chapter 10 - muscle tissue

the 4 common properties of all muscle types

excitability, contractility, extensibility, elasticity

ability to change electrical states and propagate action potentials

excitability

ability to shorten and generate force

contractility

ability to stretch beyond resting length

extensibility

ability to recoil to original length after stretching

elasticity

voluntary, straited, cylindrical, multinucleated (due to fusion of myoblasts) (muscle tissue)

skeletal muscle

involuntary, straited, intercalated discs (muscle tissue)

cardiac muscle

involuntary, non-striated, single nucleus, spindle-shaped (muscle tissue)

smooth muscle

functions of the skeletal muscle

movement of the skeleton, stabilizes joints and prevents skeletal damage, controls voluntary movement of the digestive urinary and other tracts, protects internal organs, generates heat during contraction

found only in the heart wall, pumps blood through the circulatory system via force and pressure gradients (type of muscle tissue)

cardiac muscle

found in walls of arteries (regulates blood flow, pressure), in visceral organs/passageways, in skin (arrector pili muscle), does not connect to bone (type of muscle tissue)

smooth muscle

composed of long muscle fibers, appears straited due to actin and myosin filaments and their arrangements, rich vascular supply, contraction via motor units, tendons connect muscle to bone (type of muscle tissue)

skeletal muscle

skeletal muscle attachments...

muscles span joints and attach to bones; muscles attach to bone in at least 2 places; attachments can be direct or indirect

attachment to movable bone (location of skeletal muscle attachments)

insertion

attachment to immovable or less movable bone (location of skeletal muscle attachments)

origin

epimysium fused to periosteum of bone or perichondrium of cartilage (skeletal muscle attachment)

direct

connective tissue wrappings extend beyond muscle as ropelike tendon or sheetlike aponeurosis (skeletal muscle attachment)

indirect

each skeletal muscle is covered in connective tissue; name the connective tissues sheaths from external to internal and function?

epimysium, perimysium, and endomysium; support cells and reinforce whole muscle

dense irregular connective tissue surrounding entire muscle; may blend with fascia (CT sheaths on skeletal muscle)

epimysium

fibrous connective tissue surrounding fascicles (CT sheaths on skeletal muscle)

perimysium

fine areolar connective tissue surrounding each muscle fiber (CT sheaths on skeletal muscle)

endomysium

a muscle is made of a group of ?

fascicles

a fascicle is a group of ?

muscle cells OR muscle fibers

a muscle fiber has many special tube-like specialized organelles called

myofibrils

myofibrils are made up of many ?

sarcomeres

sarcomeres are made up of

actin and myosin filaments

plasma membrane of a muscle cell, conducts action potentials (anatomy of skeletal muscle fibers)

sarcolemma

contractile organelles made up of sarcomeres (anatomy of skeletal muscle fibers)

myofibrils

what kind of filaments are actin and myosin?

actin - thin

myosin - thick

stores, releases calcium for muscle contraction (anatomy of skeletal muscle fibers)

sarcoplasmic reticulum

muscle cells contain _ and _ ; function?

glycosomes (glycogen storage) and myoglobin (O2 storage)

deep invaginations of the sacrolemma that penetrate the interior to allow rapid transmission of electrical action potentials

t-tubules

stripes formed from repeating series of dark and light bands along length of each myofibril

striations

contains thick and thin filaments that are partially overlapped; dark regions; holds the H zone and M line (parts of a sarcomere)

A Band

contains only thin filaments; lighter regions; holds the Z disc (parts of a sarcomere)

I Band

contains only thick filaments (myosin); m-line bisects this zone (parts of a sarcomere)

H Zone

defines the boundary between one sacromere and the next, attaches/anchors to actin filaments; coin-shaped sheet of proteins on midline of light I band

Z Disc

first step of muscle contraction...

myosin heads bind to myosin binding sites on actin

second step of muscle contraction...

actin is pulled closer to the M-line by myosin pulling on it and sliding it over

third step of muscle contraction...

sacromere shortens, myofibrils shorten, muscle cell shortens, overall muscle shortens

how are muscle contractions initiated

through an action potential

where is the signal during a muscle contraction sent from

motor neuron

where does the action potential spread from once it reaches the muscle cell

around the sarcolemma, along the t-tubules, and lastly the sarcoplasmic reticulum

when the action potential reaches the sarcoplasmic reticulum, what does it release? and what does it bind to?

calcium; binds to actin CAUSES a contraction

process leading to calcium release and muscle contraction

excitation-contraction coupling

muscle contractions begin here; the space between the end of a neuron and a muscle cell

neuromuscular junction

a neuron that carries an action potential towards something that is going to be triggered to move; every skeletal muscle fiber is innervated by this at an NMJ

motor neuron

what is released at the end of a neuron once an action potential travels to the end of a neuron

acetylcholine

what does acetylcholine attach to once it crosses the NMJ

sarcolemma; then causes an action potential for the muscle cell

what does an action potential cause to release? where does it release from?

calcium; sarcoplasmic reticulum

tension remains constant; muscle changes length (type of contraction)

isotonic contraction

muscle shortens (isotonic contraction)

concentric

muscle lengthens (isotonic contraction)

eccentric

muscle generates tension without changing length (type of contraction)

isometric contraction; note: MOST BODY MOVEMENTS COMBINE THE TWO TYPES OF CONTRACTIONS

location of smooth muscle tissue:

hollow organs (stomach, intestines, bladder), blood vessels, airways, eyes, skin (arrector pili)

control of smooth muscle tissue

involuntary, regulated by ANS, hormones, and stretch

cell structure of smooth muscle tissue

spindle-shaped, single nucleus, arranged in sheets, no striations

smooth muscle in __ regulates airflow resistance

airways

smooth muscle in ___ regulates blood pressure and perfusion

blood vessels

understanding multi-unit smooth muscle in airways explains ___ and treatments

bronchoconstriction

constant, slightly contracted state of muscles, due to spinal reflexes, keeps muscles firm, healthy, and ready to respond

muscle tone