Life Science Chapter 21 The Nervous System


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Life Science Chapter 21 The Nervous System

  1. 1. The Nervous System
  2. 2. Neuron – working unit of the nervous system
  3. 3. Axon – carries messages away from the cell body
  4. 4. dendrites – receive the messages and send them to the cell body
  5. 5. Terminal Bud – send messages to other neurons
  6. 6. 3 types of neurons• Sensory neurons – send info to the spinal cord or brain• Interneurons – send info out of brain and spinal cords to the motor neurons• Motor neurons – send info from brain and spinal cord to muscles or glands
  7. 7. Sensory neuron Motor neuron(hand) (arm) Interneuron
  8. 8. Synapse• Small space in between neurons• Neurotransmitters are released in the synapse and starts an impulse in the next neuron
  9. 9. Synapse
  10. 10. Divisions of the Nervous SystemCNS – central nervous system – brain and spinal cordPNS – peripheral nervous system – all the nerves outside the CNS
  11. 11. Central Nervous System• Brain 100 billion neurons• 3 major parts
  12. 12. 1. Cerebrum• Divided into hemispheres• Memory is stored
  13. 13. Cerebrum
  14. 14. 2. Cerebellum• Under the cerebrum• Coordinated voluntary muscle movements
  15. 15. 3. Brainstem• Connects the brain to the spinal cord• Made up of the – Mid brain – Pons – Medulla• Controls homeostasis of heart, breathing, blood pressure, involuntary muscle movements
  16. 16. Peripheral Nervous System• 2 divisions of the peripheral nervous system
  17. 17. Peripheral Nervous System Somatic AutonomicNervous System Nervous SystemSkeletal Heartrate,Muscle breathing, digestion, salivary glands
  18. 18. Reflex• Involuntary response to a stimulus• Involves a pathway called a (reflex arc) over which impulses travel
  19. 19. Reflex arc1. Impulse is sent to the spinal cord2. Impulse passes to an interneuron in the spinal cord which immediately relays the impulse to motor neurons3. Motor neurons transmit the impulse to muscles in your arm4. Your arm pulls back (Without thinking!)
  20. 20. Steps of a reflex arc1. Receptor2. Sensory neuron3. Interneuron (spinal cord)4. Motor neuron5. Effector – “response”
  21. 21. Your Endocrine System
  22. 22. Endocrine system• System of glands that release their products into the blood stream and broadcast messages throughout the body
  23. 23. Hormones• Affect specific tissues called target cellsTarget cells – control activities in parts of the body other than right around the gland
  24. 24. Glands of the Endocrine System
  25. 25. Hypothalamus• Part of the brain• Produces hormones that influence the pituitary gland
  26. 26. Pituitary Gland• “Master Gland”• Secretes numerous hormones• Growth-stimulating Hormone• Hormones to control specific glands• Thyroid Stimulating Hormone (TSH) – Tells thyroid to produce thyroxine• The Follicle Stimulating Hormone – Stimulates activity in the ovary and testes
  27. 27. Thyroid Gland• Located in the neck• Makes thyroxine• Regulates metabolism
  28. 28. Parathyroid Glands• Embedded in the thyroid gland• Secrete parathormone• Controls the metabolism of calcium• Necessary for nerve function, blood clotting, and proper growth of teeth and bones
  29. 29. Adrenal Glands• Two glands located on top of the kidneys• Each gland has 2 distinct regions
  30. 30. Adrenal Cortex• Secretes two types of steroid hormones1. promotes the conversion of body fat and protein into glucose2. promotes the reabsorbtion into the blood stream of sodium and chloride ions by the kidney tubules – This affects the water balance and maintains BP
  31. 31. Adrenal Medulla• Secretes adrenalin in times of emergency• Increases the blood sugar level• Speeds heart and breathing rates
  32. 32. Islets of Langerhans• Located in the pancreas• Secrete insulin and glucagon
  33. 33. Insulin• Helps take glucose into cells• Lowers blood sugar levels by taking it out of the blood and storing it in the liver and muscle cells
  34. 34. Glucagon• Stimulates the release of sugar from the liver• Raises blood sugar level
  35. 35. Gonads• Sex glands• Testes• Secrete testosterone – develop male secondary sex characteristics• Ovaries• Secrete estrogen - develop female secondary sex characteristics
  36. 36. Endocrine Control• Negative feedback system• Controls the amount of hormone an endocrine gland produces• Works like a thermostat in your house
  37. 37. Negative feedback systemStart: 1. Hormone level low 2. Hormone production increases 3. Hormone level high 4. Hormone production slowed downEnd: 5. Hormone level low
  38. 38. Endocrine Feedback System of TSH Hypothalamus In hibits Thyroxin Pituitary Gland Thyroid Gland Thyroid stimulates Stimulating Hormone
  39. 39. Endocrine System Disorders
  40. 40. Goiter• Enlargement of the thyroid gland• Results in not being able to make thyroxine• Often associated with iodine deficiency in the diet
  41. 41. Diabetes• Insulin deficiency• Results in an elevated blood sugar level• Also an inability of the body to store the sugar glycogen in the liver