CNS Neuroanatomy 3

Medulla oblongata

Lowest part of the brainstem continuous with the spinal cord; all sensory and motor communication between brain and spinal cord passes through it. Contains nuclei for cranial nerves VIII–XII and centers for vital autonomic control.

Medulla oblongata nuclei (3 main types)

1. Relay nuclei (sensory/motor information)

2. Cranial nerve nuclei (VIII–XII)

3. Autonomic control centers (cardiovascular, respiratory, digestive).

Gracile nucleus and cuneate nucleus

Relay somatic sensory information (touch, pressure, proprioception) from spinal cord to thalamus via medial lemniscus pathway.

Solitary nucleus

Receives visceral sensory input (taste, baroreception, chemoreception) from cranial and spinal nerves.

Olivary nuclei

Relay information from cerebrum, spinal cord, and diencephalon to cerebellum; form bulges (“olives”) on medulla surface and aid in motor learning.

Reticular formation

Diffuse network of gray matter extending through brainstem; regulates autonomic functions, arousal, and muscle tone.

Cardiovascular centers (medulla)

Control heart rate, force of contraction, and blood vessel diameter; essential for maintaining blood pressure.

Respiratory rhythmicity centers (medulla)

Regulate breathing rate and rhythm; interact with pons for fine-tuning respiration.

Cranial nerves associated with medulla

Vestibulocochlear (VIII), Glossopharyngeal (IX), Vagus (X), Accessory (XI), and Hypoglossal (XII) — involved in swallowing, vocalization, and visceral organ control.

Pons

Brainstem structure superior to medulla; acts as a bridge between cerebellum and higher brain regions; houses nuclei for cranial nerves V–VIII and centers for breathing regulation.

Pneumotaxic and apneustic centers (pons)

Paired respiratory centers that modify and smooth breathing rhythm generated by medulla (prevent over-inflation, fine-tune inhalation/exhalation).

Cerebellar peduncles

Three paired fiber tracts connecting cerebellum to brainstem:

Superior (to midbrain/diencephalon/cerebrum)

Middle (to pons)

Inferior (to medulla).

Transverse fibers (pons)

Fibers connecting cerebellar hemispheres via the pons; relay motor commands from cortex to cerebellum.

Mesencephalon (midbrain)

Upper brainstem region connecting pons to diencephalon; involved in visual/auditory reflexes, motor control, muscle tone, and alertness.

Corpora quadrigemina

Four rounded nuclei (“quadruplet bodies”) on dorsal midbrain forming the tectum; include superior and inferior colliculi.

Superior colliculi

Visual reflex centers — coordinate head and eye movements in response to visual stimuli (e.g., tracking moving objects).

Inferior colliculi

Auditory reflex centers — mediate head/neck orientation toward loud sounds.

Tectum

Dorsal portion of midbrain housing the corpora quadrigemina (superior/inferior colliculi).

Tegmentum (midbrain floor)

Contains red nucleus and substantia nigra; involved in muscle tone, posture, and voluntary movement coordination.

Red nucleus

Highly vascular midbrain structure controlling limb flexor muscle tone and motor coordination; integrates cerebellar and cortical inputs.

Substantia nigra

Darkly pigmented midbrain nucleus containing dopaminergic neurons; modulates basal nuclei activity; degeneration causes Parkinson’s disease.

Cerebral peduncles

Large bundles of descending motor tracts on anterior midbrain; connect cerebrum to lower brainstem/spinal cord.

Reticular activating system (RAS)

Part of reticular formation in midbrain; regulates consciousness, attention, and wakefulness. Damage leads to coma.

Diencephalon

Region between brainstem and cerebrum; includes thalamus, hypothalamus, and epithalamus. Surrounds the third ventricle.

Epithalamus

Roof of diencephalon; contains pineal gland which secretes melatonin, regulating circadian rhythms.

Thalamus

Paired egg-shaped nuclei forming lateral walls of the third ventricle; primary sensory relay center to the cerebral cortex (“gateway to the cortex”).

frontal, parietal, occipital, limbic + parietal

Divided into groups by function:

Anterior (limbic/emotions)

Medial (relay to ___ lobe)

Ventral (relay to ___ lobes)

Posterior (relay to ___ lobe)

Lateral (connects _____ systems).

Anterior thalamic nuclei

Part of limbic system; involved in emotion, learning, and memory.

Medial thalamic nuclei

Relay information to frontal lobe for executive and cognitive processing.

Ventral thalamic nuclei

Relay sensory input to parietal lobe (touch, pressure, pain, proprioception).

Posterior thalamic nuclei

Include pulvinar, lateral geniculate (visual), and medial geniculate (auditory) nuclei; relay sensory data to appropriate cortical regions.

Lateral thalamic nuclei

Integrate and adjust activity between parietal cortex and cingulate gyrus (emotion + attention).

Hypothalamus

Inferior diencephalic region controlling autonomic and endocrine functions; integrates neural and hormonal regulation for homeostasis.

Infundibulum

Stalk connecting hypothalamus to pituitary gland, enabling hypothalamic control of endocrine secretion.

Mammillary bodies

Pair of rounded structures involved in reflex movements (suckling, chewing) and memory formation.

Hypothalamic nuclei and functions
ADH, Oxytocin, Body temperature, circadian, Hormonal

• Supraoptic nucleus → ___ secretion

Paraventricular nucleus → ___ secretion

Preoptic area → ______ control

Suprachiasmatic nucleus → _____ rhythm

Tuberal nuclei →____ regulation via pituitary.

Autonomic regulation (hypothalamus)

Controls heart rate, blood pressure, digestion, and respiratory rate through autonomic centers in brainstem.

Behavioral/emotional drives (hypothalamus)

Regulates hunger, thirst, sexual behavior, and emotional responses.

Coordination between voluntary and autonomic systems (hypothalamus)

Integrates somatic and visceral responses (e.g., stress-induced changes in heart rate).

Cerebellum Flashcards

Cerebellum

Posterior brain region for coordination of movement, posture, and balance; ensures smooth, precise muscle activity.

Cerebellar hemispheres

Left and right lobes connected by vermis; each hemisphere controls coordination of ipsilateral body movements.

Vermis

Narrow midline band separating cerebellar hemispheres; maintains body posture and equilibrium.

Folia cerebelli

Folded gray matter ridges on cerebellar surface increasing cortical area, analogous to gyri in cerebrum.

Primary fissure

Separates anterior and posterior lobes of cerebellum.

Flocculonodular lobe

Small lobe important for balance and eye movement coordination.

Purkinje cells

Large inhibitory neurons in cerebellar cortex that integrate sensory and motor inputs and regulate deep cerebellar nuclei output.

Arbor vitae

White matter “tree of life” pattern connecting cerebellar cortex to deep nuclei and peduncles.

Cerebellar cortex vs nuclei

gray matter controlling subconscious motor coordination; vs relay output to other brain regions via peduncles.

Cerebellar function summary

Coordinates voluntary movement, adjusts motor commands, maintains posture and balance, and fine-tunes learned motor skills.

Medulla vs Pons vs Midbrain

Medulla: autonomic reflexes & life-sustaining functions.
Pons: communication bridge & breathing control.
Midbrain: sensory reflexes & motor control.

Thalamus vs Hypothalamus

sensory relay to cortex. vs
autonomic & endocrine control, emotional regulation.

Cerebrum vs Cerebellum

conscious thought & voluntary control. vs
subconscious coordination & precision of motor output.

Superior vs Inferior colliculi

visual reflexes (track moving object). vs
auditory reflexes (turn toward sound).

Red nucleus vs Substantia nigra

motor coordination and tone.vs
dopamine control of basal nuclei (movement initiation).

Pons vs Medulla respiratory control

adjusts rhythm (pneumotaxic/apneustic). vs
generates basic rhythm (respiratory rhythmicity centers).

Cerebellar peduncles connection summary

Superior: cerebellum ↔ midbrain/cortex.
Middle: cerebellum ↔ pons.
Inferior: cerebellum ↔ medulla.

Hypothalamic nuclei & hormone control

ADH (supraoptic) controls water balance; Oxytocin (paraventricular) controls uterine contractions/milk ejection; both hormones secreted via posterior pituitary.

Cerebellar damage vs Cerebral damage

___damage → ataxia, poor balance, dysmetria.
____ damage → paralysis, aphasia, sensory loss.

Thalamic nuclei mapping

Anterior → emotion; Medial → cognition; Ventral → sensory relay; Posterior → vision/audition; Lateral → emotion integration.