Physiology - Cardiovascular System #1

what is threshold for an autorhythmic cell?

-40 mV

list 3 results of increased contractility

1. increased stroke volume 2. increased force of contraction 3. increased cardiac output

List 3 thing that affect stroke volume

1. preload 2. contractility 3. afterload

what is the formula for resistance?

1/radius^4

A normal heart rate in an adult at rest is _____ bpm.

75

This area is the only electrical connection between the atria and ventricles.

AV bundle (bundle of His)

which valves are open or closed during isovolumetric relaxation?

AV valves closed; semilunar valves closed

cardiac glycosides slow down the activity of the sodium-potassium pump in cardiac muscle cells. what condition will this treat?

CHF; heart is not beating with enough contractile force to move enough blood; this will increase calcium in the cells; if you slow down the primary active transport, you slow down the secondary active transport; calcium builds up inside the cell and contractile force increases

Why can tetanus NOT occur in myocardial contractile cells?

Ca2+ entry depolarizes the cell and lengthens the refractory period, which prevents the summation of the tension developed from repeated action potentials.

predict what would happen to heart rate (HR), stroke volume (SV), and cardiac output (CO) with decreased heart rate.

Decreased HR, increased SV, and no change to CO

Which cell junction acts as an anchor, holding the cells together as the heart beats?

Desmosome

what is the formula for stroke volume?

EDV - ESV

what happens when an autorhythimic cell reaches threshold?

FAST calcium channels open and calcium rushes into the cell

T/F: One role of the cardiovascular system is to remove wastes from the body.

False

T/F: The expiratory phase of respiration increases stroke volume.

False

The depolarization phase of contractile cells is caused by the opening of what voltage-gated channels?

Fast sodium

Which cell junction allows ions to move across the heart from cell to cell, so that the heart beats as an entire unit?

Gap junction

predict what would happen to heart rate (HR), stroke volume (SV), and cardiac output (CO) with increased sympathetic input.

Increased HR, increased SV, and increased CO

Where are the gap junctions and the desmosomes located?

Intercalated disc

How do pacemaker cells differ from contractile cells?

Pacemakers control heart rate whereas contractile cells generate force of contraction.

What pressure difference causes the aortic semilunar valves to close?

Pressure in the aorta that is greater than left ventricular pressure

In a normal ECG wave tracing, atrial repolarization is hidden by the:

QRS complex

Which wave on the ECG would be wider if the patient had a left bundle branch block?

QRS complex

What happens to resistance, friction, and flow when a blood vessel's diameter increases and the pressure gradient remains unchanged?

Resistance decreases, friction decreases, and the rate of flow increases

what is the equation for CO?

SV x HR

the Frank-Starling law states that _____

Stroke volume increases as end-diastolic volume increases.

The 2nd heart sound occurs during which aspect of the ECG?

T wave

What causes action potentials in contractile cells?

The flow of positive ions from adjacent cells

T/F: Parasympathetic innervation has little effect on ventricles.

True

What pressure difference causes the AV valves to open?

When pressure in the atrium is greater than in the ventricle

What does the P wave of the ECG represent?

atrial depolarization

The intrinsic conduction system consists of _____________ cells that initiate and distribute action potentials throughout the heart.

autorhythmic

the electrolytes in Rigner's solution are required for what?

autorhythmicity

what receptor binds EPI and NE?

beta-1 adrenergic

relate blood flow and radius

blood flow is directly proportional to vessel radius to the 4th power

what has the greatest effect on blood flow?

blood vessel radius

blood flow is directly proportional to what?

blood vessel radius and pressure gradient

what does the term anastomosing mean?

branching

How does the sympathetic nervous system increase stroke volume?

by increasing contractility

describe the plateau phase

calcium channels are open and potassium channels are closed

what happens during the repolarization phase of the cardiac action potential?

calcium channels close; potassium permeabilty increases; potassium leaks out

pressure changes in the cardiovascular system primarily result from?

changes in the force of contraction of the heart

what is the effect of calcium channel blockers that work on L-type calcium channels?

decrease calcium into the cell which has a negative inotropic effect and reduces contractile force

what effect does thrombocytopenia have on viscosity?

decreases blood viscosity

define preload

degree of myocardial stretch before contraction begins; stretch represents the load placed on cardiac muscles before they contract

what is Poiseuille's law?

describes relationship between resistance and viscosity of blood, radius of the blood vessel and length of the blood vessel

Cardiac output is the amount of blood pumped out of ___________ in one minute.

each ventricle

define EDV

end diastolic volume; amount of blood in each ventricle at the end of diastole

define ESV

end systolic volume; amount of blood remaining in the left ventricle after contraction; increased sympathetic activity increases the force of contraction; more blood is squeezed out and less remains in the left ventricle

how does calcium impact the force of contraction?

force of contraction is proportional to the number of crossbridges that are active in the myocardial cells which, in turn, is determined by how much calcium is bound to troponin

Action potentials generated by the autorhythmic cells spread to the contractile cells through what in the membrane?

gap junctions

what affect does NE have on heart rate?

increases rate of depolarization and increasing frequency of action

During what phase of the cardiac cycle does the ventricle contract, raising intraventricular pressure and, thus, closing the AV valves?

isovolumetric contraction

what impact does tachycardia have on EDV?

it decreases it because the increased heart rate reduces the time during which the ventricles can fill with blood; diastole is shorter than normal

why does electrical signaling in the heart begins in the SA node?

it depolarizes the fastest

why is the plateau important?

it lengthens the total duration of the myocardial action potential; prevents sustained contractions (tetanus) which would not allow the hear to relax to fill its chambers with blood

what is the result of the potassium efflux?

it produces repolarization

what effect will ACh have on heart rate?

it will slow the heart rate

A defect in the bicuspid valve would directly affect _____.

left ventricular filling

ventricular filling occurs during what phase of the cardiac cycle?

mid-to-late ventricular diastole

what effect does a calcium channel blocker have on heart rate and contractile force?

negative chronotropic and negative inotropic

what is the effect of parasympathetic input to the heart?

open additional potasium channels in pacemaker cells

what does the reversal of membrane potential trigger?

opening of potassium channels resulting in potassium rapidly leaving the cell (efflux)

viscosity most directly affects what?

peripheral resistance

define systole

phase of heartbeat when heart muscle contracts and pumps blood from chambers into the arteries

define diastole

phase when heart muscle relaxes and allows ch

The pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is caused by decreased efflux of what ion?

potassium

resting cardiac cells are most permeable to what?

potassium

what happens during repolarization?

potassium leaves the cell, ionic pumps actively transport calcium back to the extracellular space; sodium-potassium pump transport sodium out and potassium in to restore ion concentrations to their resting levels

define driving pressure

pressure created in the ventricles; it's the force that drives blood through the blood vessels

what is the result of calcium influx into autorhythmic cells?

produces rapidly rising phase of the action potential (deplolarization) reversing membrane potential

what is thrombocytopenia?

reduction in platelets

Where is the calcium stored in contractile cells?

sarcoplasmic reticulum

The repolarization phase of contractile cells is delayed by the plateau phase. The opening of what voltage-gated channels is responsible for the plateau phase?

slow calcium

what branch of the ANS dominates during exercise?

sympathetic branch

what are voltage gated sodium channel blockers used to treat?

tachycardia; contraction time is decreased

what does the long refactory period in cardiac muscle prevent?

tetanus

what is the role of intercalated discs?

they are the point of communication between cardiac muscle cells; hold cells together

what is the role of the chordae tendineae?

they prevent the valve from being pushed back into the atrium

what might be seen in both a diseased heart and an athlete's heart?

thicker myocardium

define refactory period

time following an action potential during which a normal stimulus cannot trigger a second action potential; no summation occurs

T/F: potassium leak channels are always open

true

what contributes directly to preload?

venous return

During this phase of the cardiac cycle, the pressure in the ventricle increases and forces the semilunar valves open.

ventricular ejection

what happens during the plateau phase of the cardiac action potential?

voltage gated calcium channels open and potassium leaks out; calcium moves slowly into the cell due to its large size; combination of calcium influx (increased calcium permeabilty) and decreased potassium permeability

what happens during depolarization in the cardiac action potential?

voltage gated sodium channels open

define stroke volume

volume of blood pumped per ventricle per contraction

blood vessel length decreases when?

we lose weight