Physiology exam 3

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Function of the muscular system

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Biology

235 Terms

1

Function of the muscular system

Movement

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Muscles are classified into 3 groups based on

Characteristics and function

Smooth, cardiac, skeletal

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Term for a single cell

Muscle fiber

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Skeletal muscle

Moving muscle

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Smooth muscle

Moving components, usually within a tube

Controlled by brain

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Cardiac muscle

Pumping blood

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Thick filaments are made up of

Myosin

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Polypeptide chains form

Two globular heads and a tail

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Crossbridge

Area that exerts force on the thin filament

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Heads contain

ATP binding sites and actin binding sites

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Thin filaments are made up of

Actin and troponin and tropomyosin

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12

Thin filaments have an important role in

Regulating contractions

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Tropomyosin

Overlaps binding sites blocking cross bridges

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Troponin

Ca2+ binding to troponin regulates skeletal muscle contraction

Moves tropomyosin away and allows myosin to interact with the actin

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Excitation-contraction coupling occurs

At axon terminal of neuron

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Motor end plate is

ESPS on muscle fiber

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Ca2+ enables…

ACh to be released across the space between axon terminal and motor end plate

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ACh binds to

Nicotininc ACh (muscle fibers) receptors

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Nervous system stimulates

Muscle fibers

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Action potential in muscle fibers

Contract

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Action potential starts in

Muscle cell

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22

T-tubule voltage gated calcium channel

Open when membrane is depolarized

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Relaxation occurs as

Ca2+ is pumped into Sarcoplasmic reticulum when an action potential stops

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24

Cross bridge cycle is initiated when

Excitation contraction coupling increases Ca2+ and binding sites on actin are exposed

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25

Each cross bridge goes through its cycle ____ of other cycles

Independently

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Step 1 in cross bridge cycle

The active site on actin is exposed as Ca2+ binds to troponin

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Step 2 in cross bridge cycle

Myosin head forms a cross bridge with actin

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Step 3 in cross bridge cycle

During the power stroke, myosin head bends and adp and phosphate is released

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Step 4 in cross bridge cycle

A new molecule of atp attaches to the myosin head causing the cross bridge to detach

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Step 5 in cross bridge cycle

ATP hydrolyzes to adp and phosphate, which returns the myosin to the cocked position

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The myosin head serves as a….

Myosin ATPase enzyme

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What is happening in step one and two of the cross bridge cycle

Energy present excitement, ca2+ concentration needs to increase and bind troponin and tropomyosin to move to bind myosin and actin

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Release of phosphate upon binding creases a change on myosin head to produce a

Power stroke

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34

What is happening in step three and four of cross bridge cycle

Binding actin and myosin creates a release of phosphate

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After the power stroke….

Adp is released and a new atp binds, to make myosin release actin

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What is happening in step five and six of cross bridge cycle

“Resetting”

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Filaments do not change length but they….

Slide

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38

Smooth muscle

Undergo changes in volume with accompanying changes in lengths of the smooth muscle fibers

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Examples of smooth muscle

Stomach, intestine, blood vessels

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Smooth muscle cells have a ___ nucleus

Single

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41

Nerves are part of the ____ division instead of somatic

Autonomic

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In smooth muscle….

Thick and thin filaments are not organized into myofibrils

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In smooth muscles, calcium binds to….

Calmodulin

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Pacemaker cells

Action potential spontaneously in absence of neuronal or hormonal input

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Depolarization opens

Voltage gated ca2+ channels

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Prolonged stimulation holding ca2+ concentrations is called

Latch state

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Latch state

Muscles hold tension for long periods

Ex. Sphincter muscles of GI tract

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48

Two sources of Ca2+ that contribute to the rise of cytosol in ca2+ in smooth muscle

  1. Sarcoplasmic reticulum

  2. Extracellular ca2+ enters the cell through plasma membrane

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49

To relax….

Ca2+ has to be removed using Ca-ATPase pump

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50

Cellular structure of cardiac muscle

Striated using sliding filament mechanism

Arranged like smooth muscle

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Myocardium

Contracts fully every time its stimulated

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Cells are linked by

Gap junctions

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Gap junctions

Spread currents quickly

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Autonomic nervous system hormones and neurotransmitters modulate

Amount of ca2+ released

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Heart cannot exhibit

Summation and tetanus due to refractory period and fulling heart

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Three main functions of the cardiovascular system

Transportation, circulation, protection

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Transportation

O2 and co2, products of digestion, waste

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Regulation

Hormones, temperature (cycling blood through deep to surface vessels)

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Protection

Clotting and immune system

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Cells of cardio

Myocardial cells, node (pacemaker) cells, erythrocytes, endothelial cells

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Circulatory system is impacted by which systems

Endocrine, nervous, respiratory, Kidneys

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Arteries

Away

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Veins

In

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Systemic

Arteries carry oxygenated blood and veins carry deoxygenated blood

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Pulmonary

Carry deoxygenated blood to the lungs and the pulmonary veins vary oxygenated blood to the heart

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Atari empty into _____

Ventricles

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Atrioventricular valve (AV)

Permits blood flow from atrium to ventricles but not backwards

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Left AV/mitral

Bicuspid

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Right AV

Tricuspid

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Pulmonary valve

Right ventricle to pulmonary trunk

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Aortic valve

Left ventricle to aorta

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Conducting system

Special cells in electrical contact with cardiac muscle cells via gap junction

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Conducting system functions

Initiated heartbeat and spreads action potential

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Signal starts in the

SA node

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SA node is located in

Right atrium

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Discharge rate of the SA node determines

Heart rate

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Action potential jumps from cell to cell via

Gap junctions

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Action potential passage through AV node is

Slow

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After AV node is excited…

Action potential moves down the septum to the bundle of His

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AV node and bundle of his

Separates atrial and ventricular contraction

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Purkinji fibers

Spread the potential quickly throughout the ventricles causing them to depolarize together

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Slow predictable depolarization is called

Pacemaker potential

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K+ channels

Gradually closing from previous action potential

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HCN channels

Open in response to hyperpolarization and Na+ enters causing spontaneous depolarization

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HCN channels also called

Funny channels

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86

T (transient) type CA2+

Provide final depolarizing boost

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Ca2+ influx through

L (long lasting) type voltage gated channel

Long action potential

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L type gated channels located in

Sarcoplasmic reticulum

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K+ opens =

Repolarization

Opens because of change in voltage

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90

Change in heart rate can be because of

Change in concentration, change at receptor (beta blockers)

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Voltage gated Na+ open

Depolarization

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Transient K+ channels and L type Ca2+ channels…

Open slow and balance

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A long refractory period….

Prevents summation and tetanus

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A long refractory period is almost as long as…

Contraction itself

Prevents re-excitation during contraction

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95

P wave

Atrial depolarization

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96

Qrs complex

Ventricular depolarization

Path of depolarization differs and currents in the fluid change direction accordingly

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T wave

Ventricular repolarization

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Atrial repolarization typically….

Does not register

Happens at same time as QRS complex

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99

Bradycardia

Cardiac rate slower than 60 beats per minute

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100

Tachycardia

Cardiac rate faster than 100 beats per minute

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