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MSK > Physiology > Flashcards

Physiology Flashcards

1
Q

What is Rheumatology

A

Concerns the diagnosis and treatment of diseases of joints and soft tissues
Primarily inflammatory conditions

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2
Q

What is orthopaedics

A

Surgical discipline concerned specifically with musculoskeletal system
Includes elective and emergency surgery

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3
Q

What are the physiological functions of skeletal muscles

A 
Maintain posture 
Purposeful movement 
Respiratory movement 
Heat production 
Contribute to whole body metabolism
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4
Q

What are the 3 types of muscles

A

Skeletal
Cardiac
Smooth

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5
Q

What is achieved through muscle contraction

A

Developing tension

Producing movement

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6
Q

What causes striation of muscle tissue

A

Alternating bands of myocin thick filaments (dark) and actin thin filaments (light)

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7
Q

What branch of the nervous system innervates cardiac and smooth muscle

A

Autonomic nervous system

Involuntary

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8
Q

Do skeletal muscles have gap junctions

A

NO

This is a feature of cardiac muscle

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9
Q

Which type of muscles have neuromuscular junctions present

A

Skeletal

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10
Q

What is a neuromuscular junction

A

where the somatic nerve connects to the muscle to cause it to contract

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11
Q

Where does the calcium come from in skeletal muscle contraction

A

Entirely from the sarcoplasmic reticulum

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12
Q

What is the transmitter at neuromuscular junctions?

A

Acetylcholine

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13
Q

Why are neurotransmitters required at the neuromuscular junction

A

There is no continuity of cytoplasm between nerve and skeletal muscle cells

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14
Q

A single motor unit can supply more than one muscle fibre - true or false

A

TRUE

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15
Q

Which muscles have high numbers of fibres per unit

A

Muscles where power is important

E.g. thighs

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16
Q

What is the functional unit of skeletal muscle

A

Sarcomere

Made up of actin and myosin

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17
Q

How do skeletal muscles attach to bones

A

Via tendons

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18
Q

How far does a single muscle fibre usually extend

A

the entire length of muscle

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19
Q

What are myofibrils

A

Specialised contractile intracellular structures

Made up of actin and myosin organised into sarcomeres

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20
Q

What is the Z line

A

Where two sarcomeres meet

Connects the thin filaments of 2 adjoining sarcomeres

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21
Q

What is a functional unit

A

the smallest component capable of performing all the functions of that organ

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22
Q

What is required for muscle contraction

A

ATP - energises the myosin head

Calcium - switches on cross bridge formation

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23
Q

Is it ATP or calcium that is required for muscle relaxation

A

ATP

needed to break down the crossbridges and pump Ca back into SR

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24
Q

What is excitation contraction coupling

A

the process whereby the surface action potential results in activation of the contractile structures of the muscle fibre

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25
Q

When is Ca released from the SR in skeletal muscles

A

When the surface action potential travels down the transverse tubules (T-tubules)

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26
Q

What are T tubules

A

Extensions of the surface membrane that dip into the muscle fibre
Bring AP much closer to SR

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27
Q

What initiates skeletal muscle contraction

A

Stimulation of alpha motor neurons

This is neurogenic initiation

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28
Q

What factors affect the tension developed by each contracting muscle fibre

A

Frequency of stimulation
Summation of contractions
Length and thickness of muscle fibre

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29
Q

What lasts longer, the action potential or the muscle twitch

A

The AP is short lived

The contraction continues for a while after

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30
Q

What type of muscle cannot be tetanised

A

Cardiac

Due to long refractory period

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31
Q

What causes tension of the muscle to increase

A

Increasing the frequency of stimulation

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32
Q

How is sustained muscle contraction produced

A

If the muscle is stimulated rapidly with no opportunity to relax between stimuli
Contraction will also be stronger

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33
Q

What happens when a skeletal muscle is stimulated once

A

A twitch is produced

Not useful for meaningful muscle activity

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34
Q

How is muscle tension transmitted to bone

A

Via the elastic components of muscle

Tendon or connective tissue

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35
Q

What are the main differences between different types of skeletal muscle fibres

A

The pathway used for ATP synthesis
The level of resistance to fatigue
The activity of myosin ATPase

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36
Q

Each motor unit contains more than one type of muscle fibre - true or false

A

False

Usually only contains one type

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37
Q

Which metabolic pathways can supply ATP in a muscle fibre

A

Transfer of phosphate from creatine phosphate to ADP
Oxidative phosphorylation - when O2 present
Glycolysis - when O2 not present

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38
Q

Describe slow oxidative type 1 fibres

A

Slow twitch fibres
Used for prolonged, low aerobic activity
Resistant to fatigue
produces lots of ATP

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39
Q

Describe fast oxidative, type IIa fibres

A

Intermediate twitch fibres
Use both aerobic and anaerobic metabolism
Useful in prolonged activity with moderate work - jogging

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40
Q

Describe fast glycolytic type IIx fibres

A

Fast twitch fibres
Uses anaerobic metabolism
Used for short-term, high intensity activity
Fatigue easily - produce less ATP

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41
Q

What is a reflex action

A

A stereotyped response to a specific stimulus

Simplest form of coordinated movement

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42
Q

Which nerve is stimulated by the knee jerk reaction

A

L3, 4

Femoral nerve

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43
Q

Which nerve is stimulated by the ankle jerk reaction

A

S1, S2

Tibial nerve

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44
Q

Which nerve is stimulated by the biceps jerk reaction

A

C5, 6

Musculocutaneous Nerve

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45
Q

Which nerve is stimulated by the brachioradialis jerk reaction

A

C5-6

Radial nerve

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46
Q

Which nerve is stimulated by the Triceps jerk reaction

A

C6-7

Radial nerve

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47
Q

What are annulospiral fibres

A

The sensory nerve ending of muscle spindles

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48
Q

Where are muscle spindles found

A

Within the belly of muscles

They run parallel to ordinary muscle fibres (

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49
Q

Describe the nerve supply to muscle spindles

A

They have their own (efferent) motor nerve supply

Called gamma neurons

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50
Q

What factors may impair skeletal muscle functions

A

Intrinsic muscle disease
Disease of NMJ
Disease of the lower neurons that supply the muscle
Disruption of input to motor neuron - e.g. MND

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51
Q

What are some general symptoms of muscle disease

A

Muscle weakness/tiredness
Delayed relaxation - myotonia
Muscle pain - myalgia
Stiffness

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52
Q

List some useful investigations in neuromuscular disease

A 
Electromyography 
Nerve conduction studies 
Muscle enzymes - CK 
Inflammatory markers - CRP, PV 
Muscle biopsy
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53
Q

What is defined as chronic pain

A

Lasting over 3 months

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54
Q

What is the definition of pain

A

An unpleasant sensory and emotional experience, associated with actual tissue damage or described in terms of such damage

55
Q

What are the 4 processes in the experience of pain

A

Transduction - stimuli turned into electrical impulse
Transmission - signal passes through nervous system
Modulation - signal is modified or hindered by system
Perception - finishes with the conscious experience of pain

56
Q

What are nociceptors

A

Sensory afferent neurons - first order

they are activated by intense noxious/harmful stimuli

57
Q

Describe the pain pathway

A

Noxious stimuli is picked up by free nerve ending of nociceptors
Pass along the nerve and synapse with second order in spinal cord send signal to brain

58
Q

Where are second order neurons found

A

They ascend the spinal cord in the anterolateral system

Terminate in the thalamus

59
Q

What is the spinothalamic tract

A

Part of second order neuron system

Involved in pain perception - location and intensity

60
Q

What is the spinoreticular tract

A

Part of second order neuron system

Involved in responses to pain, arousal, emotion etc

61
Q

What types of stimuli can be noxious

A

Mechanical
Thermal
Chemical

62
Q

What are the two types of nociceptors

A

A delta-fibres

C fibres

63
Q

What are A delta fibres

A

mechanical/thermal nociceptors so respond to those stimuli

Thinly myelinated so transmit fast

64
Q

What are C fibres

A

respond to all types of noxious stimuli

Non-myelinated so slow transmission

65
Q

What type of pain in transmitted by A delta fibres

A

Stabbing, pricking sensation

Immediate pain

66
Q

What type of pain in transmitted by C fibres

A

burning, throbbing, cramp sensations

slower

67
Q

How can you classify pain

A

Mechanism
Time course - acute/chronic
Severity
Source of origin

68
Q

What is nociceptive pain

A

Normal response to injury of tissue by damaging stimuli
Only occurs with intense stimulation
Has a protective function

69
Q

What is inflammatory pain

A

Caused by activation of the immune system
Variety of mediators can be the cause
Discourages contact and movement of the affected area
This is protective as it promotes healing

70
Q

What is neuropathic pain

A

Caused by damage to neural tissue
Pathological pain
Can present as burning, shooting, numbness etc

71
Q

What is dysfunctional pain

A

type of pathological pain
no identifiable cause
Not well understood and hard to treat

72
Q

What is referred pain

A

Pain developed in one part of the body felt in another structure
Most common in deep, visceral pain

73
Q

What causes referred pain

A

convergence of nociceptive visceral and skin afferents upon the same spinothalamic neurons at the same spinal level

74
Q

What are the 3 types of joints

A

Synovial
Fibrous
Cartilaginous

75
Q

Describe fibrous joints

A

Where bones are united by fibrous tissue
Doesn’t allow movement
E.g. skull in adults

76
Q

Describe cartilaginous joints

A

Where bones are united by cartilage
Allow limited movement
E.g. intervertebral discs

77
Q

Describe synovial joints

A

Bones that are separated by a cavity and united by a fibrous capsule
Also involves ligaments, tendons etc
Allow a wider range of movement

78
Q

What is the synovial membrane

A

the lining of the fibrous capsule in a synovial joints

Its a vascular connective tissue - with capillaries and lymphatics

79
Q

What produces synovial fluid

A

synovial cells that are found in the synovial membrane

80
Q

What covers the articular surfaces of bones

A

Cartilage

81
Q

What supports a joint

A

extra-articular structures such as ligaments, tendons and bursa

82
Q

What are the physiological functions of a joint

A

structural support

purposeful motion - help distribute stress, confer stability

83
Q

What provides joint lubrication

A

Interstitial fluid

Synovium and synovium derived lubricin

84
Q

Synovial fluid has high viscosity - true or false

A

True

Due to presence of hyaluronic acid produced by synovial cells

85
Q

Does the synovial fluid contain cells

A

Normally contains a few

Mainly mononuclear leucocytes (WBC)

86
Q

Is the synovial fluid a static pool in the joint

A

No

It is continuously replenished and absorbed by the synovial membrane

87
Q

When would the synovial fluid WBC count rise

A

In inflammatory and septic arthritis

It becomes more opaque due to increased cell count

88
Q

When would synovial fluid turn red

A

Traumatic synovial tap and in haemorrhagic arthritis

89
Q

What are the main functions of articular cartilage

A

Provides a low friction surface for joints - reduces wear and tear
Distributes pressure in the bone

90
Q

What determines the mechanical properties of cartilage

A

composition of the cartilage extracellular matrix

91
Q

What is the function of the water in the cartilage

A

Maintains resiliency of the tissye
Contributes to nutrition and lubrication
Different amounts in different areas of the joints

92
Q

What is the function of the collagen in the cartilage

A

Maintains cartilage architecture

Provides tensile stiffness and strength

93
Q

What is the function of the proteoglycan component of cartilage

A

Responsible for the compressive properties associated with load bearing
Concentration varies in different areas

94
Q

How do chondrocytes receive nutrients

A

Via the synovial fluid

The cartilage itself is avascular

95
Q

Describe the turnover of cartilage ECM

A

Chondrocytes produce enzymes that help degrade the components
Also lay down the cells
In normal joints the two processes are in balance

96
Q

What changes in the cartilage could lead to disease

A

Changes in the relative amounts of the three major components
Rate of ECM degradation exceeding the rate of synthesis

97
Q

What does repeated wear and tear of joints lead to

A

Osteoarthritis

Common in increasing age

98
Q

What causes rheumatoid arthritis

A

Synovial cell proliferation and inflammation

99
Q

What are some effects of cartilage wear and tear on the subchondral bone

A

Cyst formation
Sclerosis in the bone
Osteophyte formation

These may be seen in X-ray

100
Q

What innervates skeletal muscle

A

motor neurones

101
Q

Describe the motor neurones to skeletal muscle

A

Cell bodies are found in the brain or spinal cord
Myelinated axon for fast transmission
The axon branches into many fine branches which lose the myelin sheath as they approach the target muscle
The axon ends with a terminal bouton at the NMJ

102
Q

What neurotransmitter is used in all skeletal muscle contractions

A

Acetylcholine

103
Q

What is a motor unit

A

The neurone and the number of fibres that it innervates

104
Q

What surrounds the terminal bouton of a motor neuron

A

A cap of Schwann cells

105
Q

What are active zones at the NMJ

A

The point at which the neurotransmitter can be released

The vesicles cluster near these areas and will fuse in the zone when needed

106
Q

How is acetylcholine synthesised

A

Choline is brought into the terminal by a choline transporter
ACh is then synthesised in the cytosol from the choline and acetyl coenzyme A
It is then transported into a vesicle by vesicular ACh transporter

107
Q

Describe how ACh is stimulated to leave the vesicle

A

Action potential arrives at the terminal and triggers the opening of Ca channels
Ca flows in and binds to vesicles which allows them to fuse with the presynaptic membrane
Acetylcholine is released by exocytosis

108
Q

What is the end plate potential

A

The depolarisation generated by nicotinic ACh receptors at the post-synaptic membrane
Caused by influx of Na+ (which exceeds K+ efflux)
This movement of ions is caused by ACh binding to receptor and opening the pore in the centre

109
Q

Each vesicle contains roughly the same amount of neurotransmitter - true or false

A

True

This amount is known as a quantum

110
Q

Why are the voltage gated Na channels in the muscle fibre so important

A

Although the initial stimulation (e.p.p) is generated by the nicotinic receptor, it would not be enough on its own to trigger contraction
The additional Na+ channels allow the action potential to spread the length of the fibre and cause the contraction

111
Q

What are transverse (T) tubules and their function

A

These tubules are formed by invaginations of the muscle fibre membrane (sarcolemma)
They allow the AP to pass deep into the fibre, closer to the SR
This brings about the release of calcium that causes contraction

112
Q

Why does the duration of muscle twitch exceed that of the AP

A

There is a delay of Ca release from the SR - contraction period
And also takes extra time to reuptake the Ca - relaxation phase

113
Q

What is the function of acetylcholinesterase

A

Breaks down the ACh in the synaptic cleft so that a single epp cannot trigger a run of AP

114
Q

How can you treat Neuromyotonia

A

Anti-convulsants - carbamazepine

Block voltage gated Na+ channels

115
Q

What drugs may be used in the treatment of LEMS

A

Anticholinesterases - pyridostigmine
These decrease the breakdown of ACh so more likely to get contraction
K+ channel blockers -

116
Q

LEMS may improve on exertion

A

TRUE

Activity can help symptoms

117
Q

What drugs are used to treat Myasthenia Gravis

A

Anticholinesterases

Immunosuppressants - azathioprine

118
Q

How does the botulinum toxin work

A

Acts on motor neurone terminals to irreversible inhibit ACh release - prevents exocytosis
The effects are only overcome when the toxin is cleared and new vesicles have been synthesized – takes many weeks to recover
Death rate is high

119
Q

What are the clinical uses of botulinum toxin

A

Low doses can be given as IM injection to treat overactive muscles (twitches)
Used cosmetically as botox to reduce wrinkles

120
Q

What are curare-like compounds

A

Act as competitive antagonists of nicotinic receptors - interfere with ACh action
Reduce the amplitude of e.p.p. to below the threshold - no contraction

121
Q

How are curare-like compounds used clinically

A

Used to induce reversible muscle paralysis in certain types of surgery

122
Q

Name 2 examples of curare-like compounds

A

Vecuronium

Atracurium

123
Q

How does the angle of the legs change throughout childhood

A

All babies are bow legged
Then straightens up at 1-2 years
Angle out slightly over 2
Then back to straight or ‘normal’ alignment from 4 onwards

124
Q

What are some common ‘abnormalities’ in children that usually correct themselves

A

Overlapping toes
Internally rotated feet
Flat feet

125
Q

How do bones grow longitudinally

A

From the growth plate by enchondral ossification

This is where you start with a cartilage model that eventually becomes bone

126
Q

How does bone grow in circumference (get wider)

A

From the periosteum by appositional growth

127
Q

Which part of the bone is most vulnerable to trauma

A

Growth plates

128
Q

What factors affect the growth plate of bone

A 
Hormones 
Diet/nutrition 
Sunshine - vitamins 
Injury 
Illness
129
Q

What is meant by varum knee alignment

A

Knees bend out the way
Bow legged
Normal in under 2s

130
Q

What is meant by valgum knee alignment

A

Knees bend in the way

Knock kneed

131
Q

When is genu varum abnormal

A

If unilateral
If very severe
If it is causing pain
Causes include, skeletal dysplasia, rickets, Blount’s disease and tumours

132
Q

What is Blount’s disease

A

Rare condition where growth is stopped in the tibial physis unilaterally
Get a typical beak-like protrusion on x ray

133
Q

What pathologies can cause genu valgum

A

Tumours – enchondroma, osteochondroma
Rickets
Neurofibromatosis
Idiopathic

More likely if asymmetrical, painful or severe

MSK (21 decks)

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