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Anatomy Muscles > Ch 13 PNS > Flashcards

Ch 13 PNS Flashcards

1
Q

Purpose of Pns

A

Provides links from and to world outside body

All neutral structure outside brain
Sensory receptors
Peripheral receptors
Efferent motor ending

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2
Q

What are sensory receptors?

A

Specialized to respond to changes in the environment ( stimuli )
Activation results in graded potentials that trigger nerve impulses

Sensation ( awareness of stimulus )
Perception ( interpretation of meaning of stimulus) occur in the brain

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3
Q

Classifications of receptors

A

The type of stimulus they detect
Location in body
Structural complexity

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4
Q

Classification of stimulus type

A

Menchanoreceptors- respond to touch, pressure, vibration and stretch

Themoreceptore- sensitive to change in temp
Photoreceptors- respond to light energy
Chemoreceptors- responds to chem ( taste , smell )
Nociceptors - sensitive to pain

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5
Q

Classifications by location

A

Exteroceptors:
Respond to stimuli arising outside body
Receptors in the skin for touch, pressure, pain and temperature

Most special sense organs

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6
Q

Classifications by locations

A

Interceptors ( visceoroceptors )
Sensitive to chemical changes and sometimes cause discomfort

Proprioceptors : respond to stretch in skeletal muscle , inform brain of ones movement

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7
Q

Classifications by receptors structure

A

Simple receptors for general sense :
Tactile receptors ( touch pressure stretch
Modified dendritic ending of sensory neurons

Receptors for special sense :
Vision hearing equilibrium, smell and taste

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8
Q

Senses : non encapsulated or encapsulated

A

Non encapsulated( free) nerve endings
Abundant in epithelial and ct
Most nonmyelinated, small diameter fibers
Respond mostly to temp and pain , and some pressure movements (itch)

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9
Q

Simple receptors of general sense

A

Thermoreceporys
Cold ( 10-40) in superficial Dermis
Heat receptors ( 32-48) in deeper dermis

Outside those temperatures range- nociceptors activated pain

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10
Q

Unencapsukated dentritic endings

A

Nociceptors
Player in detection-
Ion channel opened by heat , low ph chem eg

Respond to : pinching, chemicals from damage tissues, capsaicin

Other light touch receptors
Tactile ( Markell) docs
Hair follicle receptors

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11
Q

Encapsulated dendritic endings

A

All mechanoreceptors in ct capsule
Tactile ( meissner’) corpuscles discriminative touch
Lamellar ( pacinian) corpuscles- deep pressure and vibration
Bulbous corpuscles ( riffini endings ) deep continuous tissue

Muscle spindles- muscle stretch
Tendon organs- stretch in tendons
Joint kinesthtic receptors- joint position and motion

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12
Q

Sensory integration

A

Somatosensoru system - part of sensory system serving body wall and limb

Receives input from
Exteroceptors , proprioceptors and interceptors

Input relayed towards head, but processed along way

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13
Q

Sensory integration continues

A

Levels of neural integration in sensory systems:
Receptors level - sensory receptors
Circuit level - processing in ascending pathways
Perceptual level - processing’s in cortical sensory areas

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14
Q

Processing’s at receptor level

A

To produce a sensation:
Receptors have specificity for stimulus energy
Stimulus must be applied in receptive field
Transduction occurs
Stimulus change to garage potential
Generator potential or receptor potential

Grades potentials must reach threshold ap

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15
Q

Continue…

A

Grades potential called generator potential
Stimulus
Generator potential in after repair neuron
Action potential

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16
Q

Adaptation of sensory receptors

A

Is change in sensitivity in presence of constant stimulus

Receptors membranes become less responsive
Receptor potential risk decline I. Frequency or stop

17
Q

Professing at circuit level

A

Pathways of 3 neurons conduct sensory impulses upward to appropriate cortical regions
First order : conduct impulses from receptors level to spinal reflexes
Second order: transmit impulses to 3rd order sensory neurons

3rd order sensory : conduct impulses from thalamus to the somatosensory cortex

18
Q

Structure of a nerve

A

Cordlike organ of pns budge of myelinated and no myelinated peripheral axons enclosed by ct

Ct covering:
Endometrium - loose ct that encloses axons and their myelin sheaths
Perineurim: coarse cr that bundles fibers into fascicles
Epineurium- tough fibrous stealth around nerve

19
Q

Classifications of nerve

Most are mixed

A

Classified according to direction transmit impulses
Mixed nerves - both sensory and motor fibers : impulses both to and from cns sensory ( afferenr) nerves - impulses only towards cns
Motor ( effenent) nerves - impulses only away from cns

20
Q

Classifications of nerve

A

Purse sensory ( afferent) or motor ( efferent) nerves are rare ; most mixed

Types of fibers in mixed nerves
Somatic afferent /efferent
Visceral afferent / efferent

Peripheral nerves classified as cranial or spinal nerve

21
Q

Ganglia

A

Contain neuron call bodies associated with nerves in pns

Associated with afferent nerve fibers contain cell bodies of sensory neurons
Dorsal root ganglia ( sensory , somatic )

Ganglia associated wirh efferent nerve fibers contain autonomic motor neurons 
  Automatic ganglia ( motor, visceral)
22
Q

Regeneration of nerve fibers

A

Mature neurons are amitotic but if soma of damage nerve is intact, peripheral axon may regenerate

If peripheral axon damaged
Axon fragments ( wallerian degeneration) spreads distally from injury
Macrophages clean dear axon; myelin sheath intact
Axon filaments grow through regeneration tube
Axon regenerates: née myelin sheath forms
Greater distance between severed ends-less chance of regeneration

23
Q

Nerve fiber

A

Most cns fibers never regenerate
Cns oligodendrocytes bear growth inhibiting proteins that prevents cns fiber regeneration
Astrocytes at injury site from scar tissue containing chondroitin sulfate that blocks axonak regrowth
Treatment
Newuteuzinf growth inhibitors, blocking receptors for inhibitory proteins, destroying chondroitin sulfate promising

24
Q

Cranial nerve

A

12 park of nerves that arise from brain and exit through foramina leading to muscles, glands and sense organs in head and neck

Input and output reminds ipsilatreal except vn ( 2,4)

25
Q

Cranial nerve

A

Olfactory : smell /sensory only
Optic nerves vision / sensory only
Oculomotor nerve : motor eyelid movement
Trickle at nerve muscle for eye rotation/motor
Trigeminal nerve : both face nerve , motor for mastification
Abducens nerve : rotate laterally, motor

26
Q

Cranial nerve

A

Vestibulocochlear nerve : sensory only hearing sense of balance
Glossopharyngeal nerve : mixed : motor for salvation and sensory for Tate’s
Vagus nerve: major motor , allows muscle to swallow and speech
Accessory nerve : motor , head neck and shoulder movement
Hypoglossal nerve : motor provides tongue movement

27
Q

Spinal nerves

A

31 Paris of mixed nerves named for point of issue from spinal cord
Supply all body parts but head and part of neck
8- cervical
12 throacic
5 lumbar
5 sacral
1 coccygeal

28
Q

Spinal nerve roots

A

Each spinal nerve connects to spinal cord via two roots
Ventral roots
Contains motor efferent fibers from central horn motor neurons
Fibers inner age skeletal muscles
Dorsal roots
Contains sensory afferent fibers from sensory neurons in dorsal root ganglia and conduct impulses from peripheral receptors
Dorsal and ventral roots unite to form the spinal nerves ,

29
Q

Soinak nerves : rami

A

Spinal nerves quite short ( 1-2 vn)
Each branches into mixed rami
Dorsal Ramus
Ventral ramus - larger
Meninges branch - find reeters vertebral canal, innervates meninges and blood vessels
Rami communicantes: ( autonomic pathways)
Join ventral rami in thoracic region

30
Q

Spinal nerves plexuses

A

Within plexus fibers criss cross
Each branch contains fibers from several spinal nerves
Fibers from ventral ramus go to body periphery via several routes
Each limb muscle innervates by more than spinal nerve
Damage to one does not paralysis

31
Q

Innnervation of the skin: dermatomes

A

Area of skin innervates by cutaneous branches of single spinal nerve
All spinal nerves except C1 participate in dematomes

Extent of spinal cord injuries ascertained by affected dermatomes

Most overlap. So desctrution won’t cause compete numbness

32
Q

Stretch and tendon reflexes

A

To smoothly coordinate skeletal muscle nervous system must receive proprioceptor input regarding
Length of muscle : from muscle spindles
Amount of tension in muckraker
From tendon organs

33
Q

Muscle spindles ( proprioceptors )

A

Sense organs that monitor the length of the skeletal muscle

34
Q

The stretch myotatic reflex

A

When muscle is stretched, it contracts and maintain increase tonus

Help maintain equilibrium and posture
Stabilize joint by balancing tension in extensors and flexors smoothing muscles actions

Very sudden muscle stretch =tendon reflex

Reciprocal inhibition

Anatomy Muscles (5 decks)

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