Chapter 8 Review

the perimysium

surrounds individual bundles (fascicles) within each muscle

summation

A muscle fiber receiving a series of stimuli of increasing frequency reaches a point when it is unable to relax completely and the force of individual twitches combine by the process of summation.

sarcoplasm (cytoplasm)

Beneath the sarcolemma (cell membrane) lies sarcoplasm (cytoplasm) with many mitochondria and nuclei

sarcoplasmic reticulum (endoplasmic reticulum)

Beneath the sarcolemma of a muscle fiber lies the sarcoplasmic reticulum (endoplasmic reticulum), which is associated with transverse (T) tubules (invaginations of the sarcolemma).

intercalated discs

Complex membrane junctions, called intercalated discs, join cells and transmit the force of contraction from one cell to the next, as well as aid in the rapid transmission of impulses throughout the heart

sarcoplasmic reticulum

Each T tubule lies between two cisternae of the sarcoplasmic reticulum and is open to the outside of the muscle fiber.

synapse

Each skeletal muscle fiber (cell) is functionally (not physically) connected to the axon of a motor neuron, creating a synapse.

ADP

Energy from the conversion of ATP to ADP is provided to the cross-bridges from the enzyme ATPase, causing them to be in a "cocked" position.

fascia

Layers of dense connective tissue, called fascia, surround and separate each muscle

Pyruvic acid

Oxygen deficiency may develop during strenuous exercise. Pyruvic acid forms, then reacts to form lactic acid which accumulates as an end product of anaerobic respiration in the form of lactate

aponeuroses

Sometimes muscles are connected to each other by broad sheets of connective tissue called aponeuroses.

sustained contraction

Summation and recruitment together can produce a sustained contraction of increasing strength.

neurotransmitters

The cytoplasm of the motor neuron contains numerous mitochondria and synaptic vesicles storing neurotransmitters. When an electrical impulse reaches the end of the motor neuron axon, vesicles release neurotransmitter into the synaptic cleft and will stimulate the muscle fiber to contract.

origin

The immovable end of a muscle is the origin

acetylcholine

The motor neuron must release the neurotransmitter acetylcholine from its synaptic vesicles into the synaptic cleft in order to initiate a muscle contraction

motor end plate

The muscle fiber membrane forms a motor end plate in which the sarcolemma is tightly folded and where nuclei and mitochondria are abundant.

neuromuscular junction

The neuron communicates with the muscle fiber by way of neurotransmitters released at the synapse.

striations

The organization of these myofibrils produces striations

myoglobin

The pigment myoglobin stores oxygen in muscle tissue

twitch

The response of a single muscle fiber to a single impulse is referred to as a twitch.

motor neuron

The site where the motor neuron and muscle fiber meet is the neuromuscular junction.

myosin2

Thick filaments of myofibrils are made up of the protein myosin.

actin

Thin filaments of myofibrils are mainly composed of the protein actin, along with troponin and tropomyosin.

fatigue.

When a muscle loses its ability to contract during strenuous exercise

sliding filament model

a myosin head cross-bridge attaches to a binding site on the actin filament and bends, pulling on the actin filament; it then releases and attaches to the next binding site on the actin, pulling again.

The sarcoplasmic reticulum and transverse tubules

activate the muscle contraction mechanism when the fiber is stimulated.

peristalsis

and are thus responsible for peristalsis in hollow organs and tubes.

A motor neuron

and the muscle fibers it controls make up a motor unit; when stimulated to do so, the muscle fibers of the motor unit contract all at once.

antagonists.

are Opposing muscles

tropomyosin and troponine

are two proteins associated with the surface of the actin filaments.

Cardiac muscle

consists of branching, striated cells that interconnect in three-dimensional networks

Myosin

consists of two twisted strands with globular heads projected outward along the strands.

The sarcoplasm

contains parallel myofibrils.

insertion

contraction pulls the insertion toward the origin.

Hemoglobin

in red blood cells carries oxygen to muscle.

A latent period

is a brief delay between the stimulation and beginning of the contraction

Actin

is a globular protein put together in twisted filaments, with myosin binding sites

Muscle tone

is achieved by a continuous state of sustained contraction of a few motor units within a muscle.

recruitment

is an increase in the number of activated motor units within a muscle at higher intensities of stimulation

tetanic contraction.

is if the sustained contraction lacks any relaxation

agonist (prime mover)

is of a group of muscles, the one doing the majority of the work .

Smooth muscle

is slower to contract and relax than is skeletal muscle, but can contract longer using the same amount of ATP.

epimysium

is the layer of connective tissue around each whole muscle

Visceral smooth muscle

occurs in sheets and is found in the walls of hollow organs

Oxygen debt

refers to the amount of oxygen that liver cells require to convert the accumulated lactate back into glucose, plus the amount that muscle cells need to resynthesize ATP and creatine phosphate to their original concentrations

Both acetylcholine and norepinephrine

stimulate and inhibit smooth muscle contraction, depending on the target muscle.

In multiunit smooth muscle

such as in the blood vessels and iris of the eye, fibers occur separately rather than as sheets.

Threshold Stimulus

the minimum stimulus required to generate a impulse through the muscle, release calcium ions, activate cross-bridges, and contract the muscle

rhythmicity

these fibers can stimulate one another and display rhythmicity

Creatine phosphate

which stores excess energy released by the mitochondria, is present to regenerate ATP from ADP and phosphate.