2. Overview of the Nervous System
Chapter 6: The Nervous System
Lesson 6.1
Overview of the Nervous System

3. Organization of the Nervous System
Our nervous system has the ability to simultaneously direct multiple functions taking place in in our bodies.
Two major divisions:
Central nervous system (CNS). It directs the activity of the entire nervous system.
Brain
Spinal cord

4. Peripheral nervous system (PNS).
Sensory receptors: respond to stimuli such as pain
Afferent (sensory) nerves: transmit impulses from the sensory receptors in the skin, muscles & joints.
Efferent (motor) nerves: carry impulses from the CNS to the muscles and glands

5. Human Brain

6. Sheep Brain

8. Spinal Cord w/Brain

9. Two Major Divisions

10. The Efferent Nerves
There are two functional subdivisions of the efferent, or motor, nerves:
Somatic nervous system (voluntary)
Stimulates our skeletal muscles, causing them to develop tension.
Autonomic nervous system (involuntary)
Controls the cardiac muscle of the heart and the smooth muscles of the internal organs.
Sympathetic
Parasympathetic

11. Nervous Tissues
Two categories of tissues exist within the nervous system:
Neuroglia (glial cells)
These are specialized cells that perform support functions within the CNS.
Astrocytes
Link the nutrient-supplying capillaries to neurons and control the chemical environment to protect the neurons from any harmful substances in the blood.

12. Nervous Tissues Microglia
Absorb and dispose of dead cells and bacteria
Ependymal cells
Form a protective covering around the spinal cord and central cavities within the brain.
Oligodendrocytes
Wrap around nerve fibers and produce a fatty insulating material called myelin.

14. Neuroglia Peripheral nervous system Schwann cells
Form the fatty myelin sheaths around nerve fibers in the PNS.
Satellite cells
Serve as cushioning support cells.

15. Neurons Transmit nerve impulses throughout the body Dendrites
Send information (stimuli) to cell body.
Cell bodies
Includes a nucleus and mitochondria, like all cell bodies.
Axons
Send information (impulses) away from cell body.

17. Neurons
Within the PNS, the Schwann cells wrap around the axon, covering most of it with a fatty myelin sheath.
The myelin sheaths insulate the axon fibers, which increases the rate of impulse transmission.
The myelin sheaths are white, giving rise to the term white matter to describe tracts of myelinated fibers within the CNS.
Gray matter is the term for unmyelinated nerve fibers.

19. Axon terminals are filled with tiny sacs (vesicles) that contain chemical messengers called neurotransmitters.
Axon terminals are separated from other neurons or muscle by a microscopic gap called the synaptic cleft

21. Neuron Types by Function
Sensory (afferent) neurons
Send impulses from the skin and other organs toward CNS
Motor (efferent) neurons
Send impulses away from CNS, to the muscles and glands directing body actions.
Interneurons (association neurons)
Form bridges between neurons

24. Neuron Structures Bipolar Unipolar Multipolar
one axon and one dendrite
Unipolar
one axon
Multipolar
one axon and many dendrites

25. Sympathetic Nervous system
Review and Assessment
Match these words with 1–4 below: sympathetic nervous system, myelin, synapse, axon. 1. High alert 2. Transmits impulses away from cell body 3. Fatty insulating material 4. Gap between neurons
Sympathetic Nervous system
Axon
Myelin
Synapse