Cardiorespiratory Flashcards
what initiates haemostasis?
Occurs when a tissue or blood vessel is directly damaged and causes bleeding.
Facts about platelets?
They are circulating, contain actin and myosin so can change shape, have mitochondria, dense and alpha granules (have lots of proteins), no nucleus, produce ATP and ADP, can manufacture enzymes and has glycoprotein surface receptors.
what is VWF?
Von Willebrand factor is a large glycoprotein (alpha granule) produced by vascular endothelium at the injury site. It circulates in plasma and binds to exposed collagen which causes platelet activation.
how is fibrin formed?
in response to a damaged vessel, a cascade of enzymes causes the generation of the enzyme thrombin which converts soluble fibrinogen to insoluble fibrin.
what is calcium used for during haemostasis?
to prevent blood coagulating in storage
what are the several functions of thrombin?
1) removal of small fibrinopeptides from fibrinogen to form fibrin.
2) activation of XIII
3) activation of platelets
4) catalyses activation of factors ….
what are the limitations of coagulation?
[Thrombin] must be carefully controlled. Intact endothelium secrets a vasodilator which prevents platelet activation.
what is cardiac integration?
The nature of interactions between the heart, vasculature and other biological systems to optimise function.
what things can modify smooth muscle contraction (aka raise intracellular Ca+ levels)?
Chemical -> metabolism, hormones, paracrine effects.
Physical-> blood pressure and flow.
Classic Principles of flow regulation?
- Re-active hyperaemia
- Active hyperaemia
- Myogenic tone
- Flow-dependant vasodilation (NO)
How does Nitric Oxide effect blood flow?
It is a vasodilator. Nitric oxide increases blood flow and lowers blood pressure.
define vasodilation?
Increase in internal diameter of a blood vessel due to relaxation within the wall of the vessel. This causes an INCREASE in blood flow but a DECREASE in resistance and pressure.
define vasodilatation?
Increased calibre of the blood vessel.
what is transmural pressure?
The pressure exerted across the vessel wall.
what are the four main factors which effect blood flow?
Diameter, Length, Pressure and Viscosity.
what are structural adaptations of the coronary circulation?
High capillary density. Large endothelial area. Reduced diffusion distance.
what are the functional adaptations of the coronary circulation?
High flow and O2 extraction.
what is metabolic hyperaemia?
Condition where the muscle is working hard and release metabolites, uses ATP and breaks it down to the vasodilator (adenosine).
what are the structural adaptations of cerebral circulation?
high capillary density. Grey matter has large exchange area. Blood brain barrier (lipophilic things can’t get out of brain).
what are functional adaptations of cerebral flow?
High basal blood flow (grey matter).
Self preservation.
Cerebral auto regulation.
what are risk factors for stroke?
Modifiable -> Diabetes, hypertension, cigarette smoking, atrial fibrillation.
Unmodifiable -> sex, gender, age, ethnicity, genetics.
what is destroyed during. stroke?
120 million neurons, 830 billion synapses, 447 miles of myelinated.fibres.
what does the rate of transfer in diffusion depend on?
area, distance and driving force (conc. gradient).
what conditions arise at high altitude?
reduced barometric pressure, reduced partial pressure of oxygen, decrease in air temp and water vapour pressure. High exposure to UV.
