Chapter 14 Peripheral nervous system

Introduction G Consist of: Cranial and spinal nerves G PNS made Somatic - oversees voluntary activities of G Autonomic - controls involuntary activities. G Consist of: Cranial and spinal nerves G PNS made Somatic - oversees voluntary activities of G Autonomic - controls involuntary activities.

Spinal nerves G 31 pair - connected to spinal cord G Numbered in sequence G Eight cervical nerve pairs (C1 through C8) G Twelve thoracic nerve pairs (T1 through T12) G Five lumbar nerve pairs (L1 through L5) G Five sacral nerve pairs (S1 through S5) G One coccygeal nerve pair G Each spinal nerve arises from Two roots G dorsal - sensory (carries information to CNS) G Ventral - motor(carries information from CNS to efector) G Nerve Plexus G Cervical G Brachial G lumbrosacral

Dermatomes and myotomes G Dermatomes - section of skin innervated by a single spinal nerve G Myotome - segment of muscle innervated by a single spinal nerve G Dermatomes - section of skin innervated by a single spinal nerve G Myotome - segment of muscle innervated by a single spinal nerve

Cranial nerves G 12 pair G Designated by number and name G Olfactory nerve (I) G Carries information about sense of smell G Optic nerve (II) G Carries visual information from the eyes to the brain G Oculomotor nerve (III) G external eye muscles G regulate amount of light entering eye and aid in focusing on near objects G Trochlear nerve (IV) G oblique muscles of the eye G Trigeminal nerve (V) G Sensory from skin of head/teeth, chewing G Abducens nerve (VI) G muscles of the eye

Cranial Nerves cont’d G Facial nerve (VII) G superficial muscles of the face and scalp (Figure 14-11) G salivary glands G sensory fibers from taste buds G Vestibulocochlear nerve (VIII) G Two distinct divisions that are both sensory: vestibular nerve and cochlear nerve: G Vestibular nerve - semicircular canals in inner ear and transmit impulses that result in sensations of equilibrium G Cochlear nerve - sensations of hearing G Glossopharyngeal nerve (IX) G Supplies fibers to tongue, pharynx, and carotid sinus G Vagus nerve (X) G widely distributed branches G pharynx, larynx, trachea, heart, carotid body, lungs, bronchi, esophagus, stomach, small intestine, and gallbladder G Facial nerve (VII) G superficial muscles of the face and scalp (Figure 14-11) G salivary glands G sensory fibers from taste buds G Vestibulocochlear nerve (VIII) G Two distinct divisions that are both sensory: vestibular nerve and cochlear nerve: G Vestibular nerve - semicircular canals in inner ear and transmit impulses that result in sensations of equilibrium G Cochlear nerve - sensations of hearing G Glossopharyngeal nerve (IX) G Supplies fibers to tongue, pharynx, and carotid sinus G Vagus nerve (X) G widely distributed branches G pharynx, larynx, trachea, heart, carotid body, lungs, bronchi, esophagus, stomach, small intestine, and gallbladder

Cranial Nerves cont’d G Accessory nerve (XI) G Motor nerve that is an “accessory” to the vagus nerve G Innervates thoracic and abdominal viscera, pharynx, larynx, trapezius, and sternocleidomastoid G Hypoglossal nerve (XII) G Motor fibers innervate the muscles of the tongue G Contains sensory fibers from proprioceptors in muscles of the tongue G Accessory nerve (XI) G Motor nerve that is an “accessory” to the vagus nerve G Innervates thoracic and abdominal viscera, pharynx, larynx, trapezius, and sternocleidomastoid G Hypoglossal nerve (XII) G Motor fibers innervate the muscles of the tongue G Contains sensory fibers from proprioceptors in muscles of the tongue

Divisions of peripheral nervous system G Afferent - Sensory G Efferent - Motor G Somatic - under conscious control G Autonomic - not under conscious control G Afferent - Sensory G Efferent - Motor G Somatic - under conscious control G Autonomic - not under conscious control

Somatic G Skeletal muscle innervation G Acetylcholine is the neurotransmitter G Somatic Reflexes G Cranial - processed in brain G Spinal-processed in spine G Somatic reflex-involves skeletal muscle G Autonomic reflex-involves smooth muscle, cardiac muscle or gland. G Skeletal muscle innervation G Acetylcholine is the neurotransmitter G Somatic Reflexes G Cranial - processed in brain G Spinal-processed in spine G Somatic reflex-involves skeletal muscle G Autonomic reflex-involves smooth muscle, cardiac muscle or gland.

Autonomic nervous system G Function - maintaining homeostasis of visceral activities G Two divisions G Sympathetic - stress or emergency G Parasympathetic - normal conditions

Autonomic nerve fibers G Sympathetic division-come from thoracic and lumbar regions G Parasympathetic division- arise from brain stem and sacral regions G Autonomic neurotransmitters G Acetylcholine - used for sympathetic and parasympathetic G Norepinephrine, epinephrine from adrenal gland - used for sympathetic G Hormone - cortisol G Sympathetic division-come from thoracic and lumbar regions G Parasympathetic division- arise from brain stem and sacral regions G Autonomic neurotransmitters G Acetylcholine - used for sympathetic and parasympathetic G Norepinephrine, epinephrine from adrenal gland - used for sympathetic G Hormone - cortisol

Fight or flight - the stress response

Fight or flight G Increased heart rate G Coronary vessel dilation G Vascular dilation in muscles G Spleen contraction G Dilation of airways G Increased sweating and breathing rate G Shutting down of digestive processes G Emptying of bladder G Increased heart rate G Coronary vessel dilation G Vascular dilation in muscles G Spleen contraction G Dilation of airways G Increased sweating and breathing rate G Shutting down of digestive processes G Emptying of bladder

Clinically important reflexes G Knee-jerk (also known as patellar reflex)—extension of the lower leg in response to tapping the patellar tendon; tendon and muscles are stretched, stimulating muscle spindles and initiating conduction over a two-neuron reflex arc may be G Ankle jerk (also known as Achilles reflex)—extension of the foot in response to tapping the Achilles tendon; tendon reflex and deep reflex mediated by two-neuron spinal arcs; centers lie in first and second sacral segments of the cord G Babinski reflex—extension of great toe, with or without fanning of other toes, in response to stimulation of outer margin of sole; present in normal infants until approximately 11⁄2 years of age G Corneal reflex—winking in response to touching the cornea; G Abdominal reflex—drawing in of abdominal wall in response to stroking side of abdomen; G Knee-jerk (also known as patellar reflex)—extension of the lower leg in response to tapping the patellar tendon; tendon and muscles are stretched, stimulating muscle spindles and initiating conduction over a two-neuron reflex arc may be G Ankle jerk (also known as Achilles reflex)—extension of the foot in response to tapping the Achilles tendon; tendon reflex and deep reflex mediated by two-neuron spinal arcs; centers lie in first and second sacral segments of the cord G Babinski reflex—extension of great toe, with or without fanning of other toes, in response to stimulation of outer margin of sole; present in normal infants until approximately 11⁄2 years of age G Corneal reflex—winking in response to touching the cornea; G Abdominal reflex—drawing in of abdominal wall in response to stroking side of abdomen;