1. UNIT 7 Part 2: The Nervous System

2. Key Questions  1. How do humans coordinate all body systems?  2. What parts make up the nervous system?  3. What role do chemicals and receptors play in the nervous system?  4. How do organisms maintain dynamic equilibrium in response to stimuli (internal/external)?  5. How do feedback mechanisms allow organisms to maintain homeostasis?  6. What happens if there are disruptions in homeostasis regarding the nervous system? 

3. REMEMBER!!!!  REGULATION :  Control and coordination of all life functions to maintain homeostasis.

4. REMEMBER!!!  Human body systems that involve regulation:  Nervous system and Endocrine system

5. NERVOUS SYSTEM  A. Definitions:  Impulse: Electro-chemical signal carried along a nerve pathway.  Receptor: Specialized structures that detect a stimulus.

6. RECEPTORS Tons of sensory neurons found here!!!

7. NERVOUS SYSTEM  Effector: Structure that carries out a response (muscles, glands).  Stimulus: Anything that causes a response.  Response: Reaction to a stimulus.

8. STIMULUS/RESPONSE

10. NERVOUS SYSTEM  Neurotransmitter: Chemical secreted to help to transmit impulses from neuron to neuron.  Reflex: A quick, automatic response to a stimulus. Examples: sneezing, blinking.

11. REFLEX Normal reflex for an infant when he or she is startled or feels like they are falling. The infant will have a "startled" look and the arms will fling out sideways with the palms up and the thumbs flexed.

12. Videos  Video – ‘Neuron’ – on server (part at beginning)

13. NOTES-NERVOUS SYSTEM  A. Structures of the Nervous System:  Neurons: Basic unit of function of the nervous system (See Diagram).

15. NERVOUS SYSTEM  Transmit impulses in one direction.

16. NERVOUS SYSTEM  PARTS OF THE NEURON: DCATS  Dendrites: Connect stimuli to neuron and generate impulses toward cell body.  Cell Body: Contains nucleus.

17. NERVOUSE SYSTEM  Axon:  Fibers wrapped in myelin sheath (fat coating)  Transmits impulses away from cell body and toward terminal branches.

18. NERVOUS SYSTEM  Terminal branches: End of neuron. Secretes neurotransmitters.  Dendrite on next nerve catches the neurotransmitter and initiates signal again.

20. NERVOUS SYSTEM  Synapse: Space between adjacent neurons.

21. Neuron Diagram

22. What is the ‘funny bone?!’  http://kidshealth.org/kid/talk/qa/funny_bone.ht ml http://kidshealth.org/kid/talk/qa/funny_bone.ht ml

23. Video  Video – ‘Nerve Impulses’ (server)  Video – ‘Neurotransmitters’ (server)

24. NERVOUS SYSTEM  FYI:  You are born with all of the nerve cells you will ever have. They cannot divide, so they cannot be replaced.  Many drugs affect the nervous system. Example: Many pain killers block neurotransmitters from being secreted, therefore the impulse is blocked, and you do not feel pain.

25. NERVOUS SYSTEM  3 Types of Neurons:  1. Sensory Neuron –  Transmits impulses from receptors to brain and spinal cord.  Sense organs = structures where sensory neurons are concentrated (eyes, ears, skin, tongue).

26. SENSORY NEURON

27. NERVOUS SYSTEM  FYI: The Senses:  The body has millions of neurons that respond to stimuli in the environment.  Sensory receptors react to specific stimuli by sending impulses to other neurons and then to the CNS.  These receptors are concentrated in sense organs, such as eyes, ears, nose, mouth, and skin.

28. NERVOUS SYSTEM  2. Interneurons –  Relay messages from sensory neurons to motor neurons.  Found in brain and spinal cord.

29. NERVOUS SYSTEM  3. Motor Neuron –  Transmit impulses from central nervous system (brain and spinal cord) to effectors (muscles, glands).

30. NERVOUS SYSTEM  Define Reflex Arc : Pathway over which nervous impulses travel.  Step 1 : A receptor receives a stimulus (ex. hammer to knee).  Step 2 : Receptor initiates an impulse in a sensory neuron, which carries impulse to spinal cord.

31. NERVOUS SYSTEM  Step 3 : Within spinal cord, sensory neuron synapses with interneuron, which then synapses with motor neuron.  Step 4 : Motor neuron transmits impulse to effector (knee kicks out!)

32. REFLEX ARC

33. NERVOUS SYSTEM C. Parts of the Human Nervous System:

34. Nervous System  The Nervous system is divided into 2 parts:  The central nervous system (CNS) and the  Peripheral nervous system (PNS)

36. Nervous System  All body functions are coordinated by communication between the central nervous system and the peripheral nerves.

38. NERVOUS SYSTEM 1. Central Nervous System (CNS):  Brain and spinal cord  Relays messages, processes and analyzes information

39. NERVOUS SYSTEM  A. BRAIN  Large mass of neurons located in cranial cavity.  Has about 100 billion neurons!  Surrounded by skull for protection.  Controls the other organ systems of the body  Activates muscles  Causes secretion of chemicals (like hormones)

42. NERVOUS SYSTEM Brain continued:  Allows organism to respond to changes in the internal and external environment  FYI: 1 of most active organs in body – weighs only a few pounds, but receives 20% of blood pumped by heart!  Made of 3 parts that control different functions in body:  Cerebrum, cerebellum, medulla

44. NERVOUS SYSTEM  1. Cerebrum:  Largest part of brain  Center for VOLUNTARY (conscious) activities.  Where reasoning, memory, thinking occur.  Left hemisphere = (analytical, math ability) and controls right side; right hemisphere = (artistic ability, creativity) and controls left side.

45.  Left vs. Right Brain Information!  http://www.ucmas.ca/our-programs/whole- brain-development/left-brain-vs-right-brain/ http://www.ucmas.ca/our-programs/whole- brain-development/left-brain-vs-right-brain/

46. NERVOUS SYSTEM  FYI: Cerebrum is made of 2 layers  Outer layer Cerebral cortex – made of gray matter Gray matter = densely packed nerve cell bodies  Inner layer Made of white matter = bundles of axons with myelin sheaths

48. NERVOUS SYSTEM  2. Cerebellum:  2nd largest region  Controls and coordinates MOTOR activities (movement) and aids in maintaining balance.

49. NERVOUS SYSTEM  3. Medulla:  Also called brain stem.  Connects brain with spinal cord.  Controls involuntary activities (breathing, heartbeat, blood pressure, peristalsis)  FYI: (Medulla oblongata = lower portion of brain stem)

51. NERVOUS SYSTEM  Other parts of brain:  Thalamus: Relay station for sensory information

52. NERVOUS SYSTEM  Hypothalamus:  Below thalamus  Controls coordination of nervous and endocrine systems  Helps to control body temp, blood pressure, fatigue, emotions, hunger.

55. NERVOUS SYSTEM  B. Spinal Cord:  Structure that is continuous with brain.  Protected by spinal column.

56. NERVOUS SYSTEM  Spinal Cord continued:  Coordinates activities between brain and other structures.  CENTER FOR REFLEX ACTIONS – PART OF REFLEX ARC.  Pathway from sensory neurons to interneuron to motor neurons to effector.

59. NERVOUS SYSTEM  2. Peripheral Nervous System (PNS): All nerves in body “around” or outside of the CNS.  Transmits impulses from sense organs to central nervous system and from central nervous system to muscles and glands.

61. NERVOUS SYSTEM  * The PNS is divided into 2 different systems based on what each group of nerves control.

63. NERVOUS SYSTEM  A. Somatic Nervous System:  Consists of nerves that coordinate and control the VOLUNTARY (conscious) muscles of the skeletal system (we can control the actions of these muscles)

64. NERVOUS SYSTEM  B. Autonomic Nervous System:  Consists of nerves that control muscles which are INVOLUNTARY (we cannot control these muscles – they are automatic)

65. NERVOUS SYSTEM  Examples:  Heartbeat = cardiac muscle  Peristalsis = smooth muscle tissue  Glands = secretion of hormones.

67. When Things Go Wrong: Disruptions in Homeostasis  1. Alzheimer’s Disease  Brain disease that causes problems with memory, thinking, and behavior  Progressive disease – worsens over time  No cure http://www.alz.org/alzheimers_disease_4719.asp

69. When Things Go Wrong: Disruptions in Homeostasis  2. Stroke  When blood supply to part of the brain is interrupted  Deprives brain tissue of food and oxygen  Brain cells die

70. When Things Go Wrong: Disruptions in Homeostasis 3. Spinal Cord Injuries  Due to a blow or fracture that dislocates the vertebrae  Complete spinal cord injury – paralyzed below the level of injury

72. When Things Go Wrong: Disruptions in Homeostasis  4. Multiple Sclerosis  Disease in which body’s immune system eats away at myelin sheath  Interferes with body’s ability to communicate  May result in deterioration of nerves

74. When Things Go Wrong: Disruptions in Homeostasis  5. Infections:  Meningitis  Disease caused by inflammation of the protective membranes covering the brain and spinal cord- meninges.  Usually caused by an infection of the fluid surrounding the brain and spinal cord.  May develop in response to a number of causes, usually bacteria or viruses, but meningitis can also be caused by physical injury, cancer or certain drugs.

75. When Things Go Wrong: Disruptions in Homeostasis  Botulism  Botulinum toxin prduced by bacteria is one of most poisonous substances known  1 gram – if dispersed and ingested could kill 2 million people  Toxin produces a protein that blocks release of acetylcholine (neurotransmitter) that tells a muscle to contract

76. When Things Go Wrong: Disruptions in Homeostasis  Botox –  Drug that contains extremely dilute form of the poison  Has been found to be safe and effective for various applications http://www.botoxcosmetic.com/Why_Botox.aspx

77. Videos  Video – ‘Synesthesia-The Man Who Tasted Shapes’ (on server-12 min.)  Video – Anancephaly (on server – 12 min.)  Nova – ‘How the Brain Works’