1. Nervous Tissue

2. The Nervous System Components Responsible for Subdivisions
Brain, spinal cord, nerves, sensory receptors
Responsible for
Sensory perceptions, mental activities, stimulating muscle movements, secretions of many glands
Subdivisions
Central nervous system (CNS)
Peripheral nervous system (PNS)

3. Functional Overview of NS
CNS
Integration, processing and coordination of sensory data and motor commands
Higher functions
PNS
Sensory or afferent division with sensory neurons. Brings sensory info to CNS. Begins as receptors, ends in?
Motor or efferent division with motor neurons. Brings motor commands to peripheral tissue. Ends at effector cells.

4. Central Nervous System
Consists of
Brain
Located in cranial vault of skull
Spinal cord
Located in vertebral canal
Brain and spinal cord
Continuous with each other at foramen magnum

5. Peripheral Nervous System

6. Peripheral Nervous System
Two subcategories
Sensory or afferent
Motor or efferent
Divisions
Somatic nervous system
Autonomic nervous system (ANS)
Sympathetic
Parasympathetic
Enteric

7. Nervous System Organization

8. Cells of Nervous System
Neurons or nerve cells
Receive stimuli and transmit action potentials
Organization
Cell body or soma
Dendrites: Input
Axons: Output
Neuroglia or glial cells
Support and protect neurons

9. Types of Neurons Functional classification Structural classification
Sensory or afferent: Action potentials toward CNS
Motor or efferent: Action potentials away from CNS
Interneurons or association neurons: Within CNS from one neuron to another
Structural classification
Multipolar, bipolar, unipolar

10. Neuroglia of CNS Astrocytes (star shaped glial cells) Ependymal Cells
Regulate extracellular brain fluid composition
Promote tight junctions to form blood-brain barrier
Ependymal Cells
Line brain ventricles and spinal cord central canal
Help form choroid plexuses that secrete CSF (cerebrospinal fluid)

11. Neuroglia of CNS Microglia Oligodendrocytes Specialized macrophages
Form myelin sheaths if surround axon

12. Neuroglia of PNS Schwann cells or neurolemmocytes Satellite cells
Wrap around portion of only one axon to form myelin sheath
Satellite cells
Surround neuron cell bodies in ganglia, provide support and nutrients

13. Myelinated and Unmyelinated Axons
Myelin protects and insulates axons from one another
Not continuous
Nodes of Ranvier
Unmyelinated axons
Action potentials in neurons lack myelin sheaths and travel slowly

14. Electrical Signals
Cells produce electrical signals called action potentials
Transfer of information from one part of body to another
Electrical properties result from ionic concentration differences across plasma membrane and permeability of membrane

15. Sodium-Potassium Exchange Pump

16. Ion Channels Nongated or leak channels Gated ion channels
Always open and responsible for permeability
Specific for one type of ion although not absolute
Gated ion channels
Ligand-gated
Open or close in response to ligand binding to receptor as ACh
Voltage-gated
Open or close in response to small voltage changes

17. Resting Membrane Potential
Characteristics
Number of charged molecules and ions inside and outside cell nearly equal
Concentration of K+ higher inside than outside cell, Na+ higher outside than inside
At equilibrium there is very little movement of K+ or other ions across plasma membrane

18. The Synapse Junction between two cells
Site where action potentials in one cell cause action potentials in another cell
Types
Presynaptic
Postsynaptic

19. Synapse
Site of communication between two nerve cells or nerve cell and effector cell
neuro-effector junctions
Electrical vs. chemical synapses

20. Chemical Synapse vs. Electrical Synapse
Space between two cells
Signal transduction via NT
Most common
Direct physical contact between cells = gap junctions
Direct signal transduction
Rare, but occurs in CNS and heart

21. Chemical Synapses Components
Presynaptic terminal
Synaptic cleft
Postsynaptic membrane
Neurotransmitters released by action potentials in presynaptic terminal
Synaptic vesicles
Diffusion
Neurotransmitter removal

22. Anatomical Organizatin of NS
Collections of cell bodies - ganglion in PNS, center or nucleus in CNS
Bundles of axons - tracts in CNS, nerves in PNS
“White” = myelinated axons, both nerves and tracts
“Gray” = non-myelinated material, dendrites, synapses and cell bodies as well as nonmyelinated axons. In CNS – nucleus; in PNS - ganglia
The End