Physiology Flashcards
(132 cards)
1
Q
What two muscle types are striated?
A
Skeletal and cardiac
2
Q
What is muscle striation caused by?
A
Alternating dark bands of myocin (thick filaments) and light bands of actin (thin filaments)
3
Q
What are skeletal muscle fibres organised into?
A
Motor units
4
Q
What is a motor unit?
A
A single alpha motor neuron and all the skeletal muscle fibres it innervates.
5
Q
What is the relationship between number of muscle fibres per motor unit and function of muscle?
A
Muscles which serve fine movements have fewer fibres per motor unit.
6
Q
Give three examples of fine movement muscles?
A
- External eye muscles
- Muscles of facial expression
- Intrinsic hand muscles
7
Q
What makes up myofibrils?
A
Sacromeres
8
Q
What type of initiation of contraction is involved in skeletal muscle?
A
Neurogenic
9
Q
What type of initiation of contraction is involved in cardiac muscle?
A
Myogenic
10
Q
What type of muscle has motor units, no gap junctions but has neuromuscular junctions present?
A
Skeletal
11
Q
What type of muscle has no neuromuscular junction but has gap junctions?
A
Cardiac
12
Q
In skeletal muscle contraction - where does the calcium come entirely from?
A
Sarcoplasmic reticulum
13
Q
In cardiac muscle contraction - where does the calcium come from?
A
ECF and sarcoplasmic reticulum
14
Q
What is the process whereby the surface action potential results in activation of the contractile mechanism of the muscle fibre?
A
Excitation contraction coupling
15
Q
In skeletal muscle - when is the calcium released from the lateral sacs of the sarcoplasmic reticulum?
A
When the surface action potential spreads down the transverse T-tubules
16
Q
What is the transmitter at the neuromuscular junction?
A
Acetylcholine
17
Q
What is the functional unit of skeletal muscle?
A
Sacromeres
18
Q
What is the smallest component capable of performing all the function of that organ called?
A
Functional unit
19
Q
Where is the sacromere found between?
A
Two Z-lines
20
Q
What do Z-lines connect?
A
The thin filaments of 2 adjoining sacromeres
21
Q
What is the A-band made up from?
A
Thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
22
Q
What is the name for the lighter area within middle of A-band where thin filaments do not reach?
A
H-zone
23
Q
What line extends vertically down the middle of A-band within centre of H-zone?
A
M-line
24
Q
What does the I-band consist of?
A
Remaining portion of thin filaments that do not project in A-band
25
How is muscle tension produced?
By sliding of actin filaments on myocin filaments
26
What is required for both contraction and relaxation of muscle fibres?
ATP
27
What is required to switch on cross bridge formation?
Calcium
28
What two primary factors does gradation of skeletal muscle tension depend on?
1. Number of muscle fibres contracting within the muscle
| 2. Tension developed by each contracting muscle fibre
29
What allows simultaneous contraction of a number of muscle fibres?
Motor units
30
A stronger contraction could be achieved by stimulation of more motor units - what is this known as?
Motor unit recruitment
31
During submaximal contractions - what helps prevent muscle fatigue?
A synchronous motor units
32
What three factors does tension developed by each contracting muscle fibre depend on?
1. Frequency of stimulation
2. Summation of contractions
3. Length of muscle fibres
33
In skeletal muscle: what is the duration of action potential much shorter than?
Duration of resulting twitch
34
What does repetitive fast stimulation of skeletal muscle bring about?
Summates twitches to bring about a stronger contraction
35
If a muscle fibre is restimulated after it has completely relaxed, what length is the is the second twitch?
Same magnitude as first twitch
36
If a muscle fibre is restimulated before it has completely relaxed, what happens?
Second twitch is added onto the first resulting in summation
37
What occurs when a muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli?
A maximal sustained contraction known as tetanus occurs
38
Can cardiac muscle be tetanised? Explain.
No - the long refractory period prevents generation of tetanic contraction
39
When can maximal tetanic contraction be achieved?
When muscle is at its optimal length before the onset of contraction.
40
In teh body the resting length of a skeletal muscle is approximally what?
Its optimal length
41
What is isotonic contraction used for?
Body movements and for moving objects - muscle tension remains constant as the muscle length changes
42
What are isometric contractions used for?
Supporting objects in fixed positions and for maintaining body posture - muscle tension develops at constant muscle length.
43
In both isotonic and isometric contractions muscle tension is transmitted to the bone via what?
Elastic components of muscle
44
The velocity of muscle shortening decreases as the load what?
Increases
45
What four things could cause impairment of skeletal muscle function
1. Intrinsic disease of muscle
2. Disease of NMJ
3. Disease of lower motor neurones which supply the muscle
4. Disruption of inputs to motor unit
46
Give 3 examples of genetically determined myopathies that cause intrinsic muscle disease?
1. Congenital myopathies
2. Muscular dystrophy
3. Myotonia
47
Give a disease which involves chronic degeneration of contractile elements?
Muscular dystrophy
48
Give a disease which involves abnormalities in muscle membrane ion channels?
Myotonia
49
Name three subgroups of acquired myopathies which cause intrinsic muscle disease?
1. Inflammatory myopathies
2. Endocrine myopathies
3. Toxic myopathies
50
Name an inflammatory myopathy?
Polymyosytis
51
Name an endocrine myopathy?
Cushing syndrome, thyroid disease
52
Name a toxic myopathy?
Alcohol, statins
53
What is the simplest monosynaptic spinal reflex?
Stretch reflex
54
What serves as a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle?
Stretch reflex
55
What is the sensory receptor in stretch reflex and what is it activated by
Muscle spindle - activated by muscle stretch
56
What does stretching the muscle spindle increase?
Firing in the afferent neurons
57
What do afferent neurons synapse in the spinal cord with?
Alpha motor neurons (efferent limb of the stretch reflex) that innervate the stretched muscle
58
What is the stretch reflex coordinated by?
Antagonist muscle
59
Name the spinal segment and peripheral nerve for knee jerk?
L3, L4
| Femoral nerve
60
Name the spinal segment and peripheral nerve for ankle jerk?
S1, S2
| Tibial nerve
61
Name the spinal segment and peripheral nerve for biceps jerk?
C5-C6
| Musculocutaneous nerve
62
Name the spinal segment and peripheral nerve for Brachioradialis jerk?
C5-C6
| Radial nerve
63
Name the spinal segment and peripheral nerve for triceps jerk?
C6-C7
| Radial nerve
64
What are muscle spindles known as?
Intrafusal fibres
65
What are ordinary muscle fibres referred to as?
Extrafusal fibres
66
Where are muscle spindles found?
Within the belly of muscles and run parallel to ordinary muscle fibres
67
What are the sensory nerve endings on muscle spindles known as?
Annulospiral fibres
68
What has its own efferent (motor) nerve supply
Muscle spindle
69
What are the efferent neurons that supply muscle spindles called?
Gamma motor neurons
70
What adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscle shortens during muscle contraction
Gamma-motor neurones
71
What three factors cause differences between different types of skeletal muscle fibres?
1. The enzymatic pathways for ATP synthesis
2. The resistance to fatigue
3. The activity of myosin ATPase
72
What are muscle fibres with greater capacity to synthesise ATP more resistant to?
Fatigue
73
What does activity of myosin ATPase determine?
Speed of contraction
74
What are the three metabolic pathways that supply ATP in muscle fibre?
1. Transfer of high energy phosphate from creatinine Phosphate to ADP - immediate source
2. Oxidative phosphorylation: main source when O2 present
3. Glycolysis: main source when O2 not present
75
What activities are slow oxidative type I fibres used for?
Prolonged relatively low work aerobic activities
76
What activities are fast oxidative (type IIa) fibres used for?
Prolonged relatively moderate work activities (jogging) - use both aerobic and anaerobic metabolism
77
What activities are fast glycolytic (type IIx) fibres used for?
Short-term high intensity activities (jumping) - use anaerobic metabolism
78
What susbtance is released when muscles are damaged?
Creatine kinase
79
What are the three types of joints?
1. Synovial
2. Fibrous
3. Cartilaginous
80
What type of joint is bones united by fibrous tissue - they do not allow any movement?
Fibrous (synarthrosis)
81
What type of joints are bones united by cartilage - they also allow limited movement?
Cartilaginous joint (amphiarthrosis)
82
Give four examples of cartilaginous joints?
1. Intervertebral discs
2. Pubic symphsis
3. Part of sacroiliac joints
4. Costochondral joints
83
What type of joint has bones seperated by a cavity (containing synovial fluid) and united by a fibrous capsule?
Synovial joint (diarthrosis)
84
In a synovial joint - what is the inner aspect of fibrous capsule lined with?
Synovial membrane
85
What - in the synovial joint - is vascular connective tissue with capillary networks and lymphatics?
Synovial membrane
86
What does the synovial membrane contain which produces synovial fluid?
Synovial cells (fibroblasts)
87
What is the difference between simple and compound synovial joints?
Simple ones have one pair of articular surfaces, compound have more than one pair of articular surfaces.
88
Give an example of a simple synovial joint?
Metacarpalphalangeal joint
89
Give an example of a compound synovial joint?
Elbow joint
90
Joints have a role of stress distribution - what is the greatest share of loading energy taken up within?
Muscles and tendons crossing each other
91
What three things provide joint lubrication?
1. Cartilage interstitial fluid
2. Synovium-derived hyaluronic acid (mucin) which is a polymer of disaccharides
3. Synovium-derived lubrcin - a glycoprotein
92
What part of a synovial joint supplies the chondrocytes with O2 and nutrients and removes CO2 and waste products?
Synovial fluid
93
What is the synovial fluid continuously replinished and absorbed by?
The synovial membrane - not a static pool
94
Why does the synovial fluid have a high viscosity?
Mainly due to presence of hyaluronic acid (mucin) produced by synovial cells
95
What does the viscosity of synovial fluid vary with?
Joint movement
96
What is the other consituent of synovial fluid (uric acid) derived by?
Dialysis of blood plasma
97
Normally the synovial fluid contains few cells, what are they mainly?
Mononuclear leucocytes
98
What happens to the synovial fluid with rapid movement?
Decreased viscosity and increased elasticity
99
What condition causes the viscosity and elasticity to become defective?
Osteoarthritis
100
Describe normal synovial fluid?
Clear and colourless
101
What is the normal WBC count in synovial fluid?
102
What does synovial fluid WBC increase in?
Inflammatory and septic arthritis
103
What does synovial fluid turn red in?
Traumatic synovial tap and in haemorrhagic arthritis
104
In inflammatory synovial fluid: what is the viscosity, colour, clarity, total WCC and PMN lecuocytes?
```
Low
Straw to yellow
Translucent
2000 - 75000
often >50
```
105
In septic synovial fluid: what is the viscosity, colour, clarity, total WCC and PMN leucocytes?
```
Variable
Variable
Opaque
Often > 100 000
Often >75
```
106
What are the 4 zones of articular cartilage?
Superficial (10-20%)
Middle (40-60%)
Deep (30%)
Calcified
107
What is the ECM of articular cartilage made of?
Water (70%) and collagen (20%) - mainly type II contributes most to the elastic behaviour of cartilage and proteoglycans (10%)
108
In articular cartilage - where os water mostly found?
Near articular surface
109
What does cartilage water content decrease with?
Age
110
Where is highest concentration of proteoglycan in cartilage found?
In middle and deep zone
111
What is proteoglycan found in cartilage mainly composed of?
Glycosaminoglycan e.g. chondroitin suphate
112
What does chondroitin in cartilage decrease with?
Age
113
What is proteoglycan in cartilage responsible for in the role of joint?
Compressive properties associated with load baring
114
What is the water in cartilage responsible for in role of joint?
Resiliency of tissue, nutrition and lubrication
115
What is the collasgen in cartilage responsible for in joints?
Tensile stiffness and strength
116
What does cartilage ECM usually constitue of the total cartilage volume?
>98%
117
What is the ECM of articular cartilage syntehsised, organised, degraded and maintained by?
Chondrocytes (
118
The articular cartilage is avascular so where do cartilage ells receive nutrients and O2 from?
Synovial fluid
119
In the cartilage ECM turnover - what has a negative effect (i.e. breakdown)?
Metalloproteinase proteolytic enzymes e.g. collagenase and stromelysin
120
What occurs when ECM of cartilage degradation exceeds rate of synthesis?
Joint disease
121
In cartilage ECM turnover: what does catabolic factors do?
Stimulate proteolytic enzymes and inhibit proteoglycan synthesis
122
In cartilage ECM turnover: what two immune componenets are involved catabolically?
TNF-alpha
| IL-1
123
In cartilage ECM turnover: what does anabolic factors do?
Stimulate proteoglycan synthesis and counteract effects of IL-1
124
In cartilage ECM turnover: what two immune components are involved anabolically?
TGF-beta
| IGF-1
125
What do increased levels of serum and synovial keratin sulphate suggest?
Cartilage breakdown - level increases with age and patients with osteoarthritis
126
What does increased levels of type II colagen in synovial fluid suggest?
Cartilage breakdown - useful in evaluating cartilage erosion in osteoarthritis and rheumatoid arthritis
127
Cartilage and synovial composition and function deterioate with age and repeated wear and tear giving rise to what?
Osteoarthritis
128
What does synovial cell proliferation and inflammation cause?
Rheumatoid arthritis
129
What does deposition of needle shaped salt crystals e.g. uric acid cause?
Gouty arthritis
130
What does injury and inflammation to periarticular structures cause?
Soft tissue rheumatism e.g. injury to the tendon causes tendonitis
131
What is subchondral sclerosis and cystic formation found in?
Osteoarthritis
132
What does deposition of rhomboid shaped calcium pyrophosphate crystals cause?
Pseudo-gout
