A & P Chapter 17

Dendrites

a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body.

Axon Hillock

a specialized part of the cell body (or soma) of a neuron that connects to the axon. The last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.

Ganglia

a structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber.

Collaterals

a subordinate or accessory part.

Nerve fiber

a threadlike extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system.

Ependymal cells

a type of glial cell. These cells line the CSF-filled ventricles in the brain and the central canal of the spinal cord. The cells are ciliated simple columnar epithelium-like cells.

Oligodendrocytes

a type of neuroglia. Their main functions are to provide support and insulation to axons in the central nervous system of some vertebrates, equivalent to the function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by creating the myelin sheath, which is 80% lipid and 20% protein.

Unipolar neurons

a type of neuron in which only one protoplasmic process (neurite) extends from the cell body.

Dorsal Root Ganglion with sensory neurons & satellite cells

(also known as a posterior root ganglion), is a cluster of nerve cell bodies (a ganglion) in a posterior root of a spinal nerve.

Neurofibrils

a fibril in the cytoplasm of a nerve cell, visible by light microscopy.

Nuclei

Multiple for nucleus- a brain structure consisting of a relatively compact cluster of neurons

Synapses

a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Tracts

a bundle of nerve fibers having a common origin, termination, and function.

Fascicles

a bundle of structures, such as nerve or muscle fibers.

Cell body

The part of a neuron containing the nucleus but not incorporating the axon and dendrites. Also called soma.

Multipolar neurons

a type of neuron that possesses a single (usually long) axon and many dendrites, allowing for the integration of a great deal of information from other neurons. These dendritic branches can also emerge from the nerve cell body. Constitute the majority of neurons in the brain and include motor neurons and interneurons.

Bipolar neurons

a type of neuron which has two extensions. Specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions.

Nissl bodies

also known as Nissl substance, is a large granular body found in neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis.

Axons

also known as a nerve fibre, is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. The function of the axon is to transmit information to different neurons, muscles and glands.

Nodes of Ranvier

also known as myelin sheath gaps, are the gaps (approximately 1 micrometer in length) formed between the myelin sheaths generated by different cells

Neurons

an electrically excitable cell that processes and transmits information through electrical and chemical signals.

Purkinje cells of Cerebellar Cortex

are a class of GABAergic neurons located in the cerebellum.

Schwann cells

are a type of "support" cell in the PNS. Some important points- they insulate (myelinate) individual nerve fibers (axons), which is necessary for sending appropriate electrical signals throughout the nervous system.

Microglia

are a type of glial cell that are the resident macrophages of the brain and spinal cord, and thus act as the first and main form of active immune defense in the central nervous system (CNS).

Pyramidal Cells of Cerebral Cortex

are a type of neuron found in areas of the brain including the cerebral cortex

Astrocytes

are characteristic star-shaped glial cells in the brain and spinal cord.

Neurotransmitter

are endogenous chemicals that transmit signals across a synapse from one neuron (nerve cell) to another "target" neuron

Neuroglia

are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the central nervous system and peripheral nervous system

Satellite cells

are precursors to skeletal muscle cells.

Axon terminals

are specialized to release the electrical impulse of the presynaptic cell.

Motor/ efferent neurons

carry nerve impulses away from the central nervous system to effectors such as muscles or glands (and also inner hair cells of the mammalian inner ear). The term can also be used to describe relative connections between nervous structures (for example, a neuron's efferent synapse provides input to another neuron, and not vice versa).

Sensory/ afferent neurons

carry nerve impulses from receptors or sense organs toward the central nervous system. This term can also be used to describe relative connections between structures. Communicate with specialized interneurons.

Mixed nerves

contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Myelin

is a dielectric (electrically insulating) material that forms a layer

Endoneurium

is a layer of delicate connective tissue around the myelin sheath of each myelinated nerve fiber. Its component cells are called endoneurial cells.

Association/ Interneurons

is one of the three classifications of neurons found in the human body. Interneurons create neural circuits, enabling communication between sensory or motor neurons and the central nervous system (CNS).

Epineurium

is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve.

Neurilemma

is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system

CNS

is the part of the nervous system consisting of the brain and spinal cord

PNS

is the part of the nervous system that consists of the nerves and ganglia outside of the brain and spinal cord. The main function is to connect the central nervous system (CNS) to the limbs and organs, essentially serving as a communication relay going back and forth between the brain and the extremities

Myelinated fibers

make up the myelin sheath

Synaptic vesicles

store various neurotransmitters that are released at the synapse.

Nerves

the axon of a neuron. A nerve is formed of a bundle of many such fibers, with their sheaths.

Neuroplasm

the cytoplasm of a nerve cell

Perineurium

the sheath of connective tissue surrounding a bundle (fascicle) of nerve fibers within a nerve.

Synaptic cleft

the space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter—called also synaptic gap

Myelin sheath

usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. It is an outgrowth of a type of glial cell.