1. Patrick Yerkes
Nervous System

2. Introduction
The nervous system carries information from one part of the body to another
The nervous system transmit information by nerve impulses to communicate with other parts of the body
Main parts of the nervous system are the: Brain, Spinal Cord, and Nerves
Regulate homeostasis and responds to disease

3. Organs and Divisions of the Nervous System
Central Nervous System (CNS)
Occupies the midline or central part of the body
Peripheral Nervous System (PNS)
Nerves extend to the outlying or peripheral part of the body
Autonomic Nervous System (ANS)
Regulate the body’s involuntary functions

4. Cells of the Nervous System
Two types of cell:
Neurons
Nerve cells
Conduct nerve impulses
Gila
Specialized connective tissue cells
Support neurons

5. Neurons Neurons consist of three parts
Cell body- main part of the neuron
Dendrites- branching projections of the neuron
Processes that transmits impulses to the cell bodies
Axon- elongated projection
Transmits impulses away from the cell body

6. Transmitted Impulses 3 main types of neurons
Sensory- Transmits impulses to the spinal cord and brain from all parts of the body. Also called Afferent.
Motor- Transmits impulses away from the brain or spinal cord. Only conduct impulses to two kinds of tissues (muscle and glandular epithelial). Also call Efferent.
Interneuron- conduct impulses from the sensory neurons to motor neurons. Also call Central or Connective Neurons
Interneuron

7. Neurons continued
Myelin is a white fatty substance formed by a Schwann Cells that wrap the axons around the CNS
The fibers are called Myelinated Fibers
Nodes of Ranvier are indentations between nearby Schwann Cells
The outer cell membrane is the Neurilemma
Axons in the brain and spinal cord do not have Neurilemma and decreases healing or regeneration

8. Gila Also called- Neuroglia
Do not specialize in transmitting nerve impulses
Are support cells
Greek word Gila means “glue”
Holds the functions neurons together and protect them
Regulates nerve function
Common brain tumor is called Glioma

9. Gila continued Gila can be different in size
Large cells that look somewhat like star from their thread like extensions are called- Astrocytes
Microglia- are the smaller cells, they remain stationary
When inflamed or degenerating brain tissue they will enlarge and act as micro scavengers
Eat other micros

10. Gila continued
Oligodenrocytes- hold nerve fibers together and serve a more important function which is to produce fatty myelin sheath that envelops nerve fibers located in the brain or spinal cord

11. Nerves Nerve- is a group of peripheral nerve fibers bundles together
Peripheral nerve fibers usually have myelin sheath
Often look white
Bundles of axons in the CNS are called tracts
The axons could be myelinated and forming white matter
Unmyelinated axons and dendrites are called grey matter for being grey

12. Nerves End
Each axon in a nerve is surrounded by thin wrapping fibrous connective tissue called ‘endoneurium’
Groups of endoneurium are called ‘fascicles’
Each fascicle is surrounded by a thin fibrous ‘perineurium’
A tough fibrous sheath is called a ‘epineurium’ which covers the whole nerve

13. Stop

14. Reflex Arcs Some nerve impulses are called ‘Action Potentials’
Can travel over trillions of routes
Neurons create the paths
Routes named Neuron Pathways
Reflex Arcs are one way streets, the impulse can only go one way

15. Reflex Neurons
A specialized type of neuron pathway is called the ‘reflex arc’
The simplest kind of reflex arc is a two- neuron arc
Consist on only 2 types of neurons: Sensory and Motor neurons
Three- neuron arc is the next simplest arc
Consist of all 3 neurons: Interneurons, Motor, and Sensory

16. Reflex Arc: Receptors
Are the beginnings of dendrites of sensory neurons
Often away from the spinal cord mostly located in; (in tendons, skin, or mucous membranes)
Sensory receptors are located in the quadriceps and the patellar tendon
Reflex response for the patellar tendon which is the rubber hammer and creates a knee- jerk
Example of a two- neuron arc

17. Reflex Arc: Ganglion A group of nerve- cell bodies located in t he PNS
Near the Spinal cord
Each spinal ganglion contains no sensory neuron
The axon of the sensory neuron travels from the cell body in the dorsal root ganglion
Ends in the dendrites of another neuron in the grey matter

18. Reflex Arc: Continued
A microscopic space that separates the axon ending with one neuron from the dendrites to another
This is called a Synapse
Nerve impulse stops at the synapse
The neuron axon forms a synapse called the ‘effectors’
Organs put the nerve signals to effect

19. Reflex Arc: Effectors Effectors are the muscles and glands
Muscles contract
The glands secretion
Only kind of reflexes by these effectors
A response to impulse conduction on the reflex arc is called a reflex

20. Reflex Arc: Interneuron
Some neurons need 3 neurons
More complex involves one more sensory and motor neuron
In the 3 neuron reflex
End of the sensory neurons’ axon synapses first with a interneuron
Before chemical signals are sent to a second synapse
Ending up with a conduction motor neuron

21. Reflex Arc: Example
Applying an irritating stimulus to the skin of the thigh
It creates a 3- neuron reflex response
Causes contractions of the muscles to pull away from the leg away from the irritant
3 neuron contraction is also called a - withdrawal reflex

22. Reflex Arc: Interneurons Continued
All interneuron's’ lie entirely within gray matter of the brain or spinal cord
Grey matter forms the ‘H’ shaped inner core of the spinal cord
3 neuron reflex has 2 synapses
2 neuron reflexes has 1 synapses between a sensory neuron and the motor neuron

23. ID motor neuron Reflex Arc: Identify
Look at its dendrites and cell body
Located in spinal cord
Dies in the muscles

24. Stop

25. Nerve impulse: Introduction
A nerve impulse is a self- propagation wave of electrical disturbance that travels along the surface of a neuron’s plasma membrane.
Example
A Spark going to fuse

26. Nerve Impulse: Neuron
First they have to be stimulated ( a change in the neuron’s environment)
Temperature, Pressure, and chemical changes are used as stimuli
Membrane of a resting neuron has a slight positive charge on the outside and a negative charge on the inside
This occurs from excessive amounts of sodium ions (NA+) on the outside of the membrane

27. Nerve Impulses: Neuron continued
When the section of the neuron is stimulated and the channels open
The sodium ions (NA+) flood inside
Causing the membrane to become positive temporarily and then becomes negative
The neuron immediately recovers the electrical disturbance stimuli (Na+)
If a impulse is traveling interacts with a section of a membrane insulating myelin
‘jumps’ around the myelin called ‘saltatory conduction’
Saltatory Conduction can travel much faster then the nonmyelinated sections

28. Saltatory Conduction

29. Stop

30. Synapse: Introduction
By definition a synapse is a place where impulses are transmitted from one neuron called presynaptic neuron to another postsynaptic neuron.
The presynaptic and postsynaptic neuron makes up the synapse

31. Synapse: Structures
Three structures of the synapse is: a synaptic knob, a synaptic cleft, and the plasma membrane of a postsynaptic

32. Synapse: Synaptic Knob
Is a tiny bulge at the end of the terminal branch of a presynaptic neuron’s axon
Each synaptic knob has many small sacs or vessels
Each vessel contains a very some quantity of a chemical compound called a neurotransmitter
After the nerve impulse arrives at the synaptic knob neurotransmitters molecules are released from the vesicles into the synaptic cleft

33. Synapse: Synaptic Cleft
Is the space between the plasma membrane (of the postsynaptic neuron) and the synaptic knob
About 2 millionths of a centimeters in width
Has protein molecules embedded in opposite synaptic knobs
The receptors and neurotransmitters bind
The binding can cause an impulse in the postsynaptic neuron by opening the ion channels in the postsynaptic membrane

34. Synapse: Neurotransmitter
Neurotransmitters -Chemicals help neurons communicate
Around 30 different compounds have been identified as neurotransmitters
Neurotransmitters are did sent randomly
They are localized in certain types of neuron groups and released in specific pathways

35. Synapse: Neurotransmitter Sub Groups
Acetylcholine
catecholamine
Released in certain areas in the Spinal Cord
Also in the neuromuscular junctions
Also called nerve- muscle
Includes
Norepinephrine
Dopamine
Serotonin
All three of these transmitters play a role for
Sleep
Motor function
Mood
Pleasure recognition

36. Synapse: Sub Groups

37. Synapse: Pain Killer (Neurotransmitters)
2 ‘morphine’ like N.transmitters are called endorphins and enkephalins
Released in multiple areas in the spine and brain in the pain conduction pathways
Are natural pain killers
Endorphins are released mainly in intense exercise
Pain is normally used as a warning sign that draws our attention to injuries
Hold back against severe pain because it can stop us from continuing an activity that is needed for survival

38. Activities to help relieve pain

39. Synapse: Nitric Oxide
Unlike other transmitters Nitric Oxide diffuses directly across the plasma membrane
Rather then being released in the vesicles
Nitric Oxide is important for the male sexual response to create a penile erection
Drugs like Viagra (sildenafil) treats MED or Male Erectile Dysfunction by promoting the Nitric Oxide response

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