SDL: Sensory receptors

Question 1

the three groups of sensory receptors

Answer 1

1. exteroreceptors a. telereceptors b. contact receptors
2. interoceptors
3. proprioceptors

Question 2

what do exteroceptors (teleceptors and contact receptors) sense?

Answer 2

signals that come from outside of the body (contact receptors: heat, cold, touch, pressure; teleceptors: sound to the ears, light to the eyes, chemicals to the nose)

Question 3

what do interoceptors sense?

Answer 3

blood vessel and viscera signals

Question 4

what do proprioceptors sense?

Answer 4

signals from somatic structures that contribute to sense of orientation and movement of the body in space

Question 5

these three sensory receptors detect tactile stimuli

Answer 5

meissner’s corpuscle, hair follicle receptor, Merkel disc receptors

Question 6

what do free nerve endings function as?

Answer 6

thermoreceptors, some also function as nociceptors that detect noxious stimuli

Question 7

what two receptors detect displacement of the skin?

Answer 7

pacinian corpuscle (deep touch), Ruffini ending (stretching of the skin)

Question 8

what happens when the pacinian corpuscle is stimulated?

Answer 8

an ion channel will open that leads to formation of a “generator potential” with graded and non-propagating potentials

Question 9

describe the generator potential

Answer 9

the potential generated depends on the intensity of the stimulus; the info does not propagate along the sensory neuron buried inside

Question 10

how is a stimulus to the pacinian corpuscle transmitted along the neuron?

Answer 10

when its strong enough, the AP is generated and propagated along the sensory neuron. during this, a mechanical signal is converted into an electric signal and transmitted

Question 11

how does an AP tell the brain what is actually happening on the skin?

Answer 11

neuronal coding created by a series of APs that encode intensity, velocity, and duration of the stimuli

Question 12

describe pattern theory of sensation

Answer 12

pattern created by series of APs by a single group of sensory fibers to tell the brain the nature of the stimulus

Question 13

describe the specific nerve energies theory of sensation

Answer 13

each receptor is sensitive to a particular stimulus (adequate stimuli OR specific energy)

Question 14

what is sensory adaptation?

Answer 14

sensory receptor decreases its firing frequency after being exposed to the stimulus constantly for a while

Question 15

receptors that completely adapt to the stimulus, i.e. stop firing after some time

Answer 15

phasic receptor

Question 16

receptors that continue to fire as long as the stimulus is present

Answer 16

tonic receptor

Question 17

when the brain pays less attention to a constant stimulus, regardless of the fact that the receptor is firing

Answer 17

habituation

Question 18

the area of the body from which a stimulation influences the discharge rate of that neuron

Answer 18

receptor field (small on finger tips, large on back of the torso)

Question 19

the ability to tell whether the skin is stimulated by one or two points

Answer 19

two-point discrimination (easy on finger tip, poor on the back)

Question 20

why should we care about two-point discrimination?

Answer 20

if there is a lesion somewhere in the sensory receptor to brain pathway, it will cause poor two-point discrimination

Question 21

neural syphilis can destroy..

Answer 21

the dorsal column of the spinal cord, thus making the patient show a very poor two-point discrimination

Question 22

relative size of nerve fiber types from greatest to least

Answer 22

A>B>C

Question 23

which nerve fiber type has the slowest speed?

Answer 23

dorsal root: pain, reflex responses

Question 24

pain is transmitted by which two fiber types?

Answer 24

dorsal root (C), A-delta (pain, temp, touch)

Question 25

somatosensory receptors send the info through..

Answer 25

A-beta, A-delta, and C

Question 26

relative conduction velocity of nerve fiber types from greatest to least

Answer 26

A>B>C

Question 27

what activates the nociceptors (free nerve endings)?

Answer 27

noxious mechanical, thermal, or chemical stimuli will activate the nociceptor and cause pain

Question 28

describe pricking pain: also called? fiber type? easy to localize?

Answer 28

fast pain, first pain; A-delta; yes

Question 29

describe burning pain: also called? fiber type? easy to localize?

Answer 29

slow pain, second pain; C; no.

Question 30

what does lidocaine block? what type of pain does it block?

Answer 30

Na+ channels on C (pain) fibers; burning, slow, second pain.

Question 31

subtances released during tissue damage

Answer 31

bradykinin, serotonin, histamine, K+, acids, ACh, proteolytic enzymes, prostaglandins, substance P

Question 32

what leads to hyperalgesia after tissue damage?

Answer 32

prostaglandin and substance P release, which increase the sensitivity of nerve endings that causes a sensitive or painful area during the healing process

Question 33

the characteristics of the triple vascular response

Answer 33

redness (local vasodilation), flare (vasodilation), weal (edema)

Question 34

two muscle receptors and their locations

Answer 34

1. Golgi tendon organ (in the tendon of a muscle) 2. muscle spindle (in the belly of skeletal muscle mass)

Question 35

how is the Golgi tendon organ arranged? what does it detect? what nerve fiber does it use to send info?

Answer 35

series with the muscle mass; detects tension; sends info by the I-b nerve fiber (type of A-alpha)

Question 36

regular muscle fibers that can contract and generate force

Answer 36

extrafusal muscle fibers

Question 37

what type of fibers does the muscle spindle consist of?

Answer 37

intrafusal fibers, which can be nuclear chain fibers or nuclear bag fibers

Question 38

what neurons are intrafusal fibers activated by? what neurons are extrafusal fibers activated by?

Answer 38

efferent gamma-motor neuron; alpha-motor neuron

Question 39

when the muscle spindle is activated, it sends info to the spinal cord via

Answer 39

Group Ia (A-alpha) and Group II (A-beta) fibers

Question 40

how is muscle spindle arranged? what type of stimuli does it detect?

Answer 40

parallel with extrafusal fibers; detects stretch- reports change of muscle length and rate of change of muscle length

Question 41

if muscle spindle detects stretch, what happens when the muscle contracts?

Answer 41

the alpha-motor neuron causes muscle contraction, muscle spindle becomes floppy and does not detect anything

Question 42

when the muscle is stretched, the muscle spindle is activated as well as the

Answer 42

Golgi tendon organ

Question 43

when the intrafusal muscle fibers become floppy, it can’t send its signal out; if muscle spindle becomes inactive each time a muscle contracts, how does the nervous system solve this problem?

Answer 43

alpha-gamma linkage or co-activation

Question 44

describe alpha-gamma linkage

Answer 44

the alpha-motor neuron causes muscle contraction, also gamma-motor neurons activate the intrafusal muscle fibers and cause it to contract, so muscle spindle does not become floppy and will remain sensitive to the length of the muscle mass

Question 45

T/F: a nuclear bag fiber is a type of extrafusal muscle fiber

Answer 45

false, its an intrafusal muscle fiber

Question 46

what is the role of an alpha-motor neuron?

Answer 46

activate extrafusal fibers, leads to muscle contraction

Question 47

does alpha-motor neuron cause contraction of intrafusal muscle fibers?

Answer 47

yes

Question 48

what is the idea behind alpha-gamma linkage?

Answer 48

using alpha and gamma-motor neurons to activate the intrafusal fibers and cause contraction of muscle, so that the muscle spindle doesn’t become floppy, and will remain sensitive to the length of the muscle mass

Question 49

knowing the location of an extremity without looking at it is called

Answer 49

joint position sense

Question 50

what are the determinants for having good joint position sense?

Answer 50

sensory receptors in the joints, skin, and the muscle

Question 51

the basis of knee jerk reflex and other stretch reflexes is activation of..

Answer 51

muscle spindle