A&P 1 - Module 09 (Nervous Tissue)

Central Nervous System

The anatomical division of the nervous system comprised of the brain and spinal cord.

Peripheral Nervous System

The anatomical division of the nervous system comprised of the cranial nerves and spinal nerves.

Sensory (Afferent) Division (of the PNS)

The functional division of the nervous system responsible for transmitting sensory information from receptors in the body to the central nervous system.

Motor (Efferent) Division (of the PNS)

The functional division of the nervous system responsible for transmitting motor commands from the central nervous system to effectors such as muscles and glands.

Somatic Nervous System

The functional division of the nervous system that is responsible for conscious perception and the control of skeletal muscle.

Autonomic Nervous System

The functional division of the nervous system that is responsible for the control of cardiac and smooth muscle, as well as glandular tissue.

Sympathetic Division (of the ANS)

The division of the autonomic nervous system responsible for the 'fight, flight, or freeze' response, preparing the body for stressful or emergency situations.

Parasympathetic Division (of the ANS)

The division of the autonomic nervous system responsible for the 'rest and digest' response, promoting relaxation, digestion, and energy conservation.

Neuron

A nervous tissue cell with dendrites and an axon that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system.

Neuroglia

A group of nervous tissue cells responsible for supporting neurons.

Axon Hillock

The tapering of the neuron cell body that gives rise to the axon.

Initial Segment

The first part of the axon as it emerges from the axon hillock, where the action potential is generated.

Myelin Sheath

A lipid-rich layer of insulation around an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates a faster transmission of action potentials.

Node of Ranvier

The gaps between two myelinated regions of an axon, allowing for saltatory propagation of an action potential down the axon.

Pre-Synaptic Cell

A neuron that releases neurotransmitters from their axon terminal into the synaptic cleft to signal a target cell.

Post-Synaptic Cell

A neuron or other cell that receives neurotransmitters across a synapse and responds by generating a graded potential.

Anaxonic Neuron

A neuron with no distinct axon, where all neuronal processes appear similar, primarily found in the central nervous system.

Bipolar Neuron

A neuron with two processes extending from the neuron cell body (soma) - the axon and one dendrite.

Unipolar Neuron

A neuron that has only one process extending from the neuronal cell body (soma) that then splits to become both the axon and dendrite.

Multipolar Neuron

A neuron that has multiple processes - one axon and two or more dendrites; the most common neuronal cell shape.

Nuclei

A collection of neuron cell bodies in the central nervous system (singular, nucleus).

Ganglion

A collection of neuron cell bodies in the peripheral nervous system (plural, ganglia).

Tract

A bundle of axons in the central nervous system.

Nerve

A bundle of axons in the peripheral nervous system.

White Matter

A region of the nervous system containing mostly myelinated axons, making the tissue appear white.

Gray Matter

A region of the nervous system containing cell bodies of neurons with few or no myelinated axons.

Receptor

A specialized structure that is activated by specific environmental stimuli, initiating sensory signals in the nervous system.

Sensory Neuron

A neuron responsible for transmitting sensory information from receptors to the central nervous system.

Interneuron

A neuron located within the central nervous system that processes information and forms connections between sensory and motor neurons.

Motor Neuron

A neuron responsible for transmitting motor commands from the central nervous system to effectors such as muscles and glands.

Interoceptor

A sensory receptor that detects stimuli from within the body (i.e., changes in internal organs or blood pressure).

Proprioceptor

An interoceptor that detects body position and movement, located in muscles, tendons, and joints.

Exteroceptor

A sensory receptor that detects external stimuli (i.e., temperature, pressure, and light).

Ependymal Cell

A glial cell type in the CNS responsible for producing cerebrospinal fluid.

Microglia

A glial cell type in the CNS that is responsible for cleaning up cellular debris and protecting against pathogens.

Astrocyte

A glial cell type of the CNS that provides nutrient support for neurons and maintains the blood-brain barrier.

Oligodendrocyte

A glial cell type in the CNS that forms the myelin insulation for axons in tracts.

Schwann Cell

A glial cell type in the PNS that forms the myelin insulation for axons in nerves.

Satellite Cell

A glial cell type in the PNS that provides nutrient support and environmental regulation for neurons in the ganglia.

Chemically-Gated Channel

An ion channel that opens only when a specific chemical (ligand) is bound.

Voltage-Gated Channel

An ion channel that opens only when the local membrane potential reaches a specific voltage.

Mechanically-Gated Channel

An ion channel that opens only when a physical event (pushing, pulling, bending, stretching) directly alters the structure of the protein.

Graded Potential

A change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it; in neurons, located in the dendrites or cell body, and potentially resulting in the generation of an action potential at the initial segment.

Continuous Propagation

The slow propagation of an action potential along an unmyelinated axon.

Saltatory Propagation

The quick propagation of the action potential from node of Ranvier to node of Ranvier along a myelinated axon.

Excitatory Post-Synaptic Potential (EPSP)

A graded potential in the postsynaptic membrane that is the result of depolarization and makes an action potential more likely to occur.

Inhibitory Post-Synaptic Potential (IPSP)

A graded potential in the postsynaptic membrane that is the result of hyperpolarization and makes an action potential less likely to occur.

Temporal Summation

The combination of graded potentials received at the same location on the membrane but at different times resulting in an increase in signal strength and distance it is propagated.

Spatial Summation

The combination of graded potentials received at different locations along the membrane but at the same time resulting in an increase in signal strength and distance propagated.