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 cerebrum diencephalon brain stem cerebellum meninges
blood-brain barrier

35. Cerebrum cerebral cortex lobes primary motor cortex
gyrus
sulcus
fissure
lobes
frontal
parietal
occipital
temporal
primary motor cortex
primary somatic sensory cortex

36. Cerebrum

37. Diencephalon
thalamus
hypothalamus
epithalamus

38. Brain Stem
midbrain
pons
medulla oblongata

39. The Brain cerebellum meninges blood-brain barrier dura mater
arachnoid mater
pia mater

40. Spinal Cord

41. 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.

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

43. Functional Anatomy of the Peripheral Nervous System
nerve structure
cranial nerves
spinal nerves and nerve plexuses
autonomic nervous system

44. Nerve Structure endoneurium perineurium epineurium covers axons
bundles fascicles
epineurium
wraps nerves

45. Cranial Nerves

46. Spinal Nerves and Nerve Plexuses
31 pairs
dorsal root
ventral root
dorsal ramus
ventral ramus
plexuses

47. Autonomic Nervous System
preganglionic and postganglionic neurons
sympathetic nerves
fight-or-flight action
parasympathetic nerves
resting or digesting action

48. 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

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

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

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

52. Cerebral Palsy damage to brain motor function impairment before birth
during birth
during infancy
motor function impairment

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

54. Common Diseases and Disorders of the CNS
meningitis
multiple sclerosis
epilepsy
Parkinson’s disease
dementia and Alzheimer’s disease

55. 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