Neurons: Cellular & Network Properties Flashcards

Vocabulary flashcards covering cellular anatomy, glial cell functions, membrane potential mechanisms, graded and action potentials, synaptic transmission, and neurotransmitter classifications.

Afferent Neurons

Sensory neurons that send information to the central nervous system (CNS) through sensory receptors.

Efferent Neurons

Neurons that convey output signals from the central nervous system to target cells via the efferent division of the peripheral nervous system (PNS).

Pseudounipolar Neurons

Sensory neurons featuring a single process called the axon, formed during development when the dendrite fused with the axon.

Bipolar Neurons

Neurons with two relatively equal fibers extending off the central cell body, involved in sensory transmission such as smell and vision.

Anaxonic Neurons

Central nervous system interneurons that have no apparent axon.

Multipolar Neurons

Neurons possessing multiple dendrites (typically five to seven branching four to six times) and a single long axon; includes typical efferent neurons and CNS interneurons.

Ependymal Cells

CNS glial cells that create barriers between compartments, line the brain ventricles, serve as a source of neural stem cells, and secrete cerebrospinal fluid (CSF) into ventricles when associated with the choroid plexus.

Astrocytes

Glial cells in the central nervous system that take up $\text{K}^+$, water, and neurotransmitters, help form the blood-brain barrier, secrete neurotrophic factors, and provide substrates for ATP production.

Microglia

Modified immune cells acting as scavengers in the central nervous system; they represent the only component of the immune system with access to the CNS.

Oligodendrocytes

CNS support cells that form myelin sheaths around axons and are capable of myelinating segments of more than one neuron.

Schwann Cells

Peripheral nervous system glial cells (neurolemmocytes) that form myelin sheaths around a single segment ($1\text{--}1.5\,\text{mm}$) of one axon and secrete neurotrophic factors.

Satellite Cells

Support cells in the PNS that surround and support neuron cell bodies outside the CNS in autonomic ganglia.

Node of Ranvier

A section of unmyelinated axon membrane between two Schwann cells that contains voltage-gated ion channels necessary for saltatory conduction.

Graded Potential

A variable-strength electrical signal generated in dendrites or cell bodies when gated channels open, which decreases in strength as it spreads through the cell over space and time.

Excitatory Post-Synaptic Potential (EPSP)

A depolarizing graded potential in the dendrites or cell body caused by the binding of excitatory neurotransmitters.

Inhibitory Post-Synaptic Potential (IPSP)

A hyperpolarizing graded potential in the dendrites or cell body caused by the binding of inhibitory neurotransmitters.

Trigger Zone

The region of a neuron (typically the axon hillock) where incoming graded potentials summate; if depolarization reaches a threshold voltage (typically $-55\,\text{mV}$), an action potential is initiated.

Action Potential

An all-or-none, regenerating electrical depolarization signal conducted along an axon when threshold membrane potential is achieved at the trigger zone.

Spatial Summation

The integration of simultaneous graded potentials originating from multiple presynaptic inputs across the surface area of a postsynaptic neuron.

Temporal Summation

The additive integration of sequential graded potentials arriving at the trigger zone close together in time from a high-frequency presynaptic stimulus.

Absolute Refractory Period

The period during an action potential when voltage-gated $\text{Na}^+$ channels are inactivated, preventing any stimulus from triggering a second action potential.

Relative Refractory Period

The period following an action potential where voltage-gated $\text{Na}^+$ channels have reset to closed but $\text{K}^+$ channels remain open, requiring a larger-than-normal stimulus to initiate a new action potential.

Saltatory Conduction

The rapid conduction of an action potential along a myelinated axon where electrical signals jump from one Node of Ranvier to the next.

Acetylcholine (ACh)

A neurocrine synthesized from acetyl CoA and choline that acts as an excitatory neurotransmitter at neuromuscular junctions and performs excitatory or inhibitory functions in the ANS and CNS.

Choline Acetyltransferase

The enzyme inside the axon terminal responsible for synthesizing acetylcholine from acetyl CoA and choline.

Acetylcholinesterase (AChE)

An inactivating enzyme present in the synaptic cleft that rapidly breaks down acetylcholine into choline and acetate.

Nicotinic Receptors

Ionotropic, chemically-gated monovalent cation channels ($\text{Na}^+$ influx, $\text{K}^+$ efflux) for acetylcholine that produce fast, excitatory responses.

Muscarinic Receptors

Metabotropic, G-protein coupled receptors for acetylcholine ($\text{M}_1\text{--}\text{M}_5$) located in the PNS and CNS that produce slow, excitatory or inhibitory responses.

Catecholamines

A category of monoamine neurocrines derived from the amino acid tyrosine, consisting of dopamine, norepinephrine, and epinephrine.

Adrenergic Receptors

G-protein coupled receptors that bind norepinephrine or epinephrine, classified into alpha ($\alpha_1, \alpha_2$) and beta ($\beta_1, \beta_2, \beta_3$) subtypes.

Glutamate

The main excitatory amino acid neurotransmitter used throughout the central nervous system, critical for strengthening neural circuits involved in learning and memory.

Gamma-Aminobutyric Acid (GABA)

The primary inhibitory amino acid neurotransmitter in the brain, synthesized as a derivative of glutamate.

Glycine

An amino acid that functions primarily as an inhibitory neurotransmitter within the spinal cord.