ion - electrically charged molecule
Anion - Neg. charged ion
Cation - Pos. charged ion
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Where are anions and cations?
Inside the neuron within intracellular fluid. Outside the neuron are other ions in extracellular fluid.
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Are there more anions or cations inside a neuron?
Anions, so it is negatively charged.
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What is electrical charge across a cell membrane?
The difference in electrical potential inside and outside the cell.
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What is resting potential?
Balance of ions at rest (about 70mV)
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What is action potential?
Brief electrical impulse (big charge in cell membrane potential) that provides the basis for conduction of info along an axon.
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What must happen for action potential to occur?
The level of depolarisation (inside of axon becoming more positive) must reach threshold of excitation.
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What are the ionic forces?
Diffusion, electrostatic pressure
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What is diffusion?
Molecules move from areas of high conc. to area of low conc. across a semi-permeable membrane.
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What is electrostatic pressure?
Opposite charges attract one another, like charges repel.
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What are organic anions?
They can't move across cell membrane so help to maintain internal negative charge.
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What are potassium ions?
High conc. inside and so diffusion forces it to move outside. But outside has a positive charge compared to the inside, so electrostatic pressure keeps it where it is.
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What are chloride ions?
(like potassium) are under two opposing forces, so remain where they are.
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What are sodium ions?
High conc. outside, so diffusion would make it move inside. The charge inside is opposite, so electrostatic pressure helps to force it inside the neuron.
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What happens in the sodium (NA+)-potassium (K+)pump?
2 Sodium are pushed out, for every 1 potassium allowed in, so it maintains resting potential.
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What leads to depolarisation?
If membrane becomes more permeable to diffusion of sodium, electrostatic pressure will cause more sodium to enter the cell, which will lead to a increase in positive charge (depolarisation)
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What causes a change in permeability?
Opening of sodium channels
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What leads to action potential
Change in permeability leading to depolarisation. The opening of the sodium channel starts the potential, and then potassium channels are step 2.
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Summary of synaptic transmission
1) action potential in pre-synaptic neuron
2)Depolarisation from action potential opens calcium channels in PS neuron
3) Calcium enters PS neuron
4) calcium triggers vesicles to fuse with synaptic membrane
5)vesicles release neurotransmitter into synapse
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Cont.
6)Neurotransmitter binds with receptors in the Post-synaptic membrane
7)Neurotransmitter binding with post-synaptic receptors opens some ion channels in post synapticc neuron
8) opening of ion channels letting in cations (EPSP), letting in anions (IPSP)
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Cont.
9) summation of EPSPs to IPSPs is excitatory enough to depolarise too threshold, so the neuron will fire action potential.
10) excess neurotransmitters are degraded by enzymes
11) excess neurotransmitters are taken back by pre-synaptic neuron.
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What are post-synaptic receptors
Specialised to fit certain neurotransmitters (lock and key), molecule of correct fit to receptor is called a Ligand.
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What is a ligand?
Molecule that fits receptors, can be endogenous (occurring naturally in the body) or exogenous (drugs, toxins etc from outside).
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Examples of neurotransmitters
Dopamine, serotonin, endorphins etc.
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Reading?
Kolb, 4 & 5
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Other cards in this set
Card 2
Front
Where are anions and cations?
Back
Inside the neuron within intracellular fluid. Outside the neuron are other ions in extracellular fluid.
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