AnaPhy: Ch.9 Incomplete

skeletal muscle

voluntary muscle and constitutes about 40%of the body’s weight; attached to bone;
functions as body movement; locomotion, facial expressions, posture, respiratory functions, speech

skeletal muscle

type of muscles attached to bone and with striations; functions as body movement

cell shape of skeletal muscle

very long and cylindircal

smooth muscle

involuntary muscle most widely distributed in the body; found in walls of hollow organs, blood vessels, eyes, glands, and skin

smooth muscle function

propels urine through the urinary tract, mixes food in the stomach and the small intestines, regulates blood flow in blood vesseld

cell shape of smooth muscle

spindle shaped; single centrally located

skeletal muscle

type of muscle not capable of spontaneous contraction

cardiac muscle

involuntary muscle found in the heart; with striations

cardiac muscle

functions: pumps blood; contraction provide the major force for propelling blood through blood vessels

functions of the three types of muscle

movement of the body, maintenance of posture, respiration, production of body heat, communication, constriction of organs and blood vessels, contraction of the heart

movement of the body

most skeletal muscles are attached to bones and are responsible for the majority of body movement; walking, running, chewing

maintenance of posture

skeletal muscles constantly maintain tone, which keeps us sitting or standing erect

respiration

contraction of the skeletal muscles of the thorax and diaphragm help us breathe

production of body heat

when skeletal muscles contract, heat is given off as a by-product

communication

skeletal muscles are involved in all aspects of communication; speaking, writing, typing, gesturing, smiling or frowning

constriction of organs and vessels

contraction of smooth muscles within walls of internal organs causes the structures to constrict which help propel and mix food in the digestive tract, remove materials in organs

constriction due to smooth muscle contraction

help propel and mix food and water in the digestive tract; remove materials from organs, and regulate blood flow

contraction of the heart

contraction of the cardiac muscle causes heart to beat, propelling blood to all parts of the body

four major functional/general properties of muscle tissue

contractility, excitability, extensibility, elasticity

contractility

the ability of muscles to shorten forcefully and contract; lifting books

when muscles contract, it can cause

structures to which it is attached to move or increase pressure inside a blood vessel' or hollow organ

forces that oppose contraction

cause muscle to lengthen passively; gravity pulling on a limb

excitability

the capacity of muscle to respond to an electrical stimulus

smooth muscle and cardiac muscle respond to stimulation by

nerves and hormones

extensibility

a muscle can be stretched beyond its normal resting length and still be able to contract; retrieving a fallen pencil on the ground

elasticity

the ability of muscle to spring back to its original resting length after its been stretched; taking a deep breath

skeletal muscles are composed of

skeletal muscle tissues, nervous tissue, connective tissue, and adipose tissue

each muscle cell is called

muscle fiber

connective tissue coverings

each skeletal muscle is surrounded by these tissue layers that support the muscle during contraction

three layers of connective tissue in a skeletal muscle

epimysium, perimysium, endomysium

epimysium

forms a connective tissue sheath that surrounds each skeletal muscle; a layer of dense irregular connective tissue

epimysium protein fibers merge with

a connective tissue whose protein fibers gradually merge with muscular fascia between adjacent muscles and between muscles and skin

muscular fascia

outer layers of connective tissue that keep muscles separate from surrounding tissues and organs

perimysium

subdivides each whole muscle into numerous, visible bundles of muscle fibers called fascicles

fascicles

visible bundles of muscle fibers

perimysium

a loose connective tissue serving as passageways for blood vessels and nerves that supply each fascicle

endomysium

a delicate layer of connective tissue that covers and separates the individual muscle fibers within each fascicle

endomysium

serves as passageways for nerve fibers and blood vessels that supply each separate muscle fiber

epimysium

outer most layer of connective tissue covering that surrounds muscle organs

perimysium

middle layer of connective tissue covering that surrounds each fascicle

endomysium

innermost layer of connective tissue covering that surrounds the muscle fibers

collagen fibers of the connective tissue coverings

converge at the ends of muscle and together form tendons and aponeuroses; they are interwoven and blend into one another

epimysium of one muscle directly attaching to tendons or fascia of another muscle

attachments that serve to move bones or skin for locomotion, facial expressions, and other types of movement

skeletal muscle fibers

very unique cells that develop from the fusion of several hundred embryonic cells called myoblast

myoblast

embryonic cells that contain its own nucleus

sarcoplasm

muscle cell cytoplasm; contains high amounts of myoglobin and glycogen

myoglobin

conjugated protein which is the oxygen-transporting pigment of muscle

sarcolemma

muscle fiber cell membrane; contain transverse tubules (T-tubules); transmits electrical impulses to the interior of the muscle fiber

t-tubules

tube-like inward folds of the sarcolemma; carry electrical impulses into the center of the muscle fiber

sarcoplasmic reticulum

highly specialized smooth endoplasmic reticulum in skeletal muscle fibers that stores high levels of Ca; release of Ca from the sarcoplasmic reticulum is a “switch” for muscle contraction

sarcoplasm

muscle fiber containing organelles such as mitochondria and energy-storing glycogen granules that constitute a kind of cytoplasm

terminal cisternae

t-tubules that lie next to enlarged portions of the sarcoplasmic reticulum

t-tubules

allow action potentials to quickly spread to the myofibrils

two channel types contributing to the electrical properties of both resting and stimulated cell

ligand-gated channels, voltage-gated channelsl

ligand-gated channels

open when a specific ligand, a chemical signal such as neurotransmitter binds to a receptor

voltage-gated ion channel

are gated membrane channels that open and close in response to a specific membrane potential

voltage-gated channels that play major roles in an action potential

voltage-gated Na, K, Ca channels

electrically excitable cells

are polar; specialized to respond to electrical stimuli

intercalated disk

helping muscles contract

hypertrophy

increase in size of each muscle fiber

mechanical component structures

myofibrils, myofilaments (actin, myosin)

actin myofilaments

thin filaments made up of 2 long-coiling protein strands; connected to Z disks of sarcomeres; located between each myosin filament

myosin myofilaments

thick filaments arranged in parallel; have a main shaft and a globular head on each end

sarcomeres

join end to end forming myofibrils; smallest portion that can contract; contractile structures formed by overlapping actin and myosin

3 regulatory proteins of actin

globular actin, tropomyosin, troponin

G actin

molecules that are globular subunits that form a long chain of 200 G actins subunits; active site for myosin head binding during contraction

F actin (fibrous)

chain of 200 G actin subunits

tropomyosin

a long fibrous protein that lies in the groove along the fibrous actin strand

troponin

consist of three subunits: TnC- binds to Ca, TnT- binds to tropomyosin (prevents the tropomyosin from uncovering G actin active site) TnI- binds to G actin (inhibits actin to myosin binding)

myosin components

2 myosin heavy chains (forms the rod portion), 2 myosin heads

neuromuscular junctions

also called an end plate; point of contact of motor neuron axon branches with the muscle fiber

action potential

electrical signals

motor neuorons

carries action potential signals which stimulate muscle fiber action potentials followed by muscle cotraction

presynaptic terminal

axon terminals

synaptic cleft

space between the presynaptic terminal and the muscle fiber

motor-end plate/ postsynaptic membrane

muscle plasma membrane/ sarcolemma in the area of the junction; depression in the sarcolemma of the adjacent muscle fiber, n close association with the synaptic knob

synaptic vesicles

numerous mitochondria and spherical sacs in the presynaptic terminals; contains neurotransmitters called acetylcholine (ACh)

neurotransmitter

a molecule that allows a neuron to communicate with its target

neurotransmitters (ACh)

inhibits the production of action potential in the motor-end plate by binding to ligand-gated ion channels

sarcomere

region between two Z lines

Z discs

filamentous networks of proteins form a stationary anchor for actin myosin filaments

I bands (isotropic)

2 two lighter straining regions; consisting only of thin filaments

A bands

darker straining band in the center of each sarcomere; formed by entire length of thick myosin filaments

H zone

smaller band at the center of each A band

M line

dark line at the middle of each H zone; consists of delicate filaments that hold the myosin myofilaments in place

threshold

is the membrane potential at which voltage-gated ion channels open

depolarization phase

the action potential is a brief period during which further depolarization occurs and the inside of the cell becomes even more positively charged

repolarization phase

return of the membrane potential to its resting value

triad

a skeletal muscle substructure responsible for the regulation of excitation-contraction coupling

excitation-contraction coupling

link between an action potential on the sarcolemma and the sarcomere shortening

power stroke

movement of myosin head in cross-bridging

muscle twitch

response of a muscle fiber to a single AP along its motor neurons

myograph

recording produced from a single isolated twitch

phases of a twitch

lag phase, contraction phase, relaxation phase

lag phase/ latent phase

time during which action potential is traveling along the axon, the events at neuromuscular junction occurs, and the AP travels along the sarcolemma

contraction phase

Ca is released from SR and cross-bridge cycling occurs

relaxation phase

concentration of Ca in the sarcoplasm decreases slowly and Ca is actively transported back into the SR

action potential

electrochemical event

muscle contraction

mechanical event

tension

muscle contraction measured as a force