PowerPoint® presentation to accompany: Medical Assisting Third Edition Booth, Whicker, Wyman, Pugh, Thompson

1. Chapter 29 The Nervous System PowerPoint® presentation to accompany: Medical Assisting Third Edition Booth, Whicker, Wyman, Pugh, Thompson

2. Learning Outcomes 29.1 Explain the difference between the central nervous system and the peripheral nervous system. 29.2 Describe the functions of the nervous system. 29.3 Describe the structure of a neuron. 29.4 Describe the function of a nerve impulse and how a nerve impulse is created.

3. Learning Outcomes (cont.) 29.5 Describe the structure and function of a synapse. 29.6 Describe the function of the blood-brain barrier. 29.7 Describe the structure and functions of meninges. 29.8 Describe the structure and functions of the spinal cord.

4. Learning Outcomes (cont.) 29.9 Describe the location and function of cerebrospinal fluid. 29.10 Define reflex and list the parts of a reflex arc. 29.11 List the major divisions of the brain and give the general functions of each. 29.12 Explain the functions of the cranial and spinal nerves.

5. Learning Outcomes (cont.) 29.13 Describe the differences between the somatic nervous system and autonomic nervous system. 29.14 Explain the two divisions of the autonomic nervous system. 29.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system.

6. Highly complex system of two parts Central nervous system (CNS) Peripheral nervous system (PNS) Controls all other organ systems and is important for maintaining balance within those systems Introduction Disorders are numerous and often difficult to diagnose and treat

7. CNS Brain Spinal cord PNS Peripheral nerves Two sections Somatic nervous system (SNS) Skeletal or voluntary muscles Autonomic nervous system (ANS) Automatic functions General Functions of the NS

8. General Functions (cont.) • Three types of neurons • Afferent or sensory nerves • Sensory information from environment or inside body to CNS for interpretation • Efferent or motor nerves • Impulses from CNS to PNS to allow for movement or action • Interneruons • Interpretive neurons between afferent and efferent nerves in the CNS

9. ANSWER: B Apply Your Knowledge Match the following: ___ Somatic nervous system A. Motor nerves ___ Autonomic nervous system B. Governs skeletal or voluntary muscles ___ Afferent nerves C. Governs respiratory and GI systems ___ Efferent nerves D. Go-betweens or interpreters ___ Interneurons E. Sensory nerves C A E D Correct!

10. Neuron Structure • Functional cells of NS • Transmit electrochemical messages called nerve impulses to • Other neurons • Effectors (muscles or glands)

11. Neuron Structure (cont.) • Neurons lose their ability to divide • If destroyed, not replaced • Neuralgia • Support cells for neurons that can divide • Astrocytes – anchor blood vessels to nerves • Microglia – act as phagocytes • Oligodendrocytes– assist with production of myelin sheath

12. Neuron Structure (cont.) Neurons have cell body processes called nerve fibers that extend from the cell body. • Dendrites – short • Receive nerve impulses for the neuron • Axons – long • Send nerve impulses away from the cell body

13. Dendrites Schwann cells Axon Neuron Structure (cont.) • White matter– axons with myelin sheath • Schwann cells – neurological cells • Wrap around some axons • Cell membranes contain myelin • Myelin insulates axons and enables axons to send nerve impulses more quickly • Gray matter– axons without myelin sheath

14. ANSWER: F Apply Your Knowledge True or False: ___ Effectors are neurons. ___ Neurons can reproduce. ___ Astrocytes anchor blood vessels to nerve cells. ___ Microglia act as phagocytes. ___ Oligodendrocytes are reproductive cells. ___ Repolarization is the return to the resting state. They are the muscles or glands. F Neurons cannot reproduce. T T They take part in myelin production. F T GOOD JOB!

15. Nerve Impulse • Membrane potential • Neuron cell membrane at rest is in a polarized state • Inside of cell membrane is negative • Outside of cell membrane is positive due to more Na+ and K+ • As Na+ and K+ move into the cell, the membrane becomes depolarized • Inside becomes more positive • Action potential (nerve impulse) is created • Repolarization occurs when K+ and later Na+ move to the outside of the cell membrane • Return of the cell to polarized (resting) state

16. Nerve Impulse (cont.) • Impulse travels down axon to synaptic knob • Vesicles or small sacs in synaptic knob • Produce chemicals called neurotransmitters • Neurotransmitters are released by synaptic knob • Allow impulse transmission to postsynaptic structures • Dendrites • Cell bodies • Axons of other neurons

17. Nerve Impulse (cont.) • Functions of neurotransmitters • Cause muscles to contract or relax • Cause glands to secrete products • Activate or inhibit neurons

18. Apply Your Knowledge What is the function of neurotransmitters? ANSWER: Neurotransmitters cause muscles to contract or relax, cause glands to secret products, activate neurons to send nerve impulses, or inhibit neurons from sending them. Right!

19. Central Nervous System • Includes the spinal cord and brain • Blood-brain barrier • Protects layers of the membranes of the CNS • Formed by tight capillaries • Prevents unwanted substances from entering the CNS tissues • Inflammation can make more permeable

20. CNS (cont.) • Meninges –protect brain and spinal cord • Dura mater • Tough outer layer • Arachnoid mater • Middle layer (web-like) • Pia mater • Innermost and most delicate • Directly on top of brain and spinal cord • Holds blood vessels on the surface of these structures

21. CNS (cont.) • Epidural space • Above dura mater • Subdural space • Below dura mater • Subarachnoid space • Between arachnoid mater and pia mater • Contains cerebrospinal fluid (CSF) • Cushions CNS

22. CNS:Spinal Cord • Slender structure continuous with the brain • Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra • 31 spinal segments: • 8 cervical segments • 12 thoracic segments • 5 lumbar segments • 5 sacral segments • 1 coccygeal segment  

23. CNS:Spinal Cord (cont.) • Cervical enlargement • Motor neurons that controlmuscles of the arms • Lumbar enlargement • Motor neurons that control muscles of the legs

24. Gray matter Inner tissue with darker color Contains neuron cell bodies and their dendrites Divisions are called horns Central canal runs down the entire length of the spinal cord through the center of the gray matter Spinal Cord/Nerve CNS:Spinal Cord (cont.)

25. Spinal Cord/Nerve CNS: Spinal Cord (cont.) • White matter • Outer tissue • Contains myelinated axons • Divisions are called columns (funiculi) • Columns contain groups of axons called nerve tracts Spinal Cord/Nerve

26. CNS: Spinal Cord (cont.) • One function of the spinal cord is to carry sensory information to and from the brain • Ascending tracts • Carry sensory information up to the brain • Descending tracts • Carry motor information down from the brain to muscles and glands

27. Reflexes Another function of the spinal cord is to participate in reflexes Reflex – a predictable, automatic response to stimuli Interneurons CNS: Spinal Cord (cont.) Receptor Sensory Neurons Effectors Motor Neurons

28. CNS: Brain • Four sections • Cerebrum • Diencephalons • Brain stem • Cerebellum

29. Brain CNS: Brain – Cerebrum • Largest section • Two cerebral hemispheres • Connected by a thick bundle of nerve fibers called the corpus callosum • Longitudinal fissure between hemispheres • Sulci – grooves on surface • Gyri or convolutions – bumps of brain matter between sulci

30. CNS: Brain – Cerebrum (cont.) • Lobes • Frontal • Motor areas for voluntary body movements • Parietal • Somatosensory – interprets sensations • Temporal • Auditory – interprets sounds • Occipital • Interprets what a person sees Parietal Frontal Temporal Occipital

31. Cortex Outer layer – gray matter Contains about 75% of all neurons Inner layer – white matter Functions Interpret sensory information Initiate body movements Stores memories and creates emotions Ventricles Interconnected cavities within the brain Filled with CSF CNS: Brain – Cerebrum (cont.)

32. Brain CNS: Brain – Diencephalon • Between the cerebral hemispheres superior to the brain stem • Thalamus • Relay station for sensory information going to the cerebral cortex for interpretation • Hypothalamus • Maintains homeostasis by regulating vital activities

33. Connects the cerebrum to the spinal cord Midbrain Just beneath diencephalon Controls both visual and auditory reflexes Pons Rounded bulge on underside of brain stem Between midbrain and medulla oblongata Regulates respiration Medulla oblongata Inferior portion of brain stem Directly connected to spinal cord Controls many vital activities, such as heart rate, blood pressure, and breathing Brain CNS: Brain – Brain Stem

34. Brain CNS: Brain – Cerebellum • Location • Inferior to the occipital lobes of the cerebrum • Posterior to the pons and medulla oblongata • Coordinates • Complex skeletal muscle contractions that are needed for body movements • Fine movements

35. Preventing Brain and Spinal Cord Injuries • Wear appropriate protective gear for sports • Avoid diving into unknown waters • Always wear seat belts • Follow safety rules on playgrounds • Children should be in car seats appropriate for age and weight • Know how to get help quickly in emergencies • Follow traffic rules and signs while walking, biking, or driving

36. Apply Your Knowledge Answer: H SUPER! Match the following: ___ Meninges A. Carry motor information from brain ___ Ascending tracts B. Stores memories and creates emotions ___ Descending tracts C. Grooves on the surface of the cerebrum ___ Cerebral cortex D. Carry sensory information to the brain ___ Hypothalamus E. Predictable, automatic response to stimuli ___ Sulci F. Maintains homeostasis ___ Cerebellum G. Coordinates skeletal muscle contractions ___ Reflexes H. Protects the brain and spinal cord D A B F C G E

37. Peripheral Nervous System • Nerves that branch off the CNS • Peripheral nerves • Two types: • Cranial nerves • Spinal nerves

38. PNS: Cranial Nerves I.   Olfactory nerves • Carry smell information to the brain for interpretation II.  Optic nerves • Carry visual information to the brain for interpretation III. Oculomotor nerves • Found within the muscles that move the eyeball, eyelid, and iris IV. Trochlear nerves • Act in the muscles that move the eyeball.

39. PNS: Cranial Nerves (cont.) V.  Trigeminal nerves • Carry sensory information from the surface of the eye, the scalp, facial skin, the lining of the gums, and the palate to the brain for interpretation • Also found within the muscles needed for chewing VI. Abducens nerves • Act in the muscles that move the eyeball

40. PNS: Cranial Nerves (cont.) VII. Facial nerves • Found in the muscles of facial expression as well as in the salivary and tear glands • Also carry sensory information from the tongue VIII. Vestibulocochlear nerves • Carry hearing and equilibrium information from the inner ear to the brain for interpretation

41. PNS: Cranial Nerves (cont.) IX. Glossopharyngeal nerves • Carry sensory information from the throat and tongue to the brain for interpretation • Also act in the muscles of the throat X. Vagus nerves • Carry sensory information from the thoracic and abdominal organs to the brain for interpretation • Also found within the muscles in the throat, stomach, intestines, and heart

42. PNS: Cranial Nerves (cont.) XI. Accessory nerves • Found within the muscles of the throat, neck, back, and voice box XII. Hypoglossal nerves • Found within the muscles of the tongue

43. Spinal Nerves PNS: Spinal Nerves • Peripheral nerves originating from the spinal cord • 31 pairs of spinal nerves • 8 pairs of cervical nerves (C1 through C8) • 12 pairs of thoracic nerves (T1 through T12) • 5 pairs of lumbar nerves (L1 through L5) • 5 pairs of sacral nerves (S1 through S5) • 1 pair of coccygeal nerves (C0)

44. PNS: Spinal Nerves (cont.) • Dermatome • Skin segment innervated by spinal nerve • C1 is not associated with a dermatome • Ventral root • Axons of motor neurons only • Dorsal root • Axons of sensory neurons only • Dorsal root ganglion • Contains cell bodies of sensory neurons

45. Spinal Nerves PNS: Spinal Nerves (cont.) • Main portions of spinal nerves fuse to form nerve plexuses • Cervical – supply skin and muscles of neck • Phrenic nerve originates from this plexus • Controls diaphragm • Brachial – control muscles in the arms • Lumbosacral – lower abdomen, external genitalia, buttocks, thighs, legs, and feet • Sciatic nerve originates from this plexus • Controls muscles of legs

46. PNS:Somatic Nervous System • Nerves that connect the CNS to skin and skeletal muscle • “Voluntary” nervous system • Controls skeletal muscles, which are under voluntary control

47. PNS:Autonomic Nervous System • Nerves that connect the CNS to organs and other structures • “Involuntary” nervous system • Motor neurons located in ganglia • Neuron cell bodies outside the CNS

48. PNS:Autonomic Nervous System (cont.) • Sympathetic division • “Fight or flight” – Prepares body for stressful or emergency situations • Neurons release neurotransmitter norepinephrine • Increases heart and breathing rates • Slows down muscles of the stomach and intestines • Dilates pupils • Constricts blood vessels – increases blood pressure

49. PNS: Autonomic Nervous System (cont.) • Parasympathetic division • Prepares body for rest and digesting • Controls most of the body’s organs • Releases acetylcholine • Slows heart and breathing rates • Constricts pupils • Activates muscles of stomach and intestine • No communication with blood vessels • Sympathetic and parasympathetic divisions are antagonistic

50. Apply Your Knowledge What is the difference between the sympathetic and parasympathetic nervous systems? ANSWER: The sympathetic nervous system prepares the body for stress. It releases norepinephrine, causing an increase in heart and respiratory rate, slows down the GI system, and dilates pupils. The sympathetic system also controls constriction of blood vessels. The parasympathetic system prepares the body for resting and digesting. It releases acetylcholine, which slows heart and respiratory rate, constricts pupils and stimulates the GI system. It has no effect on most blood vessels. Impressive!