1. Nervous System

2. Nervous System Design 2 main section Central Nervous System
Peripheral Nervous System

3. Central Nervous System (CNS) brain and spinal cord.
encased in skull and vertebral column to protect them

4. Peripheral Nervous System (PNS)
All of the nerves going to and from the central nervous system

5. Peripheral Nervous System (PNS)
Sensory fibers info from the body to the central nervous system 
General senses spread around the body 
Special senses  special sensory organs.

6. motor fibers deliver information from the central nervous system to the body. somatic nervous system skeletal muscles motor neurons .

7. Autonomic Nervous System smooth muscle, cardiac muscle, and glands
Autonomic Nervous System smooth muscle, cardiac muscle, and glands. Homeostasis
sympathetic (alert, fight of flight) and parasympathetic (relaxed, rest and digest) nervous systems balance with each other

8. Neuron Neurons -the cells which can send electrical impulses
Most of the neurons are found in the central nervous system.

9. Neuron
Cell Body- contains the nucleus and most of the cell's organelles

10. Neuron
The neuron lacks one organelle which other body cells have, the centriole.  The centriole allows the cell to reproduce.  As a result, neurons are unable to multiply to replace any neurons that are lost or damaged.

11. Neuron nerve fibers transmit electrical impulses. 2 types
dendrites and axons.

12. Neuron Axon impulses away from the cell body.
Message to the body for action
only one axon associated with each neuron. 
end of the axon may be split
Each end enlarged terminal bulb.
Terminal bulb releases neurotransmitters- chemicals that tell the other cell what to do.

13. Neuron Dendrites impulses towards the cell body of the neuron.
Many per neuron
Info sent from nerve receptors.  

14. Neurons
3 basic types
Number of dentrites varies

15. Multipolar neurons- single axon and many dendrites
Multipolar neurons- single axon and many dendrites. Most common type of neuron in the CNS.

16. Bipolar neurons have one axon and one dendrite,
Generally opposite sides. 
typically found in the special sense organs (e.g. the eye, ear, and nose).

17. Unipolar neurons have a single fiber which exits the cell body then splits into two parts.  One part serves as the axon while the other part serves as the dendrite. 
The central stalk is used for impulses going in either direction (to or from the cell body).

18. Neuroglia
Neuroglia support cells of the nervous system.

19. Microglia small, phagocytic . brain's microbial defense mechanism.
consume bacteria and viruses that enter the brain tissue
clean up damaged tissue too.    

20. Astrocytes blood/brain barrier.
Materials moving from the blood to the neurons must first pass through the astrocyte. 
Toxic material will not be passed to neurons
Will die to protect neuron if need be

21. Ependymal cells form cerebrospinal fluid (fluid is shock absorber)
fluid is formed within chambers in the interior of the brain tissue. 

23. Ependymal cells
flows through several tunnels until it reaches the outside of the brain and spinal cord tissues. 
Continuously made and reabsorbed

24. Schwann cells and the Oligodendroglia.
form the myelin sheath around some of the nerve fibers (axons or dendrites). 

25. insulating wrapper that covers large areas of a nerve fiber.
Myelin Sheath
insulating wrapper that covers large areas of a nerve fiber. 
wrap in a jelly-roll fashion around the nerve fiber. 
Many line up end to end down a neuron fiber

26. Oligodendroglia form myelin in the CNS
Schwann cell form myelin in the PNS
myelinated fiber has myeline
unmyelinated fiber no myeline

27. Nodes of Ranvier. small spaces between the cells

28. Myelinated fibers send impulses more rapidly

29. At birth, the myelin sheath is just beginning to form
At birth, the myelin sheath is just beginning to form.  By age two, most of the myelin sheath is in place

30. Multiple Sclerosis (MS), the myelin sheath is slowly deteriorating.
Devastating effect on body function
Possibly autoimmune 

31. Sending an Electrical Signal
Neuron At Rest
Unequal ions on sides of membrane at rest
Excessive sodium (Na) ions (+) outside of the nerve fiber
Few Na+ inside
membrane is not permeable to Na+. 
Also excessive proteins on inside of membrane
Membrane is very negative on inside
Sending an Electrical Signal
See hand out 

32. Types of Impulse Transmission
Impulse can go towards nerve body or away
dendrite or axon

33. Types of Impulse Transmission
Continuous Conduction
occurs in unmyelinated fibers.
very slow because each segment of the nerve fiber must be depolarized. 
Long fibers (like 3 ft) takes as long as ½ a second

34. Types of Impulse Transmission
 Saltatory Conduction
Myelinated fiber transmission.
extremely rapid
about 1/60 the time for the same length of unmyelinated fiber

35. Types of Impulse Transmission
 Saltatory Conduction
only the exposed fiber at the nodes of Ranvier needs to be depolarized. 
Signal skips from node to node. 

36. Synapse Synapse- a junction between a neuron and another cell.
Cell could be another neuron or a body cell. 
neuron does not actually come in contact with the other cell. 

37. Synapse Synaptic Gap or Cleft- between the two cells.
Axon terminal
Vesicles
Synaptic cleft
Action potential arrives
Synapse
Axon of transmitting neuron
Receiving neuron
Synaptic Gap or Cleft- between the two cells. 
neurotransmitters- chemical messengers between the gaps
released by the terminal bulb of the neuron
bind to receptors located on the membrane of the other cell

38. Neurotransmitters Acetylcholine PNS / some CNS
Axon terminal
Vesicles
Synaptic cleft
Action potential arrives
Synapse
Axon of transmitting neuron
Receiving neuron
Vesicle fuses with plasma membrane
Ion channels
Transmitting neuron
Acetylcholine 
PNS / some CNS
Used to stimulate skeletal muscles and visceral smooth muscle

39. Neurotransmitters Acetylcholine
Inhibits cardiac muscle and multiunit smooth muscle
Stimulates secretions from most glands
and stimulates impulse transmission in other neurons.

40. Neurotransmitters Norepinephrine PNS / some CNS
stimulates contraction of cardiac and multiunit smooth muscle

41. Neurotransmitters Norepinephrine
Inhibits contraction of visceral smooth muscle. 
No effect on skeletal muscle. 
Inhibits secretion by most glands and inhibits impulse transmission in other neurons.

42. Neurotransmitters Dopamine and GABA (gamma amino butyric acid) CNS
inhibit impulses to neurons controlling certain muscle movements.  

43. Neurotransmitters Endorphins and Enkephalins CNS
block, or inhibit, transmission of pain impulses. 
Hundreds of times more powerful than morphine

44. Neural Networks
Neural networks - formed when several neurons link together to form a pathway. 
critical to the functioning of the body. 
different types of neural networks. examples:
divergent circuit, a single neuron sends impulses to several other neurons.  This allows information to be disseminated to many areas simultaneously to allow a coordination of activities.
convergent circuit, several neurons send information to a single neuron.  This type of circuit will allow information from a number of sources to be processed in one central location.
reverberating circuit cycles the impulse back through the neural network.  This continues to restimulate the neurons near the beginning of the neural network and keeps the information cycling through the network.  This type of circuit is involved in short-term memory.