Chapter 39: Motor Mechanisms and Behaviours Flashcards
what is muscle activity a response to?
input from the nervous system
is muscle contraction a passive or active process?
active
is muscle relaxation a passive or active process?
passive
what is a vertebrate skeletal muscle?
moves bones and the body and is characterized by a hierarchy of smaller and smaller units
what does a skeletal muscle consist of?
a bundle of long fibers, each a single cell, running parallel to the length of a muscle
what is each muscle fiber made of?
bundle of smaller myofibrils
what did myofibrils contain?
thick and thin filaments
what is the skeletal muscle also called? why?
striated muscle because the regular arrangement of myofibrils creates a pattern of light and dark bands
what is the functional unit of a muscle?
a sarcomere. it is bordered by Z-lines (any of the dark thin bands across a striated muscle fiber that mark the junction of actin filaments in adjacent sarcomeres)
what does muscle contraction rely on?
interactions between protein structures
what do the thin filaments consist of?
2 strands of actin
what do thick filaments consist of?
staggered arrays of myosin molecules
what are filaments?
proteins that cause movement (motor proteins)
what is the model called that explains how muscles contract?
sliding-filament model
what does the sliding-filament model say?
filaments slide past each other longitudinally, causing an overlap between thin and thick filaments. the head of a myosin molecule binds to an actin filament, forming a cross bridge, and pulling the thin filament toward the centre of the sarcomere (Z-line comes closer)
what is the sliding of filaments reliant on?
interactions between actin and myosin
what do muscle contractions require?
repeated cycles of binding and release
how is the ATP needed to sustain muscle contraction made?
glycolysis and aerobic respiration
does the filament ever change shape?
no, only the closeness of the Z-lines
what binds to actin stands when the fiber is at rest?
tropomyosin and troponin complex
what are tropomyosin and troponin complex
additional proteins that bind to actin stands when a muscle fiber is at rest
what must happen to the myosin binding sites before it can be contracted?
it must be uncovered
how are the myosin binding sites exposed?
Ca 2+ bind to the troponin complex. this moves the troponin and the tropomyosin.
what needs to be present for a contraction to occur?
high concentration of Ca 2+
when does a muscle stop contracting?
when there is a low concentration of Ca 2+
where does Ca 2+ come from?
it is controlled by the brain
what makes actin and myosin unbind?
ATP
what are graded contractions?
the extent and strength of contraction can be voluntarily altered
what mechanisms does the nervous system use to produce graded contractions?
varying the number of fibers that contract. varying the rate at which fibers are stimulated.
what does a motor unit consist of?
a single motor neuron and the muscle fibers it controls
what send a message to the muscle to contract?
multiple neurons
what is action potential?
sudden, fast, transitory, and propagating change of the resting membrane potential. property called excitability.
what does the recruitment of multiple motor neurons result in?
stronger contracts. this allows for a variation in contraction strength
what is a twitch a result of?
a single action potential in a motor neuron
what is tetanus?
is a state of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials
what are the types of skeletal muscle fibers?
slow oxidative, fast oxidative, and fast glycolytic
what is the contraction speed in slow oxidative?
slow
what is the contraction speed in fast oxidative?
fast
what is the contraction speed in fast glycolytic?
fast
what is the major ATP source in slow oxidative?
aerobic respiration
what is the major ATP source in fast oxidative?
aerobic respiration
what is the major ATP source in fast glycolytic?
glycolysis
what is the rate of fatigue for slow oxidative?
slow
what is the rate of fatigue for fast oxidative?
intermediate
what is the rate of fatigue for fast glycolytic?
fast
how many mitochondria in slow oxidative?
many
how many mitochondria in fast oxidative?
many
how many mitochondria in fast glycolytic?
few
what is the myoglobin content in slow oxidative?
high (red muscle)
what is the myoglobin content in fast oxidative?
high (red muscle)
what is the myoglobin content in fast glycolytic?
low (white muscle)
how do oxidative and glycolytic fibers differentiate?
what their energy source is
what is myoglobin?
a protein that binds O2 more tightly than hemoglobin does
how does fast twitch and slow twitch fibers differ?
their speed of contraction
what is a slow twitch fiber?
they contract more slowly but sustain longer contractions. all slow-twitch fibers are oxidative
what is a fast twitch fiber?
they contract more rapidly but sustain shorter contractions. fast twitch fibers can be either oxidative or glycolytic
what are characteristics of the cardiac muscle?
found only in the heart. consists of striated cells and Z-lines. striated cells are electrically connected by intercalated discs. they are involuntary. cardiac muscle gain can generate action potentials without neural input
what are intercalated discs?
found between myocardial cells of the heart. help bond muscle cells together and transmit signals between cells
what are characteristics of smooth muscle?
found mainly in the walls of hollow organs such as those of the digestive tract. not striated. contractions are relatively slow. contractions may be initiated by the muscle itself without the brain. involuntary. contractions may also be caused by a stimulation from neurons in the autonomic nervous system
what are skeletal muscles attached in?
antagonistic pairs
what happens if one muscle in the pair contracts?
the other relaxes
what does the skeleton do?
provides a rigid structure to which muscles attach. helps with support, protection, and movement
