Chp 13.15-.13.20

Question 1

receptive field

Answer 1

area monitored by a singer receptor cell
the larger the receptive field, the poorer the ability to localize a stimulus
ex: receptive fields on the tongue or fingertips much smaller than on the skin of the abdomen

Question 2

4 events along SENSORY pathways

Answer 2

1. depolarization of receptor
2. action potential generation
3. propagation over labeled line
4. CNS processing

Question 3

1. depolarization of receptor

Answer 3

physical or chemical stimulus results in graded changed in membrane potential of receptor cell
transduction

Question 4

transduction

Answer 4

conversion of stimulus to a change in membrane potential

Question 5

2. action potential generation

Answer 5

if receptor cell depolarized to threshold, action potential develops in the initial segment
greater degree of depolarization=greater frequency of action potential

Question 6

3. propagation over labeled line

Answer 6

a labeled line consists of axons carrying information about one type of stimulus
CNS interprets stimulus according to the nature of the axon on which it arrives

Question 7

4. CNS processing

Answer 7

occurs at every synapse along the labeled line

line may branch repeatedly, distributing sensory information to multiple nuclei and centers in spinal cord and brain

Question 8

events long MOTOR pathways from CNS processing

Answer 8

involuntary motor pathways and voluntary motor pathways

Question 9

involuntary motor pathways

Answer 9

immediate involuntary response
respond before sensations reach cerebral cortex
ex: reflex response

Question 10

voluntary motor pathways

Answer 10

1% of arriving sensations relayed to primary sensory cortex where perception occurs
voluntary response is not immediate

Question 11

functional classes of free nerve endings

Answer 11

nociceptors, thermoreceptors, chemorecpetors, mechanoreceptors

Question 12

2 axon types of nociceptors

Answer 12

type A fibers and type C fibers

Question 13

nociceptors

Answer 13

pain receptors

free nerve endings with large receptive fields and broad sensitivity

Question 14

type A fibers

Answer 14

FAST PAIN
ex: deep cut or injection
sensations quickly reach the CNS and trigger somatic reflexes
relayed to primary sensory cortex for conscious attention
can usually localize the stimulus within a few centimeters

Question 15

type C fibers

Answer 15

SLOW PAIN
ex: burning and aching pain
cause a generalized activation of reticular formation and thalamus
individual is aware of the pain but has only a general idea of the area affected

Question 16

thermoreceptors

Answer 16

temperature
free nerve endings
located in dermis, skeletal muscles, liver, hypothalamus
cold receptors 3-4 times more numerous than warm

Question 17

chemoreceptors

Answer 17

respond to water-soluble and lipid-soluble substances that are dissolved in body fluids

Question 18

mechanoreceptors

Answer 18

sensitive to stimuli that distort their plasma membranes

membranes contain mechanically gated ion channels

Question 19

stretching, compression, twisting

Answer 19

gates open or close in response to:

Question 20

3 mechanoreceptors

Answer 20

proprioceptors, baroreceptors, tactile receptors

Question 21

proprioceptors

Answer 21

monitor position of joints and muscles
most complex
ex: muscle spindle

Question 22

baroreceptors

Answer 22

detect pressure changes in walls of blood vessels and portions of digestive, respiratory and urinary tracts

Question 23

tactile receptors

Answer 23

provide sensations of touch, pressure, and vibration

Question 24

fine touch and pressure receptors

Answer 24

give detailed information about a stimulation

Question 25

crude touch and pressure receptors

Answer 25

provide poor localization and give little information

Question 26

tonic receptors

Answer 26

ALWAYS ACTIVE
frequency of generated action potentials reflects level of stimulation
increased stimulus=increased frequency

Question 27

phasic receptors

Answer 27

NORMALLY INACTIVE

become active for a short time in response to a change in monitored conditions

Question 28

peripheral adaptation, central adaptation

Answer 28

two types of adaptation

Question 29

adaptation

Answer 29

reduction in sensitivity in the presence of a constant stimulus

Question 30

peripheral adaption

Answer 30

occurs when level of receptor activity changes

receptors responds strongly at first, then activity gradually declines

Question 31

central adaption

Answer 31

occurs along sensory pathways within the CNS
generally involves inhibition of nuclei along a sensory pathway
ex: new smell disappears after a few seconds

Question 32

free nerve endings, root hair plexuses, tactile discs, tactile corpuscles, lamellated corpuscles, ruffini corpuscles

Answer 32

6 types of tactile receptors in the skin

Question 33

free nerve endings

Answer 33

branching tips of sensory neurons
nonspecific
respond to touch, pressure, pain, temp
most common receptors in the skin

Question 34

root hair plexus

Answer 34

monitor distortions and movements of hair follicle
displacements of hair distorts sensory dendrites and produces action potentials
adapt rapidly

Question 35

tactile discs and Merkel cells

Answer 35

decect fine touch and pressure
extremely sensitive tonic receptors
very small receptive fields
each merkel cell and its nerve terminal make up a tactile disc

Question 36

merkel cells

Answer 36

unusually large epithelial cells in stratum basale
dendritic processes from many nerve terminals branching from single mylinated afferent fiber make close contact with Merkel cells

Question 37

tactile corpuscles or Meissner’s corpuscles

Answer 37

provide sensations of fine touch, pressure, low-frequency vibration
adapt to stimulation within a second
fairly large 100um
most abundant in eyelids, lips, fingertips, nipples
highly coiled and interwoven dendrite

Question 38

lamellated corpuscles or pacinian corpuscles

Answer 38

sensitive to deep pressure
fast adapting
large receptors 4mm
single dendrite wrapped in layers of collagen fibers separated by intersitial fluid
found in fingers, mammary glands, superficial and deep fasciae and join capsules, viscera

Question 39

ruffini corpuscles

Answer 39

sensitive to pressure and distortion of reticular dermis
ex: stretching of the skin
tonic receptors with little adaption
capsule surrounds core of collagen fibers