Anatomy & Physiology: Brain and Cranial Nerves Vocabulary

Vocabulary flashcards covering embryonic development, brainstem regions, cerebellum, diencephalon, cerebral structures, meninges, ventricles, blood supply, and the twelve cranial nerves based on Chapter 13.

Brain Neuron Count and Connections

The human brain contains around 100 billion neurons, each averaging 10,000 connections with other neurons, along with approximately 1 trillion glial cells.

Neural Tube

A tube formed by the fusion of neural folds during embryonic development that gives rise to the central nervous system, with its cephalic portion becoming the brain and caudal portion becoming the spinal cord.

Neural Crest Cells

Cells that migrate away from the crest of neural folds to give rise to PNS sensory, autonomic, and enteric neurons, pigmented cells, adrenal medulla, facial bones, and tooth dentin.

Development of Brain Segments

The early embryonic brain develops from three primary pouches (forebrain/prosencephalon, midbrain/mesencephalon, and hindbrain/rhombencephalon), which later subdivide into five secondary vesicles.

Prosencephalon

The embryonic forebrain pouch that divides into the telencephalon (which becomes the cerebrum) and the diencephalon.

Mesencephalon

The embryonic midbrain structure that remains a single structure in both embryo and adult, serving as a visual reflex center and part of the auditory pathway.

Rhombencephalon

The embryonic hindbrain pouch that divides into the metencephalon (pons and cerebellum) and myelencephalon (medulla oblongata).

Regions of the Brain

The four main divisions of the adult brain: the brainstem, cerebellum, diencephalon, and cerebrum.

Brainstem

The region connecting the spinal cord to the cerebrum, consisting of the medulla oblongata, pons, and midbrain, with the reticular formation scattered throughout.

Medulla Oblongata

The most inferior part of the brainstem, measuring about 3 cm long, that functions as a center for vital reflexes such as heart rate, blood vessel diameter, breathing, swallowing, and vomiting.

Pyramids (Medulla)

Two prominent anterior enlargements on the medulla oblongata formed by large descending motor tracts involved in conscious control of skeletal muscles.

Decussation of Pyramids

The crossing of motor fibers near the inferior end of the medullary pyramids, accounting for each half of the brain controlling the opposite side of the body.

Olives

Rounded oval structures protruding from the anterior surface of the medulla oblongata lateral to the pyramids, containing nuclei involved in balance, coordination, and sound modulation.

Pons

The part of the brainstem superior to the medulla oblongata that contains ascending and descending tracts, pontine nuclei relaying information between cerebrum and cerebellum, and sleep and respiratory centers.

Corpora Quadrigemina

Four nuclei forming mounds on the dorsal surface of the midbrain tectum, consisting of two superior colliculi and two inferior colliculi.

Superior Colliculi

The two upper mounds of the corpora quadrigemina that receive visual, auditory, and tactile sensory input and initiate visual/head reflexes toward stimuli.

Inferior Colliculi

The two lower mounds of the corpora quadrigemina involved in hearing, serving as an integral part of CNS auditory pathways.

Tegmentum

The region of the midbrain largely consisting of ascending sensory tracts (such as the spinothalamic tract and medial lemniscus) and containing the red nuclei, cerebral peduncles, and substantia nigra.

Red Nuclei

Paired pinkish nuclei within the midbrain tegmentum that aid in unconscious regulation and coordination of motor activities.

Cerebral Peduncles

Portions of the midbrain ventral to the tegmentum consisting primarily of descending motor tracts carrying information from the cerebrum to the brainstem and spinal cord.

Substantia Nigra

A dark gray or black nuclear mass in the midbrain containing melanin granules, interconnected with basal nuclei to maintain muscle tone and coordinate movements.

Reticular Formation

A diffuse system of interconnected nuclei scattered throughout the brainstem that regulates alertness, consciousness, sleep-wake cycles, posture, pain perception, and rhythmic contractions.

Arbor Vitae

The branching, tree-like white matter structure located within the center (medulla) of the cerebellum.

Purkinje Cells

The largest inhibitory neurons in the CNS, located in the cerebellar cortex, each receiving about 200,000 synapses and sending the sole output from the cerebellar cortex to deep nuclei.

Thalamus

The largest component of the diencephalon, serving as the major sensory relay center of the brain for all sensory input except smell before projecting to the cerebral cortex.

Habenula

An epithalamic structure involved in motivational control of behavior, playing an integrative role in reward mechanisms and behaviors associated with addictions.

Pineal Gland

An endocrine structure in the epithalamus shaped like a pinecone that modulates the sleep-wake cycle and other biorhythms.

Hypothalamus

The most inferior part of the diencephalon that acts as the primary control center for homeostasis, autonomic nervous system regulation, body temperature, food/water intake, and endocrine function.

Mammillary Bodies

Bulges on the ventral surface of the hypothalamus involved in olfactory reflexes, emotional responses to odors, and memory.

Infundibulum

A funnel-shaped stalk extending from the floor of the hypothalamus that connects it to the pituitary gland.

Gyri

Folds or ridges on the surface of the cerebral hemispheres that increase the total surface area of the cerebral cortex.

Sulci

Grooves separating the gyri on the surface of the cerebrum that divide each hemisphere into lobes.

Precentral Gyrus

The gyrus located anterior to the central sulcus that serves as the primary motor cortex.

Postcentral Gyrus

The gyrus located posterior to the central sulcus that serves as the primary somatic sensory cortex.

Cerebral Lobes

Anatomical divisions of each cerebral hemisphere comprising the frontal, parietal, occipital, temporal lobes, and the deep insula.

Frontal Lobe

Cerebral lobe involved in voluntary motor function, motivation, aggression, sense of smell, mood, personality, and decision making.

Parietal Lobe

Cerebral lobe serving as the primary center for receiving and evaluating most sensory information, except smell, hearing, taste, and vision.

Occipital Lobe

Cerebral lobe responsible for receiving and integrating visual sensory input.

Temporal Lobe

Cerebral lobe that receives and evaluates smell and hearing inputs, playing vital roles in memory, abstract thought, and judgment.

Insula

The deep fifth cerebral lobe located within the lateral fissure that receives and evaluates taste information.

Association Fibers

Nerve fibers in the cerebral medulla that connect different areas of the cerebral cortex within the same hemisphere.

Commissural Fibers

Nerve fibers in the cerebral medulla that connect one cerebral hemisphere to the opposing hemisphere, with the corpus callosum being the largest bundle.

Projection Fibers

Nerve fibers that connect the cerebrum to lower brain regions and the spinal cord, forming the internal capsule.

Corpus Striatum

The subcortical group of basal nuclei within the cerebrum, consisting of the caudate nucleus and lentiform nucleus (putamen and globus pallidus).

Limbic System

A ring of deep cerebral and diencephalic structures involved in motivation, emotion, learning, memory, and autonomic/endocrine modulation.

Meninges Structure

Protective connective tissue membranes surrounding the brain and spinal cord, consisting of the superficial dura mater, middle arachnoid mater, and deep pia mater.

Falx Cerebri

The largest dural fold, sickle-shaped, lying in the longitudinal fissure anchoring anteriorly to the ethmoid bone and separating the left and right cerebral hemispheres.

Tentorium Cerebelli

A dural fold oriented horizontally in the cranial cavity between the cerebrum and the cerebellum.

Subarachnoid Space

The space situated between the arachnoid mater and pia mater filled with cerebrospinal fluid and containing major blood vessels.

Choroid Plexus

A vascular secretory structure composed of specialized ependymal cells and pia mater capillaries within the ventricles that produces cerebrospinal fluid.

Cerebrospinal Fluid Flow Rate

CSF flows at a rate of approximately $0.4\,mL/min$, replenishing the total volume ($117\,mL$ in subarachnoid space and $23\,mL$ in ventricles) about 4 to 5 times daily.

Blood-Brain Barrier

A selective permeability barrier formed by tight junctions between capillary endothelial cells and surrounding astrocyte foot processes that regulates substance movement into brain tissue.

Cranial Nerves Overview

Twelve pairs of nerves (designated I through XII) connecting directly to the brain or brainstem (except XI) to convey sensory, somatic motor, and parasympathetic signals.

Olfactory Nerve (CN I)

Exclusively sensory cranial nerve originating from olfactory receptors that passes through the cribriform plate to convey the sense of smell.

Optic Nerve (CN II)

Exclusively sensory cranial nerve passing through the optic foramen that transmits visual information from the retina to the brain.

Oculomotor Nerve (CN III)

Cranial nerve providing somatic motor input to four extrinsic eye muscles and levator palpebrae, plus parasympathetic control for pupil constriction and lens accommodation.

Trochlear Nerve (CN IV)

Somatic motor cranial nerve that innervates the superior oblique muscle of the eye.

Trigeminal Nerve (CN V)

The largest sensory cranial nerve supplying general sensation to the face, teeth, and meninges, and somatic motor fibers to the muscles of mastication via ophthalmic (V1), maxillary (V2), and mandibular (V3) branches.

Abducens Nerve (CN VI)

Somatic motor cranial nerve that innervates the lateral rectus muscle responsible for abducting the eye.

Facial Nerve (CN VII)

Cranial nerve controlling facial expression muscles, taste on the anterior two-thirds of the tongue, and parasympathetic innervation to submandibular, sublingual, and lacrimal glands.

Vestibulocochlear Nerve (CN VIII)

Exclusively sensory cranial nerve transmitting impulses from the inner ear for hearing (cochlear nerve) and balance (vestibular nerve).

Glossopharyngeal Nerve (CN IX)

Cranial nerve controlling stylopharyngeus motor action, taste/sensation on the posterior third of the tongue, parotid gland secretion, and monitoring carotid sinus/body receptors.

Vagus Nerve (CN X)

Cranial nerve providing motor control to larynx/pharynx muscles, taste from posterior tongue, and widespread parasympathetic innervation to thoracic and abdominal viscera.

Accessory Nerve (CN XI)

Motor cranial nerve with spinal roots that pass through the foramen magnum and jugular foramen to innervate the sternocleidomastoid and trapezius muscles.

Hypoglossal Nerve (CN XII)

Somatic motor cranial nerve arising from the medulla oblongata that innervates intrinsic and extrinsic tongue muscles, as well as thyrohyoid and geniohyoid muscles.