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Chapter 10 – Central Nervous System The Brain and Spinal Cord An amazing part of the body that can take millions of bits of information and make sense of it Amazing Brain Trick #1 Slide 3 I. Central Nervous System A. Coverings of the Br. & Sp. C 1. Bones a. Skull encases the brain b. Vertebrae encases the spinal cord 2. Meninges a. Dura mater – literally means “hard mother”, inside layer of the bone b. Arachnoid membrane – delicate cob webby membrane in the middle of the brain c. Pia mater – contains blood vessels, the layer next to the spinal cord 3. Spaces between the meninges a. Epidural space – “on the dura”, between the bones and outside the dura mater b. Subdural space – between the dura mater and arachnoid c. Subarachnoid space – between arachnoid and pia mater, space that contains the CSF B. CSF Cerebrospinal Fluid Cushion of fluid around and within the brain and spinal cord 1. Path of CSF Fluid filtered from the blood in the capillaries Circulates through brain ventricles Into the canal of the spinal cord Where it is absorbed back into the blood 2. Total amount of CSF 140 ml At all times Amazing Brain Trick #2 Count the number of “F”s in this sentence! ANSWER: There are 6 F’s in this sentence C. Spinal Cord 1. Structure a. Extends from foramen magnum to 1st lumbar vertebrae, ~18 in long. b. Nerve roots exit the spinal cord 1. Dorsal nerve roots carry sensory information to the spinal cord (right and left) 2. Ventral nerve roots carry information out of the spinal cord (right and left) 2. Function of the spinal cord a. Provides conduction routes to and from the brain 1. Ascending tracts – conduct impulses up the cord to the brain 2. Descending tracts – conduct impulses down the cord from the brain D. Brain 1. Anatomy a. Weighs about 3 pounds b. Neurons do not undergo mitosis except during prenatal and a few months postnatal VIDEO GAMES c. There are six regions 1. Medulla oblongata 2. Pons 3. Midbrain 4. Cerebellum 5. Diencephalon 6. Cerebrum (cerebral cortex) 2. Brainstem a. Medulla oblongata – attaches to the spinal cord. Most vital part of the brain because it contains the vital centers (respiratory, cardiac, and blood pressure) and vomiting, coughing, sneezing, hiccuping b. Pons – helps to regulate respiration and reflexes of 5th (V), 6th (VI), 7th (VII), and 8th (VIII) cranial nerves c. Midbrain – contains centers for certain cranial nerve reflexes (pupil and eye movement) 3. Cerebellum – controls skeletal muscles a. Produces skilled movement by coordinating groups of muscles b. Maintains balance (lack would be = staggering). That is why the police have you walk a “straight line” in a sobriety test. c. Control’s posture and coordinated movements (lack would be ataxia = overshooting the mark)….that is why you touch your alternating fingers to your nose) d. Alcohol directly inhibits the cerebellum’s function in the body 4. Diencephalon – contains thalamus and hypothalamus a. Thalamus – relay station from sensory impulses to brain 1. Sensations of pain, temperature, touch 2. Emotions – pleasantness and unpleasantness 3. Arousal or alerting mechanism (maintaining awake states) b. Hypothalamus – link between psyche (mind) and soma (body). For instance, pleasure center for primary drives eating (appetite), drinking, sex. Also is crucial part of mechanism for maintaining normal body temperature 5. Cerebrum a. Structure 1. Divided into right and left hemispheres 2. Four lobes a. Frontal b. Parietal c. Temporal d. Occipital Convolutions (gyrus) – means “sausages”…folds in the brain 4. Brain communication pathways a. Projection tracts – extension connecting to the ascending and descending tracts b. Association tracts – connect from one convolution to another c. Commissural tracts – communicate from one hemisphere to the other 3. b. Function of cerebrum 1. Sensory function of cortex a. Somatic senses– touch, pressure, temperature, body position b. Cortex contains sensory map of the body– notice face and hands which has a lot of nerve receptors c. Special senses– vision, hearing Motor function of cortex – controls muscle movements 3. Integrative function of cortex a. Consciousness – who you are and how others are. Varying levels of consciousness include fully awake, SWS(Slow wave sleep-dreamless), REM (rapid eye movement-dreaming), altered states of consciousness (coma) b. Language – ability to speak and write words and understand spoken and written words 2. Emotions – subjective experience and objective expressing of emotions 5. Memory – capable of storing and retrieving short term and long term information 6. Specialization of hemispheres 4. a. Left – language and dominant hand movements in 90% of population. You can determine a persons dominant hand by watching them talk in most cases. b. Right – perception of nonspeech auditory stimuli – coughing, crying, laughing E. Diagnostic Tools 1. Lumbar puncture (AKA: Spinal Tap)– withdrawal of CSF with a needle inserted around the 4th lumbar vertebrae (to keep from hitting the spinal cord directly). Patient lies on their side, drawing knees up to chest which separated the vertebrae for insertion. Used to detect bacterial infections, etc. 2. EEG – electroencephalogram – measures brain waves. 2 flat EEG with in 24 hours apart with no spontaneous breathing (without respirator) = brain dead EEG F. Disorders 1. CVA- cerebrovascular accident (stroke) – oxygen is cut off from part of the brain and cause the neurons to cease to function. Paralysis appears on opposite side of the body than the damage to the brain. 2. Cerebral Palsy (CP) – damage to motor areas. They can often talk and are smart, but can be mistaken for mentally retarded due to the need for helmets (since the cannot control their body movements) and their look. 3. Dementia – general term for “losing your mind”….boxers who have received too many blows to the head a. Alzheimers – increasing loss of memory (forget to turn off stove after cooking or water after washing their hands). This progresses to infantile behavior….they will often talk about their “past”….what they can remember. b. Huntington’s Disease – genetic disorder characterized by chorea (involuntary purposeless movement)….this goes into severe dementia and eventually death. 1st symptoms do not appear until 30-40 years old (by that time you’ve usually populated and spread the gene). 4. Seizure Disorders – seizures are sudden bursts of neural activity – may be mild, zoning out (petit) to severe full blown with convulsions (tonic clonic). You can have isolated seizures due to high temperatures, over-stimulation of neurons from video games, TV shows ….but if it recurs and becomes chronic then it is termed epilepsy. 5. Meningitis – inflammation of the meninges. Neck becomes stiff, fever, headache. If only the spinal meninges are affected, then it is called spinal meningitis. Death can occur within 24 hours of onset of symptoms. 6. Hydrocephalus – “water on the brain” – CSF accumulates in the brain due to blockage (tumor) and it can’t be drained…yet the mechanism for making more won’t shut off, so you have an overabundance. Head can become the size of a basketball. If occurs in infants (unossified skull can accommodate hydrocephalus better than adults) – treatment would be placing a “stunt” in the brain to pump out the extra CSF. Results in coma or death in adults. 7. Parkinsons – is a decrease of output of neurotransmitter, dopamine. Dopamine’s function is to inhibit or turn off the excitatory effects of another neurotransmitter, acetylcholine (ACH). Without dopamine, the excitatory affects of ACH are not restrained and it results in excess signals going to voluntary muscles. Symptoms are tremors in head, limbs, a shuffling gait, and forward tilt of trunk. 8. West Nile VirusAbout 20 percent of people develop a mild infection called West Nile fever (80% are unaffected). Common signs and symptoms of West Nile fever include: Fever, Headache, Body aches, Fatigue, Skin rash (occasionally), Swollen lymph glands (occasionally), Eye pain (occasionally) Serious infection signs and symptoms In less than 1 percent of infected people, the virus causes a serious neurological infection. Such infection may include inflammation of the brain (encephalitis) or of the brain and surrounding membranes (meningoencephalitis). Serious infection may also include infection and inflammation of the membranes surrounding the brain and spinal cord (meningitis), inflammation of the spinal cord (West Nile poliomyelitis) and acute flaccid paralysis — a sudden weakness in your arms, legs or breathing muscles. Signs and symptoms of these diseases include: High fever, Severe headache, Stiff neck, Disorientation or confusion, Stupor or coma, Tremors or muscle jerking, Lack of coordination, Convulsions, Pain, Partial paralysis or sudden weakness