Nervous System

1. Nervous System

2. Unit 5: Nervous System & Senses p. 35 senses nerves functions 3a. Interpret interactions among hormones, senses, and nerves which make possible the coordination of functions of the body. 3b. Investigate the physiology of electrochemical impulses and neural integration and trace the pathway of an impulse, relating biochemical changes involved in the conduction of the impulse. 3c. Describe how the body perceives internal and external stimuli and responds to maintain a stable internal environment, as it relates to biofeedback. electrochemical biochemical internal external internal (homeostasis)

3. I. Function of the Nervous System Control & coordination of body systems Three basic functions to accomplish this mission: Sensory input Integration Motor output

4. The three functions… visualized: Integration Evaluate the info Send response instruction(s) Motor output Sensory input Information IN

5. Comp Book: -p. 38 Flow Map: From Stimulus to Nervous Response

6. II. General Overview A. Structural Classification There are 2 major structural divisions of the nervous system: the central nervous system (CNS) the peripheral nervous system (PNS)

7. 1. Central Nervous System (CNS) – is made up of the brain & spinal cord a. Brain – contains about 100 billion neurons Click here for intro to the brain video

8. The brain can be divided into 4 major regions: i. Cerebrum ii. Diencephalon (midbrain) iii. Cerebellum iv. Brain stem

9. i. The cerebrum governs: • intelligence • memory • language • interpretation of sensory info. (smell, sight, hearing) taste,

10. motor functions (activity of muscles and glands)

11. ii. The diencephalon is found beneath / within the cerebrum • The diencephalon contains: • Thalamus: conducts information between the spinal cord & cerebrum

12. Hypothalamus (below the thalamus): center for homeostasis in the body (temperature, appetite, & water balance)

13. iii. Cerebellum: below the cerebrum & behind the brain stem Cerebellum

14. iii. Cerebellum governs: • smooth, coordinated movements • helps maintain posture, muscle tone, and equilibrium (balance) (you lose your equilibrium when you drink because the alcohol inhibits the function of the cerebellum)

15. iv. brain stem: connects brain to spinal cord—it regulates: • heartbeat • respiration • blood pressure

16. swallowing • coughing • hiccupping • sneezing • vomiting

17. Neurons passing through the brain stem cross from one side of the body to the other. (In other words, if your right hand was burned, the pain signals would travel to the left side of the cerebrum to be interpreted) (Also, if you wanted to lift your left arm, the signal would be sent to your left arm from the right side of your cerebrum)

18. b. Spinal cord – extends from the brain stem, through the vertebrae to the 2nd lumbar vertebra

19. Notice: the spinal cord does not extend to the tip of the vertebral column

20. information traveling to and from the brain must pass through the spinal cord to reach other parts of the body • often called the “information highway” of the CNS • made of 2 layers: “gray” & “white” matter

21. 2. Peripheral Nervous System (PNS) the cranial & spinal nerves Humans have: • 12 pairs of cranial nerves ex. optic nerves, olfactory nerves, facial nerves

24. 31 pairs of spinal nerves

26. One of the most important functions of the PNS is to perform reflex actions, which do not involve the brain A reflex is a sudden, rapid, involuntary response to a stimulus

27. Reflex examples: • knee jerk reflex (lower leg kicks when tendon is tapped)

28. withdrawal reflex (hand withdraws if it touches something hot)

29. papillary reflex (pupil constricts if a bright light is shown in your eyes)

30. How do reflexes work? Knee jerk reflex: the patellar tendon is tapped • this generates nerve impulses which travel along sensory neurons to the spinal cord

31. the spinal cord then transmits impulses through motor neurons • the rectus femoris muscle is instructed to contract, causing extension of the lower leg • the brain is not involved in the response

32. information travels over a shorter distance – producing faster reaction times • the reflex is completed before your brain is aware of what happened

33. you will typically withdraw your hand from something hot before you recognize the pain of the burn

34. Comp Book: -set it up -back of p. 35 structural classification

35. II. General Overview (continued) Remember the nerve pathway? Sensory integration  motor output Sometimes it is simpler to address each part of the nervous system based on the general role it plays in the nerve pathway… (brain) B. Functional Classification of PNS: categorizing parts of the nervous system based on the nervefunction in the overall nerve pathway; in this way, there are 2 types of nerves: • Sensory • Motor

36. 1. Sensory Nerves = Afferent Division: The body’s receptive nerves taking info from both the internal and external environment toward the CNS: a. Somatic sensory fibers—nerve endings & receptors in skin, skeletal muscles & joints b. visceral sensory fibers—nerve endings and receptors in abdominal & pelvic organs

37. Plus all your special senses… ch. 9 c. Vision from the eyes d. Hearing & balance from the ears e. Smelling from the nose (chemoreceptors) f. Taste from the tongue (chemoreceptors)

38. 2. Motor Nerves = Efferent Division After the brain integrates the sensory input, outgoing response is sent through the efferent nerves The motor or efferent portion of the PNS is typically divided into 2 subsystems: a. Somatic Nervous System b. Autonomic Nervous System

39. a. Somatic Nervous System – includes the cranial & spinal nerves that regulate voluntary actions

40. b. Autonomic Nervous System – includes the cranial & spinal nerves that regulate involuntary actions ex. cardiac muscle smooth muscle gland activity

41. Keep in mind that although the ANS functions “automatically”, you can consciously control it for a short period of time When you hold your breath, you are overriding your ANS – however, you cannot override it indefinitely

42. The Autonomic Nervous System can be further subdivided into: i. Sympathetic Division ii. Parasympathetic Division

43. i. Sympathetic Division: regulates involuntary actions during periods of high stress or increased activity • increases blood pressure • heart rate • breathing rate • blood flow to muscles

44. dilates the pupils of your eyes (increases amount of light; see better) • decreases digestion of food & blood flow to the skin All of these changes prepare your body for action (“fight or flight”)

45. ii. Parasympathetic Division: regulates involuntary actions during periods of rest or relaxation • decreases blood pressure • decreases heart & respiratory rates • decreases blood flow to muscles

46. ii. Parasympathetic Division (cont.’d): • constricts the pupils of your eyes • increases digestion of food and blood flow to the skin

47. *** Most internal organs are regulated by both the sympathetic and parasympathetic divisions.*** • the sympathetic division dominates when you are under stress • the parasympathetic division dominates when you are relaxed

48. Comp Book: -p. 36 functional classification -back of p. 37 Venn: Autonomic vs. Somatic

49. III. The Electrochemical Impulse A. Anatomy of a neuron Click here for intro to nerve cells video

50. Neuron structure – 3 basic parts 1. One or more dendrites • Short, highly branched extensions • Receive impulses from receptors or other neurons • transmit impulses toward the cell body