Physiology Flashcards
Name the 3 types of muscle in the body
Skeletal
Cardiac
Smooth
Which of the 3 types of muscle lack striation?
Smooth muscle
Which of the 3 types of muscles are under voluntary control?
Skeletal muscle
Somatic NS innervation
What is a skeletal muscle motor unit?
One alpha motor neurone
+ all the skeletal muscle fibres it innervates
How does the number of muscle fibres within a motor unit affect overall function?
Greater number = more power but less precision
Fewer number = finer control but less power
In skeletal muscles, where does Ca come from to initiate contraction?
ENTIRELY from sarcoplasmic reticulum
Where must action potential spread before Ca can be released by the SR?
Down transverse T tubules
Released from lateral sacs of SR
What are the 4 sarcomere zones?
A-band
H-zone
M-line
I-band
Which ion is required for cross-bridge formation during muscle contraction?
Ca++
How does Ca cause cross-bridge formation?
Binds to troponin
What is the transmitter of impulses at the neuromuscular junction?
Acetylcholine
What is ATP used for in muscle contraction?
Power cross bridges
What is ATP used for in muscle relaxation?
Release cross bridges
Pump Ca back into the SR
How does the duration of action potential in skeletal muscles relate to that of the resulting twitch?
AP is much shorter than the twitch
- allows summation for stronger contraction
What is tetanus of a skeletal muscle?
Maximal sustained contraction
How is a muscle tetanised?
Rapid action potentials to muscle fibres do not allow opportunity for relaxation, so summation occurs to its highest (constant) level
Is tetanus possible in cardiac muscle?
No
- long refractory period prevents constant/summative twitches
When might you get maximal tetanic contraction?
When muscle is at its optimal length before contraction
- for skeletal muscle, this is its resting length
What are the 2 types of skeletal muscle contraction?
Isotonic
Isometric
What is isotonic contraction?
Tension in muscle remains constant but its length changes
e.g. during movement
What is isometric contraction?
Muscle tension develops at a constant muscle length
e.g. maintaining posture, holding objects
How is muscle tension transmitted to bone?
Via elastic components of the muscle
What is the relationship between velocity of muscle shortening and its load?
Inverse
- max vel. at zero load
- zero vel. at max load (isometric contraction)
Describe the stretch reflex
Negative feedback
Resists passive change in muscle length to maintain its optimal length
What are the sensory receptors of the stretch reflex?
Muscle spindle
- aka intrafusal fibres
- collection of specialised muscle fibres
What are annulospiral fibres?
Sensory nerve endings of muscle spindles
What are the efferent neurones that supply muscle spindles?
Gamma motor neurones
- sense that the muscle has been stretched beyond optimum length
Name 3 metabolic sources of ATP to the muscle fibre
Transfer of phosphate from creatine phosphate to ADP
Oxidative phosphorylation
Glycolysis
What are the 3 types of muscle fibres?
Type I - SLOW oxidative
Type IIa - Intermediate
Type IIx - FAST glycolytic
Which activities are Type I muscle fibres more suited for?
- slow twitch
- for prolonged, low intensity, aerobic work
e. g. walking, maintaining posture
Which activities are Type IIa muscle fibres more suited for?
- use both aerobic and anaerobic metabolism
- for prolonged mod. intensity work
e. g. jogging
Which activities are Type IIx muscle fibres more suited for?
- fast twitch
- anaerobic metabolism
- for short-term high intensity activities e.g. jumping
Which 3 investigations can be used to detect neuromuscular disease?
Electromyography (EMG)
Nerve conduction studies
Muscle enzyme checks e.g CK
Name 3 types of joints. Examples?
Synovial e.g. knee
Fibrous e.g. between skull bones
Cartilaginous e.g. between vertebrae
What is the synovial membrane?
Vascular connective tissue with lymphatics
- contains fibroblasts which produce the fluid
What are the 2 types of synovial joints?
Simple: one pair of articular surfaces
Compound: more than one pair
Name 3 extra-articular structures of the synovial joint which contributes to support
Ligaments
Tendons
Bursae
Give features of synovial fluid
High viscocity because of mucin
Clear and transparent
Replenished and absorbed by cells of the synovial membrane
