Lecture 1 - Neurophysiology Flashcards
What part of the brain is specific to mammals?
Neocortex
What is the function of glial cells?
To provide supportive care to neurons
What is characteristic of the neocortex?
- 6 layer structure
- Grooves (sulci) and folds (gyri) help to increase SA (greater # of neurons)
What are the 4 divisions of the neocortex?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
Which part of the neocortex is responsible for communication?
Temporal lobe - variable in animals
How many pairs of spinal nerves are there in dogs?
36
What is the difference between an afferent neuron and an efferent neuron?
Afferent -> spinal cord
Efferent <- spinal cord
What is the typical resting membrane potential (RMP) of neurons?
Between -60mV to -70mV
What are the concentrations of ions outside the neuron at RMP?
Low K+
High Na+
High Cl-
What are the concentrations of ions inside the neuron at RMP? Organic ions?
High K+
Low Na+
Low Cl-
High OA- (proteins)
What regulates the RMP?
- K+ leak channels
- Na+/K+ ATPase
- Negative proteins
Where does the driving force want K+ to move?
Out of the neuron
Where does the electrical force want K+ to move?
Stay inside the neuron
What are the two main types of passive transport channels?
- Ligand gated channels
- voltage gated channels
At what potential do voltage-gated sodium channels open?
-50mv to -55mV
What are the characteristics of an action potential?
- All or none
- Threshold potential of -50mV
- Same magnitude regardless of stimulus
- Travels in one direction along axon
- Has a refractory period
- Cannot be summed
- Amplitude does not diminish
What happens during depolarization?
An influx of Na+ into the axon through VG channels
What happens at the peak of an action potential?
Na+ channels close and K+ channels open
What happens during repolarization?
K+ flows out of the cell
What happens during hyperpolarization (refractory period)?
Channels are closed and non-functional during absolute RF, Na+ VG channels are closed but functional during relative RF.
What are characteristics of a graded potential?
- No refractory period
- Amplitude diminishes
- Summed over time and space
- Amplitude is proportional to stimulus
- Happen in membrane of soma
- Can be inhibitory or excitatory
Where are action potentials initiated?
axon hillock
Why do action potentials only propagate forward?
Because of the refractory period (hyperpolarization)
What is the rate of action potential propagation determined by?
- Axon diameter (bigger = faster)
- Myelin sheath (more = faster)
What are graded potentials?
Small fluctuations in membrane potential due to the opening of ion channels. Causes membrane to reach threshold and trigger action potential
What can a graded potential be triggered by?
Input from other neurons (synaptic release)
How does synaptic release occur?
- Depolarization reaches synapse
- Ca2+ channels open and Ca2+ flows in
- Ca2+ triggers vesicular fusion to membrane and releases neurotransmitters into synaptic cleft
- NT stimulates dendrites of next neuron
- NT’s are re-uptaken by transporters or metabolized
What are the 3 amino acid neurotransmitters?
- Glutamate
- Glycine
- GABA
What are ionotropic receptors and what do they do?
Ligand-gated ion channels. A NT binds to the channel and it opens to allow movement of ions. Channels are specific to specific NT’s. Signal quickly.
What are metabotropic receptors?
Receptors linked to an ion channel through a signalling cascade involving secondary messengers. Has a slower and prolonged effect. G-protein coupled receptor.
What is the most abundant neurotransmitter?
Glutamate (excitatory)
-> Ionotropic and metabotropic
What is the major inhibitory neurotransmitter of the brain?
GABA
-> Ionotropic and metabotropic
What is the major inhibitory neurotransmitter of the spinal cord?
Glycine
-> ionotropic only
