Download Spinal Cord and Nerves

Bell Work
1.
2.
3.
4.
What is the spinal cord?
What is used to protect the spinal cord?
What animal does equestrian refer to?
Which way are afferent signal carried? What
about efferent?
5. What does the word “mixed” mean?
6. What is 1-12 in roman numerals?
7. Why do you think some processes would be
handled by either the brain stem or spinal cord
and not by the brain?
We talked about the brain, but the
other part of the CNS is called the…
Spinal Cord
• It is a cylindrical cord that measures about 17
inches that extends from the foramen magnum of
the skull to about the second lumbar vertebra
(just below the ribs)
• After the second vertebra, the spinal cord breaks
into spinal nerves that look like a horse’s tail and
is therefore called the cauda equina.
• It provides a two way communication pathway to
and from the brain
• It is protected by meninges and the vertebrae
Figure 7.18 (Page 247)
and 7.19 (Page 248)
Both the brain and spinal cord
have nerves that go to specific
parts of the body
So, what is a nerve?
• A bundle of neuron fibers found outside the CNS
• Each nerve fiber is surrounded by a
endoneurium.
• Groups of these fibers are surrounded by another
connective tissue wrapping called the
perineurium and form bundles called fascicles.
• Fascicles are bound together by a final, tough
sheath called the epineurium to form the cordlike
nerve
Figure 7.20
from 249
Nerve Classifications
• Sensory or afferent nerves – only carry
impulses toward the CNS
• Motor or efferent nerves – only carry impulses
away from the CNS
• Mixed nerve – nerves that carry both sensory
and motor fibers
The 12 Pairs of Cranial Nerves
• I – Olfactory (smell)
• II – Optic (vision)
• III – Oculomotor (major eye movements: pupil
dilation, following motions with your eyes)
• IV – Trochlear (resposible for the superior oblique
eye muscle)
• V – Trigeminal (sensory impulses of the skin of
the face and activates chewing)
• VI – Abducens (lateral eye movement)
The 12 Pairs of Cranial Nerves
• VII – Facial (anterior taste, facial expression,
lacrimal and salivary glands)
• VIII – Vestibulocochlear (hearing and balance)
• IX – Glossopharyngeal
• (throat, posterior taste and some swallowing)
• X – Vagus (throat and digestive system)
• XI – Accessory (control neck and back movement)
• XII – Hypoglossal (tongue movement)
Figure 7.21
from Page 252
Blue are
sensory nerves;
red are motor
nerves
There are 31 Pairs of Spinal Nerves, but
we are not going to worry about those)
• Named for the region they arise, but more
importantly, soon after the spinal nerves are
formed, they split into a dorsal and ventral
rami
• Dorsal rami serve posterior body trunk
• Ventral rami tend to form complex nerve
networks called plexuses, which serve the
motor and sensory needs of the limbs.
• Largest nerve in the body, the sciatic nerve
from the sacral plexus
The Autonomic System
• Also called the involuntary nervous system
• It is the motor subdivision of the PNS
• Controls body activities automatically mostly
from the brain stem or spinal cord
• Regulates cardiac muscle, smooth muscle, and
glands
• Has two divisions, which do opposite things:
– Sympathetic – mobilizes the body during extreme
situations (“flight or fight” system)
– Parasympathetic – allows us to unwind and conserve
energy (“resting and digesting” system)
Figure 7.24 from Page 260
Let’s Improve our memory
• Turn to page 261 of your book and read the
prove it to yourself section.
• Now, use this information to study and
memorize the 12 cranial nerves (name, roman
numeral, and what it does).
• I am going to give you some time, and then I
am going to “quiz” you on them.
Clicker Time