BIOL& 241 Human Anatomy & Physiology: Chapter 13&14 Peripheral & Autonomic Nervous System Overview

Peripheral Nervous System (PNS)

Neural structures outside the Central Nervous System. Afferent (sensory) receptors, Peripheral nerves, Efferent (motor) endings, and their associated ganglia.

Nerve

A bundle of axons encased in connective tissue.

Endoneurium

Connective tissue covering individual axons.

Perineurium

Connective tissue covering a fascicle of axons.

Epineurium

Connective tissue covering an entire nerve.

Cranial Nerves + Spinal Nerves

12 pairs of nerves exiting directly from the brain + Nerves exiting from the spinal cord.

Cranial Nerve I

Olfactory Nerve, smell. Tiny. Not the olfactory bulb or the tract. Pure Sensory.

Cranial Nerve II

Optic Nerve, vision. Brain tract; part that starts in eye and reaches optic chiasm = nerve, part of the axon that continues on to the thalamus is the tract. Pure Sensory.

Cranial Nerve III

Oculomotor Nerve; controls eye movement. Somatic Motor Fibers control 4 of 6 extrinsic eye muscles & muscle for eyelid. "Pure" motor.

Medial Rectus Muscle (CN III)

Turns the eye medially.

Superior Rectus Muscle (CN III)

Muscle that turns the eye upward.

Inferior Rectus Muscle (CN III)

Muscle that turns the eye downward.

Inferior Oblique Muscle (CN III)

Muscle that turns the eye upward and laterally.

Levator Palpebrae Superioris (CN III)

Muscle that lifts the upper eyelid.

Cranial Nerve IV

Trochlear Nerve; controls Superior Oblique Muscle --> turns the eye downward and laterally. "Pure" motor.

Cranial Nerve VI

Abducens Nerve; controls Lateral Rectus Muscle --> turns the eye laterally. "Pure" Motor.

Proprioception

Awareness of body position and movement.

Cranial Nerve V

Largest cranial nerve with three branches. Mixed. Proprioceptor fibers from muscles of mastication.

V1 - Ophthalmic Division (CN V)

Sensory to anterior scalp, upper eyelid, lacrimal gland, cornea, nose & nasal cavity mucosa.

V2 - Maxillary Division (CN V)

Sensory to lower eyelid, nasal cavity mucosa, palate, palate, upper lip, cheek.

V3 - Mandibular Division (CN V) (1)

Sensory to anterior tongue, lower teeth, chin, lateral (temporal) scalp.

V3 - Mandibular Division (CN V) (2)

Motor to Muscles of mastication (Masseter, Temporalis, Medial Pterygoid, Lateral Pterygoid).

Masseter

Prime mover of jaw closure; elevates mandible.

Temporalis

Closes jaw; elevates and retracts mandible.

Medial Pterygoid

Helps protract (pull anteriorly) mandible; grinding movements.

Lateral Pterygoid

Protracts mandible; forward sliding & grinding jaw movements.

Cranial Nerve VII

Large facial nerve controlling facial expression muscles. 5 branches. Sensory: Taste. Mixed.

Facial Nerve Branches

Includes temporal, zygomatic, buccal, mandibular, cervical.

Cranial Nerve VIII

Vestibulocochlear nerve (AKA Auditory Nerve) for hearing and balance (vestibular nerve: balance & equilibrium, cochlear nerve: hearing). Pure Sensory.

Cranial Nerve IX (1)

Glossopharyngeal nerve for taste and pharynx. Mixed. Innervates / senosry to posterior tongue & pharynx.

Cranial Nerve IX (2)

Motor to Stylopharyngeus Muscle & Parotid Salivary gland.

Cranial Nerve X

Vagus nerve extending beyond head and neck, to thorax and abdomen.

Cranial Nerve XI

Accessory nerve that joins Vagus with motor function to neck. "Pure" Motor.

Cranial Division (CN XI)

Motor to larynx, pharynx, and soft palate.

Spinal Root (CN XI)

Motor to trapezius and sternocleidomastoid.

Cranial Nerve XII

Hypoglossal nerve supplying the tongue. "Pure" Motor.

Spinal Nerves

Cervical (C1 - C8), Thoracic (T1 - T12), Lumbar (L1 - L5), Sacral (S1 - S5), Coccygeal (C0).

Facts about Cervical Nerves (1)

C1 starts between skull and Atlas (above the first cervical vertebra).

Facts about Cervical Nerves (2)

C8 is the last nerve below C7 (last cervical vertebra) --> 8 nerves but 7 cervical vertebrae.

Cauda Equina

Bundle of nerves resembling a horse's tail. The part where it extend beyond the spinal cord length, reaching the intervertebral foramina between the lumber and sacral vertebrae.

Dorsal Roots

Afferent sensory fibers from sensory receptors. Its ganglia relay info form sensory receptors.

Ventral Roots

Efferent motor fibers to muscles and glands. Somatic fiber for Sk. muscles. ANS efferent fibers exist.

Spinal nerves

Mixed. Neurons enter or exit it at levels appropriate to the organ they serve.

Meningeal Branch (Spinal Nerves)

Supplies meninges and spinal cord blood vessels.

Rami Communicantes (Spinal Nerves)

Connects thoracic and lumbar axons of preganglionic sympathetic neurons.

Dorsal Ramus (Spinal Nerves)

Supplies posterior body regions.

Ventral Ramus (Spinal Nerves)

Supplies anterior body (becomes intercostal nerves in the thoracic region) and forms plexuses.

Cervical Plexus

C1 - C5 supplying deep muscles of neck and shoulder, upper body skin (around ear and anterior neck).

Phrenic Nerve (Cervical Plexus)

Supplies diaphragm for breathing.

Brachial Plexus

C5 - T1. Supplies upper extremities.

Axillary/Circumflex Nerve (Brachial Plexus)

Supplies shoulder and deltoid muscle.

Musculocutaneous Nerve (Brachial Plexus)

Upper arm muscles (biceps & brachialis), sensory of forearm skin.

Median Nerve (Brachial Plexus)

Controls hand flexors & forearm (Flexor carpi radialis); responsible for Carpal Tunnel.

Ulnar Nerve (Brachial Plexus)

Supplies lower arm and hand flexors (Flexor carpi ulnaris).

Radial (Brachial Plexus)

Extensors of the back of arm (Triceps brachii).

Lumbar Plexus

T12 - L4.

Lateral Femoral Cutaneous (Lumbar Plexus)

Skin of lateral, anterior, and posterior thigh.

Femoral Nerve (Lumbar Plexus)

Largest lumbar nerve; innervates thigh flexors and knee extensors (Quadriceps, Sartorius). Skin of thigh, hip, and medial lower leg & foot.

Genitofemoral Nerve (Lumbar Plexus)

Scrotum and skin of thigh.

Obturator Nerve (Lumbar Plexus)

Thigh adductor muscles (Adductors, Gracilis).

Sacral Plexus

L4 - S4.

Pudendal Nerve (Sacral Plexus)

Skin & muscles of the perineum (pelvic cavity floor), oenis, scrotum, part of vagina.

Sciatic Nerve (Sacral Plexus)

Largest nerve; innervates hamstrings of thigh and splits into Peroneal nerve and TIbial nerve.

Peroneal Nerve (Sciatic Nerve)

Tibialis anterior & Peroneus longus.

Tibial Nerve (Sciatic Nerve)

Innervates gastrocnemius and soleus muscles.

Dermatomes

Skin areas supplied by specific spinal nerves.

Intercostal Muscles

Muscles between ribs, innervated by T2 - T11.

Referred Pain

Pain resulting from noxious stimuli of visceral organs of thorax & abdomen

Referred Pain Cause

Visceral sensory info converges with 2nd order somatic sensory neurons at same level.

Referred Pain Sensation

Dull aching, gnawing, burning.

Important Referred Pain Stimuli

Extrem stretching of tissue, ischemia (low blood flow), irritating chemicals, muscle spasms.

Reflex Arc Components

Sensory receptor, Sensory neuron, Integration center (w/o an interneuron), Motor neuron, Effector organ.

Loss of Reflex

Interruption in basic reflex arc.

Hyporeflexia

Decreased intensity; pressures on nerve root.

Hyperreflexia

Hyperactivity; interruption of upper motor neuron.

Flaccid Paralysis

Total loss of muscle tone & atrophy of muscle. Due to lower motor neuron damage (anterior horns - gray matter).

Spastic Paralysis

Increased muscle tone (reduced inhibition / no voluntary control over skeletal muscle) from upper motor neuron damage (corticospinal tract).

Autonomic Nervous System

Controls involuntary functions, subdivision of PNS.

Somatic Nervous System

Controls voluntary muscles.

ANS Controls....

Involuntary muscles (cardiac, smooth - walls of visceral organs and blood vessels), and glandular epithelial tissue.

Parasympathetic Nervous System

Resting state, conserves energy, promotes digestion. Takes care of daily conditions. Gives slower response.

Signs of Parasympathetic Nervous System

Low blood pressure/heart rate/respiratory rate, GI tract actively digesting food, skin is warm, eye pupils constricted, lenses of eye are accommodated for close vision.

Sympathetic Nervous System

Prepares body for fight or flight response. For emergency., gives instantaneous response.

Signs of Sympathetic Nervous System

Pounding heart, rapid deep breathing, cold sweaty skin, dilated eye pupils.

CN that serve PNS

Head: 3 (Oculomotor), 7 (Facial), 9 (Glossopharyngeal).

Neck & Trunk (Throax, Abdomen): 10 (Vagus).

Pelvic Splanchnic Nerves

Serve distal half colon, bladder, ureters, reproductive organs. In Sacral region (S2 - S4)

Sympathetic Nervous System Distribution

T1 to L2 (middle of spinal cord).

Preganglionic fibers

Myelinated fibers in the autonomic nervous system. White Rami.

Synapses.... (1)

At same, higher, or lower level in the sympathetic trunk. Or at collateral region after passing through the trunk.

Synapses.... (2)

Most preganglionic fibers pass through sympathetic trunk w/o synapsing, forming the splanchnic nerves.

Collateral ganglion

Ganglia located anterior to the vertebral column.

Splanchnic nerves

Nerves formed by preganglionic fibers passing through the trunk.

Postganglionic axons

Unmyelinated fibers that extend to target organs. Gray Rami.

Rami Communicantes

Associated only with sympathetic division. Never carry parasympathetic fibers.

Visceral sensory neurons

Sense chemical changes, stretch, temp, viscera irritation.

Brain interprets visceral senses as....

Hunger, fullness, pain, nausea.

Effector organs

Smooth muscle, cardiac muscle, and glands.

Somatic Nervous System Neurotransmitters

All somatic neurons: Acetylcholine (Ach). Always excitatory, stimulation causes postsynaptic potential reach threshold & muscle contracts.

Autonomic Postganglionic Neurons Neurotransmitters

Parasympathetic: Ach

Sympathetic: Norepinephrine/Noradrenaline (usually). Ach - eccrine sweat glands, arrector pili muscles of skin, sm. muscles in vessels walls for sk. muscles.

1st Order Motor Neuron

Motor neurons exiting the CNS. Somatic: Lower motor, Autonomic: Preganglionic.