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
2
Q
Name the four distinct processes in the physiology of pain
A
- transduction
- transmission
- modulation
- perception
3
Q
Describe transduction
A
Translation of noxious stimulus to electrical activity at the peripheral nociceptor
4
Q
Describe transmission
A
Propagation of pain signal as nerve impulses through the nervous system
5
Q
Describe modulation
A
Modification / hindering of pain transmission in the nervous system eg. by inhibitory neurotransmitters like endogenous opiods
6
Q
Describe perception
A
Conscious experience of pain. Causes physiological and behavioural responses
7
Q
Pain begins with activation of what?
A
Nociceptors
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
9
Q
Name the neurotransmitters of the nociceptive pathway
A
- glutamate
- peptides (substance P, neurokinin A)
10
Q
Second order neurons ascend the spinal cord where?
A
In the anterolateral system (terminate in the thalamus)
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
12
Q
Nociceptors are activated by what?
A
- mechanical, thermal or chemical stimuli that are noxious
13
Q
Transduction of nociceptors begins where and is mediated by what?
A
- begins in free nerve endings
- mediated by numerous receptors and channels
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
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
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
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
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
19
Q
Define allodynia
A
Pain sensitivity to innocuous stimuli
20
Q
Define hyperalgesia
A
Pain sensitivity to noxious stimuli
21
Q
Name the two types of pathological pain
A
- neuropathic
- dysfunctional
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
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
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
25
Name the physiological functions of skeletal muscles
- maintenance of posture
- purposeful movement in relation to external environment
- respiratory movements
- heat production
- contribution to whole body metabolism
26
Name the three types of muscle in the body
- skeletal
- cardiac
- smooth
27
How do muscles develop tension and produce movement?
Through contraction
28
Which muscle is striated and which is not?
- skeletal and cardiac are striated
| - smooth muscle is not
29
What is striation?
- can be visualised under a light microscope as alternating dark bands and light bands
30
What causes the dark and light bands of striated muscle?
- dark bands are caused by myosin thick filaments
| - light bands are caused by actin thin filaments
31
Skeletal muscles are innervated by what?
The somatic nervous system and are subject to voluntary control
32
Cardiac and smooth muscles are innervated by what?
The autonomic nervous system - involuntary
33
Is skeletal muscle neurogenic or myogenic?
Neurogenic
34
The Ca++ for contraction of skeletal muscle originates from where?
The sarcoplasmic reticulum
35
Gradation of contraction of skeletal muscle is dependent on what?
- by motor unit recruitment
| - summation of contractions
36
Skeletal muscle fibres are organised into what?
Motor units
37
What are motor units?
A single alpha neuron and all the skeletal muscle fibres it innervates
38
The number of muscle fibres per motor unit depends on what?
The functions served by the muscle
39
What type of muscles have fewer fibres per motor unit?
- muscles which serve fine movements (eg external eye muscles, muscles of facial expression; and intrinsic hand muscles)
40
Skeletal muscles are usually attached to the skeleton by what?
Tendons
41
Skeletal muscle consists of what?
Parallel muscles fibres bundled by connective tissue
42
Each muscle fibre contains what?
Myofibrils
43
What are myofibrils?
- specialised contractile intracellular structures
| - the myofibrils have alternating segments of thick and thin protein filaments
44
With each myofibril, actin and myosin are arranged into what?
Sarcomeres
45
What is the functional unit of muscle?
Sarcomeres
46
Which of the filaments are thin and which are thick?
- actin are the thin filaments
| - myosin are the thick filaments
47
What separates sarcomeres?
Z lines
48
What does the z line connect?
The thin filaments of 2 adjoining sarcomeres
49
How many zones does a sarcomere have?
4
50
Name the 4 zones of sarcomeres
- A band
- H zone
- M line
- I band
51
What is the A band?
Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
52
What is the H zone?
Lighter area within middle of A band where thin filaments dont reach
53
What is the M line?
Extends vertically down the middle of an A band within the centre of the H zone
54
What is the I band?
Consists of remaining portion of thin filaments that do not project in A band
55
Muscle tension is produced by what?
Sliding of actin filaments over myosin filaments
56
Force generation depends on what?
ATP dependent interactions between thick and thin filaments
57
What is calcium required for?
To switch on cross bridge formation
58
What is ATP required for?
Both contraction and relaxation
59
What is excitation contraction coupling?
The process whereby the surface action potential results in activation of the contractile structures of the muscle fibre
60
In skeletal muscle fibres. where is calcium released from?
The lateral sacs of the sarcoplasmic reticulum when the surface action potential spreads down the transverse tubules
61
What are T tubules?
Extensions of the surface membrane that dip into the muscle fibre
62
Spread of action potential down the t tubules triggers what?
The release of calcium ions from lateral sacs of sarcoplasmic reticulum
63
Ca2+ is the link between what?
Excitation and contraction
64
ATP is needed during muscle contraction to?
Power cross bridges
65
ATP is needed during relaxation to?
- release cross bridges
| - to pump Ca2+ back into the sarcoplasmic reticulum
66
Gradation of skeletal muscle tension depends on what two primary factors?
- number of muscle fibres contracting within the muscle
| - tension developed by each contracting muscle fibre
67
Describe the number of muscle fibres contracting within the muscle in relation to gradation of skeletal muscle tension
- 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
Describe the tension developed by each contracting muscle fibre in relation to gradation of skeletal muscle tension
- depends on frequency of stimulation and summation of contractions
- length of muscle fibre at the onset of contraction
- thickness of muscle fibre
69
In skeletal muscle the duration of action potential is longer or shorter than the duration of resulting twitch?
Shorter
70
As the duration of the action potential is much shorter than the duration of the resulting twitch, it is possible to do what?
To summate twitches to brings about a stronger contraction through repetitive fast stimulation of skeletal muscle
71
What happens if the skeletal muscle is stimulated once?
A single contraction called a twitch is produced
72
What happens if skeletal muscle receives a second stimulation before it has time to completely relax?
The second response adds to the first and a greater muscle tension is developed
73
The tension developed by skeletal muscle increases with what?
Increasing frequency of stimulation
74
Maximal tetanic contraction can be achieved when?
The muscle is at its optimal length before the onset of contraction
75
Developed tension depends on what?
The initial length of skeletal muscle fibre
76
The resting length of a skeletal muscle is what?
Approximately its optimal length
77
What is isotonic contraction?
Used for body movements and for moving objects. Muscle tension remains constant as the muscle length changes
78
What is isometric contraction?
Used for supporting objects in fixed positions and for maintaining body posture. Muscle tension develops at constant muscle length
79
What are the two types of skeletal muscle contraction?
Isotonic and isometric contraction
80
In both isotonic and isometric contraction, muscle tension is transmitted to the bone via what?
The elastic components of muscle
81
The velocity of muscle shortening decreases as what increases?
Load
82
What are the main differences between different types of skeletal muscle fibres?
- 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
Name some metabolic pathways that supply ATP in muscle fibres
- 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
How many types of skeletal muscle fibres are there?
3
85
Name the three types of skeletal muscle fibre
- slow oxidative type 1 fibres
- fast oxidative type 2a fibres
- fast glycolytic type 3 fibres
86
Describe slow oxidative type 1 fibres
- also known as slow twitch fibres
| - used mainly for prolonged relatively low work aerobic activities eg maintenance of posture, walking
87
Describe fast oxidative type 2a fibres
- also known as intermediate twitch fibres
| - use both aerobic and anaerobic metabolism and are useful in prolonged relatively moderate work activities eg jogging
88
Describe fast glycolytic type 3 fibres
- also known as fast twitch fibres
| - use anaerobic metabolism and are mainly used for short term high intensity activities eg jumping
89
Input from a variety of sources influence the activity of motor units to produce?
Purposeful skeletal muscle activity
90
What is a reflex action?
A stereotyped response to a specific stimulus
91
What are the simplest form of coordinated movement?
Reflex actions
92
Where are the pathways responsible for reflex actions located?
At various levels of the motor system
93
What is the simplest monosynaptic spinal reflex?
The stretch reflex
94
The stretch reflex helps to do what?
Helps maintain posture eg when walking
95
The sensory receptor is the muscle spindle and is activated by what?
Muscle stretch
96
Stretching the muscle spindle increases firing where?
In the afferent neurons
97
The afferent neurons synapse where?
In the spinal cord with the alpha motor neurones ( efferent limb of the stretch reflex) that innervate the stretched muscle
98
The stretch reflex is coordinated by what?
Simultaneous relaxation of antagonist muscle
99
The stretch reflex can be elicited by what?
Tapping the muscle tendon with a rubber hammer
100
Name some examples of tendon reflexes that can be elicited by rubber hammer
- knee jerk
- ankle jerk
- biceps jerk
- brachioradialis
- triceps jerk
101
What are the sensory receptors for stretch reflex?
Muscle spindles
102
What are muscle spindles?
Collection of specialised muscle fibres
103
What else are muscle spindles known as?
Intrafusal fibres
104
Ordinary muscle fibres are referred to as what?
Extrafusal fibres
105
Where are muscle spindles found?
Within the belly of muscles and run parallel to ordinary muscle fibres (extrafusal fibres)
106
Muscle spindles have sensory nerve endings known as what?
Annulospiral fibres
107
The discharge from the muscle spindle sensory endings increases or decreases as the muscle is stretched?
Increases
108
The efferent neurons that supply muscle spindles are called what?
Gamma motor neurons
109
What do the gamma motor neurons do?
Adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscle shorten during muscle contraction
110
Impairment of skeletal muscle function may be caused by?
- 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
Name some causes of intrinsic muscle disease
- genetically determined myopathies
| - acquired myopathies
112
Name some genetically determined myopathies
- 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
Name some acquired myopathies
- 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
Name some symptoms of muscle disease
- muscle weakness / tiredness
- delayed relaxation after voluntary contraction (myotonia)
- muscle pain (myalgia)
- muscle stiffness
115
Name some useful investigations in neuromuscular disease
- electromyography (EMG)
- nerve conduction studies; determines the functional integrity of peripheral nerves
- muscle enzymes eg CK
- inflammatory markers
- muscle biopsy
116
What is electromyography?
- 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
Name the three types of joint
- synovial
- fibrous
- cartilaginous
118
What is a fibrous joint?
- synarthrosis
- bones united by fibrous tissue
- doesn't allow any movement
- example; sutures of the skull in adults
119
What is a cartilaginous joint?
- amphiarthrosis
- bones united by cartilage
- allow limited movement
- examples; intervertebral discs, pubic symphysis, part of the sacroiliac joints, costochondral joints
120
What is a synovial joint?
- 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
Describe the synovial membrane
- 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
The articular surfaces of bone are covered with what?
Cartilage
123
What are the two classes of synovial joints?
- simple
| - compound
124
What are simple and compound synovial joints?
- simple; one pair of articular surfaces eg metacarpophalangeal joint
- compound; more than one pair of articular surfaces eg elbow joint
125
What are joints supported by?
Extra-articular structures such as brusa, ligaments and tendons
126
What is the physiological functions of joints?
To serve the functional requirements of the MSK system
- structural support
- purposeful movement
127
Describe the roles of joint during purposeful motion
- stress distribution
- confer stability
- joint lubrication
128
Describe conferring stability in relation to the role of joints
- 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
Describe joint lubrication provided in relation to the role of joints
- 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
Describe the functions of synovial fluid
- 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
Describe the general characteristics of the synovial fluid
- 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
Describe the changes in synovial fluid viscosity and elasticity during joint movement
- 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
Describe the appearance of synovial fluid
The normal synovial fluid is clear and colourless
| - the synovial fluid turns red in traumatic synovial tap and in haemorrhagic arthritis
134
What is the normal cell count of synovial fluid?
- it has <200 WBC/mm3 of which polymorphs are usually <25mm3
| - the synovial fluid WBC count increases in inflammatory and septic arthritis
135
Describe the main functions of articular cartilage
- 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
Name the four zones of articular cartilage
- superficial zone
- middle zone
- deep zone
- calcified zone
137
How do the zones of articular cartilage differ?
Zones differ in organisation of collagen fibres and relative content of cartilage components
138
Describe the articular cartilage
- 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
Describe the mechanical properties of the major cartilage components
- water
- collagen
- proteoglycan
140
Describe the water of major cartilage components
- 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
Describe the collagen of major cartilage components
- 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
Describe the proteoglycan of major cartilage components
- 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
Describe the extracellular matrix of articular cartilage
- 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
Describe catabolic factors of cartilage matrix turnover
- stimulate proteolytic enzymes and inhibit proteoglycan synthesis
- tumour necrosis factors
- interleukin
145
Describe anabolic factors of cartilage matrix turnover
- stimulate proteoglycan synthesis and counteract effects of IL-1
- tumour growth factor
- insulin like growth factor
146
Describe the markers of cartilage degradation
- 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
Name some things that can go wrong in a joint
- 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
Deposition of what causes gouty arthritis?
Needle shaped uric acid crystals
149
Deposition of what causes pseudo-gout?
Rhomboid shaped calcium pyrophosphate crystals
