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Physiology Flashcards

1
Q

Define pain

A

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

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2
Q

Name the four distinct processes in the physiology of pain

A
  • transduction
  • transmission
  • modulation
  • perception
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3
Q

Describe transduction

A

Translation of noxious stimulus to electrical activity at the peripheral nociceptor

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4
Q

Describe transmission

A

Propagation of pain signal as nerve impulses through the nervous system

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5
Q

Describe modulation

A

Modification / hindering of pain transmission in the nervous system eg. by inhibitory neurotransmitters like endogenous opiods

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6
Q

Describe perception

A

Conscious experience of pain. Causes physiological and behavioural responses

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7
Q

Pain begins with activation of what?

A

Nociceptors

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8
Q

What are nociceptors?

A

Specific primary sensory afferent neurons normally activated by intense noxious stimuli (eg mechanical, thermal or chemical)
- first order neurons that relay information to second order neurones in the CNS by chemical synaptic transmission

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9
Q

Name the neurotransmitters of the nociceptive pathway

A
  • glutamate

- peptides (substance P, neurokinin A)

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10
Q

Second order neurons ascend the spinal cord where?

A

In the anterolateral system (terminate in the thalamus)

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11
Q

What does the anterolateral system mainly comprise of?

A
  • the spinothalamic tract (STT); involved in pain perception (location, intensity)
  • the spinoreticular traact (SRT); involved in autonomic responses to pain, arousal, emotional responses, fear of pain
  • from the thalamus, sensory information is relayed (third order neurones) to the primary sensory cortex
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12
Q

Nociceptors are activated by what?

A
  • mechanical, thermal or chemical stimuli that are noxious
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13
Q

Transduction of nociceptors begins where and is mediated by what?

A
  • begins in free nerve endings

- mediated by numerous receptors and channels

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14
Q

What are A kappa fibres?

A

Mechanical / thermal nociceptors that are thinly myelinated (conduction velocity of 6-30ms^-1) respond to noxious mechanical and thermal stimuli
- mediate first or fast pain

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15
Q

What are C fibres?

A

Nociceptors that are unmyelinated (conduction velocity of 0.5 - 2.0 ms^-1) collectively they response to all noxious stimuli (eg they are polymodal)
- mediate second or slow pain

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16
Q

Name the ways to classify pain

A
  • mechanisms eg nociceptive, inflammatory, pathological
  • time course; eg acute, chronic, breakthrough
  • severity; eg mild, moderate or severe
  • source of origin; eg somatic or visceral
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17
Q

Describe nociceptive pain

A
  • this represents normal response to injury of tissues by noxious (damaging) stimuli
  • only provoked by intense stimulation of nociceptors by noxious stimuli (eg mechanical, chemical, thermal)
  • nociceptive pain is adaptive
  • functions as early warning physiological protective system to detect and avoid noxious stimuli
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18
Q

Describe inflammatory pain

A
  • caused by activation of the immune system by tissue injury or infection
  • pain activated by a variety of mediators released at the site of inflammation by leucocytes, vascular endothelium and tissue resident mast cells
  • causes heightened pain sensitivity to noxious stimuli (hyperalgesia) and pain sensitivity to innocuous stimuli (allodynia)
  • this discourages physical contact (with the affected part) and also discourages movement (eg of a joint)
  • inflammatory pain is adaptive, it promotes repair until healing occurs
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19
Q

Define allodynia

A

Pain sensitivity to innocuous stimuli

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20
Q

Define hyperalgesia

A

Pain sensitivity to noxious stimuli

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21
Q

Name the two types of pathological pain

A
  • neuropathic

- dysfunctional

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22
Q

Describe neuropathic pathological pain

A
  • caused by damage to neural tissue
  • examples of neuropathic pain include; compression neuropathies, peripheral neuropathies, central pain (following stroke of spinal injury), postherpetic neuralgia, trigeminal neuralgia, phantom limb
  • can be perceived as burning, shooting, numbness, pins and needles, may be less localised
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23
Q

Describe dysfunctional pathological pain

A
  • in dysfunctional pain there is no identifiable damage or inflammation
  • examples of dysfunctional pain include; fibromyalgia, IBS, tension headache, temporomandibular joint disease, interstitial cystitis
  • pathophysiology of dysfunctional pain is not fully understood
  • simple analgesics usually not very effective in pathological pain (neuropathic or dysfunctional)
  • pathological pain is sometimes treated by drugs not originally developed for pain eg antidepressants
  • pathological pain is not protective but maladaptive
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24
Q

Referred pain is caused by what?

A
  • convergence of nociceptive visceral and skin afferents upon the same spinothalamic neurons at the same spinal level
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25
Q

Name the physiological functions of skeletal muscles

A
  • maintenance of posture
  • purposeful movement in relation to external environment
  • respiratory movements
  • heat production
  • contribution to whole body metabolism
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26
Q

Name the three types of muscle in the body

A
  • skeletal
  • cardiac
  • smooth
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27
Q

How do muscles develop tension and produce movement?

A

Through contraction

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28
Q

Which muscle is striated and which is not?

A
  • skeletal and cardiac are striated

- smooth muscle is not

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29
Q

What is striation?

A
  • can be visualised under a light microscope as alternating dark bands and light bands
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30
Q

What causes the dark and light bands of striated muscle?

A
  • dark bands are caused by myosin thick filaments

- light bands are caused by actin thin filaments

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31
Q

Skeletal muscles are innervated by what?

A

The somatic nervous system and are subject to voluntary control

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32
Q

Cardiac and smooth muscles are innervated by what?

A

The autonomic nervous system - involuntary

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33
Q

Is skeletal muscle neurogenic or myogenic?

A

Neurogenic

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34
Q

The Ca++ for contraction of skeletal muscle originates from where?

A

The sarcoplasmic reticulum

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35
Q

Gradation of contraction of skeletal muscle is dependent on what?

A
  • by motor unit recruitment

- summation of contractions

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36
Q

Skeletal muscle fibres are organised into what?

A

Motor units

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37
Q

What are motor units?

A

A single alpha neuron and all the skeletal muscle fibres it innervates

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38
Q

The number of muscle fibres per motor unit depends on what?

A

The functions served by the muscle

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39
Q

What type of muscles have fewer fibres per motor unit?

A
  • muscles which serve fine movements (eg external eye muscles, muscles of facial expression; and intrinsic hand muscles)
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40
Q

Skeletal muscles are usually attached to the skeleton by what?

A

Tendons

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41
Q

Skeletal muscle consists of what?

A

Parallel muscles fibres bundled by connective tissue

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42
Q

Each muscle fibre contains what?

A

Myofibrils

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43
Q

What are myofibrils?

A
  • specialised contractile intracellular structures

- the myofibrils have alternating segments of thick and thin protein filaments

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44
Q

With each myofibril, actin and myosin are arranged into what?

A

Sarcomeres

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45
Q

What is the functional unit of muscle?

A

Sarcomeres

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46
Q

Which of the filaments are thin and which are thick?

A
  • actin are the thin filaments

- myosin are the thick filaments

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47
Q

What separates sarcomeres?

A

Z lines

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48
Q

What does the z line connect?

A

The thin filaments of 2 adjoining sarcomeres

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49
Q

How many zones does a sarcomere have?

A

4

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50
Q

Name the 4 zones of sarcomeres

A
  • A band
  • H zone
  • M line
  • I band
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51
Q

What is the A band?

A

Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

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52
Q

What is the H zone?

A

Lighter area within middle of A band where thin filaments dont reach

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53
Q

What is the M line?

A

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

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54
Q

What is the I band?

A

Consists of remaining portion of thin filaments that do not project in A band

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55
Q

Muscle tension is produced by what?

A

Sliding of actin filaments over myosin filaments

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56
Q

Force generation depends on what?

A

ATP dependent interactions between thick and thin filaments

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57
Q

What is calcium required for?

A

To switch on cross bridge formation

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58
Q

What is ATP required for?

A

Both contraction and relaxation

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59
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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60
Q

In skeletal muscle fibres. where is calcium released from?

A

The lateral sacs of the sarcoplasmic reticulum when the surface action potential spreads down the transverse tubules

61
Q

What are T tubules?

A

Extensions of the surface membrane that dip into the muscle fibre

62
Q

Spread of action potential down the t tubules triggers what?

A

The release of calcium ions from lateral sacs of sarcoplasmic reticulum

63
Q

Ca2+ is the link between what?

A

Excitation and contraction

64
Q

ATP is needed during muscle contraction to?

A

Power cross bridges

65
Q

ATP is needed during relaxation to?

A
  • release cross bridges

- to pump Ca2+ back into the sarcoplasmic reticulum

66
Q

Gradation of skeletal muscle tension depends on what two primary factors?

A
  • number of muscle fibres contracting within the muscle

- tension developed by each contracting muscle fibre

67
Q

Describe the number of muscle fibres contracting within the muscle in relation to gradation of skeletal muscle tension

A
  • motor units allow simultaneous contraction of a number of muscle fibres
  • a stronger contraction could be achieved by stimulation of more motor units; this is known as motor unit recruitment
  • asynchronous motor units recruitment during submaximal contractions helps prevent muscle fatigue
68
Q

Describe the tension developed by each contracting muscle fibre in relation to gradation of skeletal muscle tension

A
  • depends on frequency of stimulation and summation of contractions
  • length of muscle fibre at the onset of contraction
  • thickness of muscle fibre
69
Q

In skeletal muscle the duration of action potential is longer or shorter than the duration of resulting twitch?

A

Shorter

70
Q

As the duration of the action potential is much shorter than the duration of the resulting twitch, it is possible to do what?

A

To summate twitches to brings about a stronger contraction through repetitive fast stimulation of skeletal muscle

71
Q

What happens if the skeletal muscle is stimulated once?

A

A single contraction called a twitch is produced

72
Q

What happens if skeletal muscle receives a second stimulation before it has time to completely relax?

A

The second response adds to the first and a greater muscle tension is developed

73
Q

The tension developed by skeletal muscle increases with what?

A

Increasing frequency of stimulation

74
Q

Maximal tetanic contraction can be achieved when?

A

The muscle is at its optimal length before the onset of contraction

75
Q

Developed tension depends on what?

A

The initial length of skeletal muscle fibre

76
Q

The resting length of a skeletal muscle is what?

A

Approximately its optimal length

77
Q

What is isotonic contraction?

A

Used for body movements and for moving objects. Muscle tension remains constant as the muscle length changes

78
Q

What is isometric contraction?

A

Used for supporting objects in fixed positions and for maintaining body posture. Muscle tension develops at constant muscle length

79
Q

What are the two types of skeletal muscle contraction?

A

Isotonic and isometric contraction

80
Q

In both isotonic and isometric contraction, muscle tension is transmitted to the bone via what?

A

The elastic components of muscle

81
Q

The velocity of muscle shortening decreases as what increases?

A

Load

82
Q

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

A
  • the enzymatic pathways for ATP synthesis
  • the resistance to fatigue; muscle fibres with greater capacity to synthesise ATP are more resistant to fatigue and
  • the activity of myosin ATPase - this determines the speed at which energy is made available for cross bridge cycling ie. the speed of contraction
83
Q

Name some metabolic pathways that supply ATP in muscle fibres

A
  • transfer of high energy phosphate from creatine phosphate to ADP - immediate source for ATP
  • oxidative phosphorylation; main source when O2 is present
  • glycolysis; main source when O2 is not present
84
Q

How many types of skeletal muscle fibres are there?

A

3

85
Q

Name the three types of skeletal muscle fibre

A
  • slow oxidative type 1 fibres
  • fast oxidative type 2a fibres
  • fast glycolytic type 3 fibres
86
Q

Describe slow oxidative type 1 fibres

A
  • also known as slow twitch fibres

- used mainly for prolonged relatively low work aerobic activities eg maintenance of posture, walking

87
Q

Describe fast oxidative type 2a fibres

A
  • also known as intermediate twitch fibres

- use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities eg jogging

88
Q

Describe fast glycolytic type 3 fibres

A
  • also known as fast twitch fibres

- use anaerobic metabolism and are mainly used for short term high intensity activities eg jumping

89
Q

Input from a variety of sources influence the activity of motor units to produce?

A

Purposeful skeletal muscle activity

90
Q

What is a reflex action?

A

A stereotyped response to a specific stimulus

91
Q

What are the simplest form of coordinated movement?

A

Reflex actions

92
Q

Where are the pathways responsible for reflex actions located?

A

At various levels of the motor system

93
Q

What is the simplest monosynaptic spinal reflex?

A

The stretch reflex

94
Q

The stretch reflex helps to do what?

A

Helps maintain posture eg when walking

95
Q

The sensory receptor is the muscle spindle and is activated by what?

A

Muscle stretch

96
Q

Stretching the muscle spindle increases firing where?

A

In the afferent neurons

97
Q

The afferent neurons synapse where?

A

In the spinal cord with the alpha motor neurones ( efferent limb of the stretch reflex) that innervate the stretched muscle

98
Q

The stretch reflex is coordinated by what?

A

Simultaneous relaxation of antagonist muscle

99
Q

The stretch reflex can be elicited by what?

A

Tapping the muscle tendon with a rubber hammer

100
Q

Name some examples of tendon reflexes that can be elicited by rubber hammer

A
  • knee jerk
  • ankle jerk
  • biceps jerk
  • brachioradialis
  • triceps jerk
101
Q

What are the sensory receptors for stretch reflex?

A

Muscle spindles

102
Q

What are muscle spindles?

A

Collection of specialised muscle fibres

103
Q

What else are muscle spindles known as?

A

Intrafusal fibres

104
Q

Ordinary muscle fibres are referred to as what?

A

Extrafusal fibres

105
Q

Where are muscle spindles found?

A

Within the belly of muscles and run parallel to ordinary muscle fibres (extrafusal fibres)

106
Q

Muscle spindles have sensory nerve endings known as what?

A

Annulospiral fibres

107
Q

The discharge from the muscle spindle sensory endings increases or decreases as the muscle is stretched?

A

Increases

108
Q

The efferent neurons that supply muscle spindles are called what?

A

Gamma motor neurons

109
Q

What do the gamma motor neurons do?

A

Adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscle shorten during muscle contraction

110
Q

Impairment of skeletal muscle function may be caused by?

A
  • intrinsic disease of muscle
  • disease of NMJ
  • disease of lower motor neurons which supply the muscle
  • disruption of input to motor nerves (eg upper motor neuron disease)
111
Q

Name some causes of intrinsic muscle disease

A
  • genetically determined myopathies

- acquired myopathies

112
Q

Name some genetically determined myopathies

A
  • congenital myopathies; characteristic microscopic changes leading to reduced contractile ability of muscles
  • chronic degeneration of contractile elements; muscular dystrophy
  • abnormalities in muscle membrane ion channels eg myotonia
113
Q

Name some acquired myopathies

A
  • inflammatory myopathies eg polymyositis, inclusion body myositis
  • non inflammatory myopathies eg fibromyalgia
  • endocrine myopathies eg cushings syndrome, thyroid disease
  • toxic myopathies eg alcohol, stains
114
Q

Name some symptoms of muscle disease

A
  • muscle weakness / tiredness
  • delayed relaxation after voluntary contraction (myotonia)
  • muscle pain (myalgia)
  • muscle stiffness
115
Q

Name some useful investigations in neuromuscular disease

A
  • electromyography (EMG)
  • nerve conduction studies; determines the functional integrity of peripheral nerves
  • muscle enzymes eg CK
  • inflammatory markers
  • muscle biopsy
116
Q

What is electromyography?

A
  • electrodes detect the presence of muscular activity
  • records frequency and amplitude of muscle fibres action potentials
  • EMG findings not pathognomonic of specific disease - will not provide the definitive diagnosis
  • EMG helps differentiate primary muscle disease from muscle weakness caused by neurological disease
  • nerve conduction studies usually done at the same time as EMG
117
Q

Name the three types of joint

A
  • synovial
  • fibrous
  • cartilaginous
118
Q

What is a fibrous joint?

A
  • synarthrosis
  • bones united by fibrous tissue
  • doesn’t allow any movement
  • example; sutures of the skull in adults
119
Q

What is a cartilaginous joint?

A
  • amphiarthrosis
  • bones united by cartilage
  • allow limited movement
  • examples; intervertebral discs, pubic symphysis, part of the sacroiliac joints, costochondral joints
120
Q

What is a synovial joint?

A
  • disarthrosis
  • bones separated by a cavity (containing a synovial fluid) and united by a fibrous capsule (and other extra-articular structures eg ligaments, tendons and bursae)
  • the inner aspect of fibrous capsule is lined with synovial membrane
121
Q

Describe the synovial membrane

A
  • about 60 micrometres thick in the human knee
  • vascular connective tissue with capillary networks and lymphatics
  • the synovial membrane contains synovial cells (fibroblasts) which produces the synovial fluid
122
Q

The articular surfaces of bone are covered with what?

A

Cartilage

123
Q

What are the two classes of synovial joints?

A
  • simple

- compound

124
Q

What are simple and compound synovial joints?

A
  • simple; one pair of articular surfaces eg metacarpophalangeal joint
  • compound; more than one pair of articular surfaces eg elbow joint
125
Q

What are joints supported by?

A

Extra-articular structures such as brusa, ligaments and tendons

126
Q

What is the physiological functions of joints?

A

To serve the functional requirements of the MSK system

  • structural support
  • purposeful movement
127
Q

Describe the roles of joint during purposeful motion

A
  • stress distribution
  • confer stability
  • joint lubrication
128
Q

Describe conferring stability in relation to the role of joints

A
  • shape of the articular component eg the hip joint
  • ligaments provide a second major stabilising influence
  • synovial fluid acts as an adhesive seal that freely permits sliding motion between cartilaginous surfaces
129
Q

Describe joint lubrication provided in relation to the role of joints

A
  • cartilage interstitial fluid
  • synovium; derived hyaluronic acid (mucin), a polymer disaccharides
  • synovium derived lubrcin- a glycoprotein
  • mucin and glycoprotein mainly produced by synovial cells in the synovial membrane
130
Q

Describe the functions of synovial fluid

A
  • lubricates joints
  • facilitates joint movement; reduced friction
  • helps minimise wear and tear of joints through efficient lubrication
  • aids in the nutrition of articular cartilage
  • supplies the chondrocytes (cartilage cells) with O2 and nutrients and remove O2 and waste products
131
Q

Describe the general characteristics of the synovial fluid

A
  • the synovial fluid fills the joint cavity
  • the synovial fluid is continuously replenished and absorbed by the synovial membrane ie not a static poole
  • the synovial fluid has a high viscosity - mainly due to the presence of hyaluronic acid (mucin) produced by the synovial cells
  • the viscosity of the synovial fluid varies with joint movement
  • other constituents of the synovial fluid (for example uric acid) are derived by dialysis of blood plasma
  • normally, the synovial fluid contains few cells (mainly mononuclear leukocytes)
132
Q

Describe the changes in synovial fluid viscosity and elasticity during joint movement

A
  • the viscosity and elasticity of synovial fluid change during joint movement
  • rapid movement is associated with decreased viscosity and increased elasticity
  • these properties of synovial fluid become defective in a diseased joint eg in osteoarthritis
133
Q

Describe the appearance of synovial fluid

A

The normal synovial fluid is clear and colourless

- the synovial fluid turns red in traumatic synovial tap and in haemorrhagic arthritis

134
Q

What is the normal cell count of synovial fluid?

A
  • it has <200 WBC/mm3 of which polymorphs are usually <25mm3

- the synovial fluid WBC count increases in inflammatory and septic arthritis

135
Q

Describe the main functions of articular cartilage

A
  • provides a low friction lubricated gliding surface
  • this helps prevent wear and tear of joints
  • distributes contact pressure to subchondral bone
  • the composition of the cartilage ECM and the interaction between the fluid and solid phase of the cartilage plays a significant role in determining the mechanical properties of cartilage
136
Q

Name the four zones of articular cartilage

A
  • superficial zone
  • middle zone
  • deep zone
  • calcified zone
137
Q

How do the zones of articular cartilage differ?

A

Zones differ in organisation of collagen fibres and relative content of cartilage components

138
Q

Describe the articular cartilage

A
  • usually hyaline
  • is elastic and has sponge like properties
  • covers the articular surfaces of bones
  • it has special extracellular matrix made predominantly of water, collagen - mainly type 2 contributes most of the elastic behaviour of cartilage and proteoglycans
139
Q

Describe the mechanical properties of the major cartilage components

A
  • water
  • collagen
  • proteoglycan
140
Q

Describe the water of major cartilage components

A
  • accounts for 70% of the cartilage net weight
  • unevenly distributed, highest 80% near the articular surface
  • cartilage water content decreases with age
  • maintain the resiliency of the tissue and contribute to the nutrition and lubrication system
141
Q

Describe the collagen of major cartilage components

A
  • accounts for 20% of the cartilage wet weight
  • mainly type 2 collagen which decreases with age
  • maintain cartilage architecture
  • provides tensile stiffness and strength
142
Q

Describe the proteoglycan of major cartilage components

A
  • accounts for 10% of cartilage wet weight
  • highest concentration is found in the middle and deep zone
  • composed mainly of glycosaminoglycan eg. chondroitin sulphate
  • composition of cartilage proteoglycan changes with age eg chondroitin decreases with age
  • responsible for the compressive properties associated with load bearing
143
Q

Describe the extracellular matrix of articular cartilage

A
  • cartilage ECM usually constitutes >98% of the total cartilage volume
  • the ECM is synthesises, organised, degraded and maintained by chondrocytes (cartilage cells) usually constitiutes <2% of the total cartilage volume
  • the articular cartilage is avascular and the cartilage cells (chondrocytes) receives nutrients and O2 via the synovial fluid
  • in normal joints, the rate of ECM degradation doesn’t exceed the rate at which it is replaced
144
Q

Describe catabolic factors of cartilage matrix turnover

A
  • stimulate proteolytic enzymes and inhibit proteoglycan synthesis
  • tumour necrosis factors
  • interleukin
145
Q

Describe anabolic factors of cartilage matrix turnover

A
  • stimulate proteoglycan synthesis and counteract effects of IL-1
  • tumour growth factor
  • insulin like growth factor
146
Q

Describe the markers of cartilage degradation

A
  • serum and synovial keratin sulphate; increased levels indicate cartilage breakdown, level increases with age and patients with osteoarthritis
  • type 2 collagen in synovial; increased levels indicate cartilage breakdown, useful in evaluating cartilage erosion eg in osteoarthritis and rheumatoid arthritis
147
Q

Name some things that can go wrong in a joint

A
  • cartilage and synovial composition and function deteriorate with age and repeated wear and tear giving rise to osteoarthritis
  • synovial cell proliferation and inflammation cause rheumatoid arthritis
  • deposition of salt crystals eg uric acid can cause gouty arthritis
  • injury and inflammation to periarticular structures causes soft tissue rheumatism eg injury to the tendon causes tendonitis
148
Q

Deposition of what causes gouty arthritis?

A

Needle shaped uric acid crystals

149
Q

Deposition of what causes pseudo-gout?

A

Rhomboid shaped calcium pyrophosphate crystals

MSK (10 decks)

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