Neurons and Synapsis (6.5)
The Nervous System
The Nervous sytem consists of two parts the Central Nervous System(CNS) and the Peripheral Nervous System (PNS).
|
The Nerve
The nervous system is composed of neurons. These cells carry rapid electrical impulses throughout the body.
|
The Mylein Sheath
The axons of nerves are cylindrical. Most axons are coated by a fatty white substances called myelin, acting as an insulator. Mylein
Multiple Sclerosis is an autoimmune disease that attacks the myelin sheath. This results in a loss of nerve signal causing numbness, weakness, tremors, fatigue, slurred speech, loss of function, lack of coordination, etc |
The nere Impulse
Nerves function by the movement of charged ions. When the membrane potential (charge) is changed from the inside to outside of an axon. The potential is created through the movement of sodium (Na+) ions and potassium (K+) ions.
If a nerve is NOT transmitting the potential (or voltage) across the membrane is referred to as its resting potential. Due to an imbalance of mostly positively charged ions across the membrane.
|
|
The Action POtential
The Nerve impulse can be seen as a graph of voltage across the membrane, called the action potential.
Please see Cellular Transport (1.4) for a review of voltage gated channels (ball and chain) and active transport. Phet Simulation |
|
|
propagation of the Action Potential
So how does a nerve impulse move down the nerve from the cell body through the axon? This is called propagation of the action potential. It occurs because of ion depolarization.
|
Synaptic Transmission
What is a synpase?
A synapse is the junction between two nerve cells. Where the axon of one meets the dendrite or cell body of the next nerve. Stages of Synaptic Transmission:
|
Acetolcholine Neurotransmitter specifically:
|
|
|
Disruption of Acetylcholine and Neonicotinoids
Disruption of AcetylcholineMany chemicals can disrupt, slow down, speed up, or stop signals all together. Two acetylcholine disrupters are Nicotine and Sarin Gas.
Why would these things cause problems from the nerve?
|
NeonicotinoidsNeonicotinoids = synthetic compounds that function similar to nicotine
Nicotine and transmission |