3.8 transport in animals

what is the need for transport systems?

• as organisms get bigger, the distance between the cells get greater

• as diffusion is only effective over very short diffusion distance, the organism won’t survive

• organisms therefore need a specialised transport system to move substance around the body

how are exchange systems adapted to maximise effectiveness?

• thin for short diffusion distance

• large surface area so lots of a substance can diffuse at once

• good blood supply to maintain a concentration gradient

what are the features of a transport system?

• transport medium

• vessels to transport

• pump to transport medium

• medium which flows in one direction (valves)

• ability to control flow of medium suit the changing needs of the organism

what are the 4 types of circulatory systems?

• single closed

• double closed

• open circulatory system

• closed circulatory system

what is the single closed circulatory system?

• only passes through the heart once for each complete circuit of the body

• the heart had 2 chambers

• because it goes through 2 sets of narrow vessels, the pressure is low which limits exchange process

what is the double closed circulatory system?

• the blood travels twice through he heart each circuit

• this ensures relatively high pressure and fast flow of blood

what are advantages of double circulation?

• the blood only travels through 1 capillary network before retuning to heart

• this maintains high pressure and steep concentration gradient

what is the close circulatory system?

• the blood is enclosed in blood vessels and doesn't come in direct contact with cells

• the blood is pumped under pressure and things leave through walls of the blood vessels

• the volume of blood flowing can be adjusted by widening or narrowing blood vessels

what is the open circulatory system?

• the blood (haemolymph) flows freely from the heart into body cavities (haemocoel) and comes into direct contact with the cells

• this is where change takes place before returning to heart through open-ended vessels

• no transport of O₂ or CO₂ as directly exchanged from tracheoles

what is the function of an artery?

• carry blood away from the heart

what is the structure of an artery? (outside to inside)

• tunica externa (adventita)

• tunica media

• tunica intima

• narrow lumen

what is the structure/function of tunica externa in artery?

• mostly made of collagen and elastic fibres

• strong protein that protects the blood vessel from over-stretching

what is the structure/function of tunica media in artery?

• thick layer of smooth muscle and elastic tissue

• muscle which withstands high pressure, can contract to narrow the lumen and reduce blood flow

• elastic tissue which maintains high blood pressure by stretching and recoiling

what is the structure/function of tunica intima in artery?

made up of:

• endothelium which is one cell thick, smooth, reduces friction for free blood flow

• connective tissue

• elastic fibers

what is the function of the narrow lumen in artery?

• helps maintain high blood pressure

what is the function of the arterioles?

• carry blood from an artery to the capillaries

what is the structure of the arterioles and why?

• contains rings of smooth muscle which contract and constrict and the diameter of the arteriole

• this increases resistance to flow and reduces the rate of flow of blood which diverts the flow to parts of the body that are demanding more oxygen

what is the structure of capillaries and why?

• very narrow diameter which reduces blood flow to allow exchange between blood and surrounding cells more efficiently

• thin walls only one cell thick, reduces the diffusion distance

• walls are leaky to allow plasma and dissolved substances to leave the blood

what are capillary beds?

• network of capillaries running though tissues

what is precapillary sphincters?

• capillary beds which regulate the flow of blood to tissues

what is the purpose of venule?

• transport blood from capillaries to veins

what does the venula walls consist of?

• muscle

• elastic

• collagen

what is the structure of a vein? (outside to inside)

• tunica externa (adventita)

• tunica media

• tunica intima

• large lumen and valve

what is the structure/function of the tunica externa in veins?

• mostly made of collagen and elastic fibres

• strong protein that maintains the shape of the vein, prevents collapse under low pressure

what is the structure/function of the tunica media in veins?

• thin layer of muscle and elastic fibres

• much thinner in veins

• no need for thick muscle as don’t need to withstand high pressure

what is the structure/function of the tunica intima in veins?

made up of:

• endothelium-one cell thick, smooth and reduces friction for free blood flow

• connective tissue

• elastic fibres

why do veins have a large lumen?

• low blood pressure

why do veins have valves?

• prevents the backflow of blood

• blood flows in 1 direction

how do valves work in veins?

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what is tissue fluid?

• formed by plasma leaking from capillaries

• it surrounds cells and supplies them with oxygen and nutrients

• formed at the arteriole end of capillary beds

• drained from the cells by lymph vessels and venules

what is hydrostatic pressure?

• the pressure caused by a fluid pushing against the container that its’s within

what is oncotic pressure?

• the pressure created by the osmotic effects of the solutes in the solution

at the arterial ends which pressure is bigger?

• hydrostatic pressure > oncotic pressure

at the venue ends which pressure is bigger?

• oncotic pressure > hydrostatic pressure

why is there oncotic pressure?

• in blood plasma we have proteins such as albumin

• these are highly hydrophilic and lower water potential of the blood plasma in capillary

• so tendency of water to move back to blood by osmosis

what is the purpose of the lymphatic system?

• drain surplus tissue fluid away from the cells

• supports immune system by producing and containing lymphocytes (type of WBC)

• helps fat and fat soluble vitamin absorption

how much tissue cells drain into lymphatic system instead of back into the venule?

• 10% drains into lymphatic system, where it forms a lymph

• the lymphatic system drains into the circulatory system near the vena cava vie the thoracic duct

why does blood travel through the heart twice for each circuit?

• to ensure relatively high pressure, fast flow of blood

what do the coronary arteries do?

• supply the heart muscles itself with oxygen and glucose needed for respiration

what happens if coronary arteries become constricted?

• arteries become more narrow and restricts the blood flow to the heart muscles

• less oxygen and less glucose pass through

• less respiration to release energy for the heart to contract

how can you treat cardiovascular disease?

• using a stent

• a tube is inserted into the artery to keep it open to make sure the blood can pass through

what are the 2 branches of the vena cava?

• superior

• inferior

what does the superior vena cava do?

• brings in blood from head and upper parts of the body

what does the inferior vena cava do?

• brings in blood from lower parts of the body

why is the left ventricle thicker than the right?

• left ventricle pumps blood around the whole body whereas right only pumps to the lung

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what is the tissue separating the left and right side of the heart called?

• septum

what does systole mean?

• contracting

what does diastole mean?

• relaxing

explain the cardiac cycle?

• both atria and ventricle are in diastole

• blood flows into atria through vena cava and pulmonary vein, causes pressure in atria to rise

• pressure in atria > pressure in ventricle

• AV valves open so blood flows from atria to ventricle

• atria systole takes place, pushes remaining blood into ventricle, stretching ventricle

• ventricular systole takes place, pressure increases

• ventricular pressure > atrial pressure

• AV valves close, prevents movement of blood back into atria

• semi-lunar valves in pulmonary artery and aorta also open, blood pumped out of heart

• ventricle diastole, ventricular pressure is lower than pulmonary artery, semi-lunar valves close

explain what happens on this part of the graph

explain what happens on this part of the graph

explain what happens on this part of the graph

explain what happens on this part of the graph

what is the sound the heart makes described as?

• lub-dub

what happens during the lub sound of the heart?

• AV valves closing due to contraction of ventricles

what happens during the dub sound of the heart?

• semi-lunar valves closing as a result of the back flow from the aorta and pulmonary artery as the ventricles relax and pressure is lower

what is systolic blood pressure?

• maximum blood pressure

• occurs when ventricles are contracting (at the end of the cardiac cycle)

what is diastolic blood pressure?

• minimum blood pressure

• occurs when ventricles are relaxed and filled with blood (at the beginning of cardiac cycle)

how do you record blood pressure, layout wise?

• systolic blood pressure / diastolic blood pressure

• e.g. 120/80 mm Hg

what does diastolic pressure give the clearest indication of?

• resistance to flow in blood vessels

what is blood pressure?

• measured in arteries

• determined by cardiac output and resistance to flow of blood in vessels

• resistance to flow is affected by diameter of blood vessels

• narrow vessels (vasoconstriction)

• wider vessels (vasodilation)

what factors affect blood pressure?

• cardiovascular centre

diameter of blood vessels controlled by stimulation of sympathetic and parasympathetic nerves

• smoking

nicotine causes vasoconstriction

build up of fatty deposits in vessels

• diet

high fat diet leads to build up of fatty deposits in blood vessels

• adrenaline

causes selective vasoconstriction and vasodilation

• increases in blood viscosity

excess water loss (sweating / excessive urination)

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what is the mass of specialised cells in the right atrium called?

• Sino-atrial node (SAN)

• In gsce this was called a pacemaker

why are pacemaker cells myogenic?

• initiates its own heart beat

how is a heartbeat established? Step by step

1. The SAN produces electrical impulses which cause both atria to contract (systole)

2. This forces open the AV valves, blood flows into ventricles. There is a band of non-conducting fibres which prevents the atria sending impulses to the ventricles

3. A patch of muscle fibres,AVN, conducts electrical impulses through the Bundle of His to the tip of the ventricles. There is a short delay in this node to allow ventricles to fill up with blood before contracting the Purkyne tissue

4. The 2 ventricles contract, base upwards, the Av valves shut and blood passes through semilunar valves into the arteries

5. as the ventricles are contracting, the atria relax and fill up with blood

what is heart rate?

• number of beats per minute

how would you calculate heart rate?

• beats per minute = heart rate

what is stroke volume?

• volume of blood (cm³) pumped by heart in 1 beat

how would you calculate stroke volume?

• stroke volume = blood cm³ per beat

what is cardiac output?

• stroke volume multiplied by the heart rate gives the amount of blood (cm³) pumped by heart 1 min

how would you calculate cardiac output?

• cardiac output (cm³ min) = heart rate x stroke volume

what do cardiac muscle consist of?

• fibres that branch, producing cross-bridges

why is it good that cardiac muscles consists of fibres that branch?

• help the stimulus to spread around the heart, producing a squeezing effect

why do cardiac muscles have a lot of mitochondria?

• to supply energy for contraction and are separated by intercalated discs which helps to synchronise the contraction

what are features of involuntary cardiac muscle?

• myogenic

• intermediate contraction speed

• cells branch and interconnect for simultaneous contraction

• uninucleated

• has striation (bands)

• connected by intercalated discs (low electrical resistance so impulses pass through easily)

what are electrocardiograms (EEGs) used for?

• to monitor electrical activity of the heart

what is the process for getting a EEG?

• EEG leads are attached to the body and a small amount of gel is applied which allows the electrical impulses of the heart to be more easily transmitted to the heads

how does a healthy persons EEG looks like?

what does each letter mean?

• P = atria contraction (only very small)

• Q = electrical impulses going down the Bundle of His

• QRS = ventricular contraction

• T = ventricular repolarisation

how would you calculate heart rate?

what is bradycardia?

• heart rate of <60bpm

what is normal heart rate?

• 60-100bpm

what is tachycardia?

• heart rate of >100bpm

• normally 100-160bpm

name these types of rhythms

1. bradycardia

2. normal rate

3. tachycardia

what are the two ventricular conditions?

• ventricular fibrillation

• ventricular tachycardia

what is ventricular fibrillation and how does it look like?

• impulses originating from several places in ventricles at a high rate

what is ventricular tachycardia and how does it look like?

• rapid heart rhythm originating from ventricles

what is atrial fibrillation and how does it look like?

• Atria beating more frequently than ventricles so no clear P wave is seen

what is ectopic heartbeat?

• when either the atria or ventricle has an extra beat

how would ectopic heartbeat of ventricles having an extra beat look like?

what are key facts about oxygen?

• low solubility in water

• only about 3ml of O₂ are dissolved in each litre of plasma

• If we have a total plasma volume of 3-5 litres only about 9-15ml of O₂ can be carried in the dissolved states

• resting body requires 250ml of O₂ per minute

what percent is oxygen transported for both ways?

• 98.5% combines with haemoglobin

• 1.5% is dissolved in the plasma

what are advantages of haemoglobin in red blood cells?

1. Hb is close to the enzymes that maintain or vary the binding property

2. Within RBCs, Hb doesn’t affect osmotic pressure of plasma

3. RBC’s clear stagnant plasma near capillary walls making exchange of O₂, CO₂, nutrients and waste more efficient

what is the structure of Hb?

• 2 alpha-globin polypeptide chain, 2 beta-globin polypeptide chain

• each polypeptide chain has it’s own tertiary structure

• haem group is a ‘prosthetic group’ since it contains Fe⁺

• so haemoglobin is a conjugated protein as has a non-protein attached

what is the short hand way of saying partial pressure of oxygen?

• pO₂

what is partial pressure?

• the individual pressure exerted independently by a particular gas within a mixture of gases

• (basically conc in a gas)

how many oxygen molecules can Hb transport?

• 4 oxygen molecules