1. Unit VII - The Nervous System: Part 1
Nerve Cells & the
Central Nervous System

2. Structural Subdivisions
Central NS
Brain & Spinal Cord
Peripheral NS
Cranial & Spinal Nerves

3. Functional Subdivisions

4. Functional Subdivisions
Somatic NS
Information to/from voluntarily controlled organs (skeletal muscles)
Somatic Sensory – Information In (afferent)
Somatic Motor – Information Out (efferent)
Autonomic NS
Information to/from involuntary organs (smooth & cardiac muscles and glands)
Sympathetic Division – “fight or flight”
Parasympathetic Division – “rest & repair”

5. Divisions of the Autonomic NS
“rest & digest”
“fight or flight”
Divisions of the Autonomic NS

6. Cells of the Nervous System
Two Categories:
Neurons – transmit messages
Neuroglia – “assistants”

7. Neuron Structure Cell Body (soma)
Resembles other cells; holds organelles
Dendrites
Highly branched; receive signals
Axons
Long process; Sends signals out
Usually covered in a myelin sheath
Larger diameter = faster conduction

8. Structural Classification of Neurons
Bipolar
1 axon; 1 dendrite; (both branched at tips) rare
Unipolar
1 process; divides into 1 axon & 1 dendrite (branched at tips) sensory
Multipolar
1 axon; several dendrites

9. Functional Classification of Neurons
Afferent (Sensory) Neurons
Transmit to spinal cord or brain
Efferent (Motor) Neurons
Transmit to muscles and glands
Interneurons
Conduct between sensory and motor neurons
synapse = where neurons meet other neurons, muscles, or glands

10. The Other Cells of the NS…
Glia (Neuroglia) – “nerve glue”
Do not conduct information
Serve as support
Numerous!
Able to reproduce

11. Types of Glia Astrocytes Largest & most common glia cells
Transfers nutrients from blood to neurons
Forms the blood-brain barrier
Astro = star

12. Types of Glia Microglia Smallest glial cells
Phagocytize (eat) when brain inflamed
Micro = small
Glia = glue

13. Types of Glia Ependymal Cells Form sheets that line fluid-filled areas
Help form fluid and help move it (cilia)
Hint: think of cilia like apPENDages

14. Types of Glia Oligodendrocytes Few branches
Make the myelin sheath around nerves in CNS
Help hold nerve fibers together
Oligo = few
Dendr = tree (branches)

15. Types of Glia Schwann Cells Only in peripheral NS (nerves)
Forms myelin sheath

16. Synapses
Site where axon of one neuron meets with a neuron, a muscle cell, or a gland cell

17. Synapses
Vesicles receive signal to secrete neurotransmitter which travels across synaptic cleft (space) and eventually binds to receptors on the post-synaptic cell (the next cell).
This carries the activation signal to that next cell.

18. Neurotransmitters Acetylcholine Serotonin Dopamine Epinephrine
Excites skeletal muscle
Serotonin
Moods; emotions; sleep
Dopamine
Emotions; mood; motor control
Epinephrine
Fight or flight

19. Side Note: Drugs & Neurotransmitters
Some drugs (like cocaine) block the re-uptake of dopamine
This causes too much dopamine to signal next cell
In the case of cocaine, this causes over-stimulation of pleasure center in brain
Long-term effect though, is that body stops making enough dopamine

20. Side Note: Drugs & Neurotransmitters
Some toxins work by blocking enzymes that break down acetylcholine (ACh)
ACh never leaves receptor - nerve impulse cannot fire anymore, so muscles can not contract

21. Reflex Arcs stimulus -> sensory neuron -> CNS ->
interneuron -> motor neuron -> effector

22. Nerves Bundles of fibers of peripheral NS
Nerve cell - bound by endoneurium
Fascicle - bound by perineurium
Complete nerve - bound by epineurium

23. Nerves Nerve bundles with myelin sheaths look white
Bundles without myelin sheaths look gray

24. Nerve Repair Mature neurons cannot do mitosis, so cannot be replaced
Neurons in PNS might be repaired, but cannot do so very well
Distal part of axon degenerates
“sprouts” of axon appear & move to broken spot to connect
In CNS, repair is very unlikely

25. Types of Nerve Damage

26. The End

27. FAKE QUIZ! Answer in your notebook – on a left-side page if possible.
You do not need to write the questions, but you may want to do so for study purposes.

28. Self Quiz 1. Fill in the blanks… Nervous System
Structural Divisions Functional Divisions
__A__ __B__ __C__ __D__
Brain & __E___ Afferent __F___ __G___
Spinal Cord (Sensory) Parasympathetic

29. Self Quiz 1. Fill in the blanks… Nervous System
Structural Divisions Functional Divisions
CNS PNS Somatic Autonomic
Brain & Nerves Afferent Efferent Sympathetic
Spinal Cord (Sensory) (Motor) Parasympathetic

30. Self Quiz
Match the nervous system cells with the appropriate descriptions…
A. oligodendrocytes C. astrocytes E. microglia
B. ependymal cells D. Schwann cells F. neurons
Connect the neurons to capillaries
The two types that form myelin sheaths
Engulf (eat) debris surrounding damaged nervous tissue
Transmit electrical messages
6. Allow for better movement of cerebrospinal fluid

31. Self Quiz
Match the nervous system cells with the appropriate descriptions…
A. oligodendrocytes C. astrocytes E. microglia
B. ependymal cells D. Schwann cells F. neurons
Connect the neurons to capillaries - C
The two types that form myelin sheaths – A & D
Engulf (eat) debris surrounding damaged nervous tissue - E
Transmit electrical messages - F
6. Allow for better movement of cerebrospinal fluid - B

32. Self Quiz 7. Label the parts… A (wraps nerve) B (bundle of cells)
C (wraps cell)
Nerve Cell

33. Self Quiz 7. Label the parts… A - epineurium B - fascicle
C - endoneurium
Nerve Cell

34. Self Quiz 8. Name the parts of the neuron…
axon - soma/cell body – dendrite - myelin sheath A B C D

35. Self Quiz 8. Name the parts of the neuron…
axon - soma/cell body – dendrite - myelin sheath
A - dendrites
B – myelin sheath
C - axon
D – soma/cell body