Muscle Excitation/Constriction Flashcards
describe the structure of skeletal muscle
long cylindrical cells with many nuclei, rapid contractions, striated, voluntary (concious reflex)
describe the structure of cardiac muscle
branching cells with 1/2 nuclei, striated, involuntary, medium speed contractions
describe the structure of smooth muscle
fusiform cells with one nucleus, nonstriated, involuntary, slow wave-like contractions
explain how an electrochemical gradient can be created within cells
energy input (ATP) transporting ions across a membrane
what is the resting membrane potential?
the electrical gradient across the cell membrane
what is the resting membrane potential value in nerve/muscle cells?
-40 to -90 mV
how does potassium ion movement affect the cell?
if membrane permeable to K, it will leak out the cell down its conc. gradient, leaving the cell -ve charged
the -ve charge attracts K ions back into the cell down the electrical gradient
what is the equilibrium potential?
where electrical gradient opposes chemical gradient
describe the membrane permeability in relation to Na and K ions in real cells
much more permeable to K than Na, RMP around -70 mV
3 Na ions pumped out and 2 K ions pumped in
what is a motor unit?
all the muscle cells controlled by one nerve cell
give 3 examples of motor unit ratios
back muscles - 1:100
finger muscles - 1:10
eye muscles - 1:1
what is muscle tonus?
the tightness of a muscle
some fibers always contracted
what is muscle tetany?
involuntary sustained contraction of a muscle as a result of a rapid succession of nerve impulses
what is a muscles refractory period?
a brief period of time in which muscle cells will not respond to a stimulus
explain the formation of key proteins in the skeletal muscle
composed of thick myosin and thin actin filament, held together by titin filament
structures in bands along the sarcomere
why are Z lines important in sarcomeres?
contain titin filament, regulates the continual transducing of sarcomere length
describe a myosin molecule structure and its importance
2 molecules platted around with large myosin head
heads act as binding notches to bind to actin in different directions
describe the structure of an actin molecule and the function of the molecules
double stranded structure containing troponin complex, tropomyosin and G actin
tropomyosin is an inhibitory molecule preventing the binding of myosin and actin
explain how an action potential is generated during muscle contraction
nerve impulse reaches neuromuscular junction
acetylcholine released from motor neuron
ach binds to muscle membrane receptors to allow Na to enter
Na influx generates action potential in the sarcolemma
explain how an action potential results in actin filament binding site exposure
action potential travels doen T-tubule
sarcoplasmic reticulum releases calcium
calcium binds with troponin to move the troponin-tropomyosin complex
binding sites in the actin filament are exposed
explain the process of actin-myosin filament sliding to create a contraction
myosin head attaches to binding sites and create a power stroke
ATP detaches myosin heads and energises them for another contraction/stroke
when action potentials cease, the muscles stop contracting
what is muscle atrophy? and how is it caused?
weakening/shrinking of muscle (reduced muscle cell size)
could be caused by immobilisation, neural stimulation loss or other factors
what is muscle hypertrophy? and how is it caused?
muscle enlargement (more capillaries/mitochondria)
caused by strenuous exercise or steroid hormones
describe isometric contractions
produces no movement
used in standing, sitting, and maintaining posture
describe isotonic contractions
produces movement
used in walking and moving body parts
name each band/line/zone in the sarcomere and explain what it covers
H zone - area with only myosin
A band - all myosin
M line - runs down middle of sarcomere
I band - only actin
Z line - sarcomere boundary
