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biomechanics (my own) > Functional neuro-muscular units > Flashcards

Functional neuro-muscular units Flashcards

1
Q

Skeletal Muscle

A
  • Surrounded by Epimysium

- Contains Muscle fascicles

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2
Q

Muscle Fasicles

A
  • Surrounded by Perimysium

- Contains Muscle fibers

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3
Q

Muscle Fiber

A
  • Surrounded by Endomysium

- Contains Myofibrils

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4
Q

Myofibril

A
  • Surrounded by Sarcoplasmic Reticulum (communication)

- Consists of Sarcomeres

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5
Q

Sarcomere

A
  • Contains Thick and Thin filament
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6
Q

Neuromuscular Junction

A
  • Site where axon and muscle fiber communicate
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7
Q

Components of neuromuscular junction

A
  • Motor neuron
  • Motor end plate
  • Synaptic cleft
  • Synaptic vesicles
  • Neurotransmitters
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8
Q

Muscle contraction

A
  • Motor nerve impulse cause release of Ach from synaptic vesicles
  • Bind to receptors on motor end plate
  • Generate mms contraction
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9
Q

Muscle relaxation

A
  • Acetylcholinesterase breaks down Ach
  • Motor neuron impulses stop
  • Ca++ moves back in SR
  • Myosin and actin binding prevented
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10
Q

components of a motor unit

A
  1. A single motor neuron and all the muscle fibers it controls
  2. The functional connection b/t the nervous system and the muscular system
  3. All muscle fibers contract together
  4. One neuron may innervate several mms fibers
  5. One muscle fiber may be innervated by several motor neurons
  6. Large and small motor neurons
    a. Fine control - extraocular mms (20 fibers)
    b. Strength control - gastronemius (1000 fibers)
  7. One mms fiber may act with several motor units depending on demand
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11
Q

muscles twitch

A

a single brief stimulus to a muscle; produces quick cycle of contraction and relaxation; less than 1/10 s

a. Not strong enough to do useful work
b. Normal activities require more than a single fiber twitch; sustained mms contraction

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12
Q

phases of twitch

A

i. Latent
ii. Contraction
iii. Relaxation
d. Occurs with low frequency stimuli (10 stimuli/sec)
e. Each stimulus produces an identical twitch response

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13
Q

muscle Treppe

A

relaxation is complete before next stimulus occurs, each contraction is a little stronger than previous
Treppe= stairs
b. Moderate frequency stimuli (10-20 stimuli/sec)
c. Each subsequent contraction is stronger than previous ones until, after a few stimuli, all contractions are equal (plateau)

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14
Q

Wave summation (temporal summation)

A

if a second stimulus is applied before relaxation is complete, the second contraction is greater

a. a rapid sequence of stimuli cause the muscle twitches to fuse together
b. High frequency stimulation (20-40 stimuli/sec)
c. Each stimulus arrives before the previous twitch is over
d. As the frequency of stimulus increases, the frequency of contraction increases

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15
Q

Tetanus

A

with higher frequency of stimulus, relaxation b/t contractions is reduced

a. Incomplete - produces peak tension during rapidly alternating cycles of contraction and partial relaxation
- High frequency stimulation (20-40 stimuli/sec)
- partial relaxation
b. Complete - sustained maximal contraction at peak tension, typical of normal mms contraction
- Maximum frequency stimulation (40-50 > stimuli/sec)
- no relaxation between contractions

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16
Q

Nerve types (6)

A 
A-alpha
A-beta
A-gamma
A-delta
B
C
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17
Q

myelinated nerve types (5)

A

A-alpha–>Proprioception ,Motor–Fastest (100ms) LARGE
A-beta–>Touch, Pressure–50 ms LARGE
A-gamma–>Motor–20 ms LARGE
A-delta–>Temperature ,Pain –15ms LARGE
B–>Sympathetic ,preganglionic–slower. MEDIUM

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18
Q

unmylinated nerve

A

C–>Pain, Burning,Aching, Sympathetic Post-ganglionic

slow–smallest diameter

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19
Q

Spinal Cord Reflex Arc

A
  • Functional unit of nervous system

- Automatic response to sitmulus without conscious thought

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20
Q

Components of reflex arc:

A
  1. Sensory receptor - transmits AP stimulated by sensation (skin)
  2. Sensory neuron - transmits impulses to spinal cord (dorsal root)
  3. Interneuron - connects or switches impulses to other neurons
  4. Motor neuron - transmits motor impulses
  5. Effector organ - responds with reflex contraction of mms or gland
21
Q

Proprioceptors

A
  • Muscle spindle receptors
  • Golgi tendon organs
  • Joint kinesthetic receptors
22
Q

Proprioception

A

The sense of position and movement of one’s own limbs and body without using vision (somatosensory)

  1. Sense of body and limb position
  2. Sense of speed and direction of limb joint movement
  3. Sense of muscle length and tension
23
Q

Mechanoreceptors:

A
  1. Muscle spindle receptors
  2. Intrafusal mms fibers
  3. Nuclear bag fibers
  4. Nuclear chain fibers
24
Q

Muscle spindle receptors -

A

located within the fleshy part of the muscle

25
Q

Intrafusal mms fibers

A
  • modified mms fibers enclosed in a capsule within extrafusal mms fibers (voluntary skeletal mms)
26
Q

Nuclear bag fibers -

A

a. Nuclei are concentrated in the center of the fiber
b. The ends of the fibers are striated and contractile
c. The contractile fibers are attached to the extrafusal fibers
receive input from GAMMA motor neurons
e. The nuclear bag is sensitive to SUDDEN rate change in muscle length (PHASIC)

27
Q

Nuclear chain fibers -

A

a. Nuclei are spread in a chain-like fashion in the center of the fiber
b. The ends of the fibers are striated and contractile
c. The contractile fibers are attached to the ends of the nuclear bag muscle fibers
d. Sensitive to STEADY changes of the length of the muscle (TONIC)

28
Q

Primary endings type Ia fiber:

A

a. Annulospiral sensory endings
b. larger diameter
c. conduct impuses faster (100ms)
d. respond to rate of change in the muscle fiber length

29
Q

Secondary endings type II fiber

A

a. Flower spray sensory endings
b. smaller diameter
c. conduct impulses slowly
d. respond to overall length of the muscle fiber

30
Q

Responses to stretching can be either:

A
  1. Monosynaptic - makes a rapid adjustment to prevent a fall
  2. Stretch response - controlled by cerebellum - regulates muscle tone;
  3. Gamma motor neurons let the brain preset the sensitivity of spindle to stretch
  4. When the brain signals gamma motor neurons to fire, the intrafusal mms fibers contract and become tense so that very little stretch is needed to stimulate the sensory endings
  5. Making the spindles highly sensitive to stretch is advantageous because balance reflexes have little margin for error
31
Q

Golgi tendon organs

A
  1. Encapsulated nerve endings located at the junction of tendon and mms
  2. numerous terminal branches associated with bundles of collagen fibers in the tendon
32
Q

golgi tendon organs detect:

A
  1. Force of mms contraction
  2. Tension applied to the tendon
  3. Prevents contracting mms from applying excessive tension to tendons
  4. Produces sudden relaxation of the mms
  5. Plays a role in mms tone imbalance, muscle spasm and tender joints
33
Q

golgi tendon organ FUNCTIONS

A
  1. Tendons stretch as the mms contracts causing increased tension at the tendon
  2. Increased tension stimulates 1b snesory neurons from the Golgi tendon organs
  3. Golgi tendon organs are sensitive only to intense stretch
  4. Sensory neurons enter the spinal cord and synapse with inhibitory interneurons
  5. Interneurons synapse with alpha motor neurons
  6. Inhibitory neurotransmitters are released
  7. Inhibits the alpha motor neurons which innervate extrafusal mms to which the Golgi tendon organ is attached
  8. Mms relaxes and reduces tension applied to the tendons
  9. Protects tendon and muscle from damage
    * **respond to slow stretch by resetting a mms’s length and inhibiting its synergistic stabilizers while facilitating it antagonist
34
Q

Dynamic Response

A

sudden increase in muscle tension causes a decrease in mms tone via involuntary muscular relaxation

35
Q

Static Response

A

A sustained or gradual increase in mms tension causes a decrease in mms tone

36
Q

muscle spindle vs golgi tendon organ LOCATION

A

S:Located within muscle belly (intrafusal)

G;Located within the tendon (extrafusal)

37
Q

muscle spindle vs golgi tendon organ INNERVATION

A

S:Sensory and motor innervation
G:Sensory innervation only

38
Q

muscle spindle vs golgi tendon organ NUCLEAR BAG FIBERS

A

S:Nuclear bag fibers - primary afferent only, fast stretch, dynamic
G:Detects tendon tension and rate of change

39
Q

muscle spindle vs golgi tendon organ CHAIN FIBERS

A

S: primary and secondary afferents, slow stretch, static G:Dynamic response - quick stretch

40
Q

muscle spindle vs golgi tendon organ PURPOSE

A

S:Detect muscle length and rate of change. Involuntary muscular contraction
G: Involuntary muscular relaxation

41
Q

Joint kinesthetic receptors -

A
  1. Located in and around synovial joint capsules
  2. Encapsulated and free nerve endings
  3. Stretch receptors
42
Q

TYPES of Joint kinesthetic receptors: Pacinian corpuscles

A

i. Located in CT and synovial joint capsules (Fibrous capsule, adipose tissue, ligaments, knee menisci, annulus fibrosis cervical discs)
ii. Respond to rapid pressure change
iii. Respond to stretch
iv. Respond to acceleration and deceleration of joint movement

43
Q

TYPES of Joint kinesthetic receptors: Ruffini corpuscules -

A

i. Located in synovial capsules and ligaments
ii. Respond to deep rapid and sustained pressure
iii. Especially responsive to lateral stretch
iv. Detects changes in joint angles
v. Ligament receptors adjusts muscle tone

44
Q

TYPES of Joint kinesthetic receptors: Free nerve endings

A

i. Located in most body tissues, joint capsules, ligaments, tendons, fat pads, minisci and periosteum
ii. Respond to rapid and sustained pressure

45
Q

steps of Quick Stretch Reflex

A

1) muscle stretched, 2) mms spindle afferent to spinal cord, 3) monosynaptic, 4) alpha motor neuron stimulates agonist

46
Q

Reciprocal Inhibition

A
  1. Reflex response from muscle spindles

2. Inhibits the muscle opposite the contracted mms

47
Q

Autogenic Inhibition

A
  1. Reflex response from Golgi Tendon Organs

2. An inhibitory response to a mms that develops too much tension either via shortening or lengthening

48
Q

Clinical Application of quick stretch, reciprocal i., atuogenic i. :

A

i. Post-isometric Relaxation
ii. Muscle Energy technique
iii. Strain-Counterstrain

biomechanics (my own) (6 decks)

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