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Neurons I bet your neurons are all fired up now! The Nervous System NEURON = 1 cell Afferent, Efferent and Interneurons Example: Optic Nerve, Auditory Nerve Example: Nerve = a bundle of neurons Types of Neurons • Efferent (Motor) Neurons carry outgoing messages from the brain and spinal cord to the muscles and glands • Interneurons - neurons within the brain and spinal cord that communicate internally and between sensory inputs and motor outputs • Afferent (Sensory) Neurons carry messages from tissues and sensory organs to the brain and spinal cord for processing Neurons Neurons Neurons Neurons Neurons Neurons Neurons Parts of a Neuron Synapse (space between the neuron where chemical messages are sent to dendrites of other cells) Neurons How neurons communicate Neurons use an electro-chemical process to send messages • Why electrical? – Pushing information through axon is based on process of positive and negative charges of electrical atoms (ions) • Potassium (K+), Sodium (Na+), Chloride (Cl-) • Why chemical? – Neurotransmitters (chemicals) cross the synapse: different ones send different impulses and need to find receptors – It can either excite (fire) or inhibit (prevent firing) • Messages are sent at a speed of 2-200 mph • Neurons are altered with use (learning) – unused neurons die (“neural sculpting) How does a neuron fire The electrical impulse is called the action potential Step 1 - Resting potential – neuron is charged and ready to fire Polarized – positive outside, negative inside – (Na+) (Cl- & K+) Selectively permeable – gates do not allow sodium ions to pass through the cell membrane – Step 2 - Action potential – brief electrical charge that travels down the neuron Transmits neural messages to other neurons, muscles or glands When stimulated – depolarizes – – • Sodium (Na+) rushes in Step 3 - Repolarization – Potassium (Ka+) flows out repolarizing the Axon. Step 4 – Refractory Period – brief period of time when neuron won’t fire no matter how much stimulation • Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (Ka+) bringing axon back to a resting state Action Potential Action Potential Action Potential Action Potential Action Potential Electrical Transmission – The Action Potential http://outreach.mcb.har vard.edu/animations/ac tionpotential_short.swf How to generate a neural impulse 1. Neuron is stimulated by light, heat, pressure or chemical messages (neurotransmitters) from other neurons. 2. Signals from other neurons are either – – – Excitatory - tell neuron to fire (brings neuron closer to firing Inhibitory - tell neuron not to fire (brings neuron further away from firing) (excitatory) – (inhibitory) reach minimum threshold, (minimum energy needed for a neuron to fire) an action potential will occur 3. All or None Law – once the neuron fires the impulse moves down the action potential at the same intensity—it can’t be stopped Synapse Agonist Action Potential Resting Potential Refractory period 7 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 17 18 pe r. . . 0% to ry ot en t.. . nt i.. . ni st 14 fra c 6 Re 5 0% st in gP 4 0% Re 3 io n 2 Ac t 1 0% Ag o Sy na p se 0% Po te 1. 2. 3. 4. 5. A brief electrical charge that travels down the axon of a neuron is called the 19 20 What disease is related to degeneration of the neuron’s myelin sheath? 10 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 17 18 0% gt o n’ sD . .. r.. . er ... zh e ul ti M 14 Hu nt in 9 0% sc hi zo ph 8 0% D. 7 Al 6 C. 5 B. 4 pl e so n. .. rk in 3 pa 2 A. 1 0% ... 0% im A. parkinson’s disease. B. Multiple sclerosis. C. Alzheimer’s disease. D. schizophrenia. Huntington’s Disease 1. 2. 3. 4. 5. 19 20 The function of dendrites is to 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 na .. . t.. . ... 17 sig ain he na t ne 14 0% ns m it 10 18 tra 9 0% tro lp 8 co n 7 rd i 6 se 5 re le a 4 0% et . i.. co m in 3 ei ve 2 re c 1 0% ur ot . .. 0% co o 1. receive incoming signals from other neurons. 2. release neurotransmitters into the spatial junctions between neurons. 3. coordinate the activation of the parasympathetic and sympathetic nervous systems. 4. control pain through the release of opiate-like chemicals into the brain. 5. transmit signals to other neurons. 19 20 The movement of positively charged ions across the membrane of a neuron can produce a(n) Action potential Synapse Neurotransmitter Myelin sheath Interneuron 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 14 15 0% 17 18 rn eu r on th sh ea it t . .. 16 0% In te 7 0% M ye lin 6 ro tra 5 Ne u 4 Sy na p . te nt i.. po 3 io n 2 Ac t 1 0% se 0% ns m 1. 2. 3. 4. 5. 19 20 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 po pe r. . . to ry te n ti. . . .. . ive pe rm sh ol d Th re 14 17 fra c 7 18 Re 6 io n 5 Ac t 4 ec t 3 Se l 2 M 1 ye l in sh ea t h The axon of a resting neuron has gates that do not allow positive sodium ions to pass through the cell membrane. What is this characteristic called? 1. Myelin sheath 2. Threshold 3. Selective permeability 4. Action potential 0% 0% 0% 0% 0% 5. Refractory period 19 20 The minimum level of stimulation required to trigger a neural impulse is called the Reflex Threshold Synapse Action potential All-or-none response 5 6 7 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 14 15 17 18 .. re . on e po te nt i.. . se 16 0% or -n 4 0% Al l- 3 io n 2 0% Ac t 1 0% Th re sh ol d Re fle x 0% Sy na p 1. 2. 3. 4. 5. 19 20 Dendrites are branching extensions of Neurotransmitters Endorphins Neurons Myelin Endocrine Glands 4 5 6 7 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 0% n. .. in 0% in e M Gl a ye l ro ns ns or ph i En d 14 0% 17 oc r 3 0% 18 En d 2 Ne u 1 ro tra ns m it t . .. 0% Ne u 1. 2. 3. 4. 5. 19 20 How do neurons communicate with each other? The chemical process How Neurons Communicate How Neurons Communicate How Neurons Communicate How Neurons Communicate How Neurons Communicate Inhibition and Excitation Excitation – the process of making the neuron receiving neurotransmitters more likely to generate an action potential (fire) Inhibition – the process of making the neuron receiving neurotransmitters less likely to generate an action potential Excitation>Inhibition for neuron to fire Threshold – minimum stimulation for neuron to fire (-55 mV) Synaptic Transmission http://learn.genetics.utah.e du/content/addiction/rewar d/neurontalk.html Neurotransmitters Neurotransmitters – Chemical messengers in the brain. Different types affect the brain and behavior in various ways Excitatory neurotransmitters bring the dendrite closer to threshold by allowing positive ions to rush in. (ex. Glutamate) Inhibitory neurotransmitters take the dendrite further away from threshold by allowing negative ions to rush in (ex. GABA) Drugs can be….. • Agonists- mimic neurotransmitters • Antagonists- block neurotransmitters • Reuptake Inhibitors- block reuptake Acetylcholine (ACH) • Deals with motor movement, memory and learning. • Too much and you will…. • Too little and you will… • Lack of AcH has been linked to Alzheimer’s disease. • Black widow – increased AcH • Botox – decreased AcH • Curare – decreased AcH Dopamine • Deals with motor movement and alertness/attention, emotion, rewards. • Lack of dopamine linked to Parkinson’s disease. • Too much - linked to schizophrenia. Serotonin • Regulates sleep, dreaming, mood, pain, aggression, appetite and sexual arousal • Depression - Lack of serotonin • Anorexia = too much • Bulimia – too little Endorphins • Involved in pain control. • “endorphins make you happy” – runners high (emotions) • Drugs that mimic = . Agonists - Heroine, morphine, codeine Norepenephrine • Fight or flight response • Helps control alertness and arousal • Undersupply can depress mood GABA • Major inhibitory neurotransmitter meaning it keeps the neuron from firing (slows CNS) • Undersupply linked to seizures, tremors, insomnia • Alcohol consumption causes an increase in Gaba Glutamate • Major excitatory neurotransmitter Meaning… It causes neurons to fire – overactive CNS • Oversupply can over stimulate brain, producing migraines or seizures • MSG Drugs can be….. • Agonists- mimic neurotransmitters • Antagonists- block neurotransmitters • Reuptake Inhibitors- block reuptake Agonists and Antagonists http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/ i_03_m_par/i_03_m_par_cocaine.html#dro gues Agonist and Antagonists Examples: Agonists – Opiate Drugs Heroine, Morphine (Endorphins) Black Widow Spider Venom (AcH) Antagonists – Botulin (AcH), Botox (AcH), Curare (AcH) Reuptake refers to the 1. movement of neurotransmitter molecules across a synaptic gap. 2. release of hormones into the bloodstream. 3. inflow of positively charged ions through an axon membrane. 4. reabsorption of excess neurotransmitter molecules by a sending neuron. 5. the ending of the refractory period. Antidepressants such as Prozac target which neurotransmitter? m Do pa ac et yl GA B 0% in e 0% ch o. .. A. 0% D. glu ta m at n. .. B. ro to ni se 0% e. .. 0% C. A. serotonin. B. glutamate. C. GABA. D. acetylcholine. Dopamine A. 1. 2. 3. 4. 5. Lindsey has just played a long volleyball match after injuring her ankle in the first game, but feels little fatigue or discomfort. Her lack of pain is most likely caused by the release of Glutamate Dopamine Acetylcholine Endorphins Insuline 4 5 6 7 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 13 15 16 17 18 e 0% In su lin ns or ph i in e in e m 14 0% En d 3 0% ty lc h ol 2 0% Do pa 1 Gl ut a m at e 0% Ac e 1. 2. 3. 4. 5. 19 20 A person with schizophrenia may have an overactive dopamine system. Drugs used to treat this disorder prevent the action of dopamine by keeping it from binding to its receptors. These drugs are 1. 2. 3. 4. 5. Agonists Reuptakes Action Potentials Antagonists Synapses Neurotransmitters that bring a neuron closer to firing are called 1. 2. 3. 4. 5. Agonist Antagonists Inhibitory Reuptake Excitatory The Nervous System Central Nervous System • Brain • Spinal chord • Interneurons Peripheral Nervous System • All nerves that are not encased in bone. • Everything but the brain and spinal cord. • Motor and Sensory Neurons • Autonomic and Somatic Somatic Nervous System • Controls voluntary muscle movement. • Uses motor (efferent) neurons. Autonomic Nervous System • Controls the automatic functions of the body. – Lungs, stomach, intestines, liver, kidney, heart • sympathetic and the parasympathetic Sympathetic Nervous System • Fight or Flight Response. – Arouses and expends energy • Causes: – Increase in heart rate, breathing, dilates pupils, slows down digestion, relaxes bladder Parasympathetic Nervous System • Rest and Digest Response • Automatically slows the body down after a stressful event. • Causes: – Heart rate and breathing slow down, pupils constrict and digestion speeds up. The peripheral nervous system consists of: 6 7 8 9 10 21 22 23 24 25 26 27 28 29 30 11 12 14 15 16 0% .. n. or . at io ot fo rm nd ya re tic u lar sp in th e B. 13 se ns or 5 th e 4 C. 3 0% . ho rd ac ar e t io n so cia as 2 A. 1 0% m 0% 17 D. association areas. the spina chord. the reticular formation. sensory and motor neurons. as . A. B. C. D. 18 19 20 As Allison reaches for a box in her garage, out jumps a big spider. Her heart immediately begins to race as she withdraws her hand, but soon she realizes that the spider is harmless, and she begins to calm down. Which part of her nervous system is responsible for brining her back to a normal state of arousal? 28 29 30 vo . .. 27 17 18 19 ne r 26 16 ta l 25 15 le 24 14 0% sk e 23 13 pa 22 12 ym 21 11 ra s 10 pa 9 n. .. 8 at ic 7 so m 6 B. 5 th e 4 pa 3 sy m 2 A. 1 0% ... 0% t.. . 0% C. A. sympathetic nervous system B. somatic nervous system C. parasympathetic nervous system D. skeletal nervous system 20 Reflexes • Reflex - a simple, automatic, inborn response to a sensory stimulus – Normally, sensory (afferent) neurons take info up through spine to the brain. – Some reactions occur when sensory neurons reach just the interneurons in the spinal cord = reflex – Survival adaptation. A Simple Reflex A Simplified Neural Network Neurons learn to work together as a team. Neurons that fire together, wire together = learning The Endocrine System •A system of glands that secrete hormones. •Hormones are similar, but work a lot slower than neurotransmitters. •Neurotransmitter Neurotransmitters •nervous system •Speed = fraction of a second •Hormones •blood stream •Speed = several sec to travel from gland to tissue Hormones •Messages outlast neurotransmitters Master Gland:controls other glands Responsible for releasing growth hormones Controls pituitary gland Sends info to CNS Overactive = too thin Underactive = too fat Adrenaline or epinephrine and norepinephrine Hypoglycemia – low blood glucose/sugar Hyperglycemia -High blood glucose/suger (diabetes) Estrogen Testosterone Figure 3A.11 The endocrine system © 2011 by Worth Publishers