bio 225 exam 4 circulatory

fluids flow down pressure gradients (high → low pressure), how larger animals move fluid through their bodies

Q = ∆P/R

due to friction, opposes fluid movement; R = 8ηL/πr⁴

Q = ∆Pπr⁴ / 8ηL

oxygen, carbon dioxide, nutrients, waste products, immune cells, signaling molecules

I = V / R

by increasing pressure of the fluid in one part of the body

as radius increases, resistance decreases, and vice versa

• unbranched and rigid tubes

• uniform and simple flow

• steady flow

• total R is the sum of each R value

• each section between each resistor in a blood vessel has its own pressure

• to find the total R, add the inverse of each R value together (1/R)

• pressure before branching is higher than pressure after branching

flow is uniform at all points within a closed circuit

V = Q / A

velocity is NOT uniform at all points within the circuit

at the circulatory system’s capillary beds, where total cross-sectional area is highest

1 and 2

2 and 5

2 and 4

pulmonary (heart-lungs) and systemic (heart-body)

• deoxygenated blood enters the right atrium via the vena cava, then goes into the right ventricle and is pumped to the lungs via the pulmonary artery

• oxygenated blood enters from the lungs to the left atrium via the pulmonary veins, then goes into the left ventricle and is pumped to the body via the aorta

• arteries carry blood from the heart

  • arterioles are smaller branches of an artery

• veins carry blood towards the heart

  • venules are smaller branches that combine to make up a vein

largely made up of myocardium, with endothelium on the inside and pericardium on the outside (with pericardial fluid in the pericardial cavity)

this multi-layered section of the heart protects it from friction while it’s beating

fish have a spongy myocardium, which allows blood from heart chambers to get to the myocardium and deliver nutrients

relaxation of the heart, negative pressure, blood flows in

contraction of the heart, positive pressure, blood flows out

1. ventricular diastole - atria pressure > ventricular pressure, and av values open. during total relaxation, 70% of the blood flows from the atria to the ventricles, called passive filling

2. atrial systole - the atria contract, forcing the remaining 30% into the ventricles

3. ventricular systole - the atria relax while the ventricles contract (and av valves close), called isovolumetric contraction (increase in pressure until the semilunar valves open)

4. ventricular systole - when ventricular pressure is high enough, semilunar valves open and ventricle contraction causes ejection of blood into arteries

5. ventricular diastole - the ventricles relax, called isovolumetric relaxation (semilunar valves are closed while ventricular pressure decreases)

they are passive, meaning no muscles or ATP are used, they only respond to pressure gradients

atrial → ventricular, right - tricuspid, left - bicuspid/mitral, weak enough to open with pressure but not backwards (prolapse), chordae tendinae and papillary muscles prevent prolapse

ventricular → out, pulmonary valve (to lung) and aortic value (to body), weak enough to open from ventricular contraction but withstand return pressure

• the SA node sends out an action potential and it goes to the AV node via junctional fibers

• the signal travels from the AV node to the AV bundle, aka bundle of His, and then splits down the left and right bundle branches

• the bundle branches split off into purkinje fibers and the signal travels into the walls of the ventricles, causing them to contract

• it has high Na+ permeability and low K+ permeability, which causes slow, continuous depolarization

• this pacemaker potential causes the SA node to reach its threshold and trigger an action potential

• after the SA node repolarizes, the pacemaker potential occurs again

the “funny current” through the funny channel — a non-selective cation channel that opens at hyperpolarized voltages and closes at depolarization, mostly Na+

the SA node essentially has an intrinsic action potential frequency, slowly getting to threshold, then action potential, then repeat

• a special kind of K+ channel called a transient channel, which is open only for a short time and causes a small amount of repolarization before closing again

• Ca2+ is flowing into the cell at the same time, causing the stable plateau

• P-wave shows the depolarization of atria (contraction)

• QRS complex shows depolarization of ventricles (contraction) and repolarization of atria (relaxation)

• T-wave shows repolarization of ventricles (relaxation)

they control the pacemaker potential in the sa node

• controlled by the sympathetic and parasympathetic nervous system

  • sympathetic system creates faster depolarization, limits the funny current, while the parasympathetic system creates longer depolarization, increasing the funny current

• acetylcholine activates both muscarinic receptors of autorhythmic cells

• K+ leaves, Ca2+ stops entering, cell hyperpolarizes

• more time needed to depolarize, HR decreases

• norepinephrine and epinephrine activate beta receptors of autorhythmic cells

  • adenylate cyclase converts ATP to cAMP which contributes to ions entering cell

• Na+ and Ca2+ both enter

• depolarization increases, HR increases

the pressure caused by ventricular ejection

CO = HR x SV

• norepinephrine or epinephrine binds and changes the shape of beta receptors

  • adenylate cyclase converts ATP to cAMP

  • cAMP activates protein kinase A

• protein kinase phosphorylates L-type Ca2+ channels so Ca2+ enters the cell, stimulating contraction

• protein kinase phosphorylates Ca2+ channels on SR, Ca2+ moves to cytoplasm and stimulates contraction

• protein kinase phosphorylates myosin, stimulating contraction

• protein kinase phosphorylates sarcoplasmic Ca2+ ATPase, speeding removal of Ca2+ from cytoplasm, decreasing relaxation time

• increasing contraction force increases stroke volume, which increases cardiac output

highest arterial blood pressure, from ventricular contraction

lowest arterial blood pressure, from ventricular relaxation?

average blood pressure in arteries, 2/3 DP + 1/3 SP, MAP = CO x TPR

left ventricle → arteries → arterioles → capillaries → venules → veins

they detect a rise in blood pressure, signal to the cardiovascular control center of the medulla, and enact a negative feedback loop