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HSCI 100 (134)
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week 8.docx

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Department
Health Sciences
Course
HSCI 100
Professor
Nienke Van Houten
Semester
Summer

Description
CHAPTER 8 – NERVOUS SYSTEM Peripheral nervous system (PNS) - Peripheral nerves – sensory & motor, spinal nerves – sensory & motor - Somatic nervous system o Nerves that carry info to and from CNS = sensations + voluntary movement o Carry somatic nerves result in conscious sensations, light sound touch o Tells us about world around and within us - Autonomic nervous system o Governs involuntary, subconscious activates that keep body function (HR, breathing rate)  Sympathetic nervous system – stressful/emergency conditions  Parasympathetic nervous system – governs bodily activities during restful conditions Central nervous system (CNS) - Spinal cord, brain (Cranial nerves) protected by bony cases (skull and vertebral column), membranes (meninges), fluid cushion (cerebrospinal fluid) o Meninges – 3 connective tissues covering brain and spinal cord  Outer = dura mater, middle = arachnoid, inner = pia mater o Cerebrospinal fluid – fills space btwn meninges and internal cavities of brai (ventricles) & internal cavities of spinal (central canal)  Functions: shock absorption, support, nourishment/waste removal o Blood-brain barrier  Selects substances permitted to enter cerebrospinal fluid from blood - All voluntary/involuntary THE BRAIN - Cerebrum o Contains sensory areas for skin senses, vision, hearing, olfaction o Motor area for voluntary control of movement o Association areas for interpreting sensations, language, thinking, decision making, self-awareness, creativity, memory  Thin outer layer = cerebral cortex  Gray mater = unmyelinated axons  White matter = myelinated axons  Frontal, parietal, temporal, occipital lobes - Corpus callosum o Allows L&R cerebral hemispheres to communicate - Thalamus o Processes all sensory info except olfaction o Relays info to appropriate higher brain centers - Hypothalamus o Controls HR, bP, breathing rate, body temp, food intake o Center for emotions o “master biological clock” - Cerebellum o Coordinates sensory-motor voluntary movement o Stores memory of learned motor patterns - BRAINSTEM o Midbrain – relays info btwn cerebellum/spinal cord & cerebrum, integrates sensory input o Pons – bridge btwn higher/lower brain center o Medulla oblongata – contains autonomic ctrs for HR and digestive activities, relays sensory info thalamus LIMBIC SYSTEM – term for group of structures that help to produce emotions/memory - Feelings about thoughts - Short-term memory – holds small amt of info for few seconds/mins - Long term-memory – seemingly limitless amounts of info for hrs, days yrs, - Olfactory bulb transmits info about odors from nose to limbic system THE SPINAL CORD - Tube of neural tissue continuous with medulla at base of brain to below last rib - Function – transmit messages to and from brain, serve as reflex center - White matter found toward surface of spinal cord – grouped into tracts (ascending/descending tracts) - Reflex arc – receptor, sensory neuron, interneuron, motor neuron  effector o 1. Stimulus initiates a pain sensation o 2. Sensory messages are carried to spinal cord by sensory neuron o 3. Interneurons in the spinal cord integrates information from sensory neuron and stimulate appropriate motor neurons o 4. Motor neurons stimulate appropriate muscles o 5. Leg muscles contract, causing them to lift the foot off glass Reticular Activating System (RAS) – extensive network of neurons that runs through medulla and protects cerebral cortex - Activates cerebral cortex DISORDERS OF NERVOUS SYSTEM Headaches - Tension headache – response to stress most of us unconsciously contract muscles of our head, face, neck - Migraine headaches – confined to one side often centered behind one eye. Throbbing pain increases with each beat of heart. Experience an aura (visual disturbance, hallucinations, numbness) Strokes - Cerebrovascular accident – death of nerve cells caused by interruption of blood flow to a region of the brain - Neurons die b/c no oxygen and glucose - Causes? Blood clots, hemorrhage Coma - Person totally unresponsive to all sensory input and cannot be awakened - Cause? Trauma to neurons in regions of brain responsible for stimulating cerebrum, particular in RAS & thalamus - Can be caused by mechanical shock – blow to the head, tumors, infections, drug OD, failure of liver/kidney Spinal Cord Injury - Spinal cord = pathway that allows brain to communicate with rest of body o Damage to spinal cord = impair sensation & motor control below site of injury - Result? Damage, injury, paralysis, loss of sensation Mechanoreceptors – action potentials from physical formation and reformation Corpuscle – rounded globular mass of cells - Meissner’s (tactile) corpuscles o Light touch o Low frequency vibrations (<50Hz) o Concentrated in fingers, lips, palms, soles o Action potential from physical deformation o Adapt rapidly  Why you stop feeling your clothes - Pacinian (lamellar) corpuscles o Pressure o Vibration – 250 Hz o Silkiness of silk o Smoothness of finished wood o Roughness of concrete - Ruffini’s (bulbous) corpuscles o skin stretch o kinesthetic sense of finger position and movement o monitors slippage of objects on skin  grip modulation o sustained pressure with little adaptation  you do not feel the steering wheel - merkel’s discs o low frequency vibration 5-15Hz o sustained response o sense very small displacement o high resolution tactile discrimination  braille, cotton vs burlap - free nerve endings = pain Medulla - autonomic functions o breathing – chemoreceptors o heart rate – sympathetic, parasympathetic o blood pressure – vasomotor baroreceptors o vomiting, coughing, sneezing, swallowing Pons - relay station: forebrain to cerebellum o sleep, respiration, swallowing, bladder control, hearing, taste, balance posture, facial expressions and sensation, eye movement Midbrain - substantia nigra o dopamine – motor control, motivation, habituation - relay of vision and hearing Thalamus - great relay station of the brain - all ascending tracks terminate here - thalamus  cortex, cortex  thalamus Cortical columns - basic computational element of the cortex - 6 neuron layers deep Cranial nerves - Special senses: smell (olfactory cortex), sight, hearing, taste (gustatory cortex). Facial motor After sensation comes response - Super fast response: reflexes - Fast response: limbic system - Slow response: cortical system Functions Amygdala - Positive/negative colouring of events - Memory modulation, sex, rage, social networks Cingulate gyrus - Links behavioural outcomes to motivation “it felt good when I learned to ride my bike” Nucleus accumbens - Pleasure dome: anticipates positive sensations. Euphoria in sex, drugs alcohol Insula - Integration of body’s emotional tone – craving, addiction, social violations, empathy, orgasms Cerebellum - Principal role in motor coordination - May be involved in fear/pleasure regulation - As many neurons as rest of brain Marshmallow test video – impulse (generated by limbic system) somehow being kept (or not) at the bay Frontal lobes - Executive function: o Regulation emotion o Impulse control o Interpersonal function o Planning Neuromodulation – shift overall +/- tone - Primary neurotransmitters = glutamate (excitatory +), GABA (inhibitory -) - Neuromodulators = dopamine, serotonin, norepinephrine, acetylcholine Dopamine: reward seeking behavior - Motivation to behave in certain ways o Reward from basic drive fulfillment: food, sex, drugs, learned stimuli - Craving and euphoria in addiction - Movement - Cognitive function - Social behavior - Dopaminergic drugs – Adderall, cocaine, crystal met, Dexedrine, Ritalin Serotonin – regulation of mood, appetite, sleep - Cognitive functions – memory/learning - Serotonergic drugs – turkey sandwiches, SSRI antidepressants, DMT, MDMA, LSD, mescaline Noradrenaline - Focuses attention = decision making - Fight or flight (sympathetic nervous stem) - Amygdala on-switch Acetylcholine - Memory - Muscle – neuromuscular junction - Parasympathetic system – rest & digest - Drugs = nicotine, acetyl cholinesterase inhibitors -  pharmacology o 1. Ach made from choline + acetyl CoA o 2. In synaptic clef, Ach rapidly broken down by enzyme acetyl cholinesterase o 3. Choline transported back into axon terminal and is used to make more ACh - Corpuscles – - Vesicles – acetylcholine - Motor cortex  pons  cerebellum (secondary input) - Dopamine – reward system - How many cortical columns are In the human brain -2 mil - Motor control – front , sensation in back == association cortex CHAPTER 8A – DRUGS & THE MIND DRUG DEPENDENCE - Tolerance: progressive decrease in effectiveness of a drug in a given person o Develops b/c body naturally steps up production of enzymes to break down drug, disabling it from having continued effect, o Also b/c changes in nerve cells - Cross tolerance: tolerance to one drug results in a lessened response to another - Dependence: state in which drug is necessary for physical/psychological well-being o Withdrawal symptoms Alcohol - Alcohol = ethanol. By-product of fermentation when yeast cells break down sugar to release energy for their own use - Absorption: o Absorbed from digestive system and into blood, delivered to brain o 20% absorbed in stomach, remaining = intestines - Distributed to all body tissues. Ethanol soluble in both fat & water - Elimination: o 95% that enters is metabolized and broken down before eliminated (in liver)  Converts alcohol to co2 & water o 5% eliminated unchanged through lungs/urine - Health related effects: o Nervous system – alcohol is a depressant  Slows activity o liver - fat accumulates  fat blocks blood flow == inflammation (hepatitis)  fibrous scar tissue forms (cirrhosis) == intestinal bleeding, kidney failure, fluid accumulation o cancer – tongue, mouth, esophagus o hearts & blood vessels – too much alcohol = reduce heart ability to pump blood, promote deposit of fat in blood vessels, higher bP  damage heart muscle, blood vessels clogged, high blood pressure == enlarge heart MARIJUANA THC receptors in brain - mimics anandamide – internal bliss – regulation of mood, memory, pain, appetite, movement - stimulates release of dopamine in reward pathways Health related effects of long term use - usually smoked, residual materials in smoke is harmful (not THC) - more tar buildup, carbon monoxide prevents RBC from carrying oxygen to cells of body - makes heart beat faster - interfere with reproductive functions STIMULANTS – excite CNS Heroin – acts in brain regions where neurons communicate using endorphins LSD & MDMA – act in brain regions where neurons communicate us
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