1. Memmler’s The Human Body in Health and Disease 11th edition
Chapter 9
The Nervous System: The Spinal Cord and Spinal Nerves

2. Role of the Nervous System
Nervous system coordinates all body systems
Detects and responds to stimuli
Brain and spinal cord act as switching centers
Nerves carry messages to and from centers

3. Structural Divisions Central nervous system (CNS) Brain Spinal cord
Peripheral nervous system (PNS)
Cranial nerves
Spinal nerves

4. Anatomic divisions of the nervous system.

5. Functional Divisions Somatic nervous system Controlled voluntarily
Effectors are skeletal muscles
No further subdivisions
Autonomic (or visceral) nervous system (ANS)
Controlled involuntarily
Effectors are smooth muscle, cardiac muscle, and glands
Subdivided into
Sympathetic nervous system
Parasympathetic nervous system

6. Glands; Cardiac & Smooth Muscle;
Brain
Somatic
Autonomic
Skeletal;
Voluntary control
Glands; Cardiac & Smooth Muscle;
Involuntary
Sympathetic
“Fight/ flight”
Parasympathetic
“Rest/ digest”

7. Checkpoint 9-1: What are the two divisions of the nervous system based on structure?
Checkpoint 9-2: The nervous system can be divided functionally into two divisions based on type of control and effectors. What division is voluntary and controls skeletal muscle, and what division is involuntary and controls involuntary muscles and glands?

8. Neurons and Their Functions
Functional cells of nervous system
Highly specialized
Unique structure

9. Diagram of a motor neuron. The break in the axon denotes length
Diagram of a motor neuron. The break in the axon denotes length. The arrows show the direction of the nerve impulse.
• Is the neuron shown here a sensory or a motor neuron?

10. Structure of a Neuron Cell body Nucleus Other organelles Cell fibers
Dendrites
Axons
Some are protected by myelin sheath

11. What is a dendrite? a. A neuron fiber that conducts impulses away from the cell body b. A neuron fiber that conducts impulses to the cell body c. A gap between myelin-covered axons

12. Answer: b. A neuron fiber that conducts impulses to the cell body

13. Formation of a myelin sheath.
Schwann cells wrap around the axon, creating a myelin coating.
(B) The outermost layer of the Schwann cell forms the neurilemma.
Spaces between the cells are the nodes (of Ranvier).

14. ACTIVITY
Make your own myelin covered nerve

15. Checkpoint 9-3: The neuron, the functional unit of the nervous system, has long fibers extending from the cell body. What is the name of the fiber that carries impulses toward the cell body and what is the name of the fiber that carries impulses away from the cell body?
Checkpoint 9-4: Myelin is a substance that covers and protects some axons. What color describes myelinated fibers, and what color describes unmyelinated tissue of the nervous system?

16. Types of Neurons Sensory neurons (afferent neurons)
Conduct impulses to spinal cord, brain
Motor neurons (efferent neurons)
Conduct impulses to muscles, glands
Interneurons (central or association neurons)
Conduct information within CNS

17. Nerves and Tracts Nerve: fiber bundle within PNS
Tract: fiber bundle within CNS
Organized into fascicles
Connective tissue layers
Endoneurium
Perineurium
Epineurium

18. Checkpoint 9-5: Nerves are bundles of neuron fibers in the PNS
Checkpoint 9-5: Nerves are bundles of neuron fibers in the PNS. These nerves may be carrying impulses either toward or away from the CNS. What name is given to nerves that convey impulses toward the CNS, and what name is given to nerves that transport away from the CNS?

19. Neuroglia Neuroglia (glial cells) Protect and nourish nervous tissue
Support nervous tissue
Aid in cell repair
Remove pathogens and impurities
Regulation composition of fluids around and between cells

20. Checkpoint 9-6: The nervous system’s nonconducting cells protect, nourish and support the neurons. What are these cells called?

21. The Nervous System at Work
Electrical impulses sent along neuron fibers and transmitted between cells at junctions

22. The Nerve Impulse
Plasma membrane carries electrical charge (potential)
Plasma membrane is polarized (negative charge)
Membrane potential reverses, generates electrical charge (action potential)
Resting state
Depolarization
Repolarization
Sodium/potassium (Na+/K+) pump
Myelin sheath speeds conduction

23. Question: Which ions are involved in the action potential. a
Question: Which ions are involved in the action potential? a. Potassium and calcium b. Sodium and oxygen c. Sodium and potassium

24. Answer: c. Sodium and potassium

25. Checkpoint 9-7: An action potential occurs in two stages
Checkpoint 9-7: An action potential occurs in two stages. In the first stage, the charge on the membrane reverses, and in the second stage, it returns to the resting state. What are the names of these two stages?
Checkpoint 9-8: What ions are involved in generating an action potential?

26. The Synapse Junction point for transmitting nerve impulse
Axon (presynaptic cell)
Dendrite (postsynaptic cell)
Synaptic cleft
Neurotransmitters
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Acetylcholine
Receptors

27. Neurotransmitters and Psychoactive Drugs
Psychoactive drugs affect neurotransmitter activity in the brain
Used to treat depression, anxiety, obsessive-compulsive disorder (OCD)
Selective serotonin reuptake inhibitors (Example: Prozac)
Block serotonin uptake
Others block norepinephrine, dopamine.

28. A synapse.
The end-bulb of the presynaptic (transmitting) axon has vesicles containing neurotransmitter, which is released into the synaptic cleft to the membrane of the postsynaptic (receiving) cell.
(B) Close-up of a synapse showing receptors for neurotransmitter in the postsynaptic cell membrane.

29. Question: The point of junction for transmitting a nerve impulse is called what? a. axon b. synapse c. vesicle

30. Answer: b. synapse

31. Checkpoint 9-9: Chemicals are needed to carry information across the synaptic cleft at a synapse. As a group, what are all these chemicals called?

32. The Spinal Cord Links PNS and brain
Helps coordinate impulses within CNS
Contained in and protected by vertebrae

33. Spinal cord and spinal nerves. Nerve plexuses (networks) are shown.
(A) Lateral view. (B) Posterior view. 
• Is the spinal cord the same length as the spinal column? How does the number of cervical vertebrae compare with the number of cervical spinal nerves?

34. Structure of the Spinal Cord
Unmyelinated tissue (gray matter)
Dorsal horn
Ventral horn
Gray commissure
Central canal
Myelinated axons (white matter)
Posterior median sulcus
Anterior median fissure
Ascending and descending tracts

35. Checkpoint 9-10: The spinal cord contains both gray and white matter
Checkpoint 9-10: The spinal cord contains both gray and white matter. How is this tissue arranged in the spinal cord?
Checkpoint 9-11: What is the purpose of the tracts in the white matter of the spinal cord?

36. The spinal cord.
(A) Cross-section of the spinal cord showing the organization of the gray and white matter. The roots of the spinal nerves are also shown.
(B) Microscopic view of the spinal cord in cross-section (x5).

37. The Reflex Arc Receptor detects stimulus
Sensory neuron transmits impulses to CNS
CNS coordinates impulses and organizes response
Motor neuron carries impulses away from CNS
Effector carries out response

38. Typical reflex arc. Numbers show the sequence of impulses through the spinal cord (solid arrows). Contraction of the biceps brachii results in flexion of the arm at the elbow.   
• Is this a somatic or an autonomic reflex arc? What type of neuron is located between the sensory and motor neuron in the CNS?

39. Checkpoint 9-12: What name is given to a pathway through the nervous system from a stimulus to an effector?

40. Reflex Activities Simple reflex Rapid Uncomplicated Automatic
Spinal reflex
Stretch reflex

41. Medical Procedures Involving the Spinal Cord
Lumbar puncture (spinal tap)
Cerebrospinal fluid (CSF) removed for testing
Drug administration
Anesthetic (an epidural or spinal anesthesia)
Pain medication

42. Diseases and Other Disorders of the Spinal Cord
Multiple sclerosis (MS)
Amyotrophic lateral sclerosis
Poliomyelitis
Tumors
Injuries
Monoplegia
Diplegia
Paraplegia
Hemiplegia
Tetraplegia (Quadriplegia)

43. Question: In a lumbar tap, what is removed from the body for testing? a. cerebrospinal fluid b. lymph c. bone marrow

44. Answer: a. cerebrospinal fluid

45. The Spinal Nerves 31 pairs
Each nerve attached to spinal cord by two roots
Dorsal root
Dorsal root ganglion
Ventral root
Nerves near end of cord travel together in the cord until each exits from its respective intervertebral foramen
Mixed nerves

46. Branches of the Spinal Nerves
Cervical plexus
Phrenic nerve
Brachial plexus
Radial nerve
Lumbosacral plexus
Sciatic nerve
Dermatomes

47. Dermatomes. A dermatome is a region of the skin supplied by a single spinal nerve.
• Which spinal nerves carry impulses from the skin of the toes? From the anterior hand and fingers?

48. Checkpoint 9-13: How many pairs of spinal nerves are there?

49. Disorders of the Spinal Nerves
Peripheral neuritis
Sciatica
Herpes zoster
Guillain-Barré syndrome

50. The Autonomic Nervous System (ANS)
Regulates the action of glands, smooth muscles of hollow organs and vessels, and heart muscle
Preganglionic neuron connects spinal cord to ganglion
Postganglionic neuron connects ganglion to effector

51. Checkpoint 9-14: How many neurons are there in each motor pathway of the ANS?

52. Divisions of the Autonomic Nervous System
Sympathetic nervous system
Parasympathetic nervous system

53. Sympathetic nervous system
Thoracolumbar area
Collateral ganglia
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Adrenergic system
Activated in the four E’s: excitement, emergency, embarassment, exercise

54. Parasympathetic nervous system
Arise in craniosacral areas
Terminal ganglia
Cholinergic system

55. Question: Any group of nerve cell bodies located outside the central nervous system is known as what? a. a ganglion b. a plexus c. a horn

56. Answer: a. a ganglion

57. Autonomic nervous system
Autonomic nervous system. The diagram shows only one side of the body for each division.
• Which division of the autonomic nervous system has ganglia closer to the effector organ?

58. Cellular Receptors “Docking sites” on postsynaptic cell membranes
Two types:
Cholinergic receptors
Nicotinic (bind nicotine) on skeletal muscle cells
Muscarinic (bind muscarine, a poison) on effector cells of PNS
Adrenergic receptors
Found on receptor cells of sympathetic nervous system
Bind norepinephrine, epinephrine

59. Functions of the Autonomic Nervous System
Sympathetic nervous system
Fight-or-flight response
Parasympathetic nervous system
Returns body to normal
Systems generally have opposite effects on organ

60. Checkpoint 9-15: Which division of the ANS stimulates a stress response, and which division reverses the stress response?

61. Question: What is the technical name of a “docking site” on a postsynaptic cell membrane? a. neurotransmitter b. cellular receptor c. dendrite

62. Answer: b. cellular receptor

63. QUESTIONS?