Cerebrum Lobes and Functions

The Cerebrum and Its Lobes

• The cerebrum is divided into lobes, with specific structures indicating their boundaries.
• Each lobe has distinct functions.

Gyri, Sulci, and Fissures

• Gyri are ridges on the brain's surface.
• Sulci are grooves separating gyri.
• Fissures are deep splits, such as the longitudinal cerebral fissure dividing the cerebral hemispheres.

Frontal Lobe

• Location: Front of the brain
• Posterior border: Central sulcus
• Includes precentral gyrus (before central sulcus) and superior, middle, and inferior frontal gyri (perpendicular to the precentral gyrus).
• Primary motor cortex in precentral gyrus initiates voluntary movements.
• Broca's area in inferior frontal gyrus produces written and spoken language.

Parietal Lobe

• Just posterior to central sulcus
• Contains postcentral gyrus with the primary somatosensory cortex for tactile and proprioceptive information.
• Responsible for spatial orientation and attention.
• Receives sensory information in the postcentral gyrus and the precentral gyrus is involved in motor control.

Occipital Lobe

• Most posterior lobe
• Separated from parietal lobe by parieto-occipital sulcus.
• Houses primary visual cortex and visual association cortex, essential for vision.

Temporal Lobe

• Below the lateral sulcus
• Includes superior, middle, and inferior temporal gyri.
• Superior temporal gyrus contains primary auditory cortex.
• Contains Wernicke's area in the posterior superior temporal gyrus, which is responsible for language comprehension.
• Additional functions include learning, memory, and visual processing assistance.

Limbic Lobe

• Seen best in a mid-sagittal view
• Includes the cingulate gyrus, the most prominent structure
• Functions: emotional responses, drive-related behavior, and memory processing

Recap of Cerebral Lobes and Functions

• Frontal Lobe: Initiates voluntary movement and produces written and spoken language.
• Parietal Lobe: Processes sensory information and is responsible for spatial orientation.
• Occipital Lobe: Houses the primary visual cortex, essential for vision.
• Temporal Lobe: Contains the primary auditory cortex, responsible for language comprehension, learning, and memory.
• Limbic Lobe: Regulates emotions, drive-related behavior, and memory processing.

Mid-Sagittal Structures of the Brain

• Structures visible in the mid-sagittal plane can be identified.

Major Structures Visible in the Mid-Sagittal View

• Cerebral Lobes: Frontal, limbic, parietal, occipital, and temporal lobes
• Cerebellum and Arbor Vitae:
  • The cerebellum is visible, showing white matter tracts.
  • Arbor Vitae: The branching pattern of white matter tracts means "tree of life," unique to each individual.
• Brainstem Structures: Midbrain, pons, and medulla oblongata
• Limbic Lobe Structures:
  • Cingulate gyrus: A belt-like structure
  • Cingulate sulcus: Surrounds the cingulate gyrus
• Corpus Callosum and Associated Structures:
  • Rostrum: The most anterior portion
  • Genu: The curved portion (Latin for "knee")
  • Body: The central section
  • Splenium: Most posterior, shaped like a bandage
• Below the Corpus Callosum:
  • Fornix: An arch-shaped structure
  • Septum Pellucidum: A membrane separating two spaces

C-Shaped Brain Structures

• Fornix
• Corpus Callosum
• Cingulate gyrus
• These C-shapes are due to embryonic development

Diencephalon Structures

• Thalamus: Meaning "inner chamber"
  • Interthalamic adhesion: Connects the left and right sides of the thalamus
• Hypothalamus: Located under the thalamus
• Infundibulum: A stalk leading to the pituitary gland
• Epithalamus: Located above the thalamus
  • Pineal gland: Shaped like a pine cone
• Subthalamus: Not especially visible in this view

Quadtrigeminal Plate and Colliculi

• Two superior colliculi
• Two inferior colliculi
• Quadtrigeminal means 'four twins,' referring to the paired colliculi.

Diencephalon

• The diencephalon is located between the cerebral hemispheres

Breakdown of the Word “Diencephalon”

• "Di" means through or between.
• Encephalon refers to the brain.
• Diencephalon means through or between the brain.

Components of the Diencephalon

• Thalamus: Inner chamber
• Epithalamus: Upon the thalamus
• Hypothalamus: Under the thalamus
• Subthalamus: Not pictured initially

Sensory Pathways Relayed by the Thalamus

• Conscious proprioception
• Vibration
• Fine touch
• Pain
• Temperature
• Taste
• Vision
• Hearing
• Smell bypasses this pathway.

Summary of the Hypothalamus Mnemonic P-TAN HATS

• P-TAN HATS aids recall of the hypothalamus' functions.
• T - Thirst and water balance
• A - Autonomic nervous system regulation
• N - Neurohypophysis (posterior pituitary gland)
• H - Hunger and satiety
• A - Adenohypophysis (anterior pituitary gland)
• T - Temperature regulation
• S - Sexual urges and emotions

Function of the Epithalamus

• Consists mainly of the pineal gland.
• Some animals have a parietal eye, linked to the pineal gland, for light detection and thermoregulation.
• In humans, the pineal gland modulates the circadian rhythm by producing melatonin in low light or at nighttime.

Function of the Subthalamus.

• Lesions may lead to tremors.
• It tends to modulate movement, inhibiting jerky movements or tremors.

Cranial Nerves

• Two main questions to keep in mind:
  • What are the basic functions of each cranial nerve?
  • Where is each cranial nerve located?

Spinal Cord Anatomy and Cranial Nerve Function

• Understanding spinal cord anatomy helps in grasping cranial nerve functions
• The ventral horn gray matter houses somatic motor cell bodies for skeletal muscle innervation.
• The anterior lateral horn gray matter houses visceral motor cell bodies for smooth muscle innervation.
• The posterior lateral horn gray matter handles visceral sensory information.
• The dorsal horn gray matter processes somatic sensory data like pain, temperature, touch, and proprioception.

Spinal Cord and Brainstem

• The anterior spinal cord handles motor functions
• Sensory innervation occurs in the spinal cord's posterior portion
• The spinal cord evolves into the brainstem and flattens from a circular tube to an oval shape
  • Somatic/visceral motor sections change from anterior to medial
  • Somatic/visceral sensory fibers switch from posterior to lateral
• New types of innervation evolve: -Pharyngeal Motor: Head and neck -Special Sense Sensory

Medial Cranial Nerves

• Solely provide somatic motor innervation to skeletal muscles
• Nerves are 3, 4, 6, and 12

Lateral Cranial Nerves

• Innervate skeletal muscles from the pharyngeal arches and smooth muscles via autonomic functions.
• Transmit both somatic and visceral sensations
• Nerves are 5, 7, 9, and 10

Other Cranial Nerves

• This group includes nerves for special senses and those assisting skeletal muscle actions.
• Involves nerves 1, 2, 8, and 11 which don't fully align with traditional functions
• These nerves are responsible for our special senses

Cranial Nerve I (Olfactory Nerve)

• Smell
• Special Sense/Other classification

Cranial Nerve II (Optic Nerve)

• Vision
• Special Sense

Cranial Nerve III (Oculomotor Nerve)

• Eye muscles
• Medial

Cranial Nerve IV (Trochlear Nerve)

• Superior Oblique Muscle
• Medial

Cranial Nerve V (Trigeminal Nerve)

• Sensory and Motor function to face
• Lateral

Cranial Nerve VI (Abducens Nerve)

• Lateral Rectus Muscle
• Medial

Cranial Nerve VII (Facial Nerve)

• Facial Expression
• Lateral

Cranial Nerve VIII (Vestibulocochlear Nerve)

• Equilibrium
• Special Sense/Other

Cranial Nerve IX (Glossopharyngeal Nerve)

• Swallowing
• Lateral

Cranial Nerve X (Vagus Nerve)

• Autonomic functions
• Lateral

Cranial Nerve XI (Spinal Accessory Nerve)

• Neck and Shoulder Muscles
• Special Sense/Other

Cranial Nerve XII (Hypoglossal Nerve)

• Tongue Movement
• Medial

Cerebellum Meaning and Function

• Cerebellum means "little brain", is a smaller version of the cerebrum
• Coordinates voluntary movement, posture, balance, and muscle tone
• Facilitates skilled motor activities like riding a bicycle or walking a tightrope

Role in Communication

• Connects with the nervous systems, processes space, position and movement
• Aids to refine, correct, and enhance motor skills

Location of the Cerebellum

• Resides in the posterior cranial fossa near the brain stem
• The tentorium cerebelli separates temporal and occipital lobes

Structural Components of the Cerebellum

• Has two hemispheres, joined by a vermis
• Inferiorly, cerebellar tonsils exist parallel to the location with vermis
• Three lobes: anterior, posterior, and flocculonodular

Anterior Lobe (Spinal Cerebellum) Function

• Spinal cerebellum manages muscle tone and ongoing movement

Posterior Lobe (Cerebral Cerebellum/Pontocerebellum) Function

• Cerebral/ponto cerebellum supports fine motor movement
• Separated by horizontal fissure

Flocculonodular Lobe (Vestibular Cerebellum) Function

• Lateral
• Vestibular cerebellum maintains balance and posture
• Features include: nodule (central vermis part)
• Features include: and two flocculi

Cerebellar Peduncles

• They consist of 3 white matter stalks connect from brainstem stems, they include:
  • Superior
  • Medial
  • Inferior
• Sends efferent(CNS) and afferent(cerebellum) signals

The Superior Peduncle

• Links cerebellum-midbrain

The Medial Peduncle

• Links cerebellum-pons

The Inferior Peduncle

• Links cerebellum-medulla oblongata

Afferent Fibers

• Primarily use medial/inferior peduncles while efferent signals mainly use superior peduncles

Folia

• Has folds much like cerebrum (cortex folds cause sulci )
• Cortex folds form thinner layers than thinner layers than the cerebrum to become more parallel

Folia Cortex

• More surface area and helps fit the cortex in lesser area.
• Includes external gray matter (cerebellar cortex) and the subcortical white matter with a tree shape.

Arbor Vitae: The cerebellar cortex shape of the arrangement of white matter to organize a tree shape