CNS - Lecture 2

Question 1

What is modality of sensory input, give some examples

Answer 1

how a stimulus is sensed or perceived by our sensory organs.
eg. vision, sense of touch, hearing, movement

Question 2

explain the relationship between sensory inputs and control

Answer 2

You can only control what you sense: without knowing the state of what you are controlling, you cannot control it

Question 3

When a stimulus is processed, what determines which modality of stimulus it will respond to?

Answer 3

the structure of the sensory receptor

Question 4

different modalities are processed…

Answer 4

in different parts of the brain

Question 5

what is the adequate stimulus

Answer 5

the modality activating a given receptor

Question 6

5 types of sensory endings in human skin (acronym)

Answer 6

MMFPR
- meissner’s corpuscles
- merkel’s corpuscles
- free nerve endings
- pacinian corpuscles
- ruffini corpuscles

Question 7

meissner’s (tactile) corpuscles function

Answer 7

respond to light touch on the skin.

Question 8

what is merkel’s corpuscles?

Answer 8

receptors that respond to touch

Question 9

what do free nerve endings respond to

Answer 9

sensory receptors that respond to pain

Question 10

Pacinian (lamellated) corpuscles structure and function

Answer 10

• contains slippery layers (lamellae) that slide over each other
• respond vigorously to vibration; distribute and amplify mechanical deformation

Question 11

Ruffini corpuscles function

Answer 11

respond to skin stretch; also function as thermoreceptors

Question 12

Types of ruffini corpuscles and their responses

Answer 12

warm type: increase firing rate as temperature rises
cold type: increase firing rate as temperature falls

Question 13

describe type A sensory receptors and transmission

Answer 13

• specialized endings of afferent axons
• project directly to the spinal cord

Question 14

describe type B sensory receptors and it’s transmission

Answer 14

• comprise first-order receptor cells responding to stimuli
• synaptically activate second-order cells close by, whose axons transmit information to the nervous system

Question 15

first order cell characteristics and role

Answer 15

• generally small
• act as an intermediary between stimulus (stimulus energy) and second-order cells

Question 16

what cells release neurotransmitters

Answer 16

first-order cells

Question 17

what is the outcome of neurotransmitter release

Answer 17

activation of second-order cells

Question 18

second order cells location and role

Answer 18

• close to the first-order cells in the sensory pathway
• receive signals from the first-order cells and transmit this information to higher brain centers.

Question 19

The sensory axon resides and transmits information via

Answer 19

the dorsal root ganglion

Question 20

process of the central branch of a sensory axon

Answer 20

enters the spinal cord and synapses onto a neuron cell body to transmit information to higher centers

Question 21

where do sensory neuron axons terminate

Answer 21

enters the CNS and terminates in branches that make synaptic contact with neurons within the CNS

Question 22

somatosensory receptors function and types

Answer 22

• cover the surface of the body and signal a variety of sensory modalities
• mechanoreceptors, thermoreceptors, nociceptors, proprioceptors and vestibular receptors

Question 23

mechanoreceptors sense

Answer 23

local tissue deformation in skin and viscera

Question 24

thermoreceptors sense

Answer 24

temperature in skin and brain

Question 25

nociceptors sense

Answer 25

pain due to tissue damage

Question 26

proprioceptors sense

Answer 26

movement & force in muscles and joints

Question 27

vestibular receptors

Answer 27

respond to head acceleration and tilt

Question 28

what is the basic mechanism of information transfer in both vertebrates and invertebrates

Answer 28

sensory receptors signal stimuli with action potentials

Question 29

what nerve cell development happened in vertebrates but not invertebrates

Answer 29

development of the myelin sheath around nerve axons that increases conduction speed

Question 30

T/F muscle spindle primary endings and golgi tendon are slow compared to postganglionic fibers, nociceptors and warmth receptors

Answer 30

False - Muscle spindle primary endings and Golgi tendon are the fastest and the autonomic postganglionic fibers, nociceptors and warmth receptors are the slowest

Question 31

sensory stimulus processing intensity principle

Answer 31

as the stimulus intensity increases, the membrane potential at the initial segment of the sensory receptor’s afferent axon increases until action potentials are generated

Question 32

explain what recruitment is

Answer 32

as stimulus intensity increases, the number of sensory receptors that are activated increases

Question 33

explain what happens during stimulus-response

Answer 33

with a mechanoreceptor, membrane distortion causes tiny pores to open
Na enters the cell making the inside less negative

Question 34

what is receptor potential and what triggers it

Answer 34

• the change in voltage at the initial segment
• triggered by membrane distortion in mechanorecpetors

Question 35

explain the idea of frequency coding

Answer 35

the bigger the stimulus, the more the membrane channels in the sensory ending are distorted = more action potentials/sec (AP/s)

Question 36

explain population code

Answer 36

the bigger the stimulus, the more sensory neurons are recruited into activity = more AP/s

Question 37

explain temporal pattern code

Answer 37

the variability of firing rate (bursts vs steady firing) - may mediate certain types of sensation

Question 38

sensory stimulus processing duration principle

Answer 38

some receptors that adapt very rapidly to stimuli while others adapt very slowly to stimuli

Question 39

slowly adapting (tonic) receptors response and examples

Answer 39

• generate AP’s throughout the duration of the stimulus
• merkel’s corpuscles, free neuron endings, ruffini corpuscles

Question 40

rapidly adapting receptors response and examples

Answer 40

• response only briefly each time the stimulus changes
• pacinian corpuscles and meissner’s corpuscles