Neural Tissue and Central Nervous System Lecture Review

A comprehensive set of vocabulary flashcards covering the histology, physiology, and anatomy of the nervous system and CNS as detailed in the provided lecture notes.

Sensory input

Information gathered by sensory receptors about internal and external changes.

Integration

The process of interpretation of sensory input within the nervous system.

Motor output

Activation of effector organs, such as muscles and glands, to produce a response.

Central nervous system (CNS)

Division consisting of the brain and spinal cord, serving as the integration and command center.

Peripheral nervous system (PNS)

Division consisting of paired spinal and cranial nerves that carry messages to and from the CNS.

Somatic afferent fibers

Fibers within the sensory division of the PNS that convey impulses from skin, skeletal muscles, and joints.

Visceral afferent fibers

Fibers within the sensory division of the PNS that convey impulses from visceral organs.

Somatic nervous system

The somatic motor (voluntary) division that conducts impulses from the CNS to skeletal muscles.

Autonomic nervous system (ANS)

The visceral motor (involuntary) division that conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands.

Sympathetic division

A branch of the ANS that mobilizes body systems during activity.

Parasympathetic division

A branch of the ANS that conserves energy and promotes house-keeping functions during rest.

Neurons

Excitable cells of the nervous tissue that transmit electrical signals.

Astrocytes

The most abundant CNS neuroglia that help determine capillary permeability, guide neuron migration, and control the chemical environment.

Microglia

CNS neuroglia that migrate toward injured neurons and phagocytize microorganisms and neuronal debris.

Ependymal cells

Cells that line the central cavities of the brain and spinal column, separating CNS interstitial fluid from cerebrospinal fluid.

Oligodendrocytes

CNS neuroglia with processes that wrap nerve fibers to form insulating myelin sheaths.

Satellite cells

PNS neuroglia that surround neuron cell bodies.

Schwann cells

Also called neurolemmocytes, these PNS cells surround peripheral nerve fibers, form myelin sheaths, and are vital to regeneration.

Amitotic

A characteristic of most neurons meaning they do not undergo division, with few exceptions.

Dendrites

The receptive regions of a neuron.

Axon hillock

The cone-shaped area of the cell body that leads into the axon.

Anterograde transport

Movement along the axon toward the axonal terminal, carrying mitochondria, membrane components, and enzymes.

Retrograde transport

Movement along the axon toward the cell body, carrying organelles to be degraded, signal molecules, viruses, and bacterial toxins.

Myelin sheath

A segmented protein-lipoid sheath that protects and electrically insulates axons, increasing the speed of impulse transmission.

Nodes of Ranvier

Gaps in the myelin sheath along an axon.

Multipolar neurons

Neurons with one axon and several dendrites; the most abundant type and major type in the CNS.

Bipolar neurons

Rare neurons with one axon and one dendrite, found in special sensory organs like the eye and olfactory mucosa.

Unipolar neurons

Neurons with a single short process that branches into peripheral and central processes; found mainly in the PNS.

Interneurons

Also called association neurons, these shuttle signals through CNS pathways and are mostly contained within the CNS.

Chemically gated channels

Also known as ligand-gated channels, these open when a specific neurotransmitter binds to the protein.

Voltage-gated channels

Ion channels that open and close in response to changes in membrane potential.

Resting membrane potential

The potential difference across a resting neuron membrane, approximately $-70\,mV$, maintained by differential permeability and the sodium-potassium pump.

Graded potentials

Incoming short-lived, localized changes in membrane potential that act as short-distance signals.

Action potential (AP)

A brief reversal of membrane potential with a total amplitude of $\sim 100\,mV$ that serves as the principal means of long-distance communication.

Threshold

The membrane potential level, typically $-55$ to $-50\,mV$, at which positive feedback leads to the opening of all $Na^+$ channels.

Absolute refractory period

The time from the opening of $Na^+$ channels until they reset, ensuring one-way transmission of nerve impulses.

Relative refractory period

The interval following the absolute refractory period when most $Na^+$ channels have reset but some $K^+$ channels remain open, elevating the threshold for AP generation.

Saltatory conduction

The rapid jumping of action potentials from node to node in myelinated axons, approximately 30 times faster than continuous conduction.

Group A fibers

Large diameter, myelinated somatic sensory and motor fibers with high conduction speeds.

Synapse

A junction that mediates information transfer from one neuron to another neuron or an effector cell.

EPSP

Excitatory postsynaptic potential; a local depolarization that brings the neuron closer to the AP threshold.

IPSP

Inhibitory postsynaptic potential; a local hyperpolarization that drives the neuron away from the AP threshold.

Temporal summation

Occurs when one or more presynaptic neurons transmit impulses in rapid-fire order.

Spatial summation

Occurs when a postsynaptic neuron is stimulated by a large number of terminals at the same time.

Acetylcholine (ACh)

A neurotransmitter released at neuromuscular junctions, synthesized by choline acetyltransferase and degraded by acetylcholinesterase.

Substance P

A neuropeptide that acts as a mediator of pain signals.

Cerebral cortex

The thin superficial layer of gray matter where the conscious mind is located, making up 40% of brain mass.

Lateralization

The division of labor between the two cerebral hemispheres.

Primary Motor Cortex

Located in the precentral gyri, it contains pyramidal cells allowing conscious control of precise voluntary movements.

Primary Somatosensory Cortex

Located in the postcentral gyri, it receives sensory information from skin, skeletal muscles, and joints.

Wernicke’s area

A region in the posterior association area involved in understanding written and spoken language.

Thalamus

The region comprising 80% of the diencephalon that sorts, edits, and relays afferent impulses to the cerebral cortex.

Hypothalamus

The main visceral control center that regulates body temperature, food intake, water balance, and the sleep cycle.

Pineal gland

A structure in the epithalamus that secretes melatonin to help regulate sleep-wake cycles.

Corpora quadrigemina

Dorsal midbrain protrusions including superior colliculi (visual reflex centers) and inferior colliculi (auditory relay centers).

Medulla Oblongata

Part of the brain stem containing the cardiovascular and respiratory centers, and regulating activities like vomiting and swallowing.

Cerebellum

Region dorsal to the pons and medulla that subconsciously provides precise timing for skeletal muscle contraction.

RAS (reticular activating system)

An axonal network that sends impulses to the cerebral cortex to keep it alert and filters out repetitive stimuli.

Blood-brain barrier

A selective barrier composed of continuous endothelium, basal lamina, and astrocyte feet that maintains a stable brain environment.

Conus medullaris

The terminal end of the spinal cord, typically at the $L1$ vertebra.

Dorsal Column-Medial Lemniscal Pathways

Ascending pathways that transmit input for discriminative touch and vibrations to the somatosensory cortex.

Pyramidal tracts

Direct descending pathways that regulate fast and fine (skilled) movements.

Paraplegia

Total motor and sensory loss caused by spinal cord transection between $T1$ and $L1$.

Quadriplegia

Total motor and sensory loss caused by spinal cord transection in the cervical region.

Poliomyelitis

A condition involving the destruction of ventral horn motor neurons by a virus, leading to muscle atrophy.

Amyotrophic Lateral Sclerosis (ALS)

Also known as Lou Gehrig’s disease, a progressive destruction of ventral horn motor neurons and pyramidal tract fibers.