Neurophysiology, Neurotransmitters, and the Nervous System

Practice flashcards covering the basics of neurophysiology, including neuron anatomy, action potentials, synaptic transmission, brain structures, and neurotransmitter types.

Neurons

Excitable cells responsible for transmitting information, receiving sensory input, and controlling muscles and glands; there are roughly $100$ billion in the nervous system.

Glia

Support cells that provide structural support, protection, and energy to neurons, while also communicating via chemical transmission.

Dendrites

The part of the neuron designed to receive signals from other neurons.

Axon

The long extension of a neuron that carries the nerve impulse away from the cell body toward the axon terminals.

Myelin sheath

An insulating layer around the axon that helps speed up the conduction of the nerve impulse.

Nodes of Ranvier

Gaps in the myelin sheath where the action potential is regenerated.

Resting potential

The electrical charge of a neuron when it is not being stimulated, typically around $-70\,mV$.

Action potential

An all-or-nothing electrical signal generated at the axon hillock that travels down the axon to the terminal.

Depolarization

A change in the electrical charge of a neuron making it less negative (e.g., moving from $-70\,mV$ toward $-55\,mV$).

Hyperpolarization

A change in the electrical charge of a neuron that makes it even more negative than the resting potential.

Threshold of excitation

The specific voltage level (around $-55\,mV$) at which the resting potential breaks down and an action potential is triggered.

All-or-none law

The principle that action potentials are always the same strength and do not vary with the strength of the stimulus.

Rate law

The principle that the intensity of a stimulus is transmitted by variations in the rate at which action potentials fire.

Excitatory post-synaptic potential (EPSP)

Depolarization caused by the opening of voltage-gated $Na^+$ channels, bringing the cell closer to firing an action potential.

Inhibitory post-synaptic potential (IPSP)

Hyperpolarization caused by the opening of voltage-gated $K^+$ channels, making it more difficult for the cell to fire an action potential.

Temporal summation

The integration of post-synaptic potentials that occur in rapid succession at the same location.

Spatial summation

The integration of post-synaptic potentials that occur in close proximity to one another on a neuron.

Ionotropic receptor

A type of receptor associated with an ion channel that opens or closes immediately when a neurotransmitter binds to it.

Metabotropic receptor

A receptor linked to G-proteins that can trigger second messengers or open ion channels, typically involving slower and longer-lasting effects.

Autoreceptors

Receptors located on the presynaptic neuron that bind its own neurotransmitter to regulate and inhibit subsequent release.

Heteroreceptors

Presynaptic receptors that respond to chemicals released by the post-synaptic cell to regulate neurotransmitter release.

Reuptake

The most common method of terminating a signal, where neurotransmitters are taken back into the presynaptic neuron via transporters.

Deactivation

The process of terminating a signal where enzymes in the synapse break down the neurotransmitter.

Central nervous system (CNS)

The division of the nervous system consisting of the brain and spinal cord.

Peripheral nervous system (PNS)

All parts of the nervous system outside of the brain and spinal cord; it includes ganglia (cell bodies) and nerves (axons).

Somatic nervous system

A functional unit of the PNS made of sensory and motor nerves that allow interaction with the environment, primarily using acetylcholine.

Autonomic nervous system

The part of the PNS that regulates internal organ function and homeostasis, consisting of the sympathetic and parasympathetic systems.

Sympathetic nervous system

The 'fight or flight' system that prepares the body for sudden expenditures of energy in times of danger; uses adrenaline.

Parasympathetic nervous system

The 'rest and digest' system that maintains smooth internal functioning most of the time; uses acetylcholine.

Medulla oblongata

A hindbrain structure involved in the autonomic nervous system and containing the respiratory centre.

Locus coeruleus

An area in the pons containing the majority of norepinephrine neurons in the brain; associated with depression.

Cerebellum

The 'little brain' involved in motor coordination, fine muscle movements, and certain cognitive tasks.

Raphe nuclei

A midbrain structure that serves as an important source of serotonin in the brain.

Periaqueductal gray (PAG)

An area involved in pain sensation (analgesia) and defensive behaviour; contains many opioid receptors.

Substantia nigra

A midbrain structure that sends dopamine projections to the basal ganglia; deterioration is linked to Parkinson’s disease.

Ventral tegmental area (VTA)

A midbrain area that sends dopamine projections to cortical areas and is involved in the reward circuit.

Basal ganglia

A forebrain structure involved in voluntary movement, habit formation, and action selection; includes the nucleus accumbens.

Hippocampus

A part of the limbic system critical for learning, memory, and conditioned place preference.

Amygdala

A limbic system structure responsible for processing emotions such as fear, aggression, and anxiety.

Hypothalamus

The primary recipient of limbic input; it maintains homeostasis by controlling metabolism, sexual motivation, and hormonal balance.

Cortex

The most advanced part of the brain responsible for higher-order cognitive processes, including judgment and impulsivity (PFC).

Teratogens

Agents like thalidomide or alcohol that cause developmental dysfunction or malformations in a fetus.

Agonistic effects

Drug actions that facilitate the function of a specific neurotransmitter.

Antagonistic effects

Drug actions that impede or block the function of a specific neurotransmitter.

Acetylcholine (ACh)

The first discovered neurotransmitter; it plays roles in cognition in the CNS and autonomic/muscular function in the PNS.

Dopamine (DA)

A catecholamine synthesized from tyrosine/DOPA; implicated in learning, reward, addiction, and schizophrenia.

Glutamate

The major excitatory neurotransmitter in the brain; critical for learning and memory through NMDA receptors.

Gamma-aminobutyric acid (GABA)

The major inhibitory neurotransmitter in the brain; synthesized from glutamate by glutamic acid decarboxylase (GAD).

Positron emission tomography (PET)

An imaging technique using radioisotopes to measure brain distribution of drugs or active areas, though it has low resolution and high cost.

Functional magnetic resonance imaging (fMRI)

A high-resolution imaging technique that measures the BOLD signal to correlate brain activity with mental tasks.