Gr.12 Life Sciences Human nervous system

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

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

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

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]

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

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

Neurons Axon

Neurons

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.

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.

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.

The Spinal Cord

The Spinal Cord

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

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)

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