Lecture 3- Transmission within neurons Flashcards
What do motor neurons do?
They provide information to the body
What do sensory neurons do?
Provide info from the body
What do inter neurons do?
Link sensory and motor neurons
What do neurons do?
They do all the info processing and transmitting through variety of different neuron types
Name the 5 aspects of the structure of a neuron
Soma
Dendrites
Axon
Myelin sheath
Terminal buttons
What is the soma?
(neuron structure)
The cell body
-Contains the nucleus
What are dendrites?
(neuron structure)
Receive messages
-Tree like structure
What is the axon?
(neuron structure)
Carries info (action potential) from soma to terminal buttons
What is the Myelin sheath?
(neuron structure)
Wraps around axon
What are the terminal buttons?
(neuron structure)
At the end of the axon branches
What do Glia (glial cells) include?
Includes Astrocytes, Oligodendrocytes, Microglia
What do Glia (Glial cells) do?
Oligodendrocytes produce the myelin sheath that insulates axons.
-Nodes of Ranvier = naked axon
-Cells provide support, waste services, supply of nutrients
Describe the transmission within neuron
-An electrical process (all cells have electrical charge, more neg on inside) -This results in a resting potential (store of energy) -Neurons can reverse electrical charge
What is the cell membrane?
Membrane- All cells are covered in membrane, 2 layers of phospholipid molecules.
What is the ion channel?
Spans the membrane
What are the 2 types of ions?
Cations (pos charged)
Anions (neg charged)
What does Intercellular fluid contain?
Potassium ions (K+) and anions (A-)
What does Extracellular fluid contain?
Sodium (Na+) and chloride (Cl-) ions
What is the membrane potential?
The membrane potential is the difference in electrical potential inside and outside the cell.
How is the membrane potential balanced?
Diffusion and Electrostatic pressure
Describe Organic anions (A-)
-Concentrated inside cell
-Cannot cross the membrane
Describe Potassium ions (K+)
-More concentrated inside cell
> Diffusion= Wants to move out
Electrostatic= Attracted to inside
Overall= Forces balance so K+ doesn’t move
Describe Chloride ions (Cl-)
-More concentrated outside cell
> Diffusion= Wants to move in >Electrostatic= Repelled from inside
Overall= Forces balance so Cl- doesn’t move
Describe Sodium ions (Na+)
-More concentrated outside cell
> Diffusion= Wants to move in >Electrostatic= Attracted to inside
Overall=Both force Na+ into cell
How is Na+ kept under control?
-Na+ kept under control by sodium-potassium pumps
In resting potential, what is the difference between inside and outside?
Inside= negative Outside= positive
What is the resting potential of a neuron?
-70mV
Why is maintaining the resting potential important?
It’s important so the neuron can respond rapidly to a stimulus.
What is an action potential?
An action potential is a reversal in the potential and is how information is sent through an axon.
- Also a rapid change in the membrane potential
How could you describe an action potential?
Considered an all or none process as either fires or not, they stay the same size throughout transmission.
What is depolarisation?
A decrease from normal resting potential (brings membrane closer to 0)
What is hyper polarisation?
An increase relative to resting potential (more negative)
What is Propagation?
-The action potential is transmitted down an axon via propagation.
-The action potential is regenerated at points along axon due to entry of sodium ions at neighbouring point eg dominoes falling
What is Saltatory conduction?
-Action potential regenerated along axon at nodes of Ranvier
What are the benefits of Saltatory conduction?
Benefits:
-Fast conduction
-Energy efficient
Describe the process of action potential
(6 steps)
-Once the threshold of excitation has been reached, the Sodium (Na+) channels open and Na+ enters the cell.
-Potassium (K+) channels then open in which K+ begins to leave the cell
-Na+ channels the become refractory in which no more Na+ can enter the cell.
-K+ continues to leave cell, causing membrane potential to return to resting level.
-K+ channels close so Na+ channels reset
-Extra K+ outside diffuses away.
