Human physiology chapter 7 review questions

Choose the true statement:

A. the modality of energy a given sensory receptor responds to in normal functioning is known as the “adequate stimulus” for that receptor

B. receptor potentials are “all-or-none” - that is, they have the same magnitude regardless of the strength of the stimulus

C. when the frequency of action potentials along sensory neurons is constant as long as a stimulus continues, it is called “adaptation”

D. when sensory units have large receptive fields, the acuity of perception is greater

E. the “modality” refers to the intensity of a given stimulus

A

for example, photons of light are the adequate stimulus for photoreceptors of the eye, and sound is the adequate stimulus for hair cells of the ear

Using a single intracellular recording electrode, in what part of a sensory neuron could you simultaneously record both receptor potentials and action potentials?

a. in the cell body

b. at the node of Ranvier nearest the peripheral end

c. at the axon hillock where the axon meets the cell body

d. at the central axon terminals within the CNS

e. there is no single point where both can be measured

b

Receptor potentials generate only local currents in the receptor membrane that transduces the stimulus, but when they reach the first node of Ranvier, they depolarize the membrane threshold, and there the voltage-gated Na+ channels first initiate action potentials. Beyond that point, the receptor potential decreases with distance, whereas action potentials propagate all the way to the central axon terminals.

Which best describes “lateral inhibition” in sensory processing?

a. presynaptic axo-axonal synapses reduce neurotransmitter released at excitatory synapses

b. when a stimulus is maintained for a long time, action potentials from sensory receptors decrease in frequency with time

c. descending inputs from the brainstem inhibit afferent pain pathways in the spinal cord

d. inhibitory interneurons decrease action potentials from receptors at the periphery of a stimulated region

e. receptor potentials increase in magnitude with the strength of a stimulus

d

Lateral inhibition increases the contrast between the region at the center of a stimulus and regions at the edges of the stimulus, which increases the acuity of stimulus localization

What region of the brain contains the primary visual cortex?

a. occipital lobe

b. frontal lobe

c. temporal lobe

d. somatosensory cortex

e. parietal lobe association area

a

The occipital lobe of the cortex is the initial site of visual processing.

Which type of receptor does not encode a somatic sensation?

a. muscle-spindle stretch receptor

b. nociceptor

c. Pacinian corpuscle

d. thermoreceptor

e. cochlear hair cell

e

Somatic sensations include those from the skin, muscles, bones, tendons, and joints, but not encoding of sound by cochlear hair cells.

Which best describes the vision of a person with uncorrected nearsightedness?

a. the eyeball is too long; far objects focus on the retina when the ciliary muscle contracts

b. the eyeball is too long; near objects focus on the retina when the ciliary muscle is relaxed

c. the eyeball is too long; near objects cannot be focused on the retina

d. the eyeball is too short; far objects cannot be focused on the retina

e. the eyeball is too short; near objects focus on the retina when the ciliary muscle is relaxed

b

A person with uncorrected nearsightedness (myopia) has an eyeball that is too long. When the ciliary muscles are relaxed and the lens is as flat as possible, parallel light rays from distant objects focus in front of the retina, whereas diverging rays from near objects are able to focus on the retina.

If a patient suffers a stroke that destroys the optic tract on the right side of the brain, which of the following visual defects will result?

a. complete blindness will result

b. there will be no vision in the left eye, but vision will be normal in the right eye

c. the patient will not perceive images of objects striking the left half of the retina in the left eye

d. the patient will not perceive images of objects striking the right half of the retina in the right eye

e. neither eye will perceive objects in the right side of the patient’s field of view

d

When the right optic tract is destroyed, perception of images formed on the right half of the retina in both eyes is lost, so nothing is visible at the left side of a person’s field of view

Which correctly describes a step in auditory signal transduction?

a. displacement of the basilar membrane with respect to the tectorial membrane stimulates on the hair cells

b. pressure waves on the oval window cause vibrations of the malleus, which are transferred via the stapes to the round window

c. movement of the stapes causes oscillations in the tympanic membrane, which is in contact with the endolymph

d. oscillations of the stapes against the oval window set up pressure waves in the semicircular canals

e. the malleus, incus, and stapes are found in the inner ear, within the cochlea

a

Pressure waves traveling down the cochlea make the cochlear duct vibrate, moving the basilar membrane against the stationary tectorial membrane and bending the hair cells that bridge the gap between the two

A standing subject looking over her left shoulder suddenly rotates her head to look over her right shoulder. How does the vestibular system detect this motion?

a. the utricle goes from a vertical to a horizontal position, and otoliths stimulate stereocilia

b. stretch receptors in neck muscles send action potentials to the vestibular apparatus, which relays them to the brain

c. fluid within the semicircular canals remains stationary, bending the cupula and stereocilia as the head rotates

d. the movement causes endolymph in the cochlea to rotate from right to left, stimulating inner hair cells

e. counterrotation of the aqueous humor activates a nystagmus response

c

With the sudden head rotation from left to right, inertia of the endolymph causes it to rotate from left to right with respect to the semicircular canal that lies in the horizontal plane. This fluid flow bends the cupula and embedded hair cells within the ampulla, which influences the firing of action potentials along the vestibular nerve.

Which category of taste receptor cells does MSG (monosodium glutamate) most strongly stimulate?

a. salty

b. bitter

c. sweet

d. umami

e. sour

d

Umami is derived from the Japanese word meaning “delicious” or “savory”; the stimulation of these taste receptors by glutamate produces the perception of a rich, meaty flavor.

Describe several mechanisms by which pain could theoretically be controlled medically or surgically.

a) Use drugs to block transmission in the pathways that convey information about pain to the brain. For example, if substance P is the neurotransmitter at the central endings of the nociceptor afferent fibers, give a drug that blocks the substance P receptors. b) Cut the dorsal root at the level of entry of the nociceptor fibers to prevent transmission of their action potentials into the central nervous system. c) Give a drug that activates receptors in the descending pathways that block transmission of the incoming or ascending pain information.

At what two sites would central nervous system injuries interfere with the perception that heat is being applied to the right side of the body? At what single site would a central nervous system injury interfere with perception that heat is being applied to either side of the body?

Information regarding temperature is carried via the anterolateral system to the brain. Fibers of this system cross to the opposite side of the body in the spinal cord at the level of entry of the afferent fibers. Damage to the left side of the spinal cord or any part of the left side of the brain that contains fibers of the pathways for temperature would interfere with awareness of a heat stimulus on the right. Thus, damage to the somatosensory cortex of the left cerebral hemisphere (that is, opposite the stimulus) would interfere with awareness of the stimulus. Injury to the spinal cord at the point at which fibers of the anterolateral system from the two halves of the spinal cord cross to the opposite side would interfere with the awareness of heat applied to either side of the body, as would the unlikely event that damage occurred to relevant areas of both sides of the brain.

What would vision be like after a drug has destroyed all the cones in the retina?

Vision would be restricted to the rods; therefore, it would be normal at very low levels of illumination. At higher levels of illumination, however, clear vision of fine details would be lost, particularly from the center of the visual field where cones are concentrated, and everything would appear in shades of gray, with no color vision. In very bright light, there would be no vision because of bleaching of the rods’ rhodopsin.

Damage to what parts of the cerebral cortex could explain the following behaviors? a) A person walks into chair placed in her path b) The person does not walk into the chair, but she does not know what the chair can be used for

a) the individual lacks a functioning primary visual cortex b) the individual lacks a functioning visual association cortex

How could the concept of referred pain potentially complicate the clinical assessment of the source of a patient’s somatic pain?

Because it is common for somatic receptors in visceral organs to converge onto ascending pathways for receptors in the skin, muscles, and joints, physicians must be aware that complaints about pain in superficial structures may indicate a deeper problem. For example, a person having a heart attack may complain of pain in the left arm, a patient with stomach cancer may experience pain in the middle of the back, and a patient with kidney stones may complain of an ache in the upper thigh or hip.

A key principle of physiology is that homeostasis is essential for health and survival. How might sensory receptors responsible for detecting painful stimuli (nociceptors) contribute to homeostasis?

Nociceptors detect stimuli indicating potential or actual damage to tissues, which could threaten homeostasis. By allowing us to perceive those stimuli, nociceptors not only help us learn to avoid them but also let us respond quickly to minimize damage when they occur. In these ways, we can avoid injuries like burns or cuts that may threaten homeostasis by causing fluid loss from the body.

How does the sensory transduction mechanism in the vestibular and auditory systems demonstrate the importance of the general principles of physiology that controlled exchange of materials occurs between compartments and across cellular membranes?

A good example of the importance of controlled exchange between extracellular compartments in the vestibular and auditory systems is the endolymph found within the cochlear duct and vestibular apparatus. The unusually high K+ concentration allows current to flow into the cells when tip links are stretched, generating a receptor potential that leads to neurotransmitter release from the hair cells. This, in turn, generates action potentials in the afferent neuron. In addition, like in all neurons and excitable cells, the maintenance of Na+ and K+ concentration gradients between the intracellular and extracellular fluid compartments by Na+/K+-ATPase pumps is essential for the transmission of action potentials in the auditory and vestibular afferent neurons.

Elaboration of surface area to maximize functional capability is a common motif in the body illustrating the general principle of physiology that structure is a determinate of - and has coevolved with - function. Cite an example from this chapter.

An excellent example of a body structure that has maximized surface area to maximize function is a photoreceptor cell. Repeated foldings of the membranous discs in rods and cones greatly increases the surface area available for the retinal-containing photo pigments, making the eye exquisitely sensitive to light.