1011 multipolar neurons and countless fibers THE BRAIN 1011 multipolar neurons and countless fibers

Portions of the brain Cerebrum Cerebellum Brain stem

Cerebrum Split in half—cerebral hemispheres—separated by a layer of dura mater Corpus callosum connects the two hemispheres Ridges called convolutions Sulcus—shallow groove Fissure—deep groove Lobes of brain named after bones around them Frontal lobe, Parietal lobe, Temporal lobe, Occipital lobe

Cerebral Cortex Surrounds the outside of cerebrum (gray matter) 75% of active neurons in brain Beneath is a mass of white matter that connects to the rest of nervous system

Functions of Cerebrum Centers for interpreting sensory impulses, initiating voluntary movements, memory, ability to reason, general intelligence and personality stem from cerebrum Functional areas broken down into motor areas, sensory areas, and association areas (Figure 9.24) Hemisphere dominance Ventricles Diencephalon

Cerebellum Large mass of tissue below the occipital lobes of the cerebrum Two hemispheres and a cortex Functions Coordination and skeletal muscle movements Helps maintain posture Brings information on position of limbs and joints Communicates with cerebrum to move parts to desired positions Sends out impulses to midbrain to move the body

Brain Stem Three portions Midbrain Pons Medulla Oblongata Joins lower parts with higher parts Contains reflex centers for vision and hearing Pons Relays impulses from different parts of the brain and sensory impulses from PNS to cerebrum Small function in breathing rate Medulla Oblongata Three major activity centers: Cardiac, Vasomotor, and Respiratory Also centers for coughing, sneezing, swallowing, and vomiting

Throughout all of the brain stem is a complex network of fibers and gray matter called the reticular formation. It joins the hypothalamus with the rest of the brain and helps control sleep and wakefulness

Diencephalon Found between cerebral hemispheres—surrounds third ventricle Thalamus bulges into third ventricle Receives all sensory impulses going to brain and channels them to appropriate locations Hypothalamus—regions below the thalamus Regulates: heart rate/blood pressure, body temp., water/electrolyte balance, control of hunger, control of movements and glandular secretions, sleep and wakefulness Limbic System controls emotional experience and expression

Brain