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Chapter 6: Muscles

What are the four major functional characteristics of the skeletal muscles? Contractility, Excitability, Extensibility, and Elasticity.
The ability of skeletal muscle to shorten with force is... Contractility.
The capacity of skeletal muscle to respond to a stimulus is... Excitability.
The ability to be stretched is... Extensibility.
The ability to recoil to their original resting length after they have been stretched... Elasticity.
What do muscles do? Muscles help produce heat essential for maintenance of normal body temperature.
Each skeletal muscle is surrounded by a connective tissue sheath called the what? Epimysium.
What is another connective tissue located outside the epimysium that surrounds and separates muscles? Fascia.
What are the numerous visible bundles that compose muscle? What loose connective tissue are they surrounded by? Fasciculi, and they are surrounded by the perimysium.
What are the single muscle cells that fasciculi composed of? Fibers.
What is each muscle fiber? A single cylindrical cell containing several nuclei.
Each muscle fiber is surrounded by a connective tissue sheath called the what? Endomysium.
The cytoplasm of each fiber is filled with what? Myofibrils.
What are myofibrils? A threadlike structure that extends from one end of the fiber to the other.
What 2 major kind of protein fibers do myofibrils consist of? Actin myofilaments and myosin myofilaments.
What are actin myofilaments? Thin myofilaments, that resemble two strands of pearls twisted together.
What are myosin myofilaments? Thick myofilaments, that resemble bundles of minute golf clubs.
Actin and myosin myofilaments form highly ordered units called... Sarcomeres, which are joined end to end to form the myofibril.
What is the sarcomere? It is the basic structural and functional unity of the muscle.
Each sarcomere extends from what to what? From one Z line disc to another Z line disc.
Each Z line is an attachment site for what? Actin.
What gives a banded appearance? The arrangement of actin and myosin.
On each side of the Z line is a light area called the what? What does it consist of? The I band, and it consists of actin.
The A band... Extends the length of the myosin, and is the darker central region in each sarcomere.
In the center of each sarcomere is another light area called... The H zone, which consists of only myosin.
The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the what? The M line.
The inside of the cell membrane is charged how? Negatively.
The outside of the cell membrane is charged how? Positively.
The charge difference across the membrane is called the... Resting membrane potential.
The brief reversal back of the charge is called the... Action potential.
What are nerve cells that carry action potentials to skeletal muscle fibers? Motor neurons.
Each branch that connects to the muscle forms a what? Near what? Neuromuscular junction, or synapse, near the center of the cell.
What is a single motor neuron and all the skeletal muscle fibers it innervates called? A motor unit.
What do many motor units form? A single muscle.
How is a neuromuscular junction formed? By an enlarged nerve terminal resting in an indentation of the muscle cell membrane.
What is the enlarged nerve terminal? Presynaptic terminal.
What is the space between the presynaptic terminal and the muscle cell? The synaptic cleft.
What is the muscle fiber? The postsynaptic terminal.
Each presynaptic terminal contains what, and what do they secrete? Synaptic vesicles that secrete a neurotransmitter called acetylcholine.
The acetylcholine released into the synaptic cleft between the neuron and the muscle cell is rapidly broken down by an enzyme called what? Acetylcholinesterase.
Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten. When the sarcomeres shorten, it causes the muscle to shorten. Muscle contraction.
The sliding of actin myofilaments past myosin myofilaments during contraction is called what? During this, the H and I bands shorten, but the A bands do not change in length. The sliding filament mechanism.
What is 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 a stimulus until... Threshold, or when the muscle fiber will contract maximally. This is also called the all-or-none response.
The time between application of a stimulus to a motor neuron and the beginning of a contraction is the what? Lag phase.
The time of contraction is... Contraction phase.
The time in which the muscle relaxes is the... Relaxation phase.
Where the muscle remains contracted without relaxing is called... Tetany.
The increase in the number of motor units being activated is called what? Recruitment.
What is needed for energy for muscle contraction? ATP (Adenosine Triphosphate).
Where is ATP produced? In the mitochondria.
ATP is... Short lived and unstable, and degenerates to the more stable ADP (Adenosine Diphosphate) plus phosphate.
Anaerobic respiration... Without oxygen.
Aerobic respiration... With oxygen (more efficient).
The oxygen debit is what? The amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells.
What results when ATP is used during muscle contraction faster than it can be produced in the muscle cells? Muscle fatigue.
What are the 2 types of muscle contractions? Isometric (equal distance) and Isotonic (equal tension).
The length of the muscle does not change, but the amount of tension increases during the contraction process? Isometric.
The amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes? Isotonic.
Refers to constant tension produced by muscles of the body for long periods of time, and keeps the head up and the back straight... Muscle tone.
What contracts quickly and fatigues quickly, and is well adapted to perform anaerobic metabolism (ex. white meat)? Fast twitch fibers.
What contracts more slowly and is more resistant to fatigue, and is better suited for aerobic metabolism (ex. dark meat)? Slow twitch fibers.
The points of attachments of each muscle are its... Origin and insertion.
At these attachment points the muscle is connected to a bone by a what? Tendon.
What is the most stationary end of the muscle? The origin (head).
What is the end of the muscle undergoing the greatest movement? The insertion.
What is the portion of the muscle between the origin and insertion? The belly.
Some muscles have multiple... Origin or head.
Muscles that work together to accomplish specific movements are called what? Synergists.
Muscles that work in opposition to one another are called what? Antagonists.
Among a group of synergists, if one muscle plays the major role in accomplishing the desired movement, it is the what? Prime mover.
Most muscles have names that are... Descriptive.
Some are named according to their what? Location, size, orientation of fibers, shape, origin, insertion, and function.
Created by: jessicamitchell



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