Transcript Divisions of the Nervous System

Divisions of the Nervous System
Chapter 11
Meninges- membranes surrounding the
brain & spinal cord
 Dura Mater-fibrous - (outer)
1. brain-it lines the skull, but may split,
forming a blood-filled dural sinus
2. spinal cord-has fat-filled epidural space
between dura mater and bone
 Arachnoid Mater-lines dura mater(middle)
 Pia Mater-thin, covers surface of brain &
spinal cord -vascular, nourishing (inner)
Subarachnoid space is between AM and PM
(filled with cerebrospinal fluid)
Spinal Cord
31 segments
 ends between 1st & 2nd lumbar vertebrae
 2 grooves: anterior median fissure and
posterior median sulcus
 On cross-section:
gray matter-posterior, anterior, and
lateral horns, gray commissure, central
canal (cerebrospinal fluid)
white matter- anterior, posterior, and
lateral funiculi

Brain
Three Main Regions
 Cerebrum - largest
 Cerebellum
 Brainstem
Cerebrum
2 cerebral hemispheres connected by band
of white matter called the corpus callosum
 shallow grooves on surface are sulci(sulcus)
 deep grooves are fissures (longitudinal
fissure, transverse fissure, lateral fissure)
 folds/convolutions between sulci are
gyri(gyrus)
 Lobes: frontal, parietal, occipital, temporal
 Cerebral Cortex:outer, thin layer of gray
matter

Figure 11.15a
Functions of Cerebrum
Functional Regions of Cerebral
Cortex
1. Motor Regions
a. Primary Motor Area-in precentral
gyrus(directly in front of the central sulcus)controls voluntary muscle movements(left
hemisphere controls right side, vice versa)
b. Broca’s area-usually in left hemis. muscle actions associated with speech
-regulates the patterns of breathing and
vocalization needed for normal speech
2. Sensory Regions
a. Primary Sensory Area-in postcentral
gyrus (behind the central sulcus)
- receive somatic sensory info from
receptors for touch, pressure, pain,
vibration, taste, and temp.
b. Hearing – responsible for monitoring
sound; recognizes sounds such as spoken
words

c. Vision Recognizes
images and puts them together
 Ex: when you see the symbols C, A, R this
area of the brain recognizes that those are the
letters that form the word car.
3. Association Areas-all lobes
memory, reasoning, judgment, emotional
expressions
a. General Interpretive Area (Wernicke
area)-word recognition and expression
(written interpretation)
- Plays an imp. Role in your personality
Figure 11.17
http://www.youtube.com/watch?
v=HVGlfcP3ATI
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Hemisphere Dominance
Dominant Hemisphere: language,
intellectual functions requiring verbal,
analytical, and computational skills--usually the left hemisphere
 Nondominant Hemisphere: nonverbal
functions (musical, intuitive, and emotional
expression)---usually the right hemisphere

Memory
short-term: few seconds--as long as
impulse travels
 recent: minutes or days--lost if not
consciously recalled
 long-term: results from repeated recall or
experience---promotes facilitation of
neurons

Basal Ganglia/Basal Nuclei
Basal ganglia/nuclei are masses of gray
matter deep within each cerebral
hemisphere
 They serve as a relay for motor impulses
from cortex and as a source of inhibitory
neurotransmitters such as dopamine (lack of
dopamine causes Parkinson’s disease)
 Inhibit muscular activities

Ventricles- interconnected cavities within
brain filled with cerebrospinal fluid
Lateral ventricles (1st & 2nd)-within each
cerebral hemisphere
 Third ventricle-just under the corpus
callosum
 Fourth ventricle-within brainstem, in front
of cerebellum
 A channel called the cerebral aqueduct
connects the 3rd and 4th ventricles.

Cerebrospinal Fluid
produced by choroid plexus (specialized
capillaries lining the ventricles)
 Know the flow of C-S fluid (see fig. 11.4)
 drained through arachnoid granulations
into the dural sinus
 composition is clear, slightly viscous
 functions: protection, maintains stable ionic
concentration in CNS, pathway for wastes
from CNS to blood

Diencephalon- surrounds the 3rd
ventricle
 Thalamus-sides of dienceph.-relay station
for incoming sensory impulses from other
parts of the nervous system--general
awareness of pain, touch, temp., etc.
 Hypothalamus-anterior floor of dienceph. connects to pituitary; controls pituitary;
body’s thermostat
 Mammillary bodies (2)-olfaction and
swallowing reflexes
 Pineal gland-posterior projection

Limbic System-all structures in general
region of diencephalon-Because they are
connected to the cortex, they help in
production of emotional feelings (fear,
anger, pleasure, etc.)
Brainstem
Midbrain-surrounds cerebral aqueduct;
contains all descending voluntary motor
tracts; center for visual and auditory
reflexes; postural reflexes
 Pons-bulge on anterior surface of brainstem
 Medulla Oblongata-connects to spinal
cord--contains all ascending and descending
tracts---contains many vital control centers:
cardiac, vasomotor, respiratory, vomiting,
coughing, etc.

Reticular Formation


allows cortex to be in
an aroused, conscious
state
wakeup center
Cerebellum
2 hemispheres
 gray matter surrounds the white matter
 white matter is called the arbor vitae (tree
of life)
 functions:
1. control of coordination of skeletal
muscles
2. equilibrium (receives impulses from
semicircular canals of inner ears)

Peripheral Nervous System
Each nerve is made of bundles of
neuron fibers bound by C.T. An
endoneurium surround each
individual fiber within the nerve.
Types of Nerves




Cranial Nerves
12 pairs
some sensory, some
motor, most mixed
Name and number
each (Table 11.9)
Old Otto Owens Told
Tom About Finding
Very Good Vacations
Around Hawaii



Spinal Nerves
31 pairs, all mixed
cauda equina-group
of descending spinal
nerves below end of
spinal cord but within
vertebral column
all form plexuses
except some thoracic
nerves-->become
intercostal nerves
Figure 11.25
Structure of a Spinal Nerve
Dorsal root (sensory root)--has dorsal root
ganglion (contains cell bodies of sensory
neurons)
 Ventral root (motor root)
 Branches: 1. meningeal branch-supplies
meninges, vertebrae
2. posterior branch-muscle & skin of back
3. anterior branch-muscle & skin of front &
sides of trunk--also limbs
4. visceral branch (thoracic region only) supplies viscera

Peripheral Nervous System
Somatic Division
Voluntary
1 motor neuron
Autonomic Division
Involuntary
2 motor neurons
Sympathetic Div.
"stress"
Parasympathetic Div.
"rest"
Somatic Division of PNS
voluntary
 Motor impulses lead to skeletal muscles.
 Motor pathway has 1 motor neuron.

Autonomic Division of PNS
involuntary
 Motor impulses lead to smooth muscles and
glands.
 Motor pathway has 2 motor neurons:
preganglionic fiber (myelinated) begins in
CNS and ends at a PNS ganglion;
postganglionic fiber (unmyelinated) begins
at ganglion and ends at effector.

Comparison of the effects of
sympathetic & parasympathetic
divisions on each organ
Every organ is supplied by both
sympathetic and parasympathetic impulses.
 The effects are opposite.
 See Table 11.10
