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The Neuron Notes PPT
2.2.1 : The Neuron
Part I Basic Neuron Design (work in Pairs)
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Part II Relaying The Message (individually-may hand draw, MS Word, or Inspiration)

2. The Neuron Nervous System

3. Basic Divisions of the Nervous System: CNS
Central nervous system (CNS)
Brain and spinal cord - a long bundle of neurons that carries messages to and from the body to the brain that is responsible for very fast, lifesaving reflexes.
Integrating and command center

4. Basic Divisions of the Nervous System: PNS
Peripheral nervous system (PNS)
Outside the CNS
Nerves extending from brain and spinal cord
Cranial nerves
Spinal nerves
Link all regions of the body to the CNS

5. Sensory Input and Motor Output
Sensory signals picked up by sensory receptors
Carried by afferent nerve fibers of PNS to the CNS – nerves that transmit info to the CNS
Motor signals are carried away from the CNS
Carried by efferent nerve fibers of PNS to effectors – nerves that transmit info from CNS to the PNS (organs)

6. Nervous Tissue Cells are densely packed and intertwined
Two main cell types
Neurons – transmit electrical signals
Support cells - neuroglial cells
Surround and wrap neurons

7. The Neuron The human body contains billions of neurons
Basic structural unit of the nervous system
Specialized cells conduct electrical impulses along the plasma membrane
Longevity – can live and function for a lifetime
Do not divide – fetal neurons lose their ability to undergo mitosis – do NOT have centrioles
High metabolic rate – require abundant oxygen and glucose

9. Basic Neuron Structure

10. The Cell Body Many Mitochondria
Contains the cell’s nucleus
round, centrally located structure
contains DNA
controls protein manufacturing
directs metabolism
no role in neural signaling
Many Mitochondria
Nissl Bodies- groups of ribosomes – make protien

11. Dendrites Information collectors
Receive inputs from neighboring neurons
Inputs may number in thousands
If enough inputs, the cell’s AXON may generate an output
Surface is rough
Branch near cell body

12. Axons Takes information away from cell body Smooth surface
One axon per cell, 2 distinct parts
tubelike structure
branches at end that connect to dendrites of other cells
Axon Terminal
Releases information
to the next neuron/dendrite

13. Myelin Sheath White fatty casing on axon
Acts as an electrical insulator
Made by Schwann Cells – in the PNS
When present, increases the speed of neural signals down the axon

15. ****Oligodendroglia***
Cells that make insulates the axons in the CNS – specifically the brain.
One single oligodendroglia can insulate up to 50 axons
Difference – one Schwann cell is needed for one axon in the PNS

16. Nodes of Ranvier
In between the areas of myelin sheath, Nodes of Ranvier or bare patches exist.
The nerve impulse will jump form node to node greatly increasing the speed of nerve transmission.
can produce transmission speeds of up to 200 meters per second and explains the speed at which we can react to potentially harmful stimuli.

17. Neurons and Synapses
Types of Neurons
Sensory
Motor
Interneurons

18. Length of Fibers Location Function Sensory neuron Interneuron
Motor Neuron
Length of Fibers
Long dendrites and short axon
Short dendrites and short or long axon
Short dendrites and long axons
Location
Cell body and dendrite are outside of the spinal cord; the cell body is located in a dorsal root ganglion
Entirely within the spinal cord or CNS
Dendrites and the cell body are located in the spinal cord; the axon is outside of the spinal cord
Function
Conduct impulse to the spinal cord
Interconnect the sensory neuron with appropriate motor neuron
Conduct impulse to an effector (muscle or gland)

19. Motor Neuron Efferent Neuron – Moving toward a central organ or point
Relays messages from the brain or spinal cord to the muscles and organs

20. Sensory Neuron
Afferent Neuron – Moving away from a central organ or point
Relays messages from receptors to the brain or spinal cord

21. Interneurons Relays message from sensory neuron to motor neuron
Make up the brain and spinal cord

22. Neuron Types
Based on what is coming out of the cell body (also known as the soma)

23. BiPolar Neuron
Has two processes extending from the cell body (example: retinal cells, olfactory epithelium cells.
Rare

24. Unipolar Neuron Have but one process from the cell body.
However, that single, very short, process splits into longer processes (a dendrite plus an axon).
Unipolar neurons are sensory neurons - conducting impulses into the central nervous system.

25. Multipolar neurons
Are so-named because they have many (multi-) processes that extend from the cell body:
lots of dendrites plus a single axon.
Functionally, these neurons are either motor (conducting impulses that will cause activity such as the contraction of muscles) or association (conducting impulses and permitting 'communication' between neurons within the central nervous system).