1. Nerve cells and their support system
Nervous tissue
Nerve cells and their support system

2. A few terms Central nervous system (CNS) – brain & spinal cord
Peripheral nervous system – nerves that extend from the CNS to muscles, glands & sense organs.

3. Nervous system function – control center of the body
Sensory input - Monitor internal and external changes
Integration – processes and decides a response if one is needed
Motor output – produces an effect via muscles or glands

4. Neurons (nerve cells)
Cell body – contains the nucleus, ribosomes and the rest of the material for running the cell
Dendrites – outgrowths of the cell body that are branched, receive information from other cells and send it onto the cell body
Axon – (nerve fiber) long extension from cell body that carries information to a target cell. Can be a few mm to over a m.
Axon terminals – branched end of the axon that releases the neurotransmitters that communicate with another nerve cell

5. Glial cell Support the neurons both physically and metabolically
Make up 90% of cells in the nervous system
Found around all parts of the cell
Provide nutrients to the cells
Clear waste & neurotransmitters from the area
Block toxins & provide immune protection

6. Myelin sheath Manufactured by Schwann cells, a type of glial cell
Speeds conduction of the electrical signal
Conserves energy

7. Types of neurons
Afferent neurons – carry information from tissues and organs to the brain & spinal cord
Interneurons – connect neurons in the brain and spinal cord
Efferent neurons carry information from the CNS to rest of the body, particularly muscles and glands

8. Nerve impulse – Action Potential
Action potential – rapid changes in the charge distribution outside and inside the cell. Self propagating, travels like a wave.
Na+ & K+ are the primary ions involved, Cl- also plays a role
Pumps in cell walls return charges back to normal. ml

9. Synapse The junction between 2 neurons
Includes the ends of both neurons and the space between them

10. Types of synapses
Electrical – nerve impulse (action potential) gets sent directly from one neuron to another. Fastest
Chemical – a neurotransmitter is released that carries information across the synapse to the next neuron. Slower. Action potential causes changes in the axon terminal that cause vesicles filled with neurotransmitters to fuse w/ the cell membrane & release their contents. The neurotransmitters then cross the space and bind with the next neuron. Then the action potential continues.

11. Neurotransmitters
Acetylcholine (ACh) is a predominant neurotransmitter.
Synthesized in the nerve cell
Enzymes and diffusion rid the synapse of ACh following each impulse
Alzheimer’s – degeneration of ACh system
Many ACh receptors also bind nicotine

12. All or nothing
A nerve impulse is sent along an axon or dendrites only if the signal is strong enough to generate a response.
If the signal is not strong enough no impulse is sent.
All action potentials are the same strength
Degree of response is due to the number of nerves involved.

13. Neuron repair Outside the CNS neurons can make repairs
If axon is cut & cell body is not damaged, the end that is no longer attached degenerates, but the attached end can grow out and restore some function.