Module 2 Exchange and Transport

1
Module 2Exchange and Transport

• Unit One
• Cells, Exchange and Transport
• AS Biology
• OCR Specification

2
Exchange

• In groups
• discuss what is meant by the word exchange
• Apply the word exchange to a biological concept
• Exchange takes place over surfaces
• Write down features of a good exchange surface
• Which processes are used in the exchange of
  substances

3
Learning Outcomes

• Explain, in terms of surface areavolume ratio,
  why multicellular organisms need specialised
  exchange surfaces and single-celled organisms do
  not.

4
Exchanges between organisms and their environment

• Exchange can take place in two ways
• Passively (no energy is required)
• E.g. diffusion and osmosis
• Actively (energy is required)
• Active transport
• Pinocytosis and phagocytosis

5
Surface area to volume ratio

• Exchange takes place at the surface of an
  organism, but the materials absorbed are used by
  cells that mostly make up its volume.
• For exchange to be effective, the surface area of
  the organism must therefore be large compared
  with its volume.

6
Activity

• Cut out and make animals X and Y
• Compare the two animals with respect to
• Length
• Breadth
• Height
• Total surface area
• volume

7
Learning outcomes

• Explain, in terms of surface areavolume ratio,
  why multicellular organisms need specialised
  exchange surfaces and single-celled organisms do
  not.

8
Evolution of organisms

• A flattened shape
• A central region that is hollow
• Specialised exchange surfaces
• Large areas to increase the surface area to
  volume ratio

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Why organisms need special exchange surfaces

• Oxygen for
• Glucose as a source of
• Proteins for and
• Fats
• Water
• Minerals
• To remove waste materials

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Features of a specialised exchange surface

• Good exchange surfaces have
• A large surface area
• Thin barrier to reduce diffusion distance
• Large concentration gradient
• Fresh supply of molecules on one side
• Removal of required molecules on other side

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Specialised Exchange Surfaces

• Alveoli in the lungs
• Small intestine
• Liver
• Root hairs in plants
• Hyphae of fungi

12
Progress Question

• Very small organisms such as the amoeba do not
  have specialised gas exchange systems.
• Mammals are large, multicellular organisms and
  have a complex gas exchange system.
• Explain why the mammal needs such a system when
  an amoeba does not.

13
Progress Question - suggestions

• Why do we need gas exchange?
• Oxygen is needed for respiration
• Body needs to get rid of waste carbon dioxide.
• How do simple animals take in the oxygen they
  need?
• Diffusion through the surface membranes e.g.
  amoeba or flatworm

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Progress Question - suggestions

• Why cant multi-cellular organisms do this?
• Cells are too far away from the oxygen in the
  external environment.
• Need a specialised exchange surface.
• In humans the specialised gas exchange surface is
  the alveoli.

15
Learning Outcomes

• Describe the features of an efficient gas
  exchange surface, with reference to diffusion of
  oxygen and carbon dioxide across and alveolus.

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Gas Exchange

• Gaseous exchange is the movement of gases between
  an organism and its environment.
• Gas exchange takes place by diffusion.
• The rate of diffusion depends on three factors.
• The surface area of the gas exchange surface
• Difference in concentration
• The length of the diffusion pathway

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Alveoli

• Adaptations of alveoli to gas exchange
• Large surface area
• Thin walls of alveoli and blood capillaries
• Steep concentration gradient
• Good blood supply
• Ventilation
• Blood is constantly moving through the lungs to
  maintain the concentration gradients.
• The air in the alveoli is continually refreshed
  by ventilation.

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Alveoli and gas exchange

• Large surface area 70m2
• Extremely thin lined with squamous epithelium
  allows for rapid diffusion
• 0.1µm to 0.5µm thick
• Kept moist / surfactant
• Extensive capillary network
• Capillaries 7-10µm in diameter
• Blood flow through capillaries is slowed
• Ventilation

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Applying you knowledge

• Alf smoked for 40 years. He had a bad smokers
  cough and easily got out of breath. His health
  got worse so he went to see his doctor. The
  doctor said that he had emphysema. She explained
  that the coughing had damaged a lot of the
  alveoli in his lungs and reduced their surface
  area.
• Explain as fully as you can why Alf got out of
  breath easily.
• Alfs illness got worse. He couldnt walk very
  far and he had to breathe oxygen from a cylinder.
  Explain why.

20
Structure of the Mammalian Lung
21
Learning Outcomes

• describe the features of the mammalian lung that
  adapt it to efficient gaseous exchange
• outline the mechanism of breathing (inspiration
  and expiration) in mammals, with reference to the
  function of the rib cage, intercostal muscles and
  diaphragm

22
Pupil Activity

• Colour in the diagram of the lungs
• Take care to read all the information provided as
  you colour in.

23
Think!!

• Why is the volume of oxygen that has to be
  absorbed and the volume of carbon dioxide that
  has to be removed in mammals so large?
• Large organisms with large volume of living cells
• Maintain a high body temperature
• High metabolic rate
• High respiratory rate

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Mammalian Lungs

• Structure of the lungs
• Trachea
• Rib cage
• Intercostal muscles
• Bronchi
• Bronchioles
• Alveoli (site of gaseous exchange)
• 100µm 300µm in diameter
• 300 million in each lung

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Pupil Activity

• Design a poster using the information sheet
• 13.1 human gaseous exchange system
• Your poster should show the distribution of
  tissues and highlight the functions of each of
  the tissues
• cartilage
• Cilia
• goblet cells
• smooth muscle
• elastic fibres

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Learning Outcomes

• describe, with the aid of diagrams and
  photographs, the distribution of cartilage,
  ciliated epithelium, goblet cells, smooth muscle
  and elastic fibres in the trachea, bronchi,
  bronchioles and alveoli of the mammalian gaseous
  exchange system
• describe the functions of cartilage, cilia,
  goblet cells, smooth muscle and elastic fibres in
  the mammalian gaseous exchange system

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Ciliated Epithelium
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Cartilage
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Smooth Muscle
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Squamous Epithelium
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Distribution
Tissue / cell trachea bronchus bronchioles alveolus
Cartilage ? ? ? (not in the tiniest) ?
Goblet cells ? ? ? ?
Ciliated cells ? ? ? ?
Smooth muscle ? ? ? ? Very little
Squamous epithelium ? ? ? ?
Elastic fibres ? ? ? ?
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Functions of cells, tissues and fibres
34
Cartilage

• Flexible supporting material
• Incomplete rings support the smooth muscle
  keeping the tubes open.
• Prevents trachea and bronchi from collapsing when
  air pressure lowers during inhalation

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Cilia

• Synchronised movement to transport mucus towards
  the pharynx

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Goblet cells

• Produce the mucus that forms a thin layer over
  surface of the trachea and bronchi
• The mucus is sticky and traps bacteria. Pollen
  and dust particles, the air is filtered.

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Smooth muscle

• Contraction of the smooth muscle allows the
  bronchioles to constrict.
• This controls the flow of air to the alveoli.

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Elastic fibres

• Elastic fibres become stretched when the smooth
  muscle contracts, when the smooth muscles relaxes
  the elastic fibres recoil back into their
  original positions.
• This dilates the bronchioles.

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Difference in structure of Trachea, bronchi and
bronchioles

• Cartilage in trachea and bronchi keep airways
  open and air resistance low.
• Trachea has c-shaped rings
• Bronchi has irregular blocks
• Bronchioles have smooth muscle which contracts
  and elastic fibres to control their diameter

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Learning Outcomes

• outline the mechanism of breathing (inspiration
  and expiration) in mammals, with reference to the
  function of the rib cage, intercostal muscles and
  diaphragm

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Inhalation
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Exhalation
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Inspiration Expiration
Diaphragm Contracts and flattens Relaxes and pushed up by organs in abdomen
Rib cage (ribs and intercostal muscles) External intercostal muscles contract raising the ribs Internal
Volume of thorax
Pressure in chest cavity
Air movement
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Mammalian Lungs (1)

• Two reasons why mammals require a large and
  constant supply of oxygen are (1) and (2). The
  main organs for gaseous exchange are the lungs,
  which are connected to the outside by a tube
  called the (3). This branches into two (4), one
  of which enters each lung.

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Mammalian Lungs (2)

• The actual site of gaseous exchange is in the
  alveoli, which have a diameter of (5) and have
  walls made of (6) which is very thin, being only
  (7) in thickness. The total number of alveoli
  for both lungs is around (8) giving them a very
  large surface area of about (9).

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Gaseous Exchange in the alveoli (1)

• Gaseous exchange occurs in the alveoli, with the
  gas called (1) moving into the blood and the gas
  called (2) moving in the opposite direction. The
  diameter of an alveolus is (3) and it is
  surrounded by squamous epithelial cells that are
  only (4) thick and so allow rapid (5) of gases
  across them.

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Gaseous exchange in the alveoli (2)

• Each alveolus is surrounded by a network of (6)
  that are around (7) in diameter, causing (8)
  within them to be flattened against their
  surface, thus improving the rate of exchange of
  gases between themselves and the alveoli.

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Learning Outcomes

• explain the meanings of the terms tidal volume
  and vital capacity
• describe how a spirometer can be used to measure
  vital capacity, tidal volume, breathing rate and
  oxygen uptake
• analyse and interpret data from a spirometer

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Breathing Rate

• Breathing refreshes the air in the alveoli so
  that concentration of O2 and CO2 remains constant

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Lung Capacities

• Tidal volume
• The volume of air breathed in or out in a single
  breath
• Residual volume
• The amount of air that remains in the alveoli and
  airways after forced exhalation.
• Vital Capacity
• The volume of air that can be exchanged between
  maximum inspiration and maximum expiration

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• The effect of exercise on breathing is measured
  by calculating ventilation rate, which is the
  total air moved into the lungs in one minute.
• Ventilation rate tidal volume X breathing rate
• Ventilation brings about changes in lung volume,
  these changes can be ,measured by a spirometer.

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Measuring Oxygen Uptake

• If someone breathes in and out of a spirometer
  for a period of time, the carbon dioxide level
  increases to dangerous levels.
• To avoid this, soda lime is used to absorb the
  carbon dioxide exhaled.
• This means the total volume of gas in the
  spirometer will go down.

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Measuring Oxygen Uptake

• The volume of CO2 breathed out is the same as the
  volume of O2 breathed in.
• This allows us to make calculations of oxygen
  used under different conditions.

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Spirometer trace (4 marks)

• A spirometer measures the volume of gas breathed
  in and out of the lungs.
• The spirometer trace shows the results obtained
  from a 17 year old male who was sitting down
  while breathing in and out of a spirometer.
• Describe this persons breathing between points J
  and K on the spirometer trace

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Spirometer trace answers
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Transport

• Unit One
• Cells, Exchange and Transport
• AS Biology
• OCR Specification

57
Learning Outcomes

• Explain the need for transport systems in
  multi-cellular animals in terms of size, activity
  and surface area to volume ratio
• Explain the meaning of the terms single and
  double circulatory systems with reference to the
  circulatory systems of fish and mammals
• explain the meaning of the terms open circulatory
  system and closed circulatory system, with
  reference to the circulatory systems of insects
  and fish

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The Mammalian Transport System

• Why do multi-cellular animals require a transport
  System?

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The Internal Transport System

• Cell Metabolism What do cells need?
• Amino acids, glucose, oxygen
• Removal of waste products
• What is important in determining whether an
  organism has a transport system?
• Size
• Surface area to volume ratio
• Level of activity

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Pupil Activity

• Using the table on the next slide, determine the
  importance of the three factors and give
  information to support your answers?
• Size
• Surface area to volume ratio
• Level of activity

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Different Transport Systems
Type of organism Size range Example Level of Activity Type of transport system
Single celled Microscopic Paramecium Move in search of food No special transport sys.
Cnidarians Microscopic ? 60cm Sea Anemone Slow swim or sedentary No special transport sys.
Insects 1mm ? 13cm Locust Move actively (fly) Blood system with pump
Fish 12mm ? 10m Goldfish Move actively Blood system with pump
Mammals 35mm ? 34m Human Move actively Blood system with pump.
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Determining the need for a transport system!
Size Important, but not the only factor Small mammals and insects have a transport system Large cnidarians no transport system


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Determining the need for a transport system!
Size Important, but not the only factor Small mammals and insects have a transport system Large cnidarians no transport system
Surface area to volume ratio Small organisms have a large S.A to volume ratio, and have no transport system

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Determining the need for a transport system!
Size Important, but not the only factor Small mammals and insects have a transport system Large cnidarians no transport system
Surface area to volume ratio Small organisms have a large S.A to volume ratio, and have no transport system
Level of Activity Fish, mammals and insects more active have a transport system Larger but sedentary cnidarians do not
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Why transport systems?

• Diffusion only works effectively in large surface
  area to volume ratios
• Small organisms. Oxygen diffuses into cells, to
  mitochondria for use in respiration
• Large organisms can not rely on this
• Body surface is not large enough
• Distances from surface are too great
• Less active organisms have a smaller requirement
  for glucose and oxygen.

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Surface AreaVolume ratios
Length of side (mm) Volume (mm3) Surface area (mm2) Surface areavolume ratio
1
5
10
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Surface AreaVolume ratios
Length of side (mm) Volume (mm3) Surface area (mm2) Surface areavolume ratio
1 1 6 6 1
5 125 150 1.2 1
10 1000 600 0.6 1
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Surface area volume ratio

• With a cube shape
• As it gets bigger the volume increases faster
  than the surface area
• Larger multi-cellular animals need a transport
  system and special gas exchange surfaces

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Open Circulation

• Insects have an open circulation
• Blood is not enclosed in vessels, and it
  circulates in body spaces.

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Closed circulation

• Blood flows inside vessels
• Single circulation e.g. Fish
• Blood flows through heart once in every
  circulation of the body.

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Closed Circulation

• Double Circulation e.g. mammals
• Blood passes through the heart twice in every
  circulation of the body.
• Two circuits
• Pulmonary circuit
• Systemic circuit

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Advantages of a double circulation

• Simultaneous high pressure delivery of oxygenated
  blood to all regions of the body
• Oxygenated blood reaches respiring cells
  undiluted by deoxygenated blood.

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The Mammalian Heart

• Structure of the Heart
• Dissection

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Learning Outcomes

• describe, with the aid of diagrams and
  photographs, the external and internal structure
  of the mammalian heart
• explain, with the aid of diagrams, the
  differences in the thickness of the walls of the
  different chambers of the heart in terms of their
  functions

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External Structure of the heart

• Observe and draw the external structure of the
  heart, identifying the following parts.
• Cardiac muscle
• coronary arteries
• Aorta
• pulmonary artery
• Vena cava
• pulmonary vein

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Internal structure of the heart

• Observe and draw the internal structure of the
  heart
• Identify and describe
• Septum
• atrium and ventricle
• Atrio-ventricular valves
• mitral/bicuspid
• tricuspid

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Revision of structure of heart

• Label the diagram of the heart
• Right atria / left atria
• Right ventricle / left ventricle
• Aorta / pulmonary artery
• Vena cava / pulmonary vein
• Colour in deoxygenated blood blue / oxygenated
  blood red
• Fill in the missing gaps in the summary.
• You have got 10 minutes for this activity

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The Mammalian Heart

• The Cardiac Cycle

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Learning outcomes

• describe the cardiac cycle, with reference to the
  action of the valves in the heart

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Cardiac Cycle

• The sequence of events of a heart beat
• Alternate contractions (systole) and relaxations
  (diastole)
• Between 70 and 75 bpm

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Cardiac Cycle

• Blood flows through the heart
• Muscles contract
• Volume chamber decreases
• Pressure increases
• Blood forced to a region of lower pressure
• Valves prevent backflow

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Cardiac Cycle

• There are 3 main stages to the cardiac cycle
• Atrial systole
• Ventricular systole
• Diastole

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Atrial Systole

• Heart is full of blood and ventricles relaxed
• Both atria contract
• Blood passes into ventricles
• A-V valves open due to pressure
• 70 blood flows passively atria - ventricle

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Atrial Systole
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Ventricular Systole

• Atria relax
• Ventricles contract
• Forces blood into pulmonary artery and aorta
• A-V valves close (lub)
• S-L valves open
• Pulse is generated

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Ventricular systole
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Diastole

• Ventricles relax
• Pressure in ventricle lt pressure in arteries
• High pressure blood in arteries cause S-L valves
  to shut (dub)
• All muscles relax
• Blood from vena cava and pulmonary vein enter
  atria

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Diastole
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Structure and function of heart muscle

• Ventricle walls are thicker
• Need greater force when contract
• R. Ventricle force relatively small, pumps to
  lungs
• L. Ventricle sufficient to push blood around
  body
• Thickness left gt right

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Exam Question

• Answer the exam question
• You have got 15 minutes for this

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Pressure and volume changes of the heart
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Pupil Activity

• June 2003 2803/1 question 2

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Learning outcomes

• Describe how heart action is coordinated with
  reference to the sinoatrial node (SAN), the
  atrioventricular node (AVN) and the Purkyne
  tissue.
• Interpret and explain electrocardiogram (ECG)
  traces, with reference to normal and abnormal
  heart activity.

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Control of Heart Beat

• Myogenic heart muscle contracts and relaxes
  without having to receive impulses from the
  nervous system
• Sino-atrial node
• Atrio-ventricular node

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Sino-atrial Node

• Special cardiac muscle tissue in right atrium
• a.k.a. SAN or Pacemaker
• Sets the rhythm at which all other cardiac muscle
  cells beat
• Sends excitation wave (depolarisation) over
  atrial walls

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What happens next?

• Collagen fibres prevent the wave of excitation
  from passing from the atria to the ventricle
  walls
• Allows the ventricle to fill before they contract

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Atrio-ventricular Node

• Patch of conducting fibres in the septum
• a.k.a AVN
• AVN picks up impulses that have passed through
  atrial tissue
• Wave of excitation runs down purkyne tissue to
  the base of the septum

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Atrio-ventricular Node

• Wave spreads upwards and outwards through the
  ventricular walls
• Blood is squeezed up and out through arteries.

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Control of cardiac cycle - Summary

• Cardiac muscles is myogenic
• Wave excitation spreads out from SAN across
  atria, atria contract
• septum prevents wave crossing to ventricles
• Wave excitation passes through AVN, which lies
  between atria
• AVN conveys wave excitation between ventricles
  along specialised muscle fibres known as bundle
  of His
• This conducts wave through septum to base of
  ventricles, bundles branch into smaller fibres
  known as Purkyne tissue
• Wave is released, ventricles contract from apex
  of heart upwards

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electrocardiogram

• Record of wave of electrical activity caused by
  atrial systole (P), ventricular systole (QRS),
  and the start of ventricular diastole (T)

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Translating ECGs

• Elevation of the ST section indicated a heart
  attack
• A small or unclear P wave indicated atrial
  fibrillation
• A deep S wave indicates abnormal ventricular
  hypertrophy (increase in muscle thickness)

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ECG of an unhealthy heart

• An abnormal ECG could indicate
• Arrhythmia
• Where the heart is beating irregularly
• Fibrillation
• Where the heart beat is not co-ordinated
• Myocardial infarction
• Heart attack

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Fibrillation

• Excitation wave is chaotic
• Small sections of the cardiac muscle contract
  whilst other sections relax
• Heart wall flutter
• Possible causes
• Electrical shock
• Damage to large areas of muscle in walls of heart

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Exam Question

• Answer the practice exam question

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The Mammalian Transport System

• Structure and function of Arteries, Veins and
  Capillaries

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Learning Outcomes

• describe, with the aid of diagrams and
  photographs, the structures and functions of
  arteries, veins and capillaries

108
Structure of Arteries, Veins and Capillaries

• GCSE Revision
• Arteries carry blood away from the heart
• Veins carry blood towards the heart
• Capillaries are a network of thin tubes which
  link A to V, and take blood close to cell.

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Basic Structure
Lumen (hollow centre of tube)

• Tunica externa
• outer layer containing collagen fibres.

• Tunica media
• Middle layer containing smooth muscle and elastic
  fibres

• Tunica intima
• Endothelium (single layer of cells)

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Microscope Artery
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Microscope Vein
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Microscope Capillary
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Blood Vessels
Look at the image on the following page. What are
structures X and Y What do parts 1 4 show or
represent?
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1
X
2
3
Y
4
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Answers

• X is an artery
• Y is a Vein
• shows the smooth endothelial lining cells which
  reduce resistance to blood flow.
• shows red blood cells within the lumen of the
  artery
• shows the thick muscular wall of the artery
• shows blood capillaries note their size compared
  to arteries and veins.

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Structure and Function of Arteries
Look at this cartoon. What can you deduct about
arteries? (answers on a postcard please)
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Structure of Arteries, Veins and Capillaries
Arteries Veins Capillaries
Thick muscular wall Much elastic tissue Small lumen Capable of constriction Not permeable Valves (Aorta and P.A) Thin muscular wall Little elastic tissue Large lumen Not capable constriction Not permeable Valves throughout No muscle No elastic tissue Large lumen (relative) Not capable constriction Permeable No valves
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Arteries

• Function
• To transport blood, swiftly and at high pressure
  to the tissues.
• The structure of the artery wall gives it
  strength and resilience
• The large amounts of elastic tissue in the tunica
  media allow the walls to stretch as blood pulses
  through.
• As arteries move away from the heart there is a
  decrease in elastic tissue and an increase in
  muscle tissue.

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Arteries (cont)

• Elasticity of walls 2 functions
• give
• Blood at low pressure in an artery gets a push
  as artery recoils ? evens out blood flow
• Arterioles
• More smooth muscle
• Contracts to help control the volume of blood
  flowing into tissues (dilation and constriction)

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Capillaries

• Function
• To take blood as close as possible to all cells,
  allowing rapid transfer of substances between
  cells and blood
• Network of capillaries ? capillary bed

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Veins

• Venules/veins
• Return blood to the heart
• Low venous pressure
• Semi-lunar valves
• Form from endothelium
• Allow blood to travel to the heart
• Prevents the back flow of blood

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Systemic Circulation

• Aorta
• ? artery
• ? arteriole
• ? capillary
• ? venule
• ? vein
• ? vena cava

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Summary of function of A, V and C
Arteries Veins Capillaries
Transports blood away from heart Oxygenated blood (except P.A) Blood High Pressure Blood moves in pulses Blood flow rapidly Transport blood too heart. Deoxygenated blood (except P.V) Blood low pressure No pulses Blood flows slowly Links arteries to veins Blood changes from oxygenated to deoxygenated (except in lungs) B.P. reducing No pulses Blood flow slowing
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Revision Questions (1)

• Suggest why arteries close to the heart have more
  elastic fibres in walls than arteries further
  away from the heart.
• Suggest why there are no blood capillaries in the
  cornea of the eye. How might the cornea be
  supplied with its requirements?

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Revision Questions (2)

• Suggest reasons for the following
• Normal venous pressure in the feet is about 25mm
  Hg. When a soldier stands at attention the blood
  pressure in their feet rises very quickly to
  about 90mm Hg.
• When you breathe in (volume thorax increases),
  blood moves through the veins towards the heart.

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Pupil Activity

• Bioviewer activity slide set 68
• Read the information on the front of the card.
• how does the human circulatory system help to
  maintain cell life?
• what are the three major parts of the human
  circulatory system?
• Observe the following slides
• Slide 1 human blood
• Slide 2 Phagocyte
• Slide 3 artery and vein
• Slide 4 capillaries in the lung

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Blood, Tissue fluid and Lymph
128
Blood the transport medium

• Plasma
• Straw coloured, alkaline liquid
• Consists mainly of water
• Functions of blood
• Defends body against disease
• Maintains diffusion gradients
• Acts as a buffer
• Provides pressure
• Distributes heat around body

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Blood plasma

• Water with dissolved substances
• Nutrients e.g. glucose
• Waste products e.g. urea
• Plasma proteins
• Buffers
• Solute potential

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Red Blood CellsErythrocytes

• Origin
• Bone marrow
• Mature RBC transport respiratory gases
• Life span 120 days
• No nucleus/ cell organelles
• Cytoplasm full of haemoglobin
• Biconcave disc
• Large SA volume ratio

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White Blood CellsLeucocytes

• Protect body as part of the immune system
• Originate in bone marrow ?thymus and lymph for
  growth and development
• Lymphocytes
• Production of antibodies
• neutrophils, monocytes
• phagocytosis

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Platelets(cell fragments)

• Tiny packages cytoplasm containing vesicles with
  thromboplastins
• Clotting factors
• Made in bone marrow
• Last 6 7 days

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Pupil Activity

• Which of these functions could, or could not, be
  carried out by a RBC.
• Protein synthesis
• Cell division
• Lipid synthesis
• Active transport

134
Answers SAQ

• Protein Synthesis
• NO no DNA so no mRNA can be transcribed.
• Cell Division
• NO no chromosomes, so no mitosis no centrioles
  for spindle formation

• Lipid Synthesis
• NO occurs in smooth ER
• Active Transport
• YES occurs across plasma membrane, can be
  fuelled by ATP from anaerobic respiration.

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Tissue Fluid

• Immediate environment of each individual body
  cell.
• Homeostasis maintains composition of tissue fluid
  at a constant level to provide the optimum
  environment in which cells can work.
• Contains less proteins than Blood plasma

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Forces for exchange on capillaries
Blood proteins (e.g. albumins) can not escape and
maintain the water potential of the plasma,
preventing excess water loss, and help to return
fluid to the capillary
Arteriole end
Venule end
Blood in capillary
Diffusion gradient
Diffusion gradient
Osmotic movement of water
Ultrafiltration of water and small molecules (O2,
glucose and amino acids) due to hydrostatic
pressure
Hydrostatic pressure reduced
Tissue fluid
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Lymph

• Similar composition to plasma with less proteins
• Lipids absorbed in lacteals, give lymph milky
  appearance
• Tiny blind ending vessels
• Tiny valves in walls allow large molecules to
  pass in.
• Drains back into blood plasma in subclavian vein.

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oedema

• If lymph does not take away proteins in tissue
  fluid between cells, YOU could die in 24 hours.
• Get a build up in tissue fluid, called oedema.

139
Movement in lymph capillaries

• Contraction of muscles around vessels
• Valves
• Slow movement
• Diagram the relationship between blood, tissue
  fluid and lymph at a capillary network
• Diagram the lymph system

140
Table summary
feature blood Tissue fluid Lymph
Cells
Proteins
Fats
Glucose
Amino acids
Oxygen
Carbon dioxide
Antibodies
141
Table summary
feature blood Tissue fluid Lymph
Cells Erythrocytes, leucocytes, platelets phagocytes Lymphocytes
Proteins Hormones and plasma proteins hormones, proteins secreted by body cells some
Fats Transported as lipoproteins None Absorbed by lacteals
Glucose 80-120mg per 100cm3 Less Less
Amino acids more less less
142
Table summary
feature blood Tissue fluid Lymph
Oxygen more less Less
Carbon dioxide little Released by body cells More
Antibodies yes yes yes
143
The Mammalian Transport System

• Transport of Oxygen and Carbon Dioxide

144
Partial Pressure

• In a mixture of gases, each component gas exerts
  a pressure that is proportional to how much of it
  is present.
• Concentration of gas is quoted as its partial
  pressure, in kilopascals kPa.
• pO2 ? partial pressure of oxygen
• pCO2 ? partial pressure of carbon dioxide
• pO2 atmospheric pressure x O2
• 100

145
Pupil Activitycalculation of partial pressure

• Assume the composition of air is 20 oxygen and
  80 nitrogen, and is approx. the same at sea
  level (atmospheric pressure 101.3kPa) and at
  5000m above sea level (atmos. Pressure 54.0
  kPa) and at 10000m above sea level (atmos.
  Pressure 26.4 kPa)
• What is the partial pressure of oxygen at these
  altitudes?

146
Transport of Oxygen

• Haemoglobin in red blood cells (RBC)
• Hb 4O2 HbO8

147
Haemoglobin dissociation curve

• A graph showing the amount of oxygen combining
  with haemoglobin at different partial pressures.
• High pO2 haemoglobin saturated with oxygen
• Low pO2 oxyhaemoglobin gives up its oxygen to
  respiring cells (dissociates)

148
Haemoglobin dissociation curve
149
S-shaped curve

• Each Hb molecule has 4 haem groups
• 1st O2 combines with first haem group
• Shape of Hb distorted
• Easier for other 3 O2 to bind with haem group

150
Bohr Shift

• high pCO2 increases dissociation of
  oxyhaemoglobin
• Oxyhaemoglobin releases oxygen where it is needed
  most actively respiring tissues.

151
Fetal Haemoglobin

• Fetal Hb has a higher affinity for O2 than adult
  Hb.
• This allows the fetal Hb to steal O2 from
  mothers Hb

152
Myoglobin

• Oxymyoglobin is more stable than oxyhaemoglobin
• Only gives up O2 at very low pO2.
• Myoglobin acts as an oxygen store

153
Carbon Dioxide Transport

• CO2 carried in three ways
• 5 in solution in plasma as CO2
• 10 combines with amino groups in Hb molecule
  (carbamino haemoglobin)
• 85 hydrogen carbonate ions

154
Carbon dioxide transport

• Transported in blood as hydrogen carbonate ions
• Carbonic anhydrase catalyses the reaction
• CO2 H2O ? H2CO3

155
Carbon Dioxide Transport

• Carbonic acid dissociates
• H2CO3 ? H HCO3-
• H ions associate with haemoglobin (buffer)
• Haemoglobinic acid (HHb)
• Contributes to Bohr effect

156
Chloride Shift

• Build up HCO3- causes them to diffuse out of RBC
• Inside membrane positively charged
• Cl- diffuse into RBC from plasma to balance the
  electrical charge

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158
Problems with Oxygen Transport
159
Carbon Monoxide

• Haemoglobin combines readily with carbon monoxide
  to form carboxyhaemoglobin (stable compound)
• Carbon monoxide has a higher affinity with
  haemoglobin than oxygen does
• 0.1 CO in air can cause death by asphyxiation.

160
High Altitude

• Pupil activity
• question sheet on high altitude
• Question
• Atheletes often prepare themselves for important
  competitions by spending several months training
  at high altitude. Explain how this could improve
  their performance.

161
Training at high altitude

• Spending a length of time at high altitude
  stimulates the body to produce more red blood
  cells
• When an athlete returns to sea level, these
  extra RBC remain in the body for sometime, and
  can supply extra oxygen to muscles enabling them
  to work harder and for longer than they would
  otherwise.