3. Circulatory Unit: Vessels, Heart Physiology, Blood Pressure Flashcards
What are the 3 main types of blood vessels?
Arteries, veins and capillaries
What is the function of arteries?
To carry oxygenated blood AWAY from the heart
Describe the general anatomy of the arteries?
The arteries have a thick tunica media to withstand high blood pressure from the heart
The tunica media is the middle layer of the artery wall, it contains elastic fibres as well to accommodate for constriction/dilation
What is the function of veins?
Usually carry deoxygenated blood TOWARDS the heart
What is the general anatomy of the veins
Veins have thinner walls and valves to prevent back flow due to low pressure
What is the function of the capillaries and the general anatomy
Site of exchange between blood plasma and cells.
Extremely thin walls (only tunica media)
Vary in diameter and permeability depending on location
What is the conduction system of the heart?
SA NODE -> AV NODE -> AV BUNDLE -> PURKINJE FIBRES
What is the purpose for the conduction system
To ensure coordinated contraction of the heart chambers
atria contract at the same time then a delay then ventricles contract
What is the delay in a heartbeat?
The delay is due to the conduction system, it allows for the aria to fully empty blood into the ventricles before allowing the ventricles to contract
Why is the conduction system important?
It allows the heart to contract rhythmically and efficiently without needing input from the nervous system.
What happens during one heartbeat
- Blood enters atria
- SA node triggers atria to contract
- Blood moves to ventricles
- Ventricles contract
- AV valves close (lub) semilunar valves open
- Semilunar valves close (dub)
What does an ECG measure? (Describe the wave thing)
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
Atrial repolarization occurs during qrs complex but the charge from the ventricles depolarizing hides it
What is heart contractility?
The ability of the heart muscle to contract with force. Heart contractility determines how much blood the heart pumps per beat.
What factors influence heart rate?
- Autonomic Nervous System
– Sympathetic: ↑HR, ↑HC Parasympathetic: ↓HR - Hormones
– Epinephrine, norepinephrine: ↑HR, ↑HC - Ions in blood (can affect conduction system)
– Na+, K+: ↑ HR, ↑HC Ca2+: ↑HR, ↑HC - Body Temperature
– High Temp: ↑HR Low Temp: ↓HR, ↓HC
What are the major arteries of the upper body
Arch of aorta (aortic arch), brachiocephalic trunk(branches into right subclavian and right common carotid), left common carotid, left subclavian
What are the major arteries of the lower body
Descending aorta, hepatic artery, renal artery, mesenteric artery, left and right common iliac arteries, left and right femoral arteries
What are the major veins of the upper body
Superior vena cava, right brachiocephalic (branches off into right subclavian, right jugular) left brachiocephalic (branches off into left jugular and left subclavian)
What are the major veins for the lower body
Inferior vena cava, renal vein, hepatic vein, hepatic portal vein (serves gastric vein, mesenteric vein) right and left common iliac vein, right and left femoral vein
What is blood pressure?
The force exerted by blood on the artery walls
What is the difference between systolic and diastolic pressure?
Systolic: pressure during ventricular contraction (~120)
Diastolic: pressure during ventricular relaxation (~80)
What is hypotension
Blood pressure that is lower than average systolic is less than 100
What is hypertension
Blood pressure that is higher than the average systolic/diastolic is graters that 140/90
What factors increase blood pressure
Increase in cardiac output, decrease in compliance of arteries, increase in blood volume, decrease in vessel diameter, increase in viscosity
How is blood pressure regulated?
Autonomic nervous system (can adjust heart rate and vessel diameter)
Autoregulation (local tissue response via vasoconstriction/vascodilation)
Endocrine system (hormones like aldosterone and epinephrine)
