The Brain and Cranial Nerves Largest organ in the body at almost 3 lb. Brain functions in sensations, memory, emotions, decision making, behavior

Principal Parts of the Brain Cerebrum Diencephalon –thalamus & hypothalamus Cerebellum Brainstem –medulla, pons & midbrain

Protective Coverings of the Brain Bone, meninges & fluid Meninges same as around the spinal cord –dura mater –arachnoid mater –pia mater

Blood Supply to Brain Uses 20% of our bodies oxygen & glucose needs –blood flow to an area increases with activity in that area –deprivation of O2 for 4 min does permanent injury at that time, lysosome release enzymes Blood-brain barrier (BBB) –protects cells from some toxins and pathogens proteins & antibiotics can not pass but alcohol & anesthetics do –tight junctions seal together epithelial cells, continuous basement membrane, astrocyte processes covering capillaries

Cerebrospinal Fluid (CSF) ml (3-5oz) Clear liquid containing glucose, proteins, & ions Functions –mechanical protection floats brain & softens impact with bony walls –chemical protection optimal ionic concentrations for action potentials –circulation nutrients and waste products to and from bloodstream

Origin of CSF Choroid plexus = capillaries covered by ependymal cells –2 lateral ventricles, one within each cerebral hemisphere –3rd ventricle –4th ventricle

Brain Stem Medulla Oblongata Pons Midbrain

Medulla Oblongata Nuclei of 5 cranial nerves Cardiovascular center –force & rate of heart beat –diameter of blood vessels Respiratory center –medullary rhythmicity area sets basic rhythm of breathing Reflex centers for coughing, sneezing, swallowing

Ventral Surface of Medulla Oblongata Ventral surface bulge –pyramids –large motor tract –decussation of most fibers left cortex controls right muscles

Dorsal Surface of Medulla Oblongata 5 cranial nerves arise from medulla -- 8 thru 12

XII = Hypoglossal Nerve Controls muscles of tongue during speech and swallowing

XI = Accessory Nerve Proprioception

X = Vagus Nerve Receives sensations from viscera Controls cardiac muscle and smooth muscle of the viscera Controls secretion of digestive fluids

IX = Glossopharyngeal Nerve Stylopharyngeus m. (lifts throat during swallowing) Somatic sensations & taste on posterior 1/3 of tongue

VIII = Vestibulocochlear Nerve hearing if damaged deafness or tinnitus (ringing) is produced sense of balance vertigo (feeling of rotation) ataxia (lack of coordination)

Pons One inch long help control breathing Cranial nerves 5 thru 7

VII = Facial Nerve facial muscles salivary & nasal and oral mucous glands & tears

VI = Abducens Nerve Movement of eye

V = Trigeminal Nerve muscles of mastication touch, pain, & temperature receptors of the face

Midbrain One inch in length Extends from pons to diencephalon

IV = Trochlear Nerve Movement of eye

III = Oculomotor Nerve Movement of eye

Cerebellum 2 cerebellar hemispheres Function –correct voluntary muscle contraction and posture based on sensory data from body about actual movements –sense of equilibrium

Cerebellum Cerebellar cortex = grey matter Arbor vitae = tree of life = white matter

Diencephalon Surrounds 3rd Ventricle Surrounds 3rd ventricle Superior part of walls is thalamus Inferior part of walls & floor is hypothalamus

Thalamus 1 inch long mass of gray mater in each half of brain Relay station for sensory information on way to cortex Crude perception of some sensations

Hypothalamus Mammillary bodies are relay station for olfactory reflexes; infundibulum suspends the pituitary gland Major regulator of homeostasis –receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood

Functions of Hypothalamus Controls and integrates activities of the ANS which regulates smooth, cardiac muscle and glands Synthesizes regulatory hormones that control the anterior pituitary Contains cell bodies of axons that end in posterior pituitary where they secrete hormones Regulates rage, aggression, pain, pleasure & arousal Feeding, thirst & satiety centers Controls body temperature Regulates daily patterns of sleep

Epithalamus Pineal gland –endocrine gland the size of small pea –secretes melatonin during darkness –promotes sleepiness & sets biological clock Habenular nuclei –emotional responses to odors

Cerebrum (Cerebral Hemispheres) Cerebral cortex is gray matter overlying white matter –2-4 mm thick containing billions of cells –grew so quickly formed folds (gyri) and grooves (sulci or fissures) Longitudinal fissure separates left & right cerebral hemispheres Corpus callosum is band of white matter connecting left and right cerebral hemispheres Each hemisphere is subdivided into 4 lobes

Lobes and Fissures Longitudinal fissure (green) Frontal lobe Central sulcus (yellow) Parietal lobe Occipital lobe Temporal lobe

Limbic System Emotional brain--intense pleasure & intense pain Strong emotions increase efficiency of memory

II -- Optic Nerve Connects to retina supplying vision

I -- Olfactory Nerve Extends from olfactory mucosa of nasal cavity to olfactory bulb Sense of smell