1. THE NERVOUS SYSTEM

2. The Nervous System Central Nervous System Peripheral Nervous System BrainSpinal cord Cranial Nerves Spinal Nerves Ganglia

3. Neuron = Nerve cell Sensory Neuron (afferent) Carry electrical impulses from sense organs to the C.N.S Cell body is outside C.N.S in ganglia Motor Neuron (efferent) Carry electrical impulses from the C.N.S to effector (muscle/Gland) Cell body inside C.N.S

4. Interneurons Occur in the C.N.S only May connect sensory to motor neurons

6. Direction of impulse

7. Diagrams Draw diagram of sensory neuron and interneuron into notes

8. Functions of parts Dendrites – receive information and carry electrical impulses towards the cell body Axons – carry impulses away from a cell body Cell body – contains a nucleus and it forms neurotransmitter chemicals Myelin sheath – is a fat rich material that insulates electrical impulses Schwann cells – form myelin sheath Neurotransmitter swellings (vesicles) – produce neurotransmitter chemicals.

9. Dendron – brings impulse to the cell body Nodes of Ranvier – are gaps in the myelin sheath. Electrical impulse ‘jumps’ from one gap to the next  Speeds up transmission of impulse

10. Stimulus A change in the neurons environment that, if strong enough, will generate an impulse e.g. red light at traffic lights

11. Movement of an Impulse Impulses travels along an neuron in the form of an electrical impulse In order for the impulse to travel it is necessary for ions to move in and out of dendrites and axons The movement of ions requires energy in the form of ATP

12. Threshold level The minimum intensity of stimulus needed to generate an impulse It does not matter if the stimulus is above the required strength  the same message is sent Message sent in all neurons is the same All or nothing Law – an impulse is only generated if the stimulus is at or above the threshold.

14. Functions of parts Cerebrum – major sensory and motor control, language, memory, intelligence and consciousness. Cerebellum – muscle co-ordination, movement and balance.

15. Functions of parts Medulla oblongata – regulates breathing and heart rate. Hypothalmus – overall body homeostasis  osmoregulation, temperature control regulates hormone secretion by the pituitary gland. Pituitary gland – master gland - secretes 8 hormones which control other glands in the body

16. The Spinal Cord Bones of the backbone enclose the spinal cord. It carries impulses to and from the brain. It is also involved in many reflex actions

18. T.S. of spinal cord

20. Functions of parts The Meninges – are membranes that surround (the brain) and Spinal cord. Spinal nerves – 31 pairs of spinal nerves carry impulses to and from the spinal cord. Dorsal root – carries impulses into the spinal cord along sensory neurons. Ganglion – (pl. Ganglia) located on the dorsal root is a swelling that contains cell bodies of sensory neurons

21. Functions of parts White matter – contains axons Grey matter – contains cell bodies and dendrites. Central canal – contains cerebrospinal fluid. Ventral root – contains motor neurons that carry impulses out of the spinal cord

22. Reflex Action A reflex action is an automatic, unconscious or involuntary response to a stimulus. The brain is NOT involved in reflex actions Examples – knee jerk reaction, blinking for protection, raising your hands when falling Significance/Benefit  allows faster responses than normal

23. REFLEX ACTION --- The Reflex Arc

24. The path of a reflex action The path taken by a reflex action is called a reflex arc. Example : Dropping a hot object ŒReceptors in finger detect hot object Impulse travels along sensory neuron to spinal cord ŽImpulse travels into spine via dorsal root In the spinal cord the impulse splits

25. The path of a reflex action (a)It crosses a synapse onto an interneuron (b)It crosses another synapse and passes on up to the brain. From the interneuron the impulse crosses another synapse and travels out of the ventral root along a motor neuron ‘The motor neuron connects to a muscle to a