1. The Nervous System
Overview

3. sensory input - monitors changes outside and inside the body

4. integration - processes and interprets input and makes decision

5. motor output - effects a response from either a muscle or a gland

6. Basic Functions:
sensory input - monitors changes outside and inside the body
integration - processes and interprets input and makes decision
motor output - effects a response from either a muscle or a gland

7. Divisions of the Nervous System
Central (CNS) - brain and spinal cord
integrating and command centers
Peripheral (PNS) - nerves outside of CNS

11. Histology of Nervous Tissue

12. Nervous Tissue: Support Cells
collectively called neuroglia (nerve glue)
supporting cells
assist, segregate, and insulate neurons
9 times more numerous than neurons

14. 1. astrocytes control ionic environment
attach neurons to capillaries (nutrients)
1. astrocytes

15. 2. microglia
type of macrophage
engulf microorganisms

16. 3. ependymal
form cerebrospinal fluid (CSF)

17. 4. oligodendrocytes
form myelin sheath
insulates nerve fibers

18. 5. Schwann cells
form myelin sheath
act as phagocytes
insulates

19. 6. satellite cells
control chemical environment

20. Types of Glia Cells
astrocytes - control ionic environment, attach neurons to caps. (nutrients)
microglia - type of macrophage, engulf microorganisms
ependymal - form cerebrospinal fluid (CSF)
oligodendrocytes - form myelin sheath, insulates nerve fibers
Schwann cells - form myelin sheath, act as phagocytes, insulates
satellite cells - controlling chemical environment

21. The Neuron

23. Neuron Structure able to generate and conduct nerve impulse
can live and function for a lifetime - amitotic
cell body - large nucleus and nucleolus
rough ER in form of Nissl bodies

24. processes - cytoplasmic extensions (extend from cell body)
1. dendrites - short, branched
conduct impulses toward cell body

25. 2. axon - only 1
may have side branches
ends in terminals or synaptic bulbs which release neurotransmitters
conduct impulses away from cell body

26. insulated by myelin sheath
made of Schwann cells (wrap around)

27. adjacent Schwann cells don’t touch gaps are Nodes of Ranvier
increase speed of transmission
Node of Ranvier
Myelin sheath
Schwann Cell

29. Formation of Myelin Sheath
As the Schwann cells wrap around the axon, the myelin sheath forms.
The neurilemma is the outer most part of the myelin sheath with the majority of the cytoplasm and nuclei.
innermost is called the myelin sheath

30. White matter is a collection of myelinated fibers.
Gray matter is unmyelinated with only a single layer of Schwann cells. Gray matter is slow and found where distances are short.

31. Neuron Classification According To Structure
number of processes extending from the cell body

32. 1. Multipolar
many dendrites
1 axon
1 cell body
most common

33. 2. Bipolar
1 axon
1 dendrite
1 cell body
rare
ex: olfactory and retina

34. 3. Unipolar single process that merges with cell body sensory neurons
ex: skin

35. Neuron Classification According To Function
direction of impulse conduction

37. away from CNS, to muscle or glands, most multipolar
sensory / afferent –
toward CNS, from skin or internal organs
motor / efferent –
away from CNS, to muscle or glands, most multipolar
association neurons / interneurons –
lie between sensory and motor neurons, shuttle signals

39. Nerves
Nerves are cord like bundles of nerve fibers wrapped by connective tissue.
Blood and lymph vessels are also found inside.
Nerves are only found in the PNS.

40. Types of Nerves ** most nerves sensory nerves - (afferent) toward CNS
motor nerves - (efferent) away from CNS
mixed nerves –
both sensory (afferent) and motor (efferent) nerves, to and from CNS
** most nerves

41. Regeneration of Nervous Tissue
mature neurons do not undergo mitosis
if damage is severe or close to cell body, neuron may die
however, cut or compressed axons can regenerate in the PNS

47. Regeneration of Nervous Tissue
Damage area is reabsorbed
Neurilemma of Schwann cells form a tunnel to guide axonal “sprouts” to their original contacts. Schwann cells also releases growth factor.
The grater the distance, the less chance of nerve recovery.
Neurosurgeons align cut nerve endings surgically to enhance regeneration.
Post trauma regrowth is never exactly the same.

48. Regeneration of Nervous Tissue
CNS cells never regenerate (lack neurilemma)
supporting neuroglial cells provide no guiding tunnel and scaring blocks axon sprouts