Lecture 18 Flashcards
What neuron releases neurotransmitters and which senses them? What happens when that neuron senses a neurotransmitter?
- pre-synaptic neuron releases neurotransmitters
- post-synaptic neuron senses neurotransmitters
- neurotransmitters cause ion channels to open
What is a chemical gated ion channel?
- stimulus = chemicals
- channel changes shape, opens
- ions cross the membrane, driven by electrochemical gradient
- neurotransmitter unbinds, causing channel to close
What is a voltage gated ion channel?
- stimulus = membrane depolarizes to threshold voltage
- channel changes, opens
- ions cross membrane driven by electrochemical gradient
- membrane potential changes will cause the channel to inactivate or close
- has 2 channel openings, so can be closed, open, or inactivated
What is a mechanically gated ion channel?
- stimulus = deformation of the membrane
- channel changes shape, opens
- ions cross driven by electrochemical gradient
- when membrane returns to original shape, channel closes
What gated channels are on the dendrites and cell body?
Na+ and Cl- chemical gated channels and in some mechanical gated channels (e.g in finger tips)
What gated channels are on the axon hillock?
Na+ and K+ voltage gated channels
What gated channels are on the axon?
Na+ and K+ voltage gated channels
What gated channels are on the axon terminal?
Ca2+ voltage gated channels
What is the resting membrane potential? What is the electronegativity of the intracellular and extracellular sides of the membrane?
Resting membrane potential = -70mV
Intracellular = more negative, high K+, low Na+
Extracellular = more positive, low K+, high Na+, more Cl-
What are local potentials? What is its other name?
A change in voltage in a small location somewhere on the dendritic/cell body membrane of the post-synaptic neuron. Can also be called post-synaptic potential.
How do excitatory local potentials form?
- pre-synaptic neuron releases excitatory neurotransmitter e.g ACh (acetylcholine)
- when it binds, it opens chemically gated Na+ channels
- Na+ enters post-synaptic cell, causing depolarization (membrane becomes more positive)
How do inhibitory local potentials form?
- pre-synaptic return releases inhibitory neurotransmitters e.g GABA
- neurotransmitter binds, opening chemical gated K+ or Cl- channels
- K+ exits or Cl- enters post-synaptic cell, causing hyperpolarization of cell (membrane becomes more negative)
Why is it just as important to have inhibitory local potentials as excitatory local potentials?
Because otherwise we would be paying attention to every possible stimulus, and won’t be able to block anything out and concentrate on what’s important
What is spatial summation?
The summed input from multiple pre=synaptic neurons
What is temporal summation?
The summed input from repeated firing of one pre-synaptic neuron
What is threshold potential?
The minimum voltage needed for an action event to occur. Is -60mV
How does action potential work?
- Voltage gated Na+ channels open when membrane depolarized to at least -60mV
- Massive influx of Na+ causes “rapid depolarization” phase
- Roughly at +30mV, Na+ channels inactivate, so blocked. K+ channels open, K+ exits. K+ causes “repolarization phase”
- K+ channels start to close slowly, excess K+ exits causing “hyperpolarization phase”. Membrane potential goes as low as -90 mV.
- All K+ channels close, membrane potential back at -70mV
