Chapter 9

1. Chapter 9 9.15-9.16

2. 9.15 Peripheral Nervous System

3. PNS • Consists of nerves that branch from the CNS and connect to other body parts • Includes cranial nerves and spinal nerves • Can be subdivided • somatic nervous system = conscious activities (innervates the skin and skeletal muscles) • Autonomic nervous system = unconscious activities (innervates viscera)

4. Cranial Nerves • 13 pairs • 1st pair originates in the cerebrum • Others originate in the brain stem • Use these tools to help you • On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How. • Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly.

5. Cranial Nerves • Olfactory nerves (I) • Sensory neurons • Associated with smell • Optic nerves (II) • Sensory neurons • Associated with vision • Oculomotor (III) • Primarily motor • Raise eyelids, move eyes, adjust the amount of light entering the eyes, and focus lenses

6. Cranial Nerves • Trochlear • Primarily motor neurons • Move the eyes • Sensory fibers transmit condition of eye muscles • Trigeminal • Mixed neurons • Sensory fibers for surface of eyes, tear glands, scalp, forehead, and upper eyelids • Sensory fibers for upper teeth, upper gum, upper lip, lining of the palate, and skin of the face • Sensory fibers for the jaw, lower teeth, lower gums, and lower lip • Muscles for mastication and the floor of the mouth

7. Cranial Nerves • Abducens • Primarily motor neurons • Motor fibers move the eyes • Sensory fibers transmit the condition of the muscles • Facial • Mixed neurons • Sensory fibers for taste receptors and the anterior tongue • Motor fibers for facial expression, tear glands and salivary glands

8. Cranial Nerves • Vestibulocochlear • Sensory neurons • Sensory fibers for sense of equilibrium • Sensory fibers for sense of hearing • Glossopharyngeal • Mixed • Sensory fibers for pharynx, tonsils, posterior tongue, and carotid arteries • Motor fibers for pharynx used in swallowing and to salivary glands

9. Cranial Nerves • Vagus • Mixed neurons • Somatic motor fibers for speech and swallowing • Autonomic motor fibers for the heart, smooth muscles, and glands in the thorax and abdomen • Sensory fibers for pharynx, larynx, esophagus, and viscera of the thorax and abdomen

10. Cranial Nerves • Accessory • Primarily motor • Motor fibers for soft palate, pharynx, and larynx • Motor fibers for neck and back • Hypoglossal • Primarily motor • Motor fibers for tongue

11. Spinal Nerves • 31 pairs originating from the spinal cord • All are mixed • Grouped according to the level from which they arise • Cervical nerves – 8 • Thoracic nerves – 12 • Lumbar nerves – 5 • Sacral nerves – 5 • Coccygeal nerves – 1

12. Spinal Nerves • Dorsal root – posterior sensory root • Ventral root – anterior motor root • Plexuses – A network of interlaced nerves • Spinal nerve fibers are sorted and recombined so that fibers that innervate a particular peripheral body part reach it in the same nerve, even though the fibers originate from different spinal nerves

13. Spinal Nerves • Cervical plexuses – supply muscles of the skin, neck, and diaphragm • Brachial plexuses – supply the muscles and skin of the arm, forearm, and hand • Lumbosacral plexuses – supply the muscles and skin of the lower abdominal wall, external genetalia, buttocks, thighs, legs, and feet

14. Spinal Nerves • Anterior branches of the thoracic spinal nerves enter spaces between the ribs (intercostal nerves) • Supply motor impulses to the intercostal muscles and upper abdominal wall • Receive sensory impulses from the skin of the thorax and abdomen

15. 9.16 Autonomic Nervous System

16. ANS • Functions continuously without conscious effort • Regulates the actions of smooth muscles, cardiac muscles, and glands • Regulates heart rate, blood pressure, breathing rate, body temp, etc. • Maintain homeostasis • Responds to emotional stress and prepares the body to meet the demands of strenuous physical activity

17. General Characteristics • Includes 2 divisions • Sympathetic division • Parasympathetic division • Viscera have nerve fibers from both divisions • Each activates some organs, but inhibits others

18. Sympathetic Division • Prepares the body for energy-expending, stressful, or emergency situations • Fight of flight response

19. Parasympathetic Division • Most active under ordinary, restful conditions • Returns the body to a resting state following a stressful experience

20. Autonomic Nerve Fibers • Somatic nervous system - requires one neuron to travel from the brain to the effecter organ • Autonomic nervous system – requires two neurons to get from the brain to the organ • Preganglionic fiber – Cell body is located in the brain or spinal cord, but the axon leaves the CNS and end in the autonomic ganglion • Postganglionic fiber – Cell body is in the autonomic ganglion and the axon extends to the visceral effector

21. Autonomic Neurotransmitters • Preganglionic fibers (both sympathetic and parasympathetic) secrete acetylcholine (cholinergic fibers) • Parasympathetic postganglionic fibers cholinergic also • Sympathetic postganglionic fibers secrete norepinephrine (adrenergic fibers) • Cause the effects of organs to be different!