Chapter 12—The Central Nervous System

Cephalization

Evolutionary and developmental concentration of nervous tissue and sensory organs at the anterior end of the body, forming a head region.

Brain

Main control center of the CNS; receives sensory information, integrates it, and coordinates motor, cognitive, emotional, and autonomic functions.

Proprioception

Sense of body position and movement, provided by receptors in muscles, tendons, and joints.

Neural tube

Embryonic structure formed from the neural plate; develops into the brain and spinal cord.

Primary brain vesicles

Three early embryonic brain regions: prosencephalon, mesencephalon, and rhombencephalon.

Prosencephalon

Forebrain; develops into the telencephalon and diencephalon.

Mesencephalon

Midbrain; remains the midbrain in the adult brain.

Rhombencephalon

Hindbrain; develops into the metencephalon and myelencephalon.

Secondary brain vesicles

Five embryonic brain regions; telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.

Telencephalon

Develops into the cerebral hemispheres, including the cerebral cortex, basal nuclei, and related structures.

Diencephalon

Develops into the thalamus, hypothalamus, and epithalamus.

Metencephalon

Develops into the pons and cerebellum.

Myelencephalon

Develops into the medulla oblongata.

Brainstem

Consists of the midbrain, pons, and medulla oblongata. Connects the brain with the spinal cord and regulates essential functions.

Cervical flexures

Embryonic bends in the developing neural tube near the junction of the brain and spinal cord.

Convolutions

Folds of the cerebral cortex, including raised gyri and grooves called sulci. Increase cortical surface area.

Gray matter

Nervous tissue containing neuron cell bodies, dendrites, synpases, and unmyelinated axons.

White matter

Nervous tissue composed mainly of myelinated axons; carries signals between different CNS regions.

Ventricles

Connected cavities within the brain filled with CSF.

Lateral ventricles

Two large ventricles, one in each cerebral hemisphere. They produce CSF through their choroid plexuses.

Septum pellucidum

Thin membrane separating the right and left lateral ventricles.

Interventricular foramen

Opening connecting each lateral ventricle to the third ventricle.

Third ventricle

Narrow CSF-filled cavity in the diencephalon, between the two thalami.

Cerebral aqueduct

Narrow passage through the midbrain connecting the third and fourth ventricles.

Fourth ventricle

CSF-filled cavity between the brainstem and cerebellum; connects with the central canal and subarachnoid space.

Lateral apertures

Two openings in the fourth ventricle that allow CSF to enter the subarachnoid space.

Median aperture

Midline opening in the fourth ventricle that allows CSF to enter the subarachnoid space.

Cerebral hemispheres

Right and left halves of the cerebrum, responsible for higher functions such as sensation, voluntary movement, language, and reasoning.

Longitudinal fissure

Deep groove separating the cerebrum form the cerebellum.

Transverse cerebral fissure

Deep groove separating the cerebrum from the cerebellum.

Central sulcus

Groove separating the frontal lobe from the parietal lobe; lies between the precentral and postcentral gyri.

Frontal lobe

Responsible for voluntary motor control, planning, decision-making, personality, and aspects of speech production.

Parietal lobe

Processes somatic sensory information, including touch, pressure, temperature, pain, and body position.

Precentral gyrus

Ridge immediately anterior to the central sulcus; contains the primary motor cortex.

Parieto-occipital sulcus

Groove separating the parietal and occipital lobes, especially visible on the medial brain surface.

Occipital lobe

Posterior cerebral lobe primarily responsibel for visual processing.

Lateral sulcus

Deep groove separating the temporal lobe from the frontal and parietal lobes.

Temporal lobe

Involved in hearing, language comprehension, memory, and aspects of emotion.

Insula

Deep cerebral lobe hidden beneath portinos of the frontal, parietal, and temporal lobes; invovled in taste, visceral sensation, and emotional awareness.

Cerebral cortex

Outer layer of gray matter covering the cerebral hemispheres; responsible for conscious perception, voluntary movement, and higher cognitive functions.

Motor areas

Cerebral regions involved in planning, initiating, and controlling voluntary movement.

Primary motor cortex

Located in the precentral gyrus of the frontal lobe; directly controls voluntary skeletal muscle movements.

Pyramidal cells

Large, triangular-shaped neurons found in the cerebral cortex. Many participate in pathways controlling voluntary movement.

Somatotopy

Organization of the body in an orderly spatial arrangement within a brain region.

Motor homunculus

Map of body regions represented in the primary motor cortex. Body parts requiring precise control occupy larger cortical areas.

Premotor cortex

Frontal lobe region anterior to the primary motor cortex; helps plan and coordinate learned movements.

Broca’s area

Usually in the left frontal lobe; involved in producing and organizing spoken language.

Frontal eye field

Frontal lobe region that controls voluntary eye movements, especially directing the eyes toward a target.

Primary somatosensory cortex

Located in the postcentral gyrus of the parietal lobe; receives and processes touch, pressure, pain, temperature, and proprioceptive information.

Spatial discrimination

Ability to identify the precise locatino of a stimulus and distinguish between nearby points of contact.

Somatosensory homunculus

Map of the body’s sensory representation in the primary somatosensory cortex; regions with greater sensory sensitivity occupy more cortical space.

Somatosensory association cortex

Parietal lobe region that interprets somatic sensory information and helps identify objects through touch.

Primary visual cortex

Located in the occipital lobe; receives and initially processes visual information.

Visual association area

Occipital region that interprets visual information, allowing recognition of objects, shapes, and patterns.

Primary auditory cortex

Located in the temporal lobe; receives and processes sound information.

Auditory association area

Interprets sounds, allowing recognition of speech, music, and familiar noises.

Primary olfactory cortex

Cortical region that initially process information related to smell.

Rhinecephalon

Collectively refers to oflcatory-related brain structures involved in processing smell.

Gustatory cortex

Located primarily in the insula and frontal operculum; processes taste information.

Multimodal association areas

Brain regions that integrate information from multiple sensory systems and connect it with memory, emotions, and reasoning.

Anterior association area

Prefrontal cortex region involved in judgment, planning, decision-making, working memory, and personality.

Posterior association area

Region involving portions of the parietal, temporal, and occipital lobes; integrates sensory information for recognition and spatial awareness.

Limbic association area

Association region involved in emotion, motivation, memory, and linking experiences with emotional meaning.

Lateralization

Specialization of certain functions in one cerebral hemisphere more than the other.

Cerebral dominance

Hemisphere that is more specialized for certain functions, especially language. Usually the left hemisphere for language.

Cerebral white matter

Myelinated axons beneath the cerebral cortex that connect different brain regions.

Association fibers

White matter fibers connecting cortical areas within the same cerebral hemisphere.

Commissural fibers

White matter fibrs connecting corresponding or related regions of the right and left cerebral hemispheres.

Commissures

Bundles of commissural fibers that cross the midline and connect the two cerebral hemispheres.

Corpus callosum

Largest cerebral commissure; connects the right and left cerebral hemispheres and allows communication between them.

Projection fibers

White matter fibers connecting the cerebral cortex with lower brain regions, the brainstem, and spinal cord.

Internal capsule

Dense bundle of projection fibers carrying sensory and motor information between the cerebral cortex and lower CNS structures.

Basal nuclei

Groups of deep cerebral gray matter involved in regulating movement, posture, and muscle tone.

Caudate nucleus

C-shaped basal nucleus involved in movement regulation, learning, and goal-directed behavior.

Putamen

Basal nucleus involved in regulating voluntary movement.

Globus pallidus

Basal nucleus that helps regulate movement by influencing motor pathways through the thalamus.

Thalamus

Major sensory relay station that processes and directs most sensory information to the cerebral cortex; also participates in motor and consciousness pathways.

Interthalamic adhesion

Small connection between the right and left thalami in some individuals.

Hypothalamus

Regulates homeostasis, temperature, hunger, thirst, automatic activity, and endocrine function through its control of the pituitary gland.

Mammillary bodies

Small hypothalamic structures involved in memory processing and part of the limbic system.

Infundibulum

Stalk connecting the hypothalamus to the pituitary gland.

Epithalamus

Diencephalon region containing the pineal gland; involved in regulating circadian rhythms through melatonin secretion.

Cerebral peduncles

Large fiber bundles in the midbrain carrying motor information from the cerebrum toward the brainstem and spinal cord.

Corpora quadrigemina

Four rounded elevations on the dorsal midbrain consistinng of the superior and inferior colliculi.

Superior colliculi

Midbrain structures involved in visual reflexes and orienting the eyes and head toward visual stimuli.

Inferior colliculi

Midbrain structures involved in auditory processing and sound-related reflexes.

Substantia nigra

Midbrain region containing dopamine-produces neurons imortant for movement control; degeneration is associated with Parkinson’s disease.

Red nucleus

Midbrain structure involved in motor coordination and movement pathways.

Pons

Brainstem region connecting the medulla and midbrain; relays information to the cerebellum and helps regulate breathing.

Medulla oblongata

Lowest portion of the brainstem, continuous with the spinal cord; contains centers regulating heart rate, blood pressure, and breathing.

Pyramids

Paired ridges on the anterior medulla containing descending corticospinal motor fibers.

Decussation of the pyramids

Crossing of most corticospinal fibers in the lower medulla, causing each cerebral hemisphere to control the opposite side of the body.

Olives

Rounded elevations on the lateral medulla that overlie the inferior olivary nuclei.

Inferior olivary nuclei

Medullary nuclei that relay information to the cerebellum and help coordinate motor learning and movement.

Cochlear nuclei

Brainstem nuclei that receive auditory information from the cochlear portion of cranial nerve VIII

Vestibular nuclei

Brainstem nuclei that process balance and head-position informatino from the vestibular system.

Nucleus gracilis

Medullary nucleus receiving fine touch, vibration, and conscious proprioception from the lower body.

Medulla funcitons

Regulates vital autonomic functions, including breathing, heart rate, and blood pressure; also coordinates reflexes such as swallowing, coughing, and vomiting.

Cerebellum

Brain region responsible for coordinating movement, balance, posture, and motor learning. It helps make movements smooth and precise.

Vermis

Narrow midline region connecting the two cerebellar hemispheres; important for posture and trunk coordination.