Functions of Muscle

Myosin Microfilament

"thick" Shape of golf club two intertwined heavy chains. form rod portion lying parallel to myosin, and tow heads extend laterally. contains 300 myosin molecules.

Sliding Filament Model

-Actin myofilaments sliding over myosin to shorten sacromeres. -actin and mysosin do not change length -shortening sarcromeres responsible for skeletal muscle contraction. -During relaxation sarcomeres lengthen because some external force, like contraction of antagonistic muscles.

Action Potential Propagation

-spread from one location to another -action potential does not move along the membrane: new action potential at each successive location.

myosin heads

1) bind to active sites on the acin molecules to form cross-bridges. 2) bend and straighten during contraction, at hinge region. 3) Are ATPase enzymes.

troponin

3 subunits. First binds to actin, second binds to tropomycin, and third binds to calcium ions.

#2

Myosin APTPase enzymes in myosin head hydrolyze and release ATP molecule

#4

Myosin head binds to exposed active site on actin myofilaments to form cross-bridges.

#5

Pi relesed from myosin heads. energy moves myosin head causing actin myfilaments to slide. ADP is released from myosin head

I bands

Z line to end of myosin(start)

Action Potentials

a change in charge from the normal resting state.

Sarcomeres

basic functional unit of fibers.

ATPase enzymes

break down ATP to relase energy which bends the hinge region of the myosin molecule during contractions.

extensibility

capable of being stretched between contractions.

Skeletal muscle structure

composed of muscle cells(fibers), connective tissue, blood vessels, and nerves.

Muscular Fascia

connective tissue sheets external to epimysium, holds muscles together and seperates them into functional groups.

Muscle contraction

controlled by nervous system action potential.

sarcoplasm

cytoplasm of muscle cell

Titin filaments

elastic chains of amino acids. holds actin and myosin in place. muscles ability to stretch and recoil.

Tropomyosin

elongated protein

Z disc

filamentous network of proteins, that serve as attachment for actin myofilaments. Has a striated appearance.

Cardiac Muscle

heart; major source of movement of blood. controlled involuntary by endocrine and autonomic nervous system.

depolarization

inside becomes less negative. Must reach a threshold to depolarize.

Resting Membrane

inside cell is more negative, outside cell is more positive. Na+/K+ pump maintain this. must exist for action potential to occur.

A band

length of myosin

ligand gated ion channel

ligands are molecules that bind to receptors. ex: neurotransmitters

All or None Principle

like camera flash system

conductivity

local electrical change triggers a wave of excitation that travels along the muscle fiber.

myofibrils

long protein bundles that occupy the main portion of the sarcoplasm

Skeletal muscle fibers

long, cylindrical, multinucleated

Excitation-Contraction Couplings

mechanism where an action potential causes muscle like contractions.

M line

middle of H zone

H zone

middle of band; thick filament only(myosin).

What are the five functions of muscle?

movement, maintenance of posture and body temp., communication, construction of organs and vessels, and contraction of the heart.

Steps of muscle parts

muscle to muscle bundle,to muscle fiber, to muscle fibril.

Antagonistic Muscles

muscles that produce the opposite effect.

#8

myosin heads return to resting position. If Ca remains attached to troponin, the cycle continues.

Frequency

number of action potentials produced per unit of time.

What are the three types of muscle tissue?

skeletal, smooth, and cardiac

motor neurons

stimulate muscle fibers to contract. capillary beds surround muscle fibers.

Skeletal muscle appearance

striated appearance due to light and dark banding.

What is located in the Neuromuscular junction?

synapse -presynaptic terminal -synaptic cleft -postsynaptic membrane -motor end plate

Actin Microfilaments

thin microfilaments

F Actin

two fibrous strands, double helix. 200 globular monomer units, G Actin. Each has an active site. Actin site can bind myosin during muscle contraction

Skeletal muscle

voluntary muscles in body movement

Smooth Muscle

walls of hollow organs, blood vessels, eyes, glands, and skin. controlled involuntary by endocrine and autonomic nervous system.

#6

ATP binds to myocin head, causing detachments from actin

#7

ATPase from myosin head splits ATP to ADP and Pi, which remained attached.

#3

Activates the head"cocking" it in an extending position and ADP and Pi remained attached.

perimysium

CT surrounding group/bundle of muscle fibers/each group call a fasciculus.

epimysium

CT surrounds the whole muscle

endomysium

CT with reticular fibers, surrounds muscle fibers.

Steps in neuromuscular junction #1

Ca2+ binds to troponin. troponin/tropomyosin filament moves exposing active sites on actin filaments.

Voltage gated ion channel

open and close in response to small voltage changes across plasma membranes. Each is specific for certain ions.

sarcolemma

plasma membrane of muscle cell

The tropomyosin/troponin complex

regulates the interaction between active sites on G actin and Myosin.

What is responsiveness

responding to chemical signals, stretch, and electrical changes, across the plasma membrane

repolarization

return of resting membrane potential.

elasticity

returns to its original resting length after being stretched.

Muscle/cell fiber

several bundles (fascicle) of muscle fiber in each muscle.

contractility

shortens when stimulated