3.1.2 - Transport In Animals Flashcards (PMT)

Why do multicellular organisms require transport systems?

• Large size

  • Small SA:V ratio

  • Subsequently high metabolic rates

• Demand for oxygen is high

  • Need a specialised system to ensure string supply to all respiring tissues

Summarise the different types of circulatory system.

• Open

  • Blood can diffuse out of vessels (e.g. insects)

• Closed

  • Blood confined to vessels (e.g. fish, mammals)

  • Single

    • Blood passes through heart once per circuit of the body

  • Double

    • Blood passes through heart twice per circuit of the body

Relate the structure of arteries to their function.

• Thick muscular walls

  • To handle high pressure without tearing

• Elastic tissue

  • Allows recoil to prevent pressure surges

• Narrow lumen

  • To maintain pressure

Relate the structure of veins to their function.

• Thin walls

  • Due to lower pressure

• Require valves

  • To ensure blood doesn’t flow backwards

• Have less muscular and elastic tissue

  • As they don’t have to control blood flow

Relate the structure of capillaries to their function.

• Walls only one cell thick

  • Short diffusion pathway

• Very narrow

  • Can permeate tissues

  • Red blood cells can lie flat against the wall

    • Effectively delivers oxygen to tissues

• Numerous and highly branched

  • Providing a large SA

Relate the structure of arterioles and venules to their function.

• Branch off arteries and veins

  • To feed blood into capillaries

• Smaller than arteries and veins

  • So change in pressure is more gradual as blood passes through increasingly smaller vessels

What is tissue fluid?

A watery substance containing glucose, amino acids, oxygen, and other nutrients

• Supplies these to the cells

• Also removes any waste materials

What types of pressure influence formation of tissue fluid?

• Hydrostatic pressure

• Oncotic pressure

Where is hydrostatic pressure higher?

Higher at arterial end of capillary than venous end

What does oncotic pressure do?

• Changes water potential of capillaries as water moves out

  • Induced by proteins in the plasma

How is tissue fluid formed?

• As blood is pumped through increasingly smaller vessels

  • Hydrostatic pressure is greater than oncotic pressure

    • So some plasma leaks out of the gaps in the walls of the capillaries

      • To surround the cells of the body

• Tissue fluid then exchanges substances with the cells

How does tissue fluid differ from blood and lymph?

• Tissue fluid is formed from blood, but does not contain:

  • Red blood cells

  • Platelets

  • Various other solutes usually present in blood

• After tissue fluid has bathed cells it becomes lymph

  • So contains less oxygen and nutrients and more waste products

Label this diagram of the human heart.

Describe what happens during cardiac diastole.

1. The heart is relaxed

2. Blood enters the atria

   • Increases the pressure

     • Pushes open atrioventricular valves

3. Blood is thus allowed to flow into ventricles

4. Pressure in heart is lower than in the arteries

   • So semilunar valves remain closed

Describe what happens during atrial sytole.

• The atria contact

  • Pushes any remaining blood into the ventricles

Describe what happens during ventricular systole.

1. The ventricles contract

2. Pressure increases

   • Closes the atrioventricular valves to prevent backflow

   • Opens the semilunar valves

3. Blood flows into the arteries

How do you calculate cardiac output?

Cardiac output = heart rate x stroke volume

What does myogenic mean?

The heart’s contraction is initiated within the muscle itself, rather than by nerve impulses

Explain how the heart contracts.

1. SAN initiates and spreads impulse across atria

   • Atria contract

2. AVN receives, delays, then conveys impulse down the bundle of His

3. Impulse travels into the Purkinje fibres which branch across the ventricles

   • Fibres contract from bottom up

What is an electrocardiogram (ECG)?

A graph showing the amount of electrical activity in the heart during the cardiac cycle

Describe types of abnormal activity that maybe seen on an ECG.

• Tachycardia

  • Fast heartbeat (over 100 bpm)

• Bradycardia

  • Slow heartbeat (under 60 bpm)

• Fibrillation

  • Irregular, fast heartbeat

• Ectopic

  • Early or extra heartbeats

Describe the role of haemoglobin.

• Present in red blood cells

• Oxygen molecules bind to the haem groups

  • Are carried around the body

  • Then released where needed in respiring tissues

How does partial pressure of oxygen affect oxygen-haemoglobin binding?

• As partial pressure of oxygen increases, affinity of haemoglobin for oxygen increases

  • So oxygen binds tightly to haemoglobin

• When partial pressure is low, oxygen is released from haemoglobin

What do oxyhaemoglobin dissociation curves show?

• Saturation of haemoglobin with oxygen (in %)

• Plotted against partial pressure if oxygen (in kPa)

• Curves further to the left show the haemoglobin has a higher affinity for oxygen

Describe the Bohr effect.

• As partial pressure of carbon dioxide increases, conditions become acidic

  • So haemoglobin changes shape

• Affinity of haemoglobin for oxygen decreases

  • So oxygen released from haemoglobin

Explain the role of carbonic anhydrase in the Bohr effect.

• Carbonic anhydrase present in red blood cells

• Converts carbon dioxide to carbonic acid

  • Dissociates to produce H+ ions

• These combine with haemoglobin to form haemoglobinic acid

• Encourages oxygen to dissociate from haemoglobin

Explain the role of bicarbonate ions (HCO3-) in gas exchange.

• Produced alongside carbonic acid

• 70% of carbon dioxide is carried in this form

• In the lungs

  • Bicarbonate ions are converted back into carbon dioxide which we breathe out

Describe the chloride shift.

• The intake of chloride ions across a red blood cell membrane

• This repolarises the cells after bicarbonate ions have diffused out

How does foetal haemoglobin differ from adult haemoglobin?

• Partial pressure of oxygen is low by the time it reaches the foetus

  • So foetal haemoglobin has for oxygen than adult

• Allows both mother’s and child’s oxygen needs to be met