along the spinal cord within Lissauer's tract where they will synapse with second-order neurons The second-order neurons cross over to the contralateral side and ascend to the anterolateral quadrant of the spinal cord and through the brainstem before they enter the thalamus In the thalamus, the second-order neuron synapses with the third-order neuron, which ascends to the somatosensory cortex 229) The response of every sensory receptor is governed by the law of specific nerve energies Explain this law and its consequence for a receptor's response to low- and high-intensity stimuli, along with the general process of sensory transduction Answer: The law of specific nerve energies states that a given sensory receptor is specific for a particular energy modality Thus, different modalities of energy, including light waves, sound waves, pressure, temperature, etc., are ultimately transduced into electrical energy in the form of an action potential The specific energy modality to which a receptor responds best (low energy state) is called the adequate stimulus Receptors will also respond to other energy forms, but they must be at a higher energy to activate that receptor However, our perception of a stimulus is linked to the receptor that has been activated Thus, activating a photoreceptor on the retina by pushing on the eye (pressure) will result in our perception of a flash of light even though the stimulus was pressure The process of converting one form of energy into another is called transduction For sensory transduction, a graded potential is produced, which can lead to an action potential if the stimulus is strong enough and the receptor is a part of a neuron However, not all receptors are neurons (some are modified neurons or epithelial cells that cannot produce an action potential) A graded potential in these receptor cells will stimulate a proportional release of neurotransmitter that will induce an action potential in a neighboring nerve cell 57 full file at http://testbankcorner.eu 230) Photoreceptive cells are located within the retina Describe the general structure and the cells present within the retina, and how light is converted into electrical energy within rods and cones Answer: There are three distinct layers of cells within the retina: 1) an outer layer of rods and cones (the photoreceptive cells), 2) a middle layer of bipolar cells, and 3) an inner layer of neurons called ganglion cells Light must pass through the second and third layers to reach photoreceptors The bipolar cells, along with amacrine and horizontal cells, are involved in processing visual information, while the ganglion cells are the neural cells that transmit the visual information back to the visual center of the brain The main difference between rods and cones lies in the photopigment that detects light and the sensitivity of that pigment to particular wavelengths of light In rods, the photopigment is rhodopsin The light-absorbing portion of the photopigment (rhodopsin) is retinal The other portion of that protein (opsin) determines the sensitivity of rhodopsin to particular wavelengths of light Rhodopsin is located within membranous disks that are associated with transducin and phosphodiesterase (which degrades cGMP) In the presence of cGMP, sodium channels on the cell membrane of the photoreceptor are more likely to be in the open state In the dark, phosphodiesterase is relatively inactive, allowing cGMP to be elevated and sodium channels to be maintained in the open state, which depolarizes the photoreceptor This depolarization stimulates voltage-sensitive calcium channels to remain open, which causes the release of neurotransmitter onto bipolar cells When light impinges on rhodopsin, the opsin molecule bleaches, activating transducin, which activates phosphodiesterase This will decrease the intracellular concentration of cGMP, causing sodium channels to close and the cell to hyperpolarize This hyperpolarization closes the voltage-sensitive calcium channel, which decreases the release of neurotransmitter onto the bipolar cells Rods are sensitive to low intensities of light, whereas cones require a greater intensity of light in order be activated The same mechanisms that are active in the rods are active in the cones The color sensitivity of cones derives from the three different forms of rhodopsin found in cones These molecules are most sensitive to red, green, and blue wavelengths of light 231) Nociceptors play an important role in protecting us from damaging stimuli Describe the two types of pain and the difference between discriminative and affective pain Describe the gate-control theory of pain modulation Answer: Activation of nociceptors leads to the perception of pain That perception of pain can lead to several possible responses that include a reflex withdrawal from the stimulus, increased autonomic response, or an emotional response We perceive pain in two ways, which are termed as fast pain and slow pain Fast pain is perceived as a sharp, pricking sensation that can be easily localized and is transmitted over A fibers Slow pain is detected as a poorly localized, dull ache that is transmitted over C fibers The primary afferents from nociceptors synapse with second-order receptors in the spinal cord The discriminative properties of pain relate directly to our perception of pain At the same time, activation of that pathway will stimulate (coactivate) a second pathway that assesses the affective component of the painful stimulus The affective component of a painful stimulus is the aspect of pain that is not associated with the pain itself, as in the case of an autonomic or emotional response to pain The pathway utilized by the affective components of pain ascends through the reticular formation of the brainstem, to the hypothalamus, and to the limbic system The gate-control theory of pain modulation maintains that a non-painful somatic stimulus can inhibit pain signals at the level of the spinal cord There are many interneurons within the spinal cord; one type of these is inhibitory for second-order nociceptive neurons If this interneuron is active, then the transmission of the painful message will be diminished and the perception of pain will be lessened The inhibitory interneuron is activated by A fibers (associated with mechanical stimuli) and inhibited by collaterals from C fibers (nociceptors) However, when the two neuronal tracts are activated, collaterals from the A fibers will stimulate the inhibitory interneuron, thus decreasing the transmission of the painful message 58 full file at http://testbankcorner.eu 232) Within the inner ear are several structures that are involved in equilibrium and balance Describe these structures and how they are able to detect changes in velocity and direction Answer: The vestibular organs in the inner ear are composed of the semicircular canals (of which there are three) and two otolithic organs (utricle and saccule) They are able to detect a change in linear and rotational velocity (acceleration or deceleration) The vestibular apparatus is located within the temporal bone and consists of a membranous labyrinth that is filled with endolymph and is surrounded by perilymph The three semicircular canals are located perpendicular to one another, allowing them to detect rotational movement of the head in three planes The anterior canal detects rotation in the up and down direction, as when nodding "yes." The posterior canal detects motion of the head from side to side, as when the ear moves toward the shoulder The lateral canal detects rotation of the head from side to side, as when shaking the head to say "no." These canals contain an enlarged region called the ampulla where the sensory cells are located Within the ampulla is the cupula, a gelatinous mass in contact with the stereocilia that project from the hair cells Bending of the stereocilia causes a change in membrane potential of the hair cell The stereocilia are bent by endolymph pushing against the cupula As the head is put into motion (accelerates), the endolymph lags behind, causing it to move within the canal, which pushes on the cupula This movement of the cupula bends the stereocilia, thereby altering the membrane potential of the hair cell If that acceleration of the head reaches a constant velocity (acceleration is an increase in velocity whereas deceleration is a decrease in velocity), the endolymph will stop moving within the canal as the head comes to a constant velocity and the stereocilia will no longer be stimulated Any change in velocity (acceleration or deceleration) would cause the endolymph to move again within the canal and thereby stimulate the stereocilia Otoliths are the small calcium carbonate crystals that are embedded within the gelatinous mass in contact with the stereocilia of the hair cells The hair cells of the utricle are oriented horizontally with the stereocilia extending vertically, while the hair cells of the saccule are oriented vertically with the stereocilia extending horizontally Thus, the utricle can detect forward and backward acceleration while the saccule detects upward and downward acceleration Again, the otolith lags behind the movement of the body, causing the bending of the stereocilia of the hair cell that alters membrane potential of the hair cell 233) What are the components of sound that are detected within the ear, and how does that sound reach the inner ear where it is transduced into electrical energy? Answer: Sound waves travel and affect the gas molecules that compose the air by putting them into motion Sound waves traveling through the air consist of regions where the air molecules are closer together (compressed) and regions where those molecules are further apart (rarified) The amplitude of sound is proportional to the differences in air molecule densities between the compressed and rarified air Amplitude is expressed as a log scale in decibels The pitch of the sound is determined by the frequency of the sound waves measured as the number of waves per second (hertz: Hz) To detect sound, the properties of the sound wave must be transmitted to a solid structure That transition occurs at the ear drum where sound waves cause the tympanic membrane to vibrate at the frequency of the sound waves That vibration is passed along the middle ear across three bones: from the malleus (hammer), to the incus (anvil), and finally, onto the stapes (stirrup) The stapes is in contact with the cochlea at the oval window Once the vibration reaches the stapes, it is passed to the oval window, which vibrates the fluid of the cochlea There are two membranes within the cochlea (basilar and vestibular) that separate the cochlea into three fluid filled compartments (scala vestibuli, scala tympani, and scala media) The tympani and vestibuli are filled with perilymph while the media is filled with endolymph Vibration is passed from the oval window to the scala vestibuli onto the scala tympani This will cause the basilar and vestibular membranes to vibrate as well The organ of Corti, which contains the hair cells that detect sound, is located on the top of the basilar membrane The stereocilia of the hair cells are embedded within the tectorial membrane When the basilar membrane vibrates, the stereocilia that are attached to the tectorial membrane are sheared This movement bends the stereocilia, causing a change in membrane potential within the hair cell 59 full file at http://testbankcorner.eu 234) All receptors, by definition, must transduce the energy from a stimulus into an electrical signal before that information can be sent to the central nervous system Once that electrical signal is generated, how does the brain decode the type, intensity, duration, and location of a stimulus? Answer: Our perception of a stimulated receptor is based upon the sensory pathway activated and the region of the brain where those pathways terminate Thus, activation of an auditory neuron will result in the perception of sound independent of how that neuron was activated The specific pathway that transmits information is referred to as labeled lines, with each sensory receptor having its own unique labeled line Stimulus intensity is coded for in two ways: 1) action potential frequency (frequency coding) and 2) the number of receptors activated (population coding) As stimulus intensity increases, the magnitude of the graded potential will increase, resulting in more frequent action potentials (increased frequency) Alternatively, a stronger stimulus could activate more receptors The number of receptors activated depends upon the size and density of each receptor's receptive field Slowly adapting receptors work best for coding intensity while rapidly adapting receptors are better for coding change (not magnitude of change) The location of a stimulus is coded by location of their receptive field The precision with which we can perceive location is called acuity Acuity for a particular stimulus will depend upon a receptive field's size, number of receptors, the extent of overlap, and its lateral inhibition These can vary considerably between receptive fields throughout the body Lateral inhibition describes a situation where input from a strongly stimulated receptor will inhibit the afferent pathway transmitting information from nearby receptors 235) Describe the neural pathway of vision from the photoreceptor to the primary visual cortex How are we able to perceive the three-dimensional character of the world around us? Answer: Throughout the retina, varying numbers of photoreceptors converge onto a bipolar cell These cells are capable of generating graded potentials, the nature of which is determined by the photoreceptor Two types of photoreceptors are present within the retina: those that release excitatory neurotransmitters and those that release inhibitory neurotransmitters As neurotransmitter release is reduced when the photoreceptor is activated by light, the bipolar cells are either depolarized or hyperpolarized Thus, some bipolar cells are activated by light while others are inhibited by light In addition, the synapse between the photoreceptor and bipolar cells can be modulated by horizontal cells When depolarized, the bipolar cells release their neurotransmitter onto a ganglion cell The direction of the response from the ganglion cell will depend upon whether the neurotransmitter from the bipolar cells is excitatory or inhibitory Ganglion cells are the first-order neurons in the pathway of vision and are therefore the first cells capable of generating an action potential The axons of the ganglion cells form the optic nerve and exit the eye at the optic disk The two bundles of nerves combine at the base of the brain to form the optic chiasm In the optic chiasm, half of the axons from each eye cross over The cells from the nasal portion of the eye cross over to combine with the temporal portion of the eye from the other side The ganglion cells terminate in the lateral geniculate body of the thalamus, where they synapse with the neurons that ascend to the primary visual cortex Depth perception is dependent upon the brain receiving input from both eyes The region of the visual field that is detected by both eyes is the binocular visual field Within this area, we are able to perceive depth The cortex uses the difference in angle between the visual field of both eyes to perceive a three-dimensional image 60 full file at http://testbankcorner.eu Answer Key Testname: C10 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20) 21) 22) 23) 24) 25) 26) 27) 28) 29) 30) 31) 32) 33) 34) 35) 36) 37) 38) 39) 40) 41) 42) 43) 44) 45) 46) 47) 48) 49) 50) D D E A E A E A C D D B A E E E D D A C B A B C B C E B B C C C B E E D D C E A C D E B B B E A D E 61 full file at http://testbankcorner.eu Answer Key Testname: C10 51) 52) 53) 54) 55) 56) 57) 58) 59) 60) 61) 62) 63) 64) 65) 66) 67) 68) 69) 70) 71) 72) 73) 74) 75) 76) 77) 78) 79) 80) 81) 82) 83) 84) 85) 86) 87) 88) 89) 90) 91) 92) 93) 94) 95) 96) 97) 98) 99) 100) E A E C B D A C D A A A B E C A D C A C C C B B D A A E A D E C E A B A D B C B B D B C E D E C A E 62 full file at http://testbankcorner.eu Answer Key Testname: C10 101) 102) 103) 104) 105) 106) 107) 108) 109) 110) 111) 112) 113) 114) 115) 116) 117) 118) 119) 120) 121) 122) 123) 124) 125) 126) 127) 128) 129) 130) 131) 132) 133) 134) 135) 136) 137) 138) 139) 140) 141) 142) 143) 144) 145) 146) 147) 148) 149) 150) C D C A E D D E A A A A E D E B C C E A D C E E E A E E C B C D E B A D D E A B D C C B A A C A A A 63 full file at http://testbankcorner.eu Answer Key Testname: C10 151) 152) 153) 154) 155) 156) 157) 158) 159) 160) 161) 162) 163) 164) 165) 166) 167) 168) 169) 170) 171) 172) 173) 174) 175) 176) 177) 178) 179) 180) 181) 182) 183) 184) 185) 186) 187) 188) 189) 190) 191) 192) 193) 194) 195) 196) 197) 198) 199) 200) E D A B D B D E C E B E A E C C C C D E C D A A C C C C analgesia depolarization fovea contraction endolymph sound small Nociceptors convex Rods Rods parasympathetic TRUE FALSE FALSE FALSE TRUE TRUE TRUE FALSE FALSE FALSE 64 full file at http://testbankcorner.eu Answer Key Testname: C10 201) 202) 203) 204) 205) 206) 207) 208) 209) 210) 211) 212) 213) 214) 215) 216) 217) 218) 219) 220) 221) 222) 223) 224) 225) 226) TRUE TRUE FALSE TRUE FALSE FALSE TRUE TRUE TRUE FALSE TRUE TRUE FALSE TRUE FALSE TRUE TRUE FALSE FALSE TRUE TRUE TRUE TRUE FALSE TRUE As light moves from one transparent material to the next (cornea aqueous humor lens vitreous humor), those wavelengths of light are bent (refracted) Light is refracted as it moves through the interface of two transparent materials of different densities In the human eye, the lens is capable of actively modifying its refractive power through accommodation (the process of modifying the structure of the lens) The thickness of the lens can be altered by ciliary muscles that are attached to the lens by zonular fibers The ciliary muscle forms a ring around the lens such that, when it contracts, the amount of tension on the lens from the zonular fibers is reduced This reduction in radial tension on the lens causes the lens to thicken due to its inherent elasticity As the lens thickens, light is bent to a greater extent in order to focus objects that are close to the eye onto the retina When viewing something at a distance, the ciliary muscle relaxes, which increases the tension on the zonular fibers and thereby causes the lens to flatten Accommodation is under the control of the parasympathetic nervous system, whose activity stimulates ciliary muscle contraction, causing the lens to thicken as it focuses on an object that is near A distant object is brought into focus by the relaxation of the ciliary muscle induced by a decrease in parasympathetic activity However, the lens is not always able to focus the light onto the retina In myopia (near-sightedness), the lens and cornea refract the light such that the image is focused in front of the retina This can be corrected by positioning a concave lens in front of the cornea, which will cause the light to diverge before reaching the eye Hyperopia occurs because the lens cannot accommodate enough for near vision (the light is not refracted enough) Thus, the object is focused behind the retina A convex lens in front of the cornea can correct for this by causing the light to converge before reaching the eye 65 full file at http://testbankcorner.eu Answer Key Testname: C10 227) The sensation of taste derives from chemoreceptors within the mouth Those chemoreceptors are located within structures called taste buds on the tongue and roof of the mouth Taste sensitive cells are modified epithelial cells with taste receptors that bind selectively to chemicals (tastants) in the food that we ingest In order to bind, the chemical must be dissolved in saliva There are four primary tastes: salt, sour, sweet, and bitter Sour derives from the presence of hydrogen ions that block potassium channels, which causes the cells to depolarize Salty foods are sensed by the increased electrochemical driving force for movement of sodium into the cell, which would cause the cell to depolarize Sweet is mediated by the receptor linked to a G protein called gustducin, which binds to organic molecules such as sucrose to stimulate the production of cAMP This activates a protein kinase that phosphorylates a potassium channel This phosphorylation causes more potassium channels to remain in the closed state, thereby depolarizing the cell Bitter is associated with detection of nitrogenous compounds Bitter substances can be sensed by several different mechanisms: the direct binding to a receptor, which causes the closure of potassium channels, and the binding to a receptor that activates a G protein, called transducin In that case, transducin activates the enzyme phospholipase C, which leads to the production of IP3 An increase in IP3 stimulates the release of calcium from the sarcoplasmic reticulum 228) The three types of skin receptors are mechanoreceptors, thermoreceptors, and nociceptors Mechanoreceptors: Merkel's disks - pressure; Meissner's corpuscles - vibration; free nerve endings - light touch; Pacinian corpuscles - vibration; Ruffini's end organs - pressure Thermoreceptors: cold and warm Nociceptors: mechanical - intense mechanical; thermal - intense thermal; polymodal - intense mechanical or thermal stimuli; or specific chemicals There are two main pathways by which sensory information will travel to the somatosensory cortex: the dorsal column-medial lemniscal pathway and the spinothalamic tract The dorsal column-medial lemniscal pathway carries information from mechanoreceptors and proprioceptors In this pathway, the first-order neurons enter the dorsal horn of the spinal cord where most of the collaterals from that neuron terminate However, the main branch ascends the spinal cord within the dorsal column to the ipsilateral brainstem That first-order neuron synapses in the dorsal column nuclei of the medulla with a second-order neuron The second-order neurons cross over to the contralateral side of the medulla along the medial lemniscus and ascend to the thalamus In the thalamus, the second-order neurons synapse with third-order neurons that transmit the information to the somatosensory cortex The spinothalamic tract carries information from thermoreceptors and nociceptors The first-order neurons enter the spinal cord at the dorsal horn and travel a short distance in either direction along the spinal cord within Lissauer's tract where they will synapse with second-order neurons The second-order neurons cross over to the contralateral side and ascend to the anterolateral quadrant of the spinal cord and through the brainstem before they enter the thalamus In the thalamus, the second-order neuron synapses with the third-order neuron, which ascends to the somatosensory cortex 229) The law of specific nerve energies states that a given sensory receptor is specific for a particular energy modality Thus, different modalities of energy, including light waves, sound waves, pressure, temperature, etc., are ultimately transduced into electrical energy in the form of an action potential The specific energy modality to which a receptor responds best (low energy state) is called the adequate stimulus Receptors will also respond to other energy forms, but they must be at a higher energy to activate that receptor However, our perception of a stimulus is linked to the receptor that has been activated Thus, activating a photoreceptor on the retina by pushing on the eye (pressure) will result in our perception of a flash of light even though the stimulus was pressure The process of converting one form of energy into another is called transduction For sensory transduction, a graded potential is produced, which can lead to an action potential if the stimulus is strong enough and the receptor is a part of a neuron However, not all receptors are neurons (some are modified neurons or epithelial cells that cannot produce an action potential) A graded potential in these receptor cells will stimulate a proportional release of neurotransmitter that will induce an action potential in a neighboring nerve cell 66 full file at http://testbankcorner.eu Answer Key Testname: C10 230) There are three distinct layers of cells within the retina: 1) an outer layer of rods and cones (the photoreceptive cells), 2) a middle layer of bipolar cells, and 3) an inner layer of neurons called ganglion cells Light must pass through the second and third layers to reach photoreceptors The bipolar cells, along with amacrine and horizontal cells, are involved in processing visual information, while the ganglion cells are the neural cells that transmit the visual information back to the visual center of the brain The main difference between rods and cones lies in the photopigment that detects light and the sensitivity of that pigment to particular wavelengths of light In rods, the photopigment is rhodopsin The light-absorbing portion of the photopigment (rhodopsin) is retinal The other portion of that protein (opsin) determines the sensitivity of rhodopsin to particular wavelengths of light Rhodopsin is located within membranous disks that are associated with transducin and phosphodiesterase (which degrades cGMP) In the presence of cGMP, sodium channels on the cell membrane of the photoreceptor are more likely to be in the open state In the dark, phosphodiesterase is relatively inactive, allowing cGMP to be elevated and sodium channels to be maintained in the open state, which depolarizes the photoreceptor This depolarization stimulates voltage-sensitive calcium channels to remain open, which causes the release of neurotransmitter onto bipolar cells When light impinges on rhodopsin, the opsin molecule bleaches, activating transducin, which activates phosphodiesterase This will decrease the intracellular concentration of cGMP, causing sodium channels to close and the cell to hyperpolarize This hyperpolarization closes the voltage-sensitive calcium channel, which decreases the release of neurotransmitter onto the bipolar cells Rods are sensitive to low intensities of light, whereas cones require a greater intensity of light in order be activated The same mechanisms that are active in the rods are active in the cones The color sensitivity of cones derives from the three different forms of rhodopsin found in cones These molecules are most sensitive to red, green, and blue wavelengths of light 231) Activation of nociceptors leads to the perception of pain That perception of pain can lead to several possible responses that include a reflex withdrawal from the stimulus, increased autonomic response, or an emotional response We perceive pain in two ways, which are termed as fast pain and slow pain Fast pain is perceived as a sharp, pricking sensation that can be easily localized and is transmitted over A fibers Slow pain is detected as a poorly localized, dull ache that is transmitted over C fibers The primary afferents from nociceptors synapse with second-order receptors in the spinal cord The discriminative properties of pain relate directly to our perception of pain At the same time, activation of that pathway will stimulate (coactivate) a second pathway that assesses the affective component of the painful stimulus The affective component of a painful stimulus is the aspect of pain that is not associated with the pain itself, as in the case of an autonomic or emotional response to pain The pathway utilized by the affective components of pain ascends through the reticular formation of the brainstem, to the hypothalamus, and to the limbic system The gate-control theory of pain modulation maintains that a non-painful somatic stimulus can inhibit pain signals at the level of the spinal cord There are many interneurons within the spinal cord; one type of these is inhibitory for second-order nociceptive neurons If this interneuron is active, then the transmission of the painful message will be diminished and the perception of pain will be lessened The inhibitory interneuron is activated by A fibers (associated with mechanical stimuli) and inhibited by collaterals from C fibers (nociceptors) However, when the two neuronal tracts are activated, collaterals from the A fibers will stimulate the inhibitory interneuron, thus decreasing the transmission of the painful message 67 full file at http://testbankcorner.eu Answer Key Testname: C10 232) The vestibular organs in the inner ear are composed of the semicircular canals (of which there are three) and two otolithic organs (utricle and saccule) They are able to detect a change in linear and rotational velocity (acceleration or deceleration) The vestibular apparatus is located within the temporal bone and consists of a membranous labyrinth that is filled with endolymph and is surrounded by perilymph The three semicircular canals are located perpendicular to one another, allowing them to detect rotational movement of the head in three planes The anterior canal detects rotation in the up and down direction, as when nodding "yes." The posterior canal detects motion of the head from side to side, as when the ear moves toward the shoulder The lateral canal detects rotation of the head from side to side, as when shaking the head to say "no." These canals contain an enlarged region called the ampulla where the sensory cells are located Within the ampulla is the cupula, a gelatinous mass in contact with the stereocilia that project from the hair cells Bending of the stereocilia causes a change in membrane potential of the hair cell The stereocilia are bent by endolymph pushing against the cupula As the head is put into motion (accelerates), the endolymph lags behind, causing it to move within the canal, which pushes on the cupula This movement of the cupula bends the stereocilia, thereby altering the membrane potential of the hair cell If that acceleration of the head reaches a constant velocity (acceleration is an increase in velocity whereas deceleration is a decrease in velocity), the endolymph will stop moving within the canal as the head comes to a constant velocity and the stereocilia will no longer be stimulated Any change in velocity (acceleration or deceleration) would cause the endolymph to move again within the canal and thereby stimulate the stereocilia Otoliths are the small calcium carbonate crystals that are embedded within the gelatinous mass in contact with the stereocilia of the hair cells The hair cells of the utricle are oriented horizontally with the stereocilia extending vertically, while the hair cells of the saccule are oriented vertically with the stereocilia extending horizontally Thus, the utricle can detect forward and backward acceleration while the saccule detects upward and downward acceleration Again, the otolith lags behind the movement of the body, causing the bending of the stereocilia of the hair cell that alters membrane potential of the hair cell 233) Sound waves travel and affect the gas molecules that compose the air by putting them into motion Sound waves traveling through the air consist of regions where the air molecules are closer together (compressed) and regions where those molecules are further apart (rarified) The amplitude of sound is proportional to the differences in air molecule densities between the compressed and rarified air Amplitude is expressed as a log scale in decibels The pitch of the sound is determined by the frequency of the sound waves measured as the number of waves per second (hertz: Hz) To detect sound, the properties of the sound wave must be transmitted to a solid structure That transition occurs at the ear drum where sound waves cause the tympanic membrane to vibrate at the frequency of the sound waves That vibration is passed along the middle ear across three bones: from the malleus (hammer), to the incus (anvil), and finally, onto the stapes (stirrup) The stapes is in contact with the cochlea at the oval window Once the vibration reaches the stapes, it is passed to the oval window, which vibrates the fluid of the cochlea There are two membranes within the cochlea (basilar and vestibular) that separate the cochlea into three fluid filled compartments (scala vestibuli, scala tympani, and scala media) The tympani and vestibuli are filled with perilymph while the media is filled with endolymph Vibration is passed from the oval window to the scala vestibuli onto the scala tympani This will cause the basilar and vestibular membranes to vibrate as well The organ of Corti, which contains the hair cells that detect sound, is located on the top of the basilar membrane The stereocilia of the hair cells are embedded within the tectorial membrane When the basilar membrane vibrates, the stereocilia that are attached to the tectorial membrane are sheared This movement bends the stereocilia, causing a change in membrane potential within the hair cell 68 full file at http://testbankcorner.eu Answer Key Testname: C10 234) Our perception of a stimulated receptor is based upon the sensory pathway activated and the region of the brain where those pathways terminate Thus, activation of an auditory neuron will result in the perception of sound independent of how that neuron was activated The specific pathway that transmits information is referred to as labeled lines, with each sensory receptor having its own unique labeled line Stimulus intensity is coded for in two ways: 1) action potential frequency (frequency coding) and 2) the number of receptors activated (population coding) As stimulus intensity increases, the magnitude of the graded potential will increase, resulting in more frequent action potentials (increased frequency) Alternatively, a stronger stimulus could activate more receptors The number of receptors activated depends upon the size and density of each receptor's receptive field Slowly adapting receptors work best for coding intensity while rapidly adapting receptors are better for coding change (not magnitude of change) The location of a stimulus is coded by location of their receptive field The precision with which we can perceive location is called acuity Acuity for a particular stimulus will depend upon a receptive field's size, number of receptors, the extent of overlap, and its lateral inhibition These can vary considerably between receptive fields throughout the body Lateral inhibition describes a situation where input from a strongly stimulated receptor will inhibit the afferent pathway transmitting information from nearby receptors 235) Throughout the retina, varying numbers of photoreceptors converge onto a bipolar cell These cells are capable of generating graded potentials, the nature of which is determined by the photoreceptor Two types of photoreceptors are present within the retina: those that release excitatory neurotransmitters and those that release inhibitory neurotransmitters As neurotransmitter release is reduced when the photoreceptor is activated by light, the bipolar cells are either depolarized or hyperpolarized Thus, some bipolar cells are activated by light while others are inhibited by light In addition, the synapse between the photoreceptor and bipolar cells can be modulated by horizontal cells When depolarized, the bipolar cells release their neurotransmitter onto a ganglion cell The direction of the response from the ganglion cell will depend upon whether the neurotransmitter from the bipolar cells is excitatory or inhibitory Ganglion cells are the first-order neurons in the pathway of vision and are therefore the first cells capable of generating an action potential The axons of the ganglion cells form the optic nerve and exit the eye at the optic disk The two bundles of nerves combine at the base of the brain to form the optic chiasm In the optic chiasm, half of the axons from each eye cross over The cells from the nasal portion of the eye cross over to combine with the temporal portion of the eye from the other side The ganglion cells terminate in the lateral geniculate body of the thalamus, where they synapse with the neurons that ascend to the primary visual cortex Depth perception is dependent upon the brain receiving input from both eyes The region of the visual field that is detected by both eyes is the binocular visual field Within this area, we are able to perceive depth The cortex uses the difference in angle between the visual field of both eyes to perceive a three-dimensional image 69 ... Explanation: 87) A) B) C) D) E) 26 89) full file at http://testbankcorner.eu 90) Which of the following is the correct order of communication of visual information in the retina? A) photoreceptor, ganglion... presence of cGMP in the cytosol of a photoreceptor will directly stimulate the A) opening of sodium channels B) opening of calcium channels C) closure of sodium channels D) opening of potassium... 66) full file at http://testbankcorner.eu 67) How is the intensity of a stimulus encoded during information transmittal to the central nervous system? A) The amplitude of action potentials transmitted