(1) 2MB MSK > Physiology > Flashcards

Physiology Flashcards

Taken from Rafi Ahmed (77 cards)

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1
Q

What is the largest tissue type in the human body?

A

Muscle

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2
Q

All muscle in the body is striated. True/False?

A

False
Smooth muscle isn’t striated

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3
Q

Which division of the nervous system innervates skeletal muscle?

A

Somatic

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4
Q

What are skeletal fibres organised into?

A

Motor units

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5
Q

What is a motor unit made up of?

A

Motor neuron + all the muscle fibres innervated by that single motor neuron

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6
Q

What determines the number of muscle fibres per motor unit?

A

The function of the muscle
Muscles associated with powerful movements have more muscle fibres per unit, whereas muscles associated with small/precise movement have less

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7
Q

Give examples of muscles that have few muscle fibres per motor unit.

A

External eye muscles
Muscles of facial expression
Intrinsic hand muscles

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8
Q

What is contained within a muscle fibre?

A

Myofibrils and Sarcomeres

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9
Q

Skeletal muscle contraction is brought about by myogenic/neurogenic initiation?

A

Neurogenic
Nerve stimulated before muscle

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10
Q

What is released in response to action potential generation + presence in the T-tubule of the muscle fibre

A

Calcium

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11
Q

What happens after calcium is released by the sarcoplasmic reticulum?

A

Calcium binds to troponin = conformational change in tropomyosin complex
–> exposed myosin-binding site on actin to allow crossbridge formation between actin and myosin

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12
Q

List the 4 zones of a sarcomere

A

A-band
H-zone
I-band
M-line

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13
Q

Composition of A-band?

A

Myosin + portion of actin that overlaps with myosin

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14
Q

Location of H-zone?

A

Lighter area in A-band where actin does not reach

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15
Q

Location of M-line?

A

Extends vertically down the middle of the A-band within the centre of the H-zone

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16
Q

I-band composition?

A

Remaining portion of actin which is not part of the A-band

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17
Q

What are the primary factors which determine gradation of skeletal muscle tension?

A
  1. Number of muscle fibres contracting within the muscle
  2. Tension developed by each muscle fibre
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18
Q

Define “motor unit recruitment”

A

Stimulating numerous motor units to contract = stronger contraction

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19
Q

Define tetanic contraction.

A

Sustained and forceful muscle contraction
Occurs when motor neuron sends rapid, continuous signals to muscle
Prevents the muscle fibres from fully relaxing between stimuli

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20
Q

True or False: Skeletal muscle cannot experience tetanic contractions?

A

False

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21
Q

When can maximum tetanic contraction of skeletal muscle be achieved (and why)?

A

At rest –> optimal length of muscle

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22
Q

What are the 2 main types of skeletal muscle contraction?

A

Istotonic and Isometric

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23
Q

When is isotonic skeletal muscle contraction used?

A

Movement

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24
Q

True/False: Muscle length changes in isotonic skeletal muscle contraction?

A

True
Muscle tension remains constant

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25
When is isometric skeletal muscle contraction used?
Maintaining fixed positions (Static)
26
True/False: Muscle length changes in isometric skeletal muscle contraction
False Muscle length is constant to allow tension to develop
27
Velocity of muscle length shortening INCREASES/DECREASES with increasing load?
Decreases
28
Define the stretch reflex.
Negative feedback mechanism that resists passive change to muscle length by contracting the muscle
29
How does the stretch reflex elicit contaction once a muscle is stretched?
Afferent fibres fire and synapse with alpha motor neurons which, when stimulated, contract the stretched muscle
30
What are the special sensory receptors that cause the stretch reflex?
Muscle spindles (intrafusal fibres)
31
Define extrafusal fibres.
Regular muscle fibres
32
Is the activity of the myosin ATP-ase fast or slow in type I muscle fibre? What effect does this have on resistance to fatigue?
Slow activity of myosin ATP-ase High resistance to fatigue
33
Is the speed of the myosin ATP-ase fast or slow in type II muscle fibre?
Fast activity of myosin ATP-ase
34
Define a simple synovial joint.
One pair of articular surfaces
35
Give examples of a simple synovial joint?
Glenohumeral joint (shoulder Hip Interphalangeal joints TMJ
36
Define a compound synovial joint?
A joint with more than 1 pair of articular surfaces
37
Examples of compound joints
Knee joint Elbow joint (whole complex) Wrist Ankle joint Carpometacarpal joint (thumb)
38
What is secreted by the synovial membrane in the joint capsule of synovial joints?
Synovial fluid
39
Functions of synovial fluid
Joint lubrication Reduce friction Minimise wear and tear Nutrition for chondrocytes
40
What 3 main things provide joint lubrication?
Interstitial fluid Synovium-derived hyaluronic acid Synovium-derived lubricin
41
How does rapid movement affect the properties of the synovial fluid?
Fluid becomes thinner and elasticity increases to aid movement
42
Describe inflammatory synovial fluid.
Thin, yellow translucent fluid High WBC count
43
What is ECM of hyaline cartilage made up of?
70% water 20% collagen 10% proteoglycans
44
True/False: Collagenous component of hyaline cartilage is type 2 collagen
True
45
Which cells synthesise, organise and degrade the ECM of hyaline cartilage?
Chondrocytes
46
Catabolic factors influencing hyline cartilage ECM breakdown
TNF-alpha IL-1 Stimulate proteolytic enzymes
47
Anabolic factors influencing hyaline cartilage ECM replacement?
TGF IGF Stimulate proteoglycan synthesis
48
What markers indicate cartilage degradation?
Increased serum/synovial keratin sulphate Increased type 2 collagen in synovial fluid
49
With regard to the alpha motor neuron and innervation of skeletal muscle, where is the ACh receptor concentrated?
Endplate region of muscle fibre
50
Which receptors are located at the endplate of the muscle fibre?
Nicotinic ACh receptors
51
Which subunits make up the nicotinic ACh receptor?
2x alpha1 1x beta1 1x delta 1x epsilon
52
What generates a miniature endplate potential (mepp) at muscle fibres?
One vesicle of ACh activating nACH receptors at the endplate
53
What do many successive mepps produce?
Graded epp which triggers an action potential that initiates contraction (if above a threshold)
54
Once threshold epp is achieved, which channels open to cause an action potential to be fired?
Voltage-gated sodium channels
55
What enzyme hydrolyses ACh at the endplate to terminate neuromuscular transmission?
Acetlycholinesterase
56
Define neuromyotonia.
muscle twitches stiffness cramps slow relaxation.
57
How does neuromyotonia arise?
Antibodies produced against K channels in the motor neuron Results in repeated hyperexcitation (firing)
58
Which drug may be useful in neuromyotonia and why?
Carbamezapine Blocks Na channels
59
Define Lambert-Eaton Myasthenic Syndrome
Autoimmune Disrupts nerve to muscle communication = muscle weakness Associated with small cell lung cancer
60
How does Lambert-Eaton Myasthenic Syndrome arise?
Antibodies produced against Ca channels causing reduced Ca entry Results in reduced ACh vesicle release
61
Which drugs increase the concentration of ACh in the synaptic cleft?
Anticholinesterases Pyridostigimine
62
Define Myasthenia Gravis.
Chronic autoimmune disorder that results in fluctuating muscle weakness (during activity) Can be associated with thymic tumours
63
How does Myasthenia Gravis arise?
Antibodies produced against nicotinic ACh receptors Results in reduced epp amplitude = less AP generation
64
What are the 3 types of pain?
Nociceptive Inflammatory Pathological
65
Define nociceptive pain.
Acute sensory Aeises to limit further damage
66
Define inflammatory pain.
Persistant Outlives initial injury but can heal ove time
67
Which receptors are activated in the presence of noxious stimuli?
Nociceptors (sensory afferents)
68
True/False: Nocicptive pain requires threshold to be achieved to activate nociceptors
True
69
Define pathological pain
Abnormal nervous system function causes normal stimuli to be felt as noxious
70
What are the 2 main subtypes of nociceptors?
A-delta-fibres C-fibres
71
What is the difference between A-delta-fibres and C-fibres
A-delta-fibres mediate initial/fast pain C-fibres mediate the second/aftermath pain
72
Peptidergic polymodal nociceptors are a subset of C-fibres. What are their efferent function?
Release pro-inflammatory mediators from peripheral terminals; contribute to neurogenic inflammation
73
Peptidergic polymodal nociceptors are a subset of C-fibres. What are their afferent function?
Transmit nociceptive stimuli to the CNS via glutamate and peptides
74
Axon of primary afferents terminate centrally in the dorsal horn of the spinal cord in various laminae of Rexed. Where do A-delta-fibres and C-fibres terminate?
Laminae I, II also V for A-delta-fibres
75
Q Second order neurones ascend the spinal cord in a system comprised of which two tracts?
Spinoreticular Spinothalamic
76
What is the spinothalamic tract concerned with?
Pain perception - where it is, how bad is it
77
What is the spinoreticular tract concerned with?
Autonomic/emotional response - fear of pain, what can I do to stop it
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