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.
