KINE 3080: Anatomy and Physiology Review

Epimysium

surrounds entire skeletal muscle

Perimysium

Connective tissue surrounding a fascicle

Endomysium

Connective tissue surrounding each muscle fiber

Sarcolemma

Each muscle fiber is surrounded by this membrane

Sarcoplasm

What lays beneath the sarcolemma. The cytoplasm of muscle cell

What does sarcoplasm contain?

cellular proteins, organelles, and myofibrils

Myofibrils

protein structures that make up muscle fibers

types of myofibrils

Sarcomeres called Myosin, actin, troponin, tropomyosin

Myosin

thick filament (dark) (A-band)

Actin

Thin filament (light) (I-band)

Contain troponin and tropomyosin

T/F: Muscle cells are multinucleated

TRUE

sarcoplasmic reticulum

Storage sight for Ca2+

Transverse tubules

How nerves impulses get into cell to signal a contraction

Satellite Cells

undifferentiated cells that play a key role in muscle growth and repair

terminal cisternae

areas of the sarcoplasmic reticulum surrounding the transverse tubules

T/F: Ca2+ is necessary for muscle contraction

TRUE

The steps of neuromuscular junction

1. action potential travels down motor neuron and reaches presynaptic terminal

2. Neurotransmitter Acetylcholine (ACh) releases from synaptic vesicles

3. Action potential initiated on motor end plate

4. Na+ diffusion into muscle = depolarization. (End plate potential, EPP)

Motor Unit

A motor neuron and all of the fibers it innervates

T/F: the NMJ is a potential site of exercise fatigue

TRUE

Depolarization of a muscle cell

Sodium enters the cell, resting membrane potential becomes more positive (+30mV)

Makes inside of cell less negative than the outside.

Repolarizarion of a muscle cell

Potassium (K+) leaves cell, Na+ channels close, membrane potential drops back to resting (~70mv)

All or None Law

Once a nerve impulse starts, it will travel the entire length of the neuron without a decrease in voltage.

Refractory period during action potential

a period where a neuron cannot fire another action potential

EPP, Depolarization, and Repolarization occur

resting membrane potential

the electrical charge of a neuron when it is not active. (-90mV)

How does Muscle contraction start?

1. Acetylcholine released

2. ACh stimulates depolarization of Na+ channels and then open, letting Na+ in.

3. Ca2+ channels open and calcium is pumped into cytosol where it can now bind with troponin. (Part of actin)

4. Muscle contraction begins

sliding filament theory

actin filaments slide toward each other during muscle contraction.

-myosin reaches forward, binds to actin, releases actin, then reaches forward again to bind actin to a new cycle.

-as myosin segment binds and releases actin it forms a cross bride which extend from the thick myosin filaments to thin actin filaments

Power stroke

The contraction of myosin's region

Requires hydrolysis of ATP, which breaks high energy phosphate bonds to release energy.

cross-bridge

Temporary connections between myosin heads and actin filaments. Acts as a force producer for muscle contraction

Myosin-Actin Cycling

myosin reaches forward, binds to actin, releases actin, then reaches forward again to bind actin to a new cycle.

Excitation-Contraction Coupling

events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract

Steps of Excitation-Contraction Coupling

1. The action potential (AP) travels along motor neuron to synaptic knob

2. ACh is released into synaptic cleft and binds to receptors on motor end plate; opening ion channels allowing sodium to enter

3. Sodium influx causes depolarization

4. Depolarizarion of T-tubules causes Ca2+ release from SR

5. Ca2+ binds to troponin, and tropomyosin is moved and uncovers myosin binding sites on actin

6. Cross bridge begins formed

7. Phosphate is released from myosin, cross bridge activates

8. ATP attaches to myosin, breaking the cross bridge. ATP is then broken down into ADP+Pi, which energizes myosin

9. Motor neuron stimulation ends. ACh is no longer released and muscle fiber repolarizes

10. Ca2+ is pumped back into SR and tropomyosin is returned to original position

When does Muscular Contraction occur?

Occurs via the binding of myosin cross-bridge to actin and then repeated cycling of myosin and actin.

Results in a shortening of the muscle fiber

When does muscle relaxation occur?

When the motor neuron stops exciting the muscle fiber and calcium is pumped back into the sarcoplasmic reticulum

Type IIx muscle fiber

FAST TWITCH

Glycolytic ATP production

Low mitochondria content

Low fatigue resistance

High myosin ATPase Activity

Type IIa fibers

INTERMEDIATE FIBERS

Both glycolytic and oxidative ATP production

High mitochondria content

High fatigue resistance

High Myosin ATPase activity

Type I fibers

SLOW TWITCH

Oxidative ATP production

Very high mitochondria content

Very high fatigue resistance

Low myosin ATPase activity

concentric contraction

muscle shortens

Eccentric contraction

Muscle lengthens

isometric contraction

Muscle contracts but there is no movement, muscle stays the same length

What comes before a muscle contraction

Stimulus then a latent period

Optimal length for cross bridging when muscle is shortened (1)

Around 75% tension

Optimal length for cross bridging when muscle is in between (2)

Around 80-90% tension

Optimal length for cross bridging when muscle is relaxed/lengthened (3)

Around 25% tension

T/F: repeated stimulus causes summation

TRUE

Summation

Process of adding together forces of multiple muscle contractions to create stronger contraction

Tetanus

a sustained muscular contraction resulting from a rapid series of nerve impulses

What do capillaries do?

exchange materials with tissues

Artery

(Arterial trunks) blood vessel that carries blood away from the heart

Where does the pulmonary artery transport from

Right ventricle

Where does the Aorta transport from

Left ventricle

Vein

A blood vessel that carries blood back to the heart.

What drains into the right atrium

venas cavae (SVC and IVC)

What drains into the left atrium

Pulmonary veins

What color is oxygenated blood?

red

What color is deoxygenated blood

Blue

Major functions of the cardiovascular system

-Deliver O2 and remove CO2

-Transport hormones and other molecules

-Support temperature balance and control fluid regulation

What are the 3 circulatory elements of the heart

-Pump (Heart)

-Channels or Tubes (blood vessels)

-Fluid medium (blood)

T/F: heart generates pressure to drive blood through vessels

TRUE

T/F: Blood flow doesn't need to meet metabolic demand

FALSE

Blood flow MUST meet metabolic demand

Pulmonary Circulation

right side of the heart pumps deoxygenated blood from right ventricle to the alveoli of the lungs

Oxygenated blood is then pumped back to left side of the heart

Gas exchange occurs at Alveoli

systemic circulation

left side of the heart pumps oxygenated blood from the left ventricle to systemic tissues/cells

Blood carries o2 and nutrients

Deoxygenated blood then pumped to right side of heart

Exchange at capillaries

How many chambers of the heart are there

four

atrium

Receiving chamber

Ventricle

Pumping chamber

Right atrium

Recieves deoxygenated blood from the body

Right ventricle

pumps deoxygenated blood to the lungs

Left atrium

receives oxygenated blood from the lungs

Left ventricle

pumps oxygenated blood to the body

Atrioventricular Valves (AV)

(i.e., right AV valve and left AV valve) between an atrium and a ventricle.

Semilunar Valve

(i.e., pulmonary semilunar valve and aortic semilunar valve)

between a ventricle and an arterial trunk.

What are the layers of the heart?

epicardium, myocardium, endocardium

epicardium (visceral pericardium)

Serous membrane including blood capillaries, lymph capillaries, and nerve fibers

Serves as lubricative outer covering

Myocardium

Myocardium Cardiac muscle tissue separated by connective tissues and including blood capillaries, lymph capillaries, and nerve fibers

Provides muscular contractions that eject blood from the heart chambers

Endocardium

Endothelial tissue and a thick subendothelial layer of elastic and collagenous fibers

protective inner lining of the chambers and valves

T/F: Left ventricle has the most myocardium

TRUE

-Must pump blood to entire body.

-Has the thickest walls (hypertrophy).

-LV hypertrophies with both exercise and disease.

-Exercise adaptations vs disease adaptations to the LV differ greatly.

T/F: Myocardium has only one fiber type

TRUE

Similar to type I fibers

High capillary density

High number of mitochondria

Striated

What are cardiac fibers connected by

Intercalated discs

What holds cardiac cells together

desmosomes

Gap Junctions

rapidly conduct action potentials

allow for simultaneous contraction of cardiac cells

T/F: There is more muscle mass in right ventricle

FALSE

There is greater muscle mass in left ventricle due to increased force generation (e.g., contraction) needed to pump blood out to the entire body

T/F: 25% of cardiac muscle is mitochondria

TRUE

almost exclusively use aerobic metabolism

Fatty acids, glucose, lactate, amino acids, ketones as fuel

Ischemia (low O2) = bad

Characteristics of skeletal muscle cells

•Large, long, unbranched, and multinucleated

•Intermittent, voluntary contractions

•Ca2+ released from SR

Characteristics of myocardial cells

•Small, short, branched, one nucleus

•Continuous, involuntary rhythmic contractions

•Calcium-induced calcium release

What is the 1st heart sound?

closure of AV valves

What is the 2nd heart sound?

closure of pulmonary and aortic valves

During exercise what happens to systole and diastole timing

A primary decrease in diastole but also a small decrease in systole

Wiggers Diagram

Showcases electrical events of heart cycle

1st part of wiggers

Atrial contraction/ventricular filling

Atria contracts

Ventricles relax

AV Valves open

Semilunar Valves close

2nd part of wiggers

Isovolumetric contraction

Atria relaxes

Ventricles contract

AV Valves close

Semilunar valves close

3rd part of wiggers

Ventricular ejection

Atria relaxes

Ventricles contract

AV valves close

Semilunar valves open

4th part of wiggers

Isovolumetric relaxation

Atria relaxes

Ventricles relax

AV valves close

Semilunar valves close

5th part of wiggers

Atrial relaxation and ventricular filling

Atria relaxes

Ventricles relax

AV valves open

Semilunar valves close

Spontaneous rhythmicity

special heart cells generate and spread electrical signal

•Sinoatrial (SA) node

•Atrioventricular (AV) node

•AV bundle (bundle of His)

•Purkinje fibers

How do electrical signals spread

Gap junctions

What should intrinsic heart rate be

100 bpm

Step 1 of action potential in heart

Action potentials originate in the sinoatrial (SA) node (the pacemaker) and travel across the wall of the atrium (arrows) from the SA node to the

atrioventricular (AV) node.

Step 2 of action potential in heart

Action potentials pass through the AV node and along the atrioventricular (AV) bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum.

Step 3 of action potential in heart

AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches.

Step 4 of action potential in heart

Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls.

What does EKG stand for

electrokardiogram