Nervous System Part 1 - Chapter 8 Review

This set of vocabulary flashcards covers the organization, cell types, electrical properties, and communication mechanisms of the nervous system as described in Chapter 8.

Central nervous system (CNS)

The division of the nervous system consisting of the brain and spinal cord.

Peripheral nervous system (PNS)

All the nervous tissue outside the central nervous system.

Sensory division

The division of the PNS that conducts action potentials from sensory receptors to the CNS.

Motor division

The division of the PNS that conducts action potentials to effector organs, such as muscles and glands.

Somatic nervous system

A part of the motor division that transmits action potentials from the CNS to skeletal muscles.

Autonomic nervous system

A part of the motor division that transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands.

Enteric nervous system

A special nervous system found only in the digestive tract.

Neurons

Nerve cells that receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs.

Glial cells

Supportive cells of the CNS and PNS that do not conduct action potentials but enhance neuron function and maintain tissue conditions.

Cell body

The part of a neuron containing a single nucleus.

Dendrite

A cytoplasmic extension from the cell body that usually receives information and transmits it to the cell body.

Axon

A single long cell process that leaves the cell body at the axon hillock to conduct sensory or motor signals.

Multipolar neurons

Neurons with many dendrites and a single axon, making up most CNS neurons and nearly all motor neurons.

Bipolar neurons

Neurons with two processes (one dendrite and one axon) located in sensory organs like the retina and nasal cavity.

Pseudo-unipolar neurons

Neurons with a single process extending from the cell body that divides into two branches functioning as a single axon.

Astrocytes

Major supporting cells in the CNS that form the blood-brain barrier and regulate signaling activity.

Ependymal cells

Cells that line the cavities in the brain containing cerebrospinal fluid.

Microglial cells

Cells that perform immune functions in the CNS by removing bacteria and cell debris.

Oligodendrocytes

Glial cells that provide myelin to axons of neurons in the CNS.

Schwann cells

Glial cells that provide myelin to axons of neurons in the PNS.

Myelin sheath

Specialized layers that wrap axons to provide insulation and prevent most ion movement across the cell membrane.

Nodes of Ranvier

Gaps in the myelin sheath occurring about every millimeter where ion movement can occur.

Multiple sclerosis

A disease of the myelin sheath that results in the loss of muscle function.

Gray matter

Groups of neuron cell bodies and dendrites with very little myelin.

White matter

Bundles of parallel axons with whitish myelin sheaths.

Leak channels

Ion channels that are always open, allowing ions to diffuse down their concentration gradient.

Gated channels

Ion channels that are closed until opened by specific chemical or electrical signals.

Resting membrane potential

The voltage across the membrane of a resting cell, characterized by a higher concentration of $K^+$ inside and $Na^+$ outside.

Sodium-potassium pump

A mechanism that actively transports $K^+$ into the cell and $Na^+$ out, consuming $70\%$ of the ATP in a neuron.

Action potential

Electrical signals conducted along the cell membrane used for cell communication.

Local current

The movement of $Na^+$ into the cell that causes the inside of the membrane to become positive.

Depolarization

A change in membrane potential where the inside of the cell membrane becomes positive relative to the outside.

Threshold

The level of depolarization required to trigger the opening of voltage-gated $Na^+$ channels and start an action potential.

Repolarization

The process where $K^+$ leaves the cell, restoring the negative charge on the inside of the membrane.

Hyperpolarization

A brief phase at the end of repolarization where the membrane potential becomes more negative than the resting potential.

All-or-none fashion

The principle that an action potential occurs completely if threshold is reached or not at all if it is not.

Continuous conduction

Action potential conduction that occurs along the entire membrane of unmyelinated axons.

Saltatory conduction

Action potential conduction in myelinated axons that occurs in a jumping pattern at the nodes of Ranvier.

Synapse

A junction where the axon of one neuron interacts with another neuron or an effector organ.

Presynaptic terminal

The end of an axon where neurotransmitters are stored in synaptic vesicles.

Neurotransmitters

Chemical substances like acetylcholine and norepinephrine that diffuse across the synaptic cleft to bind to receptors.

Acetylcholinesterase

An enzyme within the synaptic cleft that breaks down acetylcholine.

Converging pathway

A neuronal pathway where two or more neurons synapse with the same postsynaptic neuron.

Diverging pathway

A neuronal pathway where an axon from one neuron synapses with more than one postsynaptic neuron.

Spatial summation

The integration of local potentials that originate from different locations on the postsynaptic neuron.

Temporal summation

The integration of local potentials that overlap in time from a single rapidly firing input.