Transport in Animals

What is the need for transport systems in multicellular animals

• Larger organisms have longer transport distances to exchange sites so simple diffusion alone is too slow

• Low SA:V ratio less surface area for absorption of nutrients and loss of waste - longer diffusion distance

• Higher level of metabolic activity

Open Circulatory System

• Transport medium can diffuse out blood vessels

Closed Circulatory System

• Blood is confined to blood vessels

Single Circulatory System

Blood only passes through the heart once per circuit

Double Circulatory System

• Blood passes through the heart twice per circuit

• Pulmonary Circuit carries blood heart —> lungs (pick up oxygen remove carbon dioxide)

• Systemic Circuit carries blood heart —> body (deliver oxygen)

Arteries Structure and Function

• Thick smooth muscle layer Withstand high pressure

• Elastic fibers – Allow stretching and recoiling for smooth flow.

• Narrow lumen – Maintains high pressure

• Collagen for support

• Dilate and Constrict to control blood volume

Arterioles Structure and Function

• Thicker muscle layer than arteries to restrict blood flow in capillaries

• Branch of arteries into narrow blood vessels - transport blood to capillaries

• Smaller than arteries to make pressure change more gradual

• Thin Collagen and elastic layer

Capillaries Structure and Function

• One cell thick squamous epitehlial cells short diffusion distance

• Highly branches for large surface area - maximise gas exchange

• Slows blood flow – Allows more time for diffusion

• Narrow - sqaush red blood cells - maximise diffuion

Venules Structure and Function

• Branch off of veins to transport blood to capillaries

• Smaller than veins to make pressure change more gradual

• Contains valves to prevent backflow

Veins Structure and Function

• Thin muscle layer - Low risk of damage as blood is carried at low pressure (DO₂ to heart)

• Wide lumen - helps blood flow by less pressure

• Contains valves to prevent backflow

• No collagen or elastic layer

How is tissue fluid formed?

• High hydrostatic pressure as arteriole end is wider diameter than capillary with same volume of blood

• Forces out water and small moleules out of gaps in capillaries

Why is tissue fluid useful

• All Substances e.g. water, glucose, amino acids, water, ions, oxygen can re - enter cells if needed

• Waste products picked back up and removed

Hydrostatic pressure

(pressure exerted by liquid)

oncotic pressure

(tendency of water to move into blood via osmosis)

Why does more blood move out capillaries than in?

Hydrostatic pressure is greater than oncotic pressure so net movement of liquid is out of blood capillaries

Why is oncotic pressure high

• Large molecules like plasma proteins are too large to fit through capillary gaps

• Water moves via osmosis to capillaries

• Once equilibrium is reached liquid left goes into lymphatic system

Why does cardiac muscle automatically contract and relax and never fatigue

It is myogenic

What do coronary arteries do

• Supply the cardiac muscle with oxygenated blood for aerobic respiration

• This provides ATP so cardiac muscle can continually contract and relax

Why is left ventricle wall thicker than right?

• So it can contract with more force and pump blood at a high pressure

• This is because it pumps blood out of aorta around whole body to recieve oxygenated blood

Why is right ventricle muscle thin

• Doesn’t need to contract with as much force - lower pressure only pumps to lungs

• Blood needs to flow through lungs and low pressure so doesn’t damage capillaries in lungs

• Blood flows slowly at low pressure allowing more time for gas exchange

Why are atria walls so thin

• Only pumps blood to ventricles which are very close needing minimal force

• Also assisted by gravity

Structure of Mammalian Heart and blood flow

Deoxygenated Blood —> Vena Cava —> Right atrium —> Right Ventricle —> Pulmonary Artery

Oxygenated Blood —> Pulmonary Vein —> Right Atrium —> Right Ventricle —> Aorta

Cardiac Cycle

1. Atrial Systole - Walls of atria contract decreasing volume increasing pressure above ventricles opening AV valve

2. Blood is forced into ventricles and ventricles are relaxed in diastole

3. Ventriuclar Systole When blood fills ventricle walls contract volume decreases/ pressure increases above atria closing AV valves close to stop bacflow

4. Ventricular pressure rises above aorta and pulmonary arterey opening SL valve forcing blood out heart

5. Diastole Atria relaxes starts to be filled with blood and then ventricles relax

6. Pressure in ventricles drop closing SL valve

7. Blood flows into atria via pulmnoary vein and vena cava till pressure rises above ventricles opening AV valves

8. Blood trickles passively into ventricles

How do you calculate Cardiac Output?

Heart Rate x Stroke Volume

What is cardiac output?

The volume of blood that leaves the ventricle in one minute

Heart rate

Heart beats per minute

Stroke volume

Volume of blood that leaves the heart each beat

Control of cardiac cycle

• Sinoatrial node releases a wave of The sinoatrial node (SAN) generates a wave of depolarization, causing the atria to contract (atrial systole).

• The depolarization reaches the atrioventricular node (AVN), where there is a slight delay to ensure the ventricles contract after the atria.

• The AVN sends the signal through the Bundle of His down the septum and into the Purkyne fibers.

• The ventricles contract from the apex upward, ensuring efficient blood ejection

• short delay as AVN transmits second wave - to allow atria to fill ventricles

• Heart repolarizes

Electrocardiogram

A machine which measures the waves of depolarisation for irregularities

Tachycardia

• When the heart is beating at over 100bpm - abonrmally fast

Bradycardia

When the heart is beating at less than 60bpm. May be too low, however fitter may contract harder

Fibrilation

Irregular heart beat or chaotic rhytm if heart

Ectopic Heartbeat

Additional heartbeats which are not in rhythm

How do saturation of O₂ pressure interact in Oxygen Dissosiactive Curve?

• Percentage Saturation of O₂ is lower at low O₂ Partial Pressure (affinity is low at respiring tissues dissociates)

• Percentage Saturation of O₂ is high at high O₂ Partial Pressure (high affinity at alveoli)

Why does the curve get steeper

• Due to cooperative binding O₂ binding causes conformational change in haemoglobin shape making it easier for further O₂ to bind.

Bohr effect

• High CO₂ conc reduces the affinity of haemoiglobin for O₂ as ph decreases

Why is Bohr effect useful

• Same partial pressure of O₂ at lower pH - high CO₂ SHIFTS TO RIGHT

• Far less oxygen is bound and is dissosciating at (site of repsiration)

Structure of haemoglobin

4 haem group with 2 alpha chains, 2 beta chains

shape is the oxygen dissociation curve

• Sigmoid/S

Describe oxygen dissociation curve for fetal and adult human haemoglobin.

• Fetal haemoglobin curve shifts to LEFT

• Same partial pressure of O₂ fetal Hba is more saturated with O₂

• This is because has to get O₂ from mothers haemoglobin - must dissosciate O₂ from adult to bind to fetal hba

What are the three ways CO₂ is transported?

• Dissolved in blood plasma

• As carbaminohaemoglobin

• 85% In rbcs as hydrogen carbonate ions

Cholride Shift

1. Carbonic anhydrase in rbcs catalyses H₂O and CO₂ to form Carbonic acid

2. Carbonic acid dissociates to form hydrogen ions and hydrogen carbinate ions

3. Haemoglobin binds to H ions and dissociates from O₂ forming haemoglobonic acid

4. Hydrogen carbonate ions diffuse out and chloride diffuses in - both negative