Chapter 13: Peripheral Nervous System

Front 1

What is the PNS

Back 1

Everything outside of CNS. Telephone wires in and out. 2 divisions: A)Sensory: Receptor (afferent); B)Motor-efferent sending:has 2 subdivisions: a) Somatic (volunt) & b)Autonomic (involunt)-governed by hypothalamus-para(off)/symp (on)

Front 2

How do we comprise and classify the sensory division of the PNS?

Back 2

In general sensory division involves sensory receptor and sensation.
3 WAYS TO CLASSIFY: I) STIMULUS TYPE: a) mechanoreceptor-touch, pressure, vibration, stretch; b)thermoreceptors-heat or sensitivity to changes in temp. c)photoreceptors-light (retina of the eye); d) chemoreceptors-detect chemicals-(tasted/smelled (called olfactant) from dissolved fragments in mucosa; nociceptors-pain(they can stimulate subtypes of receptors:thermo, etc..)
II)STIMULUS LOCATION: a)exteroceptors -detect things outside of body or at body's surface- (skin, eye); b)interoceptors- (inside the body) detect-temp/chemical/tissue changes, /stretch-examples: visceroceptors (viscera)-detect c)proprioceptors-(also internal) muscles, joints, ligaments (gives you info on body's position-proprioceptive memory) link into your brain (why you can type/play piano-how far to move fingers);
III) STIMULUS STRUCTURE COMPLEXITY pg 493. includes only general senses-are the most are a)Simple receptors, (touch & pressure & proprioception) or b)Complex receptors (assoicated w/special senses) 2 WAYS TO GROUP SIMPLE RECEPTORS: 1)UNENCAPSULATED DENDRITES (a free nerve ending), A):free nerve ending-most body tissues, can include extero,thermo,chemo, B) Modified Free- extero, mechano, & C) Hair Follicle-extero, mechano; or 2)ENCAPSULATED DENDRITES: (covered), A) Meisner's corpuscle, B) Pacinian (pressure) C) Ruffini (some proprio ceptors) D) Muscle spindles (in skeletal muscles tells you how much to stretch), E) Golgi-(tendons stretch)-tied with Joint & Kinestahetic

Front 3

How is sensory PNS organized?

Back 3

3 levels: A) Receptor level: neurons getting stiumulus, sensations from skin goes to B) Circuit level: wiring patterns that get to the thalamus (ascending pathway); C) Perceptual level: helps you perceive and make decisions with what was felt (reaching cerebral cortex)

Front 4

Describe the structure of a nerve.

Back 4

From inside to outside: axon, myelin sheath around that, around every myelin is endoneurium (connective tissue that encloses the myelin sheath), bundles of endoneurium wrapped up into a fascicle covered with perineurium, fascicles are bundled w/blood vessels inside of epineurium

Front 5

What is a mixed nerve

Back 5

Carries fasicles mixed with sensory and motor nerves together. If it is cut you will loose both sensations. Most of our nerves are mixed.

Front 6

What are afferent nerves,

Back 6

Strictly sensory nerves

Front 7

What are efferent nerves?

Back 7

Strictly Motor nerves

Front 8

What exactly is meant by amitosis in nerves

Back 8

If the cell body is hurt the cell body can't repair, but the axon can be repaired.

Front 9

What is the process of nerve axon repair?

Back 9

Endoneurium will restructure and grow, Macrophages come in and eat old axon fibers, cleans up junk; Schwann cell migrate to injury site and build an inner tube (key to regeneration) provides the coating that guides regeneration, Axon starts to sprout and reconnect. Nerve axons regenerate 1 1/2 mm a day.

Front 10

What are the 2 classifications of nerves?

Back 10

31 pairs of mixed (sensory and motor) spinal nerves that supply all parts of the body, but the head and parts of the neck. 12 prs of cranial (w/ exception of 1 pair (the vagus nerve) of nerves they all innervate or sense sensations in head and neck (one goes out left and one goes out right) usually mixed.

Front 11

Describe Cranial Nerve I

Back 11

Pg 501: Cranial Nerve I: OLFACTORY NERVE: sensory only, comes out of diencephalon, runs across bottom of cranial tract, has a ganglion in the olfactory bulb, linked w/limbic system, below is ethmoid bone cribriform plates, fillaments in olfactory cavity inhale olfactant that dissolves in nasal mucosa synapse w/olfactory bulbs to filamented nerves & you perceive what you've smelled.

Front 12

Describe Cranial Nerve II

Back 12

Cranial Nerve II. Optic Nerve: Totally sensory, the 2 nerves cross called optic chiasma, and picked up in occipital area and perceived, 2 back parts, but the right portion on the back of both eyes go to the right side of brain, left portion of both eyes go to the left side of brain. Your left visual field is interpretted on the right side of the brain, and visa versa. This way they work as one eye.

Front 13

Describe Cranial Nerve III

Back 13

Cranial nerve III: Oculomotor nerve Primarily motor, to move eyes, but is a mixed nerve, passes through superior orbital fissure to innervate the eye.

Front 14

Describe Cranial nerve IV

Back 14

Cranial nerve IV. Trochlear nerve. Primarily motor, also goes through the superior orbital fissure to innervate the eye.

Front 15

Which cranial nerves all innervate the eyes?

Back 15

Cranial nerve VI-Abducens, Cranial Nerve IV-Trochlear, Cranial nerve III-Occulamotor all innervate different muscles on the eye going through the supraorbital fissure.

Front 16

Describe the cranial nerve V

Back 16

Trigeminal Nerve-largest cranial nerves branches extend from pons to face: 3 branches: 1) opthalmic:, includes-eye; 2)maxillary: nasal cavity, palate, teeth and cheek 3) mandibular: tongue, foramen ovale to tongue, dentist innoculates for lower teeth, primarily sensory to feel sensations on face.

Front 17

Describe cranial nerve VII

Back 17

Facial Nerves:5 branches: pg 506, facial nerves(hand on face picture) primarily motor: temporal, zygomatic, buccal, mandibular, cervical. Trigeminal and facial nerves work together.

Front 18

Describe cranial nerve VIII

Back 18

Vestibulocochlear nerves: primarily sensory: 2 nerves wrapped in one sheath: 1) vestibular (balance) and 2) cochlear (sound) both wrapped in one sheath and go to pons. You detect sound and motion w/same mechanism.

Front 19

Describe Cranial nerve IX

Back 19

Glossopharyngeal nerves: primarily sensory. taste and sensation. Has a big ganglia. Innervates tongue and salivary glands.

Front 20

Describe cranial nerve XII

Back 20

Hypoglossal Nerve: primarily motor, goes to tongue allowing movement to chew and speak,

Front 21

Describe cranial nerve XI

Back 21

Accessory Nerve, primarily motor: Innervates muscles; trapezius and sternocleidomastoid

Front 22

Describe cranial nerve X

Back 22

The Vagus Nerve: mixed nerve, innervates everything in your viscera, The exception nerve-goes beyond head and neck. Big Nerve that starts and stops things symp/parasymp.

Front 23

What is the Location of cell bodies in the cranial nerves?

Back 23

Sensory cell bodies are located in the cranial ganglia close to the brain stem, but outside the brain; Motor cell bodies cranial ganglia are located in the ventral gray matter (nuclei) of the brain stem. Note: if you see ganglia-means sensory, if you don't know it's motor

Front 24

T/F the olfactory and optic nerves are the only 2 that are strictly sensory

Back 24

True. The rest are mixed.

Front 25

Describe the Cranial Nerve VI

Back 25

Cranial Nerve VI is the Abducens. Innervates the eye and goes through the supraorbital fissure.

Front 26

Describe Cranial Nerve XI

Back 26

Cranial Nerve XI: Accessory Nerve; primarily motor (but still mixed), innervates the sternocleidomastoid & trapezius; the nerve that allows us to know we are tense in the neck.

Front 27

Describe the Cranial Nerve XII

Back 27

Cranial Nerve XII: Hypoglossal Nerve; primarily motor; goes to tongue (allows move and chew food and to speak.

Front 28

Are spinal nerves specific or mixed.

Back 28

31 mixed

Front 29

Describe the cervical nerves

Back 29

8 pairs above vertebrae, except the last pair which comes out below

Front 30

Describe the thoracic nerves

Back 30

12 pairs that all come out below the vertebrae.

Front 31

Describe the lumbar nerves

Back 31

5 pairs- Roots of lumbar and sacral nerves create the cauda equina.

Front 32

Describe the sacral nerves

Back 32

5 pairs that exit below and along with lumbar, the roots also make up the cauda equina

Front 33

What is the C0nerves

Back 33

Goes to coccyx

Front 34

Is the spinal nerve area mixed or specific?

Back 34

Mixed sensory, visceral, somatic-and 1-2 cm. exits the intervertebral forarmen at location corresponding to the vertebrae; then biforkates into dorsal ramus & ventral ramus-which carries mixed nerves butn ventral rami also branch to form rami communicantes (2 connection lines form ventral ramus to the sympathetic trunk ganglion) & meninges rami-rami exit intervetebral foramen in bands. Ventral rami are associated with sympathetic trunk ganglion of the ANS.

Front 35

What is the sympathetic trunk?

Back 35

Forms a chain ganglion of the autonomic nervous system hook up with rami communicantes off the ventral ramus.

Front 36

What is the extra ramus called, not the ventral or dorsal.

Back 36

The meningeal ramus, comes out of spinal nerve with other rami, and reenters the vertebral column and innervates the blood vessels that control the cord

Front 37

What do the dorsal ramus and ventral ramus innervate?

Back 37

The dorsal ramus, smallest one and innervates back muscles (motor) and skin (visceral) ; Ventral ramus goes between ribs, in bands innervating intercostal muscles and skin (cutaneous), (not the viscera, the vagus nerve does that.) Ventral ramus form plexuses with complex innervation

Front 38

What are plexuses?

Back 38

Innervated by ventral rami only-they supply anterior trunk and limbs. All except T2-T12 from plexuses. There are 4 of them:cervical, brachial, lumbar, and sacral. They are freeway interchanges, info is going out and in all nerves interlace, (those from C1 can get to C5 as well). The nerves all come together into different trunks coming from different places, with different cord input making action more refined. Advantages of nerve plexuses with their interchanging nature is their refined action-several nerves coming out giving lots of input form various cord levels, muscle in a limb receives nerve supply from more than one spinal nerve; so damage to one spinal segment cannot completely paralyze any limb muscle (the multiple levels above the injury can still contribute to innervation.

Front 39

What happens if you cut the phrenic nerve?

Back 39

You can't breathe it's over. This is why Christopher Reeve hardly survived, had to be put on a respirator.

Front 40

Describe the cervical plexus.

Back 40

Composed of C1 -C4 (not C5) is located deep in the neck under sternocleidomastoid. The cell bodies of the cervical plexus reside in the cervical enlargement of the spinal cord. There are 2 branches:1) cutaneous: 1st branch that comes out is sensory-picks up sensations from the skin-superficial. Transmits sensory impulses from the skin of the neck, ear, back of head, & shoulders. 2) motor branch-motor nerve innervates all neck muscles-trapezius, sternocleidomastoid, and diaphragm. The phrenic nerve is the most crucial nerve to the cervical plexus. Receives in put from c3 and C4. Supplies innervation to the diaphragm (muscle responsible for breathing movements) An irritation of the phrenic nerve=hiccups. Damage to both phrenic nerves (severed or if area of C3-C5 is crushed=paralysis of the diaphragm. leading to death of victim unless kept alive via a respirator.

Front 41

Describe the brachial plexus

Back 41

pg513. Provides for upper limb, arms, composed of C5-C8 & T1 which make 5 ventral rami roots. The roots come out C5-T1 roots are blue, and merge into 3 trunks: (orange) upper, middle, lower; The 3 trunks form 2 divisions: anterior (front of arm); posterior (back of arm)- The trunks separate into 3 cords among the 2 anterior and posterior divisions. 2 cords-lateral and medial serve the anterior part of the arm, and the posteror cord serves the posterior part of the arm. Main nerves in arm: 1) Axillary- going to deltoid from posterior div. 2) Musculo-cutaneous:, innvervates biceps (anterior) 3) Median- innervates flexor muscles in lower arm (anterior), 4) Ulnar- innervates funny bone to fingers (medial anterior) 5) Radial-(posterior) largest branch of brachial plexus; innervates extensors to extend allowing for elbow extension, supination of forearm, thumb abduction, & wrist-finger extension. If you have trauma to radial nerve you'll have wrist drop-inability to extend hand @wrist. Falling asleep w/arm hanging off bed=compression of radial nerve & ischemia (deprived blood supply)

Front 42

Describe the lumbosachral plexus

Back 42

Has overlapping innervation, LUMBAR PLEXUS includes L1-L4, has 2 major nerve branches: Major one is A)Femoral nerve (big nerve) largest nerve of the plexus-a motor branches innervates quadriceps, cutaneous branch innervates anterior thigh and medial surface of leg from knee to foot. B) Obturator nerve-innervates adductor muscles those that swing leg in. SACRAL PLEXUS: same nerve but involves L4(which overlaps w/lumbar plex.) through S4. Sacral has many branches; 1/2 serve the buttock & lower limbs & others innervate pelvic structures & perineum. A) SCIATIC-2 nerves wrapped into a single nerve, above back of knee it biforcates into 1)Common Fibular- innervates lateral calf & dorsum of foot & muscles of the anterolateral leg (extensors that dorsiflex (raise) the foot), & 2)Tibial nerves- courses down back of gastrocnemius to innervate lower calf & foot. B) SUPERIOR/INFERIOR NERVES: Gluteal-innervates buttocks. C)PUDENDAL NERVE-innervates genitalia, anal sphincter, urination.

Front 43

what are dermatomes?

Back 43

An innervation of the skin-the area of skin innervated by the cutaneous branches of a single spinal nerve. Mostly sensory, come off of all spinal nerves except C1. Come off on body trunk (head,neck,trunk) horizontally in line w/their spinal nerves, but in limbs they run longitudinally. A disease or imbalance of dermatomes is called shingles is associated with these. Same virus causes chickenpox in children and in adults-shingles!

Front 44

What are reflexes.

Back 44

They are governed primarily by the spinal cord. 2 TYPESof REFLEXES: 1)Inborn-intrinsic, unlearned and innvoluntary, hardwired into anatomy-example-when you touch a hot stove, or suckling-vital to survival. A predictable motor response to a stimulus-hard wired into anatomy.
2)Acquired or learned reflexes: learned responses that become automatic responses-driving a car, you know how much brake pressure or wheel turn then try someone else's car!

Front 45

Describe the reflex arc

Back 45

All reflexes occur over specific neural pathways=reflex arcs. 5 parts: 1)receptor (tack) feels stick (nociceptor) pull hand back (reflex from cord) 2) sensory neruon-unipolar neuron that takes afferent impulses to the CNS (the cord) 3) Integration center- interneurons between sensory and motor-ALWAYS FOUND IN CNS-makes sense of the stimulus and decides what to do 4) motor neuron-sends efferent impulses from integration center to effector organ-sending a response-this exits the ventral horn. 5) Effector-muscle fiber (usually) or gland cell responds to efferent impulse and ascending pathway takes impulse to brain to get "ouch" response. Example of a Somatic reaction. Example of Visceral: pupil contricts automatically

Front 46

What are encapsulated muscle spindles?

Back 46

They are wrapped and take info to brain

Front 47

How do reflexes happen?

Back 47

Various types of encapsulated fibers, (golgi tendon organs, muscle spindles...)send efferent or afferent impulses to the brain about the length of the muscle telling whether it is stretched or relaxed. The brain knows this based on impulses from action potentials. A stretched muscle sends a rapid frequency of impulses to the brain from stretch receptors-thus telling brain the muscle is stretched. A relaxed or unstretched muscle sends constand impulses to the brain.

Front 48

What is an antagonist muscle?

Back 48

Often called antagonistal pairs-one muscle causes flexion, one causes extension (bicep/tricep) Antagonist meaning they work against each other, one has to relax while the other contracts. This alternation of contracting and relaxing is called reciprocal inhibiton. I have to voluntarily inhibit one or the other.

Front 49

What are the 3 special spinal reflexes?

Back 49

pg. 5231) Patellar reflex (knee jerk)-called a stretch reflex- muscle contraction in response to stretching, the muscle that is stretched is going to contract. Sensory goes to muscle to contract, Inhibitory goes to opposite 2) Golgi tendon reflex-muscle relaxes in response to stretching-reciprocal activation, golgi tendon organ is patellar region, takes impulses to cord, biforcates, this time inhibitory goes back to same muscle, and the reciprocal is contracted, like when you kick a ball and prevents hyperextension . 3) Crossed extensor reflex-pg 526,, Grey commissure takes (triforcated) impulse across the cord, inhibitory goes to tricep, and activate the bicep woman can pull back from man,- the 3rd branch is a positive epsp goes to tricep, & ipsp to bicep to relax & can push man away.

Front 50

Name the largest cranial nerve

Back 50

Trigeminal nerve

Front 51

What is the distinguishment between visceral reflexes and somatic reflexes?

Back 51

Somatic has 1 motor neuron, and visceral has a pre and post ganglion

Front 52

How are spinal nerves named?

Back 52

Named according to where they exit the spinal cord. For instance: C1-C7 exit vertebral canal superior to the vertebrae they are named after, but C8 comes out below the vertebrae it's named for (between C7 and T1.

Front 53

Describe the function of ventral root and dorsal roots and dorsal root ganglion

Back 53

1)Ventral roots contain motor (efferent) fibers that come from ventral horn motor neurons & extend outward to skeletal muscles. 2) Dorsal roots contain sensory (afferent) fibers that come from sensory neurons in the dorsal root ganglion (they conduct impulses from peripheral receptors to the spinal cord). Both ventral root & dorsal root exit the cord to form a spinal nerve (where sensory & motor merge=mixed nerve) Mixed nerve can also carry visceral (ANS) & somatic motor together.

Front 54

What are rami communicantes?

Back 54

2 connection lines from ventral ramus to the sympathetic trunk ganglion. They are part of the ANS. Found in the thoracic region.

Front 55

What happens in a sciatic nerve injury?

Back 55

When a nerve is cut, the leg is nearly useless (leg can't flex because hamstring are paralyzed & all foot & ankle movement is lost=foot drop.) Recovery is slow & incomplete. If damage is below knee thigh function remains. Injury to tibial nerve=paralyzed calf muscles that can't plantar flex (point) the foot. Injury to common fibular=compression of the nerve ( as in sleeping wrong or a tight cast) causes foot drop.

Front 56

What is the functional classification of reflexes?

Back 56

There are somatic and visceral reflexes. Somatic activate skeletal muscle and Visceral (autonomic) reflexes activate visceral effectors (glands, smooth muscles or cardiac muscle); conducted throught the ANS. EXP. bright light shining in eyes constricts pupil automatically.

Front 57

What is reciprocal inhibition?

Back 57

The inhibition of motor neurons controlling antagonistic muscles; when one muscle is activated the antagonist (reciprocal muscle) has to be inhibited (inactivated) for 1st muscle to carry out its function; IPSPs inhibit reiciprocal muscle.