The Human brain The most complex mechanism known Human brain • 25 billion neurons • Require continuous supply of oxygen and glucose • If brain deprived of blood it results in damage (ex- stroke) • Hollow organ • Fluid filled spaces called ventricles The medulla • Most posterior portion of the brain stem • Continuous with the spinal cord • Consists of white matter (nerve tracts) and gray matter (cell bodies), carries messages to and from spinal cord • Motor fibers cross here, right brain controls lefts side of body, left brain controls right side. Medulla continued… • Gray and white matter known as the reticular formation extend from the spinal cord through the medulla and upward through the brain stem and thalamus. • It keeps cerebrum conscious and alert • Also houses several vital reflex centers Reflex centers of the medulla: • 1. cardiac centers that control heart rate • 2. vasomotor centers that help reg. blood pressure by controlling the diameter of blood vessels. • 3. respiratory centers that initiate and reg. breathing. The pons • Forms a bulge on the anterior surface of the brain stem. • Continuous with medulla. • Consists of nerve fibers passing from medulla to other parts of the brain. • Helps reg. respiration The midbrain • Shortest portion of brain stem. • Has bundles of neurons connecting the lower portion of the brain with spinal cord. • Contains reflex centers for vision and hearing. The diencephalon includes thalamus and hypothalamus • Thalamus – Major relay center – Controls all sensory info except smell • Hypothalamus – Control center of the autonomic center. Link between mind and body. – Links nervous system with endocrine system. – Produces 2 hormones: ADH (anti diuretic hormone) and oxytocin. Hypothalamus continued… • Oxytocin stimulates contraction of the uterus during childbirth and release of milk). ADH (prevents production of dilute urine) and oxytocin are stored in the posterior lobe of the pituitary gland. • Helps maintain fluid balance by reg. the volume of water excreted by the kidneys. Also contains a thirst center to let us know when we need fluids. • Regulates body temperature Hypothalamus continued… • Appetite and satiety (fullness) regualte food intake. • Influences sexual behavior, emotional aspects of sensory input, pleasure, and pain. The cerebellum • Responsible for coordination of movement • 2nd largest part of the brain • Contains 2 lateral masses called hemispheres and a connecting portion. • Helps make movements smooth and steady rather than trembling • Helps maintain muscle tone and posture • Impulses from the organ of balance (vestibular apparatus) in the inner ear are continuoulst delivered to the cerebellum which maintains equilibrium. The cerebrum • Largest part of the brain and most prominent. • Controls motor activities, interprets sensation, serves as the center of intellect, memory, language, and consciousness. • Divided into hemispheres • cerebral cortex- thin outer layer of the cerebrum, consists of gray matter Hemispheres of the cerebrum cont… Basal ganglia- lie within the white matter of the cerebrum, play an important role in movement. • The two cavities in the cerebrum are called the lateral ventricles. • The brain in folded into convolutions and in between them are shallow grooves called sulci and the deep pockets are called fissures. • The cerebrum is partially divided into right and left halves called the right and left cerebral hemispheres. They are separated by a deep groove called the longitudinal fissure. The cerebrum has sensory, motor, and association functions: • Sensory functions: receives info from sense receptors and interprets these messages • Motor functions: motor areas of the cerebrum are responsible for all voluntary movement and for some involuntary movement • Association functions: learning and reasoning, memory storage and recall, language abilities and even consciousness. Lobes of the cerebrum specialize in certain functions • Frontal lobe- motor cortex, formation of words. • Parietal lobe- receives info from skin and joints integrates info with visual, auditory and sensory association. • Occipital lobe- receives info from the thalamus about what we see and integrates the info in order to formulate an appropriates response. • Temporal lobe- reception and integration of auditory messages • Limbic lobe- a link between emotional and cognitive thought. • Central lobe- involved with somatic and autonomic activities.