6.5 Nerves, Hormones And Homeostasis PPT


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6.5 Nerves, Hormones And Homeostasis PPT

  1. 1. Topic 6.5Nerves, Hormones and Homeostasis<br />IB Biology<br />
  2. 2. Nervous System<br />Central Nervous System (CNS):<br />brain and spinal cord<br />relays messages, processes and analyzes information<br />Peripheral Nervous System (PNS)<br />peripheral nerves: cranial and spinal (outside CNS)<br />connects sense organs to CNS<br />connects CNS to muscles and glands<br />
  3. 3. Peripheral Nervous System<br />Sensory division (from receptors to CNS)<br />Motor division (from CNS to effectors)<br />Somatic: voluntary<br />Autonomic: involuntary<br />Sympathetic: “fight or flight”<br />Dilates pupil/relaxes lens<br />Inhibits digestion<br />Increases heart rate<br />Dilates bronchioles<br />Stimulate liver: glycogen -> glucose<br />Relaxes bladder<br />Parasympathetic: opposite - conserves energy (“rest and digest”)<br />
  4. 4. Neurons<br />Specialized cells that carry electrical impulses<br />node of Ranvier<br />Motor Neuron<br />
  5. 5. Neurons under a microscope<br />
  6. 6. Nerve bundle<br /><ul><li>Myelin sheath is made of Schwann cells wrapped around the axon
  7. 7. Myelin: insulating material
  8. 8. Demyelination = myelin is destroyed </li></ul>e.g. multiple sclerosis<br />
  9. 9. Spinal cord<br />
  10. 10. Types of Neurons<br />Sensory Neuron<br />Sensory Neurons: transmit electrical impulses from sensory receptors to the CNS<br />Relay Neurons (Interneurons): move impulses inside the CNS<br />Motor Neurons: take impulses from CNS to effectors (glands/muscles)<br />Motor Neuron<br />
  11. 11. Reflex <br />
  12. 12. How the impulse is transmitted<br />Impulse begins when a neuron is stimulated by another neuron or by the environment<br />Electrical impulse moves in one direction:<br />Dendrites -> Cell Body -> Axon<br />Synapse: gap between 2 neurons <br />Neurotransmitters send the signal to the following neuron<br />No myelin = 5-25m/s<br />With myelin = 10-120m/s<br />
  13. 13. How the impulse is transmitted<br />Neuron not transmitting an impulse: membrane has an electrical potential (voltage) called resting potential<br />Caused by the imbalance of K + and Na + across the membrane (Na + /K + pumps) = polarization<br />Electric difference (voltage): -70mV<br />
  14. 14. When there is a stimulus...<br />Na+ gates open = Na + enter the cell<br />Electrical potential of the cell changes<br />depolarization (normal charge is reversed) = +30mV<br />Action potential is recorded<br />Na + channels close<br />K + channels open<br />repolarization occurs (charges back to normal)<br />K + channels stay open longer<br />hyperpolarization = -85mV (refractory period = prevents one impulse to catch up with another)<br />Stimulus = self-propagating<br />http://outreach.mcb.harvard.edu/animations/actionpotential.swf<br />
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  17. 17. The Synapse<br />Synapse = gap between neurons<br />Action potential cannot cross gap: neurotransmitters carry the impulse<br />Neurotransmitters: stored at the end on axons (glutamate, GABA, acetylcholine, norepinephrine, dopamine, serotonin, nitric oxide, etc)<br />Voltage Ca+2 gated ions open -> calcium flows inside neuron<br />Calcium help vesicles fuse with membrane -> neurotransmitters are released<br />These bind with neuroreceptors <br />Voltage gated ions are activated = depolarization<br />Impulse is passed on to post-synaptic neuron<br />Neurotransmitters = broken by enzymes and reabsorbed by pre-synaptic neuron<br />
  18. 18.
  19. 19. Endocrine System<br />Endocrine glands produce hormones that travel in the blood<br />Target tissue responds<br />Response affects the gland = NEGATIVE FEEDBACK<br />Body maintains its internal conditions stable = HOMEOSTASIS<br /><ul><li>Blood pH, Temperature, Water balance, Glucose concentration, CO2 concentration</li></li></ul><li>Negative Feedback<br />
  20. 20. Negative Feedback 2<br />
  21. 21.
  22. 22. Control of Body Temperature<br />Hypothalamus controls body temperature, preventing cooling/overheating<br />Skin arterioles: vasoconstriction (prevents heat loss) ; vasodilation (more blood near surface – heat is transferred out)<br />Shivering<br />Hairs with erector muscle <br />Sweat glands<br />
  23. 23. Control of Blood Glucose<br />Pancreas is an endocrine gland<br />It releases insulin ( cells) and glucagon ( cells)<br />Receptors present on liver cells<br />Negative feedback occurs<br />
  24. 24. Diabetes mellitus<br />Glucose builds up in blood = cells lose water (a lot of urine is produced)<br />Glucose appears in urine <br />Type I: juvenile<br /> - no insulin is produced because  cells are destroyed (autoimmune)<br />Type II: adult<br /> - reduced sensitivity to insulin / less receptors <br />