Intro to the CVS Flashcards
Why is a cardiovascular system needed? [6 marks]
- Carry gases
- Transport nutrients
- Circulate hormones and immune mediators
- Connects to the lymphatic system
- Human reproduction
- Regulates temperature
What is the time needed to diffuse a given distance proportional to? [1 mark]
The square of the distance
What is Hg? [1 mark]
Pressure that it takes to support a column of mercury at millimetres.
How is blood pressure measured? [1 mark]
Systolic/Diastolic
What is systole? [1 mark]
Contraction
What is diastole? [1 mark]
Relaxation
What is cardiac output? [1 mark]
- The volume of blood ejected from the heart per minute.
- Typically around 5 litres/min.
What tissues are under perfused? [2 marks]
- Myocardium
- Brain
What clinical problems can arise from under perfusion? [3 marks]
- Angina
- Stroke
- MI
What is the formula for cardiac output? [3 marks]
Cardiac output (CO) = heart rate (HR) x stroke volume (SV)
What controls cardiac output? [3 marks]
- Starling’s Law
- Autonomic control of the heart
- Chemical factors like adrenaline
What is blood flow proportional to? [1 mark]
Pressure difference across blood vessels
What is blood flow inversely proportional to? [1 mark]
Resistance of blood vessels
What is the formula for blood flow? [3 marks]
Blood flow= ((P artery-P vein))/Resistance
How does resistance affect blood flow? [1 marks]
Higher resistance = lower blood flow
and vice versa
What is the blood pressure at systemic circulation and why is it that? [2 marks]
- 120/80
- To exert enough force to pump blood around.
What is the blood pressure at pulmonary circulation and why is that? [2 marks]
- 25/15
- To allow gaseous exchange to occur.
What are the resistance vessels and what do they do? [3 marks]
- Arterioles
- Determine total peripheral resistance by controlling arterial blood pressure
- Decrease in diameter = decrease in downstream pressure
How does the cross-sectional area affect velocity? [1 mark]
Decrease in CSA = increase in velocity
and vice versa
What is the formula for blood velocity? [3 marks]
Blood velocity (cm/s) = (Blood flow)/number × (πr^2 per vessel))
What occurs in dual parallel circulation and what organs are supplied this way? [3 marks]
- Cardiac output is split
- This safeguards O2 supply in organs
- Most organs are supplied this way
What occurs in dual series (portal) circulation and what organs are supplied this way? [3 marks]
- Blood flow from one organ to another
- Lower perfusion pressures
- Organs in the digestive system are supplied this way
What is in the tunica intima? [2 marks]
- One layer of endothelial cells
- Supported by an internal elastic lamina
What is in the tunica media of arterioles, arteries and the aorta? [3 marks]
ARTERIOLES: smooth muscle in circular lamellae
ARTERIES: elastic fibres and collagen form lamellae
AORTA: lots of elastic fibres
What is the difference between the tunica media in venous vessels and arterial vessels? [1 mark]
There’s less elastic fibres in venous vessels (as they don’t need to transport blood in high pressure)
What is in the tunica adventitia in arterial and venous vessels? [2 marks]
ARTERIAL: collagen supported by an external lamina
VENOUS: collagen
What does the endothelium do? [2 marks]
- Produces nitric oxide
- Relaxes the vessels
What do sympathetic nerves do in the tunica adventitia? [3 marks]
- Releases noradrenaline
- Stimulates α1 adrenergic receptors
- Leads to vasoconstriction
What are capacitance vessels and what do they do? [3 marks]
- Veins/venules
- Control filling pressure
- Provide reservoir for 2/3 of blood
What are elastic vessels and what do they do? [3 marks]
- Arteries
- They accommodate stroke volume.
- Convert intermittent ejection into continuous flow.
What are exchange vessels and what do they do? [3 marks]
- Capillaries
- Deliver nutrients to tissue
- Form lymph to remove metabolic waste
