Neurophysiology Pt 3 Quiz

Neurophysiology: General Info

• Neurons are the core components of the brain, spinal cord, and nerves.
• Dendrites integrate incoming information and decide if an action potential will be produced by the neuron.
• Dendritic spines are small membranous protrusions that cover dendrites, allowing them to communicate with up to hundreds of axons.
• Axons can range from a few micrometers to 10 meters long, containing the majority of the cellular cytoplasm and various organelles.
• Axonal proteins are synthesized by the soma and transported to the axon.

En Passante Synapses

• En Passante synapses are interfaces where the electrical signal passes by to the axon terminal.
• Axosecretory synapses are interfaces where the axon terminal secretes directly into the bloodstream.

Axoplasmic Transport

• Anterograde transport is related to synaptic components, such as the flow of synaptic vesicles and mitochondria.
• Conventional neurotransmitters include small molecule (amino acids, amines, purines) and large molecule (endorphins, neuropeptide Y) neurotransmitters.
• Unconventional neurotransmitters, such as endocannabinoids and gasotransmitters, do not require receptors and can cross the cell membrane.

Neurotransmitter Examples

• Adrenaline stimulates the fight or flight response.
• GABA stimulates a calming response.
• Acetylcholine stimulates learning.
• Glutamate stimulates memory.
• Endorphins stimulate the feeling of euphoria.
• Serotonin impacts overall mood by helping with sleep cycles and contributing to a feeling of happiness.
• Dopamine stimulates the feeling of pleasure.
• Noradrenaline stimulates concentration.

Neurotransmitter Actions

• The action of a neurotransmitter in the postsynaptic membrane depends on receptor proteins.
• Ionotropic receptors directly gate ion channels.
• Cation channels are opened by excitatory neurotransmitters and induce depolarization.
• Anion channels are opened by inhibitory neurotransmitters and induce hyperpolarization.
• Metabotropic receptors act through second messenger systems.
• GPCR (G protein coupled receptors) are examples of metabotropic receptors.

Depolarization and Hyperpolarization

• Depolarization shifts the membrane potential to be more positive in charge, typically involving excitatory neurotransmitters opening cation channels.
• EPSP (Excitatory postsynaptic potentials) are involved in depolarizing graded potentials, driving the membrane potential towards threshold.
• Hyperpolarization shifts the membrane potential to be more negative in charge, typically involving inhibitory neurotransmitters opening anion channels.
• IPSP (Inhibitory postsynaptic potentials) are involved in hyperpolarizing graded potentials.

Action Potential Generation

• Action potentials are generated by the integration of graded potentials at the axon hillock.
• The threshold potential is defined as the minimum voltage required to trigger an action potential, typically occurring at -55 millivolts.
• Action potentials are generated by the steps of: (1) receiving inputs from presynaptic neurons, (2) triggering graded potentials, (3) integrating graded potentials at the axon hillock, and (4) propagating the action potential along the axon.

Graded Potential Summation

• Numerous presynaptic axons converge on a postsynaptic neuron, generating thousands of IPSPs and EPSPs.
• The axon hillock processes graded potentials through algebraic processing of adding or subtracting potential charges.
• Graded potentials can be involved in either spatial summation or temporal summation.
• Spatial summation involves the summation of graded potentials from different synapses.
• Temporal summation involves the summation of successive discharges from a single presynaptic terminal.