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Resourcd File

  1. 1. The structure and function of the brain Neurons
  2. 2. Neuron Key words: Dendrites Cellular body Axon Myelin Sheath Nodes of Ranvier Glial cells
  3. 3. A dendrite is an extension from the neuron that receives messages from other neurons. Named after the Greek word meaning “tree,” these branch-like projections relay messages to the cell body before they’re passed down the axons and on to the other neurons.
  4. 4. Axon An axon is a neuron’s long, tube-like “arm;” it sends information on to the next neuron. Messages travel from the cell body along the axon as electrical signals, but are passed to the target cell, across a gap, as chemicals called neurotransmitters. Like wires, axons are long and thin. These fibers can reach up to three or more feet in length.
  5. 5. Myelin Sheath The myelin sheath is an insulating fatty layer that surrounds many axons. It helps speed the transmission of electrical signals down the axon, allowing much faster communication. Myelin sheaths are especially important in the axons of the peripheral nerves. These nerves can be up to several feet in length as they extend down to our fingers and toes!
  6. 6. Glial cells Special types of connective tissue cells that help support and protect neurons.
  7. 7. What do the different neurons do?  Motor neurons - carry messages AWAY from the brain  Sensory neurons – carry messages TO the brain from the PNS  Interconnecting neurons – receive messages from the sensory neurons and pass these messages to other neurons
  8. 8. Neurons and how they work  How neurons work  Neurotransmitters  Synaptic transmission  Action Potential
  9. 9. Neurotransmitters  Dopamine v=at3Sg6qvgTE&feature=related
  10. 10. Serotonin Serotonin was first recognised as a powerful vasoconstrictor in blood serum. It was isolated in 1948 by Page and was later found to be associated with the central nervous system. The chemical name for serotonin is 5-hydoxytryptamine which is often abbreviated to 5-HT. Serotonin is naturally produced in the Pineal gland which lies deep at the centre of the human brain. The average adult human possesses only 5 to 10 mg of serotonin, 90 % of which is in the intestine and the rest in blood platelets and the brain. One role of this 'wonder drug' is as a neurotransmitter, allowing numerous functions in the human body including the control of appetite, sleep, memory and learning, temperature regulation, mood, behaviour, cardiovascular function, muscle contraction, endocrine regulation and depression. Subsequent to his discovery of Serotonin, Page commented that no physiological substance known possesses such diverse actions in the body as does serotonin. 5-HT is also found in wasp stings and scorpion venom where its function is of an irritant, since intravenous injection of serotonin in humans leads to pain, gasping, coughing, a tingling and prickling sensation, nausea, cramps and other unpleasant symptoms.
  11. 11. Acetylcholine Acetylcholine is a neurotransmitter found in both the central nervous system and the peripheral nervous system. Acetylcholine plays an important role both in learning and memory and in sending messages from motor nerves to muscles, especially in the heart, bladder and stomach. It also affects glands. There is a marked deficiency of acetylcholine in the brains of patients with Alzheimer's Disease. Drugs with anticholinergic effects target acetylcholine receptors.