L7. Structure of Nerve and Neuron Flashcards
Different neuron types?
- Multipolar - multiple local inputs at soma (motor neurons, CNS)
- Unipolar - dendrites distal from soma (sensory neurons)
- Anaxonic - no distinct axon (axonless, CNS neurons)
Neuronal communication?
Neuron to neuron, muscle to organs. Neurons are the communication wires within our body. Neurons transmit signals between different parts of our body (local, regional or long distance)
Pre-synaptic neuron?
Contains neurotransmitter vesicles, releases neurotransmitters, electrical to chemical conversion
Post-synaptic neuron?
Contains neurotransmitter receptors, chemical to electrical conversion
Dendrites?
Receives input (local potential), has chemically-gated ion channels (INPUT ZONE)
Cell body (soma)?
Receives input (local potential), has chemically-gated ion channels (INPUT ZONE)
Axon hillock?
Summates the local potentials to generate action potentials, has voltage-gated ion channels (INTEGRATION ZONE)
Axon?
Sends action potential down the axon, has voltage-gated ion channels (ACTION POTENTIAL)
Axon terminals?
Releases neurotransmitter to initiate a response in target cell, has voltage-gated ion channels (OUTPUT ZONE)
Bioelectricity - ion gradients and equilibrium?
Both can act simultaneously, and in the same or opposite direction. If they exactly balance, ions will stop moving = equilibrium
Equilibrium potential?
The membrane potential when two opposing forces of an ion are balanced
Resting membrane potential?
Is the combined permeabilities and gradients of all the ions involved in cells = approximately -70mV
ECF: sodium and potassium?
High Na+ = 142mM
Low K+ = 4mM
ICF: sodium and potassium?
High K+ = 150mM
Low Na+ = 12mm
Local potentials?
–> Small graded local changes depolarises or hyper-polarises the membrane to different levels (can cause action potential)
–> Does not propagate, amplitude decreases with distance - short distances - short distances
–> Temporal and spatial summation
–> Chemically-gated ion channels
Action potentials?
–> All or nothing in terms of action potential, either the same size action potential or no action potential at all. Depolarizes at same level (+30mV) each time.
–> Propagates down the axon without loss of amplitude so can do long distances
–> Voltage-gated ion channels
Neuronal input - chemically-gated Na+ channels?
Neurons can be pre-synaptic and post-synaptic
Neurotransmitters from the pre-synaptic cell binds to the receptor on the post-synaptic cell –> chemically-gated Na+ channels will open –> Na+ will flow into cell –> cause a local depolarisation
Excitatory vs inhibitory potentials?
Excitatory neurotransmitter (adrenaline/epinephrine) - Na+ enters neuron –> brings membrane potential closer to threshold (depolarising)
Inhibitory neurotransmitter (serotonin) - Cl- enters neuron –> moves the membrane potential away from threshold (hyper-polarising)
The structure of the input zone of a neuron is called:
A. Axon
B. Dendrites
C. Axon hillock
D. Synaptic terminals
B
An excitatory neurotransmitter moves the membrane potential:
A. away from threshold because Na+ enters the cell
B. away from threshold because K+ enters the cell
C. closer to threshold because Na+ enters the cell
D. closer to threshold because K+ enters the cell
C
