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physiology Flashcards

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1
Q

which muscles are striated

A

skeletal
cardiac

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2
Q

what are motor units

A

single alpha motor neurone and all the skeletal muscle it innervates

> skeletal muscle fibres are organised into motor units

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3
Q

how many muscle fibre cells in a motor unit

A

depends on the functions served by the skeletal muscle ie strength or precision

> muscles which serve fine movements eg external eye muscles or muscle of facial expression have fewer intrinsic fibres than muscles that need power ie vastus medialis

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4
Q

what is a functional unit

A

sarcomere is the functional unit of skeletal muscle

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

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5
Q

functions of skeletal muscle

A

posture
movement
breathing
heat prod.
whole body metabolism

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6
Q

3 types of muscle tissue

A

skeletal
cardiac
smooth

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7
Q

what is the ‘voluntary’ muscle

A

skeletal

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8
Q

how can striation be visualised

A

myosin and actin filaments

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9
Q

what innervates skeletal

A

somatic -

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10
Q

what innervates cardiac and smooth

A

-

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11
Q

initiation and propagation of skeletal muscle

A

neurogenic
motor units
neuromuscular junction present
No gap junctions

calcium comes entirely from sarcoplasmic reticulum

> no continuity of cytoplasm between nerve and skeletal muscle cells

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12
Q

initiation and propagation of cardiac muscle

A

myogenic
no neuromuscular junction
gap junctions present

calcium comes from ECF and sarcoplasmic reticulum

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13
Q

what is a myofibril

A

specialised intracellular structure involved in contraction and is organised into sarcomeres

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14
Q

how many bands does the sarcomere have

A

4 bands :
A band
H zone
M line
I band

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15
Q

what is excitation contraction coupling

A
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16
Q

where is calcium released from in skeletal muscle fibres

A

lateral sacs of sarcoplasmic reticulum

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17
Q

why is calcium required

A

to switch on cross bridge formation
-it is the link between excitation and contraction
-is entirely derived from sarcoplasmic reticulum in skeletal muscles

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18
Q

what is the difference between actin myosin / excitation /calcium contraction in cardiac muscle and skeletal muscle

A

?

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19
Q

what is skeletal muscle contraction initiated by

A

neurogenic initiation

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20
Q

what is the transmitter at the neuromuscular junction

A

acetylcholine

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21
Q

why is ATP needed

A

contraction: to power cross bridges

relaxation:
release cross bridges and to pump Ca back into sarcoplasmic reticulum (rigor mortis)

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22
Q

what are the two influences that act on tension developed by skeletal muscle

A

-the no of muscle fibres contracting
-the tension developed by each contracting muscle fibres

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23
Q

how does frequency of stimulation and summation of contractions brings about increased tension in skeletal muscle

A
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24
Q

describe the two primary types of skeletal muscle contraction

A
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25
what can develop at optimum muscle length
maximum muscle tension
26
what is a reflex action
stereotyped response to a specific stimulus they are the simplest form of coordinated movement
27
why might you get impairment of muscle function
intrinsic muscle disease neuromuscular junction disease pathology of lower motor neurons disruption of input to motor nerves
28
what allows for simultaneous contraction of a number of muscle fibres
motor units
28
what allows for simultaneous contraction of a number of muscle fibres
motor units
29
how might a stronger contraction be achieved
motor unit recruitment
30
what helps prevents muscle fatigue during sub maximal contraction
asynchronous motor unit recruitment
31
what are the factors affecting tension developed by each contraction muscle fibre
-thickness -length of muscle fibre -frequency of stimulation and summation
32
twitch summation and tetanus in skeletal muscle
33
what happens when skeletal muscle is stimulated once
a single contraction called a twitch is produced
34
what happens when skeletal muscle receives a second stimulation before it had time to completely relax
the second response is much greater...
35
T or F : the resting length of skeletal muscle is the optimal length
T
36
what are the 2 types of skeletal muscle contraction
isotonic = muscle tension remains constant as the muscle length changes, useful for body movements and moving objects isometric = muscle tension develops at constant muscle length , useful in supporting objects in fixed position and for maintaining body posture
37
what are the main differences between skeletal muscle fibres
1. enzymatic pathways for ATP synthesis 2. resistance to fatigue (muscle fibres with greater capacity to synthesise ATP are more resistant to fatigue) 3. activity of myosin ATPase - this determines the speed at which energy is made available - the speed of contraction
38
how many types of fibres does a motor unit usually have
one
39
the three types of skeletal muscle fibres
slow oxidative - slow twitch ie walking , aerobic fast oxidative - intermediate twitch ie aerobic and anaerobic , jogging fast glycolytic - fast twitch ie sprinting , anaerobic
40
why are neural pathways for reflexes important
can help to localise lesions
41
the stretch reflex
negative feedback mechanism that resists p passive changes in muscle length to maintain optimal resting length of muscle helps maintain posture the sensory receptor is the muscle spindle and is activated by muscle strength stretching the muscle spindle increases firing in the afferent neurons
42
where do the afferent neurons synapse
in the spinal cord
43
intrafusal vs extrafusal
44
what are muscle spindles
collection of specialised muscle fibres
45
causes of intrinsic muscle disease
genetically determined myopathies : congenital chronic degeneration - dystrophy abnormalities in muscle membrane ion channels - myotonia acquired : inflammatory non-inflammatory endocrine toxic - alcohol
46
symptoms of muscle disease
muscle weakness / tiredness stiffness -
47
useful investigation
creatinine kinase nerve conduction studies inflammatory marker biopsy EMG
48
what are the joints of the body
synovial fibrous cartilaginous
49
do fibrous joints allow movement
doesn't allow movement
50
do cartilaginous joints allow movement
allow limited movement ie intervertebral discs , pubic symphysis
51
features of the synovial joints
the bones are separated by a cavity - filled with synovial fluid - and united by a fibrous capsule
52
what is the inner aspect of fibrous capsule (of synovial joints) lined with
synovial membrane
53
what is the synovial membrane
vascular connective tissue (with capillary networks and lymphatics) -contains synovial cells (fibroblasts) which produces the synovial fluid - about 60um thick in the human knee
54
what is a simple synovial joint
one pair of articular surfaces ie metacarpophalangeal
55
what is a compound synovial joint
more than one pair of articular surfaces eg elbow joint
56
purposeful function of joints
stress distribution confer stability joint lubrication ie cartilage interstitial fluid
57
synovial fluid features
>continuously replenished and absorbed by synovial membrane ie not a static pool >has a high viscosity - due to presence of hyaluronic acid produced by the synovial cells >viscosity and elasticity varies with joint movement
58
what happens to viscosity and elasticity in rapid movements
viscosity decreases elasticity increases
59
what happens to synovial fluid when in a traumatic synovial tap (and also in haemorrhagic arthritis)
turns red
60
what should normal synovial fluid look like
clear colourless and viscous normally has less than 200WBC
61
what does synovial fluid look like from a severely inflamed joint
thin and opaque
62
main functions of articular cartilage
prevents wear and tear - low friction lubricated gliding surfaces distributes contact pressure to subchondral bone the composition of the cartilage ECM and interaction between the fluid and solid phase of the cartilage determines the mechanical properties of cartilage
63
structural properties of articular cartilage
>elastic and sponge like - usually hyaline >covers articular surfaces of bones >has special ECM made predominantly of water and collagen , also proteoglycans water: maintains resiliency of tissues and contribute to the nutrition and lubrication system collagen: provides tensile stiffness and strength proteoglycan: provides compressive properties associated with load bearing
64
specialised ECM of articular cartilage
synthesised, organised and degraded by chondrocytes avascular - so has poor healing in normal joints the rate at which the ECM is degraded doesn't exceed the rate at which it is replaced (joint disease can occur if the rate of ECM degradation exceeds the rate of its synthesis)
65
catabolic factors of ECM synthesis
they stimulate proteolytic enzymes and inhibit proteoglycan synthesis
66
what may 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 > arthritis deposition of salt crystals injury and inflammation to periarticular structures cause soft tissue rheumatism
67
anabolic factors of ECM synthesis
stimulate proteoglycan synthesis and counteract effects of interleukin-1

msk (24 decks)

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