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Neurons I bet your neurons are all fired up now! The Nervous System NEURON = 1 cell 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 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 cross 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 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 don 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 - Return to Resting Potential • Sodium/Potassium pumps push Sodium (Na+) out and Potassium in (Ka+) bringing axon back to a resting state Step 5 - Refactory period – Brief period of time when neuron won’t fire no matter how much stimulation Action Potential Electrical Transmission – The Action Potential http://outreach.m cb.harvard.edu/ animations/actio npotential.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 inhibitory - – (excitatory) – (inhibitory) reach minimum threshold - 3. All or None Law – How do neurons communicate with each other? The chemical process How Neurons Communicate Synaptic Transmission http://learn.genetics.utah.e du/content/addiction/rewar d/neurontalk.html Neurotransmitters Neurotransmitters – Excitatory neurotransmitters Inhibitory neurotransmitters 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 ______________________ • Black widow – • Botox – • Curare – Dopamine • Deals with motor movement and alertness/attention, emotion, rewards. • Lack of dopamine – linked to _______________ • Too much - linked to _______________ • Too little – _______________ Serotonin • Involved in mood control, hunger, sleep and arousal. • Lack of serotonin has been linked to _________________ • Anorexia = _______ • Bulimia = ________ Norepenephrine • • Helps control • Undersupply can depress mood GABA • Major • Hunger and Sleep • Undersupply linked to ______________ • _______________ causes an increase in Gaba Endorphins • Involved in pain control. • “endorphins make you happy” – runners high (emotions) • Drugs that mimic - Glutamate • Major __________ meaning _________ • Involved in memory and learning • Oversupply can over stimulate brain, producing migraines or seizures • Drugs can be….. • Agonists• Antagonists• Reuptake Inhibitors- 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) Prozac (serotonin) Antagonists – Botulin (AcH), Botox (AcH), Curare (AcH) The Nervous System Central Nervous System • The Brain and spinal cord • CNS Peripheral Nervous System • All nerves that are not encased in bone. • Everything but the brain and spinal cord. • Divided into two categories….somatic and autonomic. Somatic Nervous System • Controls • Uses Autonomic Nervous System • Controls • Divided into two categories Sympathetic Nervous System • Fight or Flight Response. Parasympathetic Nervous System • Automatically Reflexes • Reflex - a simple, automatic, inborn response to a sensory stimulus – ______________take info up through spine to the brain. – Some reactions occur when – Survival adaptation. A Simple Reflex A Simplified Neural Network Neurons that learn to work together as a team. The Endocrine System A system of Similar to ___________________________ Work Hormones Neurotransmitters The Major Endocrine Glands