The Nervous System and Neuronal Excitability Lecture Review

Flashcards covering key vocabulary terms and definitions from the lecture notes on The Nervous System and Neuronal Excitability.

Nervous System

A body system responsible for integration, sensory input, and motor output, controlling body responses and activities.

Integration (Nervous System)

The process of sensory information, controlling all body responses and activities, and storing information within the nervous system.

Sensory Input (Nervous System)

The detection and monitoring of internal and external stimuli by the nervous system.

Motor Output (Nervous System)

The response caused in effectors like muscles and glands by the nervous system.

Central Nervous System (CNS)

Division of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

Division of the nervous system consisting of cranial and spinal nerves and sensory receptors.

Sensory/Afferent Division (PNS)

Functional subdivision of the PNS where receptors detect stimuli and neurons carry information TOWARDS the CNS.

Motor/Efferent Division (PNS)

Functional subdivision of the PNS where neurons carry impulses FROM the CNS to various target effectors.

Neurons

The functional units of the nervous system, capable of producing and conducting electrical signals, and releasing neurotransmitters.

Neuroglia (Glial Cells)

Support cells of the nervous system, including 4 types in the CNS and 2 types in the PNS.

Cell Body (Neuron)

The main part of a neuron containing a single nucleus, from which processes like axons and dendrites extend.

Axon Hillock

The thick base of the neuron's cell body where the axon originates and action potentials are initiated if threshold is reached.

Dendrites

Branched processes of a neuron that carry signals TO the cell body and are specialized for contact with other neurons.

Axon

A single, long process of a neuron that carries impulses AWAY from the cell body and branches at the end to form axon terminals.

Axon Terminals

Branches at the end of an axon that contain vesicles filled with neurotransmitter.

Sensory Neurons

Neurons that transmit information from the PNS to the CNS.

Interneurons

Neurons that interpret sensory information within the CNS and may elicit a response.

Motor Neurons

Neurons that transmit information from the CNS to the PNS, targeting effectors like muscles and glands.

Ganglion/Ganglia

A cluster of neuron cell bodies located in the PNS.

Nucleus/Nuclei (CNS)

A cluster of neuron cell bodies located in the CNS.

Nerve

A bundle of axons located in the PNS.

Tract

A bundle of axons located in the CNS.

Astrocytes

Star-shaped glial cells in the CNS that form the blood-brain barrier, provide structural support, and guide neuron development.

Oligodendrocytes

Glial cells in the CNS that form the myelin sheath around multiple axons, speeding nerve impulse conduction.

Microglia

Phagocytic glial cells in the CNS that engulf and clear away dead or damaged cells, debris, and pathogens.

Ependymal Cells

Glial cells in the CNS that form an epithelial layer lining chambers and canals and produce cerebrospinal fluid (CSF).

Satellite Cells

Flat glial cells in the PNS that surround cell bodies in ganglia, providing support and protection.

Schwann Cells

Glial cells in the PNS that wrap around axons and produce a myelin sheath.

Myelination

The process by which cells (oligodendrocytes in CNS, Schwann cells in PNS) wrap tightly around axons, forming a myelin sheath that acts as an electrical insulator and speeds nerve impulse conduction.

Myelin Sheath

A fatty layer formed by glial cells that insulates axons and significantly increases the speed of electrical signal transmission.

Nodes of Ranvier

Unmyelinated gaps along an axon between myelinating cells, where the axon membrane is in contact with the extracellular fluid.

Multiple Sclerosis (MS)

An autoimmune disease involving the loss of myelin sheaths in CNS neurons, impairing neural function.

Guillain-Barre Syndrome

An autoimmune disease involving the loss of myelin sheaths in PNS neurons, impairing neural function.

Excitable Cells

Cells, such as neurons and muscle cells, that can change their membrane potential when adequately stimulated to create an electrical signal.

Membrane Potential

The difference in electrical charge across the cell membrane, measured as a voltage.

Resting Membrane Potential (RMP)

The membrane potential of a cell at rest, typically between -50mV to -100mV for various cells, and about -70mV for neurons, where the inside is negatively charged relative to the outside.

Na+/K+ Pumps

Active transport proteins that maintain the concentration gradients of Na+ and K+ across the cell membrane by pumping 3 Na+ out and 2 K+ in, thus maintaining the RMP.

Leakage Channels

Non-gated ion channels that are always open, allowing for a continuous slow leak of ions across the membrane.

Gated Channels

Ion channels that must be stimulated to open or close, categorized into ligand-gated, voltage-gated, and mechanically-gated types.

Ligand-Gated Channels

Gated ion channels that open when a specific chemical (ligand) binds to them and close when the ligand is absent.

Voltage-Gated Channels

Gated ion channels that open and close in response to changes in the membrane potential (voltage).

Mechanically-Gated Channels

Gated ion channels that open and close in response to mechanical forces such as pressure, touch, stretch, or vibration.

Graded Potentials

Changes in the membrane potential away from the RMP, occurring at dendrites or cell bodies of neurons, whose strength depends on the strength of the stimulus and can summate.

Depolarization (Graded Potential)

A change in membrane potential where the inside of the cell becomes less negative than the RMP.

Hyperpolarization (Graded Potential)

A change in membrane potential where the inside of the cell becomes even more negative than the RMP.

Summation (Graded Potentials)

The process where multiple graded potentials can be added together to produce a larger change in membrane potential.

Decremental Spread

The characteristic of graded potentials where their strength deteriorates as they travel along the membrane.

Postsynaptic Potential

A type of graded potential occurring in a second neuron, caused by a first neuron.

Receptor Potential

A type of graded potential where a neuron acts as a receptor for sensory information in the PNS.

Endplate Potential

A type of graded potential found on a skeletal muscle cell.

Action Potential (AP)

A rapid set of electrical events, an 'all-or-nothing' phenomenon, starting in the axon hillock and spreading down the axon, resulting in neurotransmitter release.

Trigger Zone

The area in the axon hillock where action potentials are initiated if the graded potential reaches the threshold voltage.

Threshold Voltage

The specific membrane potential (typically -55mV in neurons) that must be reached for an action potential to be generated.

All-or-None Phenomenon

The characteristic of action potentials to either occur completely if the threshold is met, or not at all if it's not, with all APs being identical in strength and duration.

Resting Stage (Action Potential)

The initial phase of an action potential where the neuron is at its resting membrane potential (-70mV) with gated Na+ and K+ channels closed.

Depolarizing Phase (Action Potential)

The phase of an action potential during which the membrane potential rapidly rises (to +30mV) due to the influx of Na+ ions through many open voltage-gated Na+ channels.

Repolarizing Phase (Action Potential)

The phase of an action potential during which the membrane potential falls back toward the resting potential due to the efflux of K+ ions through open voltage-gated K+ channels and inactivation of Na+ channels.

Hyperpolarizing Phase (Action Potential)

The phase following repolarization where some K+ channels are still open, causing the membrane to briefly become even more negative than the RMP before returning to rest.

Saltatory Conduction

The mode of action potential conduction in myelinated axons where the AP 'jumps' from one Node of Ranvier to the next, significantly speeding up impulse transmission (10-50x faster).

Synapse

A specialized junction that allows communication between a neuron and another cell, such as another neuron or an effector cell (e.g., muscle).

Presynaptic Neuron

The neuron that transmits a signal TOWARDS a synapse.

Postsynaptic Neuron/Cell

The neuron or effector cell that receives a signal FROM a synapse.

Neurotransmitter (NT)

Chemical messengers released by neurons at synapses to transmit signals to other neurons or effector cells.

Acetylcholine (ACh)

A common neurotransmitter used in the CNS and PNS (neuron-muscle cells), which can be excitatory or inhibitory and is quickly deactivated by Acetylcholinesterase.

Acetylcholinesterase (AChE)

An enzyme that quickly deactivates (breaks down) Acetylcholine after its release at a synapse.

Monoamine Family (Biogenic Amines)

A family of neurotransmitters, mostly found in the CNS, including Dopamine, Serotonin, Histamine, Epinephrine, and Norepinephrine, broken down by Monoamine oxidase.

Dopamine

A neurotransmitter belonging to the monoamine family, primarily active in the CNS.

Serotonin

A neurotransmitter belonging to the monoamine family, primarily active in the CNS.

Epinephrine (Adrenaline)

A neurotransmitter and hormone belonging to the monoamine family, also found in the adrenal gland.

Norepinephrine (NE)

A neurotransmitter belonging to the monoamine family, active in both the CNS and PNS.

Monoamine Oxidase (MAO)

An enzyme that breaks down and deactivates neurotransmitters of the monoamine family.

Neural Circuits

Complex interactions formed by multiple neurons, which can enhance or inhibit neural activity in the CNS or body.

Diverging Circuits

A type of neural circuit where a single presynaptic neuron synapses with several postsynaptic neurons, stimulating multiple pathways simultaneously.

Converging Circuits

A type of neural circuit where a postsynaptic neuron receives action potentials from several different sources, increasing the effectiveness of summation.

Reverberating Circuits

A type of neural circuit where downstream neurons synapse with earlier ones, sending action potentials back through the circuit repeatedly.

Parallel After-Discharge Circuits

A type of neural circuit where a single presynaptic cell stimulates a group of neurons, each synapsing with a common postsynaptic cell at different times, creating a continuous input to the target.