Week 2 Flashcards
Myelin Sheath
-Some axons are covered with little beads of myelin
- Is predominantly a fatty material. It acts as an insulator and conductor of nerve impulses
- It speeds the process of communication within the neuron
Glial Cells
-Neurons are supported and assisted by glial cells
-If the neuron is the main character, then the glial cells are the supporting staff
- They grow and produce during the embryonic period
Roles of Glial Cells
- Play a central role in brain development within the nervous system; aids movement of neurons from one position to another
- Supply nutrients and oxygen to neurons and play a key role in controlling these nutrients
- Provide structural support to neurons; directing their growth
- Insulate neurons by forming the myelin sheath around them
- Remove debris left over after the death of cells i.e. synaptic pruning
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Oligodendrocytes
Provide insulating myelin sheath around neurons within the central nervous system i.e. brain and spinal cord
Schwann Cells
Provide insulating myelin sheath around neurons within the peripheral nervous system
Action Potential
A brief, electrical event which brings about a brief reversal in the electrical charge of an axon
What is RMP and how is it maintained
- Occurs when the neuron is at rest
- The steady difference in voltage/ electrical charge between the inside and outside of the axon membrane; this difference in charge is -70mv
Ion
A charged atom/ group of atoms
What causes RMP?
- Results from differential distribution of ions across nerve cell membrane
- Na+ ions are in higher concentration outside cell
- K+ ions are in higher concentration inside cell
- RMP is polarized
- Difference in polarity is 70mv
-Polarization will create the electrical energy necessary to power the firing of action potential
Polarisation
- The neuron has more negative ions inside it that outside it which has more positive ions
What Maintains RMP
-Fluid inside the cell membrane is separated from fluid outside it by cell membrane (semi-permeable)
-When nerve cell is at rest, the Na ion channels closed, and K channel is partially closed
- Sodium-potassium pump slowly pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell
- Helps maintain RMP at -70mv
Ion Channels/ Transporters
Regulate the number of ions found inside and outside the cell
Voltage- Sensitive Gates
- Some ions have
- The gates open or close according to the value of the cells membrane potential
- If the RMP changed by a certain amount, the gates would open up
Diffusion
Without barriers, molecules move from a region of high concentration to a region of low concentration
Electrostatic Pressure
Attractive forces between atomic particles charged with opposite signs or the repulsive force between atomic particles charged with the same sign
What would happen if voltage gates opened; Potassium ions
- High concentration inside and lower concentration outside
- Diffusion tends to force them out but electrostatic pressure keeps them in (as outside is +)
- Opposing forces balance
What would happen if voltage gates opened; Chloride Ions
- Higher concentration inside
- Diffusion tends to force it in but electrostatic pressure keeps it out
- Opposing forces balance
What would happen if voltage gates opened; Sodium Ions
- Higher concentration outside, lower concentration inside
- Na+ ions are positively charged and the inside of the axon is negative
- Diffusion tries to force inside since they are in higher concentration inside
- Electrostatic Pressure tries also tries to force them inside since the outside is positively charged with respect to the inside which is negatively charged
If Voltage- Gated channels opened up; what would happen to charged particles
- If axon suddenly becomes permeable to Na+ ions
- Diffusion and electrostatic pressure would cause Na+ to rush into nerve cell
- AKA an action potential
