Brain Anatomy and Function

Frontal Lobe

• Location: Separated from the temporal lobe by the lateral sulcus and from the parietal lobe by the central sulcus.
• Function: Personality, emotion, motivation, voluntary movement, and executive functions.

Precentral Gyrus

• Location: Rostral to the central sulcus
• Function: Initiates voluntary movements via the primary motor cortex neurons.

Precentral Sulcus

• Location: Rostral to the precentral gyrus
• Function: Plays a role in motor control including primary motor cortex neurons.

Parietal Lobe

• Location: Caudal to the frontal lobe, separated by the central sulcus.
• Function: Sensory integration, spatial awareness, motor action coordination, and cognitive support for memory, attention, and language.

Postcentral Gyrus

• Location: Caudal to the central sulcus
• Function: Contains the primary somatosensory cortex for proprioception, touch, pressure, temperature, and pain perception.

Temporal Lobe

• Location: Inferior to the lateral sulcus.
• Function: Hearing, language, memory, and emotion, includes Wernicke’s area for language comprehension.

Occipital Lobe

• Location: Superior to the cerebellum and caudal to the parieto-occipital sulcus.
• Function: Processes visual information.

Cerebellum

• Location: Inferior to the occipital and temporal lobes, superior to the brainstem.
• Function: Balance, postural maintenance, coordination, and movement.

Cerebellar Hemispheres

• Divided by the vermis.
• Lateral hemispheres: involved in motor planning.
• Intermediate zones: Contribute to movement coordination.

Diencephalon

• Location: Deep in the brain, surrounding the third ventricle, between the two hemispheres of the cerebrum, superior to the brainstem.
• Contains: The hypothalamus, thalamus, epithalamus, and subthalamus.
• Function: Coordinates with the endocrine system for hormone release, relays sensory and motor signals to the cerebral cortex, and regulates circadian rhythms.

Thalamus

• Location: Near the brain's center, superior to the midbrain.
• Function: Regulates sleep, alertness, and wakefulness. Relays information between subcortical areas and the cerebral cortex and processes sensory information.

Hypothalamus

• Location: Deep in the brain, between the cerebral hemispheres, inferior to the thalamus, and creates the floor and inferolateral walls of the third ventricle.
• Function: Regulates thirst, water and food intake, the autonomic nervous system, circadian rhythms, body temperature, blood pressure, breastfeeding, learning, memory, sexual drive, and emotional expression, and sends hormones to the pituitary.

Epithalamus

• Location: The most dorsal portion of the diencephalon, forming the roof of the third ventricle.
• Function: Melatonin secretion from the pineal gland, regulates motor pathways and emotions, maintains circadian rhythms, and conserves energy.

Midbrain

• Location: Most rostral/top part of the brainstem connecting the pons and cerebellum with the forebrain.
• Function: Motor control, especially eye movements, and processing of vision and hearing.

Pons

• Location: Middle portion of the brainstem.
• Function: Coordinates face and eye movements, facial sensations, hearing, and balance.

Medulla

• Location: Inferior part of the brain connecting to the spinal cord through the foramen magnum.
• Function: Controls vital processes like heartbeat, breathing, and blood pressure.

Spinal Cord

• Location: Begins at the bottom of the brainstem (connecting to the medulla) and runs the length of the spine
• Function: Sends motor commands from the brain to the body, sends sensory info from the body to the brain, and coordinate reflexes

Longitudinal Fissure

• The deep groove that separates the two cerebral hemispheres.

Central Sulcus

• A groove between the frontal and parietal lobes running from the longitudinal fissure to the lateral fissure
• Defines the primary motor cortex anteriorly and the primary sensorimotor cortex posteriorly

Lateral Sulcus

• A deep groove on the lateral surface of the brain separating the frontal and parietal lobes superiorly from the temporal lobe

Corpus Callosum

• Located in between the left and right cerebral hemispheres
• Integrates and transfers information from cerebral hemispheres to process sensory, motor, and high-level cognitive signals

Parieto-Occipital Sulcus

• A deep groove that separates the parietal and occipital lobes.
• Structural marker to differentiate the parietal and occipital lobes

Cingulate Gyrus

• In the medial aspect of the cerebral hemisphere just superior to the corpus callosum.
• Part of the limbic system involved in emotion processing, learning, and memory. Also contributes to motivation, decision making, and pain modulation.

Calcarine Sulcus

• In the medial surface of the occipital lobe, running horizontally from the parieto-occipital sulcus.
• Contains the primary visual cortex and processes visual information, specifically the contralateral visual field.

Fornix

• Bundle of white matter fibers that arches around the thalamus, originating in the hippocampus.
• The primary outgoing pathway from the hippocampus, important for its involvement in episodic (personal experiences and events) memory. Key part of the limbic system, important for memory and cognition.

Septum Pellucidum

• Thin triangular membrane found in the midline septal area of the brain positioned between the two cerebral hemispheres and separates the anterior horns of the lateral ventricles.
• Acts as a relay station between the hippocampus and hypothalamus, helps regulate emotional behaviors, social behaviors, and integrate emotional and memory-related information.

Lateral Ventricles

• A c-shaped cavity situated within each cerebral hemisphere, filled with cerebrospinal fluid to cushion the brain.
• Includes anterior horns, body, inferior horns, and posterior horns.

Third Ventricle

• A narrow vertical cavity of the diencephalon situated between the right and left thalamus.
• Produces, secrete, and covey cerebrospinal fluid.

Fourth Ventricle

• Diamond-shaped ventricle that is caudal to the pons and upper medulla, and rostral to the cerebellum
• Drains CSF from ventricular system to the subarachnoid space, allowing it to circulate and absorb around the CNS.

Interventricular Foramen

• Space that connects the lateral ventricles to the third ventricle found near the midline of the brain between the thalamus and fornix.
• Allows cerebrospinal fluid to flow from the lateral ventricle to the third ventricle to ensure proper drainage into the ventricular system to the subarachnoid space.

Parahippocampal Gyrus

• Located in the Medial temporal lobe and runs parallel to the long axis of the hippocampus
• Forms part of the limbic system and plays a crucial role in spatial navigation, memory consolidation, emotional processing, and visuospatial processing.

Optic Nerves and Chiasm

• At the base of the brain inferior to the hypothalamus and superior to the pituitary gland within the suprasellar cistern
• The optic chiasm is formed when the optic nerves come together in order to allow for the crossing of the fibers from the nasal retina to the optic tract, enabling the brain to process visual information from both eyes to create a single image.

Spinal Dura Mater

• Outermost meningeal layer of the spinal cord
• Contains rural venous sinuses that allows blood to leave brain and CSF to re-enter circulation.

Spinal Arachnoid Mater

• Located between dura and pita mater.
• Protect spinal cord and CSF

Spinal Pia Mater

• Deepest meningeal layer, clings to the spinal cord.
• Protects the spinal cord and enclose venous sinuses

Denticulate Ligaments

• Thin, triangular-shaped structures made of pia mater that extend from spinal cord to dura mater.
• Stabilize spinal cord within the vertebral canal.

Cervical Cord

• From the base of your skull through the cervical vertebrae
• Protects the spinal cord, supports the head, and allows for head and neck movement

Thoracic Cord

• Housed within the thoracic vertebral canal
• Controls lumbosacral function and is involved in visceral and autonomic regulation

Lumbosacral Cord

• Where the lumbar spine transitions into the sacrum
• Contains the necessary circuitry to independently drive locomotor behaviors

Ventral Rootlets

• Emerge from the ventrolateral sulcus of the spinal cord in the anterior root exit zone
• Transmitting somatic motor output from the brain and spinal cord to the body's skeletal muscles.

Dorsal Rootlets

• Within the dorsal spinal cord lateral to the midline.
• They are part of the dorsal root which carries sensory information from the body to the CNS.

Ventral Nerve Root

• Anterior root of the two roots that emerge from the spinal cord via the ventrolateral sulcus.
• Transmits motor output from the CNS to the body via motor neurons.

Dorsal Nerve Root

• Posterior root of the two roots that emerge from the spinal cord via the posterolateral sulcus.
• Transmits sensory input from the body to the CNS via sensory neurons.

Dorsal Root Ganglion

• At the base of each spinal nerve near the spinal cord on the posterior side.
• Collection of sensory neuron cell bodies that transmit sensory information like pain, temperature, and touch from the PNS to the CNS.

Ventral Rami

• Anterior branches of spinal nerves and formed when a spinal nerve splits into a ventral and dorsal ramus.
• Carry sensory and motor fibers for the innervation of muscles, joints, and skin of the lateral and ventral body walls and the extremities.

Dorsal Rami

• A Branch of a spinal nerve that runs along the back of the body (posterior) and backward from the intervertebral foramen.
• Provides motor innervation to muscles of the back. Provides sensory innervation to the skin of the back, neck, and posterior head. Carries visceral motor, somatic motor, and somatic sensory information to and from the back.

Conus Medullaris

• Located at the very bottom of the spinal cord, typically around the L1-L2, before the cauda equina.
• Provides a point of attachment for the filum terminale which helps stabilize the spinal cord within the spinal canal. Gives rise to the lumbar sympathetic, sacral somatic and sacral parasympathetic nerves which continue downward within the cauda equina.

Cauda Equina

• A bundle of nerve roots that resemble a horse’s tail, before the filum terminale.
• The primary function is to send and receive messages between the lower limbs and the pelvic organs; enables movement and sensation in the legs and bladder.

Filum Terminale

• At the very end of the spinal cord, extending from the tip of the conus medullaris and attaching to the posterior surface of the coccyx.
• Anchors the spinal cord to the coccyx, which provides stability and prevents excessive movement.

Mammillary Bodies

• Two small structures are located in the posterior portion of the hypothalamus
• Function in recollective memory

CN II- Optic Nerve

• Extends from the posterior part of the eyeball (roughly 2 mm medial to the posterior pole) to the suprasellar space in the middle cranial fossa
• Transmits visual information

Optic Tract

• Lies along the upper anterior and then the lateral surface of the cerebral peduncle and is parallel to the posterior cerebral artery
• Carries visual information from the optic chiasm to the left and right lateral geniculate bodies as a part of the visual pathway

Midbrain

• Location: Inferior to the cerebral cortex but the most superior portion of the brainstem.
• Function: Connects the brain to the spinal cord; plays a crucial role in processing visual and auditory signals.

Tectum

• Rear part of the midbrain between the forebrain and hindbrain.
• Controls eye movements, approach, and avoidance movements and is involved in processing auditory information to help the body respond to environmental cues.

Superior Colliculus

• Located in the dorsal midbrain on the posterior side of the brainstem; wedged between the cerebellum and thalamus.
• Integrates sensory information, particularly visual to direct eye and head movements towards a stimulus of interest, allows body to orient itself towards a target based on visual input.

Inferior Colliculus

• Located in the midbrain, on the dorsal surface and part of the tectum; situated caudal to the superior colliculus and rostral to the trochlear nerve.
• Relays auditory information from the inner ear to the auditory cortex, input from both ears converge providing information about horizontal and vertical sounds location.

CN III- Oculomotor Nerve

• Midbrain at the base of the brain stem, caudal to the mammillary bodies.
• Motor innervation to extra ocular muscles, which includes the inferior oblique, medial rectus, inferior rectus, and superior rectus.

CN IV- Trochlear Nerve

• Located just inferior to the inferior colliculus
• Motor innervation to superior oblique muscle

Pons

• Base of the brain, between the midbrain and the medulla oblongata near the base of the skull
• Transmit signals between the forebrain and cerebellum, sends information to your body, giving you sensory cues and motor information

CN V- Trigeminal Nerve

• Middle of the cranial fossa, near the temple, and in front of the ear.
• Includes the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves.
• Provides sensation to the face, including touch, pain, and temperature, as well as controlling the muscles used for mastication

Medulla

• Most inferior part of the brain that connects the brain to the spinal cord.
• Regulates vital processes within the cardiovascular, respiratory, digestive, motor, sensory, and autonomic nervous systems.

Medullary Pyramids

• Triangular structures in the ventral portion of the medulla.
• Carry corticospinal tracts to their decussation at the medullary spinal junction, provides a pathway for motor signals from the brain to the spinal cord.

Ventral Median Sulcus

• On the front surface of spinal cord, separates the left and right halves of the spinal cord, a deep groove found directly in the center of spinal cords anterior surface.
• Primarily to divide the spinal cord into two distinct halves, organization of neural pathways within the cord.

Posterior Median Sulcus

• Shallow groove in the spinal cord that separates the left and right halves of the posterior side.
• Primarily to divide the spinal cord into two distinct halves, organization of neural pathways within the cord.

Posterior Intermediate Sulcus

• Lateral to the gracile fasciculus.
• Divides the dorsal sensory ascending column into two halves, allowing the gracile fasciculus and cuneate fasciculus.

Olives

• Lateral to medullary pyramids
• Relays sensory information to the cerebellum and is important for movement and balance.

Cuneatus Fasciculus

• Lateral to the gracile fasciculus
• Transmits fine touch, proprioception, vibration

Cuneate Tubercle

• Laterally to the gracile fasciculus in the upper thoracic and cervical (C1 to T6) spinal cord segments
• transmitting sensory information—including vibration, conscious proprioception, and two-point discrimination—from the upper extremities

Gracile Fasciculus

• Present throughout the length of the spinal cord and contains afferents from the lower trunk and extremities, below the T6 spinal cord segment
• Carries sensory input from vertebral level T6 and below and ascends into the gracile nucleus to form the gracile tubercle

Gracile Tubercle

• Found on the dorsal surface of the medulla at the junction of the brainstem and spinal cord, visible bump that corresponds to the location of the gracile nucleus.
• Responsible for processing sensory information from the lower body, such as touch, vibration, and proprioception.

CN VI- Abducens

• Originates from the superior orbital fissure and can be found at the junction between the pons and medulla oblongata.
• Responsible for abduction of the eye, which controls the lateral rectus muscle.

CN VII- Facial Nerve

• Originates in the pons, travels through a bony canal in the temporal bone.
• Controls muscles of facial expression, carries taste sensation from anterior two/thirds of the tongue and provides parasympathetic innervation to the salivary and la crimal glands, regulating tear production and saliva secretion.

CN VIII- Vestibulocochlear Nerve

• Located in the midbrain and exits at the level of the superior colliculus.
• Governs hearing and balance.

CN IX- Glossopharyngeal Nerve

• Lateral to the vestibulocochlear Nerve.
• Provides sensation from the pharynx, tonsils, middle ear, carotid sinus, taste to posterior third of the tongue and motor innervation to stylopharyngeus.

CN X- Vagus Nerve

• Exits the skull through the jugular foramen, travels down the neck within the carotid sheath, over the pericardium and into the abdomen, giving off numerous branches
• Main nerve of the parasympathetic nervous system, controlling involuntary bodily processes like digestion, heart rate, breathing, saliva production, and mood

CN XI- Spinal Accessory Nerve

• Originates from the jugular foramen at the base of the skull and runs to the trapezius muscle.
• Innervates the sternocleidomastoid and trapezius muscles to control head rotation, neck flexion, and shoulder elevation.

CN XII- Hypoglossal Nerve

• In brainstem from the medulla oblongata, exits the skull through the hypoglossal canal and travels down the neck to the floor of the mouth.
• Controls the tongues muscles, which are used for speaking, swallowing, and chewing

Test your knowledge of brain anatomy, including lobes, gyri, and structures like the cerebellum and hypothalamus. Match brain structures to functions and identify cranial nerve roles.