2. Functions of the Nervous System
1. Sensory input – gathering information
• To monitor changes occurring inside and
outside the body (changes = stimuli)
2. Integration –
• to process and interpret sensory input
and decide if action is needed.
3. Motor output
• A response to integrated stimuli
• The response activates muscles or glands
3. Structural Classification of the
Nervous System
• Central nervous system (CNS)
• Brain
• Spinal cord
• Peripheral nervous system (PNS)
• Nerve outside the brain and spinal cord
Spinal nerves
Cranial nerves
4. Functional Classification of the
Peripheral Nervous System
Sensory (afferent) division
Nerve fibers that carry information to the central
nervous system
Motor (efferent) division
Nerve fibers that carry impulses away from the
central nervous system
Two subdivisions
Somatic nervous system = voluntary
Autonomic nervous system = involuntary
5. Nervous Tissue: Neurons
• Neurons = nerve cells
• Cells specialized to transmit messages
• Major regions of neurons
• Cell body – nucleus and metabolic center
of the cell
• Processes – fibers that extend from the
cell body (dendrites and axons)
6. Neuron Anatomy
• Extensions outside the
cell body
• Dendrites – conduct
impulses toward the
cell body
• Axons – conduct
impulses away from
the cell body
7. Axons and Nerve Impulses
• Axons end in axonal terminals
• Axonal terminals contain vesicles with
neurotransmitters
• Axonal terminals are separated from the
next neuron by a gap
• Synaptic cleft – gap between adjacent
neurons
• Synapse – junction between nerves
8. Functional Classification of
Neurons
• Sensory (afferent) neurons
• Carry impulses from the sensory receptors to the CNS
• Cutaneous sense organs
• Proprioceptors – detect stretch or tension
• Motor (efferent) neurons
• Carry impulses from the central nervous system to
viscera, muscles, or glands
• Interneurons (association neurons)
• Found in neural pathways in the central nervous system
• Connect sensory and motor neurons
10. Structural Classification of Neurons
• Multipolar neurons
– many extensions
from the cell body
• Bipolar neurons –
one axon and one
dendrite
• Unipolar neurons
– have a short
single process
leaving the cell
body
11. Central Nervous System (CNS)
Regions of the
Brain
•Cerebral
hemispheres
(cerebrum)
•Diencephalon
•Brain stem
•Cerebellum
12. Regions of the Brain: Cerebrum
Cerebral Hemispheres
(Cerebrum)
Paired (left and
right) superior
parts of the brain
Includes more than
half of the brain
mass
The surface is
made of ridges
(gyri) and grooves
(sulci)
13. Regions of the Brain: Cerebrum
Lobes of the cerebrum
Fissures (deep
grooves) divide the
cerebrum into lobes
Surface lobes of the
cerebrum
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
14. Regions of the Brain: Cerebrum
Specialized areas of the cerebrum
Primary somatic sensory area
Receives impulses from the body’s sensory
receptors
Located in parietal lobe
Primary motor area
Sends impulses to skeletal muscles
Located in frontal lobe
Broca’s area
Involved in our ability to speak
16. Specialized Area of the Cerebrum
• Cerebral areas involved in special senses
• Gustatory area (taste)[in insula]
• Visual area[occipital lobe]
• Auditory area
• Olfactory area
• Interpretation areas of the cerebrum
• Speech/language region
• Language comprehension region
• General interpretation area
17. Layers of the Cerebrum
Layers of the cerebrum
Gray matter—outer layer in the cerebral cortex
composed mostly of neuron cell bodies
White matter—fiber tracts inside the gray
matter
Example: corpus callosum connects
hemispheres
Basal nuclei—islands of gray matter buried within
the white matter
18. Diencephalon
• Sits on top of the
brain stem
• Enclosed by the
cerebral heispheres
• Made of three parts
• Thalamus
• Hypothalamus
• Epithalamus
20. Thalamus
• Surrounds the third ventricle
• The relay station for sensory impulses
• Transfers impulses to the correct part of
the cortex for localization and
interpretation
21. Hypothalamus
• Under the thalamus
• Important autonomic nervous system center
• Helps regulate body temperature
• Controls water balance
• Regulates metabolism
• An important part of the limbic system
(emotions)
• The pituitary gland is attached to the
hypothalamus
22. Epithalamus
• Forms the roof of the third ventricle
• Houses the pineal body (an endocrine
gland)
• Includes the choroid plexus – forms
cerebrospinal fluid
23. Brain Stem
• Attaches to
the spinal
cord
• Parts of the
brain stem
• Midbrain
• Pons
• Medulla
oblongata
24. Brain Stem
• Midbrain
Mostly composed of tracts of nerve fibers
Has two bulging fiber tracts—cerebral peduncles
Has four rounded protrusions- corpora quadrigemina
Reflex centers for vision and hearing
Cerebral aqueduct – 3rd-4th ventricles
• Pons
The bulging center part of the brain stem
Mostly composed of fiber tracts
Includes nuclei involved in the control of breathing
25. Medulla Oblongata
• The lowest part of the brain stem
• Merges into the spinal cord
• Includes important fiber tracts
• Contains important control centers
• Heart rate control
• Blood pressure regulation
• Breathing
• Swallowing
• Vomiting
27. Protection of the Central Nervous
System
Scalp and skin
Skull and
vertebral
column
Meninges
Cerebrospinal
fluid (CSF)
Blood-brain
barrier
28. Meninges
• Dura mater
• Double-layered external covering
• Periosteum – attached to surface of the skull
• Meningeal layer – outer covering of the brain
• Folds inward in several areas
• Arachnoid layer- Middle layer
• Web-like
• Pia mater- Internal layer
• Clings to the surface of the brain
29. Cerebrospinal Fluid
• Similar to blood plasma composition
• Formed by the choroid plexus
• Forms a watery cushion to protect the
brain
• Circulated in arachnoid space,
ventricles, and central canal of the
spinal cord
31. Blood Brain Barrier
• Includes the least permeable capillaries
of the body
• Excludes many potentially harmful
substances
• Useless against some substances
• Fats and fat soluble molecules
• Respiratory gases
• Alcohol
• Nicotine
• Anesthesia
32. Spinal Cord
• Extends from the medulla oblongata
to the region of T12
• Below T12 is the cauda equina (a
collection of spinal nerves)
• Enlargements occur in the cervical
and lumbar regions
Extends from the foramen
magnum of the skull to the first or
second lumbar vertebra
31 pairs of spinal nerves arise
from the spinal cord
Cauda equina is a collection of
spinal nerves at the inferior end
33. Spinal Cord Anatomy
Internal gray matter is mostly cell bodies
Dorsal (posterior) horns
Anterior (ventral) horns
Gray matter surrounds the central canal
Central canal is filled with cerebrospinal
fluid
Exterior white mater—conduction tracts
Dorsal, lateral, ventral columns
34. Spinal Cord Anatomy
Meninges cover the spinal cord
Spinal nerves leave at the level of each vertebrae
Dorsal root
Associated with the dorsal root ganglia—
collections of cell bodies outside the
central nervous system
Ventral root
Contains axons
36. Peripheral Nervous System
• Nerves and ganglia outside the central nervous
system
• Nerve = bundle of neuron fibers
• Neuron fibers are bundled by connective tissue
• The PNS functions to convey impulses to and
from the brain or spinal cord.
• The nerves of the PNS are classified as
• cranial nerves or
• spinal nerves
37. Structure of a Nerve
• Endoneurium
surrounds each fiber
• Groups of fibers are
bound into fascicles
by perineurium
• Fascicles are bound
together by
epineurium
38. Classification of Nerves
• Mixed nerves – both sensory and motor
fibers
• Afferent (sensory) nerves – carry
impulses toward the CNS
• Efferent (motor) nerves – carry impulses
away from the CNS
39. • Cranial nerves
– 12 pairs of nerves that mostly serve the head and
neck
– The cranial nerves are designated by roman
numerals
– Their names indicate the structures innervated or
the principal functions of the nerves
– Only the pair of vagus nerves extend to thoracic
and abdominal cavities
39
40. I. Olfactory Nerve
.Sense of smell
.Damage causes impaired sense of smell
40
41. II. Optic Nerve
-Provides vision
-Damage causes blindness in visual field
41
42. III. Oculomotor Nerve
Eye movement, opening of eyelid, constriction of
pupil, focusing
Damage causes drooping eyelid, dilated pupil, double
vision, difficulty focusing and inability to move eye in
certain directions 42
43. IV. Trochlear Nerve
-Eye movement (superior oblique muscle)
-Damage causes double vision and inability
to rotate eye inferolaterally
43
44. V. Trigeminal Nerve
..Sensory to face
(touch, pain and
temperature) and
muscles of
mastication
..Damage
produces loss of
sensation and
impaired
chewing
44
45. VI. Abducens Nerve
-Provides eye movement (lateral rectus m.)
-Damage results in inability to rotate eye
laterally and at rest eye rotates medially
45
46. VII. Facial Nerve
• Motor - facial
expressions; salivary
glands and tear, nasal
and palatine glands
• Sensory - taste on
anterior 2/3’s of
tongue
• Damage produces
sagging facial
muscles and
disturbed sense of
taste (no sweet and
salty)
48. IX. Glossopharyngeal Nerve
• Swallowing,
salivation, gagging
and respiration
• Sensations from
posterior 1/3 of
tongue
• Damage results in
loss of bitter and
sour taste and
impaired
swallowing
49. X. Vagus Nerve
• Swallowing,
speech, regulation
of viscera
• Damage causes
hoarseness or loss
of voice, impaired
swallowing and
fatal if both are cut
50. XI. Accessory Nerve
• Swallowing,
head, neck and
shoulder
movement
– damage causes
impaired head,
neck, shoulder
movement;
head turns
towards injured
side
51. XII. Hypoglossal Nerve
• Tongue movements
for speech, food
manipulation and
swallowing
– if both are
damaged – can’t
protrude tongue
– if one side is
damaged – tongue
deviates towards
injured side
53. Autonomic Nervous System
• The involuntary branch of the nervous
system
• Consists of only motor nerves
• Divided into two divisions
• Sympathetic division
• Parasympathetic division
54. Autonomic Functioning
• Sympathetic – “fight-or-flight”
• Response to unusual stimulus
• Takes over to increase activities
• Remember as the “E” division = exercise,
excitement, emergency, and embarrassment
55. Autonomic Functioning
• Parasympathetic – housekeeping
activites
• Conserves energy
• Maintains daily necessary body functions
• Remember as the “D” division - digestion,
defecation, and diuresis