lecture 11

Question 1

describe afference of the PNS

Answer 1

• cutaneous receptor, free nerve ending, abdominal viscera, etc. receives sensory information from stimuli
• information is passed back to sc via rami, then spinal nerve, then dorsal root to the dorsal horn

Question 2

describe efference of the PNS

Answer 2

• information from the spinal cord (ventral horn) is passed to body via the ventral root, spinal nerve, then rami
• usually innervate skeletal muscle

Question 3

what is the difference btwn rami and root?

Answer 3

• dorsal/ventral root only carry afferent/efferent information, rami do both (more information flow)
• rami are larger

Question 4

cutaneous receptors are the _____ response to _____?

Answer 4

primary afferent response to mechanical stretch

Question 5

with cutaneous receptors, mechanical stretch energy is converted into ________ so it can be sent as a signal to the brain

Answer 5

electrical energy

Question 6

describe how the conversion of mechanical stretch to electrical energy works

Answer 6

stretch allows Na to flow into the cell, converting mechanical energy to a chemical signal

Question 7

what are the 4 sensory receptors attributes

Answer 7

• intensity
• modality
• duration
• location

Question 8

describe intensity as a receptor attribute

Answer 8

discharge of receptor increased with stimuli

Question 9

describe modality as a receptor attribute

Answer 9

percept is constant for a given receptor

doesn’t matter how the receptor is stimulated, it always sends the same signal to the brain - e.g. sound, vision

Question 10

describe duration as a receptor attribute

Answer 10

receptors may be slowly adapting (one large signal then consistent little signals) or rapidly adapting (one large signal)

Question 11

describe location as a receptor attribute

Answer 11

perception is confined to the receptor’s location

Question 12

what are the two types of cutaneous receptors?

Answer 12

nonencapsulated and encapsulated

Question 13

what are the subtypes of nonecapsulated cutaneous receptors?

Answer 13

free nerve endings, hair follicle receptors, markel’s discs

Question 14

where are free nerve endings, what is their modality, and what is their adaptation (duration)?

Answer 14

• glaborous and nonglaborous skin (dermis)
• pain, temperature, touch, pressure
• varies

Question 15

where are hair follicle receptors, what is their modality, and what is their adaptation (duration)?

Answer 15

• nonglaborous skin (dermis)
• touch
• rapid

Question 16

where are Merkel’s discs, what is their modality, and what is their adaptation (duration)?

Answer 16

• glaborous and nonglaborous skin (dermis)
• touch
• slow

Question 17

what are the subtypes of encapsulated cutaneous receptors?

Answer 17

• Meissener’s Corpuscle
• Pacinian Corpuscle
• Ruffini Ending

Question 18

where are Meissener’s Corpuscles, what is their modality, and what is their adaptation (duration)?

Answer 18

• glaborous skin (dermis)
• touch
• rapid

Question 19

where are Pacinian Corpuscles, what is their modality, and what is their adaptation (duration)?

Answer 19

• glaborous and nonglaborous skin (hypodermis)
• pressure/vibration
• very rapid (imp for vibration)

Question 20

where are Ruffini Endings, what is their modality, and what is their adaptation (duration)?

Answer 20

• glaborous and nonglaborous skin (hypodermis)
• stretch
• slow

Question 21

describe the receptive feild of Meissener’s Corpuscles (rapidly adapting)

Answer 21

small (only exists at point of contact)

Question 22

describe the receptive feild of Pacinian Corpuscles (rapidly adapting)

Answer 22

larger area than Meissener’s, but most sensitive at point of contact

Question 23

describe the receptive feild of Ruffini Endings (slowly adapting)

Answer 23

generally larger area than Merkel’s, but are similar in orientation to that of the corpuscle

Question 24

describe the receptive feild of Merkel’s discs (slowly adapting)

Answer 24

smaller than Ruffini endings (only rlly exists at point of contact)

Question 25

describe cutaneous receptive feilds in general, moving from the hand, to the arm, to the back

Answer 25

- hand: small, close together, massive density - arm: larger, farther apart, less dense - back: massive receptive fields, farther apart, way less dense

Question 26

what is a dermatome?

Answer 26

area of skin that sends signals to the brain for a given spinal nerve

Question 27

is there an overlap of sensory fields?

Answer 27

yes - btwn adjacent spinal nerves

Question 28

are there differences between dermatomes and peripheral nerves?

Answer 28

yes (don't need to know explicit differences, just know that they exist)

Question 29

what is a motor unit?

Answer 29

1 motor neuron + innervated muscle fibres

Question 30

what are the basic features of a motor unit?

Answer 30

- many motor neurons innervate each muscle - each motor neuron targets only one muscle - each muscle fibre is only innervated by one motor neuron - when a motor neuron fires, all its muscle fibres contract

Question 31

axons of terminal motor neurons synapse onto:

Answer 31

the junctional folds of the sarcolemma of the muscle fibre at motor end plate

Question 32

what is the motor neuron neurotransmitter?

Answer 32

Ach

Question 33

what are myotomes?

Answer 33

groups of muscles innervated by one spinal nerve

Question 34

what are the components of a muscle spindle?

Answer 34

has: - intrafusal muscular fiber - extrafusal muscle fibers - capsule

Question 35

describe intrafusal muscule fibers

Answer 35

associated with capsule, has afferents

Question 36

describe extrafusal muscle fibers

Answer 36

generate force

Question 37

desribe the capsule

Answer 37

connective tissue surrounding the muscle spindle

Question 38

what do alpha motor neurons innervate?

Answer 38

extrafusal muscle fibers - supply power

Question 39

what do gamma motor neurons innervate?

Answer 39

intrafusal muscle fibers

Question 40

what do gamma motor neurons contain?

Answer 40

primary afferent and secondary afferent axons

Question 41

primary afferent axons increase with muscle:

Answer 41

velocity

Question 42

secondary afferent axons increase with muscle:

Answer 42

length

Question 43

if gamma neurons fire, what happens to primary and secondary afferents?

Answer 43

they become even more responsive to stretch for extreme/small muscle movements

Question 44

what is a golgi tendon organ?

Answer 44

tree-like sensory ending enclosed in a spindle-like connective tissue capsule (axon sits btwn collagen fibers of the muscle)

Question 45

how do golgi tendon organs generate an impulse?

Answer 45

pulling on collagen fibers pinches the axon, generating an impulse

Question 46

how do golgi tendon organs discharge in terms of muscle force

Answer 46

they discharge proportional to muscle force

Question 47

describe (in simple terms) an action potential

Answer 47

- Na enters the axon in response to stimulus (initiates action potential) - K leaves the axon (terminates action potential)

Question 48

describe myelin sheath

Answer 48

- for the PNS: schwann cells - for the CNS: oligodendrocytes - insulates axon, speeds up conduction - underlying axons have no channels

Question 49

describe nodes of ranvier

Answer 49

- gap btwn myelin sheath - where membrane channels are located - action potential propogation jumps btwn nodes

Question 50

larger axons have (faster/slower) transmission?

Answer 50

faster

Question 51

unmyelinated axons have (faster/slower) transmission?

Answer 51

slower

Question 52

why are neurons unmyelinated if myelination speeds condution time?

Answer 52

because its important to have some slow neurons too

Question 53

summarize the neuron fiber types

Answer 53

- BIGGER: alpha motor neurons/msucle spindle primary endings/golgi tendon organs - BIG: gamma motor neurons/muscle secondary afferent (meissner, merkel, pacinian, etc.) - MED: sharp pain, cold, some touch - SMALL: slow pain (when damage is done just need to be aware), heat, itch, some touch -most ones we covered are myelinated except some smaller bare nerve endings for temperature and pain