1. Nervous System: Nervous Tissue and Brain
Chapter 10
Lisa Ochs RN, BSN 2008

2. Structure of the Nervous System
Central Nervous System (CNS)
Brain
Spinal cord
Peripheral Nervous System (PNS)
Outside of the CNS
Includes nerves that connect the CNS with the rest of the body

3. Figure 10-1 Nervous system: central nervous system and peripheral nervous system.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

4. Function of the Nervous System
Sensory
Gather information from inside and outside the body and transmit back to the CNS
Integrative
Processing and interpreting information received from the sensory nerves
Motor
Causing an action or movement in response to the information received

5. Figure 10-2 Three functions of the nervous system: A, Sensory function
Figure 10-2 Three functions of the nervous system: A, Sensory function. B, Integrative function. C, Motor function.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

6. Types of Cells Neuroglia
Also called glial cells; mostly found in the CNS
Support, protect, insulate and “care for” neurons
Do not conduct nerve impulses
Include astrocytes (most abundant), ependymal cells (secrete CSF), Schwann cells, oligodendrocytes

7. Figure 10-3 Neuroglia, or glia; astrocytes and ependymal cells.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

8. Types of Cells
Neurons
Transmits information in the form of nerve impulse
Various shapes, sizes and lengths
Do not replicate (nonmitotic); cannot replace themselves when injured

9. Types of Cells Parts of a neuron Dendrites Cell body Axon
Tree like structures that receive information
Cell body
Contains the nucleus of the cell
Axon
Long extension that transmits information away from the cell body
Includes myelin sheath, nodes of Ranvier, & axon terminals

10. Figure 10-4 Structure of a neuron: A, Dendrites, cell body, axon, and axon terminals. B, Structure surrounding the axon, showing the myelin sheath, the nodes of Ranvier, and the neurilemma.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

11. Types of Cells Types of neurons Sensory Motor
Carries information from the periphery to the CNS
Also called afferent
Motor
Carries information from the CNS to the periphery
Also called efferent
Remember S.A.M.E.

12. Nerve Impulse
An electrical signal that conveys information along a neuron
Also called an action potential
Inside the cell, normal resting state is negative (polarized)
The cell changes to a positive state (depolarization) when stimulated
Returns to resting state of negative (repolarization)

13. Figure 10-5 Nerve impulse (action potential): A, Polarization, B, depolarization, and C, repolarization.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

14. Movement of Nerve Impulse
The nerve impulse travels along the length of the axon in a wave like manner
Each impulse depolarizes the next section of membrane
Each nerve impulse fires in an “all or nothing” manner; this ensures that the nerve impulse does not weaken as it travels along the axon

15. Speed of Nerve Impulse
Most axons are wrapped in myelin sheaths; the spaces between the myelin are the nodes of Ranvier; nerve impulses cannot travel through myelin
The nerve impulse jumps across the myelin to the bare nodes
This is called saltatory conduction
Myelinated fibers are considered fast-conducting fibers

16. Figure 10-8 Jumping from node to node
Figure 10-8 Jumping from node to node. A, A myelinated axon and the nodes of Ranvier. B, The nerve impulse jumps from node to node toward the axon terminal. C, The jumping of the nerve impulse resembles the jumping of a kangaroo.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

17. Structure of Synapse Synapse is the place where two neurons meet
Includes:
Synaptic cleft (space between the neuron & dendrite)
Neurotransmitters (most common is ACh and norepinepherine)
Inactivators (stop the activity of neurotransmitters)
Receptors (on the dendrite where the neurotransmitters attach)

19. Events at Synapse
The nerve impulse of the first (presynaptic) neuron causes the release of neurotransmitter into the synaptic cleft.
The neurotransmitter diffuses across the synaptic cleft and binds to the receptors on the second (postsynaptic) membrane.
The activation of the receptors stimulates a nerve impulse in the second neuron.

20. Figure 10-9 The synapse. Steps in the transfer of information across the synapse.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

21. The Brain

22. Brain Structure
Control center of the body- emotions, actions, memory, sleep/ wake, etc.
2% of total body weight; requires 20% of body’s oxygen supply
Primary source of energy is glucose
4 major areas: cerebrum, diencephalon, brain stem and cerebellum

23. Figure 10-10 Four major areas of the brain: cerebrum, diencephalon, brain stem, and cerebellum.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

24. Cerebrum Largest portion of the brain
Right and left hemispheres joined by the corpus callosum (allows the separate sides to communicate)
Each hemisphere has four lobes
Frontal
Parietal
Temporal
Occipital (sound familiar?)

26. Lobes & Function Frontal Parietal Temporal Occipital
Motor, personality, behavior, emotion, intellect
Parietal
Somatosensory (skin/ muscle, taste, speech, reading)
Temporal
Hearing, smell, memory, some speech
Occipital
Vision and vision functions (reading, distance, 3D)

28. Specific Functions
Decussation: crossing of fibers from one side of the brain to the other
Frontal lobe includes Broca’s area (left hemisphere); responsible for motor speech; patients with a stroke here suffer from expressive aphasia
Temporal & parietal lobes include Wernicke’s area; broad area that involves translating thoughts into words; damage here can result in severe language deficits (Wernicke’s aphasia)

29. Markings on the Cerebrum
Gyri (sing. gyrus)
“bumps” or elevations on the surface
Sulci (sing. sulcus)
“grooves”
The extensive folding of the cerebral tissue increases its surface area; the greater the number of folds and grooves, the more intelligent the species

30. Hmmmm…
There are time-keeping neurons in our brains.  Specifically in the prefrontal cortex and striatum of the cerebrum. Discovered recently in the brains of monkeys by researchers at MIT, these time-keeping neurons fire consistently at certain rhythms . . .
thus helping our brains to figure out when things are happening.  This helps us with rhythmic activities, of course, but also with any number of tasks and memories that rely on knowing what came first, in what order, and so on. 

31. Hmmmm…
Researchers speculate that damage to these neurons, or damage to the mechanisms that read the timing pattern, may contribute to disorders (such as Parkinson Disease) that involve ill-timed movements and other functions. 
From retrieved December 30, 2009

32. Hmmmm…
In their paper, researchers failed to speculate whether this is why A&P students know exactly when to start slamming their books shut moments before a class is scheduled to end.

33. Diencephalon
2nd main area of the brain, beneath the cerebrum and above the brain stem
Includes the thalamus and the hypothalamus

34. Diencephalon Thalamus Hypothalamus
Relay station for sensory fibers traveling from lower brain & spinal cord to sensory areas of cerebrum
Hypothalamus
Regulates many processes in the body- body temperature, water balance, metabolism
“thermostat” of the body

35. Brain Stem Connects the spinal cord with higher brain structures
Includes midbrain, pons and medulla oblongata

36. Brain Stem Midbrain Pons Medulla Oblongata
Relays sensory and motor information; reflex centers for vision and hearing
Pons
“bridge”; relays information; very important in regulating breathing rate and rhythm
Medulla Oblongata
Relays information; very important in regulating heart rate, blood pressure and respiration; called the “vital center”; also contains vomiting center

37. Cerebellum
Located under the occipital lobe and the base of the skull; “little brain”
Primarily concerned with coordination of voluntary muscle activity; balance and coordination
Persons with damage to the cerebellum may appear intoxicated

38. Other Structures Not confined to specific lobes Limbic system
“emotional brain”; responsible for various emotional states and behaviors
Reticular formation
Concerned with the sleep-wake cycle and consciousness
Sensitive to certain drugs and alcohol

39. Other Structures Memory areas
Many lobes involved in recalling thoughts and images
Short term (seconds to hours)
Long term (years to decades)

41. Protection of the CNS BONE
First layer of protection for the brain and spinal cord
Cranium and vertebral column

42. Types of skull fractures

43. Protection of the CNS MENINGES Dura mater (“tough mother”)
Three layers of membranes that surround the brain and spinal cord
Dura mater (“tough mother”)
Tough connective tissue
Arachnoid (“spider-like”)
Weblike membrane
Pia mater (“soft mother”)
Delicate, thin; lies directly over the brain and spinal cord

44. Figure 10-14 The three layers of meninges are the dura mater, arachnoid, and pia mater.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

45. Protection of the CNS CEREBROSPINAL FLUID
Third layer of protection; formed from the blood within the brain; clear fluid that resembles plasma
Composed of water, glucose, protein and ions (esp. Na+ and Cl-)
Acts as a cushion and shock absorber, also delivers nutrients and removes waste.

46. Protection of the CNS CEREBROSPINAL FLUID
Formed in the choroid plexus of the ventricles in the brain
Circulates around and through the brain and spinal cord; continuously produced and drained
Rate of production must equal rate of drainage, otherwise increased ICP will result

47. Protection of the CNS BLOOD BRAIN BARRIER
An arrangement of cells (glial astrocytes) associated with blood vessels that supply the brain and spinal cord
Act as gate keepers- allows only certain substances to cross. Most harmful substances cannot cross this barrier
Pharmacology can be difficult- most antibiotics do not cross blood-brain barrier

48. NCLEX Question
After a brain stem infarction, a nurse would observe for which condition?
Aphasia
Bradypnea
Contralateral hemiplegia
Numbness and tingling in the face

49. Rationale
2. Bradypnea, or slowed respiratory rate, would result from damage to the brain stem. The brain stem contains the control center for vital functions such as breathing, heart rate and blood pressure.

50. NCLEX Question
The nurse is caring for a client with a cerebral injury that has impaired his speech and hearing. The client most likely experienced damage to the:
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe

51. Rationale
4. The temporal lobe contains the primary control centers for speech and hearing

52. NCLEX Question
A client is experiencing problems with balance and fine gross motor function. Which area of the brain has been affected?
Cerebellum
Brain stem
Diencephalon
Cerebrum

53. Rationale
1. The cerebellum contains the control center for voluntary muscle activity and balance.

54. Disorders of the CNS

55. Bell’s Palsy

56. Types of hematomas

57. From Crowley
Coronal section of brain illustrating large cerebral hemorrhage that has compressed and displaced the cerebral ventricles.

58. Normal CT- Brain

59. Intracerebral Bleed

60. Subdural Hematoma
With midline shift

61. Intracerebral Bleed
43 year old male

62. Transcranial gunshot wound

63. Knife vs. cranium