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Biomechanics > 9 - The Muscle Unit > Flashcards

9 - The Muscle Unit Flashcards

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1
Q

What does the peripheral nervous system consist of?

A 
cranial nerves (12 pairs)
spinal nerves (31 pairs)
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2
Q

What does the central nervous system consist of?

A

brain, spinal cord

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3
Q

What does the autonomic nervous system consist of?

A

sympathetic

parasympathetic

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4
Q

What is a nerve?

A

a bundle of fibres within a connective tissue sheath

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5
Q

What forms the neuromuscular system?

A

the neuron and muscle fibre represent nervous and motor systems combined

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6
Q

What is the functional unit of the neuromuscular system?

A

the motor unit

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7
Q

Explain the neural organisation

A
  • motor neurons (efferent) = exit the spinal cord via the ventral root
  • sensory neurons (afferent) = enter the spinal cord via the dorsal root
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8
Q

What are the components of the motor neuron?

A

cell body, dendrites, axon, myelin sheaths, terminal branches, node of ranvier

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9
Q

Describe the cell body

A

information arrives and is processed

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10
Q

Describe the axon

A

travels to the muscle cell

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11
Q

Describe the terminal branches

A

the region where the axon branches out and connects to the muscle cell

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12
Q

Describe the dendrites

A

makes connections with other neurons

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13
Q

Describe the myelin sheaths

A

insulation points, the electrical signals jump from one myelin sheath to the next to get to the next destination quicker

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14
Q

Describe the node of Ranvier

A

the action potential jumps from one node to the next

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15
Q

Why do myelinated nerves have faster conduction velocities?

A

because the impulses can jump from one node of Ranvier to the next due to the myelin sheath

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16
Q

Explain the neuromuscular synapse

A
  • synapse transmit the impulses from the neuron to the effector cell
  • signal transmission at the neuromuscular synapse is chemical
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17
Q

What is a neuron?

A

a single nerve cell

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18
Q

What are the three types of neurons?

A

1 - motor neuron (efferent) - signals exciting the spinal cord
2 - sensory neurons (afferent) - signals coming into the spinal cord
3 - connection neuron (interneuron) - can elicit excitatory and inhibitory responses in other neurons

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19
Q

What is a muscle unit?

A

single motor neuron and all the muscle fibres it innervates

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20
Q

What is the force created by he muscle unit dependent upon?

A
  • motor unit recruitment

- motor unit firing rate

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21
Q

Example of type 1 muscle fibre?

A

soleus, erector spinae

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22
Q

Example of type 2a muscle fibre?

A

deltoid

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23
Q

What determines the motor unit type?

A

nerve fibre

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24
Q

What are the two ways to increase the force of muscle contraction?

A
  • number of MUs that are recruited

- firing rate

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25
Explain the size principles of motor unit recruitment
- motor unit recruitment starts from smaller MUs | - followed by progressively larger MUs as more force is required
26
What the difference between high and low firing frequency?
high (no relaxation) - maximal contraction | low - muscle fibres can partially relax
27
Describe the gradation of contraction
all MUs and high frequency = maximal force
28
What is electromyography?
measurement of muscle activation
29
What is the principle behind electromyography?
- signal from brain to MU = innervation of associated muscle fibres - action potential in muscle fibres initiates excitation contraction coupling
30
What can you measure with electromyography?
- when a muscle is turned on and off - the magnitude of activation - timing of activation
31
What determines the electromyography signal?
- the number of motor units activated - motor unit action potential firing rate - the type of motor units activated
32
What is perception?
processes of obtaining information about the internal and/or external environment form sensory stimulation
33
What is sensation?
conscious feeling relating to a sensation
34
What are sensory receptors?
- respond to different types of stimuli | - absorb energy and convert it into neural signals
35
What are exteroceptors?
- near a body surface | - respond to signals coming from the environment including the five senses
36
What are the interoceptors?
respond to signals from within the body
37
What are the two types of interoceptors?
1 - visceroreceptors = stimulated by excessive contraction or distention 2 - proprioceptors = responds to position and movement
38
How do the stimuli and receptor interact in sensory receptors?
``` mechanical (mechanoreceptor) visual (photoreceptor) chemical (chemoreceptor) heat (thermorceptor) (nocioreceptor) ```
39
How do sensory neurons/receptors adapt?
- stronger stimulus = high firing rate in affect axon - response decrease over time if stimulus stays constant - slowing adapting = decline is slow - fast adapting = decline is fast
40
What are the proprioceptors?
- located in muscles, tendons, joints | - stimulated by motion = depends of magnitude, direction and change of body movement
41
What are the proprioceptors classified as?
1 - muscle proprioceptors = muscle spindle and Golgi tendon organ 2 - joint and skin proprioceptors = ruffini endings and paccinian corpuscles 3 - labyrinthe and neck proprioceptors
42
Explain the cutaneous receptors
- each receptor to a difference type of stimuli | - the receptors all involve different places within the body
43
What are the types of cutaneous receptors and explain them
- merkel disc = edges, corners, points - Meissner corpuscle = skin motion - Ruffini ending = skin stretch - Pacinian corpuscle = vibration
44
Describe the neck proprioceptors
- maintain equilibrium of the head is due to join receptors in c1-c3 - sensitive to the angle between body and head
45
Explain the labyrinthine proprioceptors
- labyrinthine recognise orientation and the movements in the head - consists of cochlea, 3 semicircular canals, utricle and saccule - 3 semicircular cancals at 90 degrees to each other
46
What are the two types of joint proprioceptors?
- paccinian corpuscles | - ruffini endings
47
Describe the paccinian corpuscles
- located around joint capsules, ligaments and tendon sheaths - activated by rapid joint angle changes and by changes in intra-articular pressure - phasic and rapid adapting
48
Describe the ruffini endings
- activated by joint angle change but also recognise constant pressure - slow/ very little adaptation - deep layers of the skin
49
What are the muscle proprioceptors?
- muscle spindles | - Golgi tendon organs
50
Describe the muscle spindles
lie parallel and between muscle fibres sensitive to length change
51
How do muscle spindles produce movement?
- when stretched they trigger on impulse in sensory neuron to CNS - this activates the motor neuron of that muscle via a reflex action to increase force production - stimulate muscle to produce more force to resist stretching
52
Describe the Golgi tendon organ
- located at the musclo-tendinous junction - sensitive to tension - when stretched muscle relaxes
53
When sensory fibres connects to the muscle spindle and Golgi tendon organ?
muscle spindle = type 1a | Golgi tendon organ = type 1b
54
What do the muscle spindle and Golgi tendon organs function together to do?
protect the muscles for excessive stretch and excessive tension
55
The stretch reflex: receptor, effector agonist, effect on antagonist
- receptor = muscle spindle - effect on agonist = (positive or negative) more force - effect on antagonist = (negative or inhibitory) less force
56
What is the effect of muscle spindles?
when stimulated cause muscles to contract to generate force to resist stretch
57
The tendon stretch: receptor, effector agonist, effect on antagonist
- receptor = Golgi tendon organ - effect on agonist = (negative or inhibitory) less force - effector on antagonist = (positive or excitatory) more force
58
What is the effect of Golgi tendon organ?
when stimulated cause muscle to relax and produce less force to reduce tension
59
Withdraw reflex: receptor, effect and how?
- reflex = pain and tactile - effect = withdraw leg - how = positive or excitatory effect on hamstring
60
Cross-extensor reflex: receptor, effect and how?
- receptor = pain and tactile - effector = weight support on contralateral limbs - how = positive or negative effect on quadriceps
61
What is the stretch-shortening cycle?
if a concentric contraction is preceded by active stretching, more force is produced during the concentric phase
62
Why does the stretch-shortening cycle happen?
- energy storage - more time to develop - stretch reflex - muscle potentiation
63
Energy storage: the stretch- shortening cycle
- series elastic elements of the muscle stretched during the stretching period - elastic energy storage in these elements - this energy is released during concentric phase
64
More time to develop: stretch shortening cycle
the muscle is activated during the eccentric phase therefore does not have to wait for activation to build up at beginning of concentric phase
65
Stretch reflex: stretch shortening cycle
when a muscle is stretched muscle spindles feedback to the CNS and the motor neuron stimulation is increased resulting in an increase in force in the muscle to resist the stretch
66
Muscle potentiation: stretch shortening cycle
- the stretch results in more force being produced by the cross bridges

Biomechanics (11 decks)

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