Nervous System Cells, Signaling, and Neuropathies

Vocabulary flashcards covering specialized nervous system cells, neuroglia, membrane mechanics, action potential phases, synaptic potentials, and neuropathies.

Sensory (Afferent) Neurons

Functional type of neurons that carry electrical and chemical signals to the Central Nervous System (CNS).

Motor (Efferent) Neurons

Functional type of neurons that carry electrical and chemical signals away from the CNS to muscles or glands.

Interneurons (Relay Neurons)

Neurons that connect sensory and motor pathways within the Central Nervous System (CNS).

Reflex Arc

The simplest neuronal network, which requires only a sensory neuron and a motor neuron (e.g., knee-jerk response).

Neuroglia

Support cells that assist and protect neurons so they can function efficiently.

Microglia

Support cells in the CNS responsible for immune defense and clearing cellular debris.

Astrocytes

Support cells in the CNS that form the blood-brain barrier and provide structural support.

Oligodendrocytes

Support cells that form myelin sheaths around axons in the Central Nervous System (CNS).

Schwann Cells

Support cells that form myelin sheaths around axons in the Peripheral Nervous System (PNS).

Satellite Cells

Support cells that support and protect cell bodies in the Peripheral Nervous System (PNS).

Leaky Channels

Membrane channels that allow small amounts of $Na^+$ and $K^+$ to diffuse constantly across the phospholipid bilayer.

Voltage-Gated Channels

Channel proteins that open and close exclusively in response to specific membrane voltages.

Sodium-Potassium Pump ($Na^+/K^+$ ATPase)

A membrane transport protein that uses ATP to pump $3\,Na^+$ out for every $2\,K^+$ pumped in, maintaining the negative interior charge of the neuron.

Resting Potential

The polarized membrane state at $-70\,\text{mV}$ where the inside of the neuron is negative relative to the outside, maintained by leaky channels and the $Na^+/K^+$ pump.

Depolarization to Threshold

The all-or-nothing phase where an incoming stimulus opens initial $Na^+$ channels; upon reaching the $-55\,\text{mV}$ threshold, voltage-gated $Na^+$ channels surge open, driving the voltage rapidly positive up to $+30\,\text{mV}$.

Repolarization

The action potential phase starting at $+30\,\text{mV}$ where $Na^+$ channels close and voltage-gated $K^+$ channels open, allowing $K^+$ to rush out and bringing the charge back toward resting level.

Absolute Refractory Period

The phase during repolarization when the neuron cannot fire another action potential, ensuring each signal is a distinct pulse and preventing signals from propagating backward up the axon.

Hyperpolarization

The action potential phase where slow-closing $K^+$ channels permit excess positive charge to exit, dropping the membrane voltage below resting level to $-77\,\text{mV}$.

Relative Refractory Period

The phase during hyperpolarization when a second action potential can fire, but requires a stronger stimulus to reach threshold.

EPSP (Excitatory Postsynaptic Potential)

A graded potential that causes local depolarization, moving the membrane potential closer to the threshold.

IPSP (Inhibitory Postsynaptic Potential)

A graded potential that causes local hyperpolarization, moving the membrane potential further from the threshold.

Summation

The temporal or spatial addition of multiple EPSPs and IPSPs that triggers an action potential if their net total reaches $-55\,\text{mV}$ at the axon hillock.

Multiple Sclerosis (MS)

An autoimmune disorder characterized by an attack on myelin sheaths in the Central Nervous System (CNS).

Guillain-Barré Syndrome

An autoimmune disorder characterized by an attack on myelin sheaths in the Peripheral Nervous System (PNS).

ALS (Amyotrophic Lateral Sclerosis)

A neuromuscular disorder characterized by the progressive degeneration of motor neurons.