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Human Physiology 2 - Unit 2 - Zach H. > Physiology Review > Flashcards

Flashcards in Physiology Review Deck (175)
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1

What are cells in the motor cortex organized into?

vertical columns

2

What does each vertical column of cell in the motor cortex stimulate?

A group of synergistic muscles or even a single muscle.

3

What is each vertical column of cells in the motor cortex divided into?

6 distinct layers

4

In the motor cortex, which layer is pyramidal cells in?

5th layer

5

What layers does input signals enter in the motor cortex?

layers 2-4

6

What do neurons arising in the 6th layer of the motor cortex communicate with?

With other regions of the cerebral cortex.

7

What are the groups of neurons in the spinal cord?

> sensory (afferent)
> anterior motor neurons (efferents)
> interneurons

8

What type of fibers do alpha motor neurons give rise to?

A alpha fibers

9

What are interneurons responsible for most of in the spinal cord?

spinal cord integrative function

10

What are the characteristics of interneurons?

> 30X as numerous as anterior motor neurons
> small and highly excitable
> capable of spontaneous activity
> responsible for most of spinal cord integrative function

11

Where are Renshaw cells located?

anterior horns of spinal cord

12

What are Renshaw cells?

inhibitory interneurons in the anterior horns of the spinal cord

13

What do Renshaw cells do?

Transmit inhibitory signals to surrounding motor neurons.
- results in lateral inhibition
- enhance fluidity of limb movement

Transmit inhibitory signals to same motor neuron.
- results in recurrent inhibition

14

Where do Renshaw cells receive collateral branches from?

alpha motor neurons

15

What type of cell innervates muscle spindles?

small gamma motor neurons (group II afferents)

16

What are the two types of intrafusal fibers that make up muscle spindles?

> Nuclear bag fibers
> Nuclear chain fibers

17

What do nuclear bag fibers detect in the muscle spindle?

Rate of change (dynamic change) in muscle length.

18

What do nuclear chain fibers detect in the muscle spindle?

Static change in muscle length.

19

What are nuclear bag fibers innervated by?

group Ia afferents and dynamic gamma efferents

20

What are nuclear chain fibers innervated by?

group II afferent and static gamma efferents

21

Which are more numerous, nuclear chains fibers or nuclear bag fibers?

nuclear chain fibers more numerous

22

How are nuclei arranged in nuclear bag fibers?

multiple nuclei located in a central "bag-like" configuration

23

How are nuclei arranged in nuclear chain fibers?

multiple nuclei arranged in a single row

24

In muscle spindles, what transmits dynamic stretch reflex signals?

signals transmitted from primary nerve endings

25

What action of the muscle elicits a dynamic stretch reflex?

elicited by rapid stretch or unstretch

26

What is the purpose of the dynamic stretch reflex?

opposes sudden changes to muscle length

27

What is the purpose of the static reflex?

causes degree of muscle contraction to remain relatively constant

28

In muscle spindles, what transmits static reflex signals?

signals transmitted by both primary and secondary endings

29

You know muscle spindles have both a dynamic stretch reflex and a static reflex, but what is the main function of these two components combined?

prevents jerkiness of body movements (damping)

30

What does muscle stretch lead to?

direct increase in firing rate of type Ia afferent fibers

> group Ia afferents synapse directly on alpha-motor neurons of the same muscle
> muscle contracts and decreases tension on muscle spindle
> synergistic muscles are activated and antagonistic muscles are inhibited