Physiology Flashcards
1
Q
What are the functions of skeletal muscle?
A
- posture
- purposeful movement
- respiratory movement
- heat production
- whole body metabolism
2
Q
Which muscle types are striated?
A
skeletal and cardiac are striated
smooth isn’t
3
Q
Which muscle types are voluntary?
A
skeletal muscle is voluntary (somatic)
smooth and cardiac muscle are involuntary (autonomic)
4
Q
What initiates skeletal muscle contraction?
A
neurogenic initiation
- no continuity of cytoplasm between nerve and skeletal cells
- ACh is used as a transmitter at NMJ
5
Q
What is a motor unit in a skeletal muscle fibre?
A
a single alpha motor neurone and all the skeletal fibres that it supplies
6
Q
Why does the number of muscle fibres per motor unit vary?
A
the number of fibres per motor unit depends on function
- fine movements: less fibres
- powerful movements: more fibres
7
Q
How are skeletal muscles attached to skeleton?
A
by tendons
8
Q
What are ATP and calcium ions needed for in contraction?
A
- ATP is needed for contraction to power cross bridges and relaxation release and to pump Ca2+ back into SR
- Ca2+ is needed to switch on cross bridge formation, this is link between excitation and contraction, it is derived from SR in skeletal muscle
9
Q
What is excitation contraction coupling?
A
where the surface potential results in activation of contractile structure of the muscle fibre
10
Q
What is the process of contraction?
A
- AP spreads down T tubules
- Ca2+ is released from lateral sacs of SR
- Ca2+ causes movement when it binds to troponin so tropnin-tropomysoin complex moves so actin has a free myosin binding site
- power stroke so actin is dragged
11
Q
What does the amount of skeletal muscle tension depend on?
A
- no. of muscle fibres contracting (motor unit stimulation)
- tensions developed by each muscle fibre (frequency of stimulation, summation and length of fibre at onset)
12
Q
What can prevent muscle fatigue?
A
asynchronous motor unit recruitment during sub maximal contractions
13
Q
When is skeletal muscle at optimal length?
A
under resting conditions and this is when there is optimum overlap of thick and thin filaments
14
Q
What can twitches help to do?
A
twitches can be summated so there is a stronger contraction as the duration of an AP is shorter than a twitch
15
Q
What is tetanus of muscle?
A
the muscle can be stimulated so rapidly that it can’t relax between stimuli (not possible in cardiac tissue due to long refractory period)
16
Q
How is skeletal muscle tension is transmitted to bone?
A
via stretching and tightening of muscle, connective tissue and tendon
17
Q
What are the two types of skeletal muscle contraction?
A
- isotonic contraction: eg body movements, muscle tension remains constant but muscle length changes
- isometric contraction: eg posture, muscle tension develops at constant muscle length
18
Q
What are the differences in skeletal muscle fibres?
A
- enzymatic pathways for ATP synthesis
- resistance to fatigue (greater ATP making capacity means less fatigue)
- activity of myosin ATPase (speed of contraction)
19
Q
How is ATP made?
A
- with ADP and creatine phosphate which is immediate (not high amounts)
- through oxidative phosphorylation (main source when there is O2)
- through glycolysis (when O2 is low)
20
Q
What are the characteristics of Type 1 fibres?
A
- slow twitch
- resistant to fatigue
- myoglobin
- red
- good for low work
- aerobic activities
aka slow oxidative
21
Q
What are the characteristics of Type 2a fibres?
A
- aka fast oxidative, intermediated twitch
- use both aerobic and anaerobic so useful in moderate work
- myoglobin
22
Q
What are the characteristics of Type 2x fibres?
A
- aka fast twitch or fast glycolytic
- use aerobic metabolism
- white
- short-term high intensity activities
23
Q
What are the features of the stretch reflex?
A
- simplest monosynaptic spinal reflex
- negative feedback that resists passive change in muscle length
- tap tendon with hammer
- rapid stretch of muscle so contraction
24
Q
What is the process in a stretch reflex?
A
- sensory receptor is muscle spindle
- stretch of spindle leads to increased firing in afferent neurone
- synapse to alpha motor neurons which innervate stretched muscle
- coordinated by relaxation of antagonists muscle
25
Where are the sensory receptors of the stretch reflex?
in the muscle spindles in the belly of muscles and they run parallel to ordinary fibres
they have sensory nerve endings called annulospiral fibres
26
What are the features of muscle spindles?
- discharge increases as muscle is stretched
- have own efferent supply by gamma motor neurones which adjust tension level to maintain sensitivity when muscle shortens
- do not contribute to strength
27
What can impairment of skeletal muscle function be caused by?
- intrinsic disease of muscle
- disease of NMJ
- disease of lower motor neurone which supply muscle
- disruption of input to motor neurones
28
What are general symptoms of muscle disease?
- muscle weakness
- delayed relaxation
- muscle pain
- stiffness
29
What are the investigations of neuromuscular disease?
- EMG- electrical activity of muscle
- nerve conduction studies
- muscle enzymes
- inflammatory markers
- muscle biopsy
30
What are the three types of joint?
- synovial
- fibrous: bones united by fibrous tissue, no movement eg skull
- cartilaginous: bones united by cartilage, limited movement eg symphysis
31
What are the features of synovial joints?
- cavity with synovial fluid
- united by fibrous capsule
- lined by synovial membrane of vascular connective tissue
- membrane contains synovial cells which make synovial fluid
32
What are the functions of synovial fluid?
- lubrication
- joint movement
- minimised wear and tear
- cartilage nutrition
- supplies chondrocytes with O2, nutrients and removes CO2 and waste
33
What is in synovial fluid?
- mucin gives it a high viscosity (this can vary with movement)
- other constituents are from dialysis of blood plasm
- only a few cells (increase in inflammation and septic arthritis)
34
What is needed for rapid movement in terms of synovial fluid?
- low viscosity
| - high elasticity
35
What are the features of articular cartilage?
- hyaline
- elastic
- sponge-like
- covers articular surfaces
- has ECM
36
What is in the ECM?
- water: maintains resiliency, contributes to nutrition and lubrication
- collagen: maintains stiffness
- proteoglycans: compressive properties and is weight bearing
37
How is ECM controlled and supplied?
- made and degraded by chondrocytes
| - it is avascular so cells receive sustenance by synovial fluid
38
What are the markers of cartilage degradation?
- serum and synovial keratin sulphate
| - type 2 collagen in synovial fluid
39
What are the crystals in pseudo-gout?
rhomboid shaped crystals of calcium pyrophosphate which are positively birefringent
40
What is transduction of a pain signal?
translation of noxious stimulus so there is electrical activity at peripheral nociceptor
41
What is transmission of pain signal?
propagation of pain signal as nerve impulses through the nervous system
42
What is modulation of pain signal?
hindering of pain transmission in nervous system
43
What is perception of pain signal?
conscious experience of pain leading to response
44
What is the role of nociceptors?
have free nerve endings for transduction and relay information to second order neurons in CNS
45
What is the process of pain signalling?
- neuron enters posterior/dorsal horn of spinal cord
- synapses with second order neurone using glutamate
- crosses spinal cord and ascends causing pain
46
What is the spinothalamic tract?
involved in pain response so location and intensity
47
What is the spinoreticular tract?
autonomic responses so arousal, emotion and fear
48
What are the different types of nociceptors?
- Adelta is fast pain, mechanic and thermal, myelinated
| - C fibres is slow and lasting pain, unmyelinated
49
What is nociceptive pain?
- response to injury
- intense stimulation of pain receptors
- adaptive pain
- warning to avoid harm
50
What is inflammatory pain?
- activation of immune system
- variety of mediators
- heightened due to painful stimuli
- stops movement of harmed area
51
What is pathological pain?
- neuropathic: damage to neural tissue causing burning, shooting or numbness
- dysfunctional: no identifiable damage, try anti-depressants as pain meds don't work
52
What is referred pain caused by?
convergence of nociceptive visceral and skin afferents upon same spinothalamic neurone
53
What is skeletal muscle innervated by?
- alpha motor neurones with myelinated axons
- these branch into unmyelinated axons that innervate individual fibres
- the terminal bouton is the synapse with ACh as transmitter
54
What happens presynaptically?
- choline symport with Na+
| - choline is combined with acetyl from acetyl CoA by CAT enzyme
55
What is needed to open the nicotinic ion channels?
two ACh per channel as these are pentameric ligand-gated channels
56
What is an e.p.p?
this is an end plate potential and is due to the influx of Na+ being greater than the efflux of K+ and many channels are opened
57
What happens when a vesicle relates ACh?
there is a quantum released every time
there is a m.e.p.p
many mepps make an epp
58
What happens to the ACh after?
- AChE hydrolyses it
- choline is taken up by choline transporter
- acetate diffuses from synaptic cleft
59
What is neuromyotonia?
- antibodies against voltage-activated K+ channels
- the AP is longer so cramps, stiffness
- treat with Na+ channel blockers
60
What is Lambert-eaton myasthenic syndrome?
- antibodies against Ca2+ voltage-activated channels sp less ACh release
- muscle weakness
- drug therapy targets AChE
- this is associated with small cell carcinoma
61
What does the Botulinum toxin do?
causes irreversible inhibition of ACh release at the junction so no AP and there is no treatment
62
What do curare-like compounds do?
- competitive antagonisms of nAChRs
- this reduces the epps so they are below threshold
- use din surgery fro reversible paralysis
