Cardiovascular Flashcards
Arteries everywhere except heart
Carry oxygenated blood. Pressure storers
Veins everywhere except heart
Carry deoxygenated blood. Volume storers
Pulmonary artery
Carries deoxygenated blood from the heart to the lungs
pulmonary vein
carries oxygenated blood from the lungs back to the heart
role of vascular system
partition blood from heart to different organs and tissues What does this allow us to do? 1. Transports waste (urea, kidney function) 2. Thremoregulation - controls blood flow to skin 3. Transport hormones 4. Distribute nutrients 5. Move CO2 and O2
arteries vs veins vs capillaries anatomy
Arteries: Contain the thickest layer of elastic and smooth muscle, allowing them to contract and generate the most pressure.
Veins: Contain a thin layer of elastic so when blood goes in, veins give and you don’t get a lot of pushback - volume storers. Also contain one-way valves to prevent backflow. We don’t worry about backflow in the arteries because the pressure is higher.
Capillaries: Just a thin layer of endothelium, maximizing gas exchange.
Anatomy of the heart and blood flow
–Blood enters heart on the right side via superior vena cava (collects blood from the top of body) and inferior vena cava (collects blood from lower part of body)
–Blood fills the right atrium passively. When pressure in right atrium is large enough, it flows through the tricuspid valve into the right ventricle.
–Right ventricle contracts (ventricular systole), and blood flows through the pulmonary valve to the lungs
–Blood is oxygenated in the lungs
–Blood returns to the left side of the heart via the pulmonary veins and collects in the left atrium
–When pressure in the left atrium is greater than pressure in the left ventricle, blood flows down into the left ventricle through the bicuspid valve
–Left ventricle contracts –> bicuspid valve closes and aortic valve opens
–Oxygenated blood flows out of aorta to the rest of the body
Superior vena cava
carries deoxygenated blood from the upper part of the body to the right atrium
inferior vena cava
carries deoxygenated blood from the lower part of the body to the right atrium
pulmonary valve
blood must flow from the right ventricle up through the pulmonary valve to reach the veins
bicuspid valve
separates the left atrium from the left ventricle
Aortic valve
blood flows from the left ventricle up through the aortic valve to the rest of the body
tricuspid valve
separates the right atrium from the right ventricle
Right ventricle vs. left ventricle
The left ventricle is much larger because it needs to generate enough pressure to pump blood out to the whole body, while the right ventricle only needs to pump blood to the lungs.
chordae tendineae
muscles that stabilize the AV valves to help keep them closed and prevent backflow
coronary artery and coronary vein
provide the heart’s own circulation
ventricular systole
ventricular contraction
ventricular diastole
ventricular relaxation
Cardiac output
=Heart Rate x Stroke Volume
= beats/min x mL/beat
=mL/min
What does our closed circulatory system with the heart allow us to do?
- Variable cardiac output - we can couple cardiac output to metabolic rate
- We can partition blood
How do we make the heart contract?
We use electrical signals. Mechanical activity follows electrical activity. We have 2 types of cells for this:
- Conducting fibers
- Contracting fibers
Conducting fibers
specialized muscle cells that conduct electrical activity/information and generate action potentials that drive contractile cells
Contracting fibers
muscle cells that do the contraction of the heart - make up the majority of heart cells
Electrical pathway in the heart
- SA node sets the baseline rhythm and needs no outside impulse
- Spreads to the AV node, where the signal slows to let muscle contraction of the atriums catch up
- Moves through Bundle of His fibers down to the bottom of the heart
- From bottom of heart is carried back up via Purkinje fibers, which triggers contraction of the ventricle
**Contraction of ventricle happens from the bottom up to get all the blood bacvk to the valves
Gap junctions
Allow the electrical signal to spread through the heart. This means not every cardiac cell needs nervous input
myogenic
the heart is myogenic, which means it has its own pacemaker (the SA node)
Stroke volume
=End diastolic volume - residual volume
–End diastolic volume = the blood in the ventricles just before they contract. This is the amount of blood in the ventricles when they are full
–Residual volume = the blood in the ventricles after contraction. We have some blood left in there, which gives us a reserve of blood.
–Stroke volume is the amount of blood pumped from the left ventricle per beat
Ejection function
=Stroke volume/End diastolic volume
cardiac work
the area under the PV diagram of the heart
Preload vs. Afterload
Regulation of cardiac system
- Neural regulation
- Baroreceptors/Chemoreceptors
neural regulation of cardiac system
Occurs via the autonomic nervous system using both the parasympathetic and sympathetic
Parasympathetic nervous system control of cardiac system
–Parasympathetic nervous system - “rest and digest”
–The vagus nerve is part of the parasympathetic nervous system and innervates SA node and AV node
–Decreases Heart rate (negative chonotropic effects)
–Decreases force of contraction (negative inotropic effect)
–Uses acetylcholine as neurotransmitter
–Overall result: decrease in cardiac output
chonotropic effects
–Change the heart rate
–Positive chonotropic effect = increase heart rate
–Negative chontropic effect = decrease heart rate
Inotropic effect
–effects strength of contraction (of heart)
–Positive inotropic effect = increases strength of contraction
–Negative inotropic effect = decreases strength of contraction
Sympathetic Nervous system control of cardiac system
–“fight or flight”
–Positive chonotropic effect –> increased heart rate
–positive inotropic effect–> increased force of contraction
–Overall: increases cardiac output
–Primary neurotransmitter: norepinephrine
Cardiac Output Regulation
- Baroreceptors - found in carotid and aorta and measure blood pressure. If blood pressure drops, baroreceptors send info to medulla, medulla increases sympathetic activity and decreases parasympathetic activity to increase cardiac output
- Chemoreceptors - measure blood gases on arterial side of medulla. If pO2 drops or pCO2 increases, medulla increases sympathetic response and decreases parasympathetic response –> increased respiratory minute volume–> increased cardiac output
- Exercise - can override autonomic nervous system and increase cardiac output
what happens when you increase heart rate and thus cardiac output?
Period of diastole will shorten and there’s an increase in venus return.
Frank Starling Law
–The force of contraction of heart is proportional to stretch of myocardial fibers
–If you get more blood in chambers, the fibers will stretch more, and there will be a greater force of contraction
Venous pressure and flow
–Cardiac output relies on venous return and venous return relies on venus pressure
what controls venus pressure
- Sympathetic veno constriction - sympathetic nervous system releases epinephrine that acts on veins as well as heart. In the veins, epinephrine causes smooth muscle contractions which increase venus pressure and increase blood flow back to heart
- Skeletal muscle pump - during exercise you contract muscle –> constricts blood vessels –> increase venus pressure –> blood back to heart
4 methods by which materials cross capillary walls
- pinocytosis - proteins
- diffusion or transport through capillary cell membranes - done by O2 and CO2 and small lipid-soluble molecules
- movement through pores in the cells called fenestrations - proteins
- movement through the spaces between the cells - done by water-soluble substances
