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Ch.6 Notes

Eastham- Anatomy

4 major functional characteristics of skeletal muscle contractility, excitability, extensibility, elasticity
contractility ability to shorten with force
excitability ability to respond to a stimulus
extensibility ability to be stretched
elasticity ability to recoil to the original shape
muscles help to produce... heat
epimysium connective tissue sheath that surrounds skeletal muscle
fascia surrounds and separates muscles, located outside of the epimysium
muscle fasciculi or fascicle visible bundles that make a muscle
perimysium surrounds muscle fasciculi/fasicle
fasciculi are composed of... single muscle cells
single muscle cells muscle fibers
muscle fiber a cylindrical cell containing several nuclei
endomysium surrounds each muscle fiber
myofibrils fills the cytoplasm of each fiber, a threadlike structure that extends from one end of the fiber to the other
2 major kinds of protein fibers in myofibrils actin myofilaments and myosin myofilaments
actin myofilaments thin, resemble 2 minute strands of twisted pearls
myosin myofilaments thick, resemble bundles of minute golf clubs
acftin and myosin myofilaments form... highly ordered units called sarcomeres
sarcomere joined end to end to form the myofibril, the basic structural and functional unity of the muscle
each sarcomere extends from.... one Z line to another Z line
attachment site for actin Z line
each side of the Z line light colored area called an I band, consists of actin
extends the length of the myosin and the darker central region in each sarcomere A band
center of each sarcomere another light colored area called the H zone, consists of only myosin
myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called... M line
outside of most cell membranes is... positively charged
inside of the cell membrane is... negatively charged
the charge difference across the membrane is... the resting membrane potential
brief reversal back of the charge is... action potential
nerve cells that carry action potentials to skeletal muscle fibers motor neurons
axons enter... the muscles and branch
each branch that connects to the muscle forms... neuromuscular junction, or synapse near the center of the cell
single motor neuron and all skeletal muscle fibers it innervates motor unit
many motor units form... a single muscle
formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane neuromuscular junction
presynaptic terminal enlarged nerve terminal
synaptic cleft space between the presynaptic terminal and the muscle cell
postsynaptic terminal the muscle fiber
each presynaptic terminal contains... synaptic vesicles
synaptic vesicles secrete a neurotransmitter called... acetylcholine
the function of acetylcholine it diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell
when an action potential reaches the nerve terminal, it causes... the synaptic vesicles to release acetylcholine into the synaptic cleft by exocytosis
the acetylcholine diffuses across... and binds to... in the muscle cell membrane (sarcolemma) the synaptic cleft, receptor molecules
combination of acetylcholine with its receptors causes... an influx of sodium ions into the muscle fiber
influx causes an action potential in the muscle cell which causes... the muscle to contract
enzymes that rapidly break down the acetylcholine released into the synaptic cleft between the neuron and muscle cell acetylcholinesterase
occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten muscle contraction
when sarcomeres shorten it causes the muscle to... shorten
the sliding of actin myofilaments past myosin myofilaments during contraction is called... sliding filament mechanism; the H and I bands shorten, but the A bands do not change in length
a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers muscle twitch
a muscle fiber will not respond to stimulus until that stimulus reaches a level called... a threshold, at which point the muscle fiber will contract maximally
fibers responding to stimulus at the threshold level and contracting maximally is a phenomenon called... all-or-none response
time between application of a stimulus to a motor neuron and the beginning of a contraction lag phase
time of contraction contraction phase
time during which the muscle relaxes relaxation phase
when the muscle remains contracted without relaxing tetany
the increase in number of motor units being activated recruitment
needed for energy for muscle contraction ATP (adenosine triphosphate)
produced in the mitochondria, short-lived, and unstable ATP (adenosine triphosphate)
ATP degenerates to the more stable... ADP (adenosine diphosphate) plus phosphate
when muscles rest, they can't stockpile ATP but they can store another high-energy molecule... creatine phosphate
without oxygen anaerobic respiration (weight-lifting, sprinting, jumping)
with oxygen (more efficient) aerobic respiration (running, swimming, hiking, dancing)
the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores to creatine phosphate stores in muscle cells... oxygen debt
when ATP is used during muscle contraction faster than it can be produced in the muscle cells muscle fatigue
2 types of muscle contractions isometric and isotonic
equal distance contraction isometric
equal tension contraction isotonic
refers to constant tension produced by muscles of the body for long periods of time, keeps heads up and backs straight muscle tone
contracts quickly and fatigues quickly (white meat) fast-twitch fibers
contracts more slowly and are more resistant to fatigue (dark meat) slow-twitch fibers
most stationary end of the muscle (head) origin
end of the muscle undergoing the greatest movement insertion
portion of muscle between origin and insertion belly
muscles that work together synergists
muscles that work in opposition antagonists
one muscle playing the major role in accomplishing desired movement among a group of synergists prime mover
muscle names are... descriptive
muscles are named according to... location, size, orientation of fibers, shape, origin, insertion, and function, etc.
Created by: Mirandachaffins