Antrim PE Revision CourseAQA AS PHED 1

Session 3bApplied Physiology – Respiration

& Cardiac Function

Respiration – need to know

• Mechanics of breathing• Different lung volumes and capacities• Interpret spirometer graphs• Oxygen and carbon dioxide exchange in lung

alveoli and muscles• Process of diffusion• Concept of partial pressure

Cardiac function – need to know

• Circulatory system• Role of haemoglobin, myoglobin• Venous return• The a-vO2 difference• Heart structure – cardiac cycle• Cardiac output, stroke volume, heart rate• Control of heart rate• Effects of training

Breathing

Quiet breathing – diaphragm+ intercostals

Deep breathing – sternocleidomastoid + pectorals

Medulla OblongataRespiratory

Accelerator Centre

Respiratory Inhibitory

Centre

Chemo-receptors

CO2

Inflation of aleveoli

Sympathetic

(Acc nerve)

Parasympathetic

Vagus nerve

Autonomic breathing

control

Lungs

Intercostal muscles

Diaphragm Contract

Respiration – Lung Volumes

June02Q3 Ans

Respiration - VentilationVentilation = Tidal Volume x Frequency (breathing rate)

Frequency/Breathing rate:Resting 12-18 min-1 Peak: 45-60 min-1

Tidal volume: Resting 0.5L Peak: 2.25 L

Minute VentilationResting: 6 lt/min-1 Peak:175 lt/min-1

Respiration - O2 TransportRed Blood Cells

Haemoglobin > Oxyhaemoglobin

From alveoli – to muscle cell boundary

Myoglobin > Oxymyoglobin

From muscle cell boundary > mitochondria

A-V difference

Carbon dioxide

70-80% Bicarbonate carbonic acid HCO35-10% Dissolved in plasma5-10% Carbaminohaemoglobin

 

Arterial BloodO2%

Venous Blood

O2%

a-VO2

DiffO2%

More oxygen is extracted by working muscles

Rest 20 15 5

Intense Exercise

20 5 15

Arterial – Venous Oxygen Difference (a-VO2 diff)

Jun02Q5 Ans

PCO2 45mm Hg

PCO2 40mm Hg

PCO2 40mm Hg

PO2 40mm Hg

PO2 104mm Hg

PO2 104mm Hg

O2 CO2

Blood Flow in Capillary

Capillary

Alveolus

Gas

Exchange

Exercise and oxygen disassociation

Bohr Shift

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

pO2 (mm Hg)

% s

atu

ratio

n H

amo

glo

bin

Rest

Rise in temperature

Acidity rise due to CO2 LA

increase

Curve moves to the right

Bohr Shift

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

pO2 mm Hg

% S

atu

ratio

n o

f Hae

mo

glo

bin

Rest

Exercise

More O2 available during exercise

Haemoglobin disassociates oxygen

more readily

Jun02Q5

Ans

Pulmonary and systematic circulation • Arteries/arterioles/capillaries/venules and veins)• Generation of blood pressures/velocities• Venous return mechanism• Redistribution of blood/vascular shunting• Arterio – venous oxygen difference (A-VO2 diff).• Cardiac function• Cardiac cycle• Cardiac output, stroke volume and heart rate and the relationship

between them.• Heart rate range in response to exercise; hormonal and nervous

effects on heart rate;• Role of blood carbon dioxide in changing heart rate• Cardiac hypertrophy leading to bradycardia/athlete’s heart• Starling’s law of the heart• Cardio-vascular drift.

Blood vessels

Arteries - thick muscular walls; take blood away from heart - high pressure; elastic

Capillaries - tiny, very thin

walls - diffusion of substances in

and out

Veins - thin walled; carry blood back to heart - need

help - venous return

Invisible on this scale

Arte

riole

s

Venu

les

06-19 14

Venous return• One-way valves in veins• Contraction of skeletal muscles during

movements – skeletal pump• Compression of chest veins during inspiration,

and lowering of thoracic pressure – respiratory pump

• ‘Suction pressure’ of heart

Dynamics of venous returnMuscle pump

Respiratory pump

Blood pressure and velocity

Total cross-sectional area

Arteries VeinsVenulesCapillariesArteriolesBlood pressure

Pressure falls - friction & increasing cross-sectional area

Blood velocity

Velocity falls and rises – with increasing & decreasing total cross-sectional area

Jun04Q5 Ans

Starlings Law

Venous return

SV

Normal contractility

Trained Heart

Increased venous return

Increased filling of left ventricleIncrease in fibre length Increase in contractilityIncreased stroke volume

Trained heart will contract more powerfully

Left ventricle

Blood Flow - Redistribution

Rest

Max Exercise

AreaArea RestRest MaxMax

MusclesMuscles 10001000 2600026000

HeartHeart 250250 12001200

SkinSkin 500500 750750

KidneysKidneys 10001000 300300

Liver & Liver & GutGut

12501250 375375

BrainBrain 750750 750750

WholeWhole 50005000 3000030000

Blood Flow in cm3 per minute

Liver & Gut

Liver & Gut

Jan04Q1Ans

Blood Flow Redistribution - Volume

AreaArea RestRest Max ExMax Ex

MusclesMuscles 10001000 2600026000

HeartHeart 250250 12001200

SkinSkin 500500 750750

KidneysKidneys 10001000 300300

Liver & Liver & GutGut

12501250 375375

BrainBrain 750750 750750

WholeWhole 50005000 3000030000

Blood Flow in cm3 per minute

Increase in total blood flow (Cardiac Output)

SV+ HR+

Increase to skeletal muscles & heart

Decrease to liver, gut, kidneys

Brain stays same

Cardiac cycle Contraction =

systole

Relaxation = diastole

Atrial systole

Diastole

Ventricular systole

The order of contraction

Valves close when pressure drops again (diastole)

High pressure (systole) in chambers forces valves open

Cardiac OutputCardiac Output = Heart Rate x Stroke Volume

Q. = HR X SV

Stroke Volume - Volume of blood ejected each contraction (systole) of the ventricle

Rest 60bpm x 83ml = 5000ml-1 (5 litres)

Max work (trained) 200bpm x 170ml = 34000ml-1(34 litres)

Units!

Cardiac Hypertrophy• Increase in heart size due to training• Specifically left ventricle• Thickening of heart muscle• Leads to bradycardia – resting heart rate <60

Cardio-Vascular Drift• Decreasing venous return• Decrease in stroke volume• Heart rate increases

Heart Rate Control

Adrenaline

Conduction of nerve impulses gets

quicker

Increase in blood pressure

Increased levels of carbon

dioxide, lactic acid

Medulla OblongataCardiac

Accelerator CentreCardiac

Inhibitory Centre

Chemo-receptors

CO2 H+

Baro-receptors

Blood pressure

Sympathetic

(Acc nerve)

Parasympathetic

Vagus nerve

Vaso-motor

Centre

Vaso-constriction or dilation

Movement

Muscle action

Heart Rate ControlJan07Q5 Ans