1. Nervous System: General Principles
Comparative Anatomy
Tony Serino. Ph.D.
Biology Dept.
Misericordia Univ.

2. Nervous System Controls and/or modifies all other systems
Rapid response time
Usually short duration
Reflex arc illustrates functional control

3. Divisions of the Nervous System

4. Nervous Tissue Non-excitable Tissue (Supportive cells)
Neuroglia –present in CNS
Schwann and Satellite cells –present in PNS
Neurons (excitable tissue)
Initiate and conduct electrical signals (action potentials)

5. Neuroglia (glial cells)
Phagocytic,protective
Form BBB
Regulate microenvironment
Pass on nutrients; get rid of waste

6. Neuroglia
Line cavities
Create CSF
Secrete myelin in CNS

7. PNS Supportive Cells Schwann cells –secrete myelin in PNS
Satellite cells –surround neuron cell bodies in PNS

8. Neuron Anatomy Axonal terminal Nerve ending Synaptic boutons
Synaptic knobs

9. Functional Zones of a Neuron
Receptor Zone
Initial segment of Axon (trigger zone)
Nerve endings
Axon

10. Internal Cell Body Structures

11. Myelination
In PNS, a Schwann cell wraps and individual segment of a single axon
In the CNS, an oligodendrocyte performs the same function but can attach to more than one axon

12. Node of Ranvier: gaps in myelin sheath

13. Types of Neurons Anatomical classification Functional Classification
Based on number of process projecting from cell body
Functional Classification
Based on location of neuron and direction of information flow

16. Functional Classes

17. General Terms Ganglia vs. Nuclei Nerve vs. nerve fiber
Areas of densely packed nerve cell bodies
Ganglia are usually found in PNS
Nuclei are found in CNS
Nerve vs. nerve fiber
A nerve is a dissectible structure containing hundreds of axons
A nerve fiber is a single axon
CT sheaths covering peripheral nerves:

18. Nerve CT sheaths

19. Synapses Areas where neurons communicate with other cells
Can be chemical (with neurotransmitters) or electrical (gap junctions)

20. Anatomy of Synapse (chemical)
Neurotransmission ends when NT diffuses away,
re-absorbed by presynaptic neuron, or NT metabolized
(degraded) by enzymes in cleft

21. Neurotransmission
Electrical signal (action potential (AP)) descends axon to synaptic knob (nerve end)
Depolarization opens Ca++ channels to open in presynaptic membrane
Triggers a number of synaptic vesicles to fuse with outer membrane
Dumps neurotransmitter (NT) into synaptic cleft
NT diffuses across cleft and binds to receptor on postsynaptic membrane
This leads to channels opening on postsynaptic membrane changing the membrane’s potential