The Peripheral Nervous System And Reflex Activity- Ch. 13

Front 1

PNS

Back 1

Orders are sent from CNS through the PNS to voluntary muscles and other effectors in our body.

Front 2

Sensory Receptors

Back 2

Specialized to respond to changes in their environment which are called stimuli.

Front 3

Sensation

Back 3

Awareness of stimulus

Front 4

Perception

Back 4

Interpretation of the meaning of the stimulus

Front 5

3 ways to classify sensory receptors

Back 5

1. by the type of stimulus they detect
2. by their body location
3. by their structural complexity

Front 6

Mechanoreceptors

Back 6

respond to mechanical force, touch, pressure, vibration and stretch

Front 7

Thermoreceptors

Back 7

sensitive to temp changes

Front 8

Photoreceptors

Back 8

respond to light energy

Front 9

Nociceptors

Back 9

respond to damaging stimuli that result in pain

Front 10

Exteroceptors

Back 10

sensitive to stimuli arising outside the body

Front 11

Interoceptors

Back 11

also called visceroceptors, respond to stimuliwithin the body, such as from the internal viscera and blood vessels. They monitor chemical changes, tissue stretch, and temp.

Front 12

Proprioceptors

Back 12

respond to internal stimuli; however their location is much more restricted. They occur in skeletal muscles, tendons, joints, and ligamnes and in CT coverings of bone and muscle.

Front 13

Simple Receptors

Back 13

majority are simple. The simple are modified dendritic endingd of sensory neurons. They are foudn throughout the body and monitor most types of general sensory info.

Front 14

Complex Receptors

Back 14

sense organs, localized collections of cells associated with the special senses (vision, hearing, equilibrium, smell and taste)

Front 15

General Sensory Receptors

Back 15

(simple receptors) respond to tactile sensation, temp, pain and muscle sense

Front 16

Free Dentric Nerve Endings

Back 16

free dendritic endings: everywhere; most abundant in epithelial & connective
tissues
-most are unmyelinated with small diameter (slow)
-respond chiefly to pain & temperature
-examples: Merkel discs in deep skin epidermis & root hair plexuses that
surround hair follicles

Front 17

Tactile Discs (Merkel Discs)

Back 17

Unencapsulated; Exteroceptors; Mechanoreceptors (light pressure); slow adapting; in the basal layer of epidermis

Front 18

Hair Follicle Receptors

Back 18

Free Nerve Endings that wrap basketlike around fair follicles, are light touch receptors that detect bending of hairs.

Front 19

Encapsulated Nerve Endings

Back 19

one or more sensory neuron terminals in
connective tissue capsule; most are mechanoreceptors

Front 20

Meissner’s corpuscles

Back 20

touch receptors in dermal papillae

Front 21

Pacinian corpuscles

Back 21

deep pressure receptors in hypodermis

Front 22

Ruffini’s corpuscles

Back 22

deep, continuous pressure receptors in the dermis,
hypodermis & joint capsules

Front 23

muscle spindles

Back 23

proprioceptors in skeletal muscle perimysium; cause muscle
contraction to counteract stretch

Front 24

Golgi tendon organs

Back 24

proprioceptors in tendons (close to muscle insertion);
cause muscle relaxation (inhibitory to prevent damage due to overstretching)

Front 25

joint kinesthetic receptors

Back 25

proprioceptors within articular capsules in
synovial joints; several receptor types that monitor joint function

Front 26

Somatosensory System

Back 26

Part of the sensory system serving the body wall and limbs. It receives input from exteroceptors, proprioceptors, and interoceptors.

Front 27

Three levels of neural integration operate in the somatosensory system

Back 27

1. Receptor level- sensory receptors
2. Circuit level- ascending pathways
3. Perceptual level- neuronal circuits in the cerebral cortex

Front 28

Processing at Receptor level

Back 28

1. the stimulus energy must match the specifity of the receptor
2. The stimulus must be applied within a sensory receptors receptive field.
3. The stimulus energy must be concerted into the energy of a graded potential called a receptor potential by transduction
4. A generator potential in the associated sensory neuron must reach threshold so that voltage gated sodium channels on the axon are opened and nerve impulses are generated and propagated to the CNS.

Front 29

Adaptation

Back 29

Change in sensitivity in the presence of a constant stimulus

Front 30

Phasic Receptors

Back 30

fast adapting often giving burst of impulses at the beginning and at the end of the stimulus. Act to report changes in the internal or external environment. Ex. pacinian and meissners corp.

Front 31

Tonic Receptors

Back 31

provide a sustained response with little or no adaptation. Nociceptors and proprioceptors are tonic receptors b/c of the protective importance of their info.

Front 32

Circuit Level- The second level of integration:
The Task:

Back 32

Circuit Level- The second level of integration:
The Task:
task is to deliver impulses to the appropriate region of the cerebral cortex for stimulus localization and perception.

Front 33

Ascending Sensory Pathways consist of a chain of 3 neurons...

Back 33

-ascending pathways conduct sensory impulses upward
-first-order neurons: conduct impulses from sensory receptors to brain stem or spinal cord
-second-order neurons: conduct impulses from spinal cord or medullary nuclei to the thalamus or cerebellum
-third-order neurons: conduct impulses from the thalamus to the somatosensory cortex

Front 34

Processing at the Circuit level of Integration:

Back 34

Processing at the Circuit level of Integration:
-The axons of the first-order sensory neurons, whose cell bodies are in the dorsal root or cranial ganglia, link the receptors and circuit levels of processing.
-Central processes of first-order neurons branch diffusely when they enter the spinal cord. Some branches take part in local spinal cord reflexes, and others synapse with second-order sensory neurons which then synapse with the third-order sensory neurons that take the message to the cortex of the cerebrum.

Front 35

Perceptual Level- The third level of integration:
The Task:

Back 35

Perceptual Level- The third level of integration:
The Task:
-The ability to identify and appreciate sensations depends on the specific location of the target neurons in the sensory cortex, not on the nature of the message
-Each sensory fiber is analogous to a labeled line that tells the brain who is calling, a taste bud, or a pressure receptor, and from where.
-The brain always interprets the activity of a specific sensation, no matter how it is activated.

Front 36

Projection in processing at perceptual level:

Back 36

Projection in processing at perceptual level:
-The exact point in the cortex always refers to "where", regardless of how it is activated. This is a phenomenon called projection.

Front 37

Processing at Receptor Level:

Back 37

Processing at Receptor Level:
-Transduction by sensory receptors: a stimulus alters permeability of membrane receptors, leading to a local graded potential or receptor potential (like EPSP)… if the receptor is a separate cell (nonneuron), depolarization is called a generator potential
-If the receptor potential is at or above the threshold, an action potential will be generated & propagated to the CNS
-Adaptation by sensory receptors: some receptors (pressure, touch, smell) become insensitive to the same stimuli over time (don’t notice feel of clothing after some time) while others do not adapt (nociceptors & proprioceptors need to continually react to stimuli)

Front 38

Processing at Circuit Level:
posterior column-medial lemniscus pathway:

Back 38

Processing at Circuit Level:
posterior column-medial lemniscus pathway:
-impulses conveyed to cerebral cortex via posterior column of spinal cord & medial lemniscus of brain stem (relayed by thalamus)
-transmit discriminative touch, pressure, vibration, & conscious proprioception impulses, & also arousal (to RAS)

Front 39

Processing at Circuit Level:
anterolateral (spinothalamic) pathway:

Back 39

anterolateral (spinothalamic) pathway:
-impulses conveyed to cerebral cortex via anterior & lateral spinothalamic tracts within anterior & lateral columns of spinal cord (also relayed by thalamus)
-transmit pain, temperature (lateral) & itch, tickle, pressure & coarse touch (anterior) impulses
-involved with emotional aspects of perception & some higher level motor reflexes (orienting to stimulus)

Front 40

Processing at Circuit Level:
spinocerebellar tracts:

Back 40

spinocerebellar tracts:
-convey information from proprioceptors on one side of the body to the same side of the cerebellum to coordinate skeletal muscle activity (unconscious sensation) & maintain posture & balance

Front 41

Processing at the Perceptual Level:
Perception Involves:

Back 41

Processing at the Perceptual Level:
Perception involves:
awareness of stimuli, their origin & discrimination of their characteristics
• Localization & modality of sensory inputs are begun as tracts reach the thalamus, but most processing occurs in the somatosensory cortex

Front 42

Main aspects of sensory detection:

Back 42

Main aspects of sensory detection:
-perceptual detection
-magnitude estimation
-spatial discrimination
-feature abstraction
-quality discrimination
-pattern recognition

Front 43

Main aspects of sensory detection:
perceptual detection:

Back 43

perceptual detection: detection of stimulus

Front 44

Main aspects of sensory detection:
magnitude estimation:

Back 44

magnitude estimation: how much of the stimulus

Front 45

Main aspects of sensory detection:
spatial discrimination:

Back 45

spatial discrimination: site or pattern of stimulus

Front 46

Main aspects of sensory detection:
feature abstraction:

Back 46

feature abstraction: neuron or circuit is tuned to one feature over others

Front 47

Main aspects of sensory detection:
quality discrimination:

Back 47

quality discrimination: differentiation of submodalities (parts) of sensation

Front 48

Main aspects of sensory detection:
pattern recognition:

Back 48

pattern recognition: find patterns in complex stimuli

Front 49

How are Pain Receptors activated?:

Back 49

How are Pain Receptors activated?:
-by extremed of pressure and temperature as well as a veritable soup of chemicals released from injured tissue.
-Histamine, K+, ATP, acids, and bradykinin are among the most potent pain-producing chemicals.
-All of these chemicals act on small-diamteter fibers

Front 50

When you cut you finger you may notice sharp then burning pain...

Back 50

When you cut you finger you may notice sharp then burning pain...
-Sharp pain is carried by small myelinated A delta fibers, while burning pain is carried more slowly by small un-myelinated C fibers.
-Both types of fibers release the neurotransmitters glutamate and substance P, which activate second-order sensory neurons. Acons from these second-order neurons ascend to the brain via the spinothalamic tract and other aterolateral pathways.

Front 51

If you cut your finger while being attacked, you may not notice the pain...

Back 51

If you cut your finger while being attacked, you may not notice the pain...
-The brain has its own pain-suppressing analgesic systems in which the endogenous opioids (endorphines and enkephalins) play a key role.
-Descending cortical and hypothalamic pain-suppressing signals are relayed through various nuclei in the brain stem including the periaqueductal gray matter of the midbrain.
-Descending fibers activate interneurons in the spinal cord, which release the opioid neurotransmitters called enkephalins. Enkephalins are inhibitory neurotransmitters that quash the pain signals generated by the nociceptive.

Front 52

Nerves & Associated Ganglia:
Nerve:

Back 52

Nerves & Associated Ganglia:
Nerve:
-cordlike organ of PNS consisting of bundles of axons enclosed in layers of connective tissue

Front 53

Nerves & Associated Ganglia:
endoneurium

Back 53

Nerves & Associated Ganglia:
endoneurium:
-each axon enclosed in endoneurium

Front 54

Nerves & Associated Ganglia:
perineurium:

Back 54

perineurium:
-bundles of fibers (fascicles) enclosed in perineurium

Front 55

Nerves & Associated Ganglia:
epineurium

Back 55

epineurium:
-bundles of fascicles enclosed in epineurium

Front 56

Nerves & Associated Ganglia:
sensory (afferent) nerves:

Back 56

sensory (afferent) nerves:
-carry impulses toward CNS

Front 57

Nerves & Associated Ganglia:
motor (efferent) nerves:

Back 57

motor (efferent) nerves:
-carry impulses away from CNS

Front 58

Nerves & Associated Ganglia:
mixed nerves:
contain both sensory & motor fibers (can be somatic &/or autonomic)

Back 58

mixed nerves:
-contain both sensory & motor fibers (can be somatic &/or autonomic)

Front 59

Nerves & Associated Ganglia:
peripheral nerves classified as:

Back 59

peripheral nerves classified as:
-spinal nerves or cranial nerves

Front 60

Nerves & Associated Ganglia:
ganglia:

Back 60

ganglia:
-collections of neuron cell bodies associated with nerves in PNS

Front 61

Regeneration of Nerve Fibers:

Back 61

Regeneration of Nerve Fibers:
-in general, mature neurons are amitotic (do not divide)
-if cell body remains intact, regeneration is possible
-following injury, the two ends of neuron surrounding site of injury seal off & swell from accumulation of materials
-Wallerian degeneration: the axon distal to the site of injury & its myelin sheath begins to disintegrate (debris cleaned up by macrophages & Schwann cells)
-Schwann cells proliferate in response to macrophage signals, & express cell adhesion molecules & release growth factors to stimulate axonal growth... then, they guide axon extensions across the gap (form regeneration tube to bridge gap) & remyelinate the axon
-The greater the distance between broken axon ends, the less the chance of regeneration

Front 62

Cranial Nerves:

Back 62

Cranial Nerves:
-12 pairs
-The first two pairs atttach to the forebrain, and the rest are associated with the brain stem.
-Other than the vagus nerves which extend into the abdomen, cranial nerves serve only head and neck structures.

Front 63

Cranial Nerves:
Olfactory Nerve:

Back 63

I.Olfactory Nerve (cranial nerve I)
: sensory for smell


Front 64

Cranial Nerves:
Optic Nerve

Back 64

II.Optic Nerve (cranial nerve II)
: sensory for vision


Front 65

Cranial Nerves:
Oculomotor Nerve

Back 65

III.Oculomotor Nerve (cranial nerve III)
:
motor for eyeball movement (4 of the 6 extrinsic eye muscles) & upper eyelid movement (sensory for proprioception in extrinsic eye muscles)


Front 66

Cranial Nerves:
Trochlear Nerve

Back 66

IV. Trochlear Nerve (cranial nerve IV)
:
motor for eyeball movement (superior oblique muscle) (sensory for proprioception in superior oblique muscle)

Front 67

Cranial Nerves:
Trigeminal Nerve

Back 67

V. Trigeminal Nerve (cranial nerve V)
:
sensory for touch, pain & thermal sensation in face; motor for chewing


Front 68

Cranial Nerves:
Abducens Nerve

Back 68

VI. Abducens Nerve (cranial nerve VI)
:
motor for eyeball abduction (lateral rectus muscle) (sensory for proprioception in lateral rectus muscle)


Front 69

Cranial Nerves:
Facial Nerve

Back 69

VII. Facial Nerve (cranial nerve VII)
:
sensory for taste (anterior 2/3 of tongue); motor for contraction of facial muscles and activity of lacrimal, nasal, palatine & salivary glands


Front 70

Cranial Nerves:
Vestibulocochlear Nerve

Back 70

VIII. Vestibulocochlear Nerve (cranial nerve VIII)
:
sensory for hearing (cochlear nerve) & equilibrium (vestibular nerve)


Front 71

Cranial Nerves:
Glossopharyngeal Nerve

Back 71

IX. Glossopharyngeal Nerve (cranial nerve IX)
:
sensory for taste (posterior 1/3 of tongue); motor for swallowing (elevation of larynx & pharynx)


Front 72

Cranial Nerves:
Vagus Nerve

Back 72

X. Vagus Nerve (cranial nerve X)
:
-sensory for taste (epiglottis), baroreception & chemoreception in blood vessels, and sensation from thoracic & abdominal organs; motor for regulation of heart rate, breathing, swallowing/speech & digestive system activity


Front 73

Cranial Nerves:
Accessory Nerve

Back 73

XI. Accessory Nerve (cranial nerve XI)
:
-motor for head & neck movement and swallowing (sensory for proprioception in sternocleidomastoid & trapezius muscles)


Front 74

Cranial Nerves:
Hypoglossal Nerve

Back 74

XII. Hypoglossal Nerve (cranial nerve XII)
:
-motor for speech & swallowing (sensory for proprioception in tongue muscles)

Front 75

Easy way to remember the cranial nerves in order:

Back 75

Easy way to remember the cranial nerves in order:
-On Occasion, Our Trusty Truck Acts Funny- Very Good Vehicle Anyhow.

Front 76

Spinal Nerves are formed by...

Back 76

Spinal Nerves are formed by...
-the fusion of ventral (motor) and dorsal (sensory) roots.

Front 77

Cranial Nerves:

Back 77

Cranial Nerves:
-most cranial nerves are mixed nerves
-however, two nerve pairs (the olfactory and optic) associated with special sense organs are generally considered purely sensory.

Front 78

Two Cranial Nerves considered purely sensory...

Back 78

Two Cranial Nerves considered purely sensory...
-Olfactory and Optic
-There cell bodies are located within their respective special sense organs.
-In other cases of sensory neurons contributing to cranial nerves (V<VII< IX< and X), the cell bodies are located in the cranial sensory ganglia just outside the brain.
-Some cranial nerves have a single sensory ganglion, others have several and some have none.

Front 79

Several of the mixed cranial nerves contain both somatic and autonomic motor fibers:

Back 79

Several of the mixed cranial nerves contain both somatic and autonomic motor fibers:
-hence they serve both skeletal muscles and visceral organs.
-Except for some autonomic motor neurons located in ganglia, the cell bodies of motor neurons contributing to the cranial nerves are located in the ventral gray matter regions ( nuclei) of the brain stem.

Front 80

How many pairs of Spinal Nerves?:

Back 80

How many pairs of Spinal Nerves?:
31 pairs
-8 pairs of cervical
-12 pairs of thoracic
-5 pairs of lumbar
-5 pairs of sacral
-1 pair of coccygeal

Front 81

Spinal Nerves:
ventral roots:

Back 81

Spinal Nerves:
ventral roots:
-contain motor (efferent) fibers arising from the anterior horn & extending to skeletal muscle fibers

Front 82

Spinal Nerves:
dorsal roots:

Back 82

Spinal Nerves:
dorsal roots:
contain sensory (afferent) fibers arising from sensory neurons in the dorsal root ganglia; conduct impulses from sensory receptors to spinal cord
-spinal nerves are short (1-2 cm); branch into smaller dorsal ramus, larger ventral ramus & tiny meningeal branch to meninges & blood vessels
-thoracic spinal nerves have rami communicantes with autonomic (visceral) fibers

Front 83

Spinal Nerves:
dermatomes:

Back 83

dermatomes:
-areas of skin innervated by individual spinal nerves

Front 84

Spinal Nerves:
Hilton’s Law:

Back 84

Hilton’s Law:
-any nerve serving a muscle that produces movement at a joint also innervates the joint & the skin over the joint

Front 85

Innervation of Specific Body Regions:

Back 85

Innervation of Specific Body Regions:
-The spinal nerve rami and their main branches supply the entire somatic region of the body (skeletal muscles and skin) from the neck down.
-The dorsal rami supply the posterior body trunk.
-The thicker ventral rami supply the rest of the trunk and the limbs.

Front 86

Innervation of Specific Body Regions:
Difference b/w Roots and Rami:

Back 86

Innervation of Specific Body Regions:
Difference b/w Roots and Rami:
-Roots lie medial to and form the spinal nerves, and each root is strictly sensory or motor.
-Rami lie distal to and are lateral branches of the spinal nerves and, like spinal nerves, carry both sensory and motor fibers.

Front 87

Innervation of Specific Body Regions:
Ventral Rami of the Spinal Nerves:

Back 87

Innervation of Specific Body Regions:
Ventral Rami of the Spinal Nerves:
-Except for T2-T12, all ventral rami branch and joint one another lateral to the vertebral column, forming complicated interlacing nerve networks called nerve plexuses.

Front 88

Innervation of Specific Body Regions:
Nerve Plexuses:

Back 88

Innervation of Specific Body Regions:
Nerve Plexuses:
-interlacing nerve networks (lateral to spinal cord) from ventral rami of groups of spinal nerves serving similar body regions
- muscles of the anterolateral thorax & abdominal wall served by spinal nerves T1-T12 as intercostal nerves, with cutaneous branches to skin

Front 89

Innervation of Specific Body Regions:
cervical plexus:

Back 89

Innervation of Specific Body Regions:
cervical plexus:
-spinal nerves C1-C5; supplies skin & muscles of head, neck & superior part of shoulders & chest
-phrenic nerve: serves diaphragm for breathing

Front 90

Innervation of Specific Body Regions:
brachial plexus:

Back 90

Innervation of Specific Body Regions:
brachial plexus:
spinal nerves C5-T1; supplies shoulders & upper limbs
-branches: roots (ventral rami of C5-T1), trunks (upper, middle, lower), divisions (anterior & posterior) & cords (lateral, medial & posterior)
-nerves: musculocutaneous, median, ulnar, radial & axillary

Front 91

Innervation of Specific Body Regions:
lumbar plexus:

Back 91

Innervation of Specific Body Regions:
- lumbosacral plexus: lower limb; branches to pelvis, abdomen & buttocks
lumbar plexus:
spinal nerves L1-L4; supplies anterior abdominal wall, external genitals & part of lower limbs
-femoral nerve: serves muscles of anterior upper leg (quadriceps) & skin of anterior & medial lower leg
-obturator nerve: serves adductor muscles of medial thigh

Front 92

Innervation of Specific Body Regions:
sacral plexus:

Back 92

Innervation of Specific Body Regions:
sacral plexus:
-spinal nerves L4-S4; supplies buttocks, perineum & lower limbs
-sciatic nerve: serves entire leg except anteromedial thigh (longest & thickest nerve in body); branches to tibial & common fibular nerves just above knee

Front 93

Innervation of Specific Body Regions:
coccygeal plexus:

Back 93

Innervation of Specific Body Regions:
coccygeal plexus:
-spinal nerves S4-Co; supplies small area of skin in coccygeal region

Front 94

Innervation of Specific Body Regions:
Back:

Back 94

Innervation of Specific Body Regions:
Back:
-following neat, segmented plan, Via its several branches, each dorsal ramus innervates the narrow strip of muscl and skin in line with its emergence point from the spinal column.

Front 95

Innervation of Specific Body Regions:
Anterolateral Thorax and Abdominal Wall:

Back 95

Innervation of Specific Body Regions:
Anterolateral Thorax and Abdominal Wall:
-Only in the thorax are the ventral rami arranged in a simple segmental pattern corresponding to that of the dorsal rami.
-Intercostal nerves- the ventral rami od T1-T12 mostly course anteriorly, deep to each rib, as the intercostal nerves. Along their course, these nerves give off cutaneous branches to the skin.
-Subcostal Nerve- Two thoracic nerves are unusual: the tiny T1 and T12, which lies inferior to the twelfth rib, making it a subcostal nerve.
-The intercostal nerves and their branches supply the intercostal muscles lying between the ribs, the muscle and skin of the anterolateral thorax, and most of the abdominal wall.

Front 96

Innervation of Specific Body Regions:
Cervical Plexus and Neck:

Back 96

Innervation of Specific Body Regions:
Cervical Plexus and Neck:
- buried deep in the neck under the sternocleidomastoid muscle, the looping cervical plexus is formed by the ventral rami of the first four cervical nerves.
-most branches are cutaneous nerves that supply only skin.
-They transmit sensory impulses from the skin of the neck, the ear, the back of the head, and the shoulder. Other branches innervate muscles of the anterior neck.
-Phrenic Nerve- receives fibers from C3-C5. runs inferiorly through the thorax and supplies both motor and sensory fibers to the diaphragm.

Front 97

Innervation of Specific Body Regions:
Brachial Plexus and Upper Limb:

Back 97

Innervation of Specific Body Regions:
Brachial Plexus and Upper Limb:
-partly in neck and partly in axilla.
-give rise to almost all the nerves that innervate the upper limb.
-formed by intermixing of ventral rami od C5-C8 and most of the T1 ramus.
-It often receives fibers from C4, T2 or both.

Front 98

Innervation of Specific Body Regions:
4 major groups of branches in Brachial Plexus:

Back 98

Innervation of Specific Body Regions:
4 major groups of branches in Brachial Plexus:
-"Really Tired? Drink Coffee"
-From medial to lateral,
1. the ventral rami misleadingly called roots;
2. trunks, which form;
3. divisions, which form;
4. cords.

Front 99

Innervation of Specific Body Regions:
The five roots of the brachial plexus...

Back 99

Innervation of Specific Body Regions:
The five roots of the brachial plexus...
-lie deep to the sternocleidomastoid muscle. At the lateral border of that muscle, the roots unite to form upper, middle and lower trunks, each of which divides almost immediately into an anterior and posterior division.
-These divisions which generally indicate which fibers serve the front or back of the limb, pass deep to the clavicle and enter the acilla, where they give rise to three large fiber bundles called the lateral medical and posterior cords.

Front 100

Innervation of Specific Body Regions:
axillary nerve:

Back 100

Innervation of Specific Body Regions:
axillary nerve:
- branch off the posterior cord and runs posterior to the surgical neck of the humerus. It innervates the deltoid and teres minor muscles and the skin and joint capsule.

Front 101

Innervation of Specific Body Regions:
musculocutaneous nerve:

Back 101

Innervation of Specific Body Regions:
musculocutaneous nerve:
-the major end branch of the lateral cord, courses inferiorly in the anterior arm, supplying motor fibers to the biceps brachii and brachialis muscles. Distal to the elbow, it provides for cutaneous sensation of the lateral forearm.

Front 102

Innervation of Specific Body Regions:
Median Nerve:

Back 102

Innervation of Specific Body Regions:
Median Nerve:
-descends through the arm to the anterior forearm, where it gives off branches to the skin and to most flexor muscles. On reaching the hand, it innervates five intrinsic muscles of the lateral palm. The median nerve activates muscles that pronate the forearm, flex the wrist and fingers, and oppose the thumb.

Front 103

Innervation of Specific Body Regions:
Ulnar Nerve:

Back 103

Innervation of Specific Body Regions:
Ulnar Nerve:
-branches off the medial cord of the plexus. Descends along...p.505

Front 104

Innervation of Specific Body Regions:
Ulnar Nerve:
Radial Nerve:

Back 104

Innervation of Specific Body Regions:
Ulnar Nerve:
Radial Nerve:
p. 505

Front 105

Somatic Motor Pathways:
Levels of Motor Control:

Back 105

Somatic Motor Pathways:
Levels of Motor Control:
-some lower-level motor control is mediated by reflex arcs, but complex motor activities appear to be regulated by fixed-action patterns (stereotyped sequential motor actions triggered internally or by environmental stimuli)

Front 106

Somatic Motor Pathways:
Levels of Motor Control:
Segmental level:

Back 106

Somatic Motor Pathways:
Levels of Motor Control:
Segmental level:
-segmental circuits of spinal cord
-Segmental circuits activate anterior horn segments of the spinal cord to stimulate a specific group of muscle fibers
-Circuits controlling locomotion & common motor activity are called central pattern generators (CPGs)

Front 107

Somatic Motor Pathways:
Levels of Motor Control:
Projection level:

Back 107

Somatic Motor Pathways:
Levels of Motor Control:
Projection level:
cortical motor areas that produce the direct (pyramidal) system & indirect (extrapyramidal or multineuronal) system.
-axons of the neurons at this level project to the spinal cord & help control both reflex & fixed-action pattern activities, and produce voluntary movement

Front 108

Somatic Motor Pathways:
Levels of Motor Control:
Programs & Instructions Level:

Back 108

Somatic Motor Pathways:
Levels of Motor Control:
Programs & Instructions Level:
-neurons in the basal nuclei of the cerebrum and of the cerebellum (precommand areas) that regulate motor activity
-Involved in starting & stopping movements, coordinating movements with posture, blocking unwanted movements & maintaining muscle tone

Front 109

Somatic Motor Pathways:
Cerebellum:

Back 109

Somatic Motor Pathways:
Cerebellum:
center for sensorimotor integration & control, correcting errors in muscle activity, & fine-tuning motor activity
-damage to the cerebellum results in disorders of synergy & muscle tone, disturbances of equilibrium & speech disorders

Front 110

Somatic Motor Pathways:
Basal Nuceli:

Back 110

Somatic Motor Pathways:
Basal nuclei:
-receive inputs from all cortical areas & send output to the premotor & prefrontal cortex to coordinate more complex motor activities

Front 111

Organization of Upper Motor Neuron Pathways:
cortical motor areas:

Back 111

Organization of Upper Motor Neuron Pathways:
cortical motor areas:
-that produce the direct (pyramidal) system & indirect (extrapyramidal or multineuronal) system

Front 112

Organization of Upper Motor Neuron Pathways:

Back 112

Organization of Upper Motor Neuron Pathways:

Front 113

Organization of Upper Motor Neuron Pathways:
Direct Motor Pathways:

Back 113

Organization of Upper Motor Neuron Pathways:
Direct Motor Pathways:
-lateral corticospinal tracts: conveys nerve impulses from motor cortex to skeletal muscles on opposite side of the body for precise, voluntary movements of hands & limbs
-anterior corticospinal tracts: conveys nerve impulses from motor cortex to skeletal muscles on opposite side of the body for movements of axial skeleton
-corticobulbar tracts: conveys nerve impulses from motor cortex to skeletal muscles of the head & neck for precise, voluntary movements

Front 114

Organization of Upper Motor Neuron Pathways:
Indirect (extrapyramidal) tracts:

Back 114

Organization of Upper Motor Neuron Pathways:
Indirect (extrapyramidal) tracts:
-all somatic motor tracts other than direct motor pathways
-axons of UMN that carry impulses from indirect pathways descend from various nuclei of the brain stem into 5 major tracts of spinal cord & terminate on local circuit neurons or LMNs
-rubrospinal, tectospinal, vestibulospinal, lateral & medial reticulospinal tracts

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Reflexes:

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Reflexes:
-somatic reflexes: lead to contraction of skeletal muscles
-autonomic (visceral) reflexes: lead to responses from smooth muscle, cardiac muscle & glands

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Reflex Arc:

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Reflex arc:
-sensory receptor:
-sensory neuron:
-integration center:
-motor neuron:
-effector:
-general reflex types:
-omonosynaptic reflex:
-polysynaptic reflex:
-ipsalateral reflex:
-contralateral reflex:

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Reflex arc:
sensory receptor:

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Reflex arc:
sensory receptor:
distal end of sensory neuron; responds to stimulus

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Reflex arc:
sensory neuron:

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Reflex arc:
sensory neuron:
-carries impulse from receptor to axon terminals in gray matter of spinal cord (or brain stem)

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Reflex arc:
integration center:

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Reflex arc:
integration center:
within CNS gray matter, signal travels across synapse or through interneuron, generating a response

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Reflex arc:
motor neuron:

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Reflex arc:
motor neuron:
-response impulse is sent from sensory neuron or interneuron through motor neuron to effector

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Reflex arc:
effector:

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Reflex arc:
effector:
-muscle or gland that carries out response (reflex)

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Reflex Arc:
general reflex types:

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Reflex Arc:
general reflex types:
-monosynaptic reflex: involves only 2 neurons (sensory & motor) & one synapse
-polysynaptic reflex: involves more than 2 neurons (sensory, motor & interneurons) & more than one synapse
-ipsalateral reflex: sensory neurons enter & motor neurons exit spinal cord on same side
-contralateral reflex: sensory neurons enter & motor neurons exit spinal cord on opposite sides

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somatic spinal reflexes:
stretch reflex:

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somatic spinal reflexes:
-stretch reflex:
-causes contraction of skeletal muscle in response to muscle stretching
-sensory receptors are muscle spindles

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somatic spinal reflexes:
tendon reflex:

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somatic spinal reflexes:
tendon reflex:
-causes muscle relaxation in response to increasing muscle tension (to prevent tendons from tearing)
-sensory receptors are (Golgi) tendon organs

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somatic spinal reflexes:
flexor (withdrawal) reflex:

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somatic spinal reflexes:
flexor (withdrawal) reflex:
-causes muscle contraction to move body region away from painful stimulus
-plantar flexion reflex: curling under of toes in response to stimulation of lateral outer margin of toe
-damage to descending motor pathways causes great toe extension (Babinski sign), although a normal response in infants

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somatic spinal reflexes:
crossed extensor reflex:

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somatic spinal reflexes:
crossed extensor reflex:
-works with withdrawal reflex to maintain balance
-contraction of extensors on opposite side of body to compensate for withdrawal (contralateral reflex)

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What information does your nervous system need in order to smoothly coordinate the activity of your skeletal muscles?

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What information does your nervous system need in order to smoothly coordinate the activity of your skeletal muscles?
-Two types of info about the current state of a muscle are key.
-First, the nervous sustem needs to know the length of the muscle. The muscle spindles found in the skeletal muscles supply this info.
-Second, it needs to know the amount of tension in the muscle and its associated tendons. Golgi tendon organs provide this info.

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Functional Anatomy of Muscle Spindles:

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Functional Anatomy of Muscle Spindles:
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