Biology Unit 5: Principles and Application of Science

  • Created by: stesar
  • Created on: 23-11-17 11:16

The Heart - Right Side

Right Side of the Heart

  • Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart.
  • As the atrium contracts, blood flow from the right atrium into the right ventricle through the open tricuspid valve.
  • When the ventricle is full, the tricuspid valve shuts. This prevents blood from flowing backwards into the atria while the ventricle contracts.
  • As the ventricles contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.
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The Heart - Left Side

Left Side of the Heart

  • The pulmonary vein empties oxygen-rich blood from the lungs into the left atrium of the heart.
  • As the atrium contracts, blood flow from the left atrium into the left ventricle through the open mitral valve.
  • When the ventricle is full, the mitral valve shuts. This prevents backflow of blood into the atria while the ventricles contract.
  • As the ventricles contracts, blood leaves the heart through the aortic valve, into the aorta and to the body.
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The Heart Muscles

The heart muscles are myogenic, they contract spontaneously, without being stimulated by nerve cells. 

Tendinous cords make sure the valves are not turned inside out by the pressure exerted.

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Cardiac Output

Cardiac output - CO = HR x SV

CO - the amount of blood pumped by each vesicle in 1 min.

HR - Heart Rate = number of contractions in one minute.

SV - Stroke Volume = amount of blood ejected from each vesicle within each contraction.

Average - 4000ml - 5000ml = 70 x 70 

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Carry oxygenated blood away from the heart at high pressure


Thick, muscular walls control the volume of blood. Also stopping the vessels bursting under the pressure

Lots of elastic tissue in the walls, which stretch and recoil to maintain high pressure

Small lumen so blood is under high pressure

No valves, so blood is under high pressure so doesn't flow backwards

Branch into arterioles

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Link arterioles to ventricles


Walls made up of one cell thick endothelium for rapid diffusion

Numerous and highly branched for big surface area for diffusion

Very small lumen so reduced diffusion distance 

Space between linings can escape dealing with infection

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Carry blood at low pressure back to the heart


Thin muscular walls

Little elastic tissue in the wall - low pressure will not cause them to burst

Relatively large lumen

Low-pressure valves prevent backflow of blood

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Blood Transfusion and ABO Rhesus System

Red blood cells have antigens on either A or B

  • Antigen A - blood contains B antibodies
  • Antigen B - blood contains A antibodies

The RH Factor 

A person with the Rh factor on their red blood cells

  • Rh positive (Rh+)
  • Not make Rh antibodies

A person without the Rh factor on their red blood cells

  • Rh negative (Rh-)
  • Will produce Rh antibodies

Rh+ person can receive both Rh+ and Rh- transfusion but Rh- can only receive Rh-

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Systole and Diastole

Systole - contraction in a single heart-beat, two waves of contraction

Diastole - relaxation

  • The heart is relaxed
  • Blood from the vena cava and pulmonary veins enter the atria
  • Atrioventricular valves are slightly open 
  • Semi-lunar valves are closed
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Control of Heart Rate

1) All the electrical impulses start in the pace-maker cell in the sino-atrial node - atria contracts

2) These impulses travel to the atrioventricular node and then after a slight delay* to the bundle of His

3) The electrical impulse travels to the Purkinje fibres at the apex of the heart, and the heart controls the apex upwards.

*Between the ventricle and the atria, there is an insulating layer which doesn't allow message to pass through

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Structure and Function of the Heart

Vena Cava - brings the blood to the right side of the heart from the rest of the body

Atria - thin muscular walls, slight pressure builds up

Atrioventricular valve - opens to let blood pass into the right ventricle

Right Ventricle - contracts to prevent any backflow of blood

Tendinous cords - make sure the valves are not turned inside out by the pressure exerted

Pulmonary Vein - transports it to the capillary bed in the lungs

Left atrium - oxygenated blood from the lungs enter the pulmonary vein from the left atrium, pressure then builds up

Bicuspid Valve - opens between the left atrium and the left ventricle

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The Cardiac Cycle and ECGs

Diastole - the heart is relaxed

Atrial Systole - The atria are full of blood and the ventricles are relaxed. Both atria contract and force the atrioventricular valves to open due to the pressure. Blood goes into the ventricles.

Ventricular Systole - The atria relax. The ventricle walls contract. The atrioventricular valves shut to prevent backflow. The semi-lunar valves open. Blood passes through the aorta and pulmonary arteries.

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The Cardiac Cycle and ECGs

Tachycardia - heartbeat is very fast (over 100bpm) - P waves are closer together

Bradycardia - contraction of the ventricles is not controlled - little/ no blood pumped - no identifiable P, Q, R, S or T waves, heart rate is very fast

Ventricular Fibrillation - normal heart rate cycles with breathing - normal P wave but not spread evenly 

Flat Line - no electrical activity - flatline

ECGs monitor the electrical activity of the heart through sensors on the skin

P - excitation of atria - electrical message from SAN

QRS - excitation of ventricles when they begin to contract 

T - heart chambers are relaxing 

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The Respiratory System

Trachea and Bronchi

  • Rings of cartilage to keep from collapse 
  • Surfactant also prevent the lungs from collapsing
  • Goblet cells secrete mucus
  • Mucus is sticky to 'collect' dust, dirt, pathogens
  • Cilia - beat a layer of mucus out of trachea
  • Elastic fibres recoil and reopen airways
  • Smooth muscle contract and restrict airways - asthma is an over-reaction of this.


  • Smooth muscles and elastic fibres
  • Don't have cartilage
  • Smooth muscle to adjust size of bronchioles
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The Respiratory System


  • Site of gaseous exchange and massive surface area
  • Thin for rapid diffusion, moist for diffusion, surrounded by blood vessels to carry oxygen maintain steep gradient. 
  • Capillaries - 1 cell thick
  • Large surface area

Capillary Network

  • Surrounds alveoli
  • 1 cell thick to ensure short diffusion distance 
  • Circulation removes oxygen and return CO2 to maintain diffusion gradient 
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Electrical Impulse Sequence

SAN sends out an electrical impulse

Upper heart chambers (atria) contract

AVN send impulse into ventricles

Lower heart chambers (ventricle) contract or pump

SAN sends another signal to atria to contract

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The Lungs and Gas Exchange

Intercoastal Muscles - move ribcage (external) contraction which allows chest expansion for breathing

Diaphragm - dome-shaped sheet of muscle

(Inspiration -expand/ contract)
(Expiration - falls/ flattens)

Pleural membrane - link outer and inner wall of thorax -

  • contain a small amount of pleural fluid
  • Allows the surface of the lungs to glide
  • Pleural fluid lubricates and prevents friction between the lungs and inner thorax walls.
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The Spirometer

How to use:

  • Ensure the subject is sat down
  • Sterilise mouthpiece
  • Place mouthpiece in mouth and clip nose
  • Ask subject to breathe as deeply as possible, and force out air as deeply as possible
  • Resume normal breathing

Uses and issues

  • If someone breathes in & out for a period of time, the CO2 levels increases to dangerous levels
  • To avoid this, soda lime is used to absorb the CO2 exhaled
  • This means that the total volume of gas in spirometer will go down
  • The volume of CO2 breathed out = same as volume of CO2 breathed in
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Measuring Lung Capacity

Tidal Volume - volume of air breathed in or out in a single breath (0.5dm3 left)

Residual Volume - the volume of air that remains in the alveoli and airways after forced exhalation (1.5dm3 left)

Vital Capacity - total volume from fully breathed in to fully breathed out (5dm3 left)

Inspiratory Reserve Volume - maximum amount you breathe in and out (2.5-3dm3 left)

Expiratory Reserve Volume - same as above (1dm3 left)

Total Lung Capacity - vital capacity + residual volume

Breathing rate = breathing refreshes the air in the alveoli so that the concentration of CO2 and O2 remains constant

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Urinary System

Substances such as water, urea, uric acid, glucose and amino acids all have the same concentration from being in the blood plasma going in the glomerular filtrate (e.g uric acid = blood plasma = 0.04g dm3 = 0.04gm3 = glomerulus filtrate).

However, proteins are too large of a substance to fit through the filter, therefore the concentration in blood plasma 80gdm3 to 0.05gm3 in glomerulus filtrate.

Blood leaving the glomerulus has a very low water potential. Selective reabsorption (in proximal convoluted tubule) from the filtrate in tubule back into blood capillaries.

All glucose, amino acids, vitamins and may sodium and chlorine ions are reabsorbed out of the proximal convoluted tubule and back into the blood.

The walls of the nephron are made up of cuboidal epithelium with microvilli which give a large surface area.

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Kidney Function and Structure

Controls the water, ion, pH levels and maintains the composition of the blood.

Kidney's produce urine in a two-stage process:

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Podocytes (cells of the Bowman's Capsule)

  • Each cell has many foot-like extensions projecting from the surface.
  • Extensions wrap around the capillaries of the glomerulus and interlink with the extensions from neighbouring cells.
  • These fit together loosely leaving filtration slits (about 25mm wide)
  • The filtration fluid passes through the filtration slits.

Image result for urinary system

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Nephron - inside a kidney

Image result for nephron

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The Loop of Henle

Water Absorption

Descending limb descends into the medulla
Ascending limb ascends into the cortex

This arrangement allows salts to be transferred.

The overall job is to create a high concentration of sodium ions and chloride ions in the tubule fluid.

These diffuse out into the tissue fluid in the medulla which lowers the water potential so water is reabsorbed from the contents of the nephron as they pass through the collecting duct.

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The control of water content of the blood and tissue fluid - controlled by the hypothalamus.

Osmoregulation in the hypothalamus is sensitive to the water potential in the blood. Produce ADH from the neurosecretory cells.

ADH passes along their axons to the posterior pituitary gland where it is secreted directly in the blood. It then travels in the blood to the kidney. 

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Increases the permeability of the cell membranes of the collecting duct cells to water.

More Water is reabsorbed and less lost as urine.

Where is ADH produced? hypothalamus

Where is ADH secreted into the blood? How does it get to this gland?

ADH passes along axons to the posterior pituitary gland where it is secreted directly into the blood.

What effect does it have on the kidney?

It increases its permeability of the cell membranes of the collecting ducts to water.

What is the urine like if there are low levels of ADH in the blood? 

Lots of urine, but will be quite dilute

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Process from the Collecting Duct to Blood Vessels

1) Osmoreceptors detect low water content of body fluids

2) ADH produced, secreted into capillaries of post pituitary gland

3) Presence of ADH detected by receptors in membrane of the collecting duct

4) Vesicles containing water-permeable channels move and fuse with membrane of the cell

5) Water diffuses down water potential gradient out of collecting duct

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you mean ventricle when you say vesicle

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