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Flashcards by reynoldslaura, updated more than 1 year ago
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Created by reynoldslaura
over 11 years ago
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| Question | Answer |
| is the internal or external elastic lamina more prominent? | Internal! |
| Why is the elastic lamellae in elastic arteries fenestrated? | To allow nutrients to diffuse in and reach the smooth muscle cells and other cells in the tunica media |
| In what tissues do we find fenestrated capillaries? | In tissues where there is molecular exchange with the blood e.g. villi of the small intestine and the kidneys |
| In what tissues are continuous capillaries found? | They are the main type of capillaries found in most body tissues e.g. lung, muscle, CNS |
| In what tissues do we find discontinuous capillaries? | In the liver and spleen. They have large open pores that allow big molecules to get through- potentially even cells |
| Where are veins with valves found? | In the lower limbs (absent from thorax, brain and abdomen) |
| Give an example of a vein that has several layers of smooth muscle in its tunica media. | Vena cava or renal veins |
| What type of blood vessels have muscular arteries? | All major blood vessels except ones serving or near the heart |
| Give an example of an elastic artery? | The aorta |
| Where does an atheroma start? | In the tunia intima |
| What are 'vasa vasorum' ? | 'vessels of vessels' - These are very small arteries which give rise to a capillary network within the tunica adventitia that supply the tissue in the walls of very large blood vessels e.g. the aorta |
| Approximately what percentage of blood is found in veins and venules? | Around 70% (the walls are thinner and less rigid than arteries so can hold more blood) |
| What percentage of blood is found in the systemic arteries? | Approximately 10% |
| What are the dimensions of a capillary? | 0.8mm x 6micrometers |
| What does the tunica intima consist of? | Endothelium and loose connective tissue |
| What does the tunica media consist of? | Smooth muscle cells, fibroblasts, elastin and collagen |
| What does the tunica adventicia consist of? | Internal and external elastic lamellae |
| Where are volume receptors located? | In the walls of the cardiac atria |
| What is the raphe nucleus? | Its a specialised region in the medulla that has an inhibitory output to pre-ganglionic sympathetic nerve fibres |
| What controls total peripheral resistance? | Arterioles and precapillary sphincters |
| What is the long term regulator of blood pressure? | The kidneys- monitoring via extracellular volume and composition of blood and via hormonal mechanisms e.g. antidiuretic hormone |
| What type of blood pressure regulator is the baroreceptor reflex? | It is a short term regulator. It is concerned with the minute to minute regulation of arterial blood pressure |
| The baroreceptors detect an increase in arterial blood pressure. What happens next? | Their afferents will inc. their discharge to the brainstem where it elicits an inhibition of sympathetic activity to the heart and vessels and an inc. in parasymp. activity to the heart etc. |
| What percentage of circulating blood is found in the capillaries? | 5% |
| What is the function of baroreceptors and where are they found? | Baroreceptors monitor high pressure and feed back to the meduola oblongata. They are found in the elastic walls of the carotid arteries and the arch of the aorta |
| When does metabolic or active hyperemia occur? | When metabolic by-products cause vasodilation and therefore increase blood flow |
| Give three examples of metabolic by-products. | Any three from; K+, lactic acid, CO2, H+ |
| How can the diameter of blood vessels be controlled intrinsically? | Either by metabolic by-products causing vasodilation or by the myogenic response (controlled by heart muscle cells) |
| What is the diameter of arterioles? | 5-100µm |
| What is the diameter of capillaries? | 5-10µm |
| Where are arteriovenous anastomoses found? | In the fingers, palms and ear lobes |
| Name two extrinsic controllers of blood vessels. | Autonomic nervous system and hormones |
| What effect does angiotensin II have on blood vessel diameter? | It causes vasoconstriction |
| What effect does adrenalin have on blood vessel diameter? | It causes vasodilation |
| What effect does vasopressin have on blood vessel diameter? | It causes vasoconstriction |
| What effect does ANP (atrial natriuretic peptide) have on blood vessel diameter? | It causes vasodilation |
| What is total peripheral resistance? | The sum of the resistance of all peripheral vasculature in the systemic circulation |
| Does pulse pressure apply to capillaries? | NO! by the time blood has reached the capillaries it's at very low pressure and it meets walls of capillaries with considerable resistance. There is no difference between systolic and diastolic pressure |
| How do we calculate blood pressure? | Total peripheral resistance x cardiac output |
| How do we calculate mean arterial pressure? | Diastolic + 1/3 of pulse pressure |
| What is the normal value for diastolic pressure? | 80mmHg |
| What is the normal value for systolic pressure? | 120mmHg |
| What is the normal value for pulse pressure? | 40mmHg, although it can be higher if there is atherosclerosis |
| How do you calculate pulse pressure? | It is the difference between systolic and diastolic pressure. It is usually around 40mmHg but it is higher if there is atherosclerosis |
| What's the normal value for mean arterial pressure? | It is usually 90-95 mmHg. Females have lower than average arterial pressures |
| What causes the dicrotic notch? | The left ventricle relaxing causing the aortic valve to snap shut which creates a small surge in aortic pressure before it falls again. The dichrotic notch occurs later and later as we look down the arterial tree |
| Define venous return | The volume of blood returning to the heart from the central veins every minute |
| Define cardiac output | The volume of blood pumped out from one ventricle each minute |
| Name two factors that affect end-diastolic volume. | Intrathoracic pressure and central venous pressure |
| What is the equation for ejection fraction? | Ejection fraction= stroke volume÷end diastolic volume |
| Name three methods which we can use to measure cardiac output or stroke volume and heart rate. | 1. Fick's principle 2. Pulsed ultrasound 3. Dilution methods (rapid injection of dye and following the rate of dilution) |
| Equation for cardiac output | cardiac output = heart rate x stroke volume |
| What is Starling's Law | "the energy of contraction of the ventricle is a function of the initial length of the muscle fibres comprising its walls" |
| How do we calculate stroke volume? | end diastolic volume-end systolic volume |
| What is the typical value for stroke volume? | 70ml |
| What is the typical value for end diastolic volume? | 130ml |
| What is the typical value for end systolic volume? | 60ml |
| How do we calculate perfusion pressure? | Arterial pressure-venous pressure |
| How do we calculate blood flow? | perfusion pressure ÷ vascular resistance |
| What is the flow of blood driven by? | The difference in pressure between arteries and veins |
| What does Poiseuille's law describe? | The flow of fluid through tubes. For a given flow rate, blood velocity varies inversely with cross sectional area. (Larger the cross sectional area, the lower the velocity) |
| What is the equation for the law of Laplace? | P=T/r Where P is pressure, T is tension in the blood vessel wall and r is the radius |
| What are the three layers of large blood vessels? | Tunica intima, tunica media and tunica adventicia (All blood vessels have a tunica intima, just consists of endothelial cells) |
| What is the function of an anatomose? | They directly connect arterioles to venules |
| What are they key differences between a cardiac action potential at the ventricle and one at the SAN? | Phase 0- depolarisation is less steep Phase 1- isn't present Phase 2 and 3- have a brief plateau and repolarisation is less steep Phase 4 -is the PACEMAKER potential and it is an unstable resting potential |
| Where do you place limb lead II? | Positive electrode on the left leg and the negative electrode on the right arm |
| How long does one cardiac cycle last for? | 0.8 seconds |
| How long does diastole last for? | 0.4 seconds |
| Where does the sympathetic nerve supply to the heart come from? | The epicardial plexus |
| Where does the parasympathetic nerve supply to the heart come from ? | Vagus nerve CN X |
| What neurotransmitter is released via the parasympathetic neurons and what receptor do they act on? | Neurotransmitter released is acetylcholine and it acts on M2 muscarininc receptors to slow down heart rate at the SAN and AVN |
| What neurotransmitter is released by the sympathetic neurons and what receptors does it act on in the heart? | The neurotransmitter released is Noradrenaline which acts on the B1 and also on the B2 and a1 receptors to increase heart rate at the SAN and AVN and the force of contraction in the ventricles |
| Name three differences between cardiac and skeletal muscle | 1. Cardiac muscle cells are much smaller 2. Cardiac muscle cells are connected via desmosomes and gap junctions 3. Cardiac muscle cells have long contractions e.g. 200ms |
| What is the conduction velocity of the AVN? | 0.05ms |
| What is the conduction velocity of the sino-atrial node? | 1ms |
| What is the conduction velocity of the purkinje fibres? | 5ms |
| What is the conduction velocity of the bundle of his? | 1ms |
| What is the physiological significance of the 0.1s delay at the AVN? | It allows the atria to have ejected all their blood into the ventricles before the contract. This protects the ventricles from an excessively fast rate response to atrial arrhythmias |
| Where do you place limb lead III? | The positive electrode on the left leg and the negative electrode on the left arm |
| What does limb lead one record? | It records the excitation moving between the left and right hand sides of the heart |
| What are the potential changes in the heart and how do they differ to surface potential recordings? | In the heart,potential changes are 120mv, almost 100 times greater than the surface potential recordings (1-2mv) |
| How long does the P wave last for? | 0.08 seconds |
| What does the P wave correspond to? | Atrial depolarisation prior to contraction |
| What does the QRS complex correspond to? | Ventricular depolarisation |
| What does the T wave correspond to? | Ventricular repolarisation |
| When does atrial repolarisation occur? | During ventricular depolarisation however it is masked by the QRS complex |
| How long does the QRS complex last for? | 100ms, it is very large |
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