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Neurons I bet your neurons are all fired up now! The Nervous System Neuron = 1 cell • Example: Afferent, Efferent and Interneurons Nerve = a bundle of neurons • Example: Optic Nerve 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 Think Pair Share • Explain which neuron’s are at work when you swat a mosquito • Which neurons are at work when you pick up a fork? Warmup • Think of an example (not one we discussed in class) where you are using a) Afferent neurons b) Efferent neurons c) Interneurons Neurons Neurons Neurons Neurons Neurons Neurons Neurons How neurons communicate Electro-Chemical process 1. Electrical – within a neuron – Action Potential – brief electrical charge that sends a message down the neuron • Information is pushed through the axon based on process of positive and negative charges of electrical atoms (ions) – Potassium (K+), Sodium (Na+), Chloride (Cl-) 2. Chemical – between neurons – Neurotransmitters (chemicals) travel across the synapse: different ones send different messages on to the next neuron • Neurotransmitters can either excite (fire) or inhibit (prevent firing) • Messages are sent at a speed of 2-200 mph How does a neuron fire Step 1 : Resting potential – neuron is charged and ready to fire (-70mv) – Polarized – positive outside, negative inside (Na+) (K+) – Selectively permeable – gates do not allow sodium ions to pass through the cell membrane Step 2: Threshold – the minimum energy needed to generate an action potential (-55mv) – Excitation- the process of making a neuron more likely to generate an action potential (excitatory neurotransmitters binding to receptors) must be greater than – Inhibition – the process of making the neuron less likely to generate an action potential (inhibitory neurotransmitters binding to receptors) Step 3: Action potential – brief electrical charge that travels down the neuron – Depolarizes - Sodium (Na+) rushes in creating a positive charge on the inside of the cell membrane. – All or None Response – neurons can only send message in one direction at the same speed and strength – Repolarization - Potassium (K+) flows out of the cell membrane, reversing the polarity – Step 4: Refractory period - the recharging period that must occur to ready a neuron to generate another action potential – Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (K+) bringing axon back to resting potential Action Potential Electrical Transmission – The Action Potential http://www.outreach.mc b.harvard.edu/animatio ns/actionpotential_shor t.swf Between Neuron Communication • Neurotransmitters – the chemical messengers that carry information across the synapse between one neuron and then next are released from terminal buttons on the sending neuron Can be: – Excitatiatory Neurotransmitters – make the neuron receiving neuron more likely to generate an action potential • Glutamate – Inhibitory Neurotransmitters – make the neuron receiving neurotransmitters less likely to generate an action potential • GABA • Synapse – the small gap between neurons which neurotransmitters travel across to send a message to the receiving neuron’s dendrites • Reuptake – the process of the sending neuron’s terminal buttons taking back excess neurotransmitters from the synaptic gap 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 Synaptic Transmission http://learn.genetics.utah.edu/ content/addiction/crossingdivi de/ Think Pair Share 1. Put the following terms in order as they occur. 2. Identify which are part of the “electro” (E) part and which are part of the “chemical part” (C) 3. Briefly describe the electro-chemical process of neural transmission: – Resting potential – Synapse – Action potential – Repolarization – Refractory period – All-or-None – Threshold – Excitation – Inhibition – Reuptake – Depolarization 1. 2. 3. 4. 5. A brief electrical charge that travels down the axon of a neuron is called the Synapse Agonist Action Potential Resting Potential Refractory period Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. The function of dendrites is to 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. 0% 1. Table 0% 0% 2. 3. 0% 0% 4. 5. The movement of positively charged ions across the membrane of a neuron can produce a(n) 1. 2. 3. 4. 5. Action potential Synapse Neurotransmitter Myelin sheath Interneuron Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. 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 5. Refractory period 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. Table The minimum level of stimulation required to trigger a neural impulse is called the 1. 2. 3. 4. 5. Reflex Threshold Synapse Action potential All-or-none response Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. 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. 0% 1. Table 0% 0% 2. 3. 0% 0% 4. 5. Drugs can be….. • Agonists- mimic neurotransmitters • Antagonists- block neurotransmitter • Reuptake Inhibitors- block the reuptake Acetylcholine (ACH) • Motor movement, memory and learning. • Too much and you will…. • Too little and you will… • Alzheimer’s disease – lack of AcH • Black widow – increased AcH • Botox – blocks AcH • Curare – blocks AcH Dopamine • Motor movement and alertness/attention, emotion, rewards. • Parkinson’s Disease (too little) • Schizophrenia (Too much) Serotonin • Emotional State/Mood, Sleep, • Depression - Lack of serotonin • Anxiety • OCD Endorphins • Pain control/perception, mood booster – Examples: – Allows you to continue playing in the game when you sprain your ankle – “endorphins make you happy…happy people don’t kill their husbands” – runners high Norepenephrine • Fight or flight response – increased heart rate, breathing, pupil dilation, • High Blood Pressure • Anxiety GABA • Inhibition of Brain Activity – Major inhibitory neurotransmitter - keeps the neuron from firing (slows CNS) • Undersupply linked to seizures, tremors, insomnia • Alcohol consumption causes an increase in GABA Glutamate • Excitation of Brain Activity – Major excitatory neurotransmitter Meaning… It causes neurons to fire – overactive CNS • Migrains • MSG Antidepressants such as Prozac target which neurotransmitter? 1. 2. 3. 4. 5. A. serotonin. B. glutamate. C. GABA. D. acetylcholine. Dopamine 0% 1. 0% 0% 2. 3. 0% 0% 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 1. 2. 3. 4. 5. Glutamate Dopamine Acetylcholine Endorphins Insulin Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. 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 Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. Neurotransmitters that bring a neuron closer to firing are called 1. 2. 3. 4. 5. Agonist Antagonists Inhibitory Reuptake Excitatory Table 0% 1. 0% 0% 2. 3. 0% 0% 4. 5. 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 i.e. Heroin, Morphine (Mimic Endorphins) Black Widow Spider Venom (mimics AcH) Antagonists – Botulin (AcH), Curare (AcH) (block neurotransmitters) 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. • What are two examples of you using your Somatic Nervous System Autonomic Nervous System • Controls the automatic functions of the body. – Lungs, stomach, intestines, liver, kidney, heart • sympathetic and the parasympathetic • What are two examples of you using your Autonomic Nervous System Sympathetic Nervous System • Fight or Flight Response. – Arouses and expends energy • Causes: – Increase in heart rate, breathing, dilates pupils, slows down digestion, relaxes bladder • What are two examples of you using your Sympathetic Nervous System 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. • What are two examples of you using your Parasympathetic Nervous system The peripheral nervous system consists of: 1. 2. 3. 4. A. B. C. D. association areas. the spina chord. the reticular formation. sensory and motor neurons. Table 0% 1. 0% 2. 0% 3. 0% 4. 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? 1. A. sympathetic nervous system 2. B. somatic nervous system 3. C. parasympathetic nervous system 4. skeletal nervous system 0% 1. Table 0% 2. 0% 3. 0% 4. 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 Think Pair Share • Which part of your nervous system and which neurons would you rely on most heavily to cross the street? • Which part of your nervous system and which type of neuron’s would you use to when Ms. Short arrives at your class and calls you out to the hall, then sends you back to class. A Simplified Neural Network Neural Network – interconnected cluster of neurons in the CNS 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. •Similar too Neurotransmitters Neurotransmitters Hormones Neurotransmitters Location Nervous System Blood Stream/Endocrine System Speed Very fast – fraction of a second Travel from neuron to neuron Slow – several seconds Travel from gland to tissue Hormones Pineal Gland – controls circadian rhythm (melatonin) Master Gland:controls other glands Responsible for releasing (growth hormone Controls pituitary gland Sends info to CNS Thyroxine Overactive = skinny Underactive = fat Parathyroid hormone Adrenaline or epinephrine and norepinephrine cortisol Insulin Too Low = hyperglycemia Too high = hypoglycemia Estrogen Testosterone Figure 3A.11 The endocrine system © 2011 by Worth Publishers