transmission within neurons Flashcards
What are the 3 types of neurons?
-Sensory neurons
-Interneurons
-Motor neurons
What is the function of sensory neurons?
-Info from the body to CNS e.g. light, sound, touch and pressure
What is the function of motor neurons?
-Info from CNS to the body e.g. control muscles which is important for movement
What is the function of interneurons?
-Links sensory neurons and motor neurons within the brain
Define diffusion
-Particles moving from high concentration to low concentration
Define electrostatic pressure
-Attraction or compulsion of particles depending on their charge
What do neurons do?
-Complete all info processing and transmitting
-86 billion neurons
What are the different parts of a neuron?
-Soma
-Dendrites
-Axon
-Myelin sheath
-Terminal buttons
What is the function of the soma
-Cell body which contains nucleus and machinery that provides life processes of a cell
What is the function of the dendrites
-Receives the neural messages from one neuron to another via synapse
What is the function of the axon
-Long and slender tube
-Carries information (action potential) from soma to terminal buttons
What is the function of the myelin sheath
-Wraps around axon
-Insulation
What is the function of the terminal buttons
-End of axon branches
-Action potential is travelling down the axon, and they secrete a chemical called neurotransmitters
What are glial cells?
-Includes;
-Astrocytes (star shaped)- supports and provide nutrients
-Oligodendrocytes
-Microglia - clear away dead cells, attack foreign tissue and repair damage caused
What are oligodendrocytes?
-Produce the myelin sheath that helps axon insulation
What is the Node of Ranvier?
-Naked axon
-Lack of insulation
What is the process of transmission within a neuron?
-Electrical process
-Movement of ions across membrane
-Inside the cell has more of a negative charge than the outside
-Causes resting potential
-Neurons can reverse electrical charge
What is the function of cell membrane?
-All cells are covered in a membrane
-2 layers of phospholipid molecules (head of molecule is phosphate and tail is a fatty acid)
-Contains ion channel which spans the membrane
What are the different ions?
-Charged molecules
-Cations = positively charged
-Anions = negatively charged
What are the 2 types of fluid?
-Intercellular fluid - potassium ions and anions
-Extracellular fluid - sodium and chloride ions
What is membrane potential?
-Difference in electrical potential inside and outside of a cell
-Balanced by diffusion and electrostatic pressure
Organic anions that are concentrated inside the cell…
-Can’t cross membrane and leave cell
Potassium ions that are more concentrated inside the cell…
-Diffusion where it wants to move out
-Attracted to inside
-Forces balance so K+ doesn’t move
Chloride ions are more concentrated outside the cell…
-Diffusion where it wants to move in
-Repelled from inside
-Forces balance so Cl- doesn’t move
Sodium ions are more concentrated outside the cell…
-Diffusion where it wants to move in
-Attracted to the inside
-Both force Na+ into cell
-Kept under control by sodium-potassium pumps
Describe resting potential
-Maintaining this is crucial
-Electrical charge of neuron then it isn’t rapidly sending messages
Describe action potential
-Reversal in potential
-Rapid change in membrane potential and polarisation
-Forces of diffusion pushes Na+ into the cell, suddenly becomes permeable for this ion despite it not normally being
What is the ‘all or nothing’ process?
-Either fires or doesn’t fires
-Stays the same size through transmission
What is the difference between depolarisation and hyperpolarisation?
-Depolarisation - Decrease from normal resting potential (brings membrane closer to 0)
-Hyperpolarisation - Increase from normal resting potential (more negative_
What is the first point of the graph?
-Na+ channels open
-Begins to enter cell when exceeds threshold of excitation
What is the second point of the graph?
-K+ channels open
-K+ leaves cell
What is the third point of the graph?
-Na+ channels are refractory and full
-No more Na+ enters
What is the fourth point of the graph?
-K+ continues to leave cell
-Membrane potential returns to resting level
What is the fifth point of the graph?
-K+ channels close
-Na+ channel reset
What is the sixth point of the graph?
-Extra K+ outside diffuses away
What is propagation?
-Action potential is transmitted down an axon
-Regenerated at points along axon due to entry of sodium ions
-One direction
What is saltatory conduction?
-Regenerated at action potential along axon at Nodes of Ranvier
-Fast conduction
-Energy efficient
