3:Exchange and Transport Flashcards
What are the standard exchange surface characteristics?
- Large SA:V
- Thin, for a short diffusion pathway
- Moist, allows molecules to dissolve so they can diffuse
- Maintain a steep concentration
What happens to the SA:V the bigger an organism?
Surface area to volume ratio decreases
What is the pathway of air entering a locusts?
Spiracle —> Trachea —> Tracheole —> Indiviual cells
Describe the intake of airflow process in a locust?
1) Air flows through spiracles (each segment has a pair of spiracles)
2) Air travels from the tracheal tubes which run from the body surface to the tissues
3) Tracheal tubes branch off into a series of tracheoles which reach cells/tissue
What are the two ways gas exchange takes place in an insect?
- Diffusion gradient
- Ventilation by rhythmic abnormal movements
How does ventilation by rhythmic abnormal movements help gas exchange?
It further speeds up the exchange of respiratory gases by generating mass movement in and out of the tubes
Why do insects have a separate tracheal system instead of relying on blood to transport oxygen around the body?
- Insects have an open circulation -> they cannot easily direct the flow of blood to tissue that need it most
- Insects rely on diffusion and exchange of oxygen as a gas is more efficient
Why is the tracheal fluid withdrawn into the body when the tissue is very active?
This is to increase the surface area over which the exchange can occur
What is trachea in an insects exchange system lined with?
Chitin
Describe the pathway of gas exchange in fish.
1) The mouth is opened and the floor of the buccal cavity is lowered, this increases the volume and decreases the pressure so that water flows in
2) The volume of the operculum cavity is then increased and its pressure decreases. The floor of the buccal cavity starts to move up to increase the pressure
3) Water flows from buccal cavity to the operculum cavity where the gills are found
4) Gases can be exchanged between the blood in blood capillaries of the lamellae and water
Why is a countercurrent flow system used in fish?
In parralel flow, the concentration gradient will level out when the oxygen level in the blood and water are at 50%. Therefore diffusion stops.
However in countercurrent flow, the blood will continue to absorb oxygen from water as the concentration gradient doesn’t level out.
What are the adaptations of gills?
- several gill filaments and gill lamellar to increase the surface area
- gill filaments are thin for short diffusion path
- gill lamellar have a good blood supply and countercurrent mechanisms to maintain a high concentration gradient
Outline the passage of air in the mammalian gas exchange system?
Nose/mouth —> Trachea —> Bronchi —> Bronchioles —> Alveoli
What are the features of the trachea?
- Lined with ciliated epithelium
- Surrounded by ‘C’ shaped cartilage rings
- Surrounded by smooth muscles
Why does the trachea have ‘C’ shaped cartilage rings?
Protects it from collapse and provides support
What does the trachea have smooth muscles?
They contract and relax to increase and decrease the diameter of the trachea
What are the features of the bronchi?
- branched into 2 bronchus
- lined with ciliated epithelium (but less goblet cells than trachea)
- cartilage is irregular not in rings allowing more flexibility
- contains elastic fibres and smooth muscles
What are the features of the bronchioles?
- no cartilage or goblet cells
- walls contain smooth muscles
- it has elastic fibres
What is the passage of air in the different types of bronchioles?
Bronchiole —> Terminal Bronchiole —> Respiratory Bronchiole —> Alveolar Duct
What are the features of the alveoli?
- moist lining
- single cell thick lining of epithelial cells
- surrounded by very thin blood capillaries (usually one cell thick)
- contains elastic fibres
- contains lung surfactants
Why does the alveoli have a moist lining?
So gases can dissolve and diffuse faster
What is the lung surfactant?
A phospholipid that coats the surfaces of the lungs
Why do alveoli need lung surfactants?
Without it, the watery lining of the alveoli would create a surface tension which would cause them to collapse.
Is inspiration (inhaling) an active or passive process?
Active process
What is the process of inhalation?
1) The external intercostal muscles contract and the diaphragm contracts and flattens. This causes the ribcage to move up and out
2) Thoracic volume increases
3) Thoracic pressure decreases
4) Air flows into the lungs to equalise the pressure difference
Is expiration (exhaling) an active or passive process?
Largely passive process
What is the process of exhalation?
1) The external intercostal muscles relax and the diaphragm relaxes and moves up. This causes the ribcage to move down and in
2) Thoracic volume decreases
3) Thoracic pressure increases
4) Air flows out of the lungs to equalise the pressure difference
What is tidal volume?
The volume of air breathed in (or out) in one normal breath
What is the breathing rate?
The number of breaths per minute
What is the ventilation rate?
Total volume of air breathed in and out in one minute
What is the vital capacity?
The largest volume of air you can breathe in or out in one breathe
What is the inspiratory reserve volume?
Extra air above the tidal volume you can breathe in a forced breath
What is the expiratory reserve volume?
Extra air you can breathe out in a forced breath
What is the residual capacity?
Air you cannot empty from your lungs
What is the total capacity?
The sum of the vital capacity and residual capacity
How do you measure oxygen consumption?
1) Use soda lime to absorb the carbon dioxide
2) The trace will gradually fall as the breathing rate or volume in the chamber reduces
3) Measure how much the trace drops in a set time
4) Work out the volume of oxygen consumed per minute
Explain the need for transport system in multi-cellular animals?
1) SA:V is too small so diffusion is too slow
2) Distance is too great —> cannot rely on diffusion alone
3) High metabolic rate and waste production (more metabolically active so higher demand for nutrients)
What are the features of a good transport system?
1) Fluid or medium to carry nutrients + oxygen
2) A pump to create pressure to push the fluid
3) Exchange surfaces to enable oxygen + nutrients to enter the blood and be removed
4) Tubes or vessels to carry the blood
What does an open system consist of?
- a heart that pumps a fluid called haemolymph through shirt vessels into a large cavity called the haemocoel
- blood is not always enclosed in blood vessels
Why can’t humans have an open system?
1) Humans are too large to rely on an open system whereas insects are small so blood doesn’t meed to travel as far.
2) An open system can’t maintain a pressure so it’s slow
3) In an open system the tissue and cells are bathed in blood whereas I’m a closed system the vessels allow blood to be carried out to specific organs
5) A closed system can respond to external changes e.g. vasodilation
What is a closed circulatory system?
When the blood is fully enclosed within the blood vessels at all times
What are the advantages of a closed circulatory system?
- maintains high blood pressure —> regulate pressure as well
- blood can be deviated
- respond to external stimuli (thermoregulation)
What is a single closed circulatory system?
Blood flows only once through the heart in one circulation.
Only two chambers (atrium and ventricle)
What is the pathway of blood in the single closed circulatory system of fish? (EDIT)
Deoxygenated blood leaves the ventricle to gill capillaries, blood gets oxygenated by gaseous exchange. The gills have many capillaries for gas exchange so the blood pressure is low after going through the gill capillaries, blood gets oxygenates by gaseous exchange. The gills have many capillaries for gas exchange so the blood pressuremismlowmafteer going through the gill cappilaries. Low pressure blood then goes directly to he body which has a large number of cappilaifes.
What does is mean when it says the cardiac muscles in the heart are myogenic?
They can initiate contractions by generating their own electrical impulse
What are the two circulations in double circulation?
- Systematic Circulation
- Pulmonary Circulation
What happens during systematic circulation?
1) The left ventricle contracts
2) The semi lunar valve opens
3) Oxygenated blood enters the aorta
4) Aorta transports oxygenated blood to upper and lower parts of the body
5) Cells use oxygen for respiration and the blood gets deoxygenated
6) Deoxygenated blood is transported by superior and inferior vena cava to the right atrium
7) The right atrium contracts, tricuspid valve opens and the deoxygenated blood enter the right ventricle
What happens during the pulmonary circulation?
1) The right ventricle contracts
2) Semi-lunar valve opens
3) Deoxygenated blood enters the pulmonary artery
4) The pulmonary artery transports the deoxygenated blood to the lungs
5) Gas exchange takes place in the lungs, blood gets oxygenated
6) Oxygenated blood is transported via pulmonary vein to the left atrium
7) Through the bicuspid valve it goes to the the left ventricle
What are the three stages of the cardiac cycle?
- Atrial systole
- Ventricle systole
- Diastole
What happens during the atrial systole?
1) Blood flows into both atria and their volume increases, the muscles of the atria contract to increase the pressure
2) The pressure behind the valves is greater forcing the valves to open
3) Blood starts to flow from atria to ventricles
4) The semi-lunar valves in the vena cava and the pulmonary valve close
5) Pressure starts to decrease in the atrium
What happens during the ventricular systole?
1) The muscles of ventricles contract
2) The pressure inside the ventricles increases
3) The tricuspid & bicuspid atrioventricular valves close
4) The semi-lunar valves in the aorta and the pulmonary artery open
5) Pressure decreases
What happens during the diastole?
1) Pressure in the ventricles decrease
2) Semi-lunar valves in the aorta and the pulmonary arteries close
3) All the heart muscles relax
4) Blood flows into the atria from vena cava and pulmonary vein
5) Blood pressure remains low inside the atria and ventricles
What are valves controlled by?
The pressure gradient
What causes a valve to open?
High pressure behind the valve
What causes the valves to close?
High pressure in front of the valve.
What is the ventricular pressure during the atrial systole?
Low pressure
Why is the ventricular pressure low during the atrial systole?
Blood hasn’t entered the ventricles
What is the ventricular pressure like in the ventricular systole?
Increases rapidly
Why does the ventricular pressure increase rapidly during the ventricular systole?
The ventricles contract
What happens to the valves during the ventricular systole?
Atrioventricular valves close and semi-lunar valves open
What is the ventricular pressure during the diastole?
Low as it is a passive process
What is the atrial pressure during the atrial systole?
Gradually increasing
Why does the atrial pressure gradually increase during the atrial systole?
Because the atria contracts
What is the atrial pressure during the ventricular systole?
Starts to decrease
Why does the atrial pressure start to decrease during the ventricular systole?
Because the blood flows into the ventricles and the atrial muscles relax
What is the atrial pressure during the diastole?
Slightly increases at the beginning
Why does the atrial pressure slightly increase at the beginning of the diastole?
Because the blood flows passively into the aorta from the vena cava and the pulmonary vein
What is the aortic pressure in the atrial systole?
The pressure remains the same as the blood hasn’t entered the aorta yet
What is the aortic pressure in the ventricular systole?
Starts to increase
What is the aortic pressure in the diastole?
Decreases
What is cardiac output?
The amount of blood pumped around the body
How do you calculate cardiac output?
Cardiac output = Stroke volume x heart rate
What is the stroke volume?
The volume of blood pumped by the left ventricle in each heart beat
What is the heart rate?
The number of times the heart beats per minute
What happens to the membrane of muscle cells when they are at rest?
It becomes polarised
What happens to the membrane of muscle cells when the charge distribution is reversed?
The membrane is depolarised and it causes them to contract
In terms of electrical activity, what happens during the atrial systole?
- The sino-atrial node (SAN) sends a wave of excitation (depolarisation) throughout the atria
- This causes the walls of the atria to contract almost simultaneously
Where is the sino-atrial node (SAN) found?
In the upper left wall of the right atrium
In terms of electrical activity, what happens during the ventricular systole?
- SAN sends electrical excitations to the atrio-ventricular node (AVN), causing the AVN to send excitation through the bundle of His and then into the Purkyne tissue.
- This causes depolarisation of cardiac muscles
- There is a time gap between the generation of waves of excision by the SAN and the receival of excitations from the AVN
What does the P wave represent in an ECG?
- The depolarisation of the atria
- The atrial systole
What does the QRS complex represent in an ECG?
The electrical impulses as it spreads through the ventricles and indicates the ventricular depolarisation
What does the T wave represent in an ECG?
- the diastole
- the ventricular repolarisation
What is bradycardia?
Slower than normal heart beat - less than 60bpm
What is tachycardia?
Faster than normal heart rate - more than 100bpm
What is ectopic beat?
Extra beats, followed by gaps
What is atrial fibrillation?
Irregular heartbeat rhythm
Why does blood pressure drop from aorta to arteries and from the arteries to capillaries?
- distance from heart increases
- blood flows into larger number of vessels
- total cross-sectional area of the arteries is greater than the aorta
- total cross-sectional area of capillaries is greater than the aorta/arteries
Why is it important that the blood pressure drops in the capillaries?
- capillary wall is only one cell thick
- high pressure would burst/damage capillary walls
- reduce chance of tissue fluid build up (causing oedema)
What is the main protein found in blood plasma?
Albumins
What are albumins?
Transport protein found abundantly in the blood plasma
What is hydrostatic pressure?
Pressure inside the blood
What causes hydrostatic pressure?
The contractions of the heart
How is tissue fluid formed from plasma?
- The effect of hydrostatic pressure is greater than the oncotic effect at the arterial end, which means water (with some dissolved substances) is forced out through the capillary wall as it has pores.
- The effect of oncotic pressure is greater than the hydrostatic pressure at the venous end, therefore some fluid returns back to the capillaries.
- Valves/pores at lymph vessels allow fluid and proteins out of the tissue fluid into lymph vessels
What is lymph?
A colourless/pale yellow fluid similar to tissue fluid (but contains more lipids)
What happens to excess tissue fluid that doesn’t return to the capillaries?
The excess tissue fluid drains into the lymphatic system, where it is formed as lymph
