1. The Nervous System

2. Nervous system is divided into 2 parts: Central Nervous System (CNS)
Brain and Spinal Cord
Peripheral Nervous System (PNS)
Nerves that carry messages between CNS & rest of body.

3. To make the correct response to a stimulus,
4 processes are involved
Reception, a stimulus is detected, this is the function of neurons & sense organs
Transmission, msg passes along neurons
Receptors -> PNS -> CNS
CNS -> PNS -> Effectors (muscles)
Integration, Msgs are sorted and processed and a response decided upon.
Response, carried out by effectors when stimulated by neurons

4. Neurons Is a nerve cell, specialised to carry info 3 types of neurons
Sensory
To Brain
Motor
To muscles
Interneuron's
Between Sensory & Motor

5. Structure of Neurons
Neurons vary in size, neurons in the brain are tiny, neurons connecting the spine & feet may be over 1 metre long.

6. Structure of Neurons
Cell Body-contains nucleus & organelles & produce neurotransmitter chemicals.
Group of cell bodies outside CNS called Ganglion
Dendrites-carry impulses towards the centre of the neuron to the cell body
Axon- carry impulses away from the centre of the neuron to the cell body

7. Structure of Neurons
Neurotransmitter vesicles-at the end of axons, these swellings release chemicals that carry the impulse from 1 cell to another. Chemicals called neurotransmitters
Schwann cells, located along neurons, make myelin sheath.
Myelin sheath, fat rich membrane that insulates the electrical impulses (MS patients lack this)

8. Interneurons
Short neurons found in CNS.
Not enclosed in Myelin sheath
They connect motor & sensory nerves

9. Movement of Impulses
When a neuron receives a stimulus an electrical impulse travels along the dendrite & axon to the neurotransmitter swellings
The movement of the electrical impulse along a neuron involves the movement of ions.
When an neuron is Not carrying an impulse ions are pumped in & out of the axon. This results in the inside of the axon being –ive and the outside +ive
Threshold, is the minimum stimulus needed to cause an impulse

10. Movement of Impulses
Once the threshold is reached the axon changes its permeability to ions
At the site of stimulation the inside of the axon becomes +ive & the outside –ive.
This change in charge causes the next section of the axon to alter its permeability
A chain reaction is set up & a movement of +ive charges runs along the inside of the Axon.
Energy (ATP) is needed to cause these changes
Diagram 34.6 pg 322

11. Synapses
Neurons are not connected to each other, they are separated by a small gap, Synaptic cleft.
Synapse is the region where 2 neurons come into close contact.
Electrical impulses cannot cross a synapse, instead they stimulate the neurotransmitter swellings to release a chemical substance (neurotransmitters), which diffuse across the synaptic cleft

12. Synapse
After the nerotransmitters diffuse across the synaptic cleft the combine with receptors on the postsynaptic neuron.
This causes an impulse to be regenerated
The neurotransmitter is then broken down by enzymes. The digested NTs are reabsorbed into the neurotransmitter swellings and recycled.

14. The CNS-The Brain The brain contains over 1200 million neurons
The brain & spinal cord is protected by bone & 3 membranes called Meninges
Meningitis is an inflammation of these Meninges caused by virus or bacteria
Viral meningitis is less severe
Bacterial meningitis can lead to death

15. Structure of the Brain Cerebrum Largest part of the brain
Outer part called cerebral cortex
controls voluntary movements
Right controls left Left controls right Strokes

16. Structure of the Brain Cerebellum Medula Oblongata
controls muscular coordination
2nd largest
Medula Oblongata
involuntary once the process has been learned
Controls breathing,
blood pressure, swallowing, coughing
Connects the spinal cord with the rest of the brain

17. Structure of the Brain Hypothalamus Thalamus
links with pituitary gland
located below the thalamus
regulates the internal environment
Thalamus
located below the cerebrum
sorting centre

19. Spinal Cord
Composed of nerve tissue, surrounded by vertebrae which protects it.
Transmits impulses to & from the brain
Is located in the neural canal of the vertebrate
The neural canal is lined by the meninges & contains cerebrospinal fluid
Dorsal root carries sensory neurons into the spinal cord & the ventral root carries motor neurons out
Dorsal & ventral roots combine to form 31 pairs of spinal nerves

21. Reflex Action
Is a quick, automatic response to a particular stimulus.