Transport in animals

Open system

blood bathes tissues directly while held in cavity haemocoel, no respiratory pigment required

Closed system

blood moves in blood vessels, requires a respiratory pigment

Single circulation

blood moves through heart once, blood pressure slower, 2 chambers in heart, blood flow slower

Double circulation

blood passes through the heart twice, blood pressure higher, 4 chamber in heart, blood flow faster

Route that deoxygenated blood takes through the heart

s/v vena cava → R atrium → tricuspid → R ventricle → SL valve → pulmonary artery

Route that oxygenated blood takes through the heart

Pulmonary vein → L atrium → bicuspid → L ventricle → SL valve → aorta

the 3 stages of the cardiac cycle

Atrial systole, ventricular systole, ventricular diastole

atrial systole

atrium walls contract, BP increases, pushes blood through tricuspid + bicuspid valves into the relaxed ventricles

ventricular systole

ventricle walls contract, BP increases, forces blood through SL valves to PA + A, B and T close due to rise in VP

ventricular diastole

ventricles relax, V increases so P decreases, risks backflow into ventricles, SL shut to stop this

Arteries

carry blood away from heart, thick and muscly walls withstand high BP, branch into arterioles, don’t contain valves

Veins

larger diameter lumen, thinner and less muscly walls than arteries, BP and flow rate are lower, SL valves ensure blood flow in 1 direction to prevent backflow

Capillaries

form a vast network that penetrates all tissues + organs in body, blood collects into venules → veins → heart, thin wall

What does ECG stand for and what is it

Electrocardiogram, a trace of the voltage changes produced by the heart

Hydrostatic pressure

the force exerted by a fluid against a wall

Which part of the heart controls the heartbeat

The Sino-atrial node which acts as a pacemaker

how does the Sino-atrial node control the heartbeat:

• Both atria contract in reaction to a wave of _____ ______ at the SAN. 

• The ventricles are insulated from the atria by a thin layer of connective tissue but not the atrio-ventricular node (AVN). The electrical stimulation only spreads to the ventricles from this point. The AVN introduces a delay in the transmission of the electrical impulse. The ventricular muscles don’t contract until after the ____ _____ have stopped.  

• The AVN passes the excitation down the nerves of the bundle of ___, the left and right bundle branches and to the apex of the heart. The excitation is transmitted to _____ fibres of the ventricle walls. 

• The impulses cause the cardiac muscle in each ventricle to _____ simultaneously, from the apex upwards. 

• This pushes blood up to the aorta and pulmonary artery, emptying the ventricles completely.  

electrical stimulation, atrial muscles, His, Purkinje, contract

Red blood cells (erythrocytes)

Biconcave discs, large SA, more oxygen can diffuse across membrane, no nucleus so more room for Hb, maximises oxygen carrying capacity

How is carbon dioxide transported in the body (3 ways)

dissolved in plasma 5%, associated with Hb to form carbaminohaemoglobin 10%, as hydrogen carbonate ions 85%

Reactions in a red blood cell:

1. ___ in the blood diffuses into the RBC. 

2. Carbonic anhydrase catalyses the combination of CO2 with H2O, making _____ ___. 

3. Carbonic acid dissociated into H+ and _____ ions. 

4. HCO3- ions diffuse out of the RBC into the ____. 

5. To balance the outflow of negative ions and maintain _______ _____, chloride ions diffuse into the RBC from the plasma. This movement is called the _____ ____. 

6. H+ ions cause oxyhaemoglobin to dissociate into oxygen and haemoglobin. The H+ ions combine with the haemoglobin to make _______ ___. This removes hydrogen ions and so the __ of the RBC does not fall. 

7. ______ diffuses out of the RBC into the tissues.  

CO2, carbonic acid, HCO3-, plasma, electrochemical neutrality, chloride shift, haemoglobonic acid, pH, oxygen

The Bohr effect

at higher partial pressure of carbon dioxide, the curve shifts more to the right, Hb has a lower affinity for oxygen so it is more readily released

Function of the chordae tendineae

connect AV valves to papillary muscles within ventricles, prevent backflow of blood into atrium