1. Fundamentals of the Nervous System
HONORS ANATOMY & PHYSIOLOGY
CHAPTER 11

2. Functions of the Nervous System
3 overlapping functions:
Sensory input
monitor changes in & outside of body
information gathered called sensory input which is carried to #2 on afferent nerves
Integration
processing & interpreting sensory input
Motor output
activation of effector organs (muscles or glands) to cause a response called motor output which is carried on efferent nerrves

3. Divisions of the Nervous System
Central Nervous System(CNS)
Brain
Spinal Cord
Peripheral Nervous System (PNS)
Sensory neurons: specialized endings to detect a particular sense
Motor neurons:
Somatic: CNS  skeletal muscle (voluntary)
Autonomic:
Sympathetic
Parasympatheric

4. Organization of the Nervous System

5. Histology of Nervous Tissue
very cellular, ~20% extracellular material
2 cell types:
Neurons
excitable (respond to stimuli)
able to transmit electrical impulses (action potentials)
Neuroglia:
supporting cells

7. Parts of Neuron: Cell Body
contains nucleus, cytoplasm, typical organelles,
+ Nissl bodies clusters of RER
make materials for:
growth of neuron
regenerate damaged axons in PNS

8. Dendrites “little trees” input portion of neuron
usually, short, tapering, highly branched
their cytoplasm contains Nissl bodies, mitochondria

9. Axon another neuron muscle fiber gland cell
propagates action potentials 
another neuron
muscle fiber
gland cell

10. Parts of an Axon joins cell body @ cone-shaped elevation: axon hillock
part of axon closest to hillock = initial segment
jct of axon hillock & initial segment where action potential arises so is called the trigger zone

11. Parts of an Axon axoplasm: cytoplasm of an axon
axolemma: plasma membrane of axon
axon collaterals: side branches along length of axon 90°)
axon terminals: axon divides into many fine processes

12. Synapse
site of communication between 2 neurons or between a neuron & effector cell
synaptic end bulbs: tips of some axon terminals swell into bulb-shaped structures
synaptic vesicles: store neurotransmitter
many neurons have >1 neurotransmitter, each with different effects on postsynaptic cell

14. Types of Neurons Functional Classification Structural Classification
Sensory
Interneurons
Motor
use # processes extending from cell body
Multipolar neurons
Bipolar neurons
Unipolar neurons

15. Multipolar Neurons several dendrites with 1 axon
includes most neurons in brain & spinal cord

16. Bipolar Neuron 1 main dendrite & 1 axon
retina, inner ear, olfactory area of brain

17. Unipolar Neuron are sensory neurons that begin in embryo as bipolar
during development axon & dendrite fuse then divide into 2 branches (both have characteristic structure & function of an axon)
1 branch ends with dendrites (out of CNS)
2nd branch ends in axon terminal (in CNS)
cell bodies of most found in ganglia

18. Unipolar Neuron

19. Purkinje Cells
found in cerebellum

20. Pyramidal Cells
in cerebral cortex of brain

21. Neuroglia (Glia) ~50% vol of CNS “glue”
do not generate or propagate action potentials
multiply & divide in mature nervous systems
glioma:
brain tumors derived from glial cells
very malignant, grow rapidly

22. Glial Cells of the CNS ASTROCYTES OLIGODENDROCYTES MICROGLIA
EPENDYMAL CELLS

23. Astrocytes star-shaped largest & most numerous of glial cells
functions:
physically support neurons
assist in blood-brain-barrier (bbb)
in embryo: regulate growth, migration, & interconnections between neurons
help maintain appropriate chemical environment for propagation of action potentials

25. Oligodendrocytes “few trees” smaller & fewer branches than astrocytes
Functions:
form & maintain myelin sheath on axons in CNS
1 oligo. myelinates many axons

26. Microglia
small cells with slender processes giving off many spine-like projections
function:
phagocytes
remove cellular debris made during normal development
remove microbes & damaged nervous tissue

27. Ependymal Cells single layer of cuboidal to columnar cells
ciliated & have microvilli
function:
line ventricles of brain & central canal of spinal cord
produce, monitor, & assist in circulation of cerebrospinal fluid (CSF)
form bbb

29. Neuroglial Cells of the PNS
Schwann cells
Satellite cells

30. Schwann Cells functions: myelinate axons in PNS
1 Schwann cell myelinates 1 axon
participate in axon regeneration

31. Satellite Cells
flat cells that surround cell bodies of neurons in PNS ganglia
functions:
structural support
regulate exchange of materials between neuronal cell bodies & interstitial fluid

32. Myelination
myelin sheath: made up of multilayered lipid & protein (plasma membrane) covering
function:
electrically insulates axon
increases speed of nerve impulses

33. Myelinated & Unmyelinated Axons

35. Nodes of Ranvier gaps in myelin sheath
1 Schwann cell wraps axon between nodes of Ranvier

36. Myelin amount increases from birth to maturity
infant‘s responses slower & less coordinated as older child or adult in part because myelination is a work in progress thru infancy

38. Demyelination loss of myelin sheath see in disorders:
multiple sclerosis
Tay-Sachs
side effect of radiation therapy & chemotherapy

39. Gray Matter of the Nervous System
contains:
neuronal cell bodies
dendrites
unmyelinated axons
axon terminals
neuroglia

40. White Matter of the Nervous System
composed of:
myelinated axons