biol 65. ch 10 - muscle tissue

3 types of muscle tissue

3 types of muscle tissue

skeletal, cardiac, smooth

functions of muscle

movement, stability, control of body openings and passages, heat production, glycemic control, hormone production

Properties of muscle

excitability (responsiveness), conductivity, contractability, extensibility, elasticity

excitability

react to stimuli

conductivity

spread electrical impulse through cell muscle

contractibility

shorten when stimulated

extensibility

stretch without harm

elasticity

recoil from stretch

skeletal muscle

voluntary, striated, attached to bone, muscle cell (myofiber)

cardiac muscle

involuntary, striated, cardiomyocytes

smooth muscle

involuntary, nonstriated, fusiform (tapered at ends) cell shape

sarcolemma

plasma membrane of muscle fiber

sarcoplasm

cytoplasm of muscle fiber

sarcoplasmic reticulum

modified ER loaded with calcium for muscle contraction, terminal cisterns

regulatory proteins

-tropomyosin (blocks sites when muscle is relaxed)

-troponin (attaches to tropomyosin, binds calcium when excited)

tropomyosin

blocks sites when muscle is relaxed

troponin

attaches to tropomyosin, binds calcium when excited

contractile proteins

- thick myofilaments, myosin

- thin myofilaments , actin (fibrous actin and globular actin)

myosin

heads project from bundled tails of hundreds of molecules

fibrous actin

resembles necklace

globular actin

resembles 1 bead of necklace

striations

narrow stripes (light and dark) that run perpendicular to the length of the cell

sacromeres

-A band: dark stripe of thick myofilaments that partly overlap thin myofilaments

-H band: central region of A band that is a little lighter due to lack of thin myofilaments (contains M line: midline of A and H band that anchors thick myofilaments together)

-I band: light stripe of thin myofilaments only

- Z line/disc: midline of I band, protein that anchors thin filaments (actin) and elastic filaments (titin). defines boundaries of a sacomere

A band

dark stripe of thick myofilaments that partly overlap thin myofilaments

H band

central region of A band that is a little lighter due to lack of thin myofilaments (contains M line: midline of A and H band that anchors thick myofilaments together)

I band

light stripe of thin myofilaments only

Z line/disc

midline of I band, protein that anchors thin filaments (actin) and elastic filaments (titin). defines boundaries of a sacromere

neuromuscular junction

synapse

synaptic knob

of a motor neuron, contains vesicles with a neurotransmitter that is released into the synaptic cleft

synaptic cleft

receives vesicles with neurotransmitter released by the synaptic knob

postsynaptic membrane folds

contain receptors for the neurotransmitter

resistance exercises

stimulates the production of more myofilaments. growth is through hypertrophy not hyperplasia.

exercise

stimulates production of mitochondria, myoglobin, glycogen, blood vessels

cardiac muscle

striated, short cells, intercalated discs w gap junctions, mononucleated, involuntary

smooth muscle

no striations, fusiform cell, mononucleated, involuntary. multiunit - independent control of smooth muscle cells. unitary - several cells excited at once; widespread in viscera

myopathies

diseases of muscle

muscular distrophy

skeletal muscle degeneration, hereditary. defective gene for dystrophin (a muscle protein)

myasthenia gravis (MG)

autoimmune disease, destruction of muscle neurotransmitter receptors

dystrophin

transfers the force of moving actin filaments to tissues leading to the muscle’s tendon

sarcoplasmic reticulum

reservoir of calcium ions

what composes thick myofilaments of a muscle fiber

myosin

what composes thin myofilaments of a muscle fiber

fibrous and globular actin

dark band

A band

light band

I band

light region of the A band

H band

dark line in the middle of the H band

M line

disc in the middle of an I band

Z disc