1. The Nervous System

2. Functions
integrative
(perception)
motor
(effector)

3. peripheral nervous system
Neurons in brain and spinal cord= Central Nervous System (CNS)
Nerves that connect CNS to rest of body= Peripheral Nervous System (PNS)
peripheral nervous system

5. Neurons- transmit electrochemical “information” as nerve impulses along nerve fibers

6. Nerve impulses are carried to Effectors (muscles and glands)

7. Neuron Structure Cell body- main structure
Dendrites- receive impulses, one or many
Axon- sends impulses, branched, usually only one

8. Large axons of peripheral neurons are enclosed in sheaths of neuroglia called Schwann cells
Myelin sheath- contains lipid-protein
Surrounded by membrane called Neurilemma

9. Nodes of Ranvier- gaps between Schwann cells of myelin sheath

10. Myelinated cell fibers appear white (white matter)
Unmyelinated fibers and cell bodies appear gray (gray matter)

11. Path of travel
Sensory Neurons---Interneurons---Motor Neurons
Figure 12.10

13. Types of Neuroglia
Microglial cells- support and phagocytosis in CNS

14. Oligodendrocytes- form myelin sheaths in brain and spinal cord (CNS)

15. Astrocytes- between neurons and blood vessels; support, nutrient regulation, form scar tissue (CNS)

16. Ependymal cells- form epithelial-like membrane that covers parts of brain and forms inner lining that encloses spaces within brain and spinal cord (CNS)

17. Schwann cells- myelinate PNS

18. Satellite cells: surround cell bodies of PNS ganglia

19. Greater Na+ concentration outside Greater K+ concentration inside
All resting neurons are polarized (different charge outside than inside),
determined by ions, channel pores in membrane
K+ crosses easily; Na+ and Ca++ with more difficulty
Greater Na+ concentration outside
Greater K+ concentration inside

20. resting potential action potential
Due to diffusion- resting nerve cell always has a slight surplus of positive charge outside and slight surplus of negative charge inside
This is called resting potential
resting potential
action potential

21. A threshold potential must be reached to achieve an action potential
Na+ permeability suddenly increases, resulting in an inward rush (action potential)

22. Nerve impulse- when one action potential stimulates adjacent portions of nerve fiber to reach threshold potential and thus action potential
Results in a wave of action potentials moving down a nerve fiber

23. The firing of a nerve is an “All or None” response (due to threshold potential)

24. Neurotoxins
tetrodotoxin

25. Certain local anesthetics decrease membrane permeability to sodium ions

26. Synaptic transmission occurs between axon of one neuron (sending signal) and dendrite or cell body of another neuron (receiving signal)

27. At this gap, Neurotransmitters are released from synaptic vesicles

28. Certain neurotransmitters increase ion permeability (excitatory)
Others decrease permeability (inhibitory)

29. Gamma-aminobutyric acid (GABA) Glycine Glutamate Aspartate
Small Molecule Neurotransmitter Substances
Acetylcholine (ACh)
Dopamine (DA)
Norepinephrine (NE)
Serotonin (5-HT)
Histamine
Epinephrine
Amino Acids
Gamma-aminobutyric acid (GABA)
Glycine
Glutamate
Aspartate
Soluble Gases
Nitric Oxide (NO)
Carbon Monoxide
Neuroactive Peptides - partial list!!</FONT< td>
bradykinin
beta-endorphin
bombesin
calcitonin
cholecystokinin
enkephalin
dynorphin
insulin
gastrin
substance P
neurotensin
glucagon
secretin
somatostatin
motilin
vasopressin
oxytocin
prolactin
thyrotropin
angiotensin II
sleep peptides
galanin
neuropeptide Y
thyrotropin-releasing hormone
gonadotropnin-releasing hormone
growth hormone-releasing hormone
luteinizing hormone
vasoactive intestinal peptide