1. Part I - Nervous System Overview

2. Chapter 7 Vocabulary nervous system central nervous system (CNS)
peripheral nervous system (PNS)
sensory (afferent) division
motor (efferent) division
somatic nervous system (voluntary)
autonomic nervous system (involuntary)
Schwann cells
satellite cells
neurons (nerve cells)
cell body
dendrites
axons
neurotransmitters
synapse
myelin sheath
multiple schlerosis (MS)
neuroglia (glia) cells
ganglia
tracts
white matter
gray matter
propriocepter
afferent (sensory) neurons
efferent (motor) neurons
interneurons (association neuron)
reflex arc
somatic reflexes
autonomic reflexes
nerve

3. A. Functions of the Nervous System
1. Sensory input
To monitor changes (stimuli) occurring inside and outside the body (sensory receptors)
2. Integration
To process and interpret sensory input and decide if action is needed
3. Motor output
A response to stimuli by activating muscles or glands (effectors)

4. B. Two Major Subdivisions of the Nervous System
1. Central nervous system (CNS)
a) Brain
b) Spinal cord
2. Peripheral nervous system (PNS)
a) Nerve outside the brain and spinal cord including:
b) cranial nerves
c) spinal nerves

5. Functional Classification of the Peripheral Nervous System
Sensory (afferent) division
Nerve fibers that carry information to the central nervous system
Figure 7.1

6. Functional Classification of the Peripheral Nervous System
Motor (efferent) division
Nerve fibers that carry impulses away from the central nervous system
Figure 7.1

7. Functional Classification of the Peripheral Nervous System
Motor (efferent) division
Two subdivisions
Somatic nervous system = voluntary
Autonomic nervous system = involuntary
Figure 7.1

8. C. Divisions of the Peripheral Nervous System
1. Sensory (afferent) division
a) sense organs – cutaneous (skin), eyes, taste buds, etc
b) proprioceptors - in muscles
2) Motor (efferent) division
a) somatic nervous system= voluntary – skeletal muscle and reflexes
b) autonomic nervous system (ANS)= involuntary – glands, heart, smooth muscle and some reflexes

9. Organization of the Nervous System
Figure 7.2

10. Types of Nervous Tissue: Neuroglia
D. Neuroglia “nerve glue”
Supporting cells
mitotic – actively dividing
1. CNS glia – responsible for most brain tumors (gliomas)
2. PNS glia
a) Schwann cells – insulate with myelin sheath
b) satellite cells – protect and cushion

11. Nervous Tissue: Support Cells (Neuroglia)
Astrocytes
Abundant, star-shaped cells
Brace neurons
Form barrier between capillaries and neurons
Control the chemical environment of the brain
Figure 7.3a

12. Nervous Tissue: Support Cells
Microglia
Spider-like phagocytes
Dispose of debris
Ependymal cells
Line cavities of the brain and spinal cord
Circulate cerebrospinal fluid
Figure 7.3b–c

13. Nervous Tissue: Support Cells
Oligodendrocytes
Produce myelin sheath around nerve fibers in the central nervous system
Figure 7.3d

14. Nervous Tissue: PNS Support Cells
a) Schwann cells
Form myelin sheath in the peripheral nervous system
b) Satellite cells
Protect neuron cell bodies
Figure 7.3e

15. Types of Nervous Tissue: Neurons
E. Neurons = nerve cells
1. Amitotic – cannot divide
2. Cells specialized to transmit messages
3. Major regions of neurons
a) Cell body – nucleus and metabolic center of the cell
b) Dendrite – conduct impulses toward the cell body
c) Axon - conduct impulses away from the cell body

16. Neuron Anatomy Cell body
Nissl substance – specialized rough endoplasmic reticulum
Neurofibrils – intermediate cytoskeleton that maintains cell shape
Figure 7.4a

17. Neuron Anatomy
Cell body
Nucleus
Large nucleolus
Figure 7.4a–b

18. Neuron Anatomy Extensions outside the cell body
Dendrites – conduct impulses toward the cell body
Axons – conduct impulses away from the cell body
Figure 7.4a

19. Axons and Nerve Impulses
Axons end in axonal terminals
Axonal terminals contain vesicles with neurotransmitters
Axonal terminals are separated from the next neuron by a gap
Synaptic cleft – gap between adjacent neurons
Synapse – junction between nerves

20. Nerve Fiber Coverings
Schwann cells – produce myelin sheaths in jelly-roll like fashion
Nodes of Ranvier – gaps in myelin sheath along the axon
Multiple sclerosis (MS) is an autoimmune neurological disease where myelin sheaths are gradually destroyed. This short-circuits neurons and the affected person loses the ability to control his or her muscles
Figure 7.5

21. Neuron Cell Body Location
Most are found in the central nervous system
Gray matter – cell bodies and unmyelinated fibers
Nuclei – clusters of cell bodies within the white matter of the central nervous system
Ganglia – collections of cell bodies outside the central nervous system

22. Nerve Fiber (neuron processes) Location
Nerves – bundles of nerve fibers (neurons processes) in the PNS
Tracts – bundles of nerve fibers (neuron processes) running through the CNS
White Matter – consists of dense collections of myelinated fibers (tracts) in the CNS
Gray Matter – contains mostly unmyelinated fibers and cell bodies in the CNS

23. F. Functional Classification of Neurons
1. Sensory (afferent) neurons
Carry impulses to CNS from the sensory receptors such as:
Cutaneous sense organs
Proprioceptors – detect stretch or tension
2. Motor (efferent) neurons
Carry impulses from the CNS to effectors (muscles, glands)

24. Functional Classification of Neurons
3. Interneurons (association neurons)
Found in neural pathways in the central nervous system
Connect sensory and motor neurons

25. G. Sensory Receptors
1. Special sense organs - found in eyes, ears, nose and mouth
2. Cutaneous sense organs – found in skin
a) naked nerve endings (pain and temperature receptors)
b) Meissner’s corpuscles (light touch receptor)
c) Pacinian corpuscles (deep pressure receptor)
3. Proprioceptor – receptor found in muscle and tendons
a) Golgi tendon organ
b) muscle spindle

26. (pain and temperature receptors Meissner’s corpuscle (touch receptor)
Naked nerve endings
(pain and temperature receptors
Meissner’s corpuscle (touch receptor)
Golgi tendon organ (proprioceptor)
Pacinian corpuscle (deep pressure receptor)
Muscle spindle (proprioceptor)

27. Neuron Classification
Figure 7.6

28. H. Structural Classification of Neurons
1. Multipolar neurons – many extensions from the cell body
Figure 7.8a

29. H. Structural Classification of Neurons
2. Bipolar neurons – one axon and one dendrite
Figure 7.8b

30. H. Structural Classification of Neurons
3. Unipolar neurons – have a short single process leaving the cell body
Figure 7.8c

31. Name each type of neuron:
multipolar neuron
bipolar neuron
unipolar neuron

32. Functional Properties of Neurons
Irritability – ability to respond to stimuli
Conductivity – ability to transmit an impulse
The plasma membrane at rest is polarized
Fewer positive ions are inside the cell than outside the cell

33. Starting a Nerve Impulse
Depolarization – a stimulus depolarizes the neuron’s membrane
A depolarized membrane allows sodium (Na+) to flow inside the membrane
The exchange of ions initiates an action potential in the neuron
Figure 7.9a–c

34. The Action Potential
If the action potential (nerve impulse) starts, it is propagated over the entire axon
Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane
The sodium-potassium pump restores the original configuration
This action requires ATP

35. Nerve Impulse Propagation
The impulse continues to move toward the cell body
Impulses travel faster when fibers have a myelin sheath
Figure 7.9d–f

36. Continuation of the Nerve Impulse between Neurons
Impulses are able to cross the synapse to another nerve
Neurotransmitter is released from a nerve’s axon terminal
The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter
An action potential is started in the dendrite

37. How Neurons Communicate at Synapses
Figure 7.10

38. The Reflex Arc
Reflex – rapid, predictable, and involuntary responses to stimuli
Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector
Figure 7.11a

39. Simple Reflex Arc
Figure 7.11b–c

40. I. Types of Reflexes
1. Somatic reflexes- activation of skeletal muscle
Flexor reflex – withdraw from painful stimulus
Patellar (knee-jerk) reflex
2. Autonomic reflexes- smooth muscle, glands, heart
salivary reflex
pupillary reflex – eye pupils changing
blood pressure, digestion, sweating