Lecture 4 - Introduction to the Nervous System Flashcards
What are the four main types of cells in the brain and what are their basic function?
- Neurons - Excitable
- Microglia - Immune
- Astrocytes - provides nutrients, support, BBB
- Oligodendrocytes - myelination
Define
Excitable cells
Cells that can be electrically excited resulting in the generation and propagation of action potentials
Ex. neurons, cardiac, skeletal muscles cells, endocrine cells
Define
Non-excitable cells
Cells that are unable to generate and propagate an action potential or respond to electrical stimuli
Ex. kidney cells, adipocytes, skin cells, RBCs, microglia
Most FDA approved drugs target receptors where?
Neurons
a few in microglia and astrocytes
List the types of voltage-gated ion channels in the brain
- Sodium
- Potassium
- Calcium
List the types of ligand-gated ion channels in the brain
- Nicotinic acetylcholine receptors
- GABAA receptors
- NMDA, AMPA, and kainate types of glutamate receptors
- 5-HT3 receptors
- Gylcine receptors
What are the two other types of ion channels that can be found in the brain?
- Mechanosensitive ion channels
- Thermosensitive ion channels
What is the resting membrane potential of neurons?
-65 mV to -75 mV
What ions are in higher concentration INSIDE of neurons at resting potential?
K+
What ions are in higher in concentration OUTSIDE of neurons at resting potential?
Na+, Cl-, Ca2+
What are the basic steps in neural communication?
- Stimuli are recieved by the dendrites and cell body
- Synaptic stimuli are summed at the axon hillock where action potential is triggered if the sum of arriving signals is enough
- Action potentials are conducted to the axon terminal
- Release of neurotransmitters into the synaptic cleft
- Neurotransmitters bind to receptors in the postsynaptic cell membrane to create a new signal
Define
Action potential
The robust and quick change in membrane potential, associated with the passage of an impulse along the membrane of a neuron or muscle cell
Define
Hyperpolarization
when the membrane potential becomes more negative at a particular spot on the
neuron’s membrane
Define
Depolarization
When the membrane potential movesaway from resting potential and closer to the positive
What happens after the membrane potential depolarizes past the threshold of excitation?
Voltage-gated Na+ channels open and allow Na+ to enter the cell quickly
K+ channels open more slowly to release K+ out of the cell
At about what voltage do the Na+ channels close and K+ channels stay open?
+40 mV
What causes the refractory period in neurons?
Hyperpolarization after an overshoot of K+ ions leaving the cell
How does the cell return to resting potential?
With the assistance of Na+-K+ pumps
Where is there a buildup of + charge inside the axon and - charges outside the axon?
At the nodes of ranvier
Define
Saltatory conduction
Allows eletrical nerve signals to be propagated long distances at high rates without any degradation of signal
Common steps in Synaptic Transmission
- Neurons synthesizes neurotransmitters and stores them in vesicles
- Action potential traveling down the neuron depolarizes the presynaptic nerve ternimal
- Membrane depolarization activates voltage-dependent Ca2+channels allowing entry into the neuron
- Cytosolic Ca2+ enables vesicle fusion with the plasma membrane and releases the neurotransmitter
- Neurotransmitter binds to ionotropic receptors and metabotropic receptors
- Neurotransmitters are recycled by reuptake transporters or degraded by enzymes to terminate signal
- Enzymes such as phosphodiesterases degrade postsynaptic intracellular signalling molecules
Define
Neurotransmitters
Endogenous substances that transmit nerve impulses across synapses
What are the key neurotransmitters?
- Glutamate (excitatory)
- glycine and GABA (inhibitory)
List some of the amino acid derivatives that also modulate neuronal function
Dopamine, noepinephrine, histamine, adenosine, serotonin
