1. The Nervous System

2. The Nervous System
Master controlling and communicating system of the body
Has the same function as what other body system?
Endocrine system
How did these two systems differ?
Endocrine: widespread, slow-acting
Nervous: specific, fast-acting

3. Functions Gathers information and monitors changes sensory input
Processes and interprets the input and makes decisions
Integration
Effects a response
Motor output

4. Organization Structural Central Nervous System (CNS)
Brain and spinal cord
Peripheral Nervous System (PNS)
All of the nerves outside of the CNS

5. Organization Functional—only relevant to PNS
Sensory division AKA afferent division
Conveys impulses to the CNS
Associated with the sensory input
Motor division AKA efferent division
Carries impulse from the CNS to effector organs
Muscles and glands

6. Organization Motor-2 divisions Somatic Autonomic nervous system
Will communicate with skeletal muscle
Voluntary control
Autonomic nervous system
Will communicate with heart, digestive system, and endocrine glands
Involuntary control
Sympathetic nervous system
Fight for flight
Parasympathetic nervous system
Rest and digest

7. Let’s Draw a Tree! The Nervous System CNS PNS
Sensory/Afferent Division
Motor/Efferent
Division
Somatic
Voluntary
Autonomic
Involuntary
Sympathetic
Cardiac/smooth muscle, glands
Parasympathetic
Skeletal muscle

8. Cells
Neurons
Supporting Cells

9. Neurons
Characteristic shape that is specialized to transmit messages (nerve impulses) from one part of the body to another
Major regions
Cell body
Contains the usual organelles and the nucleus
Processes
Fibers that extend from the cell body
Dendrites
axons

10. Neurons-Processes Processes
Dendrites: conduct impulses toward the cell body
Axon: conduct impulses away from the cell body
End at axon terminals
Contain vesicles with neurotransmitters
Often wrapped in a myelin sheath
Nodes of Ranvier = sausage links

11. Axon terminals are separated from the next neuron by a gap
Synaptic cleft
Gap between adjacent neurons
Synapse
Junction between nerves

13. Supporting Cells-CNS CNS Astrocytes Microglia Star-shaped
Help nourish the neurons
Deliver nutrients
Protection
Control chemical environment
Microglia
Spider-like cells
Clean up debris and bacteria
“Garbage man”

14. Supporting Cells-CNS Oligodendrocytes
Create the myelin sheath around CNS neurons
Multiple sclerosis: these cells are destroyed so the cells in the CNS are not myelinated

15. Supporting Cells-PNS PNS Schwann cells Satellite cells
Form myelin sheath around cells in the PNS
Satellite cells
Protective, cushioning cells

16. Physiology 2 main function of neurons Irritability Conductivity
Ability to respond to stimuli
Conductivity
Ability to transmit an impulse

17. The plasma membrane at rest is polarized
This means that fewer positive ions are inside the cell than outside the cell
There is a high concentration of sodium (Na+) OUTSIDE the cell and a high concentration of potassium (K+) INSIDE the cell

18. Let’s draw a picture!
Question: According to diffusion, what direction does sodium want to move?
Question: What direction does potassium want to move?

19. Sodium and potassium are blocked from going in/out of the cell by a series of gatekeepers
Protein channels
To open the gate, they need to be unlocked by the correct neurotransmitter
Remember the lock and key model!

20. Let’s say that the neuron’s dendrite receives a signal
It touches a neurotransmitter
The gates will open and allow sodium to rush into the cell
This causes the membrane to undergo depolarization
Inside=positive, outside=negative

21. If the signal is strong enough (aka a lot of neurotransmitters open a lot of gates), it will cause an action potential (impulse) to travel along the length of the axon
The myelin sheath helps this go faster

22. However, the potassium gates open
Almost immediately after the sodium ions rush into the neuron, the sodium gatekeepers close
However, the potassium gates open
Where will the potassium flow?
OUTSIDE the cell
This reestablishes the electrical conditions within the cell
Called repolarization

23. After the impulse has traveled along the length of the axon, tiny vesicles containing neurotransmitters will fuse with the neurotransmitter membrane
They will diffuse across the synapse, bind the receptors, and the process is repeated! The signal travels on
As the neuron undergoes more action potentials, the ions will continue to move down their concentration gradient.
In order to COMPLETELY restore the neuron to its initial conditions (both with charge and ion concentration), the sodium-potassium pump (a protein) will send sodium OUT and potassium IN
This is an ACTIVE process

24. Let’s List the Steps
A neurotransmitter is released by the pre-synaptic neuron
The neurotransmitter touches a gated Na+ channel
Na+ rushes into the cell
Cell membrane depolarization (gets more positive internally)
K+ gates open
Na+ gates close
K+ rushes out of the cell
Cell membrane repolarization (reestablishes electrical equilibrium)
Neurotransmitters released
Na+/K+ pump reestablishes chemical equilibrium

25. Let’s Look at a Graph

26. Let’s Watch a Video