The Peripheral Nervous System

Front 1

What is sensation?

Back 1

awareness, either a subconscious or conscious level, of a stimulus

Front 2

What is the difference b/w sensation and perception?

Back 2

Perception is a conscious interpretation of stimuli
Sensation is the awareness of a stimuli; can be unconscious or conscious

Front 3

Name and describe the four events required to produce sensation.

Back 3

Stimulation - Change in the body's environment that can activate the receptor
Transduction - sense receptor/organ converts stimulus energy to electrical energy
Impulse generation and propagation - threshold simulus causes AP in 1st order sensory neuron to CNS; strength encoded in freqnency of AP
Integration - in CNS; conscious must be in cerebral cortex; interprets frequency as strength; single region get imput from parallel circuits; number of receptors that are firing

Front 4

Describe the energy conversion that occurs in transduction.

Back 4

- Production of receptor/graded porential en terminal endings of sensory neuron
- depolarizations summate and lead to AP in afferant fiber called generator potentials (either hyper for light or de- for all other senses; polarization)
Generator potential causes AP at 1st node of ranvier/trigger zone
Receptor cell separate from afferent neuron - receptor potential causes receptor cell to change rate of NT release, results in generator potential in afferent neuron and maybe an AP if strong enough

Front 5

What is a receptor potential? a generator potential?

Back 5

Receptor - graded; in terminal endings of sensory neuron; caused by stimulus
Generator - membrane depolarizations that summate and directly lead to generation of APs in afferant fiber
If the receptor cell is separate from afferent neuron then generator does not equal receptor
If receptor cell isn't separate from afferent neuron, then receptor potential is the same thing as a generator potential

Front 6

What is sensory adaptation?

Back 6

- Decreased sensitivity during a long-lasting and unchanging stimulus; can occur at sensory receptor level and at integration level in CNS

Front 7

What is the difference b/w phasic and tonic receptors?

Back 7

Phasic (fast acting) - prolonged/unchanged stimulus = brief response then stop; pressure, touch, smell
Tonic (slow adapting) - repetitive discharge of APs in response to unchanging stimulus; pain, body position, blood pressure, etc

Front 8

Identify and describe the three basic levels of neural integration.

Back 8

Receptor level - sensory reception and transmission to CNS; receptor specificity, receptor field, receptor potential to AP in 1st order neuron
Circuit level - processing in ascending pathways; 1st order sensory neuron; to thalamus; collaterals send input to nuclei in ret. formation
Perceptual level - processing in cortical sensory centers; thalamus relays info to cerebral cortex via 3rd order sensory neurons

Front 9

What types of simuli are received and transduced by each of the following types of receptors: mechanoreceptors, thermoreceptors, nociceptors... to be continued on other card

Back 9

Mechanoreceptors - mech pressure or stretching and vitration; proprioceptors, hearing, equilibrium, BP, digestive tract, bladder, visceral walls and body surface
Thermoreceptors - change in temp; free nerve endings; hot or cold; warm in dermis, cold receptors in stratum basale of epidermis; hypothalamus region
Nociceptors - simuli that could cause mech or chem damage to tissues; all tissues except brain; more numerous in epithelial and CT;

Front 10

What types of simuli are received and transduced by each of the following types of receptors: Photoreceptors, chemoreceptors

Back 10

Photoreceptors - light energy; only found in retina of eyes
Chemoreceptors - chemicals in solution; smell, taste, body fluid chemistry; detect desolved chem.

Front 11

Describe the location and stimulus selectivity of exteroceptors, interoceptors and proprioceptors.

Back 11

Exteroceptors - near body surface; for external stimuli; ex. cutaneous receptors and special senses
Interoceptors - in walls of viscera and blood vessels; internal stimuli
Proprioceptors - skeletal muscles, tendons, joints, ligaments and CT coverings of bones and muscles (endomysia), vestibular apparatus; body position, muscle tension, joint position, joint movement; skeletal muscle function sometimes equilibrium receptors (depends on anatomist)

Front 12

Identify and describe the main difference b/w the two subcategories of simple receptors.

Back 12

Free dendritic endings - abundant in ET and CT, but all over body; small diameter, unmyelinated, end in knob like swellings; pain and temp mostly, some also touch
Encapsulated dendritic endings - 1+ nerve fivers enclosed in CT capsule

Front 13

Name the types of encapsulated dendritic endings.

Back 13

Meissner's corpuscles (tactile corpuscles)
Krause's end bulbs
Pacinian corpuscles (lamellated corpuscles)
Ruffini's corpuscles
Muscle spindles
Golgi tendon organ (GTO)
Joint Kinesthetic receptor

Front 14

What is the function of free dendritic nerve endings? In what tissues is this type of receptor especially abundant?

Back 14

- pain and temp mostly, some also touch (mech press)
- all over body, but esp in CT and ET

Front 15

Identify and describe two specialized types of free dendritic endings.

Back 15

Merkel discs/tactile discs/type 1 cutaneous mechanoreceptors - in dermis, near jct. of dermis and epidermis; associated w/merkel cells in stratum basale; esp in fingertips, hand, lips, external genetalia; flattened disk shaped enlargement at terminal end; slow-adapting; light touch receptor
Root hair plexuses/hair follicle receptors - wrappings spiral around hair follicle; when hair follicle is bent; light touch receptor; fast adapting

Front 16

Locate and describe the structure and function of the encapsulated dendritic endings: Meissner's corpuscles (tactile corpuscles), Krause's end bulbs...

Back 16

Meissner's corpuscles - in dermal papillae, esp hairless skin (hands, penis, clitoris, eyelids, tip of toungue, feet); dendrite ends branched and spiraling; surrounded by schwann cell which is surrounded by CT capsule; rapidly adapring light touch receptor; onset of touch; mechanoreceptor; similar role to root hair plexus
Krause's end bulbs - mechanoreceptors; in mucous membranes; lining of mouth and digestive tract

Front 17

Locate and describe the structure and function of the encapsulated dendritic endings: Pacinian corpuscles (lamellated corpuscles), Ruffini's corpuscles...

Back 17

Pacinian corpuscles - single dendrite surrounded by many layers of flattened schwann cells and enclosed in CT capsule; can be very large; rapidly adapring mechanoreceptor; deep pressure and stretch; deep in dermis and subcutaneous tissue; senses vibrations
Ruffini's corpuscles - spray of dendritic endings enclosed by flattened capsule; in subcutaneous tissue, joint capsules, tendons, ligaments, soles of feet, palm of hands; tonic receptors adapt little if at all; deep and continuous pressure

Front 18

Locate and describe the structure and function of the encapsulated dendritic endings: muscle spindles, Golgi tendon organ (GTO), Joint kinesthetic receptors...

Back 18

Muscle spindles - all skeletal muscles, esp for fine motor control
Golgi tendon organ (GTO) - proprioceptors in tendons of skeletal muscle; close to where tendon ends and muscle begins; reflex action
Joint kinesthetic receptors - proprioceptors; stretch w/in and around articular capsules of synnovial joints; joint position and movement; ruffini's and pascinian corpuscles and free endings all contribute as well

Front 19

Where does somatic pain arise? Where does visceral pain arise?

Back 19

Somatic - skin, joints and muscles
Visceral - stimulation of nociceptors in walls of organs of the ventral body cavity (dull throbbing pain); triggered by ischemia (no O2), extreme stretching, irritating chem, muscle spasms

Front 20

Identify and contrast the 2 classifications of somatic pain.

Back 20

Superficial somatic pain - type A
Transmited along A fibers, largest, but only lightly myelinated; acute, sharp, not long lasting, more precise and localized
Deep somatic pain - deep in skin, muscles, joints; C fibers (small diameter, unmyelinated), burning itching aching pain, more diffuse, always indicates significant tissue damage

Front 21

Distinguish between pain threshold and pain tolerance.

Back 21

Pain threshold - all have the same; precise mV level at which receptor is activated, perceived at same degree (heat, it's 44-46 C)
Pain tolerance - varies, can be modified day to day; enough sleep, chronic pain being experienced, cultural factors, etc.

Front 22

Identify and describe the connective tissue sheaths which are associated with a nerve.

Back 22

axon myelinated or unmyelinated
Endoneurium - wraps individual fibers; made of areolar CT
Perineurium - bundles fibers into fasicles; encloses the fascicle
Epineurium - wraps entire nerve; fuses with dura mater as spinal nerves pass through intervertebral foramen

Front 23

What is a mixed nerve?

Back 23

Contains both sensory and motor fibers

Front 24

How are spinal nerves named and numbered?

Back 24

- Numbers to up as you go anterior to posterior and up as you go from medial to lateral
- Name - comes generally for the area of the body that they innervate

Front 25

What type of fibers is present in the dorsal root?

Back 25

sensory nerve fibers
Impulses from periphery to the cord

Front 26

What type of fibers is present in the ventral root?

Back 26

motor fibers
From the CNS out

Front 27

Name and identify the general function of each of the initial three branches of a spinal nerve.

Back 27

Dorsal rami - muscles and skin of posterior part of trunk
Ventral rami - intercolstal nerves (T1-T12); lateral and anterior wall of torso; subcostal nerves; interior and deep to ribs
Meningeal rami - re-enters vertebral canal; innervates blood vessels and meninges

Front 28

Explain the difference b/w in the roots and rami associated with the spinal cord.

Back 28

Roots - medial to spinal nerves; either motor or sensory
Rami - distal to (and are lateral branches of) spinal nerves; mixed in function

Front 29

How is the dorsal trunk innervated?

Back 29

Dorsal rami in a segmented way

Front 30

How are the anterolateral thorax and abdominal wall innervated?

Back 30

Ventral Rami - T1-T12; intercostal nerves; inferior and deep to ribs; supply muscles and skin of abdominal wall and anterolateral thoracic region
T12 = subcostal nverbe
Segmented innervation

Front 31

What spinal nerve branches from the intercostal nerves?

Back 31

T1-T12 = intercostal nerves
T12 = subcostal nerve
segmented innervation

Front 32

What spinal nerve fibers form the various nerve plexuses?

Back 32

All of ventral rami except T1-T12
4 main plexuses
Intermingled fibers give rise to peripheral nerves
Cervical - C1-C5
Brachail - C5-C8
Lumbar - L1-L4
Sacral - L5?-S4

Front 33

What is a dermatome?

Back 33

- Skin segment with sensory innervation supplied by fibers of a single pair of spinal nerves; all spinal nerves except C1 participate
Crainal nerve V spuuplies sensory innervation to skin of face and anterior scalp (only place not innervated by spinal nerve)

Front 34

Identify the three levels in the hierarchy of motor control and describe the activities performed at each.

Back 34

Segmental level - lower circuite neurons in spinal cord and brain stem; excitatory/inhibitory input from somatic sensory, basal ganglia; involved w/ frequencly executed activities like walking (central pattern generators)
Projection level - oversight to local circuits and LMNs; upper motor neurons in primary motor cortex (pyramidal system) or motor nuclei in brain stem (red nuclei, vestibular, reticular formations, etc); provides continual internal feedback to higher levels; synapse w/interneurons mostly and lower motor neurons
Precommand level - basal nuclei and cerebellum - input sent to Upper Motor Neurons; basal nuclei and cerebellum make it up; coordinates movements; advance planning for voluntary movement; initiate and terminate movements; muscle tone, feedback
Above this level is the primary motor cortex

Front 35

What parts of the CNS are associated with each level of the motor control hierarchy?

Back 35

Segmental level - local circuit neurons
Projections level - upper motor neurons in primary motor cortex (pyramidal system) or motor nuclei in brain stem (red nuclei, vestibular, ret. formation, etc)
Precommand level - Basal nuclei and cerebellum; send input to upper motor neurons

Front 36

Describe the difference b/w a reflex and a reflex arc.

Back 36

Reflex - rapid, automatic response to specific (threshold) stimuli; predictable response
Reflex arc - specific neural pathways/circuits involved in producing reflex behavior; not predictable in the same way

Front 37

What are the five components of all reflex arcs?

Back 37

- Receptor - responds to stimulus, must be threshold, produces generator response which creates AP
- Sensory neuron - nerve fiber; sensory impulse to CNS
Integration center - typically but not always, CNS; single synapse (monosynaptic reflex) or multiple (polysynaptic reflex) with an interneuron
- Motor neuron - nerve fiber conducts motor impulse from integration center to effector
- Effector - muscle or gland that responds to impulse
Reflex may be innate or acquired

Front 38

Where is the integration center for the reflex arc always located?

Back 38

CNS

Front 39

Identify and describe the two functional types of reflex.

Back 39

Somatic reflexes - activate skeletal muscles
Autonomic/visceral reflexes - activate smooth or cardiac muscle or glands

Front 40

Describe the structure and function of the muscle spindle.

Back 40

Complex receptor; encapsulated in CT capsule, not cutaneous, proprioceptor in perimysia of muscles
- bundle of modified skeletal muscle fibers (intrafusal fibers - shorter, smaller, less actin and myosin, no sarcomeres)
Innervation: sensory - single type Ia afferent ends in primary sensory endings that spiral around intrafusal fibers at their center; respond to length/strech and rate of change in muscle. several type II afferents respond to length/stretch, but not the rate
motor: alpha motor fibers - innervate extrafusal fibers of muscle itself, not muscle spindle; gamma efferent fibers innervate intrafusal fibers in contracting regions at each end of spindle; so spindle shortens and stays proportional to extrafusal fibers of muscle

Front 41

Intrafusal fibers

Back 41

bundle of modified skeletal muscle fibers enclosed in CT capsule; shorter, smaller diameter, less myosin and actin, no sarcomeres
Part of Muscle spindle

Front 42

Extrafusal fibers

Back 42

contractile fibers of the muscle

Front 43

Alpha motor fiber

Back 43

innervates extrafusal fibers (contracting fibers of muscle)

Front 44

Gamma motor fiber

Back 44

Innervates ends of intrafusal fibers in contracting regions of muscle spindle
Activated - causes muscle spindle to contract; so it stays proportional to extrafusal fibers; so it can still tell what's going on in the muscle and be effective

Front 45

What is the function of alpha motor efferents? Of gamma motor efferents?

Back 45

alpha - innervates extrafusal fibers (contracting fibers of muscle)
Gamma - Innervates ends of intrafusal fibers in contracting regions of muscle spindle
Activated - causes muscle spindle to contract; so it stays proportional to extrafusal fibers; so it can still tell what's going on in the muscle and be effective

Front 46

Describe the function of the primary sensory ending of the muscle spindle.

Back 46

Single type Ia afferent fiber
Responds to both length/stretch and rate of change in muscle
Part of the stretch reflex - stretching a muscle causes a reflexive contraction in the muscle

Front 47

Identify the sensory receptor thought to be involved in the deep tendon reflex arc.

Back 47

this reflex resuslts in muscle relaxation/lengthening in response to increased tension
- Involves Golgi Tendon Organ (GTO)

Front 48

Which of the reflexes, the stretch reflex and the deep tendon reflex, is monosynaptic? Which is polysynaptic?

Back 48

- Deep tendon reflex- Golgi tendon organ - polysynaptic
- Stretch reflex - muscle spindle - monosynaptic reflex

Front 49

Describe the phenomenon of reciprocal action.

Back 49

- Part of the deep-tendon reflex
- where the antatonist is stimulated to contract as well; big in preventing damage in tendons; coordination and smoothness;
- Quads contract, GTOs activated; afferent fibers synapse w/interneurons; efferent to antagonist makes it contract (this is reciprocal action), and efferent to agonist muscles is dampened so it relaxes (but not part of reciprocal action)

Front 50

Define visceral reflex.

Back 50

Sensory arm (visceral sensory neuron)- integration center - motor output/efferent pathway - visceral effector (smooth muscle, cardiac muscle, glands)
Still will have the five parts of a reflex arc

Front 51

Compare and contrast long visceral reflexes versus short visceral reflexes.

Back 51

Long reflex - integration center in CNS, focus on the health of the organism, at the expense of the organ
Short Reflex - in autonomic ganglion, focus on the health of the organ

Front 52

Describe a deep tendon reflex.

Back 52

Polysynaptic reflex results in muscle lengthening in response to increased tension in muscle
- Involves Golgi tendon organ - a proprioceptor located in the tendons; stimulated by increased tension in tendon; inhibit contraction in belly of muscle when stimulated; involved in reciprocal action, where the antagonist is simultaniously stimulated to contract

Front 53

Describe the stretch reflex and the deep tendon reflex. Be sure to include all five components of the reflex arc in your description.

Back 53

Receptor, sensory neuron, integration center, motor neuron, effector
Receptor (primary sensory endings/muscle spindle for stretch reflex and golgi tendon organs for deep tendon reflex
Sensory neuron, synapses with interneurons, efferent to the muscle, which makes the muscle either contract or not contract - see p 169 and 170

Front 54

Hilton's Law

Back 54

The principle that the nerve supplying a joint also supplies both the muscles that move the joint and the skin covering the articular insertion of those muscles

Front 55

How will you remember what nerve supplies each synovial joint?

Back 55

Hilton's law - The principle that the nerve supplying a joint also supplies both the muscles that move the joint and the skin covering the articular insertion of those muscles

Front 56

Transduction

Back 56

Process by which a sense receptor/organ converts stimulus energy to electrical energy
Environmental stimulus to altered membrane conductance to altered membrane potential to receptor potential