Central Nervous System 1-2 min interruption of blood flow may impair brain Brain & Spinal Cord cells >4 min w/o oxygen ! permanent damage Brain besides O2 must get continuous supply of glucose one of largest organs in body: very little in reserve men: 1,600 g (3.5 lbs) decrease in glucose: women: 1,450g (3.2 lbs) dizziness [size is proportional to body size not intelligence convulsions ! Neanderthals had larger brains than us!!] unconsciousness early thoughts on function of brain: The Brain is Subdivided Into: ancient Greeks weren’t particularly impressed with the brain where snot was generated cooling device for blood 1. Cerebral Hemispheres (60% of brain mass) neurons divide only during prenatal development and a few months - “human” part: thought, creativity, after birth communication after that they increase in size, but not numbers 2. Diencephalon moods, memory, manages internal environment one of most metabolically active organs in body epithalamus thalamus comprises only 2% of total body weight it yet hypothalamus ! gets 15% of blood 3. Cerebellum – coordinating movement and balance !consumes 20% of our oxygen need at rest 4. Brain Stem – oldest and smallest region, basic bodily (more when mentally active) functions = vegetative functions midbrain blood flow and O2 increase to active brain areas pons medulla Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 1 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 2 cardiac reflex center Some General Terminology for CNS: rate and force of heartbeat vasomotor control center gray matter = thin myelin; mostly cell bodies controls diameter of blood vessels dendrites & synapses controls the distribution of blood to specific organs controls blood pressure -outer layer of brain = cortex -inner layer of spinal cord respiratory center -nuclei: small areas of gray matter deeper inside the regulates the rate and depth of breathing brain polio especially affects this center in medulla ! resp failure (iron lungs) White matter = thick insulation; mostly axons also contains many nonvital reflex centers (nuclei): -inner layers of brain: nerve tracts = bundles of speech axons that interconnect various parts of the brain swallowing -outer layer of spinal cord vomiting coughing Brain Stem sneezing hiccuping 1. Medulla 2. Pons lowest portion of brainstem just above medulla continuous with the spinal cord bridge connecting spinal cord with brain and parts all ascending and descending tracts from spinal of brain with each other cord and brain = white matter contains 2 centers that help to regulate breathing most tracts cross over as they pass through the medulla ! pneumotaxic center ! apneustic center helps control several vital functions ! contains important autonomic reflex centers also contains nuclei that affect sleep and bladder control Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 3 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 4 Parkinsons Disease 3. Midbrain progressive loss of motor function begins in 50’s or 60’s can be hereditary in the form of 4 lobes above and behind pons due to degeneration of dopamine releasing neurons in = Corpora Quadrigemina substantia nigra (inhibitory neurons) leads to hyperactivity of basal nuclei and involuntary muscle contractions upper 2 lobes = Superior Colliculi results in shaking hands, facial muscles become rigid, range of motion decreases develops smaller steps, slow shuffling gait with forward bent control center for some visual reflexes: posture and a tendency to fall forward speech becomes slurred, handwriting illegible a. pupillary reflex b. reflex centers for coordinating eye movement with head and neck 4. Reticular Formation (~Reticular Activation System) movement in response to visual stimuli diffuse system of interconnecting fibers extending through several areas of brain including brain lower two lobes = Inferior Colliculi stem -comprises a large portion of entire brainstem control center for some auditory reflexes: -extends into spinal cord and diencephalon -interlacing of gray and white matter a. reflex centers for movements of head and trunk in response to Functions of RAS - both sensory and motor auditory stimuli to locate sound 1. Sleep and consciousness b. startle response to loud noises maintains consciousness and awakens from also contains: sleep ! alarm clock barbiturates depress RAS, decrease alertness & substantia nigra ! suppresses unwanted produce sleep muscle contractions amphetamines stimulate RAS producing wakefulness Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 5 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 6 general anesthetics may produce unconsciousness by and intermediate mass depressing RAS falling asleep may be caused by specific mainly a sensory relay center neurotransmitters that inhibit RAS ! “Rome of the Nervous System” 2. helps control muscle tone, balance or “gateway to cerebral cortex” and posture during body movements ! main relay station for sensory impulses 3. filters flood of sensory input that reach cerebral cortex from spinal (=habituation) cord, brain stem and cerebellum highlights unusual signals; disregards rest eg. taste, touch, heat, cold, pain, some smell (99%) the only sensory signals that can reach the cortex without going through the thalamus are LSD interferes ! get flood of sensory stimuli for sense of smell Diencephalon 3. Hypothalamus 1. Epithalamus part of the brain most involved in regulating internal environment includes roof of 3rd ventricle no blood brain barrier mainly pineal gland forms floor and part of lateral walls of 3rd ventricle 2. Thalamus: a. link between “mind” and “body” 4/5ths of diencephalon controls and integrates activities of autonomic 1.2” long NS forms lateral walls of 3rd ventricle means by which emotions express themselves by altering body functions Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 7 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 8 ! ?role in psychosomatic illnesses limbic system perception & output is geared mainly toward the experience and expression of b. relays reflexes related to smell emotions c. manufactures and transports releasing eg. pain, anger, fear, pleasure hormones that control the “Master Gland” continuous back & forth communication between limbic system and frontal lobes of cerebrum ! anterior pituitary ! much of the richness of your emotional life e. regulates body temperature depends on these interactions has receptors that monitor blood temperature outward expression of these emotions requires participation of the hypothalamus f. regulates food and water intake all sensory impulses are shunted through the has receptors that monitor osmotic pressure limbic system ! thirst center smell is directly wired to limbic system other receptors monitor some hormone concentrations in blood produces a crude appreciation of some sensations; 4. Limbic System eg. pleasure, anger, pain but can’t distinguish their location or intensity diencephalon is a main part of a diffuse group of structures called the Limbic System eg. contains pleasure center includes thalamus, hypothalamus, hippocampus, -rats pressing bar for stimulation of pleasure center midbrain, amygdala (cerebrum), mammalary body (relay -ignore sleep, food, water, sexual partners center from limbic system to thalamus), fornix (connects -continue until exhausted (50-100x’s/min) hippocampus to mammalary body of hypothalamus) -willing to cross electrified grid to seek reward [420 !amps vs 60-180 !amps for food] = the emotional brain in humans stimulates erotic feelings Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 9 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 10 smooths and coordinates complex sequences of opioids and endorphins are concentrated in muscular activity needed for body movements limbic pathways 2. controls skeletal muscles to maintain balance !is site of action of many addictive receives input from proprioceptors in muscles, drugs tendons and joints and equilibrium receptors and eyes Cerebellum ! compares intended movement with actual movement 2nd largest part of brain 3. learning and storing motor skills just below and posterior to cerebrum eg. playing musical instrument, riding a bike, typing, etc only other part of brain that is highly folded 4. recent research indicates that the cerebellum also has roles in awareness, emotion and judging the passage of time consists of 2 hemispheres diseases of cerebellum produce Ataxia grey matter outside eg. tremors speech problems white matter inside difficulty with equilibrium = arbor vitae (tree of life) NOT paralysis Functions of Cerebellum: Cerebral Hemispheres helps to coordinate voluntary muscles: largest portion of brain (~60% of brain mass) but does not send impulses directly to muscles two hemispheres joined by tracts = corpus callosum 1. acts with cerebrum to coordinate different heavily convoluted: gyri and sulci groups of muscles Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes, 2010.4 11 Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser, Lecture Notes,