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Chapter 44 :Neurons and nervous system - Coggle Diagram
Chapter 44 :Neurons and nervous system
Neurons cells : receive and propagate action potentials // Glial cells : provide support and maintain extracellular environment.
Efferent neurons: carries the
command
to the effector
Interneurons :
Stores information and helps with communication in the system
Sensory : translate input into
action potentials
Afferent neurons : carry information towards the system
Ganglia are neurons arranged into clusters, biggest is found in the brain
Neurons parts
Dendrite : Receives information, towards cell body
Axon: Carries information away from cell body
Axon terminal : forms the synapse at the end of the axon
Cell body: Contains nucleus and organelles
Other functions of glial cells : insulating axon
supply nutrients
/
Central nervous system
Peripheral nervous system
Specialized cells of the nervous system
Schawn cells : produce myelin sheath for insulations of the axons of the PNS
Astrocytes: Contribute to blood-
brain
barrier to protect the brain
Oligodendrocytes: Produce myelin sheath to insulate the axons of the CNS
Action potentials are a result of ions (Calcium,chlorine,potassium,sodium) moving across the membrane, the resting potential is between -60/-70 mV hence at rest the inside of the cells is negative. actions potentials allows + ions
flow in and the cell becomes positive.
Action and resting potentials are created by ion channels and pumps found in the plasma membrane.
The Na/K pumps moves 2K and 3Na out.
Ion channels can be gated i.e they open under some conditions :
1.Mechanically-gated channel : open when a force is applied to the membrane
2.Voltage gated channel : React to a change in voltage
3.Chemically-gated channel : React when a molecules binds to the channel protein.
When these open-close they change the action potentials
Depolarization occurs when Na enters the cell and it becomes more negative .(influx)
Hyperpolarization occurs when K leaves the cell making it more negative inside
A 5-10 mV the threshold is reached. At point Na channels opens, influx of Na ions in making the membrane potential positive, action potential is generated, the Na channels close , the K channels open and the axon returns to resting potential
Na voltage channel have a refractory period i.e they are not opened. Na channels have 2 gates : Activation gate which closed at rest and opens quickly at the threshold. And inactivation gate which is opened at rest and closes at threshold but responds more slowly.
After the action potential has been generated, there is a dip it's called undershoot or hyperpolarization.
Glial cells are the ones that make the neurons to be myelinated however there are gaps along the axon that are not covered by myelin these are called nodes of Ranvier. It's where action potentials are generated, jumping from one node to the other this is known as saltatory conduction.
Neurons communicate between each or target cells with synpases
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