L.2.2 - The Nervous System

Neuron

Nerve cell and basic building block of the nervous system.

Soma / Cell Body

Provides life support for the neuron.

Dendrites

Branch-like structures that receive messages and carry them toward the soma.

Axon

Long extension that transmits electrical impulses away from the cell body.

Myelin Sheath

Fatty protective layer that insulates an axon and speeds up message transmission.

Synapse

Contact/communication point between neurons.

Endorphins

Neurotransmitters associated with pain control and pleasure.

Amitotic

Neurons lose the ability to divide after becoming specialized.

Multipolar Neuron

Neuron with three or more processes; about 99% of neurons.

Bipolar Neuron

Neuron with two processes; found in special sensory locations such as the retina.

Unipolar Neuron

Neuron with one process; mostly found in sensory receptors.

Sensory Neuron

Afferent neuron that carries information from sensory receptors toward the CNS.

Motor Neuron

Efferent neuron that carries information from the CNS to the rest of the body.

Interneuron

Association neuron that connects sensory and motor neurons.

Sensory Input

Detecting information from the environment/body.

Integration

Processing sensory information and deciding what to do.

Motor Output

Activating parts of the body to produce a response.

Central Nervous System (CNS)

Brain and spinal cord; main control center.

Peripheral Nervous System (PNS)

Nerves branching from the brain and spine that connect the CNS to the rest of the body.

Sensory Division / Afferent

Carries sensory information toward the CNS.

Motor Division / Efferent

Carries commands away from the CNS to muscles and glands.

Somatic Nervous System

Voluntary system controlling skeletal muscle movement.

Autonomic Nervous System

Involuntary system controlling functions such as heartbeat, breathing, and stomach activity.

Sympathetic Division

Mobilizes the body into action.

Parasympathetic Division

Relaxes the body.

Astrocytes

CNS glial cells that are abundant and versatile and exchange materials between neurons and capillaries.

Microglial Cells

CNS glial cells that provide immune defense against invading microorganisms.

Ependymal Cells

CNS glial cells that create, secrete, and circulate cerebrospinal fluid.

Oligodendrocytes

CNS glial cells associated with producing myelin sheaths.

Satellite Cells

PNS glial cells that surround and support neuron cell bodies.

Schwann Cells

PNS glial cells that produce insulating myelin sheaths.

Electrical Impulse

Signal that travels down a neuron's axon when the neuron is sufficiently stimulated.

Current

Flow of positively or negatively charged ions across the cell membrane.

Sodium-Potassium Pump

Moves 3 sodium ions out and 2 potassium ions in.

Ion Channels

Proteins that provide pathways for ions to cross the cell membrane.

Voltage-Gated Channels

Open and close in response to changes in membrane potential.

Ligand-Gated Channels

Open when a neurotransmitter attaches to its receptor.

Mechanically-Gated Channels

Open when the membrane is physically stretched.

−55 mV

Threshold associated with the all-or-nothing phenomenon.

All-or-Nothing Phenomenon

A neuron fires when stimulation reaches the required threshold.