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
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
What are the three main types of heart murmur?
Systolic, diastolic and continuous
How can you differentiate between each type of heart murmur?
Systolic occurs between S1 and S2, Diastolic occurs between S2 and S1, and a continuous murmur occurs throughout systole and diastole
How does heart disease affect cardiac output?
Cardiac disease will cause a lower cardiac output because the heart isn’t as efficient
How does the sympathetic nervous system affect cardiac function in general terms?
It causes positive chronotrophy, positive isotrophy, positive dromotrophy and vasoconstriction
What is the function of the circulatory system? (4)
- Homeostasis
- Maintaining pressure
- Protection (carries white blood cells)
- Transports nutrients
Why is a dual circulatory system needed in mammals? (3)
- Blood needs to be pumped at low pressures to the lungs
- blood needs to be pumped at high pressures to the body
- a dual circuit allows both a pulmonary circuit and a systemic circuit to allow different pressures
Describe the structure of the cardiac skeleton (3)
- Outer parietal layer
- pericardial cavity
- inner visceral layer which is continuous with the epicardium
What is the role of the chord tendineae?
To connect the valves to the papillary muscles
State the 4 valves, their positions, and number of cusps
- Mitral valve between LA and LV, 2
- Tricuspid valve between RA and RV, 2
- Aortic between LV and aorta, 3
- Pulmonic between RV and pulmonary artery, 3
How many chambers does a fish heart contain?
2
Are cardiomyocytes striated or not?
Striated
Give three structural features of cardiomyocytes
- Contain desmosomes
- lots of mitochondria
- Contain T-tubules
How do caridomyocytes respond to injury?
They can increase in size but not in number
How is resting potential maintained in a cardiomyocyte? (5)
- K+ influx down electrochemical gradient
- K+ efflux down conc gradient
- Na+/K+ ATPase pump - 3Na+ out 2K+ in
- Na+/Ca+ antiporter - 3N+ In Ca2+ out
- Ca2+ ATPase pump - Ca2+ efflux
Why does a cardiac cell have a resting negative charge?
Anions in the cell usually proteins which can’t leave
How is a cardiac cell depolarised? (6)
- Influx of Na+/Ca+ through gap junction from neighbour
- Threshold of -70mv causes fast Na+ channels to open
- Na+ influx
- Threshold of -45mv causes T-type Ca2+ channels to open
- Threshold of -35mv causes L-type Ca2+ channels to open
- Positive feedback causes more and more Na+ channels to open until TMP reaches +10mv
How is a cardiac cell repolarised? (7)
- Na+ channels close as they are time sensitive
- Transient outward channels open and there is a K+ efflux
- This causes incomplete repolarisation as L-type Ca2+ channels are still open so there is a Ca2+ influx
- Plateau phase occurs os Ca2+ influx balances K+ efflux
- Ca2+ influx slows a concentration gradient reduces
- K+ efflux exceeds Ca2+ influx and rapid repolarisation occurs during which L-Type Ca2+ channels close
- Resting potential of -90mv reached
What is the all or nothing principle of an action potential?
An action potential cannot be formed unless threshold is reached. once threshold is reached the complete action potential is formed
What is the absolute refractory period?
The period in which it is impossible for another action potential to be formed as sodium channels are closed
What is the relative refractory period?
The time in which it is not impossible for an action potential to be formed as some sodium channels are open, but a very strong stimulus must be applied.
How are different potential differences achievable across a membrane? (3)
- Cell Is impermeable to some ions like large organic ions
- membrane contains channels that open at different thresholds
- permeability of K+ is higher than other ions
Describe the physiological mechanisms by which the Sympathetic nervous system affects heart rate (6)
- Sympathetic nerves release noradrenaline at the SAN and the whole myocardium
- This works at beta receptors
- It causes K+ channels to open sooner and increases Ca2+ entry
- this increases the rate of drift to threshold
- resulting in higher stronger action potentials
- causing stronger quicker contractions
Describe the physiological mechanisms by which the Parasympathetic nervous system affects heart rate (6)
- Parasympathetic nerves release ACh at the SAN + AVN
- Decreasing rate of drift to threshold
- causing the SAN to decrease in rate and the AVN to conduct more slowly
What is the affect of the SNS on cardiac action potentials and the refractory period?
Increases rate of action potentials and shortens refractory period
What is the affect of the PNS on cardiac action potentials and the refractory period?
Decreases the rate of action potentials and lengthens refractory period
What structure electrically insulates the ventricles?
Anulus fibrosus
What is the role of the pukinje cells?
Spreads the electrical impulse from the AVN to the ventricles, it ensures that they contract simultaneously
What classes of drugs can be used to effect hear rate/rhythm? (7)
- Beta-blockers
- muscarine agonists
- muscarine antagonists
- sodium channel blockers
- potassium channel blockers
- calcium channel blockers
- Cardiac glycosides
What is dysrhythmia?
An abnormal rhythm of the heart due to damage to cardiac tissue or stretch.
What is the role of cardiac glycosides?
Increase contractility of the heart
Give an example of a cardiac glycoside
digoxin
Give an example of a calcium Chanel blocker
Verapamil
Give an example of a potassium channel blocker
solatol
Give an example of a sodium channel blocker
Lidocaine
Give an example of a muscarine antagonist
atropine
Give an example of a muscarine agonist
Pilocarpine
Give an example of a beta blocker
propranolol
Describe the frank/starling mechanism?
It describes the fact that the more the heart muscles are stretched to more the will contract, so the more blood that passes through the heart the more it will contract
What is preload?
The extent of which the heart muscles are stretched before systole
What is afterload?
The force in which the ventricle contracts to eject the blood during systole
What is cardiac output?
The volume of blood pumped by the heart per minute
What is pulse pressure?
The difference between systolic and diastolic pressure
What is stroke volume?
The amount of blood pumped by the left ventricle per contraction
What is arterial compliance?
The ability of the arterial walls to expand and contract passively with changes in pressure
What is ejection rate?
How much blood is pumped by a chamber during a contraction
State the Frank/staling mechanism
Stroke volume of the heart increases in response to an increase in the volume of the blood in the ventricles, before contraction, when all other factors remain constant
What is the physiological mechanism behind Frank/staling law?
An increases in preload increases the sarcomere length which will increase the tension and exposure of myosin and actin up to a certain limit
Why will frank/starlings law only work until a certain point?
too much stretch and tension begins to decrease again
What is contractility?
The intrinsic ability of the heart muscle to generate force
What factors are plotted in a frank/starling curve?
stroke volume on the y axis and preload on the X
What does a general frank/staling curve look like?
general positive gradient the levels off and then starts to decline
What is the mathematical relationship between mean arterial pressure, cardiac output, and total peripheral resistance
arterial pressure = cardiac output X total peripheral resistance
How does preload affect cardiac output?
increased preload increases cardiac output
Explain how afterload affects cardiac output? (4)
- increased afterload means reduced fibre shortening velocity
- This reduces rate of ejection
- more blood is left in the ventricle at the end of systole
- cardiac output is reduced
What affect would increased venous return have on stroke volume?
Increase venous return causes increase preload causing increased contractility so increased stroke volume
What affect would increased venous return have on stroke volume?
Increase venous return causes increase preload causing increased contractility so increased stroke volume
How can the brachiocephalic trunk be distinguished and what 2 important branches does it give off?
It is the first and largest branch off the aortic arch, left and right common carotid
What is a phonocardiogram?
A graphic record in the form of a wave in which you can see the heart sounds obtained with a stethoscope
How would you work out a cardiac cycle from a phonocardiogram?
Start of the first peak to the start of the third
What is the valve position and volume and pressure changes during S1?
Atrioventricular valves close as pressure in the ventricles becomes higher than that of the atria
What is the valve position and volume and pressure changes during S2?
Semilunar valves close as the pressure in the aorta and pulmonary artery become higher than that of the ventricles
What is the valve position and volume and pressure changes during S3?
Atrial pressure slowly increases, all valves closed
What is the valve position and volume and pressure changes during S4?
atrial pressure higher than ventricular pressure so atria contract and AV valves open
What events occur during atrial systole?
atria are contracting, Av valves are open and ventricles fill
What events occur during atrial diastole?
atria are relaxed, AV valves are closed and atria are being filled
What events occur during ventricular systole?
Ventricles are contracting, semilunar valves are open and AV valves are closed
What events occur during ventricular diastole?
Ventricles are relaxed, semilunar valves are closed and AV valves are open as ventricles are filling
What is the ventricular pressure-volume loop?
A plot of a systems volume versus pressure
What is a ventricular pressure-volume loop used to work out?
Work done
What types of receptors are present in the cardiovascular system?
- Alpha 1
- Beta 1
- Beta 2
- M2
In general what are the ways in which vasomotor tone is regulated? (7)
- ANS
- Hormonal factors like adrenaline
- endothelial factors like NO
- Mechanical factors like increased arterial pressure
- metabolic factors
- RAAS
- Calcium and calcium channel concentration
What is a functional syncytium?
a collocational of interconnected cells that form a big cell with multiple nuclei
What is the significance of the syncytium of smooth muscle?
contraction in one area will cause contraction in the whole syncytium
How can severe hypotension cause a triad of clinical consequences in cats? (8)
- hypotension means there is less circulating blood
- blood pressure decreases
- atrial baroreceptors stimulate sympathetic and parasympathetic tone which blocks the usually tachycardia response
- CO remains low
- Peripheries imparted - hypothermia
- cold stimulates PNS causing bradycardia
- cold can stimulate vasodilation!!!
- This causes hypotension
What is arterial pulse pressure?
The abrupt expansion of an artery due to sudden ejection of blood
What molecule is released from hypoxic muscles that can cause vasodilation?
Adenosine
What is angiogenesis?
The formation of new blood vessels
What are the only 2 situations in which angiogenesis occurs?
- trauma/wound healing
- females reproductive system
Give an example of 2 proangiogenic factors
hypoxia and angiopoietins
Give an example of 2 antiangiofenic factors
endostatin, thrombospondin
