Cardiovascular System Flashcards
What is blood pressure?
The pressure exerted by the blood, against the blood vessels
What is the name of the receptors that detect blood pressure? and where are they found predominantly?
Baroreceptors, found in the carotid sinus and aortic arch
Describe the autonomic pathway that regulates blood pressure (6)
- Reduced stretch detected by baroreceptors
- Signal sent to medulla oblongata
- This causes increased sympathetic tone of the heart and vessels
- Heart rate increases, and so does contractility, so stroke volume increases
- Increased systemic vascular resistance
- Increased mean arterial blood pressure
What is the difference between dehydration and hypovolaemia?
Dehydration is a loss of fluid intracellularly and extracellularly, whereas hypovolaemia is loss of fluid from the vessels.
How does hypovolaemia affect heart function?
- Reduced stroke volume
- Reduced preload
- Reduced mean arterial pressure
- Reduced tissue oxygen delivery
What system regulates short term blood pressure changes?
Autonomic
What is a chronotropic effect?
A change the heart rate
What is an inotropic effect?
A change in force of contraction
State the mechanisms that maintain blood pressure in the long term (4)
- RAAS
- ADH
- ANP - atrial natriuretic peptide
- Paracrine endothelial cell signalling
How does the body respond to hypovolaemia? (4)
- ADH secretion
- RAAS
- Catecholamine secretion
- Increased sympathetic tone of the heart and vessels as a response to chemoreceptors and baroreceptors
What effects does ADH have on the body?
Causes the kidneys to retain more water, and so increases blood volume
What is the RAAS and what effect does it have on the body? (6)
The kidneys secrete renin which causes angiotensin II levels to rise which cause vasoconstriction, enhanced sympathetic tone on heart and vessels, vasopressin release, thirst centre activation, Increased sodium and water reabsorption.
What effect does catecholamine have on the body?
Reinforces sympathetic activity on the heart and vessels
What effect does Atrial natriuretic peptide have on the body?
Causes vasodilation and makes the kidneys to excrete more water, so decreases blood pressure.
What is the main mechanism by which venous tone is regulated?
Autonomic nervous system via sympathetic fibres innervating vascular smooth muscle.
Blood is sent mainly in parallel in the body, what effect does this have on the blood reaching the abdominal organs?
The organs receive fresh oxygen rich blood, not second hand blood.
What is a portal vein?
A vein that connects two organs so that the second organ receives second hand blood from the other
What is the importance of the portal system?
It allows solutes to be transported from one place to another without diluting the general ciculation.
Give an example of a portal vein and its role
The hepatic portal vein flows from the GI tract to the liver to filter newly absorbed substances before they reach the general circulation.
What is the importance of anastomosing vessels?
They mean that if one vessel is blocked, there is another route to bypass the blockage.
What are the three anatomical layers of blood vessels?
- Tunica intimia
- Tunica media
- Tunica externa
What is the role of the arteries and how is the structure suited to its function? (2)
- Role is to carry blood under high pressure from the heart to the tissues.
- They contain lots of elastin and collagen to support them under the high pressure.
What is the role of the arterioles and how is the structure suited to the function? (2)
- Control the flow of blood by constricting and dilating to ensure that it is at an appropriate pressure to not damage the capillaries.
- They therefore contain lots of smooth muscle.
What is the role of the veins and how is the structure suited to the function? (3)
- Function is to carry blood from the tissues to the heart. —–Contain some smooth muscle to allow contractions to force the blood back to the heart
- Also use their valves for this.