1. Chapter 10: Respiration
Respiration is the oxidation of food substances with the release of energy in living cells.
Aerobic respiration is the oxidation of food substances in the presence of oxygen with the release of a
large amount of energy.
Word equation: glucose + oxygen  carbon dioxide + water + energy
Chem equation: C6H12O6 + 6O2  6CO2 + 6H2O + energy
Anaerobic respiration is the breakdown of food substances in the absence of oxygen with the release of a
lot less energy.
In muscle cells,
Word equation: glucose  lactic acid + energy
Chem equation*: C6H12O6  2C3H6O3 + energy
During vigorous muscular contractions during exercise, your muscles first respire aerobically. Panting
may follow to take in more oxygen and remove more carbon dioxide. However due to the limit to the rate
of breathing and heartbeat, the muscles have to respire anaerobically to provide the extra needed energy
to support the muscle contractions. As a result, lactic acid is formed.
Since there is insufficient oxygen to meet the demands of vigorous muscular contractions, the muscles are
said to incur an oxygen debt. When lactic acid concentrations get too high, it causes fatigue and muscular
pains and this forces the person to stop exercise and recover. However during rest, the breathing rate
continues to be high so that sufficient oxygen is absorbed to repay the oxygen debt as well as to oxidise
the lactic acid to produce energy. When the lactic acid is used up, the oxygen debt has been repaid.

2. In yeast,
Word equation: glucose  ethanol + carbon dioxide + energy
Chem equation*: C6H12O6  2C2H5OH + 2CO2
Part Form and function
Air enters the lungs through 2 external nostrils whose walls bear a fringe of hairs and also
lined with a moist mucous membrane. This allows the air breathed in to be: cleaner since dust
Nose and foreign particles are trapped in the hairs and mucus, warmer and moist since the air
passes through the warm nasal passages and safer as harmful chemicals are detected by small
sensory cells in the mucous membrane.
The thinner walls of trachea and bronchi are lined by epithelium bearing cilia. Gland cells in
Trachea the epithelium secrete mucus to trap dust particles and bacteria. Cilia help sweep these
particles up into the pharynx to be swallowed into the oesophagus.
Each lung lies in the pleural cavity, withing which the lungs expands. Two pleural
membranes line each pleural cavity. A thin layer of lubricating fluid between the pleura
Lungs allow membranes to glide over each other easily.
Alveoli are well-supplied with capillaries for efficient gaseous exchange. Thousands of
alveoli are present to increase surface area to volume ratio for rapid diffusion of gases.
Inspiration (inhalation) Expiration (exhalation)
Diaphragm contracts and flattens. Diaphragm relaxes and arches upwards.
External intercostal muscles contract. External intercostal muscles relax.
Internal intercostal muscles relax. Internal intercostal muscles contract.
Ribs move upwards and outwards. Ribs moves downwards and inwards.
Sternum also moves up and forward. Sternum also moves down to original position.
Volume of thoracic cavity increases. Volume of thoracic cavity decreases.
Air pressure in your lungs causes them to expand to Air pressure in your lungs causes them to
fill up the enlarged space in the thorax. compress.
Air pressure in the lungs decrease. Air pressure in the lungs increase.
Atmospheric pressure is higher than in lungs hence Atmospheric pressure is lower than in lungs hence
air rushes in. air rushes out.

3. How is carbon dioxide removed? How is oxygen absorbed?
Since the concentration of carbon dioxide in the Since the concentration of oxygen in the venous
venous blood is higher than in the alveolar cavity, blood is lower than in the alveolar cavity, oxygen
carbon dioxide diffuses from the blood vessels diffuses from the alveoli into the thin film of
through the alveolar wall and into the thin film of moisture and diffuses through the blood vessel wall
moisture on the inner alveolar wall after which it where it combines with the haemoglobin in RBCs
diffuses into the air and escapes. to form oxyhaemoglobin and it is transported.
How is gaseous exchange optimised?
1. A continuous blood flow ensures that the concentration gradient in the blood vessels are maintained.
2. Breathing in and out ensures that the concentration gradient in the alveoli are maintained.
Due to carbon dioxide’s insolubility with water, there is
another method how carbon dioxide is transported in the
blood.
1. CO2 + H2O ⇌ H2CO3 (via carbonic anhydrase)
carbon dioxide + water ⇌ carbonic acid
2. H2CO3 ⇌ H+ + HCO3-
carbonic acid ⇌ hydrogen + hydrogencarbonate ions
Stimulus for breathing: High concentration of carbon
dioxide in blood, and not low concentration of oxygen in
air.
Long exposure to irritants (eg. formaldehyde) cannot be coped by our defence mechanisms. It will cause
us to cough excessively leading to lung damage. As such they should wear protective masks.

4. Chemical in
Properties of chemicals Effects on the body
tobacco smoke
Addictive drug
Increased heartbeat and blood pressure
Nicotine Causes release of adrenaline
Increased risk of blood clotting in BVs
Makes blood clot easily
Combines with haemoglobin
to form carboxyhaemoglobin
Death if CO concentration > 1%
that reduces transport
Carbon monoxide Increased risk of coronary heart disease
efficiency of RBCs
Increases atherosclerosis Increased risk of blood clotting
Damages lining of BVs
Contains carcinogenic
Blockage in air sacs and reduction in
chemicals that induce
Tar gaseous exchange efficiency
uncontrolled cell division
Dust particles trapped cannot be removed
Paralyses cilia lining
Irritants Increased risk of chronic bronchitis and
Paralyses cilia lining
(eg. formaldehyde) emphysema
Chronic bronchitis:
The epithelium lining becomes inflamed. Excessive mucus is secreted by the epithelium. The cilia on the
epithelium are paralysed hence dust and foreign particles cannot be removed. The airways are blocked
and hence the person has to frequently cough violently to expel their dust. This increases the risk of lung
infections.
Emphysema:
Persistent coughing breaks the partition walls between the air sacs. This decreases the surface area for
gaseous exchange. Hence the lungs get inflated with air and lose their elasticity. As such breathing
becomes difficult. The person wheezes and suffers sever breathlessness.

5. Chapter 11: Excretion
Excretion – Process by which toxic materials and metabolic wastes are removed from the body of an
organism. Egestion – removal of undigested material from the alimentary canal = NOT EXCRETION.
Accumulation of nitrogenous and other compounds in an organism is harmful to the organism.
Excretory organs – Skin, kidney and lungs
URINE FORMATION
1. Ultrafiltration – mechanical filtration of different solutes (waste, nutrients) in the blood plasma,
except red and white blood cells that takes place due to a high hydrostatic blood pressure produced
by the difference in diameter between the afferent and efferent arteriole, in each glomerulus, through
a selectively permeable membrane.
For ultrafiltration to occur, there must be a high hydrostatic blood pressure formed because the
afferent arteriole has a larger diameter than the efferent arteriole. A partially permeable membrane
(aka. basement membrane) must be present as it acts as a filter and only allows small molecules to
pass through.

6. 2. Selective reabsorption – process whereby useful materials are taken back into the blood stream by
osmosis (water), diffusion and active transport (glucose, amino acids)
Region Processes
- Most of the mineral salts and all of the
glucose and amino acids reabsorbed by
First convoluted tubule diffusion and active transport.
- Most of the water is reabsorbed by osmosis.
Loop of Henle - Remaining water is reabsorbed by osmosis.
- Remaining water is reabsorbed by osmosis.
Second convoluted tubule
- Mineral salts (eg. Na+) is reabsorbed by
diffusion and active transport.
Collecting duct - Remaining water is reabsorbed by osmosis.
Excess water, excess salts and metabolic waste products (eg. urea, uric acid and creatinine) pass out of
the collecting duct into renal pelvis as a mixture called urine.
OSMOREGULATION WITH ANTI-DIURETIC HORMONE (ADH)

7. Dialysis
1. Kidney failure is fatal as the body is not able to remove waste materials such as urea and other toxic
chemicals.
2. Patients suffering from kidney failure can use a kidney dialysis machine to remove urea as well as
balance their salt concentration.
3. Blood is drawn from an artery in the patient’s arm and flows through a narrow tubing throught the
dialysis machine and is soon returned to a vein in the patient’s arm.
Characteristic of dialysis How it helps?
Allows only small solutes such as urea, excess salts and
Partially permeable
water to diffuse out from the blood while RBCs and
tubing
WBCs remain in the blood.
Increases surface area to volume ratio to increase the
Long, narrow and coiled
rate of diffusion.
tubing
Ensures that these substances do not diffuse into the
dialysis fluid when the blood plasma has a higher
Same concentration of concentration of these substances.
essential substances as
normal blood plasma Allows these substances to diffuse into the blood when
the blood plasma has a lower concentration of these
substances.
Ensures a steep concentration gradient which increases
No metabolic waste in
the rate of diffusion of waste products to be diffused
supplied dialysis fluid
out into the dialysis fluid.
Direction of blood flow is
opposite to direction of Maintains the concentration gradient at all sections of
flow of dialysis fluid the dialysis machine to increase rate of diffusion.
Treatment is 2-3 times a
Allows sufficient time for the waste products to be
week for a few hours
removed from the blood.

8. Chapter 12: Homeostasis
Homeostasis is the maintenance of a constant internal environment.
4 basic principles of homeostasis:
1. Stimulus – change in the internal environment
2. Receptor – detects the stimulus
3. Corrective mechanism – reverses effects of stimulus
4. Negative feedback – provides information to receptor to stop corrective mechanis,
Structure of mammalian skin
REGULATING HEAT IN THE BODY

9. Chapter 13: Nervous System
1. Central nervous system (CNS) consists of brain and spinal cord, Peripheral nervous system (PNS)
consists of cranial nerves and spinal nerves.
2. CNS does not come in direct contact with external environment. PNS comes in direct contact with
external environment.
direction of nerve impulse
direction of nerve impulse
Neurone part Form and function
Contains nucleus and much of cytoplasm; most
Cell body
of the metabolic activity of the cell occurs here
Axon Transmits impulses away from the cell body
Dendrons Transmits impulses towards the cell body
Dendrites Terminal branches on axons and dendrons
Layer of fatty substance that encloses the nerve
Myelin sheath
fibre and insulates axon
Neurilemma Thin membrane surrounding myelin sheath
Motor end plate (applicable to motor neuron) Junction between dendrite and muscle fibre
Regions where myelin sheath is absent allow
Nodes of Ranvier nerve impulses to jump from node to node,
increasing the speed of nerve transmission

10. Path of a nerve impulse
STIMULUS causes RECEPTOR to create impulse…
Step 1: Sensory neuron at receptor 
Step 2: Sensory neurons in nerves 
Step 3: Sensory neuron at dorsal root ganglion 
Step 4: SAME sensory neuron in dorsal root 
Step 5: SYNAPSE with relay neuron in grey matter in spinal cord
(neurotransmitters released) 
Step 6: Brain (processes information) 
Step 7: Relay neuron in grey matter in spinal cord 
Step 8: Motor neuron in ventral root 
Step 9: Motor neuron in nerves 
Step 10: Effector…
EFFECTOR causes RESPONSE
3. The nervous system serves to coordinate and regulate bodily functions.
4. A reflex is an immediate response to a specific stimulus without conscious control.
5. A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to the
effector in a reflex action.
6. Receptor and effectors –
i. Knee jerk reflex: Sensory receptor in patellar tendon, upper thigh muscle
ii. Hand on hot object reflex: Thermoreceptors, biceps