Brain Structure Notes

Myelencephalon (medulla)

Main role: Vital autonomic functions (cardio-respiration) & reticular formation (arousal/attention). Analogy: life-support control room.

Reticular formation

Network running through brainstem; keeps you awake/alert. Analogy: brain’s on/off switch + dimmer for alertness.

Metencephalon

Parts: Pons (bridge of white-matter tracts + cranial nerve nuclei) & Cerebellum (fine-tuning, timing, motor learning). Analogy: pons = highway hub; cerebellum = orchestra conductor.

Cerebellum function

Adjusts movement using sensory & vestibular feedback; also helps with motor learning & timing. Analogy: live sound engineer fine-tuning the band.

Mesencephalon

Main roof & floor structures include Tectum (visual reflexes, auditory reflexes) and Tegmentum (pain & freeze, motor feedback, dopamine).

PAG role

Pain suppression (opioids/endorphins) + defensive freezing. Analogy: panic-room control hub around the brain’s plumbing.

Substantia nigra function

Sends dopamine to striatum for smooth voluntary movement; loss → Parkinson’s. Analogy: dopamine fuel station — runs dry → tremor & stiffness.

Red nucleus role

Motor feedback loop to cerebellum. Analogy: relay office sending reports back to conductor.

Diencephalon major parts

Thalamus (relay hub to cortex) and Hypothalamus (drives feeding, sex, temp, stress; controls pituitary hormones).

Thalamus — sensory nuclei map

LGN → vision; MGN → audition; VPL/VPM → somatosensation; MD → cognition/PFC. Analogy: airport hub with terminals for each sense.

Hypothalamus → pituitary → adrenal (HPA) axis

CRF → ACTH → cortisol/epinephrine (stress response). Analogy: CEO sends email → manager → factory pumps stress hormones.

Telencephalon

Includes: Cerebral cortex (neocortex: lobes, gyri) + Subcortical systems (limbic system & basal ganglia).

Key cortical landmarks

Longitudinal fissure = hemispheres; Central fissure = motor vs sensory; Lateral fissure = temporal vs frontal/parietal.

Neocortex layers

6 layers; sensory cortex → thick input; motor → thick output. Analogy: sensory = giant inbox; motor = giant outbox.

Limbic system main pieces

Hippocampus = explicit/spatial memory; Amygdala = fear/emotion; Cingulate = attention/emotion link.

Basal ganglia key structures

Striatum (movement selection/initiation), Globus pallidus (output), Nucleus accumbens (reward); SN provides dopamine.

Corpus callosum role

Main commissure connecting hemispheres; damage → split-brain effects.

Cerebellum

Fine-tunes movement with sensory/vestibular feedback.

Periaqueductal Gray (PAG)

Midbrain structure where opioids act for pain relief.

Lateral Geniculate Nucleus (LGN)

Thalamic nucleus that handles visual information.