BIO 360 - Exam 3 - Chapter 12 Summary Questions Flashcards
______ generate motion, force, and heat.
Muscles
The three types of muscle are:
skeletal muscle, cardiac muscle, and smooth muscle. Skeletal and cardiac muscles are striated muscles.
Skeletal muscles are controlled by ______ ______ neurons. Cardiac and smooth muscle are controlled by a_____ i______, p______ s______, and h______.
Some smooth and cardiac muscles are ______ and contract spontaneously.
somatic motor / autonomic innervation, paracrine signals, and hormones / auto-rhythmic
Skeletal muscles are usually attached to bones by tendons. The ______ is the end of the muscle attached closest to the trunk or to the more stationary bone. The ______ is the more distal or mobile attachment.
origin / insertion
At a flexible joint, muscle contraction moves the skeleton. ______ bring bones closer together; ______ move bones away from each other. Flexor-extensor pairs are examples of ______ muscle groups.
Flexors / extensors / antagonistic
A skeletal muscle is a collection of ______ ______, large cells with many nuclei.
muscle fibers
______ allow action potentials to move rapidly into the interior of the fiber and release calcium from the s______ r______.
T-tubules / sarcoplasmic reticulum
______ are intracellular bundles of contractile and elastic proteins. ______ filaments are made of ______. ______ filaments are made mostly of ______. _____ and ______ hold thick and thin filaments in position.
Myofibrils / Thick filaments / myosin / Thin filaments / actin / Titan / nebulin
Myosin binds to actin, creating ______ between the thick and thin filaments.
crossbridges
A ______ is the contractile unit of a myofibril. It is composed of two ______ and the filaments between them. The sarcomere is divided into ______ (thin filaments only), an ______ that runs the length of a thick filament, and a central ______ occupied by thick filaments only. The ______ and Z disks represent attachment sites for myosin and actin, respectively.
sarcomere / Z disks / I bands / A band / H zone / M line
The force created by a contracting muscle is called ______ ______. The ______ is a weight or force that opposes contraction of a muscle.
muscle tension / load
The _________________________________ states that during contraction, overlapping thick and thin filaments slide past each other in an energy-dependent manner as a result of actin-myosin crossbridge movement.
sliding filament theory of contraction
In relaxed muscle, ______ partially blocks the myosin-binding site on actin. To initiate contraction, ______ binds to ______. This unblocks the myosin-binding sites and allows myosin to complete its power stroke.
tropomyosin / Ca2+ / troponin
During relaxation, the sarcoplasmic reticulum uses a ________
to pump _______ back into its lumen.
Ca2+ - ATPase / Ca2+
Myosin converts energy from ATP into motion. ______ ______ hydrolyzes ATP to ADP and ______.
Myosin ATPase / Pi
When myosin releases ______ the myosin head moves in the ______ ______. At the end of the power stroke, myosin releases ADP. The cycle ends in the ______ ______, with myosin tightly bound to actin.
Pi / power stroke / rigor state
In ______ - ______ ______, a somatic motor neuron releases ACh, which initiates a skeletal muscle action potential that leads to contraction.
excitation-contraction coupling
Relaxation occurs when ______ is pumped back into the SR by a ______.
Ca2+ / Ca2+-ATPase
A single contraction-relaxation cycle is known as a ______. The ______ ______ between the end of the muscle action potential and the beginning of muscle tension development represents the time required for Ca2+ release and binding to troponin.
twitch / latent period
Muscle fibers store energy for contraction in ______ . Anaerobic metabolism of glucose is a rapid source of ATP but is not efficient. Aerobic metabolism is very efficient but requires an adequate supply of oxygen to the muscles.
phosphocreatine
______ ______is a reversible condition in which a muscle is no longer able to generate or sustain the expected power output. Fatigue has multiple causes.
Muscle fatigue
Skeletal muscle fibers can be classified on the basis of their speed of contraction and resistance to fatigue into?
Oxidative fibers are the most fatigue resistant.
slow-twitch (oxidative) fibers, fast-twitch oxidative-glycolytic fibers, and fast-twitch glycolytic fibers.
______ is an oxygen-binding pigment that transfers oxygen to the interior of the muscle fiber.
Myoglobin
The tension of a skeletal muscle contraction is determined by the ______ of the ______ before contraction begins.
length / sarcomeres
Increasing the stimulus frequency causes summation of twitches with an increase of tension. A state of maximal contraction is known as ______.
tetanus
A ______ ______ is composed of a group of muscle fibers and the somatic motor neuron that controls them. The number of muscle fibers in a motor unit varies, but all fibers in a single motor unit are of the same fiber type.
motor unit
The force of contraction within a skeletal muscle can be increased by ______ of additional motor units.
recruitment
An ______ contraction creates force as the muscle shortens and moves a load. An ______ contraction creates force without moving a load. Lengthening contractions create force while the muscle lengthens.
isotonic / isometric
Isometric contractions occur because s______ e______ e______ allow the fibers to maintain constant length even though the sarcomeres are shortening and creating tension.
series elastic elements
The body uses its bones and joints as ______ and ______. Most lever-fulcrum systems in the body maximize the distance and speed that a load can be moved but also require that muscles do more work than they would without the lever.
levers and fulcrums
Contraction speed is a function of muscle fiber type and load. Contraction is fastest when the load on the muscle is ______.
zero
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______ muscle is slower than ______ muscle but can sustain contractions for longer without fatiguing.
Smooth / skeletal
______ muscles are usually relaxed or cycle through contractions. ______ ______ muscle is usually contracted.
Phasic / Tonic smooth
______-______ ______muscle contracts as a single unit when depolarizations pass from cell to cell through gap junctions.
In ______ ______ muscle, individual muscle fibers are stimulated independently.
Single-unit smooth / multiunit smooth
Smooth muscle has less ______ than skeletal muscle. Each myosin is associated with about 12–15 actin molecules. Smooth muscle actin lacks ______.
myosin / troponin
In smooth muscle contraction, ______ binds to ______ and activates myosin light chain kinase (MLCK).
Ca2+ / calmodulin
MLCK phosphorylates ______ ______ ______, which activates myosin ATPase. This allows crossbridge power strokes.
myosin light chains
During relaxation, Ca2+ is pumped out of the cytosol, and myosin light chains are dephosphorylated by ______ ______ .
myosin phosphatase
Smooth muscle ______ ______ can be altered by changing myosin phosphatase activity.
calcium sensitivity
In ______ contraction, stretch on the cell depolarizes it and Ca2+ opens membrane channels.
myogenic
Unstable membrane potentials in smooth muscle take the form of either ______ ______ potentials or ______ potentials.
slow wave / pacemaker
Cardiac muscle fibers are what three things?
Cardiac muscle shares features with both ______ and ______ muscle.
(1) striated
(2) have a single nucleus
(3) electrically linked through gap junctions.
skeletal and smooth muscle
