06 diencephalon, brainstem, cranial nerves & skull

Three parts of the diencephalon

Thalamus, hypothalamus, epithalamus

Main function of the thalamus

Sensory gatekeeper/relay; filters excess input (selective attention)

Thalamus lies lateral to the

Third ventricle

Which sense does NOT relay through the thalamus?

Smell (olfaction)

Anterior thalamic nuclei relay to

Limbic system

Lateral thalamic nuclei relay

Motor info (from basal ganglia and cerebellum) and body sensation

Posterior thalamic nuclei relay

Vision and hearing

Does motor relay occur in the posterior thalamus?

No - lateral thalamus

Structure relaying basal ganglia motor info to the primary motor cortex

Thalamus

Hypothalamus function

Maintains homeostasis via ANS (HR, BP, digestion, temperature); controls pituitary

Posterior pituitary secretes

Oxytocin and vasopressin (ADH), made by the hypothalamus

Epithalamus (pineal gland) secretes

Melatonin (sleep-wake cycle)

Cerebellum: volume vs neurons

~10% of brain volume, ~50% of all neurons

Cerebellum function

Motor coordination and balance; integrates visual, proprioceptive, vestibular input

Cerebellum is at the level of the

Pons

Cerebellum attaches to the brainstem via

Cerebellar peduncles

Vermis controls

Axial skeleton (trunk)

Lateral cerebellar hemispheres control

Appendicular skeleton (limbs)

Flocculonodular lobe controls

Eye movements (and balance)

Right lateral cerebellum coordinates

Right limbs (same side / ipsilateral)

Difference between cerebellum and basal ganglia motor roles

Cerebellum integrates vision and vestibular info; basal ganglia do not

Striatum

Caudate + putamen

Tadpole-shaped nucleus following the lateral ventricle

Caudate nucleus

Parkinson's disease

Death of substantia nigra neurons → less dopamine to basal nuclei; trouble starting/stopping movement

Huntington's disease

Degeneration of striatum → excess, jerky movements

3 parts of the brainstem

Midbrain, pons, medulla

Is the diencephalon part of the brainstem?

No

Most cranial nerves arise from

The brainstem

Midbrain key structures

Superior colliculi, inferior colliculi, substantia nigra, cerebral peduncles

Superior colliculus

Visual reflexes (tracking); midbrain

Inferior colliculus

Auditory integration; midbrain

Damage to the superior colliculi causes

Visual reflex deficits

Position of visual vs auditory colliculi

Visual (superior) colliculi are superior to auditory (inferior) colliculi

Substantia nigra

Midbrain; produces dopamine for the basal nuclei

Cerebral peduncles carry

Corticospinal (motor) tracts

Cranial nerves from the midbrain

III, IV

Pons functions

Relays info from cerebrum to cerebellum; carries sensory info up; anterior to 4th ventricle

Cranial nerves from the pons

V, VI, VII, VIII

Medulla key structures

Pyramids (motor), olives, dorsal column nuclei (sensory), autonomic centres

Pyramidal decussation occurs in the

Medulla

Medulla autonomic centres control

Breathing and heart rate

Cranial nerves from the medulla

IX, X, XI, XII

CN I and CN II originate from

Cerebrum

General CNS rule: motor vs sensory location

Motor = anterior; sensory = posterior

Cranial nerve name mnemonic

Oh Oh Oh To Touch And Feel Very Green Velvet, AH

Cranial nerve type mnemonic

Some Say Marry Money, But My Brother Says Big Brains Matter More

Are cranial nerves CNS or PNS?

PNS

CN I

Olfactory; sensory; smell

CN II

Optic; sensory; vision

CN III

Oculomotor; motor; most eye muscles + levator palpebrae superioris; pupil constriction

CN IV

Trochlear; motor; superior oblique

CN V

Trigeminal; both; face sensation + muscles of mastication

CN VI

Abducens; motor; lateral rectus

CN VII

Facial; both; facial expression + taste anterior 2/3 tongue

CN VIII

Vestibulocochlear; sensory; hearing + balance

CN IX

Glossopharyngeal; both; taste posterior 1/3 tongue, pharynx sensation, swallowing, parotid secretion

CN X

Vagus; both; main parasympathetic nerve to thoracic/abdominal organs; swallowing, vocalization

CN XI

Accessory; motor; sternocleidomastoid + trapezius

CN XII

Hypoglossal; motor; tongue movement

CN I passes through

Cribriform plate of the ethmoid bone

Why is smell strongly linked to memory?

CN I connects directly to the limbic system

Cranial nerve carrying both motor and sensory (trigeminal vs oculomotor vs abducens vs vestibulocochlear)

Trigeminal (V)

Trigeminal branches

V1 ophthalmic, V2 maxillary, V3 mandibular

Which trigeminal branch is motor?

V3 (mandibular) - muscles of mastication

Taste nerves for the tongue

CN VII (anterior 2/3) and CN IX (posterior 1/3)

Basilar artery stroke likely causes

Loss of sensation on the cheek (pons, CN V)

Decreased vagus output effect on heart rate

Heart rate increases

CN III lesion

Ptosis, eye down and out, dilated pupil

CN VI lesion

Can't abduct; eye drifts medially

Facial nerve LMN lesion (e.g. Bell's palsy)

Whole same-side face paralyzed, including forehead

Facial nerve UMN lesion (e.g. stroke)

Lower face on opposite side weak; forehead spared

Spinal cord ends around vertebral level

L1-L2

Spinal cord white vs grey matter arrangement

White matter outside (tracts); grey matter inside ("H")

Dorsal horn

Sensory

Ventral horn

Motor

Neurocranium bones

Frontal, parietal, temporal, occipital, sphenoid

Viscerocranium bones

Zygomatic, maxilla, mandible (and nasal)

Sutures

Fibrous joints between neurocranium bones (tight, for protection)

Coronal suture joins

Frontal and parietal bones

Sagittal suture joins

Left and right parietal bones

Pterion bones

Frontal, parietal, temporal, sphenoid

Fontanelles

Membranous spots in an infant skull; close by age 2

Anterolateral fontanelle becomes the

Pterion

Number of vertebrae by region

7 cervical, 12 thoracic, 5 lumbar (24) + sacrum (5 fused) + coccyx

Parts of a vertebra

Body, pedicle, lamina, transverse process, spinous process

Cervical vertebrae have ___ for vertebral arteries

Transverse foramina

Lambdoid suture joins

Parietal and occipital bones

Anterior fontanelle becomes

The junction of the coronal and sagittal sutures

Cerebellum gross anatomy

Cortex with fissures and folia, deep nuclei, 2 hemispheres with lobes, central vermis

Three cerebellar lobes

Anterior, posterior, flocculonodular

Olive location

Lateral medulla

Dorsal column nuclei location

Posterior medulla (sensory)

Taste and swallowing nerves from the medulla

CN IX and CN X

Vestibulocochlear (balance) info goes from its pons nucleus to

Thalamus, cerebellum, CN XI, eye muscle nuclei