Brain and Cranial Nerves Bio 40B Dr. Kandula

Brain Part of CNS Found in dorsal body cavity Continuous with spinal cord at foramen magnum The development and uniqueness of brain makes humans “superior” to other animals

Brain Enclosed and protected by the cranium and three membranes called meninges Dura Mater Arachnoid Mater Pia Mater

Meninges of Brain

Meninges Three membranes that surround and protect the brain Dura mater - outermost tough fibrous membrane - Made up of 2 layers : outer periosteal layer is attached to cranium; inner layer surrounds brain

Meninges of the Brain There are 3 inward folds of dura mater: Falx cerebri: Goes into longitudinal fissure separating two cerebral hemispheres Falx cerebelli: Separates the 2 hemispheres of cerebellum Tentorium cerebelli: Separates cerebrum from cerebellum

Meninges Arachnoid lies deep to dura mater and is separated from it by subdural space, this space contains small amounts of interstitial fluid. The arachnoid is an avascular layer. Pia mater lies deep to the arachnoid layer and is separated from it by the subarachnoid space. The subarachnoid space contains cerebrospinal fluid. The pia mater is tightly attached to surface of brain.

Brain Made up of 4 parts: The four parts include: cerebral hemispheres, diencephalon, brainstem and cerebellum.

Sectional view of Brain

Brain In humans the cerebrum is the most prominent part and makes up 70 % of the brain

Cerebrum Separated into two hemispheres by longitudinal fissure Falx cerebri found in fissure Corpus callosum (white matter fibers) connects two hemispheres at base of fissure

Cerebrum Gyri (pl) or gyrus (sing) are ridges Sulci (pl) or sulcus (sing) are shallow grooves – central sulcus, – parieto-occipital sulcus, – lateral sulcus Fissures are deeper grooves – longitudinal fissure – transverse fissure

Superior view of Brain

Cerebrum Cortex: Thin outer edge of gray matter (neuron cell bodies) Thick central core of white matter (axons) Four lobes – Parietal: receives sensory info – Frontal: voluntary motor – Occipital: vision – temporal: hearing, taste

Cerebrum Important gyri Precentral gyrus – primary motor area, ie. all impulses for voluntary muscular activities originate here. Postcentral gyrus – primary sensory area, ie., all general senses information perceived here

Functional areas to know: Primary motor, primary somatosensory, somatosensory association, vision, hearing

Diencephalon and Brain stem

Diencephalon 1.Thalamus  Mostly gray matter  Relays sensory info to cerebrum 2.Hypothalamus  “master gland” of body  Controls hormones, temp, emotion, thirst  Maintains homeostasis  Controls ANS functions 3. Epithalamus has pineal gland to control day/night cycles.

Brain Stem 1.Medulla oblongata  White matter of motor and sensory neurons  This is where neurons cross to opposite side of body - pyramids  Breathing and heart control 2.Pons means“bridge”  Bridge between medulla and midbrain  Also contains breathing center/helps regulate breathing 3.Midbrain  Corpora quadrigemina,( superior and inferior colliculi) controls reflexes associated with hearing and vision  cerebral aqueduct (with CSF)

Cerebellum

Also has 2 hemispheres connected by a body called vermis Function: coordination, balance and equilibrium Folds of gray matter  folia White matter arrangement characteristic and called arbor vitae

Cerebrospinal Fluid (CSF) Function: cushion/protect brain and spinal cord Made by the ependymal cells of choroid plexuses (small capillaries in the ventricles) Circulates through subarachoid space and the four ventricles Finally, CSF drains out the arachnoid villi back into the blood circulation

Circulation of CSF

4 Ventricles of brain with cerebrospinal fluid

Circulation of CSF Lateral ventricles  foramen of Munro  third ventricle  cerebral aqueduct  fourth ventricle  central canal of spinal cord or subarachnoid space surrounding brain and spinal cord

Cranial nerves

Part of the peripheral nervous system 12 pairs that mostly control head and neck Nerves contain motor neurons, sensory neurons, or mixed See handout

Number Name InnervationTypeFunction IOlfactoryTemporal lobe of brainsensorySmell IIOpticOccipital lobe of brainsensoryVision IIIOcculomotorEye muscles and ciliary body mixedMovement of eyeball IVTrochlearSuperior oblique muscle of eye mixedMovement of eyeball VTrigeminaltouch–pain– temperature to the face; motor division of the nerve supplies the muscles of mastication mixedTouch on face; mastication VIAbducenssupply a muscle called the lateral rectus muscle that moves the eye outward. mixedMovement of eyeball

Numb er NameInnervationType Action VIIFacial motor portion supplies all the facial musculature/ sensory portion, taste to the anterior two-thirds of the tongue; secretory to the lacrimal gland and salivary glands mixedfacial musculature, taste, and tears & saliva secretion VIIIAuditory Temporal lobe of brain sensoryHearing and equilibrium IX GlossopharyngealPharynx, tongue and salivary glands mixed TASTE POSTERIOR 1/3 TONGUE, SALIVATION, SWALLOWING XVagus Pharynx heart, respiratory tract, GIT, mixed GASTRIC PANCREATIC SECRETIONS, GI MOVEMENT, CARDIAC, RESPIRATORY AND VISCERAL REFLEX

NumberNameInnervationTypeAction XISpinal Accessory Muscles of neck and shoulder mixed MUSCLE MOVEMENT (sternocleidomastoid, trapezius) AND VISCERAL REFLEX XIIHypoglossalTongue musclesmixedTongue movement