Human Physiology Chapter 9 (Vander's)

skeletal muscle

striated muscle attached to bone or skin and responsible for skeletal movements and facial expression; controlled by somatic nervous system

cardiac muscle

heart muscle

smooth muscle

nonstriated muscle that surrounds hollow organs and tubes; see also multiunit smooth muscle, single-unit smooth muscle

striated muscle

(STRY-ay-ted) muscle having transverse banding pattern due to repeating sarcomere structure; see also cardiac muscle, skeletal muscle

muscle fiber

muscle cell

muscle

number of muscle fibers bound together by connective tissue

tendon

(TEN-don) collagen fiber bundle that connects skeletal muscle to bone and transmits muscle contraction force to the bone

myofibril

(mye-oh-FY-bril) bundle of thick and thin contractile filaments in cytoplasm of striated muscle; myofibrils exhibit a repeating sarcomere pattern along longitudinal axis of muscle

sarcomere

(SAR-kuh-meer) repeating structural unit of myofibril; composed of thick and thin filaments; extends between two adjacent Z lines

thick filament (myosin)

myosin filament in muscle cell

thin filament (actin)

actin filament in muscle cell

tropomyosin

(troh-poh-MY-oh-sin) regulatory protein capable of reversibly converting binding sites on actin; associated with muscle thin filaments

troponin

(troh-POH-nin) regulatory protein bound to actin and tropomyosin of striated muscle thin filaments; site of calcium binding that initiates contractile activity

A band

one of the transverse bands making up repeated striations of cardiac and skeletal muscle; region of aligned myosin-containing thick filaments

Z line

structure running across myofibril at each end of striated muscle sarcomere; anchors one end of thin filaments and titin

I band

one of transverse bands making up repeating striations of cardiac and skeletal muscle; located between A bands of adjacent sarcomeres and bisected by Z line

H zone

one of transverse bands making up striated pattern of cardiac and skeletal muscle; light region that bisects A band

M Line

transverse stripe occurring at the center of the A band in cardiac and skeletal muscle; location of energy-generating enzymes and proteins connecting adjacent thick filaments

titin

protein that extends from the Z line to the thick filaments and M line of skeletal muscle sarcomere

cross bridges

in muscle, myosin projection extending from thick filament and capable of exerting force on thin filament, causing the filaments to slide past each other

contraction

operation of the force-generating process in a muscle

relaxation

return of muscle to a low force-generating state, caused by detachment of cross-bridges

sliding filament mechanism

process of muscle contraction in which shortening occurs by thick and thin filaments sliding past each other

rigor mortis

(rig-or MOR-tiss) stiffness of skeletal muscles after death due to failure of cross-bridges to dissociate from actin because of the loss of ATP

excitation contraction coupling

in muscle fibers, mechanism linking plasma membrane stimulation with cross-bridge force generation

sarcoplasmic reticulum

(sar-koh-PLAZ-mik reh-TIK-you-lum) endoplasmic reticulum in muscle fiber; site of storage and release of calcium ions

lateral sacs

aka terminal cisternae, (ter-mih-null sys-TER-nay) expanded regions of sarcoplasmic reticulum, associated with T-tubules and involved in the storage and release of Ca2+ in skeletal muscle cells; also known as lateral sacs

transverse tubule

(T-tubule) - tubule extending from striated muscle plasma membrane into the fiber, passing between opposed sarcoplasmic reticulum segments; conducts muscle action potential into muscle fiber

motor neuron

somatic efferent neuron, which innervates skeletal muscle

motor unit

motor neuron plus the muscle fibers it innervates

acetylcholine

(ass-ih-teel-KOH-leen) a neurotransmitter released by pre- and postganglionic parasympathetic neurons, preganglionic sympathetic neurons, somatic neurons, and some CNS neurons

motor end plate

specialized region of muscle cell plasma membrane that lies directly under axon terminal of a motor neuron

neuromuscular junction

synapse like junction between an axon terminal of an efferent nerve fiber and a skeletal muscle fiber

tension

in muscle physiology, the force exerted by a contracting muscle on object

load

external force acting on muscle

isometric contraction

(eye-soh-MET-rik) contraction of muscle under conditions in which it develops tension but does not change length

isotonic contraction

contraction of muscle under conditions in which load on the muscle remains constant but muscle changes length

twitch

mechanical response of muscle to single action potential

latent period

(LAY-tent) period lasting several milliseconds between action potential initiation in a muscle fiber and beginning of mechanical activity

summation

(sum-MAY-shun) increase in muscle tension or shortening in response to rapid, repetitive stimulation relative to single twitch

tetanus

(TET-ah-nus) maintained mechanical response of muscle to high-frequency stimulation; also the disease lockjaw

creatine phosphate

(KREE-ah-tin) molecule that transfers phosphate and energy to ADP to generate ATP

muscle fatigue

decrease in muscle tension with prolonged activity

oxidative phosphorylation

(fos-for-ih-LAY-shun) process by which energy derived from reaction between hydrogen and oxygen to form water is transferred to ATP during its formation

glycolytic pathway

glycolysis - (glye-KOL-ih-sis) metabolic pathway that breaks down glucose to two molecules of pyruvate (aerobically) or two molecules of lactate (anaerobically)

dense bodies

cytoplasmic structure to which thin filaments of a smooth muscle fiber are anchored

pacemaker

neurons that set rhythm of biological clocks independent of external cues; any neuron or muscle cell that has an inherent autorhythmicity and determines activity pattern of other cells

varicosities

(vair-ih-KOS-ih-tee) swollen region of axon; contains neurotransmitter-filled vesicles; analogous to presynaptic ending

myosin light chain kinase

smooth muscle protein kinase; when activated by Ca2+-calmodulin, phosphorylates myosin light chain

calmodulin

(kal-MADJ-you-lin) intracellular calcium-binding protein that mediates many of calcium's second-messenger functions

dihydropyridine DHP receptor

nonconducting calcium channels in the T-tubule membranes of skeletal muscle cell, which act as voltage sensors in excitation-concentration coupling.

Ryanodine receptor

calcium-release channel found in the lateral sacs of the sarcoplasmic reticulum in skeletal muscle cells

Fermentation

a metabolic process that converts sugar to acids, gases or alcohol. It occurs in yeast and bacteria, and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.

glycolysis

the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+.

aerobic cellular respiration

the process in which our cells break down food and turn it into that cells need to prove every day processes.

L-type Calcium channels

channels that couple membrane depolarization in neurons to numerous processes including gene expression, synaptic efficacy, and cell survival.