Chapter 22: The Nervous and Endocrine Systems

1. Chapter 22:The Nervous and Endocrine Systems

2. 22.1 The Nervous System • Functions of the nervous system: • Body’s control system. • Processes and stores information. • Communicates information throughout the body. • Controls the body’s response to stimulus. • Allows for feelings, emotions, dreams…

3. Organization of the Nervous System: • Organs: • Brain • Spinal cord • Sensory organs • Eyes • Ears • Nose • Tongue • Skin

4. Neuron: nerve cell • Parts of a neuron: • Cell body • Dendrites: Short branches off the neuron. Takes in information from the environment or other cells. • Axon: Long branch. Transmits information to other cells

6. Myelin sheath: • “Pillows” that wrap around the axon, insulating it and making nerve signals travel faster.

7. Synapse: Gap between neurons.

8. Three classes of neurons: • Sensory neurons: Carry information from the body or environment to the brain and spinal cord. • Motor neurons: Carry information from the brain and spinal cord to the muscles and glands. • Interneurons: Relay information between sensory and motor neurons.

9. Sending signals • Nerve impulses travel in one direction only.

10. Path of a nerve impulse: 1) Stimulus triggers electrical impulse in dendrite of sensory organ.

11. 2) Electrical impulse travels through the cell body and down the axon, “leaping” between the gaps in the myelin.

12. 3) Electrical impulse causes end of axon to release neurotransmitters (chemical messengers) into the synapse.

13. 4) Neurotransmitters move across synapse.

14. 5) Neurotransmitters bind to dendrites of second neuron.

15. 6) Binding triggers an electrical impulse in the second neuron.

16. Two divisions of the nervous system: • Central nervous system (CNS): • The brain and spinal cord • Communication, memory, thought.

17. Peripheral nervous system (PNS): • Connects brain and spinal cord to the rest of the body. • Divided into: • Somatic nervous system • Voluntary actions • Autonomic nervous system • Involuntary actions

18. 22.2 Brain and Spinal Cord • Brain: Allows for reasoning, intelligence, analysis of situations, communication, creation, feeling, and learning.

19. The brain is divided into three major parts: • Cerebrum • Cerebellum • Brain stem

20. Cerebrum: • Largest part of the brain. • Memory storage. • Thinking. • Processes information from sensory organs. • Communication and learning.

23. Cerebellum • Coordination of voluntary actions. • Regulates skeletal muscle and maintains muscle tone. • Balance.

24. Cerebellum

25. Brain stem • Connects brain to spinal cord. • Three parts: • Midbrain • Pons • Medulla oblongata: Controls involuntary actions.

26. Brain stem

27. The skull and the cerebrospinal fluid help protect the brain from injury.

28. Spinal Cord • Connects brain to the rest of the body. • Contains bundles of neurons held together by connective tissue, plus blood vessels to supply nutrients and oxygen.

29. Cross section of spinal cord

30. Vertebrae • (singular: vertebra) • 33 irregularly-shaped bones that protect the spinal cord. • Fluid in the spine also helps protect the spinal cord.

33. Paralysis: • Damage to the spinal cord can cause paralysis, because the brain cannot communicate with the body beyond the damaged area.

34. Reflexes: • Automatic, involuntary response to a stimulus.

35. Reflex arc: • Stimulus triggers impulse in sensory neuron to interneuron in the spinal cord. • Interneuron sends impulse to motor neuron. • Motor neuron causes muscles to move. *Controlled in the spinal cord, not the brain.

36. 22.3 The Senses • Sensory receptors: Special cells in sensory organs that can detect light, mechanical, chemical, or thermal energy. • Sensory receptors change these energies into electrical impulses that are sent to the brain to be processed.

37. Sight: • Light energy is detected and turned into images. • Two kinds of photoreceptors: • Cones: Day vision. Sensitive to red, blue, and green light. • Rods: Night vision. Not sensitive to colors. • Retina: Thin layer of tissue on the back of the eye that contains rods and cones.

39. Rods and cones

40. Hearing: • Detection of sound waves (vibration). • Cilia: tiny hairs on receptor cells that change the vibrations into an electrical impulse. • Cochlea: Contains the receptor cells.

42. Balance: • Sensed in the ears. • Semicircular canals contain tiny hair cells, jelly-like fluid, and ear stones (otoliths). • Ear stones move around and bend hair cells when the body moves. • Hair cells send impulse to the brain. • Brain interprets the impulse, and if the body is losing balance, contracts or relaxes muscles to restore balance.

43. Smell: • Chemical enters the nose and binds with sensory receptors. • This triggers an electrical impulse, which the brain interprets as smell.

44. Taste: • Sensory receptors on the tongue (especially in the taste buds) detect different chemicals. • Sweet • Salty • Bitter • Sour • Umami (meaty, savory)

45. Touch: • Different receptors detect pressure, temperature, and pain. • Sensory receptors in the skin detect chemicals, heat, and mechanical energy.

46. 22.4 The Endocrine System • Messenger system. • Works with the nervous system to control the body. • Sends mass messages throughout the body.

47. Hormones: • Chemicals released into the bloodstream and generally regulate slow body processes: • Cell growth and development • Metabolism • Sexual function • Reproduction • Response to danger or stress

48. Gland • Organ the produces and releases a substance. • Endocrine glands: Release hormones into the bloodstream.

49. Gland is triggered. • Gland releases hormone. • Hormone attaches to receptor on target cell. • Cell carries out a specific task.

50. Major glands in the body: