Exam 1 Lecture 2 Pathophysiology of Tone part 1: proprioceptors and reflexes Flashcards Preview

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Flashcards in Exam 1 Lecture 2 Pathophysiology of Tone part 1: proprioceptors and reflexes Deck (80)
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1

Types of Muscle Spindles (3)

Located in parallel with muscle fibers

  1. Nuclear Chain Fiber
    • Aligned in single row in center of fiber
    • Signal static length of muscle
    • Signal rate of change of muscle length
  2. Static Nuclear Bag Fiber
    • Aligned in bundle in center of fiber
    • Signal static length of muscle
    • Signal rate of change of muscle length
  3. Dynamic Nuclear Bag Fiber
    • Aligned in bundle in center of fiber
    • Signal rate of change of muscle length

2

Where are muscle spindles located?

•Located in parallel with muscle fibers

3

Nuclear Chain Fibers

 

  • Aligned in single row in center of fiber
  • Signal static length of muscle (II group sensory fibers)
  • Signal rate of change of muscle length (Ia group sensory fibers)

4

Static nuclear Bag fiber

  • Aligned in bundle in center of fiber
  • Signal static length of muscle (II group fibers)
  • Signal rate of change of muscle length (Ia group fibers)

5

Dynamic Nuclear Bag Fiber

 

  • Aligned in bundle in center of fiber
  • Signal rate of change of muscle length (Ia group fibers)
     

6

Group Ia afferents - sensory fibers

  • Innervates
    • all 3 types (of muscle spindle)
  • Provides information about
    • length and velocity
       

7


•Group II afferents- sensory fibers
 

 

 

  • Innervates
    • nuclear chain fibers
    • static nuclear bag fibers
  • Provides information
    • about length only
       

8

What are muscle spindles?

 

Muscle spindles are sensory receptors within the belly of a muscle that primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motoneurons via the stretch reflex to resist muscle stretch.

 

http://en.wikipedia.org/wiki/Muscle_spindle

9

Where are muscle spindles found?

within the belly of a muscle

10

What do muscle spindles do?

  • they primarily detect changes in the length of this muscle.
  • They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts.
  • the responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motoneurons via the stretch reflex to resist muscle stretch.

11

Extrafusal muscle fibers vs intrafusal muscle fibers

 

Extrafusal muscle fibers are standard skeletal muscle fibers that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement. (they are just the regular muscle fibers we refer two when talking about skeletal muscles). Shappy: "outside the bags and chains"

http://en.wikipedia.org/wiki/Extrafusal_muscle_fiber

Intrafusal muscle fibers are skeletal muscle fibers that serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle.[1] They constitute the muscle spindle and are innervated by two axons, one sensory and one motor. Intrafusal muscle fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal"

http://en.wikipedia.org/wiki/Intrafusal_muscle_fiber

 

12

Three types of intrafusal muscle fibers (muscle spindles):

 

  1. nuclear chain fibers
  2. static nuclear bag fibers
  3. dynamic nuclear bag fibers


 

13

Intrafusal fibers: contractile and non-contractile parts

 

Ends are contractilie

  • Innervated by gamma motorneurons (sometimes 1-2 beta motorneurons)
    • activate to keep tension in the spindle as the extrafusla fibers contract and so that the middle sensory part of the intrafusal fibers can stay taut and detect change in length

Middle is non-contractile

  • Innervated by sensory nerve fibers
    • provide the sensory component of the interfusal fibers
    • Nuclear chain and Static Bag fibers are innervated by Ia & II afferent neurons
      • detect rate of change in length of muscle
      • detect static length of muscle
    • Dynamic Bag fibers are inervated by Ia afferent neurons
      • detect rate of change in length of muscle

14

Motor portion of all muscle spindles (interfusal fibers) are innervated by:

 

Gamma motor neurons (NOT alpha)

maybe 1-2 beta motor neurons

15

Muscle spindles innervated by group aI afferent (Sensory) neurons

 

All of them

  1. Static Chain Fiber
  2. Statiic Nuclear Bag Fiber
  3. Dynamic Nuclear Bag Fiber

16

  1. Muscle spindles innervated by group II afferent (sensory) fibers:

 

Static Chain Fiber
Statiic Nuclear Bag Fiber
 

17

What is a type Ia sensory fiber?

 

A type Ia sensory fiber, or a primary afferent fiber is a type of sensory fiber.[1] It is a component of a muscle fiber's muscle spindle, which constantly monitors how fast a muscle stretch changes.

(In other words, it monitors the velocity of the stretch).

18

What does a type II sensory fiber respond to?

 

provide position sense of a still muscle, fire when muscle is static [2]

19

Where do you find a type Ib sensory neuron?

 

In Golgi Tendon Organ

20

What is a type II sensory fiber?

Type II sensory fiber (group Aβ) is a type of sensory fiber, the second of the two main groups of stretch receptors. They are non-adapting, meaning that even when there is no change in muscle length, they keep responding to stimuli. In the body, Type II fibers are the second most highly myelinated fibers.

Innervate

  • nuclear chain fibers
  • Static nuclear bag fibers

(but NOT dynamic nuclear bag fibers)

21

Golgi Tendon Organ

  • –Located in series with muscle fibers in musculotendonis junctions
  • –Provides information about load and force
  • –Innervated by Group Ib fibers- sensory
  • Causes Spinal reflex known as AUTOGENIC INHIBITION REFLEX
    • First thought of as a protective mechanism
      • When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
        •  causes muscle to relax to avoid tearing
      • Now it is thought that GTOs are much more active than previously suspected. Instead of activating only when muscle completely overloads, it is now thought to activate when GTO detects certain parts of the muscle have more tension. The GTO causes that part of the muscle to relax more so that the strain is distributed to other parts of the muscle.
  • –http://neuroscience.uth.tmc.edu/s3/chapter02.html
     

22

Autonomic Inhibition Reflex

 

AUTOGENIC INHIBITION REFLEX

  • First thought of as a protective mechanism of the GTO
    • When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
      •  causes muscle to relax to avoid tearing
    • Now it is thought that GTOs are much more active than previously suspected. Instead of activating only when muscle completely overloads, it is now thought to activate when GTO detects certain parts of the muscle have more tension. The GTO causes that part of the muscle to relax more so that the strain is distributed to other parts of the muscle.

23

Gamma Motor Neurons

 


–Innervate intrafusal fibers
–Mildly contractible
–Controls sensitivity of muscle spindle; keeps spindle taut
–Contracts the ends of the bag and chain fibers and stretches the center of the muscle spindle to adjust the level of tension
 

24

Alpha Motor Neurons

 

  • Innervate extrafusal fibers (just regular fibers of the skeletal muscles)
  • Highly contractible
  • Respond to muscle contraction and force
     

25

Muscle spindle: response to muscle stretch

 


–Afferent endings vigorously increase firing rate to muscle stretch in proportion to rate & amount of stretch


 

26

What is a Reflex


•subconscious, programmed unit of behavior in which a certain type of stimulus from a receptor automatically leads to the response of an effector
 

27

Reflex Arc

 


–Neural pathway between the simulation point and a responding organ (muscle or gland)
–Path followed by a nerve impulse to produce a reflex action
 

28

Five elements of a basic reflex

 

 

  1. –Sensory receptor
  2. –Afferent fiber
  3. –Reflex center
  4. –Efferent fiber
  5. –Efferent organ
     

29

draw a simple reflex

30

True or false: reflexes need brain input to operate

false


•Reflexes can operate without brain input