1. Gr.12 Life Sciences
Human nervous system

2. THE NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM CRANIAL NERVES
SPINAL NERVES
CENTRAL NERVOUS SYSTEM
BRAIN
SPINAL CORD
AUTONOMIC NERVOUS SYSTEM
PARASYMPATHETIC
SYMPATHETIC

3. The Nervous system How does our nervous system work? Response Stimulus
Receptor
Sensory neuron
Central
Nervous
system
Motor neuron
Effector
Response

4. Structure of the brain and the functions
Cerebrum
• Controls voluntary
actions
• Receives and interprets
sensations from sense
organs
• Higher thought processes
Corpus callosum
Connects the left and
right hemispheres of
the brain – allowing
communication between
both hemispheres
Cerebellum
• Coordinates all
voluntary movements
• Controls muscle
tension to maintain
balance
Medulla oblongata
• Transmits nerve impulses
between the spinal cord
and the brain
• Controls involuntary
actions such as heartbeat
and breathing
Hypothalamus
Control centre for hunger,
thirst, sleep, body
temperature and emotions

5. Questions 1. Write down the name of the part which:
1.1. Controls heartbeat (1)
1.2. Contains the centres that control balance, muscle tone and
equilibrium (1)
1.3. Has centres that interpret what you see (1)
1.4. Coordinates voluntary muscle movements (1)
1.5. Controls body temperature (1)
[5]

6. Answers
1.1. Medulla oblongata √ (1)
1.2. Cerebellum √ (1)
1.3. Cerebrum √ (1)
1.4. Cerebellum √ (1)
1.5. Hypothalamus √ (1)
[5]

7. Neurons
Neurons are specialised cells which connect the brain and spinal cord to all other parts of the body.
There are 3 types of neurons (nerve cells)
Sensory neurons:
Conduct impulses from the receptors TO the
central nervous system
Motor neurons:
Conduct impulses FROM the central nervous
system to effectors like muscles and glands
Connector / inter-neurons:
Connect sensory neurons to motor neurons

8. Neurons
Axon

9. Neurons

10. Neurons
The Synapse
The synapse is the point where an impulse passes from the terminal branch of one neuron to the dendrite of the next neuron.
The neurons NEVER touch each other.
The gap between the two neurons is called the synaptic gap.
Chemical neurotransmitters such as acetylecholine/dopamine/serotonin help to transmit the impulse from one neuron to the next across the synaptic gap.

11. The reflex arc
A reflex arc is the path travelled by the nerve impulses.
It is a rapid automatic response to a stimulus that is received by a sensory organ to ensure a quick response.
The reflex arc will cause the body to respond very quickly as a reflex action, allowing it to protect against possible severe injury.

12. The Spinal Cord
Protection: vertebrae, meninges and cerebrospinal fluid.
There are 31 pairs of spinal nerves that enter from the body.
The spinal cord is the pathway for all impulses conducted to and from the brain.
The grey matter lies on the inside in the shape of an ‘H’
The white matter lies on the outside (opposite to the cerebrum).
The spinal cord processes all reflex actions.
The spinal cord functions automatically and is not controlled by the will.
Sympathetic and parasympathetic nerve impulses are conducted along the spinal cord to all organs.

13. The Spinal Cord

14. The Spinal Cord

15. Questions
muscle 3 1
hummer 5 2
Organ
Spinal cord
Right leg 4

16. Questions
Study the above diagram of longitudinal section of the human brain, a cross-section of the spinal cord and the right leg.
1. Identify the parts 1, 2 and 5. (3)
2. What will be the effect on the body if part 5 is damaged? (1)
3. Mention three disorders of the nervous system. (3)
4. Describe the reflex action shown in the diagram. (13)
5. Draw and label the type of neuron as indicated by NUMBER 4. (10)

17. Questions Human Nervous system – MEMO 2.5 2.1 1 - cerebrum/ brain √
2 - medulla oblongata √
5 – cerebellum √ (3)
2.2 Lack of muscle control/lack of co-ordination/ bad posture
/ upset equilibrium √ Any 1 (1) √
2.3 Alzheimer’s Disease √,
Attention Deficit Disorder, √
Depression √ (3)
2.4 Hammer strikes the knee √ stimulating the touch corpuscles/receptors. √
An impulse is transmitted along the dorsal root √ to the dorsal horn √
where the sensory neuron √ makes a synapse with an interneuron. √
It moves along the motor neuron in the ventral horn √, along the ventral root √ to the effector √, the muscles in the leg. √ The leg is
raised upwards. √ At the same time an impulse moves to the brain √ to be interpreted. √ (13)
2.5