1. The Nervous System
Nervous Tissue

2. Neurology
The study of the nervous system

3. Functions of the Nervous System
Sensory – Senses changes in the body
Integrative – Analyzes sensory information, stores some of it and determines behavior based on the information
Motor – Responds to the stimuli by initiating action

4. Organization of the Nervous System
Central Nervous System (CNS) - Composed of the brain and spinal cord
Responsible for:
i. Incoming sensory Information
ii. Thoughts and emotions
iii. Memories
iv. Generating Nerve Impulses

5. Organization of the Nervous System
Peripheral Nervous System (PNS) – Composed of Cranial Nerves and Spinal Nerves
Responsible For:
i. Sensory (Afferent) – input
ii. Motor (Efferent) – output

6. Organization of the Nervous System
Peripheral Nervous System (continued)
iii. Somatic Nervous System (SNS) – voluntary
iv. Autonomic Nervous System (ANS) – involuntary
1. Sympathetic vs. Parasympathetic

7. Sympathetic vs. Parasympathetic
2 branches of the ANS that usually have opposing actions
Ex – sympathetic speeds up the heart while parasympathetic slows it down

8. Organization if the Nervous System
PNS
CNS
SNS
ANS
sympathetic
parasympathetic

9. Histology of the Nervous System
Cells
Neuroglia (glia or glial cells) – used for support and protection
Astrocytes
Oligodentrites
Microglia
Ependymal Cells
Schwann Cells
Satellite Cells

10. Histology of the Nervous System
Cells
Neurons
“nerve cell”
Conducts impulses from one part of the body to another

11. Neurons
Cell Body – contains the nucleus and nucleolus, cytoplasm and typical cellular organelles
Dendrites – Short thick branched extensions used to receive impulses and send them to the cell body
Axon – Single long thin extension that sends impulses to another neuron or tissue
Synaptic End Bulb – Structure at the end of an axon that store neurotransmitters

12. Typical Neuron

13. Myelin Sheath
Fat and protein covering that insulates the axon to increase the speed of a nerve impulse

14. Myelinated – with myelin
Unmyelinated – without myelin
Schwann Cells – glial cells wrapped around the axon that form the myelin sheath.
Nodes of Ranvier – gaps in the myelin scheath

16. Gray and White Matter
White Matter – contains both myelinated and unmyelinated axons
Found in outer sections of the spinal cord and inner portion of the brain
Gray Matter – contains only unmyelinated axons
Found in an “H” shape in the middle of the spinal cord and the outer covering of the brain

17. .

18. Action Potentials – “Nerve Impulse”
Membrane Potential – difference in the amount of electrical charge between the outside and inside of the plasma membrane
Ion Channel – openings in the plasma membrane through which ions flow

20. Action Potential
The sequence of events that decrease and reverse the resting membrane potential then return it to normal

22. Threshold – a critical level that once reached will cause a nerve impulse
Depolarizing Phase – decreasing and reversing a membrane potential (making it more positive on the inside than on the outside)
Repolarizing Phase – the membrane potential is returned to its resting state

24. Sodium-Potassium Pump Na+/K+ pump
First, Na ions rush into the cell causing the cell to BECOME MORE POSITIVE ON THE INSIDE; then K ions move out of the cell causing it to return to its resting membrane potential

26. All or None Principle…
As long as the threshold is reached, the channels will open and an action potential will occur along the ENTIRE nerve. A stronger stimulus does not cause a stronger impulse..
(it’s just like the muscle cells guys)

27. Conduction of a nerve impulse
Positive Feedback Mechanism – When the first Na channels open it causes an inflow of Na ions that depolarize the next portion of membrane to threshold, which causes another Na channel to open which causes another depolarization which causes another Na channel to open which causes…

28. Continuous Conduction
Each patch of the axon depolarizes and causes the next patch to depolarize. Found on unmyelinated axons and is relatively slow.

29. Saltatory Conduction
Na/K channels only open at the nodes of Ranvier, then the current travels under the myelin sheath to the next node.
Only in myelinated axons, faster than continuous

31. Speed of Impulse… Myelination: Diameter of Nerve: Temperature
Myelination = faster
Diameter of Nerve:
Wider = faster
Temperature
Warmer = faster

32. Synapses – space between neuron
Synaptic Cleft – tiny space filled with interstitial fluid
Ca ions from the interstitial fluid flow into the synaptic end bulb causing the neuron to release neurotransmitters.

33. Common Neurotransmitters

34. Acetylcholine (ACh)
Used at neuromuscular junctions

35. Glutamate and Aspartate
Amino Acids that have an excitatory effect on the CNS

36. GABA and Glycine Inhibitory Neurotransmitters
Anti-anxiety drugs often enhance these neurotransmitters

37. Norepinephrine
Functions in awakening, dreaming and mood

38. Dopamine (DA) Active during emotional response and addictive behavior
Cocaine blocks the re-uptake of dopamine allowing it to stay in the synaptic cleft longer and prolonging pleasurable feelings

40. Endorphins Natural Pain Killers
Endorphins interact with the opiate receptors in the brain to reduce our perception of pain and act similarly to drugs such as morphine and codeine. In contrast to the opiate drugs, however, activation of the opiate receptors by the body's endorphins does not lead to addiction or dependence.

41. Nitric Acid
Functions in learning and memory

42. NERVOUS SYSTEM DISORDERS

43. Multiple Sclerosis (MS)
Progressive destruction of the myelin sheath on the axons.

44. Epilepsy
Seizure disorder

45. Guillain-Barre Syndrome
Macrophages “eat” the myelin sheath on the axons and cause sudden paralysis
Patients usually recover at least partially