Transcript Nerve activates contraction - Silver Falls School District

Chapter 7
The Brain
Regions of the Brain
1. Cerebral
hemispheres
2. Diencephalon
3. Brain stem
4. Cerebellum
A good indication of intelligence is brain weight in relation to body weight. Sperm whale = largest brain 20 lbs.
Mammal Body weight
Blue whale
60 000 kg
Lion
200 kg
Rat
200 g
Human
70 kg
Brain weight
6kg
200g
3g
1.3 kg
How much of the animal is its brain?
0.01%
0.1%
1.5%
1.9%
1. Cerebral Hemispheres (Cerebrum)
 Paired (left and
right) superior
 more than half
of brain mass
 Gyrus, sulcus,
lobes & fissure,
gray VS white
Figure 7.13a
Specialized Area of the Cerebrum
Figure 7.13c
Layers of the Cerebrum
White matter
 Fiber tracts
inside the gray
matter
 Example:
corpus callosum
connects
hemispheres
Basal nuclei –
internal islands
of gray matter
Figure 7.13a
2. Diencephalon- Top of brain stem, in cerebrum
 3 parts
Epithalamus - has pineal body
(an endocrine gland) & choroid
plexus – makes cerebrospinal
fluid
Thalamus -Transfers impulses to
correct part of the cortex
localization and interpretation
Hypothalamus - autonomic NS
system center (regulates temp,
water balance, metabolism),
limbic sys (emotions); connects to
pituitary gland.
3. Brain Stem - Attaches to the spinal cord
Midbrain Reflex centers for
M
vision & hearing
Pons Mostly fiber tracts;
P
nuclei involved in control of
breathing
Medulla oblongata Merges
•
•
•
•
•
w/spinal cord; control centers
for:
Heart rate control
Blood pressure regulation
Breathing
Swallowing
Vomiting
MO
4. Cerebellum
 2 hemispheres
with convoluted
surfaces
 involuntary
coordination of
body
movements
Protection of the CNS
1. Scalp and skin
4. Cerebrospinal fluid
2. Skull & vertebrae
5. Blood brain barrier
3. Meninges
3. Meninges – connective tissue
 Dura mater - Double-layered
external covering; folds inward
-Periosteal – attached to
surface of the skull
-Meningeal layer – outer
covering of the brain
 Arachnoid layer – Middle,
web-like layer
 Pia mater - Internal layer,
Clings to the surface of the
brain
4. Cerebrospinal Fluid
 Similar to blood plasma
 Formed by choroid plexus
 watery cushion to protect the brain
 Circulated in arachnoid space, ventricles, &
central canal of the spinal cord
5. Blood Brain Barrier
 Includes the least permeable capillaries
 Excludes many potentially harmful
substances
 Useless against some substances
 Fats and fat soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
Cranial Nerves
 12 pairs of nerves
that mostly serve
the head and neck
 Numbered in
order, front to
back
 Most are mixed
nerves, but three
are sensory only
Spinal Cord Anatomy
 Exterior white matter – conduction tracts
 Internal gray matter - mostly cell bodies
- Dorsal (posterior) horns
- Anterior (ventral) horns
 Central canal filled w/ cerebrospinal fluid
Spinal Cord Anatomy
 Meninges cover spinal cord
 Nerves leave at each
vertebrae
 Dorsal root
 Associated with the dorsal
root ganglia – collections of
cell bodies outside the central
nervous system
Ventral root
Spinal Nerves
 pair of nerves at
each vertebrae - 31
pairs
 formed by
combination of
ventral & dorsal
roots of the spinal
cord
 nerves are named
for the region from
which they arise
Anatomy of Spinal Nerves
 Spinal nerves
divide soon after
leaving the spinal
cord
 Dorsal rami – serve
the skin and muscles
of the posterior trunk
 Ventral rami – forms
a complex of
networks (plexus) for
the anterior
Figure 7.22b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.65
Examples of Nerve Distribution
Figure 7.23