Neuroanatomy and Brain Structures: Cortex, Lobes, CSF Pathway, and Cranial Nerves

Cortex

Outer layer of the brain (gray matter) responsible for higher functions

Gyrus

Raised ridge of brain tissue

Sulcus

Shallow groove between gyri

Fissure

Deep groove separating brain regions

Lobe

Major division of the brain (frontal, parietal, etc.)

White matter

Myelinated axons (signal transmission)

Gray matter

Neuron cell bodies (processing)

Fiber tract

Bundle of axons in CNS

Nerve

Bundle of axons in PNS

Plexus

Network of intersecting nerves

Nucleus

Cluster of neuron cell bodies in CNS

Ganglion

Cluster of neuron cell bodies in PNS

What is the location and function of the primary motor cortex?

Frontal lobe; controls voluntary movement

What is the location and function of the primary somatosensory cortex?

Parietal lobe; processes touch, pain, temperature

Frontal lobe

Movement, decision-making, personality

Parietal lobe

Sensory processing, spatial awareness

Temporal lobe

Hearing, memory, language

Occipital lobe

Vision

Insular cortex

Taste, visceral sensation, emotion

Optic nerve/chiasm/tract

Vision pathway

Pituitary gland

Hormone control (master gland)

Pineal gland

Melatonin, circadian rhythm

Superior colliculi

Visual reflexes

Inferior colliculi

Auditory reflexes

Pons

Relay center; breathing regulation

Medulla oblongata

Vital functions (heart rate, breathing)

Basal ganglia

Movement regulation

Posterior commissure

Connects brain hemispheres (visual reflexes)

What is the pathway of cerebrospinal fluid (CSF) flow?

Lateral ventricles → 3rd ventricle → cerebral aqueduct → 4th ventricle → subarachnoid space → arachnoid granulations → venous blood

Why are there cervical and lumbar enlargements in the spinal cord?

To provide more neurons for limb control of the arms and legs.

At what vertebral level does the spinal cord end?

Around the L1-L2 vertebrae.

What structure does the spinal cord become at its termination?

The conus medullaris, which transitions into the cauda equina.

Into which vessel do the dural sinuses drain?

The internal jugular vein.

What is the function of the Circle of Willis?

It is a circulatory anastomosis that supplies blood to the brain and surrounding structures, providing collateral circulation to ensure blood flow even if one of the supply arteries is blocked.

what is apart of the circle of willis?

Anterior cerebral artery

Anterior communicating artery

Internal carotid artery

Posterior cerebral artery

Posterior communicating artery

Basilar artery

Anterior cerebral artery supplies

Medial frontal/parietal lobes

Middle cerebral artery supplies

Lateral brain (motor/sensory, speech)

Posterior cerebral artery supplies

Occipital lobe (vision)

olfactory nerve

cribriform plate

optic nerve

optic canal

oculomotor nerve

superior orbital fissure

trochlear nerve

superior orbital fissure

trigeminal

V1: ophthalmic

V2: maxillary

V3: mandibular

V1: ophthalmic = superior OF

V2: maxillary = foramen rotundum

V3: mandibular = foramen ovale

abducens nerve

superior OF

facial nerve

internal acoustic meatus -> stylomastoid

glossopharyngeal nerve

internal acoustic meatus

vagus nerve

jugular foramen

spinal accessory nerve

jugular foramen

hypoglossal nerve

hypoglossal canal

What is the function of the dartos muscle?

Wrinkles skin for temperature regulation

What is the function of the cremaster muscle?

Raises and lowers the testes

What does the seminal vesicle secrete?

Fructose-rich fluid for energy

What does the prostate secrete?

Alkaline fluid

What is the function of the bulbourethral gland?

Lubrication

Which sphincter is responsible for voluntary urine control?

External urethral sphincter

Which structure maintains urethral patency during an erection?

Corpus spongiosum

Which hormone is responsible for fat distribution on the mons pubis at puberty?

Estrogen

What is the function of the bulb of the vestibule?

Erectile tissue that engorges during arousal

What is the female analogue to the scrotum?

The labia majora.

What is the female analogue to the skin of the penis?

The labia majora, or more broadly, the external genital skin.

What is the female analogue to the corpus cavernosum?

The crura of the clitoris.

What is the female analogue to the corpus spongiosum?

The vestibular bulbs.

What is the female analogue to the glans penis?

The glans clitoris.

What is the female analogue to the foreskin (prepuce)?

The clitoral hood (prepuce of the clitoris).

What is the female analogue to the crus of the penis?

The crus of the clitoris.

Function of Bulb of Vestibule

Erectile tissue; engorges during arousal

Psoas major origin

Lumbar vertebrae

Psoas major insertion

Lesser trochanter

Iliacus origin

Iliac fossa

Iliacus insertion

Lesser trochanter

Quadratus lumborum origin

Iliac crest

Quadratus lumborum insertion

12th rib

Phrenic nerve

Diaphragm

Axillary nerve

Deltoid

Radial nerve

Posterior arm (extension)

Musculocutaneous

Anterior arm (flexion)

Ulnar nerve

Hand muscles

Median nerve

Forearm flexors, thumb

Femoral nerve

Quadriceps

Obturator nerve

Adductors

Sciatic nerve

Posterior thigh

Tibial nerve

Posterior leg

Common fibular

Anterior/lateral leg

Superior rectus

Elevates eye (Oculomotor nerve)

Inferior rectus

Depresses eye (Oculomotor nerve)

Medial rectus

Moves eye medially (Oculomotor nerve)

Lateral rectus

Moves eye laterally (Abducens nerve)

Superior oblique

Down & lateral (Trochlear nerve)

Inferior oblique

Up & lateral (Oculomotor nerve)