1. Chapter 12
The Nervous System

2. The Nervous System
Central Nervous System
Peripheral Nervous System

3. Peripheral Nervous System
Somatic
Autonomic
Enteric

4. Central Nervous System
Brain
100 billion neurons
12 pairs of cranial nerves
Spinal Cord
Connected to the brain
100 million neurons
31 pairs of spinal nerves
Ganglia

5. Peripheral Nervous System
All nerves outside the CNS
Somatic-
Sensory neurons from somatic receptors in head, body wall,
limbs, and from special sense organs (vision, hearing, taste
and smell) to the CNS.
Autonomic-
Sensory neurons from autonomic sensory receptors
(visceral organs-e.g. stomach, lungs)
Motor neurons from CNS to smooth muscle, cardiac muscle,
and glands. ANS=involuntary.
Sympathetic vs Parasympathetic
Enteric-
Enteric plexus extends through the GI tract. Monitor GI tract.
Contraction of GI smooth muscle as well as secretion
(e.g. stomach acid)

6. Parts of a Neuron

7. Neuron

8. Multipolar Neuron
Most neurons of the CNS are multipolar

9. Unipolar Neuron
Most neurons of ganglia are unipolar

10. Bipolar Neuron
Some neurons of the retina, the ear, and the olfactory bulb are bipolar

11. Neurons do not all look the same-why?

12. Glia-Astrocyte Largest type of glial cell
Processes make contact with blood capillaries, neurons,
and the pia matter
Function to support neurons, create blood-brain barrier,
secrete and takeup ions, neurotransmitters, and nutrients

13. Glia-Oligodendrocyte
Smaller than astrocytes, form myelin sheaths around CNS axons

14. Microglia
Small cells act primarily as phagocytes

15. Neuroglial cells in the PNS
Schwann Cells
wrap around PNS axons (like oligos in CNS)
except that each schwann cell myelinates a single axon
Satellite Cells
Flat cells that surround cell bodies of neurons in PNS ganglia
Help to regulate exchange between cells and interstitial fluid

16. Myelination
In CNS and PNS
Gaps-nodes of Ranvier

21. Ion Channels
Leak channels-randomly open and close at rest providing a measure of permeability
Voltage-gated channels-open and close in response to a change in membrane potential (voltage).
Ligand-gated channels-open and close in response to binding chemicals (e.g. ACh binding to its receptors opens a cation channel)
Mechanically-gated channels-open and close in response to mechanical stimulation (e.g. vibration, touch, pressure, stretch). Auditory receptors in the ear are channels that open in response to movement of inner ear bones).

22. Voltage-gated channels

23. Ligand-gated channels

24. Resting membrane potential-charge distribution

25. Resting membrane potential-ion distribution

26. Ion Permeability-resting membrane potential
(Buildup of negative ions in cytosol and positive ions on outside of membrane
causes charge difference acrosss membrane)
Na permeability is low
Few leak channels and Na/K pumps (pump 3 Na2+ out
and 2 K+ in).

27. Graded potentials
Hyperpolarizing
Depolarizing

28. Phases of the action potential

29. Phases of the action potential

30. Action potential propagation-non myelinated

31. Action potential propagation-myelinated

32. Neurotransmission

33. Neurotransmission-spatial summation

34. Neurotransmission-temporal summation

35. Channel locations on neurons

36. Neural Circuits

37. Circuit example There are three basic parts of a neural circuit:
the sensory input-the sensory neuron detects the stretching of the muscle
the information processing-this circuit has only a few synapses and is very short, which is why it acts so quickly. It also functions with no intervention by the conscious brain, which has better things to do than constantly remind the body to stay upright.
the motor output- stmulation of a motor neuron responsible for contracting the extensor muscle.

38. End of Chapter 12