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SPM Notes on Chapter Respiration

Jun 02, 2018

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    STRUCTURE OF

    HUMAN LUNG1. Respiratory system of man:

    - consists of trachea, lungs, bronchus,

    bronchioleand air sacs ( or alveolus )

    - structure of trachea is supported by

    cartilage tissue( ring shaped ,

    preventing it from collapse when there

    is a change in air pressure inside I

    - bronchioles end up at numerous tiny air

    sacs, the alveoli. Alveolus has a wet

    and thin / single layer of squamousepithelial cellsthrough which gaseous

    exchange takes place.

    - alveolus is well provided with a network

    of blood capillaries. Oxygen diffuses

    out of alveolar air into blood capillaries,

    combines with haemoglobin in the red

    blood cells to form oxyhaemoglobin .

    Oxygen is transported to body tisues in

    the form of oxyhaemoglobin.

    2. Both lungs ( and the heart ) are situated

    and enclosed in the thoracic cavityby

    ribs, intercostal muscles and the

    diaphragm.

    3. The contraction of external and internal

    intercostal muscles bring about the

    inhalation and exhalationof air during

    breathing.

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    RESPIRATION Dur ing inhalat ion:

    -External intercostal muscle

    contracts, internal intercostal

    muscle relaxes ( both are

    antagonistic muscles) results

    in the raising up of the ribs

    -Diaphragm also contractscuausing it to move

    downward and becomes less

    curved

    -The capacity ( volume ) of

    thoracic cavity increases and

    the air pressure iside it is

    lower than in the atmosphere.

    -Air from outside is pushed

    into the lungs.

    -The revers process occures

    during exhalation.

    Haemoglobin molecule is

    made up of 2 alpha- and

    two beta- polypeptides. It

    is nearly spherical. Thehydrophobic R-groupsare

    pointing towards the

    centreand the hydriphilic

    ones are pointing

    outwards. Each heme

    group contains Fe+ion.

    Each haemoglobin

    molecule can combine

    with 4 oxygen moleculesto form oxyhaemoglobin.

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    OXYGEN DISSOCIATION CURVE

    The rate at which haemoglobin in saturated withoxygen depends on the partial pressure oxygen

    in the al veolar air, blood and insterstitial fluid in

    body tissue. Haemoglobin takes up more

    oxygen molecules and becomes saturated with

    oxygen faster in the region where partial

    pressure of oxygen is higher. Oxyhaemoglobin

    dissociatesto release oxygen and haemoglobin

    when partial pressure of oxygen is low(and

    higher partial pressure of CO2 )

    An increase in partial pressure of carbon dioxidewilltend to reduce the the rate of oxyhaemoglobin formation,

    and hence the saturation of oxyhaemoglobin with

    oxygen. Therefore the dissociation curveof oxygen will

    move to the rightas more carbon dioxide enters / added

    to the blood. This phenomenon is called the Bohr Effect

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    Oxygen Dissociation Curve and

    Transport of CO2in Blood

    5% CO2 dissolves in blood plasma / part of it forms

    carbonic acid and carried to the lungs. 10

    20% is carriedas carbamino-haemoglobin in the red corpuscles. Carbon

    dioxide combines with the amino group at one end of the

    haemoglobin polypeptide to form carbaminohaemoglobin.

    HHbNH2 + CO2 HHbNHCOOHHaemoglobin Carbaminohaemoglobin

    In the cytoplasm of red blood cell, CO2is converted into

    H2CO3, catalysed by the enzyme carbonic anhydrase.

    H2CO3 dissociates into H+ and HCO3-. HCO3 diffuses outinto blood plasma and carried to the lungs ( about 80%)

    Chlor ide shi f t

    diffusion of Cl-

    (chloride) ions into

    red blood cell to

    balance the

    elecktric charges inthe cell.

    +

    Oxygen dissociation curves for adult

    and foetal haemoglobin.

    Oxygen dissociation curves for mioglobin and adult andfoetal haemoglobin compared.

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    CONTROLL OF BREATHING

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    Oxygen and Carbon Dioxide Transport

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    Transport of CO2and O2 In Blood

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    CONTROLL OF BREATHING

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    Controll of Breathing

    H++ HCO3-

    H2O

    Chemoreceptors

    peripheral and

    central (brain )Inspiratory

    centre , ventral

    part of medulla

    oblongata

    Expiratory c entre-

    dors al and lateral part

    of m edul la oblongata

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    Controll of Breathing

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    MEASURING LUNG CAPACITY

    Kymograph

    counterpoise

    Carbon dioxide

    absorber

    Water level

    The capacity of human lungs measured by spiromter.

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    Lung Capacity During Breathing

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    Lung Capacity

    1. Tidal volume (0.45 lit.)

    volume of air breathed in and

    out at rest.

    2. Inspiratory reserve volume

    (1.5 lit. )- extra volume of air

    taken in after normal

    inhalation

    3. Expiratory reserve volume

    (1.5 lit.)- volume of air that

    can be further breathed out

    after normal exhalation.

    4. Vital capacity (4.5 lit.)-

    volume of air breathed out

    after a forced inspiration, and

    then followed by forced

    expiration. Athlete has higher

    vital capacity.

    5. Residual volume(1.5 lit.)-

    volume of air still left in thelung after a maximal forced

    expiration, including air left in

    the trachea, bronchi and

    bronchioles.

    6. Total lung capacity (5 lit.)-

    maximum volume of air in the

    lung after a forced inhalation

    which is equal to vital

    capacity + residual volume.

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    OPENING AND CLOSING OF STOMATA

    New hypothesis based on accumulation of K+:

    Blue light stimulates the proton pump in the

    membrane of the guard cells, causing fast

    accumulation of H+in the cell.

    This causes an active uptake of K+ ions and thus

    lowering water potential in the guard cells. Water

    diffuses in by osmosis from the surrounding

    epidermal cells. Guard cells become turgid and stoma

    opens.

    The accumulation of positive charges in the cells is

    balanced by Cl-ions or the formation of malate.

    At night , the reverse takes place, K+ ions diffuses

    out, causing water potential in the cell to increase.

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    STOMATA OPENING MECHANISM

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    STOMATA

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    STOMATA OPENING

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    REFLECTION

    1. What is the significance of the following structures in respiration?

    (a) alveolus

    (b) intercostal muscles and diaphragm network of blood capillaries in alveolus

    2. Describe the molecular structure of haemoglobin and how such structure is

    adapted for its function in the transport of oxygen and carbon dioxide in

    blood.

    3. What is Bohr effect ? Describe the importance of the phenomenon in the

    dissociation of oxyhaemoglobin.

    4. Describe briefly , using suitable diagram if necessary, the transport of

    carbon dioxide from tissues to the lungs.

    5. Explain how breathing is regulated during a breathing cycle.

    6. How is the opening and closing of stomata in a leaf influenced by light and

    accumulation of K+ions in guard cells?