1. The Nervous System : communication
A.  Neurons = masses of nerve cells that transmit information
1. Cell Body - contains the nucleus and two extensions 2. Dendrites – shorter, more numerous, receive information 3. Axons – single, long “fiber” which conducts impulse away from the cell body, sends information

2. Central Nervous System (CNS): brain and spinal cord.
Peripheral Nervous System (PNS): nerves of the body
                   -- Includes 31 pairs of spinal nerves
                   -- And  12 pairs of cranial nerves

3. THREE BASIC FUNCTIONS OF THE NERVOUS SYSTEM
Sensory -  gathers info
Integrative - information is brought together
Motor - responds to signals, homeostasis

4. Motor Functions Somatic Nervous System - skeletal (voluntary)
Autonomic Nervous System -  smooth muscles, glands (involuntary)

5. Neuroglial Cells (p 208) - support cells for the neurons
1.  Microglial Cells: scattered throughout, digest debris or bacteria
Microglial cells respond to immunological alarms

6. Neuroglial Cells (p 208) 2. Oligodendrocytes:
provide insulation around the axons

7. 3. Astrocytes: connect blood vessels to neurons
Neuroglial Cells  (p 208)
3. Astrocytes:  connect blood vessels to neurons
I connect to blood vessels

8. 4. Ependymal Cells: form a membrane that covers brain-like parts
Neuroglial Cells  (p 208)
4.  Ependymal Cells:  form a membrane that covers brain-like parts

9. Practice with neuroglia coloring!
5.  Schwann cells:  form the insulating myelin sheath around the neurons
       
Practice with neuroglia coloring!

10. Axon - long section, transmits impulses
Dendrite - small extensions from the cell body; receive information
Neurofibrils - fibers within the axon

11. Chromatophilic substance (rough ER) - transport system
Myelin -insulation surrounding axons
Nodes of Ranvier - gaps in the insulation

12. White vs Grey Matter
Myelinated (white matter) – myelinated axons
Unmyelinated (grey matter) - unmyelinated

13. Label

14. Interesting Facts about the Neuron
Longevity – can live and function for a lifetime
Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception
High metabolic rate – require abundant oxygen and glucose
The nerve fibers of newborns are unmyelinated - this causes their responses to stimuli to be course and sometimes involve the whole body.  Try surprising a baby!

15. Types of Neurons
Functional: Sensory, Motor, Interneurons
Structural: (A) Bipolar (B) Unipolar (C) Multipolar

16. Nerve Impulses
At rest, the inside of a neuron's membrane has a negative charge. As the figure shows, a Na+ / K+ pump in the cell membrane pumps sodium out of the cell and potassium into it. However,  more potassium ions leak out of the cell. As a result, the inside of the membrane builds up a net negative charge relative to the outside.
Animations of Nerve Impulses
view0/chapter14/animation __the_nerve_impulse.html
animations/actionpotential.swf

17. The Synapse Synapse - junction between two communicating neurons
Nerve pathway - nerve impulse travels from neuron to neuron
Synaptic Transmission Dendrite ->cell body -> along axon -> synapse (gap)
To complete the signal, a NEUROTRANSMITTER is released at the gap to signal the next neuron

18. Neurotransmitters
Excitatory - increase membrane permeability, increases chance for threshold to be achieved
Inhibitory - decrease membrane permeability, decrease chance for threshold to be achieved

19. Types of Neurotransmitters
Acetylcholine - stimulates muscle contraction
Monoamines - Norepinephrine & Dopamine (sense of feeling good, low levels = depression)
Serotonin (sleepiness)
Endorphins (reduce pain, inhibit receptors)

20. Antidepressants
Zoloft is part of a class of drugs called selective serotonin reuptake inhibitors, or
 SSRIs for short. SSRIs act on a specific chemical within the brain known as serotonin. This is one of several chemicals used to send messages from one nerve cell to another.

21. 9.8 Impulse Processing
Neuronal pool - groups of neurons that make hundreds of synaptic connections and work together to perform a common function
These "pools" help us remember sequential tasks, like tying a shoe or riding a bike.

22. 9.9 Types of Nerves
Sensory Nerves - conduct impulses into the brain or spinal cord
Motor Nerves - carry impulses to muscles of glands
Mixed Nerves - contain both sensory and motor nerves

23. 9.10 Nerve Pathways
Reflex arc - only includes a few neurons
Reflex Behavior - automatic, subconscious responses
Knee-jerk reflex - maintains uprightedness
Withdrawal reflex - avoidance of painful stimuli

24. Synapses are highly susceptible to drugs and fatigue
Curare (poison used by S. American Indians) and atropine stops Acetylcholine from depolarising the post-synaptic membrane, i.e. become paralysed.
Strychnine and some nerve gases inhibit or destroy acetylcholinesterase formation. Prolongs and enhances any stimulus, i.e. leads to convulsions, contraction of muscles upon the slightest stimulus.
Cocaine, morphine, alcohol, ether and chloroform anesthetize nerve fibers. (inhibitory)
Mescaline and LSD produce their hallucinatory effect by interfering with nor-adrenaline & serotonin

25. 9.10 Nerve Pathways
Reflex arc – simple pathway, includes only a few neurons (reflexes)
Reflex Behavior – automatic, subconscious responses to stimulu
Knee-jerk reflex – stimulus knee  sensory nerve  spinal cord  motor nerve

26. 9.12 Spinal Cord - nerve column, passes from brain down through the vertebral canal
- has 31 segments, each with a pair of spinal nerves

27. 9.13 Brain
Three Major Parts:
Cerebrum – largest, sensory and motor functions, higher mental function (memory, reasoning)
Cerebellum – coordinate voluntary muscles
Brain stem – regulate visceral functions