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Biomechanics > 9 - The Muscle Unit > Flashcards

9 - The Muscle Unit Flashcards

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
Q

Explain the size principles of motor unit recruitment

A
  • motor unit recruitment starts from smaller MUs

- followed by progressively larger MUs as more force is required

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26
Q

What the difference between high and low firing frequency?

A

high (no relaxation) - maximal contraction

low - muscle fibres can partially relax

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27
Q

Describe the gradation of contraction

A

all MUs and high frequency = maximal force

28
Q

What is electromyography?

A

measurement of muscle activation

29
Q

What is the principle behind electromyography?

A
  • signal from brain to MU = innervation of associated muscle fibres
  • action potential in muscle fibres initiates excitation contraction coupling
30
Q

What can you measure with electromyography?

A
  • when a muscle is turned on and off
  • the magnitude of activation
  • timing of activation
31
Q

What determines the electromyography signal?

A
  • the number of motor units activated
  • motor unit action potential firing rate
  • the type of motor units activated
32
Q

What is perception?

A

processes of obtaining information about the internal and/or external environment form sensory stimulation

33
Q

What is sensation?

A

conscious feeling relating to a sensation

34
Q

What are sensory receptors?

A
  • respond to different types of stimuli

- absorb energy and convert it into neural signals

35
Q

What are exteroceptors?

A
  • near a body surface

- respond to signals coming from the environment including the five senses

36
Q

What are the interoceptors?

A

respond to signals from within the body

37
Q

What are the two types of interoceptors?

A

1 - visceroreceptors = stimulated by excessive contraction or distention

2 - proprioceptors = responds to position and movement

38
Q

How do the stimuli and receptor interact in sensory receptors?

A 
mechanical (mechanoreceptor)
visual (photoreceptor)
chemical (chemoreceptor)
heat (thermorceptor)
(nocioreceptor)
39
Q

How do sensory neurons/receptors adapt?

A
  • 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
Q

What are the proprioceptors?

A
  • located in muscles, tendons, joints

- stimulated by motion = depends of magnitude, direction and change of body movement

41
Q

What are the proprioceptors classified as?

A

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
Q

Explain the cutaneous receptors

A
  • each receptor to a difference type of stimuli

- the receptors all involve different places within the body

43
Q

What are the types of cutaneous receptors and explain them

A
  • merkel disc = edges, corners, points
  • Meissner corpuscle = skin motion
  • Ruffini ending = skin stretch
  • Pacinian corpuscle = vibration
44
Q

Describe the neck proprioceptors

A
  • maintain equilibrium of the head is due to join receptors in c1-c3
  • sensitive to the angle between body and head
45
Q

Explain the labyrinthine proprioceptors

A
  • 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
Q

What are the two types of joint proprioceptors?

A
  • paccinian corpuscles

- ruffini endings

47
Q

Describe the paccinian corpuscles

A
  • 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
Q

Describe the ruffini endings

A
  • activated by joint angle change but also recognise constant pressure
  • slow/ very little adaptation
  • deep layers of the skin
49
Q

What are the muscle proprioceptors?

A
  • muscle spindles

- Golgi tendon organs

50
Q

Describe the muscle spindles

A

lie parallel and between muscle fibres sensitive to length change

51
Q

How do muscle spindles produce movement?

A
  • 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
Q

Describe the Golgi tendon organ

A
  • located at the musclo-tendinous junction
  • sensitive to tension
  • when stretched muscle relaxes
53
Q

When sensory fibres connects to the muscle spindle and Golgi tendon organ?

A

muscle spindle = type 1a

Golgi tendon organ = type 1b

54
Q

What do the muscle spindle and Golgi tendon organs function together to do?

A

protect the muscles for excessive stretch and excessive tension

55
Q

The stretch reflex: receptor, effector agonist, effect on antagonist

A
  • receptor = muscle spindle
  • effect on agonist = (positive or negative) more force
  • effect on antagonist = (negative or inhibitory) less force
56
Q

What is the effect of muscle spindles?

A

when stimulated cause muscles to contract to generate force to resist stretch

57
Q

The tendon stretch: receptor, effector agonist, effect on antagonist

A
  • receptor = Golgi tendon organ
  • effect on agonist = (negative or inhibitory) less force
  • effector on antagonist = (positive or excitatory) more force
58
Q

What is the effect of Golgi tendon organ?

A

when stimulated cause muscle to relax and produce less force to reduce tension

59
Q

Withdraw reflex: receptor, effect and how?

A
  • reflex = pain and tactile
  • effect = withdraw leg
  • how = positive or excitatory effect on hamstring
60
Q

Cross-extensor reflex: receptor, effect and how?

A
  • receptor = pain and tactile
  • effector = weight support on contralateral limbs
  • how = positive or negative effect on quadriceps
61
Q

What is the stretch-shortening cycle?

A

if a concentric contraction is preceded by active stretching, more force is produced during the concentric phase

62
Q

Why does the stretch-shortening cycle happen?

A
  • energy storage
  • more time to develop
  • stretch reflex
  • muscle potentiation
63
Q

Energy storage: the stretch- shortening cycle

A
  • 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
Q

More time to develop: stretch shortening cycle

A

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
Q

Stretch reflex: stretch shortening cycle

A

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
Q

Muscle potentiation: stretch shortening cycle

A
  • the stretch results in more force being produced by the cross bridges

Biomechanics (11 decks)

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