BIOL 2457 1st Edition Lecture 31Outline of Last Lecture The Brain and Cranial Nerves Outline of Current LectureThe Brain and cranial nerves THE PONS CN V, VI, VII, VIII (in part) Pneumotaxic Center – adjusts rate of rhythmicity centers in medulla oblongata  Apneustic Center - adjusts depth of rhythmicity centers in medulla oblongata Relay Centers – sensory & motor to the cerebellum Ascending, descending and transverse tractsReticular formation Extends from the upper part of the spinal cord, throughout the brain stem, and into the lower part of the diencephalon. Part of the reticular formation called the reticular activating system (RAS) consists of sensory axons that project to the cerebral cortex.  The RAS helps maintain consciousness.Midbrain or Mesencephalon Extends from the pons to the diencephalon. Part of the ventricle found here - cerebral aqueduct (mesencephalic aqueduct) Cerebral peduncles: axons of the corticospinal, corticopontine and corticobulbar tracts. Tectum- situated posteriorly and contains four rounded elevations: two superior ones called superior colliculi and two inferior ones called inferior colliculi. Mesensephalic Nuclei Substantia nigra - dopeamine Large area with dark pigments Helps control subconscious muscle activities Loss of neurons here is associated with Parkinson disease Red nucleus  Helps control voluntary movements of the limbs (tone) RAS headquarters – levels of consciousness  The tectum (roof) contains the corpora quadrigemina  Superior colliculi (visual information) and inferior colliculi (auditory information)Mesencephalic Axons  Cerebral peduncles – primary motor cortex info to brain, spinal cord &thalamus (axons of the corticospinal, corticopontine and corticobulbar tracts) Cranial Nerves CN III – Occulomotor IV – Trochlear (smallest # of axons, decussates, innervates a single muscle, longest intracranialThe Cerebellum Second largest part of the brain. The central constricted area is the vermis. The anterior and posterior lobes control subconscious aspects of skeletal movement. The flocculonodular lobe on the inferior side contributes to equilibrium and balance. The Cerebellum Cerebellar cortex- gray matter in the form of parallel folds called folia. Arbor vitae- tracts of white matter. Cerebellar peduncles- three pairs: superior, middle and inferior. Attach cerebellum to the brain stem. Functions: coordinates movements, regulates posture and balance.The diencephalon is composed of  Epithalamus - roof Hypothalamus - floor Thalamus - wallsThalamus Intermediate mass joins right and left halves of the thalamus Several nuclei Major relay station for most sensory impulses that reach the primary sensoryareas of the cerebral cortexHypothalamus Inferior to the thalamus. Consists of mammillary body, median eminence, infundibulum, and a numberof nuclei.Functions of the Hypothalamus Control of the ANS Production of hormones Releasing and inhibiting hormones (regulatory hormones of the ant. pit.)  ADH and oxytocin (post. pit. hormones from sup.op & paravent. nuclei) Regulation of emotional and behavioral patterns Regulation of eating and drinking Feeding and satiety centers  Thirst center Regulation of body temperature (preoptic nuclei) Is the body’s thermostat Regulation of circadian rhythms (suprachiasmatic nuclei) Serves as the body’s internal biological clock by regulating biological activityHYPOTHALAMUS Mamillary bodies – feeding reflexes (suckling) Autonomic centers – heart rate & blood pressure Tuberal nuclei – release regulating hormones [ant. pit.] Supraoptic nuclei – secretes ADH [post. pit.]  Paraventricular nuclei – secretes oxytocin [post. pit.] Preoptic nuclei – regulates body temperature Suprachiasmaic nuclei – circadian cycles Epithalamus Small region superior to the thalamus Consists of pineal gland which secretes a hormone called melatonin Melatonin induces sleep Contains habenular nuclei Involved in olfaction, especially emotional responses to odors The Cerebrum Function  “Seat of intelligence” Anatomy Cerebral cortex- gray matter White matter fiber tractsThe Cerebrum Gyri Cortical folds Sulci Shallow grooves Fissures  Deep grooves Longitudinal fissure – separates right&left hemispheresLobes of the Cerebrum Four lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe. Central sulcus- separates the frontal and parietal lobes. Precentral gyrus- primary motor area. Postcentral gyrus- primary somatosensory