Flashcards in Physiology Deck (165)
What is a motor unit?
the alpha motor neuron and all the skeletal muscle fibres it innervates
if the alpha motor neurone supplies an area with fine motor control, will they have many or few muscle fibres?
if the alpha motor neurone supplies an area with muscles needed for force, will they have many or few muscle fibres?
what is the functional unit of a muscle?
compare cardiac muscle and skeletal muscle in terms of gap junctions?
cardiac muscles have gap junction (so AP can spread)
skeletal muscles don't have gap junctions
compare cardiac muscle and skeletal muscle in terms of neuromuscular junctions?
cardiac muscle does not contain neuromuscular junctions
skeletal muscle contains neuromuscular junctions
when is skeletal muscle at optimum length?
when is cardiac muscle at optimum length?
compare cardiac muscle and skeletal muscle in terms of initiation and propagation of contraction?
cardiac muscle- myogenic (pacemaker potential)
skeletal muscle- neurogenic
compare cardiac muscle and skeletal muscle in terms of Ca++ input?
cardiac muscle- Ca++ from ECF and sarcoplasmic reticulum
skeletal muscle- Ca++ entirely from sarcoplasmic reticulum
in skeletal muscle fibres, when is Ca++ released from lateral sacs of the sarcoplasmic reticulum?
when surface action potential spreads down the T tubules
what are T tubules?
extensions of the surface membrane that dip into the muscle fibre
what is the transmitter at the neuromuscular junction?
what is a myofibril?
made of lots of sarcomeres aligned head to tail
how far do skeletal muscle fibres (cells) usualy extend?
the entire length of the muscle
how are skeletal muscles attached to the skeleton?
how are myofibrils positioned within a cell?
parallel to each other
what lines form the borders of the sarcomere?
what is an A band?
the area of myosin
(with or without overlapping actin)
what is an I band?
the area of actin without any overlapping myosin
what is a H zone?
the area of myosin without any overlapping actin
what is the M line?
extends vertially down the middle of the A band within the centre of the H zone
what is required for both contraction and relaxation?
what is required to switch on cross bridge formation between actin and myosin?
How does Ca++ switch on cross bridge formation between actin and myosin?
by binding to troponin, this results in a conformational change of troponin-tropomyocin complex which uncovers the cross bridge binding sites on actin
Give 2 reasons why ATP is needed during muscle relaxation?
1. to release cross bridges
2. to pump Ca2++ back into sarcoplasmic reticulum
Give 1 reason why ATP is needed during muscle contraction?
1. to power cross bridges
What does the gradation of skeletal muscle tension depend on?
the tension developed by each contracting muscle fibre
the number of muscle fibres contracting within the muscle
What is motor unit recruitement?
stimulation of more motor units in order to get a stronger contraction