A&P

Ch.9,10,13

Three types of muscles tissue include

skeletal, cardiac , & smooth

Three prefixes used to refer to muscle

myo, mys, sacro

Define sarcoplasm

the cytoplasm of a muscle cell

Define sarcolemma

the cell membrane of a muscle cell

Why is it called "skeletal" muscle tissue?

Because it forms muscles that attach to the skeleton

Skeletal muscles cells have obvious stripes called

striations

Why is skeletal muscle tissue called voluntary muscle

Because it is the only type subject to conscious control

Describe skeletal muscle

long, cylindrical cells ; each cell is multinucleated with the nuclei just deep to the cell membrane

Skeletal muscle is....

striated and voluntary

Cardiac Muscle is .....

striated and involuntary

_____ forms the middle, muscular layer of the heart wall called myocardium

Cardiac muscle tissue

Describe cardiac muscle tissue

branched cells with one central nucleus

In cardiac muscle tissue- The cells are joined end to end to fit together tightly at unique junctions is called __________

Intercalated discs

Why are intercalated discs important (2)

1. Strengthen the cardiac muscle tissue and hold the cells together during contractions
2. Allow conduction of cardiac muscle action potentials (impulses) to spread quickly throughout the heart

Smooth muscle tissue is ...

Not striated & involuntary

Where is smooth muscle tissue found

in the walls of hollow visceral organs

Examples of where smooth muscle tissue is found in

Stomach, urinary bladder, respiratory passages

What is the role of smooth muscle tissue

To force fluids and other substances through internal body channels

Smooth muscle forms

valves, dilates, and constricts the pupils, and forms arrector pili muscles

Describe smooth muscle tissue

spindle shape and each cell has an elongated, central nucleus

Contraction of smooth muscle is regulated by

hormones and the autonomic division of the nervous system

The 4 special characteristics of muscle tissue is

Excitability, contractility, extensibility, elasticity

The four important functions of muscle

1. Produce movement
2. Maintain posture & body position
3. Stabilize joints
4. Generate heat

1. Produce movement described

Skeletal muscles are responsible for all locomotion & manipulation

2. Maintain posture & body position described

tiny adjustments to counteract the downward pull of gravity

3. Stabilize joints described

Strengthen and stabilize the joints of the skeleton

4. Generate heat described

As they contract muscles generate heat which plays into maintaining normal body temperature

Special characteristic excitability described

"responsiveness", ability of a cell to receive, and respond to a stimulus by changing its membrane potential, stimulus is usually a chemical

Special characteristic contractility described

Ability to shorten forcibly when adequately stimulated. Sets muscles apart from all other tissue types

Special characteristic extensibility described

Ability to extend or stretch; when relaxed muscles can extend beyond their resting length

Special characteristic elasticity described

ability of a muscle cell to recoil and resume its resting length after stretching

A skeletal muscle is made up of

muscle fibers, blood vessels, and connective tissue

Define skeletal muscle

is an organ because it is formed by two or more types of tissue

Each muscle is served by

1 nerve, 1 artery, & 1 or more veins

Skeletal muscle is said to be

well innervated and well vascularized

_____ is associated with skeletal muscles

connective tissue sheaths

Superficial fascia

is loose connective tissue that separates muscles from skin ; provides a pathway for vessels and nerves to and from muscles

Deep fascia

is dense irregular connective tissue that fills spaces between muscles and holds muscles with similar functions together ; it allows free movement of muscles and carries vessels and nerves

Three layers of connective tissue

epimysium, perimysium, edomysium

The three connective tissue do what

Extend from the deep fascia to protect and strengthen skeletal muscle

epimysium

dense irregular connective tissue that encircles the entire skeletal muscle

perimysium

dense irregular connective tissue that surrounds groups of 10 to 100 muscle cells, grouping them into bundles called fascicles

edomysium

areolar connective tissue within each fascicle that surrounds individual muscle cells

Describe a direct ( fleshy) muscle attachment

The epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage

Describe indirect muscle attachment

the muscle connective tissue wrapping extend beyond the muscle either tendon, or aponeurosis ; The T or A anchors the muscle to the connective tissue covering of a skeletal element or to the fascia of other muscles

Tendon

ropelike, cordlike ; formed of dense regular CT

Aponeurosis

sheetlike, a broad flat sheet of dense regular CT

Skeletal muscle fibers contain

calcium-regulated molecular motors

Sacrolemma

the cell membrane of a muscle cell

What is the skeletal muscle range in diameter

10-100 ; up to 30 cm

Define sarcoplasm

the cytoplasm of a muscle fiber

The sarcoplasm contains what

glycosomes and myoglobin

Define glycosomes

granules of stored glycogen that provide glucose during muscle cell activity for ATP production

Define myoglobin

oxygen-binding pigment in muscle ~ red pigment that stores oxygen

Define myofibrils

tiny rod like structures that are packed in the cytoplasm and run the length of the cell

How many myofibrils are in a single muscle cell

hundreds to thousands

Myofibrils are made of a chain of what

sacromeres

Define striations

a repeating series of dark and light bands; are evident along the length of each myofibril

Myofibrils contains _____ and _____

thick myofilaments & thin myofilaments

Thick and thin myofilaments are

very orderly arranged by forming bands

The forming bands of thick and thin myofilaments include

A band, I band, H zone, & Z discs

A band

a region that extends the entire length of the thick filaments and it contains thick filaments and overlapping thin filaments

I band

area on each side of an A band that contains the rest of the thin filaments but no thick filaments`

H zone

an area in the center of the A band that contains only thick filaments

Z discs

proteins to which thin filaments attach

Sarcomere

is the unit of a myofibril that extends from one Z disc to the next Z disc

What is the smallest contractile unit of a muscle cell; the functional unit of contraction

sacrcomere

The two main contractile proteins in muscle that form the myofilaments are

actin and myosin

Myosin

thick filaments are formed by it; shaped like a golf club with two heads

Two heads of myosin is called

globular heads

The myosin heads have _____ and _________ and contain _____

actin-binding sites & binding sites for ATP; contain ATPase enzymes that split ATP

Actin

thin filaments form it; has polypeptide subunits

Globular Actin (G actin)

polypeptide subunits, kidney shaped

The G actin molecules are polymerized into what

long actin filaments called filamentous or F actin

The backbone of each filament is formed by two intertwined F actin filaments that look like what?

Twisted double strand of pearls

Each G actin of the actin filament has a ___________ to which the myosin heads attach during contraction

myosin binding site

In relaxed muscles, the myosin binding sites on actin are blocked by a rod-shaped protein called

tropomyosin

Does the distance between successive Z discs shorten

Yes

As a muscle cell shortens ; do the I bands shorten?

Yes

Do the H zones disappear

yes

What happens to the A bands within a sarcomere

Move closer together but their length does not change

Motor neurons ________ skeletal muscle fibers to contract

stimulate

The four steps that must occur for a skeletal muscle cell to contract

1. The cell must be activated, that is, stimulated by a neuron ~ nerve cell
2. It must generate an electrical current called an action potential or impulse in its sarcolemma
3. The action potential is automatically propagated along the sarcolemma
4. Intracellular calcium ion levels must rise briefly, providing the final trigger for contraction

The motor neurons that activate skeletal muscle cells is called

somatic motor neurons; motor neurons of the somatic, voluntary, nervous system

Neuromuscular junction

is the synapse between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell

Action potentials

electrical currents, are conducted along axons of motor neurons to the neuromuscular junction

As a rule, each muscle has only ____________ located about midway along it's length

one neuromuscular junction

The neuromuscular junction is formed by three main parts

1. Axon terminal
2. Synaptic cleft
3. Junctional holds of the sarcolemma

Axon terminal

the end of the axon of the motor neuron, within are synaptic vessels

Synaptic vessels

within axon terminal; and contain neurotransmitteracetylcholine

Synaptic cleft

space filled with gel-like extracellular substance between an axon terminal and the sarcolemma of the skeletal muscle cell

Junctional folds of the sarcolemma

the folded part of the sarcolemma that is associated with the axon terminal

The receptors associated within junctional folds of the sarcolemma is called

ACh receptors

Events at the neuromuscular junction that lead to the transmission of an impluse from the motor neuron to the skeletal muscle cell includes these steps

1. Release of acetylcholine (ACh)
2. Activation of ACh receptors
3. Production of a muscle action potential
4. Termination of ACh activity

1. Release of acetylcholine (ACh)

A nerve impulse along the axon of the motor neuron reaches the axon terminal. This triggers the release of the neurotransmitter acetylcholine (ACh) from the synaptic vesicles by exocytosis into the synaptic cleft

2. Activation of ACh receptors

Acetylcholine diffuses across the synaptic cleft and binds to ACh receptors on the junctional folds of the sarcolemma. This opens ion channels in the sarcolemma.

3. Production of a muscle action potential

The inflow of ions generates a muscle action potential (impulse) in the junctional folds of the sarcolemma of the muscle cells

4. Termination of ACh activity

Acetylcholine that is bound to ACh receptors of the junctional folds is then rapidly broken down in the synaptic cleft by acetylcholinesterase

Acetylcholinesterase

is an enzyme in the synaptic cleft near the sarcolemma of the junctional folds

The destruction of ACh prevents

continued contraction of the muscle cell