What percentage of blood is plasma?
What is plasma composed of?
Water, electrolytes, plasma proteins
Name 3 plasma proteins.
Albumin - important in maintaining blood pressure
Fibrinogen - inactive form of fibrin, blood clotting
globulins - fat transport and immune function
why are red blood cells biconcave shape?
Allows cells to fold over in narrow capillaries, allows the cells to expand and accommodate fluid in hypotonic solution
where are red blood cells produced?
Red bone marrow, in skull, sternum and hip bones
describe red blood cell production.
Low oxygen delivery to kidneys is detected, erythropoietin is released, stimulates the red bone marrow, uses amino acids to produce proteins and iron in the haemoglobin. These cells are then matured, shrink in size and lose nucleus
What vitamins are required for red blood cell production
vitamin b12 and vitamin k
Describe how the mixing of blood can be dangerous at birth between a rheus’ negative mother and rheus’ positive baby.
if mother gets rheus’ positive blood, exposed to antibody so the mother produces an antigen against this. If the mother then goes on to have another rheus’ positve child, the antigens in the mothers blood will be passed to the baby. These will attack the blood in the baby resulting in haemolysis
What is the role of the chordinae tendinae and pupillary muscles in the heart?
These hold the flaps and orientate their shape. They have no role in the opening and closing of the flaps, completely done by pressure changes
What are the noises of the heart and how are these sounds produced?
The LUB noises is produced from the AV valve closing. This closes as the ventricle contracts, increasing the pressure. The DUB noise is produced from the SL valves closing, this is as the pressure in the ventricle is reduced due to the blood leaving, closes to prevent back flow
Describe starling’s law
If more blood is returned to the heart, the end diastolic volume is increased. This is detected by stretch receptors on the heart. The contraction is then increased to increase the volume of blood pushed out of the heart.
Describe the SA node action potential.
There is a gradual rise to the threshold level, as there is a constant leakage of calcium into the cell. Once it reaches threshold, there is a much more rapid increase of calcium. As it reaches +30mV, calcium channels are closed and potassium channels are opened, the cell is repolarised
Desribe purkinje cell action potential
voltage gated Na channels are opened, causing depolarisation. At +30mV, calcium channels are opened. As calcium enters the cell, there is a plateau phase in the AP, preventing repolarisation. After this, potassium channels are opened, allowing for repolarisation
How does the autonomic system act to lower the heart rate?
The parasympathetic system releases acetylcholine, this increases potassium permeability at the SA node. Takes longer to reach theshold
How does the autonomic system act to increase the heart rate?
Sympathetic nervous system releases noradrenaline which increase Ca permeability at the SA node. Reaches threshold faster.
What is calcium induced calcium release?
Calcium moves into the cell, this binds to the sacroplasmic reticulum which amplifies this response and releases more calcium
Describe what happens at each point on the ECG wave.
P - atrial depolarisation, QRS - ventricular depolarisation, T - ventricular repolarisation. P-R interval - time taken for impulse to go through AV node. S-T interval - plateau phase in AP, calcium entry
What is the role of the endothelial cells in blood vessels?
permeable for nutrients and gases, can control underlying muscles for vasoconstriction
What do smooth muscle cells do in blood vessels?
Control the diameter of the lumen of the vessel
How does the structure of the arteries give the function?
A lot of elasticity giving the vessels compliance to maintain the pressure
What is the pulse pressure?
Systolic pressure - diastolic pressure
how can the mean arterial pressure be calculated?
diastolic + 1/3rd pulse
map = cardiac output x total peripheral resistance
how can the tpr be reduced by drug therapy?
blocking alpha 1 adrenoreceptors on the smooth muscle in blood vessels, prevents vasoconstriction increases dilation - prazosin
Describe the pressures influencing the movement of fluid through the capillaries.
As blood enters capillaries, hydrostatic pressure is high pushing fluid out of capillaries. As fluid is pushed out, the hydrostatic pressure is reduced along the capillaries. The oncotic pressure (from plasma proteins) remains the same along the capillary. At the venous end, the oncotic pressure exceeds the hydrostatic pressure, pulling fluid back into the capillary.
Name the factors that influence blood flow.
Pressure gradient, viscosity, length of tube and radius of tube
what is the relationship between the radius of the vessel and the flow rate?
As the radius increases, the flow increases. In the equation, radius is to the power of 4 so a small change in radius results in a large change in flow
How can viscosity alter the blood flow and why is this important on flights?
A fluid with a high viscosity has a lower flow rate. In flights, people often drink alcohol, making them dehydrated and increasing the viscosity of the fluid. This is accompanied with inactivity, making the venous return poor and can increase oedema in the legs.
How can the blood flow in veins be altered?
Decreasing the diameter of the vessel, increases the pressure, thus improves flow. Can be done using sympathetic nervous system for vasoconstriction, in exercise improves venous return to increase CO
Why is the venous blood flow important in angina patients and how can this be altered to relieve symptoms?
an increased venous return increases the pre-load on the heart, giving it more work to do thus it requires more oxygen and symptoms are more intense. Giving alpha 1 antagonists, blocks sympathetic vasoconstriction on veins meaning the vessel diameter will be wide, the pressure will be low and venous blood flow will be reduced. Nitrates are used for this
what nerves do the baroreceptors in the carotid sinus and aortic arch activate?
carotid sinus - glossopharyngeal
aortic arch - vagal
describe the sequence of events that occur in response to a high blood pressure.
baroreceptors send nerve signal to nucleus tractus solitarius in medulla oblongata. parasympathetic NS stimulated, activates alpha 2 receptors. This activates then vagal nucleus. this sends acetylcholine to the muscarinic receptors on the heart, slow heart rate down, Alpha 2 receptors also inhibit the sympathetic ns and bulbar circulatory centre - reduce HR and vasoconstriction
Describe the sequence of events that occur in response to low blood pressure.
baroreceptors send signal to the nucleus tractus solitarius in medulla oblongata, activates beta receptors to stimulate the bulbar circulatory centre. This uses noradrenaline to increase the heart rate on beta 1 receptors and increase vasoconstriction on alpha 1 receptors. Also inhibits the vagal nucleus to remove the reduce on heart rate
how can blood pressure be controlled locally?
Metabolites are released which cause local vasodilation to increase the blood flow
Describe how blood pressure can be measured.
Use a cuff around the arm - increases pressure to reduce blood flow through radial artery. Use sphyg. to listen for flow, once flow stopped, start reducing pressure slowly. Pressure at which flow is first heard - systolic pressure. Keep reducing pressure slowly, when no flow is heard again - diastolic pressure
what occurs as a patient is moved from lying down to standing up?
Blood is pulled by gravity to the lower limb, it can then pull in the veins reducing venous return. Then, less blood is pumped out by heart, less blood to brain, baroreceptors detect decrease in blood pressure - reduced firing to brain
In an ECG, what does the T-Q interval represent?
What is the haematocrit?
The percentage red blood cells in a volume of blood
Describe 2 ways in which haemolysis can occur?
Cells in a hypotonic solution, water moves into cells from surrounding solution, causing cell to burst
Detergents can breakdown lipids in cell membrane, causing the cell to burst
What is the difference between an isotonic solution and an iso-osmotic solution?
isotonic - equal osmolarity and impermeant solutes
iso-osmotic - equal osmolarity but solutes are permeant
Why is stored blood more fragile than fresh blood?
stored blood has less ATP so cannot prevent haemolysis as efficiently, haemolysis occurs at lower % of saline