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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
How is muscle contraction initiated from the motor cortex
Nerve signals are sent from the motor cortex down the corticospinal tract which travels down the spinal cord
26
What are the 2 components of the spinal cord
White matter and grey matter
27
What is white matter
Part of spinal cord that consists of long axons of neurons that transmit impulses
28
What is the grey matter
Part of spinal cord that consists of neuronal cell bodies and their dendrites
29
Describe how corticospinal tract neurons travel through the spinal cord
Move through the white matter before entering the grey matter where cell bodies for alpha-motonerons are located
30
What shape is the grey matter
H shape
31
What are the two limbs of the grey matter
Dorsal and ventral limbs
32
What are the three types of neurons in the spinal cord
Motoneurons (efferent), sensory neurons (afferent) and interneurons
33
Where are motoneurons located in the spinal cord
In the ventral horn
34
Where do motoneurons exit the spinal cord
Through the ventral roots to muscle
35
Where do sensory neurons enter the spinal cord
Through the dorsal horn from the peripheral
36
What are alpha motoneurons
Moto neurons within the spinal cord that receive and subsequently send never signals to the muscle fibres they innervate to produce voluntary movement
37
What is a motor unit
The motoneuron and the muscle fibres they innervate (up to 6000 muscle fibres)
38
What are the three motor unit types
Slow twitch (S), fast twitch fatigue resistant (FR) and fast twitch fatiguable (FF)
39
What are slow twitch motor units
Motor units that recruit a smaller number of type 1 muscle fibres and are recruited first at low forces
40
What are fast twitch fatigue resistant muscle fibres
Motor units that recruit a larger number of type IIa muscle fibres and are recruited second at moderate forces
41
What are fast twitch fatigable motor units
Motor units that recruit a larger number number of type IIx muscle fibres last at high forces
42
Which type of motor unit has the largest axon diameter and cell body size
Type FF
43
Which type of motor unit has the highest excitability
Type S
44
Which type of motor unit has the highest maximal discharge frequency
Type FF
45
Which type of motor unit has the highest number of muscle fibres per motor unit
Type FF
46
Which type of motor unit has the fastest axon conduction velocity
Type FF
47
What is the effect of body temperature on conduction velocity
High temperature= high conduction velocity
48
What are mechanisms of force gradation
Mechanisms that increase force of muscle contraction
49
What are the two main mechanism of force gradation
Increase in motor unit recruitment (spatial summation) and increase in dishcharge frequency/rate coding (temporal summation)
50
What 3 main types of afferent nerve fibres/ sensory neurones innervate muscles
Proprioreceptors (location, moment and tension detection), mechanoreceeptors and noiciceptors (detection of chemical alterations/chemoreceptors)
51
What is muscle spindle
Dynamic and static stretch receptors
52
What is the Golgi tendon organ
Tension receptor
53
What are free nerve endings
Stretch, pressure and metabolic perturbation/disturbance receptor
54
What is the myotatic reflex arc
Reflex pathway that induces the knee jerk reflex with reciprocal inhibition to prevent excessive stretch
55
What type of afferents are muscle spindle receptors coupled with
Ia and II
56
What type of afferent are Golgi tendon organs coupled with
Ib
57
What type of afferents are free nerve endings coupled with
III and IV
58
Describe the myotatic reflex arc
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
What three neurons make up the sensory pathway
1st order, second order and 3rd order neuron
60
Where is the 1st order neuron located
Extends from periphery to the dorsal horn of spinal cord and synapses with 2order neuron
61
Where is the 2nd order neuron located
Passes up the spinal cord to the thalamus where it synapse with the 3rd order neuron
62
Where is the 3rd order neuron located
Passes to sensory regions of the cerebral cortex
63
How does the nervous system code information
Through frequency of AP and number of AP
64
What are the functions of skeletal muscle
Produce movement, maintain posture, stabilise joints, generate heat and store nutrient reserves
65
Describe the gross structure of the skeletal muscle
Wrappings of fibrous connective tissue that can be described in terms of 4 levels of organisation
66
What are the 4 layers of connective tissue in skeletal muscle
Epimysium, perimysium, endomysium and sarcolemma
67
What is the epimysium
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
What is the perimysium
Connective tissue that groups muscle fibres into bundles called fascicles (contain 10-150 muscle fibres)
69
What is the endomysium
A layer of loose connective tissue that enseaths each individual muscle fibre
70
What is the sacrolemma
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
What forms tendons
The epimysium blended/joined to intramuscular tissue sheaths to form tense connective tissue
72
What is the function of tendons
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
What is the muscles origin
The location where the tendon joins a stable skeletal part (proximal end) of the lever system
74
What is the insertion
The point of distal attachment to the moving bone
75
What are myofibrils
Smaller functional units within muscle fibres that lie parallel to the fibres long axis
76
What are sarcomeres
Smaller subunits in myofibrils that lie parallel to the long axis of the myofibril
77
What are the 2 contractile proteins in sarcomeres
Actin and myosin
78
What are the z lines
The lines that represent the separation of successive sarcomeres
79
What are M bands
Band that bisects the central portion of the sarcomere
80
What is the H zone
Central portion of sarcomere that contains the protein structures that contain myosin filaments
81
How are actin and myosin arranged in myofibrils
Hexagonal arrangement
82
What is myosin
Filaments consisting of bundles or molecules with polypeptide tails and globular heads that enable binding to actin/pulling actin towards the M band
83
What ion regulates muscle contraction and relaxation
Calcium
84
Where is calcium secreted from in muscle fibres
The sarcoplasmic reticulum
85
What are the two accessory proteins involved in muscle contraction
Tropomyosin and troponin
86
What happens when calcium ions are released from the SR in response to muscle activation
Calcium ions bind to troponin which shifts tropomysoin away from the actin binding sites, enabling the formation of cross bridges and muscle contraction
87
What are T-tubules
Complex tubule system perpendicular to the myofibril with the lateral end of each tubule terminating in a saclike vesicle (SR) that stores ca2+
88
What is a triad
The repeating pattern of two vesicles and a T-tubule in each z line region
89
What is the function of the T-tubule/ triad
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
Where does acetylcholine bind to in muscle cells when released from a motoneuron
Sarcolemma
91
What does binding of acetylcholine to the sarcolemma initiate
An influx of Na+ which spreads into the T-tubules are causes the release of ca2+ from the SR
92
Why is ATP required for muscle contraction
Bound to the myosin head and hydrolysed to form the cross bridge, for cross bridge reattachment and recycling of the head
93
What is crossbridge cycling
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
What is the sliding filament theory
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 (17 decks)

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