Skeletal muscle (nerve control) Flashcards
What are the events that happen at the postsynaptic membrane?
-local potential causes a wave of depolarisation
-this activates the Na+ channels to open and AP occurs
-AP ends when K+ channels open
Which direction does the wave of excitation travel?
In all directions across the muscle cell plasma membrane.
What is the order of structure of a muscle?
muscle, fascicle, muscle fibre, myofibrils.
What is the sarcoplasmic reticulum?
This is smooth endoplasmic reticulum used for contraction of muscle (storage of Ca2+ ions).
How does the AP cause muscle contraction?
AP wave travels down the T- tubule and since it changes the membrane potential, Ca2+ is released as the AP wave makes physical contact with the voltage- sensitive protein.
The Ca2+ concentration increase causes activation of contractile machinery.
What happens within the sarcomere during contraction?
The Z lines are brought closer together.
What is the purpose of titin?
This is used for muscle recoil and the stabilisation of the structure.
What is the purpose of the contractions of the sarcomere?
Allows the muscle to work.
What are the two myofibrils used for muscle contraction?
Actin and myosin.
What is the purpose of troponin?
This senses the Ca2+ increase.
What is the purpose of tropomyosin?
This exposes the myosin binding sites when Ca2+ is high.
What is the process of the interaction of actin and myosin?
-ATP binds to the myosin head the myosin head releases from actin
-the myosin head then latches onto the next binding site further back on the actin chain
-ATP then binds again and myosin head binds further back- shortening the muscle
What is a motor unit?
composed of a motor neuron and muscle fibres (causes contraction).
What is contraction controlled by?
The amount of motor units activated (lots of motor units activated= max contraction, flexing finger= few motor units excited).
How much contraction causes tetanus?
Maximum contraction (max activation of motor units)
How would you improve the smoothness of motor actions?
-frequency coding
-recruit motor units with larger and larger cells
-recruit more and more motor units
What happens to the muscles during rigor mortis?
-ATP synthesis stops
-SR Ca2+ pumps stop
-actin is activated
-no ATP available to detach myosin head from actin
-muscles stiffen
What is sarcopenia?
This is the loss of muscle and a result of ageing.
What are the contributing factors to sarcopenia?
-myosin production
-mitochondrial malfunction
-motor axon atrophy
-atrophy of muscle fibres (dont use the muscle, then lose it and becomes smaller).
Meaning of ipsilateral?
Same side of the body.
Meaning of contralateral?
Opposite side of the body.
What are the five components of a reflex arc?
-receptor
-sensory neuron
-integration centre
-motor neuron
-effector
Where is the integration centre?
The grey matter in the spinal cord.
