1. Introduction to the Nervous System
to be copied

2. Nervous Tissue & Homeostasis
excitable characteristic of nervous tissue allows for generation of nerve impulses (action potentials) that provide communication & regulation of most body tissue.
together with endocrine system: responsible for maintaining homeostasis

3. Differences in Nervous & Endocrine Control of Homeostasis
rapid responder
action potentials
slow, prolonged response
releases hormones

4. Structures of the Nervous System
total mass of 2 kg (~3% of total body mass)
Skull
Spinal Cord
Spinal Nerves
Cranial Nerves
Ganglia
Enteric Plexus
Special Senses & other Sensory Receptors

5. Functions of the Nervous System
3 basic functions:
Sensory
Integrative
Motor

6. Sensory Function sensory receptors detect internal & external stimuli
sensory (afferent) neurons carry this sensory information to spinal cord & brain thru cranial & spinal nerves

7. Integrative Function integrate: process
nervous system takes information from sensory neurons & processes that information, analyzes it, stores some of it & makes decisions for appropriate responses
served by interneurons (connect 1 neuron to another neuron
Perception:
conscious awareness of sensory stimuli
occurs in brain

8. Motor Function served by motor (efferent) neurons
carry info from brain/spinal cord  effectors (muscle or gland) thru cranial or spinal nerves
results in muscles contraction or gland secreting

9. Organization of the Nervous System

10. Histology of the Nerrvous System
2 cell types
Neurons
Neuroglia

11. Neurons nerve cells that possess electrical excitability:
ability to respond to a stimulus & convert it into an action potential
stimulus: any change in environment that is strong enough to initiate an action potential

12. Action Potential
electrical signal that propagates along surface of neurolema (membrane)
begins & travels due to movement of ions between interstitial fluid & inside of neuron thru specific ion channels
once begun it travels constant strength

13. Parts of a Neuron

14. 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

15. Nerve Fiber
general term for any neuronal process or extension that emerges from cell body
most neurons have 2:
Dendrites
Axons

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

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

18. 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

20. 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

21. 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

22. Axonal Transport 2 types: slow fast
for moving materials from cell body  axon terminals
slow
1-5 mm/d
replenishes new axoplasm to developing or regenerating axons
fast
200 – 400 mm/d
moves materials to/from cell body
organelles or membranes needed in axon terminal

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

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

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

26. 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

27. Unipolar Neuron

28. Pyramidal Cells
in cerebral cortex of brain

29. 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

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

31. 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

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

33. 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

34. 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

35. Neuroglial Cells of the PNS
Schwann cells
Satellite cells

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

37. 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

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

39. Myelinated & Unmyelinated Axons

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

41. 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

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

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

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