2. The Nervous System 6
Lesson 6.1: Overview of the Nervous System Lesson 6.2: Transmission of Nerve Impulses Lesson 6.3: Functional Anatomy of the Central Nervous System Lesson 6.4: Functional Anatomy of the Peripheral Nervous System Lesson 6.5: Injuries and Disorders of the Nervous System

3. Overview of the Nervous System
Chapter 6: The Nervous System
Lesson 6.1
Overview of the Nervous System

4. The nervous system is composed of:
The function of the nervous system is to coordinate all body systems! This is accomplished by the transmission of signals (electrochemical) from body parts to the brain and back to the body parts..
The nervous system is composed of:
Neurons
Neuroglial cells (also known as neuroglia, glia, and glial cells)
Blood vessels
Connective tissue

5. Two Major Divisions

6. Organization of the Nervous System
two major divisions
central nervous system (CNS) – consists of the brain and spinal cord
peripheral nervous system (PNS) – consists of cranial nerves and spinal nerves
sensory receptors
afferent (sensory) nerves – transmit nerve impulses from the sensory receptors in the skin, muscles, and joints to the CNS
efferent (motor) nerves – transmit nerve impulses from the CNS to the muscles and glands

7. The Efferent Nerves somatic nervous system autonomic nervous system
voluntary – carries information to skeletal muscle
autonomic nervous system
involuntary – carries information to smooth muscle, cardiac muscle, and glands
sympathetic
parasympathetic

8. Central Nervous System (brain and spinal cord)
Peripheral Nervous System
(cranial and spinal nerves)
brain
cranial
nerves
Sensory division
Sensory
receptors
spinal
cord
spinal
nerves
Motor division
Somatic
Nervous
System
Skeletal
muscle
Autonomic
Nervous
System
Smooth muscle
Cardiac muscle
Glands

9. Nervous Tissues neuroglia neurons also known as glial cells
support the neurons
protect the neurons
neurons
transmit nerve impulses

10. Neuroglia central nervous system astrocytes microglia ependymal
oligodendrocytes

11. Neuroglia - CNS
Astrocytes – most numerous - positioned between neurons and capillaries – protect neurons from harmful substances in the blood
Microglia – absorb and dispose of dead cells and bacteria
Ependymal – form a protective covering around the spinal cord and central cavities within the brain
Oligodendrocytes – produce myelin (fatty insulating material that surrounds nerve fibers) l

12. Neuroglia - PNS peripheral nervous system
Schwann cells – form fatty myelin sheaths around nerve fibers
insulation from myelin sheath speeds up neurotransmission
a bundle of myelinated nerve fibers (axons) = “white matter”
a bundle of unmyelinated nerve fibers (cell bodies/dendrites) = “gray matter”
nodes of Ranvier – uninsulated gaps between sections of myelin where the axon is exposed
satellite cells – provide cushioning

13. Neuroglia - PNS

14. Parts of a Neuron
cell body (soma) - central portion of neuron - contains usual organelles
neuron processes (two types) - extensions from cell body
Dendrites – many per neuron; short & branched; receptive portion of neuron; carries impulse toward cell body
Axon - one per neuron; long, thin process; carries impulses away from cell body; terminations of axon branch = axon terminals

15. Parts of a Neuron

16. Neuron Types by Function
sensory neurons
send impulses toward CNS
motor neurons
send impulses away from CNS
interneurons
transport impulses between neurons

17. Structural Types of Neurons
Due to structural differences, neurons can be classified into three (3) major groups:
Bipolar neurons – two extensions; one fused dendrite leads toward cell body and one axon leads away from cell body ex. Specialized parts of eyes, nose, & ears (sensory)
Unipolar neurons – one process from cell body; forms central & peripheral process; only distal ends are dendrites ex. Some sensory neurons in the PNS
Multipolar neurons – many extensions; many dendrites lead toward cell body and one axon leads away from cell body ex. All motor neurons and interneurons

18. Neuron Structures
bipolar
unipolar
multipolar

19. Review and Assessment
Match these words with 1–4 below: sympathetic nervous system, myelin, synapse, axon. 1. high alert 2. transmits impulses away from cell body 3. fatty insulating material 4. gap between neurons

20. Transmission of Nerve Impulses
Chapter 6: The Nervous System
Lesson 6.2
Transmission of Nerve Impulses

21. Transmission of Nerve Impulses
Transmission of nerve impulses is an electrochemical process
Creation of an action potential is electrical
Neurotransmitters released at the synapse is chemical

22. Transmission of Nerve Impulse
When a neuron is inactive or at rest:
Potassium ions are inside the cell and sodium ions are outside the cell membrane
Inside of cell is more negatively charged than outside of cell
Difference in electrical charge inside and outside of cell = cell membrane is polarized

23. Transmission of Nerve Impulse
Activation of a neuron:
Stimulus causes the sodium channels to open
Sodium ions enter the neuron causing the inside of the membrane to become more positive = cell membrane is depolarized
Depolarization occurs only at the nodes of Ranvier
Opening of sodium channels is like a domino effect creating more sodium channels to open along the membrane = action potential (electrical impulse)
All-or-none concept – electrical charge of the action potential is always the same size and travels the full length of the axon

24. Action Potential
Direction of nerve impulse

25. Transmission of Nerve Impulse
Discharge of the action potential
Membrane becomes permeable to potassium ions
Potassium ions diffuse out of the cell
Membrane is restored to its polarized state with a more negative charge inside the cell = repolarization
Refractory period = time between the completion of the action potential and repolarization

26. Transmission of Nerve Impulse

27. Impulse Transmission Factors affecting speed of impulse transmission:
Faster in myelinated axons vs nonmyelinated axons where the myelin sheath acts as an insulator
Saltatory conduction – action potentials jump over myelinated regions of the axon
Faster in nonmyelinated axons with larger diameters vs. nonmyelinated axons with smaller diameters
Faster in warmer temps because of an increase in ions diffusion rates Ds

28. Impulse Transmission Transmission at synapses
When an action potential reaches an
axon terminal, calcium
gates open and calcium
ions flow into the terminal
Influx of calcium causes the
neurotransmitter vesicles
to release the neurotransmitter
into the synapse
Neurotransmitters connect
to a receptor site on a joining
neuron or muscle fiber

29. Introduction to Anatomy and Physiology Student Site Video.html

30. Neurotransmitters 2 types of neurotransmitters:
Excitatory neurotransmitter – acetylcholine – activates muscle fibers
Inhibitory neurotransmitter – endorphins – inhibit nerve cells from discharging more pain signals

31. Reflexes
simple, rapid, involuntary response to stimuli that follows a reflex arc involving both the PNS and CNS
2 types
Somatic reflexes – involve the stimulation of skeletal muscles – when touching a hot surface, nerve impulses travel from a sensory nerve to an interneuron in the spinal cord to a motor neuron, bypassing the brain
Reflex video.html
Autonomic reflexes – send involuntary stimuli to the cardiac muscles of the heart and the smooth muscles of the organs – digestion, elimination, sweating

32. Review and Assessment
Fill in the blanks with: reflexes, saltatory conduction, neurotransmitter, or action potential. 1. A(n) _______________ is an all or none response. 2. _______________ occurs only in myelinated axons. 3. _______________ are rapid, involuntary responses. 4. The axon terminal has tiny vesicles filled with _______________.

33. Functional Anatomy of the Central Nervous System
Chapter 6: The Nervous System
Lesson 6.3
Functional Anatomy of the Central Nervous System

34. The Brain
4 Regions
Cerebrum
Diencephalon
Brain stem
Cerebellum

35. Cerebrum cerebral cortex Outer surface of cerebrum
Contains nonmyelinated gray matter
Gyrus – curved, raised area
Sulcus – grooves between gyri
Fissure – deep grooves

36. Cerebrum

37. Cerebrum lobes primary motor cortex – anterior side of central sulcus
Frontal – memory, intelligence, behavior, emotions, motor function,
smell
Parietal – pain, touch, hot/cold, speech
Occipital – vision, speech
Temporal – hearing, smell, memory, speech
primary motor cortex – anterior side of central sulcus
primary somatic sensory cortex – posterior side of central sulcus
central sulcus – separates frontal lobes from parietal lobes

39. Motor Cortex
Somatosensory cortex

40. Diencephalon Thalamus – relays sensory impulses to the sensory cortex
Hypothalamus – autonomic center regulating metabolism, heart rate, blood pressure, hunger, thirst, energy level, and body temp
Epithalamus – regulates hormones secreted by the pineal gland

41. Diencephalon

42. Brain Stem Midbrain – relays sensory and motor impulses
Pons – assists with regulation of breathing
Medulla oblongata – regulates heart rate, blood pressure, and breathing, and controls the reflexes of coughing, sneezing, and vomiting

43. Brain Stem

44. Cerebellum Below the occipital lobe
Coordinates body movement and balance

45. Blood Brain Barrier
Substances can pass less freely through capillaries in the brain compared to capillaries in other parts of the body
Protects the brain against surges in hormones, ions, and some nutrients

46. Meninges Membranes covering brain and spinal cord
dura mater (“hard mother”) – tough, outer double-layered membrane
arachnoid mater – middle layer - web-like tissue
subarachnoid space – contains cerebrospinal fluid which cushions the brain and spinal cord
pia mater (“gentle mother”) – innermost membrane of brain and spinal cord

47. Meninges

48. Spinal Cord
Major pathway for relaying sensory impulses to the brain and motor impulses from the brain
Exterior is myelinated white matter
Butterfly-shaped gray matter, composed of neuron cell bodies and interneurons, are centrally located
Dorsal, ventral, and lateral projections of gray matter are called horns

49. Spinal Cord

50. Review and Assessment
True or False? 1. The gyri divide the brain into 4 regions. 2. The hypothalamus regulates blood pressure. 3. The meninges has 3 layers. 4. The cerebellum coordinates balance. 5. The pons is also called the interbrain.

51. Functional Anatomy of the Peripheral Nervous System
Chapter 6: The Nervous System
Lesson 6.4
Functional Anatomy of the Peripheral Nervous System

52. Peripheral Nervous System - Nerve Structure
endoneurium
covers axons
perineurium
bundles fascicles
epineurium
encases fascicles and blood vessels

53. Cranial Nerves 12 pairs Olfactory nerve – smell Optic nerve – sight
Oculomotor – eye movement
Vestibulocochlear – hearing, balance
Glossopharyngeal – throat muscle movements, taste
Vagus – autonomic control of heart, lungs, digestion, taste, communication between brain and organs

54. Cranial Nerves

55. Spinal Nerves and Nerve Plexuses
31 pairs
dorsal root (posterior) and ventral root (anterior) unite to form the left and right spinal nerves at each spinal level
dorsal ramus and ventral ramus split from the spinal nerves – carry nerve impulses to the muscle and skin of the trunk
Plexuses – interconnections of nerves formed from the ventral rami in the cervical and lumbar regions of the spinal cord
4 plexuses – cervical, brachial, lumbar, and sacral

57. Autonomic Nervous System
Involuntary nervous system that activates the heart, smooth muscles, and glands
Ganglion – enlarged junction of nerve tissue composed mainly of nerve cell bodies
Preganglionic neurons – originate in the lateral horn of the spinal cord and terminate in a ganglion
Postganglionic neurons – originate in a ganglion and terminate in a cardiac muscle, smooth muscle, or gland

58. Autonomic Nervous System

59. Autonomic Nervous System
Sympathetic nervous system
Fight-or-flight response
Sympathetic nerves stimulate the adrenal gland to release epinephrine (adrenaline) – increases heart and breathing rates and sweating
Parasympathetic nervous system
Controls automatic day-in and day-out functions of the circulatory, respiratory, and digestive systems

60. Review and Assessment
Match these words with 1–4 below: efferent, ganglion, optic, perineurium. 1. wraps fascicles 2. motor 3. a cranial nerve 4. enlarged junction

61. Injuries and Disorders of the Nervous System
Chapter 6: The Nervous System
Lesson 6.5
Injuries and Disorders of the Nervous System

62. Injuries to the Brain and Spinal Cord
traumatic brain injury
cerebral palsy
spinal cord injury

63. Traumatic Brain Injury
violent impact to head
mild
moderate
severe

64. Spinal Cord Injuries C1–C3: usually fatal C1–C4: quadriplegia
C5–C7: paralysis of lower extremities
T1–L5: paraplegia
Corepics/Shutterstock.com

65. Common Diseases and Disorders of the CNS
meningitis – inflammation of the meninges around the brain or spinal cord – can be viral or bacterial
multiple sclerosis – autoimmune disease in which the body’s immune system destroys the myelin sheaths of nerve cell axons
epilepsy – abnormal electrical activity in the brain
Parkinson’s disease – slow but progressive destruction of the brain’s cells responsible for the production of the neurotransmitter dopamine which plays a role in motor functions
dementia and Alzheimer’s disease – loss of function in 2 or more areas of cognition including memory, thinking, judgment, behavior, perception, and language

66. Review and Assessment
Match these words with 1–4 below: quadriplegia, multiple sclerosis, dementia, cerebral palsy. 1. inflammation destroys myelin sheath 2. loss of memory and thinking 3. loss of function below the neck 4. may begin before birth