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The central and peripheral nervous system
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The central nervous system is essential to human function
o It is the master control centre for our emotions, senses, responses, reactions, body
balance like temperature and heartbeat as well as the activities of our muscles and
glands
o The nervous system controls and coordinates our bodily functions
The nervous system is divided into two main groups
o The Central nervous system (CNS) comprises the brain and spinal cord and acts as the
control centre for the nervous system. Information from the senses is interpreted here
and command actions are issued to other parts of the body
o The Peripheral nervous system (PNS) comprises of the connecting nerves which link the
brain and spinal cord to and from the rest of the body.
 Nerves connecting to the brain are called cranial nerves
 Nerves connecting to the spinal cord are called spinal nerves.
 The PNS carries the messages from the sensory organs along sensory nerves to the
CNS and carries messages from the CNS along motor nerves out to the muscles
and glands
 Between motor nerves and sensory nerves are interneurones
The sense organs
o Human senses enable us to be aware of environment
 See
 Touch
 Taste
 Hear
 Smell
o Sense organs are made up of sensory cells that receive and convert information from
our sense into electrical impulses for the brain
o The role of sense organs in the body is to respond to the environment and to relay these
changes to the central nervous system
The neurone consists of a cell body from which long thin strands reach out.
o Axon
 away from cell body
 Longer than dendrite
 Myelin insulator
 Efferent transmission
o Dendrite
 Towards cell body
 Shorter than axon
 Afferent Transmission
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There are billions of neurones in the body, and so we barely grow new neurones ( once
destroyed, they are gone forever)
o The myelin is used as an insulator to stop impulses jumping from one neurone to
another
o As the nerve impulse passes, there is a flow of sodium and potassium ions across the
axon membrane. For a short time, the outside is made negative and the inside positive.
After the impulse has passed by, there is a brief period during which another impulse
cannot pass, as the cell pumps the ions back to where they came from.
Types of nerve cells
o Sensory nerve cells
 Carry impulses from receptors in sense organs to CNS
 Afferent transmission
o Motor neurones
 Carry impulses out from the brain or spinal cord to the muscles or glands.
 The muscles and glands are called effectors
o Interneurones
 Connect the sensory neurones to the motor neurones
 Transmit message from the senses to the effectors via CNS
 Often Small
Reflex Arc
o Reflexes are actions that your body performs without you having to think about them
o A reflex arc is the nervous pathway along which the impulses travel for a reflex action
 Examples are:
 Knee Jerk
 Eyes to light
Nervous messages
o The nervous impulse arrives at the synapse at the end of a neurone
o The impulse triggers some chemical messengers at the end of the neurone to release
chemicals (called neurotransmitters) into the synaptic gap
o These chemicals travel across the gap and stimulate a new impulse in the adjoining
neurone
o Common neurotransmitters in the human body are:
 Acetylcholine-muscle control
 Noradrenaline-Adrenalin
 Dopamine
o Drugs and medicines can affect the transmission of nervous messages across the
synaptic gap
Transporting pharmaceuticals in the body
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The circulatory system is a transport system where blood carries oxygen, carbon dioxide,
hormones and other materials
It carries supplies to the body's cells and removes waste products
The system depends on the pumping of the heart to maintain delivery and removal of
essential substances
Blood vessels: The human body has three main blood vessels
o Arteries
 Always carry blood away from heart
 Carries blood under high pressure
 Three layers of thick, sturdy, elastic muscular walls
o Veins
 Always carry blood to heart
 Also has three layers of tissue but not as thick as arteries
 Contains valves to stop back flow of blood.
o Capillaries
 Link Arteries to veins
 Tiny, one cell thick
 Extend into all areas of the body
 Do not contain muscular walls or valves
 Main function is to diffuse substances between the blood and the cells
Components of blood
o 55% plasma
 90% water
 Salts like sodium, potassium, calcium, magnesium, chlorides, bicarbonate which
assist in membrane functioning and osmosis.
 Proteins like albumin fibrinogen, immunoglobulins which help in maintaining body
immunity and blood clotting
 Other substances such as glucose, waste, respiratory gases and hormones
o 45% blood cells
 Red blood cells transport oxygen and carbon dioxide
 Lack nucleus
 Made in bone marrow
 Relatively small and flexible
 Inside is an iron-rich substance called haemoglobin
 White blood cells
 There are five types each with a specific job
 Basophil
 Mast cell
 Eosinophil
 Neutrophil
 Monocyte
 Fighting infection
 Preventing cancers
 Identifying tissue damage
 Also made in bone marrow
 Not confined to blood vessels
The circulatory system is particularly important at distributing drugs to parts of the body
Pharmaceuticals to reduce pain and inflammation
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The human body's first line of defence is the system of the skin
o Skin coated with antibacterial and antifungal acids made by swat and glands on surface
o Moist areas encourage natural bacteria to grow to help defend the body
o Membranes covered with mucus coat
o Body fluids like saliva, urine, perspiration, tears and nasal secretions contain
antimicrobial substances to flush the body clear at these sites of entry
Damage to skin or other membranes stimulates inflammatory response
o This is the body's second line of defence
Stages in the inflammatory response
o Release of chemical alarm signals
o Blood vessels dilate and become more permeable
o White blood cells enter the tissue
o Inflammation is present
o Spread of damage is restricted
Advantages of inflammation
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Disadvantages of inflammation
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Chemical alarms like histamines are 
released to attract defence agents to
the site of infection
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Heat from increased blood flow to
area attracts antimicrobial agents
and dilated vessels enables them to
reach affected tissues. A higher
metabolic rate also speeds up cell
repair
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Heat can upset the body's temperature
regulator and may produce fever. Very high
fevers can denature enzymes in the body,
damage body proteins and in severe cases
may result in death
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Swelling and redness draw more
nutrients, oxygen, white blood cells
and plasma to the site of tissue
damage which assist in neutralising
toxins and cleaning up the area.
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Swelling can cause temporary loss of
movement in joints and pain. Long-term
swelling may result in permanent tissue
damage.
Some histamines are present in allergic
reactions which can cause runny noses,
hives, cramps, swelling or diarrhoea
Prostaglandins are local hormones derived from fatty acid molecules that modify the effects of
other hormones.
o They are produced by cell membranes not glands
o They help
 Promote inflammation
 Enhance pain by making pain receptors more sensitive
 Produce fever by their actions in the hypothalamus
 Regulate blood pressure
 Promote blood clotting
 Start muscle contraction during childbirth
 Control the sleep/wake cycle
An analgesic acts as a prostaglandin inhibitor which reverses its effects
o Aspirin is an analgesic with the chemical acetylsalicylic acid
Bacteria
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Bacteria belong to the kingdom Monera and are commonly called prokaryotes
A prokaryote is an organism whose small, simple cells lack membranes around their nucleus,
mitochondria and chloroplasts
Bacteria can be classified based on their shape
o Cocci
 Small spherical-shaped bacteria often found in chains or clusters
o Bacilli
 Rod-shaped bacteria commonly found in soil and can also be found singly, in pairs
or in chains.
o Spirilla
 Curved or spiral-shaped bacteria which is the least common
Bacteria have unique shapes which is the main means used in their naming and classification.
Structure of bacteria
o Flagella
o Pili
o Capsule
o Cell wall
o Cell membrane
o Cytoplasm
o Plasmid
o Nuclear area containing DNA
Bacterial Reproduction uses the process of binary fission
o Reproduction in bacteria will be affected by a number of conditions
 Temperature
 Moisture conditions
 Available food supply
Penicillin is obtained from a fungus (mould) and is a good antibiotic as it acts on bacterial cells
in the act of dividing.