1. Chapter 36 The Nervous System

2. Neurons: basic unit of the NS A long cell that conducts impulses Consists of 3 regions –Cell body –Dendrites  branchlike extensions that receive impulses and carry them toward the cell body –Axon  single extension of the neuron that carries impulses away from the cell body There are 3 categories of Neurons

4. Sensory → carry impulses from the body to the spinal cord and brain

5. Motor → carry response impulses away from the brain and spinal cord to a muscle or gland

6. Inter-neurons → process incoming impulses from sensory neurons and pass response impulses on to motor neurons

8. Relaying an impulse - steps You are tapped on shoulder Receptors in the skin sense the tap Sensory neurons transmit touch message to spinal cord and brain Brain interprets message sends a response to motor neurons Motor neurons transmit a response message to shoulder muscles Neck muscles are activated and you turn your head

10. Neurons at rest Plasma membrane more permeable to potassium ions (K + ) than to sodium ions (Na + ) More K + inside the membrane More Na + outside the membrane Membrane contains a sodium/potassium (Na + /K + ) pump that pumps 3 Na + out of cell for every 2 K +

11. Three sodium ions from inside the cell first bind to the transport protein

12. Then a phosphate group is transferred from ATP to the transport protein

13. Transport protein changes shape and the sodium ions are released outside the cell

14. Two potassium ions from outside the cell then bind to the transport protein.

15. As the phosphate is removed, the protein assumes its original shape and releases the potassium ions inside the cell.

16. The Na + /K + pump –  the concentration of positive charges outside the membrane –Contributes to the inside of the membrane being more negatively charged –Helps maintain a polarized condition that can transmit impulses

17. Impulse transmission Stimulus excites neuron Ion channels open and Na + enters and depolarizes (causes a change in the charge) the membrane Depolarization moves like a wave down the length of the axon The Na + /K + pump acts to try to return the membrane to its resting state

18. Myelin Sheath (white matter) White covering of cells over the axon Insulates the axon and hinders movement of ions across the membrane (ie. ions travel down the membrane until there is a gap in the myelin sheath where they cross) The gaps are called Nodes of Ranvier Impulses jump from gap to gap Absence of myelin in masses of neurons accounts for gray color = gray matter

20. Synapse – connection between neurons Neurons lie end to end – axon to dendrite – but don’t touch The space between them is the synapse When impulses reach a synapse calcium enters the axon through channels and facilitates the release of neurotransmitters into the synapse The neurotransmitters enter the dendrites of the other neuron

22. Central Nervous System (CNS) Brain & Spinal Cord Coordinates body’s activities

23. Brain Control center of entire nervous system Three main sections

24. Cerebrum Two hemispheres connected by bundle of nerves Controls your conscious activity, intelligence, memory, language, skeletal muscle movements, and senses Outer layer = cerebral cortex, made of gray matter Four lobes

25. Frontal Lobe Plays a part in –Impulse control –Language production –Working memory –Socialization –Coordination

26. Parietal Lobe Located behind the frontal lobe Plays a part in –Spatial sense –Navigation –Knowledge of numbers & their relations

27. Temporal Lobes Located on either side of brain Plays a role in –Auditory processing (sound) –Smell –Speech –Memory

28. Occipital lobe Located at the back of the brain Plays a role in –Visual processing –Color discrimination –Motion perception

29. Cerebellum Located at the back of the brain tucked under the occipital lobe Controls balance, posture, and coordination

30. Brainstem Midbrain Pons Medulla Oblongata – controls involuntary activities such as breathing and heart rate

31. Peripheral Nervous System (PNS) All the nerves that carry impulses to the CNS Two divisions

32. Somatic Nervous System Made of –12 pairs of cranial nerves –31 pairs of spinal nerves –All their branches Relay information between your skin, CNS, and skeletal muscles

33. Autonomic Nervous System Carries impulses from CNS to internal organs Two divisions –Sympathetic NS  controls many internal functions during stress –Parasympathetic NS  controls body’s internal functions when it is at rest

35. Nervous System PNS CNS Somatic NS Voluntary Autonomic NS Involuntary Parasympathetic Rest Sympathetic stress

36. 36.2 The Senses

37. Sensing Smell Receptors are nerve endings located in upper portion of nose Chemicals initiate impulses in the Olfactory nerve that is connected to the brain Brain interprets odor

38. Sensing Taste Taste depends upon smell You taste something and the chemicals contact sensory receptors on your tongue (taste buds) Signals from taste buds travel to cerebrum Signal interpreted Regions of your tongue taste different flavors

39. Sensing Light Retina –thin layer of tissue located at the back of the eye –contains two kinds of light receptors Rods & Cones –Tissue comes together and forms the optic nerve which connects to the brain Rods adapt for vision in dim light & detect shape and movement Cones adapt for vision in bright light & identify color

40. Sensing Sound Sounds travel in waves The waves vibrate the eardrum and pass to the three bones in the middle ear malleus, incus, stapes

41. As the stapes vibrates the fluid in the cochlea to move and hit hair cells causing them to bend Hair bending produces an electrical impulse that travels along the auditory nerve to the sides of the cerebrum

42. Your sense of balance Semicircular canals maintain balance Filled with a thick fluid and lined with hair cells When you tilt your head, fluid moves, hair bends and stimulates an impulse Neuron carries impulse to brain, brain sends impulse to neck to move head back

43. Sense of touch Receptors in the skin respond to changes in temperature, pressure and pain Each receptor is different (ie. light touch receptors are on surface, heavy touch located in your joints, muscle tissue) Nerve endings that extend to the lower epidermis act as pain receptors

44. 36.3 The Effects of Drugs Drug = chemical that affects the body’s functions Interact with receptor sites on cells Can  or  rate of neurotransmitter release or interaction

45. Medicinal uses for drugs Pain –drugs manipulate impulses either at the receptor site or CNS –Analgesics – No LOC, inhibit receptors at site of pain –Narcotics – analgesics that work on the CNS, relieve severe pain

46. Analgesics Ibuprofen Aspirin Narcotics Percocet Darvocet Methadone Vicodin

47. Cardiovascular –Normalize BP, heartbeat,  pumping capacity,  small blood vessels Nervous disorders –Stimulants  activity of CNS –Depressants  activity of CNS

48. Misuse of drugs Drug abuse = inappropriate self- administration of a drug for non-medical purposes –May involve illegal drugs –Taking someone else’s prescription –Excessive use of legal drugs (alcohol) Can have serious effects on the nervous system (ie. kidney damage, cardiovascular disease)

49. Addiction = psychological or physiological dependence upon a drug Tolerance =  dosage of a drug to achieve the same effect Withdrawal = illness due to lack of a specific drug

50. Stimulants (  CNS activity) Cocaine –Artificially  neurotransmitter levels –Disrupts circulatory system by  heart rate drastically and constricts blood vessels (vasoconstriction) resulting in high blood pressure Amphetamines (ADHD, TBI drugs) –Causes chest pain, paranoia, hallucinations, and convulsions –Vasoconstrictor,  BP

51. Caffeine –  heart rate,  urination –Can lead to dehydration Nicotine –  release of epinephrine –  heart rate and blood pressure –  breathing rate and stomach acid production

52. Depressants (  CNS activity) Alcohol –Blocks movement of Na+ and Ca+ –Destroys nerve cells –Cirrhosis (hardening of the liver) caused by excessive consumption of alcohol Barbiturates (anti-anxiety drugs) –  activity in both respiratory and circulatory systems

53. Narcotics: Opiates (heroin) –Act directly on the brain –  breathing and heart rate Hallucinogens: natural & synthetic –  heart rate, BP, respiratory rate, and body temperature –Synthetic = LSD (lysergic acid diethylamide)

54. Breaking the habit Individuals usually need both medical and psychological treatment to quit Nicotine replacement therapy –Nicotine patch –Nicotine inhalers –Nicotine gum Levels of chemical are gradually decreased allowing user to adapt

55. Adios Turd Nuggets!!!!