Nervous Tissue – Quick Review

Vocabulary flashcards covering major terms from Chapter 12 on Nervous Tissue, including nervous system divisions, neuron structures and properties, axonal transport, neuroglia types, myelin, associated diseases, and nerve regeneration.

Nervous Tissue

Specialized tissue found in the brain, spinal cord, and nerves that conducts nerve impulses.

Central Nervous System (CNS)

Subdivision consisting of the brain and spinal cord, enclosed by the cranium and vertebral column.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS; composed of nerves and ganglia.

Nerve

Bundle of nerve fibers (axons) wrapped in fibrous connective tissue in the PNS.

Ganglion

Knot-like swelling along a nerve containing concentrated neuron cell bodies.

Sensory (Afferent) Division

PNS fibers that carry signals from receptors to the CNS.

Somatic Sensory Division

Sensory pathways carrying signals from skin, muscles, bones, and joints to the CNS.

Visceral Sensory Division

Sensory pathways transmitting signals from thoracic and abdominal viscera to the CNS.

Motor (Efferent) Division

PNS fibers that convey commands from the CNS to effectors.

Somatic Motor Division

Motor pathways that send signals to skeletal muscles.

Visceral Motor Division (Autonomic NS)

Motor system that sends signals to glands, cardiac, and smooth muscle.

Sympathetic Division

Autonomic branch that arouses the body (increases heart rate, respiration) and inhibits digestion/urination.

Parasympathetic Division

Autonomic branch that calms the body (slows heart rate) and stimulates digestion/urination.

Excitability

Neuron property of responding to environmental stimuli.

Conductivity

Ability of neurons to produce and transmit electrical signals.

Secretion

Release of neurotransmitter when an electrical signal reaches a neuron’s end.

Sensory Neuron

Neuron that conducts impulses from receptors toward the CNS.

Interneuron

Neuron entirely within the CNS that processes, stores, and relays information.

Motor Neuron

Neuron that conveys signals from the CNS to effectors such as muscles or glands.

Soma (Cell Body)

Control center of a neuron containing nucleus, organelles, and Nissl bodies; lacks centrioles.

Dendrite

Branched neuronal process that receives signals from other neurons.

Axon (Nerve Fiber)

Long process originating at the axon hillock that conducts impulses away from the soma.

Axon Hillock

Cone-shaped region of soma where the axon originates; part of the trigger zone.

Axoplasm

Cytoplasm of an axon.

Axolemma

Plasma membrane of an axon.

Terminal Arborization

Extensive branching at the distal end of an axon.

Synaptic Knob (Terminal Button)

Swelling at axon terminus containing synaptic vesicles of neurotransmitter.

Multipolar Neuron

Neuron with one axon and multiple dendrites; most common in CNS.

Bipolar Neuron

Neuron with one axon and one dendrite; found in retina, olfactory tissue, inner ear.

Unipolar Neuron

Neuron with a single process that splits into peripheral and central branches; sensory neurons to spinal cord.

Anaxonic Neuron

Neuron with many dendrites and no axon; found in retina, brain, adrenal gland.

Axonal Transport

Two-way movement of materials along an axon.

Anterograde Transport

Axonal movement from soma toward axon terminals.

Retrograde Transport

Axonal movement from axon terminals toward soma.

Fast Axonal Transport

Rapid (20–400 mm/day) transport of organelles, vesicles, enzymes, or pathogens.

Slow Axonal Transport

Slower (0.5–10 mm/day) anterograde movement of cytoskeletal and repair materials; sets nerve regeneration speed.

Neuroglia (Glial Cells)

Supportive cells that outnumber neurons ~10:1 and aid neuron function.

Oligodendrocyte

CNS glial cell that forms myelin sheaths around multiple axons.

Ependymal Cell

CNS glial cell lining brain cavities; secretes and circulates cerebrospinal fluid.

Microglia

Small wandering CNS macrophages that remove debris and pathogens.

Astrocyte

Most abundant CNS glial cell; forms blood-brain barrier, regulates ions, converts glucose to lactate, forms scar tissue (astrocytosis).

Schwann Cell

PNS glial cell that wraps around one axon to form its myelin sheath and aids regeneration.

Satellite Cell

PNS glial cell surrounding somas in ganglia; provides insulation and chemical regulation.

Myelin Sheath

Multilayered lipid covering formed by oligodendrocytes (CNS) or Schwann cells (PNS) that insulates axons and speeds conduction.

Nodes of Ranvier

Gaps between myelinated segments of an axon.

Internode

Myelin-covered segment between two nodes of Ranvier.

Neurilemma

Outermost coil of a Schwann cell containing its nucleus and cytoplasm.

Trigger Zone

Region including axon hillock and initial segment where action potentials begin.

Unmyelinated Nerve Fiber

Axon without myelin; in PNS several are nestled in grooves of one Schwann cell.

Conduction Speed Factors

Signal velocity increases with larger axon diameter and presence of myelin.

Blood–Brain Barrier

Tight seal between capillaries and astrocyte feet limiting substance passage into brain tissue.

Glioma

Rapidly growing, malignant brain tumor derived from glial cells.

Multiple Sclerosis (MS)

Autoimmune disease where CNS myelin and oligodendrocytes degenerate, causing neurological deficits.

Tay–Sachs Disease

Hereditary disorder causing GM2 glycolipid accumulation in myelin, leading to neural dysfunction and early death.

Nerve Fiber Regeneration

PNS axon regrowth if soma and some neurilemma survive; guided by regeneration tube formed by Schwann cells and basal lamina.

Regeneration Tube

Schwann cell, basal lamina, and neurilemma structure that directs regrowing axon sprouts to target.

Astrocytosis (Sclerosis)

Formation of hardened scar tissue by astrocytes after neuron damage.