Cardiovascular Flashcards
What are the approximate dimensions of one ventricular cell
100um x 15um
What is a T-tubule?
A finger-like invagination of a cell
Is calcium higher naturally intracellularly or extracellularly?
Extracellularly
How is calcium removed from the cell?
- Calcium induced calcium release from the SR.
2. Exported by Na+/Ca2+ pump
Does the Na+/Ca2+ exchanger require energy?
No; uses Na+ gradient to drive sodium in and calcium out of the cell.
Which is more compliant to stretching - cardiac or skeletal muscle?
Skeletal muscle. Cardiac muscle is more resistant to stretching (less compliant); extracellular properties of the cytoskeleton.
What is isometric contraction?
No shortening of the muscle fibre but pressure increases in ventricles.
What is isotonic contraction?
Shortening of the muscle fibre and blood is ejected from the ventricles.
Which type of contraction is associated with increased filling and increased pressure within the ventricles?
Isometric contraction.
Are semi-lunar valves open or closed during isometric contraction?
Closed; ventricles are filling.
Define Preload
The initial stretch of the myofibre during diastolic filling.
Define Afterload
The pressure that the left ventricle must overcome to eject blood through the aorta to the systemic circulation.
What does increased afterload result in?
A decrease in isotonic shortening and volume of blood ejected from the heart.
Name one measure of afterload and one of preload.
Afterload = DBP Preload = RAP, EDV, EDP
Preload relates mostly to….
Ventricular filling
Afterload relates mostly to….
Pressure within the aorta
Describe Frank-Starling’s law
Increased diastolic fibre length increases ventricular contraction. (know word for word!)
What are the two explanations for greater contraction at a greater myofibre length?
- Greater myofibre length = more actin-myosin interactions.
- Greater myofibre length = increased affinity of troponin for calcium.
What is stroke work?
Work performed by the heart to eject blood under pressure into the pulmonary artery and aorta.
Define LaPlace’s law
When the pressure within a cylinder is kept constant, the tension on its walls increases when its radius does.
Where does the heart spend more time in?Systole or diastole?
Diastole by 2/3. Diastole has 4 phases whereas systole has 3.
How many cardiac cycle phases are there?What are they?
- Atrial systole
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid passive filling
- Reduced passive filling
What is a formula for ejection fraction?
SV/EDV
Define tetanus
Prolonged contraction of a muscle due to a rapidly repeated stimuli.
Which segment of the pressure volume loop is the longest in duration?
D to A; Filling
What is a formula for Stroke volume?
EDV-ESV
When is the 4th heart sound heard?
Congestive heart failure or pulmonary embolism. 4th heart sound = abnormal.
What does the 1st heart sound ‘lub’ indicate?
Closure of the atrioventricular valves
During which phase of the cardiac cycle is the first heart sound seen?
Isovolumetric contraction
What does the 2nd heart sound ‘dub’ indicate?
Isovolumetric relaxation; closure of semi-lunar valves.
What does the dichrotic notch indicate?
Closure of the aortic valve.
What does the 3rd heart sound indicate?
Turbulent flow and may be abnormal. Can signify mitral incompetence
When may be the 3rd heart sound be seen?
During rapid passive filling.
The right ventricle pumps the same volume of blood to the pulmonary circulation as the left ventricles does to the systemic circulation. True or false.
True. Same volume just at lower pressures.
Which has a larger volume - ESV or EDV?
EDV.
An increase in afterload has what affect on stroke volume?
Afterload decreases stroke volume.
Stroke volume is affected by which 3 things?
Preload
Afterload
Contractility
Which is the capacitance vessel?
The vein
What is Darcy’s law?
Pressure Gradient = Blood flow x Resistance.
Which vessels have the most resistance?
Small arteries and small arterioles.
What is the biggest determinant of blood flow?
Resistance.
What is the shear rate?
The gradient of velocity at any point
What is shear stress?
Shear rate x viscosity. Shear stress is a good indicator of endothelial function. High shear stress indicates good endothelial survival.
Where is low shear stress seen?
Platelet aggregation, coagulation and vasoconstriction.
How do you calculate pulse pressure?
Systolic blood pressure - diastolic blood pressure.
How do you calculate mean arterial blood pressure?
(2/3 x DBP) + (1/3 x SBP).
Which are the more compliant blood vessel - arteries or veins?
Veins.
Varicose veins are often caused by what?
Incompetent valves causing dilatation of superficial veins.
What is central venous pressure?
The pressure in the vena cavae and indicates the mean pressure within the right atrium.
What is ANP?
Atrial Natriuretic peptide secreted from the atria in response to stretch which has vasodilatory effects.
Where does the parasympathetic system arise from in comparison with the sympathetic system?
Parasympathetic system arises from the cranial and sacral spinal cord.
Sympathetic system arises from the thoracic and lumbar spinal cord.
Which is the pre-synaptic neurotransmitter for the sympathetic and parasympathetic system? What is the post- synaptic neurotransmitter?
Pre-synapse = ACh for both symp. and parasymp. Post-synapse = NA for symp, ACh for parasymp.
What does increased tonic activity cause?
Vasoconstriction.
Noradrenaline binds to which receptors in the heart?
B1 receptors
What stage of events occurs when Noradrenaline binds to the b1 receptor?
Calcium influx into the myocardial cell increases
Calcium uptake into the ST increases; increases Ca2+ induced Ca2+ release from SR.
Does a low or high intrathoracic pressure increase the EDV?
A decrease in intrathoracic pressure.
When is the baroreceptor reflex most sensitive? How would this show on a graph
When arterial pressures are between 90-100mmHg.
Graph shows a gradual upward curve until 90-100mmHg when it becomes very steep.
How does the basoreceptor reflex decrease blood pressure?
Stimulates parasympathetic activity to the heart and inhibits sympathetic activity to the heart, arteries, veins and venules and tonic activity.
Which are the Parasympathetic nervous system’s afferent and efferent nerves?
Afferent: Vagus nerve and Glossopharyngeal nerve.
Efferent: Vagus nerve.
How do baroreceptors detect a increase/decrease in blood pressure?
Through the stretch of the aortic arch/carotid arteries.
How is venous returned controlled?
Through venous return which is determined by 1. Skeletal muscle pump and 2. Sympathetic activation of veins.
When blood pressure decreases e.g. during haemorrhage, what mechanisms take place by baroreceptor reflex?
- Increased vaso+venoconstriction
- Increased sympathetic stimulation(discharge) to veins
- Increased venous pressure
What is the myogenic theory?
When there is an increase in blood pressure, smooth muscles fibres in the vessel contract.
What is the metabolic theory?
When blood flow decreases, metabolites accumulate and cause vasodilatation.
Where is the vasomotor centre?
The Medulla Oblongata
What is the purpose of capillaries?
To deliver metabolic substances to the cell
Why is capillary density important?
Capillary density maximises the surface area and minimises diffusion distance = enhances diffusion.
Where are fenestrated capillaries found?
Kidney
Where are discontinuous capillaries found?
Bone marrow, liver
What are the x3 types of capillary structure?
Continuous, discontinuous and fenestrated.
Give an example of where a continuous capillary is found.
The blood brain barrier.
Describe Oncotic pressure.
Oncotic pressure is a ‘pulling force’; it pulls proteins from the interstitial fluid back into the vessel.
Describe Hydrostatic pressure.
A pushing force i.e. from blood vessel out to interstitial fluid.
Apart from direction of flow what is a difference between hydrostatic and oncotic pressures?
Hydrostatic pressure is greater at the beginning of the capillary whereas oncotic pressure stays the same throughout the capillary.
Which is more effective - ultrafiltration or reabsorption?
Ultrafiltration; hydrostatic forces. Reabsorption is controlled by oncotic forces.
What is another name for oncotic pressures?
Colloid osmotic pressure.
Capillary density is proportional to metabolic activity. True or false?
True.
What are the three components of the ECG?
Electrodes, cables/ wires and leads
What is a vector?
A quantity that has both magnitude and direction.
What does the isoelectric line represent?
No net change in voltage
Are upward cardiac vectors towards the anode or cathode?
Towards the cathode(+)
Which part of the cardiac anatomy has the slowest conduction velocity?
The bundle of his; 2-5 m/s
Which are the bipolar leads in the ECG?
Leads I, II and III.
What is the normal R-R interval?
0.6s-1.2s
What is the normal voltage and paper speed?
25mm/s, 10mm/mV
Which is the shockable rhythm?
Ventricular tachycardia and ventricular fibrillation
What is Ventricular fibrillation?
An irregular rhythm where the heart is unable to generate an output.
What is Ventricular fibrillation?
An irregular rhythm at a rate of above 250bpm, where the heart is unable to generate an output.
What is ST depression caused by?
Myocardial ischaemia
Would you defibrillate on asystole?
No; it is not a shockable rhythm.
Which is the most isoelectric lead?
aVL.
Name 2 effects of thromboxane.
Causes platelet aggregation and vasoconstriction.
Name 4 effects of Angiotensin II.
Arteriolar vasoconstriction, sympathoexcitation, ADH secretion, Aldosterone secretion and Tubular sodium reabsorption.
What are the approximate values of intracellular vs extracellular calcium?
Intracellular = 100nmol/L Extracellular = 2mmol/L (REMEMBER THE nm Vs mm). Intracellular = less.
Is calcium higher intracellularly or extracellularly?
Extracellularly
In the Na+/Ca2+ exchanger, what is the direction of each of the ions?
Calcium flows into the cell as it is lower intracellularly. Sodium flows out of the cell; Na+ has been pumped in from Na+/K+ pump.
Is the inhibition of COX enzymes by aspirin reversible or irreversible?
Irreversible.
What treatment should you use if you want reversible inhibition of the COX enzymes?
NSAIDS.
What is the difference between the platelet and the endothelial cell?
The platelet does not have a nucleus.
What are the 3 phases of atherosclerosis?
- Endothelial damage and dysfunction.
- Fatty streak formation (foam cells)
- Well-developed atheromatous lesion (macrophages and necrotic area formed).
Define senescence
Deterioration with age. Cell stops growing, dividing.
Name one physiological mechanism that may predispose an individual to atherosclerosis.
Type of blood flow - turbulent or laminar?
What is angiogenesis?
The formation of new blood vessels from the endothelial lining of existing blood vessels.
Give x3 circumstances where the body require angiogenesis.
- Embryonic growth
- Menstrual cycle
- Wound healing
Are senescent cells good for the body?
Yes; they stop the growth of damaged cells and prevent that damage being passed onto the daughter cell.
No; they are pro-inflammatory and can be found in atherosclerotic lesions.
What is the name of the substance in red wine that is thought to decrease cardiovascular risk? How does it work?
Resveratrol. Resveratrol promotoes endothelial protective pathways e.g. production of eNOS. Also reduces cell senescence.
What is the intrinsic rate of the heart?
100-110bpm.
Are venous pressures higher at the top or the bottom of the body?
At the bottom of the body.
What affect does hydrostatic pressure have on capillary fluid from the supine to standing position?
Increased hydrostatic pressure pushes fluid out of the capillary which leads to CAPILLARY FLUID LOSS.
Name one key effect of capillary fluid loss during standing? (Why is there capillary fluid loss?)
Decreased venous return. (; Increased hydrostatic pressure forces fluid out of the capillary).
In one day, more fluid exits the capillary through filtration than enters through reabsorption. True or false?
True.
The pupil is always mildly….
constricted; vascular tone so vessel can further dilate when needed.
What is the mechanism of action of Pilocarpine? When may it be used?
Causes constriction of the pupil. This is useful when there is high pressure inside the eye e.g. glaucoma, as constriction causes decreased fluid inside the eye.
What is the mechanism of action of Tropicamide?
Causes dilatation of the pupil.
What group of drugs does Pilocarpine belong to?
Cholinergic agonist
What group of drugs does Tropicamide belong to?
Muscarinic antagonists
How is respiratory function regulated?
Pontine respiratory centre = controls rate and pattern of breathing.
Medullary respiratory centre = controls diaphragm and rhythm
Which nerves innervate the diaphragm?
C3, C4, C5.
Which nerves innervate the accessory muscles?
C1, C2, C3.
Which nerves innervate the intercostal muscles?
T1-T11
Which nerves innervate the abdominal muscles?
T6-L1
Activation of the parasympathetic system in the bladder has what effect?
Contraction of the detrusor muscle = inhibition of the internal sphincter = micturition.
Which part of the bladder is under voluntary control?
The external sphincter; made up of skeletal muscle.
NTS sends signals to where?
Nucleus Tractus Solitarius sends signals to the hypothalamus which sends signals to the DMNX (Dorsal motor nucleus of the vagus nerve).
What are the two divisions of the parasympathetic receptors?
Nicotinic and muscarinic.
What are the two divisions of the sympathetic receptors?
alpha (a1, a2) and beta (b1, b2)
Which are the receptors which determine neurotransmitter release?
Pre-synaptic receptors
Which receptor type innervate the sweat glands?
Muscarinic receptors
Which group are nicotinic and muscarinic receptors a part of?
Cholinergic receptors
What is atropine?
Competitive muscarinic receptor antagonist
What is common side effect of atropine?
Dry mout
What is the effect of atropine on the heart?
Atropine will increase the heart rate
What is the effect of atropine on the sweat gland?
Decrease sweat gland production
What is tubocucarine?
A nicotinic receptor antagonist
What is the effect of tubocurarine on the heart rate?
Removes all autonomic control from the heart as there are nicotinic receptors at both the sympathetic and parasympathetic systems.
All adrenergic receptors are….
GPCRs
What is Medetomidine?
An alpha 2 receptor agonist.
What is the effect of alpha 2 receptor agonists on noradrenaline release?
Inhibition of noradrenaline release.
An alpha 1 receptor antagonist will have what effect on smooth muscle?
Smooth muscle dilatation.
To which class of drugs does salbutamol belong?
Beta 2 receptor agonists.
To which class of drugs does atenolol belong?
Beta 1 receptor antagonists.
Which factor is Thrombin?
FIIa.
What does the ‘a’ stand for in e.g. FIIa
Activated coagulation factor.
Which is the main trigger of coagulation?
Tissue factor and Factor VIIa.
Which is the main trigger of forming the primary haemostatic plug?
Platelets binding to vWF and Collagen.
What is the name for FII
Pro-thrombin; no activation.
Factor VIIIa is a protease. True or false.
False.
Thrombin generates which two main coagulation factors?
FVa and FVIIIa.
Where does activated coagulation occur?
On the platelet surface.
