Physiology exam 3

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Biology

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235 Terms

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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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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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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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Cross bridge cycle is initiated when
Excitation contraction coupling increases Ca2+ and binding sites on actin are exposed
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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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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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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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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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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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To relax….
Ca2+ has to be removed using Ca-ATPase pump
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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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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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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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P wave
Atrial depolarization
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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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Bradycardia
Cardiac rate slower than 60 beats per minute
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Tachycardia
Cardiac rate faster than 100 beats per minute