CVS Flashcards
Life span of erythrocytes
120 days
Diameter of erythrocytes
7.5 micrometers
Where are RBCs removed
Spleen
Liver
Bone marrow
2 main groups of leukocytes
Granulocytes and agranulocytes
Which type of leukocyte is involved in a) innate immune response and b) adaptive
A) granulocytes
B) lymphocytes
What are the 3 granulocytes
Neutrophil
Basophils
Eosinophils
What are 2 main groups of lymphocytes
B and T cells
What is the most abundant WBC
Neutrophil
What do monocytes mature into
Macrophages or dendritic cells
What do basophils mature into
Mast cells
What are the 2 agranulocytes
Lymphocytes
Monocytes
What is the function of neutrophils
They’re phagocytes so engulf and destroy bacteria and other foreign molecules
They circulate in the blood and invade tissue spaces
What is the function of eosinophils
Phagocytic with particular affinity for antigen/antibody complexes
Have Receptors for immunoglobulin E
Inhibit mast cell creation
Neutralise histamine
Restricts inflammatory responses
What is the function of basophils
Act to prevent coagulation and agglutination
Release histamine and other vaso-active agents in response to allergens which results in immediate hypersensitivity reaction
What is haemostasis
Process to prevent and stop bleeding
Primary - platelet plug formation
Secondary - coagulation cascade
How does vessel injury stimulate the platelet plug formation
Endothelial wall becomes exposed
Smooth muscle contracts to limit blood loss
Mechanisms of contraction:
Endothelin release
Nervous stimulation
Describe the adhesion stage of platelet plug formation
Subendothelial collagen becomes exposed
Platelets bind to collagen via von Willebrand factor using the platelet receptor GP1B
Describe the activation process of platelet plug formation
Once bound to the subendothelium, platelets change shape - from smooth discoid to spiked
Platelets release alpha and electron dense granules, to escalate haemostasis process
Alpha:
vWF, Thromboxane A2, fibrinogen and fibrin-stabilizing factor
Electron-dense:
ADP, Ca2+, Serotonin
Describe the aggregation stage of platelet plug formation
Other platelets are attracted which bind together using GP2b/3a receptors and fibrinogen
How does the coagulation pathway form a cross linked fibrin clot
Prothrombin is converted to thrombin (IIa)
Thrombin converts fibrinogen to fibrin (Ia)
Fibrin stabilising factor (XIIIa) is formed which together with fibrin forms a cross linked fibrin clot
What mediates fibrin breakdown
Plasmin
How does plasmin naturally exist
Inactivated form - plasminogen
What is the membrane potential on a cardiac myocyte at rest
-90mv
How does the length of an action potential differ in the heart vs skeletal muscle
100x longer in the heart
Describe depolarisation in cardiac myocytes
An Action potential arrives
If the threshold potential (-60mV) is reached, Na+ channels open and there’s an influx of Na
Describe the partial repolarisation of a cardiac myocyte
At around +30mv, Na+ channels close and transient K+ channels open.
K+ moves out
Describe the plateau stage of an action potential in a cardiac myocyte
L type Ca2+ channels allow an influx of Ca2+ to balance the K+ efflux
Describe repolarisation in cardiac myocytes
Ca2+ channels close and K+ channels remain open allowing repolarisation
Primary pacemaker
Sinoatrial node
The effect of sympathetic stimulation on pacemaker potential
Noradrenaline increases Ca2+ channel opening so depolarisation is faster
This increases HR and force of contraction
Effect of parasympathetic stimulation on pacemaker potential
Decreases HR
ACh activates K+ channels so the membrane is hyperpolarised
Also decreases calcium influx
Describe the movement of different structure in cardiac looping
The bulbus cordis moves inferiorly, anteriorly and to the embryo’s right
The primitive ventricle moves to the embryo’s left side
The primitive atrium and the sinus venosus move superiorly and posteriorly - resulting in the sinus venosus being posterior to the primitive atrium
Describe fetal circulation
Oxygenated blood from placenta enters fetus through umbilical vein
This blood bypasses liver via ductus venosus into the VC
Blood then travels into the RA and since pressure is higher in the LA most blood is shunted through the foramen ovale
Blood travels from the pulmonary trunk to the aorta via the ductus arteriosus
Deoxygenated blood returns to the placenta via umbilical arteries
What does the right coronary artery supply
Right atrium and ventricle
What does the right marginal artery supply
Right ventricle and apex of heart
What does the posterior interventricular artery supply
Posterior 1/3 of interventricular septum
Right and left ventricles
AV node
What does the left anterior descending artery supply
Right and left ventricle
Anterior 2/3 of interventricular septum
What does the left marginal artery supply
Left ventricle
What does the circumflex artery supply
Left atrium and ventricle
What percentage of people have their PIV artery branch off the RCA only
70%
What percentage of people have their PIV artery branch off the L circumflex A only
10%
What percentage of people have their PIV artery branch off the RCA and LCA
20%
What percentage of people have their PIV artery branch off the RCA
90%
What percentage of people have their PIV artery branch off the LCA
30%
3 hormonal factors that result in vasoconstriction
Epinephrine (skin)
Angiotensin II
Vasopressin
2 hormonal factors that result in vasodilation
Epinephrine (muscle)
Atrial natriuretic peptide
How do central chemoreceptors respond to a decrease in PaCO2
Decrease in medullary tonic activity so decrease in bp
Where is the moderator band found
Right ventricle
What is the fossa ovalis
Depression left when the foramen ovale closes
Give 3 features of cardiac muscle
Striated
Branches
Central nucleus
