Module 7

Question 1

Define sensory receptor

Answer 1

receptors that detect environmental stimuli and convert information into action potentials

Question 2

Define adequate stimulus

Answer 2

the form of environmental stimulus to which the sensory receptor is most sensitive

Question 3

List 4 characteristics of generator potentials

Answer 3

generally depolarizing; caused by increased permeability to Na+ ions; local and do not propagate down the neuron (more like an EPSP); proportional to strength of stimulus

Question 4

List 4 kinds of environmental stimuli and an example of each

Answer 4

mechanical (touch, pressure, vibration, proprioception, sound); chemical (taste, pain, odor); electromagnetic (light); other (gravity, motion, acceleration, heat)

Question 5

Define cutaneous receptors

Answer 5

sensory receptors in the skin

Question 6

Name the receptor sensitive to fine touch and vibration

Answer 6

hair follicle receptors

Question 7

Name the receptor that responds to pain and temperature (hot and cold)

Answer 7

free nerve endings

Question 8

Name the receptor that detects low-frequency vibrations (30-40 cycles/sec) and touch

Answer 8

meissner’s corpuscles

Question 9

Name the receptor that detects only touch

Answer 9

ruffini’s corpuscles

Question 10

Name the receptor that detects high-frequency vibrations (250-300 cycles/sec) and touch

Answer 10

pacinian corpuscles

Question 11

Name all receptors that detect touch

Answer 11

hair follicle receptors (fine touch), Meissner’s corpuscles, Ruffini’s corpuscles, Pacinian corpuscles

Question 12

Name all receptors that detect vibrations

Answer 12

meissner’s corpuscles (low-frequency), pacinian corpuscles (high-frequency)

Question 13

Name the receptors that detect proprioception (limb position and movement)

Answer 13

muscle spindles and Golgi tendon organs

Question 14

Define receptive field of a neuron

Answer 14

the area on the surface of the skin where an adequate stimulus will activate a particular receptor to fire an action potential in the neuron; any stimulus applied outside the receptor field will not generate an action potential

Question 15

Name two major ascending sensory pathways

Answer 15

the spinothalamic (anterolateral) tract; the dorsal column, medial lemniscal system

Question 16

Describe the pathway of the spinothalamic (anterolateral) tract

Answer 16

info from 1st order neuron (sensory) enters spinal cord, synapses with 2nd order neuron, crosses to contralateral side, ascends to thalamus, synapses with 3rd order neuron, travels to somatosensory cortex

Question 17

Name the types of information transmitted by the spinothalamic (anterolateral) tract

Answer 17

pain, temperature, crude touch

Question 18

Describe the pathway of the dorsal column, medial lemniscal system

Answer 18

info from 1st order neuron (sensory) enters spinal cord, travels up cord, synapses with 2nd order neuron in upper spinal cord, crosses to contralateral side, ascends to thalamus, synapses with 3rd order neuron, travels to somatosensory cortex

Question 19

Name the types of information transmitted by the dorsal column, medial lemniscal system

Answer 19

fine detailed touch, proprioception (muscle sense), vibration

Question 20

Describe where the primary somatosensory cortex is located

Answer 20

on the parietal lobe, on the postcentral gyrus behind the central sulcus

Question 21

Describe the organization of the somatosensory homunculus, medial to lateral on the cortex

Answer 21

genitals, foot, leg, back, head, arm, forearm, hand, fingers, thumb, eye, nose, face, lips, tongue, pharynx

Question 22

Name the three most sensitive parts of the body (largest areas on somatosensory homunculus)

Answer 22

the hand, tongue and lips

Question 23

List the cell types in the retina

Answer 23

rod cells, cone cells, bipolar cells, ganglion cells, horizontal cells, and amacrine cells

Question 24

List functional characteristics of rod cells

Answer 24

extremely sensitive to light, function best under low light, contain one type of photopigment, do not detect light, in region of retina outside and around the fovea

Question 25

List functional characteristics of cone cells

Answer 25

function best under bright light, ideal for detecting detail, three different types each with a different photopigment, each sensitive to one primary colour, located in region of the fovea in large concentrations

Question 26

Describe how light is tranduced by the retina into action potentials

Answer 26

light strikes retina, hyperpolarizes rod and cone cells to shut them off, inhibitory neurotransmitter stops being released, bipolar cells depolarize spontaneously and activate, may lead to action potential in ganglion cells

Question 27

List four types of eye movements

Answer 27

saccades; smooth pursuit; vestibular ocular reflex (VOR); vergences

Question 28

Describe saccades with an example

Answer 28

rapid, jerky movements of the eye, used to rapidly move the eye to the object of interest (ex. reading words on a page)

Question 29

Describe smooth pursuit with an example

Answer 29

smooth movement of the eyes made to keep a moving object of interest focused on the fovea (ex. following flight of a bird with head still)

Question 30

Describe vestibular ocular reflex (VOR) with an example

Answer 30

an eye movement made when you focus your attention on an object then move your head back and forth or shake it up and down (ex. looking at someone while agreeing or disagreeing)

Question 31

Describe vergences with an example

Answer 31

eye movements made when an object of interest is approaching or moving away from you; when moving away, eyes diverge; when moving closer, eyes converge (ex. staring at pencil moving away and toward face)

Question 32

Describe where different frequencies of sound will stimulate hair cells in the cochlea

Answer 32

high frequencies near oval window (narrow and thick, tight tension) and low frequencies at apex (top) of cochlea (wide and thin, loose tension)

Question 33

Describe how sound is transduced into action potentials

Answer 33

basilar membrane vibrates, hair cells are bent, causing ion channels to open and depolarization of cells, release of neurotransmitter, excites neurons in auditory nerve, fires action potentials

Question 34

List the major functions of the vestibular system

Answer 34

maintaining balance, equilibrium, and postural reflexes, by detecting linear and rotational motion

Question 35

Name the movement detected by the semicircular canal receptors

Answer 35

detect rotational or angular accelerations of the head (three of them, each detect movement in one plane of motion)

Question 36

Name the two movements detected by the otolith organs

Answer 36

linear acceleration/deceleration in the vertical plane (saccule) and the horizontal plane (utricle)

Question 37

Describe how angular motion of the head is transduced into action potentials

Answer 37

body accelerates, otolith crystals lag behind and seem to move in opposite direction, bends cilia of hair cells, causes increase in frequency of action potentials

Question 38

Describe how hair cells perform their function

Answer 38

at rest, release small resting level of neurotransmitter which fires action potentials; when small stereocilia bend towards large kinocilium, release more neurotransmitter = more action potentials; when stereocilia bend away from kinocilium, release less neurotransmitter = less action potentials