Neurophysiology and Neurotransmitters Flashcards

Flashcards covering action and local potentials, synaptic mechanisms, neurotransmitters, and neuronal integration based on Chapter 1-8 lecture notes.

Absolute Refractory Period

The period during an action potential when a second action potential is completely impossible because the point of no return has been crossed.

Relative Refractory Period

The period while the membrane is repolarizing when a second action potential is possible, provided there is a strong external stimulus.

Depolarization

The phase of an action potential where the graph goes up, making the membrane potential less negative.

Repolarization

The phase of an action potential where the graph goes down, making the membrane potential more negative.

Local Potential

A potential characterized by graded strength that is reversible and weakens with distance.

Action Potential

An all-or-none, irreversible response that reaches approximately $+30\,mV$ and does not weaken as it travels down the axon.

Continuous Conduction

A slow mode of nerve impulse conduction that occurs when the myelin sheath is absent.

Saltatory Conduction

A fast mode of nerve impulse conduction occurring in myelinated axons, where impulses jump between gaps from node to node.

Nodes of Ranvier

The small gaps in the myelin sheath along an axon where depolarization occurs during saltatory conduction.

Multiple Sclerosis (MS)

A severe autoimmune disease characterized by the degradation of the myelin sheath in the central nervous system.

Autoimmune Disease

A condition in which the immune system gets confused and mistakenly recognizes the body's own tissues as foreign antigens.

Soma

The cell body of a neuron.

Axodendritic Junction

A synaptic junction formed between the axon of one neuron and the dendrite of another.

Axosomatic Junction

A synaptic junction formed between the axon of one neuron and the cell body (soma) of another.

Presynaptic Neuron

The neuron that sends the signal during synaptic transmission.

Postsynaptic Neuron

The neuron that receives the signal during synaptic transmission.

Synaptic Cleft

The communication gap between pre- and post-synaptic neurons, measuring between $20$ and $50\,nm$ wide in chemical synapses.

Electrical Synapses

Direct, fast, and bidirectional synapses where cells connect through gap junctions, allowing ions to flow directly with a delay of about $0.1\,ms$.

Chemical Synapses

Unidirectional synapses where electrical signals are converted to chemical signals stored in vesicles and released into the synaptic cleft.

Acetylcholine (ACh)

The main excitatory neurotransmitter at the neuromuscular junction (NMJ), which is degraded by acetylcholinesterase.

Excitatory Postsynaptic Potential (EPSP)

A local potential involving depolarization that moves the membrane closer to threshold and increases the likelihood of an action potential.

Inhibitory Postsynaptic Potential (IPSP)

A potential involving hyperpolarization that makes the membrane potential more negative and prevents an action potential from firing.

Temporal Summation

The process where rapid, successive signals sent from a single presynaptic neuron add together over time.

Spatial Summation

The process where simultaneous signals arriving from multiple presynaptic neurons add together across space onto a single neuron.

Reuptake

The process of transporting neurotransmitters back into the presynaptic neuron from the synaptic cleft so they can be reused or degraded.

Norepinephrine

A biogenic amine neurotransmitter that contributes to alertness, heart rate, and blood pressure.

Epinephrine

A biogenic amine neurotransmitter that acts as the body's fight-or-flight hormone.

Dopamine

A biogenic amine neurotransmitter associated with movement, reward, and motivation.

Serotonin

A biogenic amine neurotransmitter that regulates mood, sleep, and appetite.

Histamine

A biogenic amine neurotransmitter that promotes alertness and inflammation.

Glutamate

The main excitatory amino acid neurotransmitter in the central nervous system.

GABA

The major inhibitory amino acid neurotransmitter in the brain.

Substance P

A neuropeptide responsible for mediating pain sensations.

Endorphins

Neuropeptides naturally released during physical activity, such as exercise, that function to reduce pain.

Neuropeptide Y

A neuropeptide that regulates hunger and stimulates satiety, or the feeling of fullness.

Converging Circuit

A neuronal circuit where signals from multiple sensory neurons combine onto a single neuron to integrate input for motor control.

Synaptic Fatigue

A mechanism to protect against over-excitation wherein prolonged stimulation causes postsynaptic receptors to become less sensitive, weakening the overall response.