transport in animals exam questions Flashcards
State the meaning of the following terms:
- single circulatory system
- double circulatory system
- open system
- closed system
[4 marks]
Single Circulatory System - blood passes through the heart once for each circulation/cycle of the body
Double Circulatory System - blood passes through the heart twice for one complete circuit
Open System - blood is not always contained in vessels e.g. a heart that pumps blood like fluid called haemolymph through short vessels and into a large cavity called the haemocoel
Closed System - the blood is maintained inside vessels
Explain three reasons why mammals need a circulatory system whilst unicellular organisms do not [4]
SIZE
* Mammals are larger
* Cells deep in body
* But you need to get materials to all parts
* And diffusion would be too slow
ACTIVITY
* Mammals more metabolically active
* Need a rapid supply and removal of waste
SA:V Ration
* Large animals have a smaller surface area:volume ratio
* Diffusion alone would not be effective/would be too slow
List three reasons why a large, multicellular animal, such as a mammal needs a transport system. [3]
- Low/small surface area to volume ration
- Diffusion too slow/distance to great
- To supply enough oxygen/nutrients
- To prevent CO2/waste product building up
- Active
What is the function of the coronary artery [1 mark]
- Supply oxygen/nutrients to the heart muscle for aerobic respiration
- Remove carbon dioxide/waste
Explain why the wall of the left ventricle is thicker than the wall of the left atrium [4 marks]
- Need more muscle - to create more force
- To create higher pressure
- As has to pump blood against greater resistance/friction
- Also left ventricle pumps blood further - to all parts of the body (systemic circulation)
Explain why it is important that the two sides of the heart are completely separated [2 marks]
- Stops oxygenated and deoxygenated blood mixing
- Ensures oxygenated blood gets to the body while deoxygenated blood to lungs
- It also allows different pressures to be maintained on each side
- There would be a possible drop in blood pressure if there was a hole present
Explain the advantage of the ventricles contracting from the bottom upwards [1 mark]
- Allows the ventricles to empty completely
- This is because aorta and pulmonary artery are found at the top
Explain how pressure changes in the heart bring about the closure of the atrioventricular (bicuspid) valve [3]
- Ventricular systole (contraction of ventricle wall)
- Raises ventricular pressure
- When the pressure in ventricle is higher than atrial pressure
- It pushes valve shut
- Chordae tendinae prevents inversion
Describe how the action of the heart is initiated and coordinated [5]
- SAN initiates excitation
- Wave of excitation spreads over atrial wall/muscle
- This results in atrial systole (contraction of atria)
- In synchronization
- A short delay occurs at AVN
- Band of non-conducting collagen prevents excitation carrying straight on
- and then excitation spreads down septum
- through bundle of His and Purkyne fibres
- This results in the ventricles contracting from apex/bottom upwards
What is the advantage of the slow rate of conduction through the AVN [2 marks]
- Delays contraction of ventricles
- Until of the atria have contracted completely filling the ventricles
Suggest one advantage of the high rate of conduction in the Purkyne fibres which carries impulses through the walls of the ventricles [1 mark]
Causes the rapid contraction of ventricles together
How would cutting the nerve connections from the brain to the SAN affect the heart? [1 mark]
- It wouldn’t as the Heart is myogenic
- SAN initiates beat
- SAN generates impulses that cause contraction.
Describe how an artificial pacemaker regulated heart activity [2 marks]
- Supplies electrical impulses to the heart
- Replaces action of damages conducting tissue
- Provides regular electrical impulses
Describe the role of the Atrioventricular node in the production of the heart beat [1 mark]
- Produces electrical impulses in response to electrical activity from the SAN
- Causes a time-delay
- Passes on electrical activity from the SAN to the bundle of His
Describe the role of the Bundle of His [1 mark]
Carries electrical impulses from AVN to purkyne fibres extremely quickly
Describe the role of the purkyne fibres [1 mark]
This cause contraction of ventricles from the base simultaneously
The beating of the heart is myogenic
Explain what this means [2 marks]
- SAN/sinoatrial node (starts each beat)
- Beats initiated by the heart
- Doesn’t need stimulation by nerve/nerve impulses to contract/beat
During the electrical stimulation of the heart, there is a short delay between the excitation of the atria and excitation of the ventricles. Explain why the delay is essential. [2]
- To allow time for the atria to fully contract
- To allow time for atria to empty/ventricles to fill
- So that ventricles do not contact too early
The Purkyne tissue carries the excitation wave down the excitation wave down the septum to the apex of the heart. Explain why the excitation wave is carried to the apex. [2
- So that ventricular contraction starts at apex/base
- To push blood upwards - towards arteries
- Complete/efficient emptying of ventricles.
Describe how the structure of an artery is related to its function [6]
1) The artery has a narrow lumen
- to help maintain pressure
2) The artery has a generally thick wall
- to prevent bursting and withstand pressure
3) The wall is made up of three layers tunica intima, tunica media and tunica externa
Tunica Intima
* This is a smooth endothelium
* Made up of squamous epithelium
* Smoothness helps reduce friction
Tunica Media
* Elastic fibres- allows stretching to help prevent bursting and withstand and maintain pressure
* Collagen fibres - provide strength
* Smooth muscle - help maintain pressure (vasoconstriction)
Tunica Externa
* Mainly collagen fibres
* Some elastic fibres
Describe how the structure of a vein is related to its function [6 marks]
1) The artery has a relatively large lumen - helps accommodate large volumes of blood
2) Veins have valves - help prevent back flow and allow blood to move towards heart
3) The wall is made up of three layers tunica intima, tunica media and tunica externa
Tunica Intima
* This is a smooth endothelium
* Made up of squamous epithelium
* Smoothness helps reduce friction
Tunica Media
* Thin but does have muscle and elastic tissue (less than artery)
* As only needs to withstand low pressure
* Also allows skeletal muscle to squeeze veins
Tunica Externa
* Mainly collagen fibres (less than artery) - provides strength
State ways in which the wall of an artery is different from the wall of a vein [2 marks]
- Arteries have no valves
- Arteries have thick layer of smooth muscle and elastic tissue (tunica media)
- Arteries have more collagen (tunica externa)
Blood in arteries has a high hydrostatic pressure. State how this hydrostatic pressure in the heart is generated [1 mark]
Contraction of ventricle wall (ventricular systole)
Explain why the hydrostatic pressure of the blood drops as blood moves away from the heart [2 marks]
1) Arteries stretch and expand
2) There is more vessels
3) There is loss of fluid/plasma from capillaries
Explain how the structure of capillaries enables them to carry out metabolic exchange efficiently [5 marks]
- Thin wall (one cell thick) - creates a short pathway for easy diffusion
- Smooth endothelium - creates reduced friction/resistance and smooth flow
- Small gaps - allows nutrients out
- Narrow diameter - only one red blood cell can flow at a time (reduced rate of flow). This slows blood flow so substances can diffuse in and out
Describe and explain how the wall of an artery is adapted to both withstand and maintain high hydrostatic pressure [5 marks]
To withstand pressure:
* Wall is thick
* Thicker layer of collagen
* This provides strength
* Elastic fibers - allow it stretch to accommodate pressure
To maintain pressure:
* Elastic tissue
* To cause recoil and return to original size
* Thick layer of smooth muscle
* This constricts lumen/artery
Explain why it is important that the pressure changes as blood flows from the aorta to the capillaries [2 marks]
- Capillary is thin/only one cell thick
- High pressure would burst damage capillary
- This could result in odema
Describe how red blood cells are adapted to their function [8 marks]
- Contains Haemoglobin - to carry oxygen
- Flexible/elastic/stretchy/change shape - this allows red blood cells to fit/squeeze into capillaries
- Biconcave - gives increased surface are relative to its volume (for diffusion). Also means haemoglobin never far from cell surface
- No nucleus - to maximise room hemoglobin
- Lack of organelles (e.g. endoplasmic reticulum) increased room for Hb
- Small (about 7µm in diameter) - about the same size as a capillary
