muscles Flashcards
description of voluntary skeletal muscle
- cell membrane consists of sarcolemma
- cytoplasm is sarcoplasm
- many mitochondria
- many myofibrils
description of the cardiac muscle
- branches fibres with cross bridges
- cells separated by intercalated discs
- good network of capillaries
- more reliant on aerobic respiration
- many mitochondria
description of involuntary smooth muscle
- contains actin and myosin
- many mitochondria
- looks like a broken egg yolk
what is the appearance of skeletal muscle under microscope
striated (due to actin and myosin)
what is the appearance of cardiac muscle under microscope
striated (due to myofibrils)
what is the contract speed of smooth muscles
slow and sustained
what is the appearance of smooth muscle under microscope
unstriated (no myofibrils)
fatigue in skeletal muscle
fatigues quickly
fatigue in cardiac muscle
does not fatigue (due to lots of mitochondria)
fatigue in smooth muscle
slow (does not tire easily)
function of skeletal muscle
contraction shortens muscle for a reflex (involuntary response)
function of cardiac muscle
contracts to decrease volume in heart to pump blood into ventricles or out of heart via arteries
function of smooth muscle
intestine walls - peristalsis
OR regulated blood pressure eg. exercise and temp regulation
what are myofibrils surrounded by?
sarcoplasmic reticulum which stores and secretes calcium
function of t-tubules?
infoldings of sarcolemma which allow action potentials to spread electrical impulses across sarcoplasm
if you took a cross section of A band, what would you see?
action and myosin overlap
if you took a cross section of H zone, what would you see?
myosin only
if you took a cross section of I band, what would you see?
actin only
what does calcium bind to?
troponin
what does the binding of calcium to troponin cause?
troponin changes shape and causes tropomyosin to move away from myosin binding site = myosin head can now bind
how is there conformational change in muscle contraction?
tilts from 90 degrees to 45 degrees which forces actin to move in relation to the myosin. ADP and Pi are released
what is the condition causing the stiffening of muscles when ATP runs out?
rigor mortis (filaments become locked in position)
myosin hydrolyses…
ATP into ADP and Pi, creating energy to release myosin head away from actin returning to original 90 degree position.
how is the muscle shorten in simple terms
when the heads bend actin and myosin filaments move past each other so muscle shortens.
