Bell Work 1.What is the spinal cord? 2.What is used to protect the spinal cord? 3.What animal does equestrian refer to? 4.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.

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