1. Peripheral nervous system Nervous system

2. Peripheral nervous system Nerves that branch from CNS and connect it to other body parts Cranial nerves Arise from the brain Spinal nerves Arise from the spinal cord

3. Peripheral branches Somatic nervous system Consist of cranial nerve fibers Connect CNS to skin and skeletal muscles Oversees conscious activities Autonomic nervous system Fibers that connect CNS to viscera Controls unconscious activities

4. Cranial nerves 12 pairs of cranial nerves 11 of the twelve originate from the brain stem The first pair arises within the cerebrum Most are mixed nerves Except those associated with special senses will be sensory Cranial nerves that only affect effectors are primarily motor fibers

5. Cranial Nerves cont. Numbers and names are associated with cranial nerves Number= order in which nerves arise from front to back of brain Names= primary functions or the general distribution of the fibers

6. Olfactory nerves (I) Associated with the sense of smell Only sensory neurons Bipolar neurons Travel along olfactory tracts from olfactory bulbs to cerebral centers Interpretation results in the sense of smell

7. Optic nerves (II) Arise from the retina to form the optic nerve Form the optic chiasma from the partial crossing over of the fibers Purely sensory Sensory impulses are interpreted as vision

8. Oculomotor (III) Arise from the midbrain and pass into the orbits of the eyes Primarily motor Connects to voluntary muscles that raise the eyelids and four of the six muscles for eye movement Superior, inferior, medial rectus, and inferior oblique Second component is part of the ANS Supplies involuntary muscles within the eyes Muscles that control lens shape and pupil size

9. Trochlear (IV) Smallest cranial nerve and arises from the midbrain to the eye Supplies motor fibers to external eye muscle (superior oblique) Aids in the ability to follow moving objects

10. Trigeminal (V) Largest cranial nerves Arise from the pons Mixed nerves with predominantly sensory portions Each sensory component includes three large branches Ophthalmic, maxillary, and mandibular divisions Ophthalmic division Sensory fibers bring impulses to the brain from the surface of the eyes, tear glands, and the skin of the anterior scalp, forehead, and upper eyelids

11. Trigeminal (V) cont. Maxillary division Carry sensory impulse from the upper teeth, upper gum, and upper lip Also from the mucous lining of the palate and the skin of the face Mandibular division Includes both sensory and motor fibers Sensory impulses transmit impulses from the scalp behind the ears, the skin of the jaw, the lower teeth, the lower gum, and the lower lip Motor branches supply muscles of mastication and muscles of the floor of the mouth

12. Abducens (VI) Small and originate from the pons Each nerve enters the orbit of the eye and supplies motor impulses to the lateral rectus Rolls the eye laterally

13. Facial nerves (VII) Arise from the lower part of the pons and emerge on the sides of the face Sensory branches associated with taste receptors on the anterior 2/3 of the tongue Motor fibers transmit impulses to muscles of facial expression Other motor fibers function in the ANS and stimulate secretions from tear glands and salivary glands

14. Vestibulocochlear nerves (VIII) Sensory nerves that arise from the medulla oblongata Two distinct parts 1. vestibular branch contain receptors involved in maintaining equilibrium 2. cochlear branch fibers located in parts of the inner ear and house hearing receptors Impulses from these branches pass through the pons and medulla to the temporal lobe for interpretation

15. Glossopharyngeal nerves (IX) Associated with the tongue and pharynx Mixed nerves that arise from the medulla, but predominantly sensory Sensory impulses from lining of pharynx, tonsils, and posterior 1/3 of the tongue Motor fibers innervate muscles of the pharynx for swallowing and salivary glands

16. Vagus nerve (X) Originate in the medulla oblongata Extends down through the neck, into the chest and abdomen Mixed nerves with both somatic and autonomic branches Somatic- impulses to muscles of the larynx associated with speech and swallowing Autonomic- heart and smooth muscles and glands of the thorax and abdomen Promotes digestion

17. Accessory (XI) Originate in the medulla oblongata and spinal cord Both cranial and spinal branches Cranial branch Joins vagus nerve and carries impulses to muscles of the soft palate, pharynx, and larynx Spinal branch Descends into the neck and supplies motor fibers to the trapezius and sternocleidomastoid muscles

18. Hypoglossal (XII) Arise from the medulla oblongata Pass into the tongue Motor fibers that carry impulses to muscles that move the tongue in speaking, chewing, and swallowing

19. Spinal nerves 31 pairs that originate from the spinal cord Named based on the level from which they arise 8 cervical pairs 12 thoracic pairs 5 lumbar pairs 5 sacral pairs 1 coccygeal Cauda equina- formed from the lumbar, sacral, and coccygeal nerves

20. Spinal nerves Emerge by two short branches or roots Dorsal root- posterior or sensory root Contains the cell bodies of the sensory neurons whose dendrites conduct impulses inward Ventral root- anterior or motor root Consist of axons from the motor neurons whose cell bodies are located in the gray matter of the spinal cord

21. Spinal nerves The main portions of the nerves combine to form complex networks called plexuses The fibers are sorted and recombined so fibers that innervate a particular peripheral body part reach it in the same nerve

22. Plexuses Cervical plexus Form from the branches of the 1 st four cervical nerves Supply the muscles and the skin of the neck Fibers from 4 th,5 th, and 6 th nerves pass into the phrenic nerve to conduct impulses to the diaphragm Brachial plexus Branches of the lower 4 cervical and 1 st thoracic nerve Supplies the muscles and skin of the arm, forearm, and hand Includes the musculocutaneous, ulnar, radial, and axillary nerves

23. Plexus cont. Lumbosacral Formed on either side of the last thoracic nerve and the lumbar, sacral, and coccygeal nerves Associated with muscles of the skin of the lower abdominal wall, external genitalia, buttocks, thighs, legs, and feet Includes the obturator, femoral, and sciatic nerves Anterior branches of thoracic nerves do not enter a plexus Instead enter spaces between ribs and become intercostal nerves Supply motor impulses to the intercostal muscles and the upper abdominal wall muscles Sensory impulses from the skin of the thorax and abdomen

24. Autonomic nervous system Functions independently and continuously without conscious effort Controls visceral functions Respond to emotional stress and prepare the body to meet the demands of strenuous physical activity

25. ANS general characteristics Peripheral nerve fibers lead to ganglia outside of the CNS Impulses they carry are integrated within the ganglia This function provides the ANS with a degree of independence from the CNS Divided into two divisions Sympathetic division Prepares the body for energy-expending, stressful, or emergency situations Parasympathetic Most active under ordinary, restful conditions Counterbalances thesympathetic and restores to resting state Some viscera have nerve fibers on each branch Divisions may act antagonistically, alternately activating, or inhibiting the actions of some viscera

26. Autonomic nerve fibers Motor nerve fibers Two neurons between the CNS and skeletal muscle Preganglionic fiber leaves the CNS and synapses with one or more neurons whose cell bodies are within the autonomic ganglion Postganglionic fiber- the axon of the second neuron, and extends to a visceral effector

27. Sympathetic division Also called the thoracolumbar division 1st neurons are in the gray matter of the spinal cord between T1 and L2 Preganglion fibers are short Most of the postganglion fibers are long Extensive divergence and can control a variety of visceral effectors and can produce a complex and coordinated response Preganglion fibers- Acetylcholine Always excitatory Postganglion fibers- Norepinephrine

28. Sympathetic activation When full activiated produces the “fight or flight” response and readies the body for a crisis Increased alertness A feeling of energy and euphoria, can be associated with disregard for danger and a temporary insensitivity to painful stimuli Increased activity in the cardiovascular and respiratory centers of the pons and medulla oblongata Leads to increased blood pressure, heart rate, breathing rate, and depth of respiration

29. Sympathetic cont. General elevation of muscle tone through stimulation of the medial and lateral pathways The person looks tense and may begin to shiver The mobilization of energy reserves through the accelerated breakdown of glycogen in muscles cells and liver cells and the release of lipids by adipose tissue

30. Parasympathetic division Ganglionic neurons are located in the same ganglion and their postganglionic fibers influence the same target organ More specific and localized than the sympathetic division Preganglion fibers arise from the brain stem and sacral region of the spinal cord Short postganglion fibers Located within or next to target organs The effects of parasympathetic stimulation are generally brief and restricted to specific organ sites

31. Parasympathetic activation These functions center on relaxation, food processing, and energy absorption Called the anabolic system because its stimulation leads to increase of nutrients in blood Constriction of pupils and focusing of the lens Restricts the amount of light that enters the pupil Secretion by digestive glands, The secretion of hormones that promote the absorption and utilization of nutrients by cells Changes in blood flow and glandular activity associated with sexual arousal

32. Parasympathetic activation cont. An increase in smooth muscle activity along the digestive tract The stimulation and coordination of defecation Contraction of the urinary bladder during urination Constriction of the respiratory passageways A reduction in heart rate And in the force of contraction Sexual arousal and the stimulation of sexual glands in both sexes