Paper 1 - Mass Transport In Animals Flashcards
Explain why it’s an advantage for the human heart to have two separate pumps rather than one
In order to maintain blood pressure around the whole body
Why are the walls of the left ventricle thicker than the right?
Needs to contract with more force to generate higher pressure to send blood around the body
What is the function of the atrioventricular and semilunar valves?
Prevent backflow of blood - AV valves prevent backflow from V to A, SL vales prevent backflow from arteries to ventricles
Atrial systole
- Decreased volume of atrial chambers
- AV valves open, SL valves closed
- Blood is pushed into ventricles
- Increase in ventricular pressure
Ventricular systole
- Decreased volume in ventricles
→ blood is forced up and out into arteries
→AV valves shut = pressure higher in ventricles than in atria
→ SL valves open = pressure higher in ventricles than in aorta and pulmonary artery
Cardiac diastole
- SL valves close - higher pressure in pulmonary artery and aorta than ventricles
- AV valves open - blood flows passively into ventricles from atria
Cardiac diastole
- SL valves close - higher pressure in pulmonary artery and aorta than ventricles
- AV valves open - blood flows passively into ventricles from atria
Control of heartbeat
- Heart tissue is myogenic = contract and relax without nervous input
- SAN generates electric impulse - pacemaker - sends out waves of electrical signals to atrial walls - contract
- Transmitted to AVN
- Electrical signal transmitted down bundle of His
- Slight delay - allows time for atria to empty
- Signal transmitted by bundle of His - Purkinje fibres in muscular ventricle walls - contract from bottom up
What is cardiac output?
The volume of blood pumped by the heart per minute
Risk factors for heart disease
- High blood cholesterol
- Cigarette smoking
- High blood pressure
Describe and explain the effect of high blood pressure on the risk of developing CHD
High Bp increases risk of damage to artery walls = risk of atheroma = further increase in BP.
Atheromas = blood clots forming = blood flow blocked.
Arteries
- Thick muscle layer
- Thick elastic layer → stretches and recoils - maintains high pressure
- Large thickness of wall
- Small lumen
- Inner endothelium folded
Arterioles
- Thicker muscle layer than arteries
- Thinner elastic layer than arteries - lower pressure
Veins
- Thin muscle layer
- Thin elastic layer
- Valves
Capillaries
- Walls only one cell thick - short diffusion distance
- Highly branched - large SA for diffusion
- Narrow diameter - short diffusion pathway
- Narrow lumen - bring RBC close to the cells - short diffusion distance
- RBCs fit in single file - more time for diffusion
- Pores in endothelium - allow water, nutrients and WBC to escape
