Physiology Flashcards
Explain what a motor unit is
A single alpha motor neuron and the muscle fibres that it innervates
What is a muscle fibre?
How big is it?
1 muscle cell
Typically the full length of the muscle
What is the neurotransmitter at the neuromuscular junction?
ACh
What 2 things are needed for muscle contraction?
Ca2+
ATP
Where does skeletal muscle get its Ca2+ from?
SR only
Ca2+ is released from lateral sacs as action potential spreads down transverse (T)-tubules
(look at diagram in notes)
Explain how rigor mortis takes place?
Muscles need ATP in order to contract and RELAX
Without ATP muscles continually seize
What is the smallest functional unit in skeletal muscle?
Sacromere
Functional unit = ability to carry out full function of cell
Draw and label a sacromere: A band H zone M line I band
A band - area of actin and myosin that overlaps
H zone - central area of myosin with no overlap of actin
I band - peripheral areas of actin with no myosin underneath
M line - central part of myosin
What has more muscle fibres per motor unit - intricate muscles or large powerful muscles?
Intricate muscles - fine movement requires more motor units per muscle fibres
What 2 things is the gradation of muscle contraction dependant on?
- No of motor units stimulated (motor unit recruitment)
- Summation of contractions + length of fibre
Explain how tetanus can become a thing in skeletal muscle
In skeletal muscle action potentials are much smaller than contractions
Hence multiple action potentials can occur and enable constant contraction of muscle
What prevents cardiac muscle from becoming tetanised?
Long refractory period
What is optimum length of muscle?
The optimum overlap of actin and myosin that allows for maximum tetanic tension
What are the 2 types of skeletal muscle contraction - describe them both?
Isotonic - length changes and tension stays the same
Isometric - length stays same and tension changes
Met = police = rising tension
How is muscle contraction in sarcomeres communicated to the bones of the body?
Via the elastic component of muscle e.g. tendons/connective tissue