muscular and skeletal systems Flashcards
Which muscle types are striated
skeletal and cardiac
tendons
attaches muscle to bone
flexing and extending of skeletal muscle
flexing -reducing angle of joint
extending -increasing angle of joint
origin and insertion of skeletal muscle
origin - where muscle attaches
insertion - where muscle attaches on the bone more distant from the center of the body
fascicles
bundles that allow flexibility within the muscle
How many nerves innervate skeletal muscle
skeletal muscle is innervated by a single nerve ending
sarcolemma
cell membrane of myofiber
actin and myosin function
proteins in the myofibril (smallest unit of skeletal muscle)
actin forms thin filaments and myosin forms thick filaments
They overlap in sarcomeres
What occurs during contraction
thin and thick filaments slide across each other, drawing the Z lines of each sarcomere closer together and shortening the length of the muscle cell
myosin function in movement
enzyme that uses ATP energy to create movement, contains a head and tail
contractile cycle steps
- binding of myosin head to myosin binding site on actin. Myosin has ADP and P bound at this point
- power stroke, myosin head moves to low energy conformation and pulls actin chain towards center of sarcomere, releasing ADP
- binding of new ATP molecule necessary for release of actin by myosin head
- ATP hydrolysis occurs and myosin head is set in high energy conformation (cocked)
troponin tropomyosin complex
part of thin filament, prevents contraction when Ca2+ isn’t present
troponin is bound to tropomyosin and can bind Ca2+, causing myosin heads to be able to attach to actin, since tropomyosin is moved out of the way
neuromuscular junction
synapse between an axon terminus and a myofiber
What occurs when ACh binds to its receptor?
A postsynaptic sodium influx causing depolarization, which leads to an end plate potential.
What is required for contraction to occur in the myofibril
Action potential has to depolarize the entire myofiber
transverse tubules
allow action potential to travel in to thick myofibers.
sarcoplasmic reticulum
membrane in the myofiber that releases Ca2+ upon depolarization
How does the nervous system increase force of contraction
motor unit recruitment and frequency summation
length tension relationship
a muscle contracts most forcefully at an optimum length
creatine phosphate function
intermediate term energy storage molecule thats hydrolysis drives regeneration of ATP from ADP + P
myoglobin
provides an oxygen reserve by taking O2 from hemoglobin and then releasing it as needed
cause of rigor mortis
myosin heads are unable to release actin without ATP and the muscle can neither contract nor relax
slow twitch vs fast twitch muscle
slow twitch have a slow speed of contraction and many mitochondria, are very resistant to fatigue
fast twitch includes two types, IIA and IIB. IIB is known as white fast twitch and has very fast contraction, very few mitochondria, and has low fatigue resistance.
how is cardiac muscle similar to skeletal muscle
- thick and thin filaments are organized into sarcomeres, so both cardiac and skeletal muscle are striated
- t tubules are present and serve the same function
- troponin tropomyosin regulates contraction in the same way
- length tension relationship works the same way and is more significant in cardiac muscle