Anatomy and Physiology exam 3

UNI Dr. Cline-Brown

What are the functions of muscles?

movements, protection, heat production, joint stability

Why are muscles an organ?

2 types of tissues, has blood vessels, nervous tissue, and connective tissue

What characteristics do all muscles have?

extensibility, elastibility, excitability, contractability

Extensibility

can be pulled

Elastibility

can go back to normal shape

Excitability

can have electrical changes and send action potentials

Contractibility

the ability to contract

What are the 3 types of muscles?

smooth, skeletal, and cardiac

Characteristics of skeletal muscle

voluntary, mutinucleated, striated

Muscle fiber

a cell of muscle

Fascicle

a group of muscle fibers

Epimysium

a membrane that goes around a muscle

Perimysium

a membrane that goes around a fascicle

Endomysium

a membrane that goes around a fiber

Myofibril

a protein structure inside a muscle cell

What is the contractual unit of a muscle?

a myofibril (specifically sarcomeres)

What does the contraction for the myofibril?

myofilament

Types of myofilaments

myosin or actin

What are the functions of muscular fascia?

separate muscles from surrounding tissues and organs, reduces function between muscles, attachment point for skeletal muscles

Types of muscular fascia?

superficial fascia and deep fascia

Superficial fascia

under skin

Deep fascia

a tough layer between muscles

What is between fascicles?

blood vessels

Myoblasts

build skeletal muscle

What is 1 pointing to?

blood vessels

What is 2 pointing to?

perimysium

What is 3 pointing to?

epimysium

What is 4 pointing to?

muscle fiber/cell

What is 6 pointing to?

fascicle

What is 5 pointing to?

endomysium

Sarcolemma

a plasma membrane of a muscle cell

What are the folds in the sarcolemma called?

t tubules

What do t tubules do?

allows ions or impulses inside to generate muscle contraction

Sarcoplasma

muscle cell plasma

Myoglobin

stores oxygen in muscle cells, caused the dark look

Glycosomes

stores glucose for muscle cells

Sarcoplasmic reticulum

goes around myofilaments and stores calcium for contraction

Terminal cisternae

enlarged portions on either end of the SR next to t tubules

Triad

2 terminal cisternae and 1 t tubule

Sarcomere

join end to end to form basic building blocks of microfibrils

What causes the striations in skeletal muscle?

sarcomeres

Actin myofilament

made of spherical shaped actin molecules, THIN

Myosin myofilament

pulls actin to make actin slide during contraction, THICK

What does calcium do for muscles?

causes contraction

What are the structure of actin?

2 actin chains twisted together, have an active site

Tropomyosin

a strand like protein in grooves created by the twisted actin that supports the chains, when muscle is relaxed it blocks the actin active sites

Troponin

binds tropomyosin, actin, and calcium. Allows muscle contraction

What is the function of myosin?

to slide actin towards the middle of sarcomere

What is the structure of myosin like?

2 golf clubs twisted together (myosin heads)

What do myosin heads do?

point towards the actin and grabs them

What is the myosin hinge region?

rod and head joining area, allows myosin head to flex towards rods

Components of myosin heads

actin binding site, ATP binding site, enzyme port to break down ATP

M line

the middle of the sarcomere

Z disks

the ends of the sarcomere

A band

where myosin and actin overlap

H zone

where there is only myosin (middle)

I band

where there is only actin (goes over the Z disks)

Crossbridge

the area where myosin heads bind with actin active sites

Titin

an elastic filament that acts like a spring so myofilaments don’t move out of alignment

List the parts of the muscle from smallest to largest

actin/myosin, sarcomeres, myofibril, muscle fiber, endomysium, fascicle, perimysium, epimysium

What is tropomyosin also known as, and why?

a regulatory protein, it can hinder or cause muscle contraction

What happens to the H zone when a muscle contracts?

gets smaller or disappears

What is the “sliding filament theory of muscle contraction”?

actin filaments slide over myosin, thereby shortening the sarcomere

Do actin and myosin filaments get shorter during contraction?

no, they slide over each other

What is the first step of muscle contraction (think inside a sarcomere)

a reason to contract causes Ca2+ flooding muscle cell and bind with troponin on actin.

What is the second step of muscle contraction? (think inside a sarcomere)

myosin heads to “cock” to bind actin active sites and form cross bridge

What is the third step of muscle contraction? (think inside a sarcomere)

Once actin has been pulled, the myosin heads will let go and bind an active site further up on the actin

Cross bridge cycling

all sarcomeres contract in unison to make a large muscle contract

What 2 molecules are needed for muscle contraction?

calcium and ATP

What happens if calcium or ATP is gone?

no muscle contraction

Neuromuscular junction

where a neuron and muscle meet, and where action potentials are exchanged

What is the “Excitation contraction coupling”?

skeletal muscle requires an impulse to contract, the impulse creates an action potential across the sarcolemma and SR triad that opens calcium channels that flood the cytosol of the muscle cell

What is the first step of Excitation Contraction Coupling?

A neuron sends an AP to skeletal muscle

What is the second step of Excitation Contraction Coupling?

T tubules release calcium into the cell

What is the third step of Excitation Contraction Coupling?

troponin binds with calcium allowing tropomyosin to bind

What is the fourth step of Excitation Contraction Coupling?

myosin heads bind to actin active sites (cross bridge)

What is the fifth step of Excitation Contraction Coupling?

myosin heads pull the actin, release, pull again (cross bridge cycling)

What happens in muscle relaxation?

Impulse stops,

calcium stops flowing (contraction stops)

troponin is released

and active sites are covered by tropomyosin

What causes rigor mortis?

decrease in O2 depressed ATP

without ATP the calcium leaks into cytoplasm

calcium bind troponin, and tropomyosin moves

allowing crossbridges to form.

Without ATP, the myosin heads can’t let go

Why does rigor mortis stop after a while?

tissues degrade to the point that myosin heads let go without ATP

Motor unit

a neuron and all the muscle cells it interacts with

What is the function of dendrites?

collect signals from other cells, neurons, and sensory receptors

What is the function of the axon?

passes signals

myelin/myelin sheath

a fatty substance that allows for faster movement of electricity

Terminal branches

the ends of the axon

Axon terminals

ends of the terminal branches

Neuromuscular junction

where the axon terminals interact with muscle cells

What do all motor units have in common?

all muscle cells are the same muscle, if the neuron sends an impulse ALL muscle cells connected contract

What is the difference between motor units?

differ in the number of muscle cells connected, and sensitivity to stimuli

What is the function of the neuromuscular junction?

where the motor neuron impulse is transmitted to muscle cells, and where the neuron axon terminal meets with the folded sarcolemma

Synapse

where an impulse is transmitted from one cell to another

What is 1 pointing at?

a sarcomere

What is 2 pointing at?

H band

What is 3 pointing at?

actin filament

What is 4 pointing at?

myosin/myosin head

What is 5 pointing at?

Z disk

What is 6 pointing at?

A band

What is 7 pointing at?

I band

How many times does ATP break to form a cross bridge?

1

After the myosin heads form a cross bridge, how many ATP molecules are needed to break off and attach again?

1 (one to release and rebind)