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LIFE SCIENCES
2011
J Gerber and J Goliath
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Hormones and nerves enable animals to:
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Respond to internal and external change
Co-ordinate the various activities of the body
Observations of the response of some
invertebrates e.g wood lice, to light and
humidity
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The need for a nervous system in humans in
terms of:
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Reaction to stimuli (external and internal)
Co-ordination of various activities of the
body
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Location and functions of :
Cerebrum
Hypothalamus
Cerebellum
Medulla oblongata
Spinal cord
Model of human brain
Observe and draw the external structure of
the brain
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Dagga
Heroin
Ecstacy
Tik
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Peripheral nervous system
 Location and function
Autonomic nervous system
 Location and function
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Causes, symptoms, treatment of ONE of the
following diseases/disorders of the nervous
system:
Alzheimer’s Disease OR
Attention Deficit Disorder OR
Depression
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Generalised structure of a neuron including:
nucleus, cell body, cytoplasm, myelin sheath, axon
and dendrites
Labelled drawings to show the three types of
neurons from microscope slides or micrographs
Structure and functions of the three types of
neurons
The nerve is composed of nerve fibres held
together by connective tissue
Transmission of nerve impulses along neurons and
across synapses using neurotransmitters (no detail
of electrical charges needed)
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Difference between reflex arc and reflex action
Observe microscope slides and draw and LABEL
the cross section through the spinal cord
Structure of a simple reflex arc (receptor,
sensory neuron, dorsal root of spinal nerve,
spinal cord, interneuron, motor neuron, ventral
root of spinal nerve, effector)
Functioning of the reflex arc, use an example
Significance of a reflex arc
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Receptors on the skin of wood lice are
sensitive to humidity and light
Wood lice move away from light and dry
environments
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The systems below work together to
respond to external and internal changes:
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Nervous system
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Endocrine system (hormones)
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Location
Largest part of the brain is situated in the skull.
Functions
Centre of all voluntary actions
Contains areas that receive and interpret nerve
impulses from the sense organs for the
sensation of smell, sound, sight, taste and
touch.
Centre of higher mental functions e.g memory,
intelligence, emotions etc.
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Location
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Situated under the thalamus.
Functions
Reflex control centre of mechanisms such as
temperature, blood pressure, sleep and
emotion
Produces certain hormones e.g. ADH which
assist in maintaining water balance
Control centre for homeostasis
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Location
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Situated behind and underneath the cerebrum
Functions
Controls the co-ordination of voluntary
movements
Contain the centres which control balance
and equilibrium
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Location
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Forms bottom part of the brain stem and is
an extension of the spinal cord
Functions
Transmitter of impulses between brain and
spinal cord
Controls autonomic functions e.g. breathing,
heartbeat, peristalsis, widening and
narrowing of blood vessels
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Location
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Extends from the medulla oblongata through
the vertebral canal to the lumber region
Functions
Provides a pathway for nerve impulses to and
from the brain
Contains reflex centres that initiate reflex
actions
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Dagga
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Chemical substance in dagga combines with
specific receptors (memory, concentration,
movement) in the brain and inhibits the
normal functioning of these receptors.
Heroin
Has a depressive affect on the CNS, slows
down breathing and suppresses pain.
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Heroin
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This drug has a depressive effect on the CNS,
slows down breathing and suppresses pain.
Inhibits the activity of the medulla oblongata.
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Ecstacy
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Causes an excessive release of a certain
neurotransmitter which over stimulates brain
neurons which causes damage to the terminal
branches of the axons
Negative effect on the emotions, memory and
ability to learn.
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Tik
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Has a stimulating effect on the CNS e.g.
accelerated breathing and heart rate.
Causes an excessive release of a certain
neurotransmitter which over stimulates
neurons in the brain and damage these
neurons
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Location
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Nervous tissue found outside the CNS and is
subdivided into the somatic and autonomic
nervous systems. Consist of 12 pairs of cranial
nerves and 31 pairs of spinal nerves
Functions
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Conduct nerve impulses from the receptors to
the CNS, along the sensory neurons
Conduct nerve impulses from the CNS to the
effectors, along the motor neurons
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Location
Consists of nerves which are connected to the CNS.
Consists of the following systems i.e. sympathetic
and parasympathetic.
Functions
Controls all involuntary actions.
Conducts nerve impulses from the CNS to the
effectors e.g. muscles and glands.
Sympathetic system prepares the body for
emergency.
Parasympathetic system allows the body to return
to normal after stimulation by the sympathetic
system – antagonistic.
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Same basic structure as any other cell.
Cell body consists of cytoplasm and a nucleus.
Cytoplasm contains Nissl granules which are
rich in RNA and play a role in protein synthesis.
Two types of outgrowths – dendrites and
axons.
Dendrites conduct nerve impulses to the cell
body.
Axons conduct impulses away from the cell
body.
Axons are surrounded by a myelin sheath for
protection.
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Neurons are classified based on the number of
outgrowths projecting from the cell body.
Structure of different neurons
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Monopolar neurons – one outgrowth that
branches into two, i,e, one dendrite and one
axon.
Bipolar neurons – two outgrowths, i.e. a
dendrite and axon.
Multipolar neurons – many outgrowths, a
number of dendrites and one axon.
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Neurons are classified according to their
function as follows:
Sensory or afferent neurons – conduct
impulses from the receptors to the CNS and
are mostly monopolar.
Motor of efferent neurons – conduct
impulses from the CNS to the effectors and
are multipolar.
Interneurons or connector neurons –
connect sensory and motor neurons in the
CNS and are multipolar.
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Neurons are bundled together in the human
body.
Small bundles of axons are called nerve
fibres.
Nerve fibres are bundled together with some
connective tissue.
Nerve fibres and connective tissue make up
nerve tissue.
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Neurons are interconnected to form a
continuous conduction system throughout
the body.
The axon of one neuron connects with the
dendrites of the next neuron.
Successive neurons are not directly
connected to each other, but seperated by a
small gap.
A physiological (functional) connection is
formed known as a synapse.
The gap is called the synaptic cleft.
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A receptor is stimulated by a change in the environment and
produces impulses.
Dendrites of a sensory neuron conduct these nerve impulses
to the cell body.
Nerve impulses are conducted from the cell body along a
single axon to the terminal branches.
Ends of terminal branches do not touch the dendrites of the
neurons in the spinal cord because of a gap.
Ends of terminal branches of axons contain neurotransmitters
which are released into the synapse when the terminal
branches of axons are stimulated by an incoming impulse.
Neurotransmitters play a role in the transmission of nerve
impulses.
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Reflex action – a quick, automatic
movement/action by an effector, in response
to a stimulus received by a recepto.r
Reflec arc – pathway along which nerve
impulses are carried from a receptor to an
effector to bring about a reflex action.
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Receptor – detects a stimulus and converts
into a nerve impulse.
Sensory neuron – conducts the nerve
impulse to the grey matter of the spinal
cord.
Interneuron – serves as a reflex centre in
the grey matter of the spinal cord and
conducts nerve impulses from the sensory
neuron to the motor neuron.
Motor neuron – conducts the nerve
impulses from the spinal cord to the
effector.
Effector – reacts to the original stimulus.
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Heat stimulus received by a receptor and
convert into a nerve impulse.
Nerve impulse is transmitted by the sensory
neuron through the dorsal root of spinal
cord.
Sensory nerve transmits the impulse to the
interneuron in grey matter of spinal cord.
Neuron is connected synaptically to the
motor neuron.
Axon of the motor neuron transmits the
impulse through the ventral root to the
effector.
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Reflex arcs protect the body from dangerous
situations from the external environment.
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Instructions
 Explanation of activity on a reflex arc.
 After 10 minutes each pair/group/individual
give feedback.
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QUESTION 1
Tommy was keeping his finger over a burning candle. In about 0,2
seconds he pulled his finger away.
1.1
1.2
What type of action is Tommy’s reaction?
Explain your answer to QUESTION 1.1
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QUESTION 1.3
Diagram 1 below shows a cross section through Tommy’s spinal cord.
Diagram 2 shows Tommy’s finger over the burning candle and a muscle
in his arm. Draw the missing parts/structures and also indicate the path
(use different colours if possible) followed by the impulse during the
reaction named in QUESTION 1.1.
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1.1 Reflex
1.2 Reaction was quick/sudden; without even thinking about
it/autonomic.
1.3
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