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6 - Coordination & regulation


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6 - Coordination & regulation

  1. 1. Coordination & Regulation Nervous Systems
  2. 2. Case study : Optic nerve <ul><li>The optic nerve connects the eye to the brain. </li></ul><ul><li>Damage to this nerve will result in blindness </li></ul><ul><li>One disease that causes this is glaucoma </li></ul><ul><ul><li>In the chamber between the cornea and iris, a clear fluid is formed and drained </li></ul></ul><ul><ul><li>If draining is inhibited, this can cause the intraocular pressure (IOP) to build up </li></ul></ul><ul><ul><li>Symptoms: nothing -> eye pain -> lose sight from corners of eye -> tunnel vision -> blindness </li></ul></ul><ul><ul><li>Early diagnosis can slow / prevent onset of disease </li></ul></ul>
  3. 3. The Human Eye
  4. 4. The Nervous System <ul><li>Central Nervous System (CNS) </li></ul><ul><ul><li>Brain </li></ul></ul><ul><ul><li>Spinal Chord </li></ul></ul><ul><li>Peripheral Nervous System </li></ul><ul><ul><li>Sensory (afferent): Information to the CNS </li></ul></ul><ul><ul><ul><li>Somatic sensory neurons (from external env.) </li></ul></ul></ul><ul><ul><ul><li>Visceral sensory neurons (from internal env.) </li></ul></ul></ul><ul><ul><li>Motor (efferent): Information from the CNS </li></ul></ul><ul><ul><ul><li>Somatic system (mainly voluntary actions) </li></ul></ul></ul><ul><ul><ul><li>Autonomic system (mainly involuntary actions) </li></ul></ul></ul><ul><ul><ul><ul><li>Sympathetic (senses aroused – eg. fight or flight) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Parasympathetic (relaxed state) </li></ul></ul></ul></ul>
  5. 5. <ul><li>xcvb </li></ul>
  6. 6. Nerve Cells Cell Body Axon Myelin sheath Synaptic Terminals Dendrites Note the direction of nerve impulse
  7. 7. Different Types of Neurons <ul><li>Affector (sensory) neurons: body to CNS </li></ul><ul><li>Effector (motor) neurons: CNS to body </li></ul><ul><li>Connecting neurons (affector to effector in CNS) </li></ul>
  8. 8. Nerve Impulses <ul><li>In a relaxed state, the external environment of a neuron is more positive than the interior </li></ul><ul><li>Stimulated receptors will cause sodium ions to be imported, enough will start an action potential </li></ul><ul><li>The impulse moves down the cell as sodium ions are imported, resting potential is restored as potassium ions are exported. </li></ul>
  9. 9. Myelin Sheath <ul><li>Our neurons start myelinating from birth </li></ul><ul><li>Myelination is usually complete by age 30 </li></ul><ul><li>Works as a kind of insulation around our neurons </li></ul><ul><li>An impulse will move down the axon of an unmyelinated neuron at 0.5 m/s </li></ul><ul><li>An impulse will move down the axon of a myelinated neuron at 200 m/s </li></ul>
  10. 10. Communication Via Neurotransmitters <ul><li>Once an action potential (nerve impulse) reaches the axon terminal of the neuron it triggers the intake of calcium ions </li></ul><ul><li>This results in the exocytosis of a vessicle bound neurotransmitter (usually acetylcholine) </li></ul><ul><li>As the neurotransmitter binds to the receptor mediated proteins on the corresponding neuron, sodium ions are imported and the action potential continues </li></ul>
  11. 11. Neurotransmitter animation
  12. 12. More on Neurotransmitters <ul><li>Vessicles containing neurotransmitters are only located at the synaptic end of the axon </li></ul><ul><li>The gap between the synaptic terminal of one neuron and the dendrite of another is called the “synaptic cleft” </li></ul><ul><li>The gap between the synaptic terminal of one neuron and a muscle is called the “nerve-muscle junction” </li></ul><ul><li>The action triggered by a nerve is short lasting as the recipient muscle or gland releases enzymes to inactivate the neurotransmitter substances </li></ul>
  13. 13. Neurohormones <ul><li>Neurohormones involve cooperation between the nervous and endocrine system to maintain homeostasis </li></ul><ul><li>Neurohormones are carried on the blood </li></ul><ul><li>Eg. the hypothalamus releases a particular neurohormone to trigger the pituitary gland to release a corresponding hormone: </li></ul>
  14. 15. Nerve networks – converging or diverging <ul><li>There can be hundreds of axon terminals synapsing with a neuron </li></ul><ul><li>A neuron can synapse with any number of other neurons </li></ul><ul><li>Hence, there are no discrete linear pathways, bat rather a network of activated or inhibited neurons contributing to the ultimate action </li></ul><ul><li>NOTE: The outcome is not just determined by the number of activation / inhibition messages but is also dependent on their relative strength </li></ul>
  15. 16. Nerve networks – converging or diverging
  16. 17. Diverging network
  17. 18. Converging network
  18. 19. Depending on signal, networks can operate in one way or the other
  19. 20. Impediment of Neuron Function <ul><li>Can be caused by drugs or disease and have many consequences: </li></ul><ul><ul><li>eg. non-functioning thyroid can result in weight loss, increased appetite, heart tremors, muscle wasting. </li></ul></ul><ul><li>Can be caused by toxins contained in venom </li></ul><ul><ul><li>Cytotoxic – causes cell death (necrosis) </li></ul></ul><ul><ul><li>Haemotoxic – effects blood cloting and ability to carry oxygen </li></ul></ul><ul><ul><li>Neurotoxic – details on following slide </li></ul></ul>
  20. 21. Neurotoxic Venom <ul><li>Venom is simply modified saliva containing toxins </li></ul><ul><li>Found in many Australian spiders & snakes </li></ul><ul><ul><li>eg. Red Back, Funnel Web </li></ul></ul><ul><ul><li>eg. Inland Taipan, King Brown, Death Adder </li></ul></ul><ul><li>Some bacteria produce neurotoxins </li></ul>
  21. 22. Some of the best ways to die on your next Australian holiday! <ul><li>Porcupine fish and Funnel Web spider </li></ul><ul><ul><li>Small toxin, fast acting, fast dispersal </li></ul></ul><ul><ul><li>Interferes with movement of Na + ions, thereby preventing particular nerve impulses </li></ul></ul>
  22. 23. Some of the best ways to die on your next Australian holiday! <ul><li>Red Back spider </li></ul><ul><ul><li>Larger toxin </li></ul></ul><ul><ul><li>Causes neurotransmitters to trickle out of neuron </li></ul></ul><ul><ul><li>Message does not reach muscle = paralysis </li></ul></ul><ul><li>Parasitic tick </li></ul><ul><ul><li>Larger toxin </li></ul></ul><ul><ul><li>Inhibits release on neurotransmitters </li></ul></ul><ul><ul><li>Message does not reach muscle = paralysis </li></ul></ul>
  23. 24. Some of the best ways to die on your next Australian holiday! <ul><li>Snakes </li></ul><ul><ul><li>Neurotoxins effect the permeability of the pre & post synaptic membrane </li></ul></ul><ul><ul><li>May results in muscle damage </li></ul></ul><ul><ul><li>May result in kidney failure due to large amounts of protein in bloodstream </li></ul></ul><ul><ul><li>The good news is that many antivenoms & antitoxins have been developed that act as antibodies, in that they will bind and interfere with toxin. </li></ul></ul>
  24. 25. Central Nervous System <ul><li>Protection </li></ul><ul><ul><li>Bone (skull / vertebrae) </li></ul></ul><ul><ul><li>Meninges (membrane) </li></ul></ul><ul><ul><li>Fluid (between membrane & tissue) – cushioning </li></ul></ul><ul><ul><ul><li>NB – If a problem is suspected, diagnosis is often possible through analysis of cerebrospinal fluid </li></ul></ul></ul>
  25. 26. The Brain
  26. 27. The Brain <ul><li>Cerebrum - Largest part of the brain is the </li></ul><ul><ul><li>The 2 hemispheres are joined by many axons </li></ul></ul><ul><ul><li>Folded surface is called the cerebral cortex </li></ul></ul><ul><li>Thalamus - receives impulses from sensory organs and directs these for processing </li></ul><ul><li>Hypothalamus – responsible for hormone production and many aspects of homeostasis </li></ul><ul><li>Brain Stem (midbrain, pons and medulla oblongata) – essential for survival as it controlls breathing and heart rate. </li></ul>
  27. 28. Mapping the Brain <ul><li>Most easily done by observing the effect on the person after they have damaged a certain part of their brain. </li></ul><ul><li>More complex functions require more neurons, therefore a larger part of the brain is dedicated to this task </li></ul>Neck Hands and fingers
  28. 29. Mapping the Brain <ul><li>Neural energy is electrical and can be measured via an EEG (electroencephalogram) </li></ul><ul><li>There is an EEG range considered as normal </li></ul><ul><ul><li>Values outside the normal range may indicate brain damage </li></ul></ul><ul><ul><li>Flat EEG indicates that brain / person is dead </li></ul></ul>
  29. 30. <ul><li>Sensory detectors from body go via spinal chord to brain </li></ul><ul><li>Grey matter (cell bodies) </li></ul><ul><li>White matter (axons) </li></ul><ul><li>Surrounded by bone (vertebral column) </li></ul><ul><li>Cartilaginous discs between vertebrae provide shock absorption and flexibility </li></ul>The Spinal Chord
  30. 31. Brain Scanning <ul><li>PET (positron emission tomography) detects amount of glucose being used by cells </li></ul><ul><ul><li>Damaged sections need glucose for repair </li></ul></ul><ul><ul><li>Tumours have very high glucose requirements </li></ul></ul><ul><li>CAT (computerised axial tomography) emits very density sensitive x-rays from multiple positions </li></ul><ul><ul><li>Images appear as “slices” of the brain </li></ul></ul><ul><ul><li>Tumour cells are much denser than normal cells </li></ul></ul>
  31. 32. Comparison between nerves and hormones <ul><li>Hormones </li></ul><ul><ul><li>Slower acting </li></ul></ul><ul><ul><li>Longer lasting </li></ul></ul><ul><li>Nerves </li></ul><ul><ul><li>Faster acting </li></ul></ul><ul><ul><li>Faster dissipating </li></ul></ul><ul><li>Both </li></ul><ul><ul><li>Rely on chemical messengers </li></ul></ul><ul><ul><ul><li>Hormones (in bloodstream) </li></ul></ul></ul><ul><ul><ul><li>Nerves (over synaptic cleft) </li></ul></ul></ul>
  32. 33. Comparison between nerves and hormones (continued) <ul><li>Nerves - inactivation of neurotransmitters almost instantaneous </li></ul><ul><li>Hormones </li></ul><ul><ul><li>Adrenaline can dissipate in minutes </li></ul></ul><ul><ul><li>Insulin can persist in bloodstream for hours </li></ul></ul><ul><ul><li>Thyroxin can remain active for up to a week </li></ul></ul>
  33. 34. What is the control mechanism? <ul><li>Melanin is a cell pigment that if spread evenly causes the cell to be dark in colour. If melanin clumps toward the centre, the cell will appear light in colour. </li></ul><ul><li>Arctic hares are brown in summer and white in winter </li></ul><ul><li>HORMONAL </li></ul><ul><li>Chamelions can change colour in seconds </li></ul><ul><li>NERVOUS </li></ul>
  34. 35. Neurons and Homeostasis <ul><li>1 neuron = 1 type of neurotransmitter = 1 action </li></ul><ul><li>Activation or inhibition determined by individual neurons. </li></ul><ul><li>Neurons maintain homeostasis through their actions on glands or muscles </li></ul>Nothing Activate
  35. 36. Homeostasis – Nerves & Hormones Acting Together <ul><li>Just like hormones, homeostatic systems relying on the nervous system also uses negative feedback loops </li></ul><ul><li>Blood glucose is not all hormonally controlled. </li></ul><ul><li>Sensory nerves in the intestines will stimulate insulin production due to the amount of glucose entering the system as a result of digestion </li></ul>
  36. 37. Control of Blood Pressure
  37. 38. Maintaining Core Temperature
  38. 39. Maintaining Water Balance <ul><li>Osmoreceptors in hypothalamus detect high solute concentration in blood </li></ul><ul><ul><li>This triggers the posterior pituitary gland to produce vasopressin </li></ul></ul><ul><ul><li>Vasopressin increases permeability of distal tubules & collecting ducts in nephrons </li></ul></ul><ul><ul><li>Therefore more water is reabsorbed </li></ul></ul><ul><li>Osmoreceptors also trigger nerves that generate a sensation of thirst </li></ul><ul><ul><li>More water is consumed </li></ul></ul><ul><li>Pressure-sensitive detectors in kidneys detect drop in blood pressure </li></ul><ul><ul><li>Renin is released in the kidneys </li></ul></ul><ul><ul><li>This triggers the release of aldosterone which encourages greater reabsorption of Na + from filtrate </li></ul></ul><ul><ul><li>Water follows the passage of Na + via osmosis </li></ul></ul>
  39. 41. Neuron Neurotransmitter Neuron Neurohormone
  40. 42. Homework!!! <ul><li>Chapter review questions: 2-7 & 9 </li></ul><ul><li>Biozones: </li></ul>