Central Nervous System (CNS) CNS consists of the brain and spinal cord Four regions of the brain Cerebral hemispheres (cerebrum) Diencephalon Brain stem (midbrain, pons, and medulla) Cerebellum

Two Cerebral Hemispheres Surface markings Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) Five lobes Frontal Parietal Temporal Occipital Insula

Functional Areas of the Cerebral Cortex Left hemisphere is usually dominant connected with math and language skills, and logic Right hemisphere is connected with insight, visual-spatial skills and creativity

Diencephalon Three paired structures Encloses the third ventricle Thalamus Hypothalamus Epithalamus Encloses the third ventricle

Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interven- tricular foramen Posterior commissure Pineal gland (part of epithalamus) Anterior commissure Corpora quadrigemina Mid- brain Hypothalamus Cerebral aqueduct Optic chiasma Stop here day 1 Arbor vitae (of cerebellum) Pituitary gland Fourth ventricle Mammillary body Choroid plexus Pons Cerebellum Medulla oblongata Spinal cord

Thalamus 80% of diencephalon Gateway to the cerebral cortex Sorts, edits, and relays information Mediates sensation, motor activities, cortical arousal, learning, and memory

Hypothalamus Forms the inferolateral walls of the third ventricle Autonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility) Center for emotional response Involved in perception of pleasure, fear, rage and in biological rhythms and drives

Hypothalamus Regulates body temperature, food intake, water balance, and thirst Regulates sleep and the sleep cycle Controls release of hormones by the anterior pituitary Produces posterior pituitary hormones

Epithalamus Most dorsal portion of the diencephalon Pineal gland secretes melatonin Helps regulate sleep-wake cycles Choroid Plexus Produces cerebrospinal fluid

Brain Stem Three regions Midbrain Pons Medulla oblongata

Brain Stem Similar structure to spinal cord but contains embedded nuclei Controls automatic behaviors necessary for survival Contains fiber tracts connecting higher and lower neural centers Associated with 10 of the 12 pairs of cranial nerves

Superior cerebellar peduncle Pons Middle cerebellar peduncle Crus cerebri of cerebral peduncles (midbrain) Thalamus View (b) Infundibulum Superior colliculus Pituitary gland Inferior colliculus Trochlear nerve (IV) Trigeminal nerve (V) Superior cerebellar peduncle Pons Middle cerebellar peduncle Facial nerve (VII) Inferior cerebellar peduncle Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Olive Hypoglossal nerve (XII) Thalamus Vagus nerve (X) Diencephalon Hypothalamus Accessory nerve (XI) Midbrain Pons Brainstem Medulla oblongata (b) Left lateral view

Midbrain Located between the diencephalon and the pons Reflex centers for eye and head movement Cerebral aqueduct Channel between third and fourth ventricles

Pons Forms part of the anterior wall of the fourth ventricle The Pons is mainly a conducting area Nuclei help regulate respiration Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial)

Medulla Oblongata Joins spinal cord at foramen magnum Forms part of the ventral wall of the fourth ventricle Transmits all ascending and descending impulses Nuclei in the medulla regulate respiratory rhythm, heart rate, blood pressure Centers for coughing, sneezing, swallowing and vomiting are found here

The Cerebellum 11% of brain mass Dorsal to the pons and medulla Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction

Cerebellum Two hemispheres connected by vermis Each hemisphere has three lobes Anterior, posterior, and flocculonodular Coordinates skeletal muscle movement and maintains posture and balance

Functional Brain Systems Two networks of neurons that work together and span wide areas of the brain Limbic system Reticular formation

Limbic System Structures on the medial aspects of cerebral hemispheres and diencephalon Includes parts of the diencephalon and some cerebral structures that encircle the brain stem Produces emotions – anger, fear, conflict Modifies behavior

Reticular Formation Three broad columns of nuclei along the length of the brain stem Has far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum, and spinal cord Maintains an alert state in the cerebral cortex RAS (reticular activating system) Severe injury results in permanent unconsciousness (coma)

Protection of the Brain Four modes of protection Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier

Meninges Cover and protect the CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in the skull Three layers Dura mater Arachnoid mater Pia mater

Skin of scalp Periosteum Bone of skull Periosteal Dura mater Meningeal Superior sagittal sinus Arachnoid mater Pia mater Subdural space Arachnoid villus Blood vessel Subarachnoid space Falx cerebri (in longitudinal fissure only)

Cerebrospinal Fluid (CSF) Functions Gives buoyancy to the CNS organs Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals

Central Nervous System (CNS) Central cavity Outer white matter Spinal cord Central cavity surrounded by a gray matter core Mostly neuron cell bodies and unmyelinated fibers External white matter composed of myelinated fiber tracts Dense collections of myelinated fibers Inner gray matter Spinal cord

Spinal Cord Structure Spinal nerves Cervical and lumbar enlargements 31 pairs Cervical and lumbar enlargements The nerves serving the upper and lower limbs emerge here Cauda equina The collection of nerve roots at the inferior end of the vertebral canal

Spinal Cord Functions Two way communication between brain and body 1. Ascending Pathways carry sensory impulses to the brain 2. Descending Pathways carry motor impulses to muscles and glands

Spinal Cord Protection Bone, meninges, and CSF Cushion of fat and a network of veins in the epidural space between the vertebrae and spinal dura mater CSF in subarachnoid space

Cervical spinal nerves Cervical enlargement Dura and arachnoid mater Thoracic spinal nerves Lumbar enlargement Conus medullaris Lumbar spinal nerves Cauda equina Filum terminale (a) The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally. Sacral spinal nerves

Epidural space (contains fat) Pia mater Arachnoid mater Spinal meninges Subdural space Dura mater Subarachnoid space (contains CSF) Bone of vertebra Dorsal root ganglion Body of vertebra (a) Cross section of spinal cord and vertebra

Dorsal median sulcus Gray commissure Dorsal funiculus Dorsal horn White columns Ventral funiculus Gray matter Ventral horn Lateral funiculus Lateral horn Dorsal root ganglion Spinal nerve Central canal Dorsal root (fans out into dorsal rootlets) Ventral median fissure Ventral root (derived from several ventral rootlets) Pia mater Arachnoid mater Spinal dura mater (b) The spinal cord and its meningeal coverings

Gray Matter Dorsal horns—interneurons that receive somatic and visceral sensory input Ventral horns—somatic motor neurons whose axons exit the cord via ventral roots Lateral horns (only in thoracic and lumbar regions) –sympathetic neurons Dorsal root (spinal) gangia—contain cell bodies of sensory neurons

White Matter Consists mostly of ascending (sensory) and descending (motor) tracts Each spinal tract is composed of axons with similar functions