Ch 14: The Brain and Cranial Nerves

Vocabulary practice flashcards generated from lecture material on Chapter 14: The Brain and Cranial Nerves.

Primary Brain Vesicles

The three initial embryonic brain swellings formed during the first 3 weeks of gestation: the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon).

Secondary Brain Vesicles

The five subdivisions of the embryonic brain formed through encephalization: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.

Encephalization

The developmental process in which the 1st and 3rd primary brain vesicles further divide to form five secondary brain vesicles.

Falx Cerebri

A strong, sickle-shaped fold of dura mater descending vertically in the longitudinal fissure to separate the two cerebral hemispheres.

Falx Cerebelli

A small triangular process of dura mater that separates the two cerebellar hemispheres.

Tentorium Cerebelli

A rigid dural extension that separates the cerebrum from the cerebellum.

Blood-Brain Barrier (BBB)

A protective mechanism formed by tight junctions between endothelial cells of brain capillaries, a thick basement membrane, and astrocyte processes that regulates entry of bloodborne substances into brain tissue.

Cerebrospinal Fluid (CSF)

A clear fluid circulating through brain ventricles, central canal, and subarachnoid space that provides mechanical protection, homeostatic function, and transport of nutrients and wastes.

Septum Pellucidum

A thin membrane separating the lateral ventricles anteriorly.

Choroid Plexuses

Networks of capillary blood vessels lined by ependymal cells located within each ventricle that produce cerebrospinal fluid.

Arachnoid Villi

Finger-like projections of the arachnoid mater extending into dural venous sinuses (such as the superior sagittal sinus) to reabsorb CSF into venous blood.

Hydrocephalus

A condition caused by the failure of CSF to form and drain normally, resulting in an abnormal buildup of pressure in the skull.

Decussation of Pyramids

The crossover point in the medulla oblongata where $90\text{\%}$ of corticospinal tract axons cross over, allowing each side of the brain to control muscles on the opposite side of the body.

Substantia Nigra

A darkly pigmented midbrain nucleus containing dopamine-releasing neurons that assist in controlling subconscious muscle activities.

Red Nucleus

A nucleus in the midbrain that contributes to the control of voluntary limb movements.

Reticular Activating System (RAS)

The ascending network of sensory axons in the reticular formation that projects to the cerebral cortex to maintain consciousness, wakefulness, attention, and filter out irrelevant sensory input.

Vermis

The central constricted region connecting the two lateral cerebellar hemispheres.

Thalamus

A diencephalic region functioning as the major relay station for sensory impulses traveling to the cerebral cortex, excluding olfaction.

Hypothalamus

A diencephalic structure that integrates autonomic activities, regulates body temperature, hunger, thirst, circadian rhythms, and controls pituitary hormone secretion.

Epithalamus

A diencephalic region superior and posterior to the thalamus consisting of the pineal gland (melatonin secretion) and habenular nuclei (olfactory emotional responses).

Gyri

The elevated folds or convolutions on the surface of the cerebral cortex formed during embryonic growth.

Sulci

The shallow grooves located between the folds on the surface of the cerebral cortex.

Fissures

The deepest grooves separating major divisions or hemispheres of the cerebrum.

Precentral Gyrus

The gyrus located immediately anterior to the central sulcus in the frontal lobe containing the primary motor area.

Postcentral Gyrus

The gyrus located immediately posterior to the central sulcus in the parietal lobe containing the primary somatosensory area.

Insula

A fifth region of the cerebrum situated deep within the lateral cerebral sulcus beneath the frontal, parietal, and temporal lobes.

Association Tracts

Bundles of myelinated axons in cerebral white matter conducting nerve impulses between gyri in the same hemisphere.

Commissural Tracts

Bundles of myelinated axons, such as the corpus callosum, conducting nerve impulses between corresponding gyri of opposite hemispheres.

Projection Tracts

Bundles of myelinated axons conveying nerve impulses between the cerebrum and lower parts of the CNS (thalamus, brain stem, or spinal cord).

Basal Nuclei

Paired centers of gray matter deep within cerebral white matter that initiate and terminate movements, suppress unwanted movements, and regulate muscle tone.

Limbic System

A functional ring of structures encircling the upper brain stem and corpus callosum ('emotional brain') governing emotions, memory, and olfaction.

Sensory Homunculus

A distorted somatic sensory map of body regions mapped onto the postcentral gyrus, where regional size corresponds to sensory receptor density.

Motor Homunculus

A somatic motor map mapped onto the precentral gyrus, where larger cortical areas are devoted to body parts requiring complex or fine motor control.

Broca's Speech Area

Cortical region in the frontal lobe (Brodmann's areas 44 and 45) responsible for motor planning and production of speech.

Wernicke's Area

Association region (Brodmann's areas 22, 39, and 40) in the left temporal and parietal lobes that interprets spoken words and translates thoughts into speech.

Nonfluent Aphasia

An inability to form words resulting from stroke or damage to Broca's speech area, despite clear thoughts.

Fluent Aphasia

A condition caused by damage to Wernicke's area in which speech production remains fluent but lacks meaningful content ('word salad').

Alpha Waves

Rhythmic EEG brain waves ($8\text{--}13\text{ Hz}$) present in an awake, relaxed state that disappear during sleep.

Beta Waves

High-frequency EEG brain waves ($14\text{--}30\text{ Hz}$) present during sensory input and mental activity.

Theta Waves

EEG brain waves ($4\text{--}7\text{ Hz}$) indicating emotional stress or brain disorders in adults.

Delta Waves

High-amplitude EEG brain waves ($1\text{--}5\text{ Hz}$) occurring during deep sleep in adults, indicating brain damage if present in an awake adult.

Electroencephalogram (EEG)

A diagnostic recording of brain waves created by communicating superficial cerebral cortical neurons using scalp electrodes.

Olfactory (I) Nerve

A special sensory cranial nerve mediating the sense of smell.

Optic (II) Nerve

A special sensory cranial nerve transmitting visual sensory signals from the retina.

Trigeminal (V) Nerve

The largest cranial nerve; a mixed nerve with ophthalmic, maxillary, and mandibular branches providing facial sensation and motor control for chewing.

Facial (VII) Nerve

A mixed cranial nerve controlling facial expression, taste on the anterior two-thirds of the tongue, and tear and saliva secretion.

Vestibulocochlear (VIII) Nerve

A special sensory cranial nerve responsible for equilibrium and hearing.

Glossopharyngeal (IX) Nerve

A mixed cranial nerve carrying taste from the posterior third of the tongue, monitoring blood pressure/gases, and assisting in swallowing and salivation.

Vagus (X) Nerve

A mixed cranial nerve ('the wanderer') providing parasympathetic motor control to thoracic and abdominal viscera and slowing heart rate.

Accessory (XI) Nerve

A motor cranial nerve supplying the trapezius and sternocleidomastoid muscles to control head and shoulder movements.

Hypoglossal (XII) Nerve

A motor cranial nerve controlling tongue movements for speech, food manipulation, and swallowing.

Bell's Palsy

Paralysis of the facial (VII) nerve causing loss of facial expression, inability to close the eye, and loss of taste and salivation.