Biology 109 Test Three Notes Chapter Eleven The Nervous System Has Two Principal Parts Central Nervous System CNS o Components brain and spinal cord o Functions receives processes and transfers information Peripheral Nervous System PNS o Components nerves outside CNS o Sensory division carries information towards the CNS o Motor division carries information away from CNS o Carried signals to and from skeletal muscles PNS CNS sensory neurons Understand Figure 11 1 CNS CNS interneurons CNS PNS motor neurons Effectors perform the body s response to motor output Overview of Nervous System Integrates and controls Two types of cells make up nerve tissue o Neurons are nerve cells specialized for carrying electrical signals from one part of the body to another o Glial cells support neurons and modify neuronal communication Cell Structure Cell body organelles Dendrites Axon o o Main part of the cell has nucleus and most of the cytoplasm and o Small slender extensions of the cell body receive incoming information and convey toward cell body Long slender extension specialized to conduct electrical impulses away from the cell body toward another neuron or effect o An axon ends in a cluster of branches each with bulb like synaptic terminal that relays signals to another neuron or an effector across a synapse Neurotransmitters are packages in vesicles Myelin Sheath Wraps around neuron like insulation Carried nerve impulses faster Myelin is rich in fact appears glossy white Multiple Sclerosis results from a dismantling of the myelin covering of CNS axons by the body s own immune system Neurological Cells Support Protect Axons Neuroglial cells make up 80 of nervous system Functions o Support o Protections o Do not transmit action potentials o Forms myelin sheath around axon Neurons Initiate Action Potentials Neurons generate and transmit action potentials An action potential is basically an electrical impulse Primary means of communication throughout the nervous system Action Potentials are All or none and Self Propagating All or none Individual neuron threshold sets extent of stimulus needed If it is achieves threshold it fires o o o Once triggered an action potential is always the same in form and voltage It must meet the threshold to fire o Self Propagating o Continues to propagate itself in the next region of the axon o Moves like a wave down the axon with constant speed and amplitude Strength of Action Potentials The number of action potentials unit time encodes the strength of the stimulus Stronger stimuli generate more action potentials unit time Information is transferred from Neuron to Target Targets another neuron muscle cell or gland Synapse special junction between axon terminus and target cell Synaptic transmission o Process of transmission of impulse from sending presynaptic neuron across synaptic cleft to receiving postsynaptic target Involves release and diffusion of chemical neurotransmitter o See Figure 11 8 Synaptic Transmission Neurotransmitter Release Steps to Synaptic Transmission Action potential arrives at axon terminus causing Ca2 to diffuse into axon bulb Ca2 causes release of neurotransmitter from vesicles Neurotransmitter diffuses across synaptic cleft Neurotransmitter binds to receptor on target postsynaptic membrane and opens gated channels Graded potential result from Na movement through opened channels Know Table 11 1 Acetylcholine Serotonin Dopamine Glutamate Endorphins Disorders of the Nervous System Trauma Concussion o Physical injury to brain or spinal injury o Blow to the head may lead to unconsciousness o Disruption of electrical activity in the brain o Risk of subdural hematoma Spinal cord injuries o Impairment of sensation and function below site of injury o Caused by viruses or bacteria that manage to pass through the blood Infection brain barrier Encephalitis Inflammation of the meninges caused by viral or bacterial infection Inflammation of the brain caused by viral infection o Meningitis o Rabies o o Spread by bite or saliva infected animal o Virus spreads from bite to brain via sensory neurons Infection viral disease Brain tumors o Abnormal growth in or on the brain o If nerves in the brain cannot regenerate how can there be brain tumors Multiple sclerosis MS o Progressive damage to myelin sheaths in brain and spinal cord o Weakness visual impairment incontinence Amyotrophic lateral sclerosis ALS o Progressive damage to myelin sheaths in motor area of spinal cord o Progressive weakening and wasting of skeletal muscle Epilepsy Alzheimer s disease o Recurring episodes of abnormal electrical activity seizures o Shortage of acetylcholine o Accumulation of abnormal protein beta amyloid o Progressive memory lapses and dementia Parkinson s disease Loss of dopamine releasing neurons o o Progressive degenerative disorder affecting motor activity Shaking Parkinson s is not related to info above does not involve memory loss or anything Michael J Fox has the Parkinson s listed above Major depression activities Schizophrenia o Extreme and persistent sadness and loss of interest in pleasurable o Prozac Zoloft blocks uptake of serotonin and elevates mood SSR o Effects about 1 of the world s population and distorts a persons perception of reality o Effects dopamine pathways and may alter glutamate receptors Bipolar disorder o Involves extreme mood swings Psychoactive Drugs Affect Higher Brain Functions Drug addiction alters the natural chemistry of the brain s reward system Psychoactive drugs o Affect states of consciousness emotions or behavior Action o Able to cross blood brain barrier o o Affect higher brain functions Influence concentrations or actions of neurotransmitters Psychological dependences is where the user craves the feeling associated with the drug Tolerance requires more of the substance to achieve the same effect Addiction is the need to continue obtaining and using a substance no free choice Withdrawal is the physical symptoms that occur upon stopping the drug Cocaine blocks dopamine re uptake Morphine heroin binds endorphin receptors Nicotine stimulates dopamine reduce number receptors thus need more Caffeine blocks adenosine receptor that tells system you need sleep Drug and the Brain Many drugs such as caffeine nicotine and alcohol act as synapses by increasing or decreasing the normal effect of neurotransmitters Prescription drugs used to treat psychological disordered alter the effects of neurotransmitters Alcohol blocks glutamate receptors