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NUT1005 > Neuromuscular Physiology > Flashcards

Neuromuscular Physiology Flashcards

1
Q

What are dendrites

A

Tree-like structures that receive information from other neurons

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2
Q

What is the soma

A

Cell body of neurone that contains the nucleus and structures which support chemical processing of the neuron e.g. neurotransmitter production

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3
Q

What is the axon

A

The nerve fibre that carries nerve impulses away from the cell body to other tissues

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4
Q

What is the myelin sheath

A

Insulates axons and enhances transmission speed along axons

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5
Q

What is the myelin sheath

A

Insulates axons and enhances transmission speed along axons

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6
Q

What is the resting membrane potential

A

-70mV

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7
Q

What is meant by the membrane is polarised

A

More negative charge on the inside compared to extracellular fluid

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8
Q

What maintains the resting membrane potential

A

Na+K+ pump

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9
Q

What has the greatest effect of the resting membrane

A

The movement of K+ through potassium leak channels (membrane is more permeable to potassium) as k+ wants to move down it’s concentration gradient but also does not want to move to area where it is already more positive

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10
Q

What are ligand gated ion channels

A

Ion channels which open in response to neurotransmitters binding

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11
Q

What are voltage gated ion channels

A

Ion channels which open in response to a change in membrane potential

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12
Q

What are mechanically gated ion channels

A

Ion channels that open in response to mechanical stimulation

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13
Q

What is an action potential

A

A rapid sequence of changes in voltage across a membrane brought about by the opening and closing of various ion channels

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14
Q

What does a stimulus arriving/ binding to the post synaptic membrane receptor cause

A

Na+ voltage gated ion channels open causing an influx of Na+ into the neuron, (crossing threshold) in an all or nothing fashion

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15
Q

What happens when the cell interior becomes positively charged

A

Na+ gates close, depolarisation ends and voltage gated k+ channels open causing the k+ to leave the cell (repolarisation)

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16
Q

What is the refractory period

A

The period where some k+ channels remain open after resting potential has been reached causing hyperpolarisation and therefore no other action potential can be initiated at this time

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17
Q

How does the wave of depolarisation spread along the axon

A

Via the uncovered nodes of ranvier

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18
Q

What is the difference between an excitatory and inhibitory neurotransmitter

A

Excitatory causes influx of positive ions ( depolarisation) and inhibitory causes influx of negatively charged ions (hyperpolarisation)

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19
Q

What is the central nervous system

A

Brain and spinal cord

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20
Q

What is the peripheral nervous system

A

All nerves and sensory structures despite brain and spinal cord

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21
Q

What is the somatic nervous system

A

Voluntary control of skeletal muscle

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22
Q

What is the autonomic nervous system

A

Involuntary control of glands and smooth muscles (consists of parasympathetic and sympathetic nervous systems which are involved in fight/flight)

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23
Q

What is the motor cortex

A

Area of the brain which moving command signals are initiated

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24
Q

What is the corticospinal tract

A

Primary descending pathway controlling voluntary movement of contra lateral limb muscles

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25
Q

How is muscle contraction initiated from the motor cortex

A

Nerve signals are sent from the motor cortex down the corticospinal tract which travels down the spinal cord

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26
Q

What are the 2 components of the spinal cord

A

White matter and grey matter

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27
Q

What is white matter

A

Part of spinal cord that consists of long axons of neurons that transmit impulses

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28
Q

What is the grey matter

A

Part of spinal cord that consists of neuronal cell bodies and their dendrites

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29
Q

Describe how corticospinal tract neurons travel through the spinal cord

A

Move through the white matter before entering the grey matter where cell bodies for alpha-motonerons are located

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30
Q

What shape is the grey matter

A

H shape

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31
Q

What are the two limbs of the grey matter

A

Dorsal and ventral limbs

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32
Q

What are the three types of neurons in the spinal cord

A

Motoneurons (efferent), sensory neurons (afferent) and interneurons

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33
Q

Where are motoneurons located in the spinal cord

A

In the ventral horn

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34
Q

Where do motoneurons exit the spinal cord

A

Through the ventral roots to muscle

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35
Q

Where do sensory neurons enter the spinal cord

A

Through the dorsal horn from the peripheral

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36
Q

What are alpha motoneurons

A

Moto neurons within the spinal cord that receive and subsequently send never signals to the muscle fibres they innervate to produce voluntary movement

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37
Q

What is a motor unit

A

The motoneuron and the muscle fibres they innervate (up to 6000 muscle fibres)

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38
Q

What are the three motor unit types

A

Slow twitch (S), fast twitch fatigue resistant (FR) and fast twitch fatiguable (FF)

39
Q

What are slow twitch motor units

A

Motor units that recruit a smaller number of type 1 muscle fibres and are recruited first at low forces

40
Q

What are fast twitch fatigue resistant muscle fibres

A

Motor units that recruit a larger number of type IIa muscle fibres and are recruited second at moderate forces

41
Q

What are fast twitch fatigable motor units

A

Motor units that recruit a larger number number of type IIx muscle fibres last at high forces

42
Q

Which type of motor unit has the largest axon diameter and cell body size

A

Type FF

43
Q

Which type of motor unit has the highest excitability

A

Type S

44
Q

Which type of motor unit has the highest maximal discharge frequency

A

Type FF

45
Q

Which type of motor unit has the highest number of muscle fibres per motor unit

A

Type FF

46
Q

Which type of motor unit has the fastest axon conduction velocity

A

Type FF

47
Q

What is the effect of body temperature on conduction velocity

A

High temperature= high conduction velocity

48
Q

What are mechanisms of force gradation

A

Mechanisms that increase force of muscle contraction

49
Q

What are the two main mechanism of force gradation

A

Increase in motor unit recruitment (spatial summation) and increase in dishcharge frequency/rate coding (temporal summation)

50
Q

What 3 main types of afferent nerve fibres/ sensory neurones innervate muscles

A

Proprioreceptors (location, moment and tension detection), mechanoreceeptors and noiciceptors (detection of chemical alterations/chemoreceptors)

51
Q

What is muscle spindle

A

Dynamic and static stretch receptors

52
Q

What is the Golgi tendon organ

A

Tension receptor

53
Q

What are free nerve endings

A

Stretch, pressure and metabolic perturbation/disturbance receptor

54
Q

What is the myotatic reflex arc

A

Reflex pathway that induces the knee jerk reflex with reciprocal inhibition to prevent excessive stretch

55
Q

What type of afferents are muscle spindle receptors coupled with

A

Ia and II

56
Q

What type of afferent are Golgi tendon organs coupled with

A

Ib

57
Q

What type of afferents are free nerve endings coupled with

A

III and IV

58
Q

Describe the myotatic reflex arc

A

1) muscle spindles detect dynamic stretch via percussion of the tendon
2) 1a afferents that innervate muscle spindles are activated
3) In afferents synapse with homologous a-motoneuron monosynpatically activating the quadriceps motoneuron, inducing shortening of the quadriceps to prevent excessive stretch
4) 1a afferents simultaneously synapses with an inhibitory interneuron which synapses with the antagonist muscle so the hamstring relaxes (reciprocal inhibition)
6) the afferent signal is concurrently sent to the brain where it is perceived

59
Q

What three neurons make up the sensory pathway

A

1st order, second order and 3rd order neuron

60
Q

Where is the 1st order neuron located

A

Extends from periphery to the dorsal horn of spinal cord and synapses with 2order neuron

61
Q

Where is the 2nd order neuron located

A

Passes up the spinal cord to the thalamus where it synapse with the 3rd order neuron

62
Q

Where is the 3rd order neuron located

A

Passes to sensory regions of the cerebral cortex

63
Q

How does the nervous system code information

A

Through frequency of AP and number of AP

64
Q

What are the functions of skeletal muscle

A

Produce movement, maintain posture, stabilise joints, generate heat and store nutrient reserves

65
Q

Describe the gross structure of the skeletal muscle

A

Wrappings of fibrous connective tissue that can be described in terms of 4 levels of organisation

66
Q

What are the 4 layers of connective tissue in skeletal muscle

A

Epimysium, perimysium, endomysium and sarcolemma

67
Q

What is the epimysium

A

Fibrous tissue surrounding skeletal muscle that contains a layer of dense, irregular connective tissue which encases the entire muscle and protects it from, friction against other muscles

68
Q

What is the perimysium

A

Connective tissue that groups muscle fibres into bundles called fascicles (contain 10-150 muscle fibres)

69
Q

What is the endomysium

A

A layer of loose connective tissue that enseaths each individual muscle fibre

70
Q

What is the sacrolemma

A

Beneath the endomysium surrounding each muscle fibre containing plasma membrane and basement membrane. The plasma membrane conducts the electrochemical waves of depolarisation over the surface of the muscle fibre

71
Q

What forms tendons

A

The epimysium blended/joined to intramuscular tissue sheaths to form tense connective tissue

72
Q

What is the function of tendons

A

Connect both ends of the muscle to the periosteum (bones outer cover( to transmit force generated from muscle fibres to pull on the bone

73
Q

What is the muscles origin

A

The location where the tendon joins a stable skeletal part (proximal end) of the lever system

74
Q

What is the insertion

A

The point of distal attachment to the moving bone

75
Q

What are myofibrils

A

Smaller functional units within muscle fibres that lie parallel to the fibres long axis

76
Q

What are sarcomeres

A

Smaller subunits in myofibrils that lie parallel to the long axis of the myofibril

77
Q

What are the 2 contractile proteins in sarcomeres

A

Actin and myosin

78
Q

What are the z lines

A

The lines that represent the separation of successive sarcomeres

79
Q

What are M bands

A

Band that bisects the central portion of the sarcomere

80
Q

What is the H zone

A

Central portion of sarcomere that contains the protein structures that contain myosin filaments

81
Q

How are actin and myosin arranged in myofibrils

A

Hexagonal arrangement

82
Q

What is myosin

A

Filaments consisting of bundles or molecules with polypeptide tails and globular heads that enable binding to actin/pulling actin towards the M band

83
Q

What ion regulates muscle contraction and relaxation

A

Calcium

84
Q

Where is calcium secreted from in muscle fibres

A

The sarcoplasmic reticulum

85
Q

What are the two accessory proteins involved in muscle contraction

A

Tropomyosin and troponin

86
Q

What happens when calcium ions are released from the SR in response to muscle activation

A

Calcium ions bind to troponin which shifts tropomysoin away from the actin binding sites, enabling the formation of cross bridges and muscle contraction

87
Q

What are T-tubules

A

Complex tubule system perpendicular to the myofibril with the lateral end of each tubule terminating in a saclike vesicle (SR) that stores ca2+

88
Q

What is a triad

A

The repeating pattern of two vesicles and a T-tubule in each z line region

89
Q

What is the function of the T-tubule/ triad

A

T-tubule opens externally from inside the muscle cell and functions are a micro transportation net weak by spreading action potentials from the fibres outer membrane to the inner cell to stimulate ca2+ release

90
Q

Where does acetylcholine bind to in muscle cells when released from a motoneuron

A

Sarcolemma

91
Q

What does binding of acetylcholine to the sarcolemma initiate

A

An influx of Na+ which spreads into the T-tubules are causes the release of ca2+ from the SR

92
Q

Why is ATP required for muscle contraction

A

Bound to the myosin head and hydrolysed to form the cross bridge, for cross bridge reattachment and recycling of the head

93
Q

What is crossbridge cycling

A

The hydrolysis of ATP when the crossbridge forms causes the release of Pi from the myosin head to form a stronger bond between actin and myosin and the release of ADP which induces the power stroke
After contraction ATP rebinds to the myosin and the crossbridge reattaches, ATP is hydrolysed again to recock the head

94
Q

What is the sliding filament theory

A

Muscle shortens and lengthens because of thick myosin and thin actin filaments that slide past each other without changing length using energy from ATP

NUT1005 (18 decks)

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