Cardiac and Skeletal Muscle Flashcards
Features of skeletal muscle
multinucleated contains many mitochondria transverse tubules myofibrils and sarcomeres attached to bone voluntary
sarcolemma
plasma membrane
sarcoplasm
cytoplasm
sarcoplasmic reticulum
Smooth ER
What are myofibrils
structures that give the striated appearance, this results in the orderly arrangements of thick and thin filaments
Features of cardiac muscle
one - two nuclei centrally located
striated with intercalated discs
nodal cells have the ability to stimulate their own AP (Automaticity or auto-rhytmicity)
sliding filament mechanism
branching cells with desmosomes and gap junctions
Absolute refractory period of cardiac muscle
250 ms which prevents tetanic contractions
What does cardiac muscle depend on
intrinsic properties
hormones
autonomic nervous system
What makes up a gap junction
hexagonal array of protein subunits known as connexins
site of low electrical resistance between cells
acts as communicating channels - connexon
hole is 1.5 nm and small molecules can pass through (<500mw)
What makes up a motor unit
motor neuron and muscle fibres it innervates
Where are motor neurone cell bodies located
brain stem or the spinal cord
features of a motor neuron
myelinated and have largest diameter axons in the body
which allows propagation of AP at high velocities allowing signals from CNS to travel to skeletal muscles fibres with minimum delay
Myasthenia Gravis
muscle weakness that increases during periods of activity but improves with rest
due to auto-antibodies that target ACh receptors either destroying them or effecting the ability of ACh to bind
myositis
inflammation
Muscular Dystrophy
Inheritied disorders with progressive weakness
