Nervous System I: Organization & Signaling

Flashcards covering the organization, support cells, neuron structure, and signaling mechanisms of the nervous system.

Sensory input

The gathering of information to monitor changes occurring inside and outside the body.

Stimuli

Changes occurring inside and outside the body detected by sensory input.

Integration

The process of interpreting sensory input and deciding if action is needed.

Motor output

A response to integrated stimuli that activates muscles or glands.

Central nervous system (CNS)

The structural classification consisting of the brain and spinal cord.

Peripheral nervous system (PNS)

Nerves outside the brain and spinal cord, including spinal nerves and cranial nerves.

Sensory (afferent) division

Nerve fibers that carry information toward the central nervous system.

Motor (efferent) division

Nerve fibers that carry impulses away from the central nervous system.

Somatic nervous system

A subdivision of the motor division that is voluntary and controls skeletal muscles.

Autonomic nervous system

An involuntary subdivision of the motor division that controls cardiac muscle, smooth muscle, and glands.

Neuroglia

A group of support cells in the CNS meant to support, insulate, and protect neurons.

Astrocytes

Abundant, star-shaped cells that brace neurons, form a barrier between capillaries and neurons, and control the chemical environment of the brain.

Microglia

Spiderlike phagocytes in the CNS that dispose of debris.

Ependymal cells

Support cells that line cavities of the brain and spinal cord to circulate cerebrospinal fluid.

Oligodendrocytes

Support cells that wrap around nerve fibers in the central nervous system to produce myelin sheaths.

Satellite cells

PNS support cells that protect neuron cell bodies.

Schwann cells

PNS support cells that form myelin sheaths in a jelly roll-like fashion.

Neurons

Nerve cells specialized to transmit messages.

Cell body

The nucleus and metabolic center of the neuron.

Dendrites

Neuron processes that conduct impulses toward the cell body.

Axons

Neuron processes that conduct impulses away from the cell body.

Synaptic cleft

The gap located between adjacent neurons.

Synapse

The junction between nerves.

Myelin sheath

A whitish, fatty material covering axons.

Nodes of Ranvier

Gaps in the myelin sheath along the axon.

Proprioceptors

Sensory receptors that detect stretch or tension.

Interneurons

Also known as association neurons, these are found in the CNS and connect sensory and motor neurons.

Multipolar neurons

A structural classification for neurons having many extensions from the cell body.

Bipolar neurons

A structural classification for neurons with one axon and one dendrite.

Unipolar neurons

Neurons that have a short single process leaving the cell body.

Irritability

The functional property describing the ability to respond to stimuli.

Conductivity

The functional property describing the ability to transmit an impulse.

Polarized

The state of a resting neuron's plasma membrane where fewer positive ions are inside the cell than outside.

Depolarization

The process where a stimulus changes membrane permeability, allowing sodium ($Na^+$) to flow inside the membrane.

Action potential

A nerve impulse that, once started, is propagated over the entire axon.

Repolarization

The event where potassium ($K^+$) ions rush out of the neuron after sodium ions rush in, restoring the negative charge on the inside.

Sodium-potassium pump

A protein pump using ATP that restores initial ionic conditions by ejecting $3$ sodium ($Na^+$) ions for every $2$ potassium ($K^+$) ions carried back into the cell.

Neurotransmitter

Chemicals released from a nerve's axon terminal into the synaptic cleft to stimulate the dendrite of the next neuron.