Neurophysiology L2: Neuronal Signals start as Local Potentials Flashcards
Where are local potentials?
All neurons are functionally similar
How are potentials generated through “generator potential”?
In summary, depolarisation –> activates Na2+ channels –> change in local potential –> if large enough, action potential generated –> spinal cord
How are potentials generated through light touch (stimulus) and how does that vary when the touch is harder for generator potentials?
- Lightly touch (afferent neuron fibres) –> receptors stimulated –> Na2+ channels deform –> open channels allows Na2+ to flow in –> local potential
- Touch harder –> more receptors stimulated –> Na2+ channels deform more –> open channels more –> more Na2+ flow in –> local potential –> if local potential is large enough, activated voltage-gated Na2+ channels –> action potential generated –> spinal cord
What is the threshold potential?
Minimum energy needed to activate voltage-gated Na2+ channels
What are the 3 ways that potentials can be generated?
- Generator potential
- Receptor potential
- Synaptic potential
How are potentials generated through “receptor potential”?
Brush against poison ivy (Stimulus) –> Mask cells release histamine (transmitter for sensory neurons) –> if enough histamine is released –> activates Na+2 channels –> change in potential –> action potential is generated
How are potentials generated through “synaptic potential”?
Synapse attaches to dentritic processes –> transmitter released –> activate glutamate-like receptors –> depolarization –> transfer to next cell
How do chemical synapses affect synaptic transmission for CNS?
- Glutamate- excitatory
- GABA- inhibitory
How do chemical synapses affect synaptic transmission for CNS?
- Acetylcholine- excitatory
- Acts on receptor –> receptor activates –> opens up ion channels (mainly Na2+) –> depolarization –> … –> initiates muscle contraction
How do chemical synapses affect synaptic transmission?
- Fast post -synaptic potentials
Local potentials can be _____ or _____.
excitatory (depolarisation); inhibitory (hyperpolarisation)
What is ENa?
Equilibrium for Na2+
- Allows ions to flow in/out –> +60 is ideal (no more ions will flow in or out)
What is the RMP?
Resting membrane potential
- Normal cell is at -70. More permeable to K+ than Na2+
What is EK?
Equilibrium for K+
- Allow ions to flow in/out -90 is ideal(no more ions will flow in or out)
How does depolarisation occur? Does it have an excitatory or inhibitory component?
Glutamate (excitatory) released –> allow Na2+ channels to open –> Na2+ flows in –> more positive –> channels close –> back to -70 = local potential
How does hyperpolarisation occur? Does it have an excitatory or inhibitory component?
GABA (inhibitory) released –> allow Cl- channels to open –> Cl- flows in –> more negative –> channels close –> back to -70 = local potential
A fat dendrite has _____ (increased/decreased) internal resistance. As a result that the current can follow _____ (more/less easily).
Decreased; more
A thin dendrite has _____ (increased/decreased) internal resistance. As a result that the current can follow _____ (more/less easily).
Increased; less
