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Ch.6 Notes
Eastham- Anatomy
| Question | Answer |
|---|---|
| 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
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