Chapter 14Chapter 14

Peripheral nervous systemPeripheral nervous system

IntroductionIntroduction

Consist of: Cranial and spinal nerves

PNS made Somatic - oversees voluntary activities of

Autonomic - controls involuntary activities.

Consist of: Cranial and spinal nerves

PNS made Somatic - oversees voluntary activities of

Autonomic - controls involuntary activities.

Spinal nervesSpinal nerves 31 pair - connected to spinal cord Numbered in sequence

Eight cervical nerve pairs (C1 through C8)

Twelve thoracic nerve pairs (T1 through T12)

Five lumbar nerve pairs (L1 through L5)

Five sacral nerve pairs (S1 through S5) One coccygeal nerve pair

Each spinal nerve arises from Two roots dorsal - sensory (carries information to

CNS) Ventral - motor(carries information from

CNS to efector) Nerve Plexus

Cervical Brachial lumbrosacral

31 pair - connected to spinal cord Numbered in sequence

Eight cervical nerve pairs (C1 through C8)

Twelve thoracic nerve pairs (T1 through T12)

Five lumbar nerve pairs (L1 through L5)

Five sacral nerve pairs (S1 through S5) One coccygeal nerve pair

Each spinal nerve arises from Two roots dorsal - sensory (carries information to

CNS) Ventral - motor(carries information from

CNS to efector) Nerve Plexus

Cervical Brachial lumbrosacral

Dermatomes and myotomes

Dermatomes and myotomes

Dermatomes - section of skin innervated by a single spinal nerve

Myotome - segment of muscle innervated by a single spinal nerve

Dermatomes - section of skin innervated by a single spinal nerve

Myotome - segment of muscle innervated by a single spinal nerve

Cranial nervesCranial nerves 12 pair Designated by number and name Olfactory nerve (I)

Carries information about sense of smell

Optic nerve (II) Carries visual information from

the eyes to the brain Oculomotor nerve (III)

external eye muscles regulate amount of light entering eye

and aid in focusing on near objects Trochlear nerve (IV)

oblique muscles of the eye Trigeminal nerve (V)

Sensory from skin of head/teeth, chewing

Abducens nerve (VI) muscles of the eye

12 pair Designated by number and name Olfactory nerve (I)

Carries information about sense of smell

Optic nerve (II) Carries visual information from

the eyes to the brain Oculomotor nerve (III)

external eye muscles regulate amount of light entering eye

and aid in focusing on near objects Trochlear nerve (IV)

oblique muscles of the eye Trigeminal nerve (V)

Sensory from skin of head/teeth, chewing

Abducens nerve (VI) muscles of the eye

Cranial Nerves cont’dCranial Nerves cont’d Facial nerve (VII)

superficial muscles of the face and scalp (Figure 14-11) salivary glands sensory fibers from taste buds

Vestibulocochlear nerve (VIII) Two distinct divisions that are both sensory: vestibular nerve

and cochlear nerve: Vestibular nerve - semicircular canals in inner ear and transmit

impulses that result in sensations of equilibrium Cochlear nerve - sensations of hearing

Glossopharyngeal nerve (IX)Supplies fibers to tongue, pharynx, and carotid sinus

Vagus nerve (X)widely distributed branchespharynx, larynx, trachea, heart, carotid body, lungs,

bronchi, esophagus, stomach, small intestine, and gallbladder

Facial nerve (VII) superficial muscles of the face and scalp (Figure 14-11) salivary glands sensory fibers from taste buds

Vestibulocochlear nerve (VIII) Two distinct divisions that are both sensory: vestibular nerve

and cochlear nerve: Vestibular nerve - semicircular canals in inner ear and transmit

impulses that result in sensations of equilibrium Cochlear nerve - sensations of hearing

Glossopharyngeal nerve (IX)Supplies fibers to tongue, pharynx, and carotid sinus

Vagus nerve (X)widely distributed branchespharynx, larynx, trachea, heart, carotid body, lungs,

bronchi, esophagus, stomach, small intestine, and gallbladder

Cranial Nerves cont’dCranial Nerves cont’d Accessory nerve (XI)

Motor nerve that is an “accessory” to the vagus nerve

Innervates thoracic and abdominal viscera, pharynx, larynx, trapezius, and sternocleidomastoid

Hypoglossal nerve (XII)Motor fibers innervate the muscles of the

tongueContains sensory fibers from

proprioceptors in muscles of the tongue

Accessory nerve (XI)Motor nerve that is an “accessory” to the

vagus nerve Innervates thoracic and abdominal

viscera, pharynx, larynx, trapezius, and sternocleidomastoid

Hypoglossal nerve (XII)Motor fibers innervate the muscles of the

tongueContains sensory fibers from

proprioceptors in muscles of the tongue

Divisions of peripheral nervous system

Divisions of peripheral nervous system

Afferent - Sensory Efferent - Motor

Somatic - under conscious controlAutonomic - not under conscious

control

Afferent - Sensory Efferent - Motor

Somatic - under conscious controlAutonomic - not under conscious

control

SomaticSomatic

Skeletal muscle innervationAcetylcholine is the neurotransmitterSomatic Reflexes

Cranial - processed in brainSpinal-processed in spineSomatic reflex-involves skeletal muscleAutonomic reflex-involves smooth

muscle, cardiac muscle or gland.

Skeletal muscle innervationAcetylcholine is the neurotransmitterSomatic Reflexes

Cranial - processed in brainSpinal-processed in spineSomatic reflex-involves skeletal muscleAutonomic reflex-involves smooth

muscle, cardiac muscle or gland.

Autonomic nervous system

Autonomic nervous system

Function - maintaining homeostasis of visceral activities

Two divisionsSympathetic -

stress or emergency

Parasympathetic - normal conditions

Function - maintaining homeostasis of visceral activities

Two divisionsSympathetic -

stress or emergency

Parasympathetic - normal conditions

Autonomic nerve fibersAutonomic nerve fibers Sympathetic division-come

from thoracic and lumbar regions

Parasympathetic division-arise from brain stem and sacral regions

Autonomic neurotransmittersAcetylcholine - used for

sympathetic and parasympathetic

Norepinephrine, epinephrine from adrenal gland - used for sympathetic

Hormone - cortisol

Sympathetic division-come from thoracic and lumbar regions

Parasympathetic division-arise from brain stem and sacral regions

Autonomic neurotransmittersAcetylcholine - used for

sympathetic and parasympathetic

Norepinephrine, epinephrine from adrenal gland - used for sympathetic

Hormone - cortisol

Fight or flight - the stress response

Fight or flight - the stress response

QuickTime™ and a decompressor

are needed to see this picture.

Fight or flightFight or flight

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

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

Clinically important reflexes

Clinically important reflexes

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

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

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

Corneal reflex—winking in response to touching the cornea;

Abdominal reflex—drawing in of abdominal wall in response to stroking side of abdomen;

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

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

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

Corneal reflex—winking in response to touching the cornea;

Abdominal reflex—drawing in of abdominal wall in response to stroking side of abdomen;