CNS Neuroanatomy 1

Medulla oblongata

Brainstem nucleus connecting brain to spinal cord;
relays sensory information to thalamus and other brainstem centers;
contains autonomic centers that regulate heart rate, blood pressure, respiration, and digestion.

Pons

Brainstem region anterior to cerebellum that relays information between cerebrum and cerebellum and to the thalamus;

contains centers for subconscious somatic and visceral motor control and serves as the cerebellar “bridge.”

Mesencephalon (Midbrain)

Upper brainstem structure involved in processing visual and auditory data, generating reflexive somatic motor responses to stimuli, and maintaining consciousness/alertness (e.g., reticular activating influence).

Thalamus

Paired diencephalic nuclei that act as the major relay and processing center for nearly all sensory information going to the cerebrum (filters and routes sensory signals to appropriate cortical areas).

Hypothalamus

Diencephalic region involved in homeostasis and behavior: controls autonomic functions, emotions, thirst, hunger, circadian rhythms, and links to the pituitary via the infundibulum to regulate endocrine function.

Epithalamus/Pineal gland

Part of the diencephalon; contains the pineal gland which secretes melatonin and helps regulate circadian rhythms and some neuroendocrine functions.

Cerebellum

Second-largest brain structure located posterior to pons and inferior to cerebrum; coordinates somatic motor function by adjusting output of motor centers to produce smooth, precise, and coordinated movements and balance.

Cerebrum (Telencephalon)

Largest brain region composed of paired hemispheres; site of conscious thought, intellectual functions, memory storage, and conscious/subconscious regulation of skeletal muscle via cortical motor areas.

Gyri

Raised ridges on the cerebral cortex that increase cortical surface area and are landmarks for cortical regions.

Sulci

Grooves between gyri on the cerebral cortex; deeper sulci (fissures) separate large brain regions.

Fissure

Long, deep groove in the cerebral cortex (e.g., longitudinal fissure separates the two cerebral hemispheres).

Gray matter

Regions composed primarily of neuronal cell bodies, dendrites, and synapses — forms the cerebral and cerebellar cortex (outer layer) in the brain.

White matter

Myelinated axon tracts that connect different brain regions; lies deep to cortical gray matter in the cerebrum and cerebellum.

Contrast: brain vs spinal cord gray/white organization

In brain: gray matter is peripheral (cortex) and white matter internal. In spinal cord: white matter is peripheral and gray matter is central (butterfly-shaped).

Ventricular system

Four interconnected CSF-filled cavities (lateral ventricles ×2, third ventricle, fourth ventricle) that produce, circulate, and drain cerebrospinal fluid (CSF) to cushion the CNS and transport nutrients/waste.

Lateral ventricles (1 & 2)

Large paired ventricles within each cerebral hemisphere; main body in parietal lobe with anterior horn extending into frontal lobe, posterior horn into occipital lobe, and inferior horn into temporal lobe; separated by septum pellucidum.

Interventricular foramen (foramen of Monro)

Small channel that connects each lateral ventricle to the third ventricle, allowing CSF passage.

Third ventricle

Median ventricle located in the diencephalon; communicates with the fourth ventricle via the cerebral aqueduct.

Cerebral aqueduct (aqueduct of Sylvius)

Narrow canal through the midbrain that connects the third and fourth ventricles; a common site of obstruction causing hydrocephalus.

Fourth ventricle

Location between the pons and cerebellum; communicates with the central canal of the spinal cord and has foramina in its roof allowing CSF to enter the subarachnoid space.

Central canal

Continuation of the ventricular system running down the spinal cord; contains CSF and connects with the fourth ventricle.

CSF (cerebrospinal fluid) functions

Provides mechanical cushion for the brain/spinal cord, transports nutrients to CNS cells and removes metabolic waste, and helps maintain stable extracellular environment.

Ependymal cells

Glial cells that line the ventricles and central canal; they contribute to CSF production and form a barrier between ventricular CSF and neural tissue.

Foramina of the fourth ventricle

Openings in the roof of the fourth ventricle (e.g., foramina of Luschka and Magendie) that allow CSF to flow into the subarachnoid space.

Septum pellucidum

Thin membrane separating the anterior horns of the left and right lateral ventricles.

cranial bones: frontal, parietal, temporal, and occipital

Skull bones protecting the brain — form the rigid protective case around the brain.

Cranial meninges

Three protective connective tissue layers around brain and spinal cord: dura mater (outermost), arachnoid mater (middle), and pia mater (innermost adherent to cortex).

Dura mater

Thick, tough outer meningeal layer; in the skull it forms dural folds and venous sinuses and provides robust mechanical protection.

Arachnoid mater

Intermediate meningeal layer; bridges over sulci, creating the subarachnoid space beneath it where CSF circulates and major blood vessels run.

Pia mater

Thin innermost meningeal layer tightly adherent to the surface of the brain and spinal cord, following gyri and sulci.

Subarachnoid space

Space between arachnoid and pia containing CSF and major cerebral blood vessels; site for lumbar puncture CSF access (lower spinal region).

Blood–brain barrier (BBB)

Selective barrier formed by tight junctions between cerebral endothelial cells (supported by astrocytes) that restricts passage of many compounds from blood into brain interstitial fluid, maintaining CNS homeostasis.

Rich blood supply importance

Brain has high metabolic demand; dense cerebral circulation supplies oxygen and glucose — disruption (ischemia) quickly impairs function.

Brainstem vs cerebellum vs cerebrum

_______ (medulla, pons, midbrain) mediates vital autonomic functions and reflexes and relays information; _______ coordinates and fine-tunes motor output; ______ carries higher cognitive functions, voluntary movement planning, and sensory perception.

Hydrocephalus (basic mechanism)

Condition from impaired CSF flow or absorption (e.g., aqueductal blockage) that leads to ventricular enlargement and increased intracranial pressure.

Clinical landmark: lateral ventricle horns and lobes

Anterior horn projects into frontal lobe (useful in imaging landmarks), posterior horn extends into occipital lobe, inferior horn extends into temporal lobe — helps localize pathology on scans.

lateral,interventricular foramen,third,cerebral aqeduct,fouth,formamine,subarachnoid space,venous sinuses

CSF: (1) ventricles → (2) → (3) ventricle → (4) → (5) ventricle → (6) to (7) → absorbed into (8).

Typical exam-style relationship question prep (concept pairing)

Pair structure → function (e.g., thalamus → sensory relay; cerebellum → motor coordination; medulla → autonomic control). Practice mapping clinical deficits to damaged structure.