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.
what is the function of the capillaries and how is the structure suited to the function? (3)
- Function is exchange
- Therefore blood pressure and speed must be low
- As a result they don’t need to be very thick
Describe the relationship between vessel diameter and vascular resistance. (3)
- Inverse relationship
- R=1/R(radius)^4
- Small change in diameter results in massive resistance change
List factors that effect cardiac output (8)
- Heart rate which is influenced by:
- Autonomic innervation
- Hormones
- Fitness
- Stroke volume which is influenced by:
- Heart size
- Contractility
- Blood pressure
How does the body respond to a decreased cardiac output? (5)
- Low cardiac output causes Low blood pressure
- Decreased stretch detected by baroreceptors
- Increased CO2 detected by chemoreceptors
- Heart rate increase, peripheral vasoconstriction, RAAS
- Blood pressure and so cardiac output increase
What are the clinical signs of hypotension? (5)
- Legarthy
- Fainting
- Increased thirst
- Pale gums and mucous membranes
- Heart problems
State the differences between foetal circulation and adult circulation and why they are there. (4)
- Ductus arteriosus to bypass pulmonary circuit as it is not needed
- Foramen ovale to bypass the pulmonary circuit as not needed
- Ductus venosus to bypass the liver as not needed
- receives oxygen from placenta as lungs are collapsed due to the foetus breathing amniotic fluid
What changes occur to the circulatory system at partition? (3)
- Placenta detaches so a breath is taken to inflate lungs and get the oxygen from there
- Increased pulmonary resistance causes septum premium and secundum to come together to close the foramen ovale
- Prostaglandin levels fall and noradrenaline levels rise and cause vasoconstriction to help to closure of the ductus venosus and ductus arteriosus
State the mechanisms that control the changes in circulation at birth (3)
- Detachment of placenta and increased pO2 causes prostaglandin levels to fall
- Reduced prostaglandin reduces vasodilation
- Loss of placenta increases vascular resistance allowing shunts to close.
How long does it take for the ductus venosus, ductus arteriosus, and foramen ovale to close? (3)
- Minutes
- Hours
- Hours
State 7 congenital cardiac diseases. (CCD)
- Atrial septal defect
- Ventricle septal defect
- Persistant atrioventricular canal
- Tetrology of fallot
- Persistant truncus arteriosus
- Transposition of great vessels
- Dextrocardia
Clinical signs of CCD (7)
- Cyanosis
- Exercise intolerance
- Dyspnea
- Heart murmurs
- Coughing
- Fainting
- Fluid buildup in abdomen (heart failure)
What are the two types of atrial septal defect?
- Ostium primum defects as the septum premum doesn’t fuse with AV cushions leaving the formamen primum still present
- Ostium secundum defect as the septum doesn’t reach full growth leaving a larger fossa ovale
What causes a persistent atrioventricular canal?
Dorsal and ventral AV cushions do not fuse, leaving a gap between atria and ventricle
What factors are released by the endothelium that influence vasomotor tone? (6)
- Angiotensin II
- Nitric oxide
- Intracellular calcium
- Prostaglandin
- EDHF
- Endothelin
Name 2 endothelial derived factors that cause vasoconstriction
Endothelin and angiotensin II
Name 2 endothelial derived factors that cause vasodilation
nitric oxide and prostaglandin
Name 2 functions of endothelial cell signalling
Important in development so neighbouring cells can notify nearby cells of their function, and control of vasomotor tone and
State the three main classes of surface cell receptors
- Ion channels
- G-protein linked
- Enzyme linked
How does a G-protein linked channel work? (3)
- A ligand binds to the receptor on the outside of the cell
- G protein activated on the inside of the cell
- Internal response involving activation of enzymes and ion channels
How does an enzyme-linked Channel work?
- Ligand binds to a receptor
- Receptor has a transmembrane element
- This activates an internal enzyme
What are the three mechanisms by which oedema can occur and give examples of causes
- Increased outward filtration due to increased blood pressure
- Decreased inward absorption due to low protein count
- Leaky vessels due to inflammation or vasculitis
Describe how lymph is formed (7)
- At the arterial end there is net hydrostatic pressure outwards due to contraction of the left ventricle
- There is a net colloid pressure inwards due to plasma protein concentration
- Hydrostatic pressure outwards is higher than colloid pressure inwards so there is an outward filtration and tissue fluid forms
- At the venous end the hydrostatic pressure falls due to resistance
- The colloid osmotic pressure increases as there has been a loss of fluid from the blood
- Hydrostatic pressure outwards is lower than colloid osmotic pressure inwards so there is a net inward absorption and plasma forms
- Hydrostatic pressure outwards overall is higher than colloid osmotic pressure inwards overall so tissue fluid forms
What are the 4 Starlings forces
- Capillary hydrostatic pressure
- Interstitial colloid osmotic pressure
- Interstitial fluid hydrostatic pressure
- Plasma colloid osmotic pressure
Define colloid osmotic pressure
A type of osmotic pressure created by proteins in the plasma
What causes the S1 sound?
Closure of the mitral and tricuspid valves
What causes the S2 sound?
Closure of the aortic and pulmonary valves
Which heart sound marks the start of systole?
S1
Which heart sound marks the end of systole?
S2
How can you measure systole and diastole using the heart sounds?
Systole is the time between S1 and S2, diastole is the time between S2 and the next S1