Central Nervous System
the brain and spinal cord
Peripheral Nervous System
the nerve tissue located outside of the brain and spinal cord
Glial Cells
- provide physical support
- control nutrient control
- involved phagocytosis
Schwann Cell
-myelin sheath in the peripheral nervous system
Oligodendrocyte
-myelin sheath in the central nervous system
Microglia
- phagocytosis
- act like the immune system
Astrocyte
- creates the blood brain barrier
- takes things from the blood vessels and passes them onto the nutrients
Ramni Calal
-thought that there were synapses
Golgi stain
- first stain that showed the whole neuron
- thought that neurons were connected
Why do neurons have different shapes?
-different shapes for different functions
-some neurons bring information into the brain
some neurons send information out of the brain or to other parts of the brain
Neuronal signaling overview
- the presynaptic neuron gives off a chemical signal to the postsynaptic neuron that gets turned into an electrical signal
- that electrical signal gets turned into another electrical signal and shoots down the axon
Membrane potential/Resting membrane potential
- -70 mV means that the inside is more negative than the outside
- resting membrane potential is usually about -70 mV
Where do the electrical and concentration gradients push potassium (K)?
- the electrical gradient pushes potassium into the cell
- the concentration gradient pushes potassium out of the cell
- these forces balance each other out
Where do the electrical and concentration gradients pusH sodium (NA)?
- the electrical gradient pushes sodium into the cell
- the concentration gradient pushes sodium into the cell as well
What does the sodium-potassium pump do?
- pushes potassium into the cell
- pushes sodium out of the cell
What factors affect membrane potential?
- concentration gradient
- electrical gradient
Ion channels + properties
- passive transport
- PROPERTIES of Ion Channels
1. they are gated (you can open and closed them
2. this is how neurons send electrical signals and change membrane potential
3. they can be selective
Voltage Gated Na+ Channels
- opens when senses depolarization
- fast opening
- quickly inactivates
Voltage Gated K+ Channels
- opens when senses depolarization
- delayed opening
- stays open until cell repolarizes
How are Voltage Gated Ion CHannels opened?
Voltage = a change in membrane potential opens them
Hodgkin-Huxley Cycle
-happens where the axon is connected to the soma
-synaptic potential or receptor potential
1. membrane depolarizes
2. voltage-gated Na+ channels open
3. Na+ flows into neuron
back to 1.
What is the Action Potential
- the action potential is the electrical signal that travels down the axon
- depolarization threshold/threshold of excitation must be reached
- all or none
Myelin Sheath and Transport
- the myelin sheath allow for a tradeoff between passive and active transport
- when you have passive transmission of an axon potential the signal is not as strong
- when you have active transmission of an axon potential, you put the channels all along the axon and it takes time to build up
Saltatory Conduction
-when a signal travels under the myelin it is passive
when a signal travels at the nodes of Ranvier, there are concentrations of voltage gated channels and it is actively transported
-the passive conduction allows for speed while the active conduction allows for strength
-in MS the myelin sheath is attacked and destroyed by the immune system which results in motor and nerve issues
