Lecture 5: Somatic Sensory System Flashcards by Randi Adams

Information in the _____________ system proceeds from the receptor through a series of neurons in the brain

somatosensory

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What is the specialized nervous system that allows us ti receive information from the body in order to interact with the world, move accurately, and avoid/minimize injuries?

Somatic Sensory System

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What is the awareness of stimuli form the sense?

Receptors concert the energy of the stimulus into electrical potentials
Action potentials propagate to specific areas of the brain

sensation

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What is the interpretation of sensation into meaningful forms?
Once the brain recognizes a sensation, it interprets it, giving the __________ (color, taste, sound) of a stimulus

Perceptions

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Put these words in working order: 
Conduction 
Receptor 
Translation 
Stimulus

Stimulus
Receptor
Conduction
Translation

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What component of the sensory system applies to the receptor triggering a graded membrane potential in the receptor?

Stimulus

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What component of the sensory system converts stimulus energy to impulse (action potential)?

Receptor

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What component of the sensory system sends the impulse over the sensory pathway to CNS?

Conduction

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What component of the sensory system is the region of the CNS that receives impulses and integrates information? It may also prepare a response.

Translation

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Environmental energy or energy change that causes a change in receptor potential in a receptor cell

Stimulus

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Stimulation determines the _____ of receptors that are activated as well as the pattern of signal ____________.

Type

transmission

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Specialized peripheral element of the sensory neuron where the sensation and perception begin

Receptors

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Each type of receptor is specialized, responding only to a specific type of ________

stimulus

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Neurons with free nerve endings

simple receptors

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Nerve endings enclosed in connective tissue capsule

complex neural receptors

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Cells that release neurotransmitter into sensory neurons, initiating an action potential

special senses receptors

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What is the classification of sensory receptors?

General Senses: somatic and visceral

Special Senses

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What are somatic senses receptors?

tactile, thermal, pain, and proprioceptive

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What are visceral sensory receptors?

provide information about conditions within internal organs

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What are the special senses?

Smell, taste, vision, hearing, and equilibrium or balance

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Where are exterorecptors located?

What do they detect?

at or near body surface (superficial, cutaneous)

Detect external stimuli (light, heat, chemicals, pressure)

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Where are interorecptors located?

What do they detect?

Deep

React to stimuli coming from internal body/organs (blood pressure, plasma osmolarity, blood pH)

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What are examples of proprioceptors?

What do they sense?

muscles, tendons, ligaments

position and kinesthetic sense

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What receptors react to mechanical stimuli (touch, stretch)?

mechanoreceptors

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What receptors react to chemical molecules of substances (ex. smell, taste, substance P)?

chemoreceptors

What receptors react to hot and cold?

thermorecptors

What receptors are sensitive to stimuli that damage or threaten to damage tissue?

Nociceptors

What receptors process vision?

Photoreceptor

Superficial and Subcutaneous mechanoreceptors are composed of what type of fibers?

A beta fibers

Proprioception provides information regarding: _______ of muscles, _______ on tendons, _________ of joints, and deep _________.

Stretch Tension positions vibrations

What is kinesthetic sensory?

Sense about movement

Where does perception occur?

Cerebrum

Stimulation of nociceptors results in a sensation of ____

pain

Receptors that respond as long as a stimulus is maintained are called:

Tonic Receptors

Receptors that adapt to a constant stimulus and stop responding are called:

Phasic receptors

Peripheral sensory neurons have two axons, distal and proximal. What do each of these do?

Distal axons conduct messages from the receptor to the cell body Proximal axons project from the cell body into the spinal cord or brainstem

Which axons transmit information faster, large-diameter or small-diameter?

Large diameter because large-diameter axons are myelinated, allowing saltatory conduction of the action potential

Peripheral axons are also called:

afferents

All of the fine touch receptors transmit information on which afferents?

A-Beta afferents

Free nerve endings (Thermal and nociceptors) operate on what afferents?

A-delta and C

Type 1a afferents register what type of movements?

Quick and tonic stretch

Type II afferents monitor what?

Tonic stretch of a muscle

Specialized muscle fibers that compose the muscle spindle are called:

intrafusal fibers

Ordinary muscle fibers outside of the muscle spindle are called:

extrafusal fibers

Intrafusal Fibers are proprioceptors. What information do they tell us about the muscle?

degree of stretch | velocity of stretch

Why is alpha-gamma co-activation important?

When the alpha motor neurons cause the extrafusal fibers to stretch, the gamma motor neurons cause the intrafusal fibers to stretch, and this allows the sensory endings to indicate stretch

Tension in tendons is relayed by:

Golgi tendon organs

What type of afferents transmit information from the Golgi tendon organs to the spinal cord?

Type Ib afferents

Free nerve endings are most often stimulated by:

inflammation

The area of skin innervated by a single afferent neuron is called the _________ ______ for that neuron

receptive field

Receptive fields tend to be smaller ________ and larger __________

distally | proximally

Superficial mechanoreceptors have a ______ receptive field

small

Subcutaneous mechanoreceptors have a _____ receptive field

large

What is the diameter of the axon afferent being described? | Transmit information form specialized receptors in muscles, tendons, and joints

Large

What is the diameter of the axon afferent being described? | transmit information from joint capsules, muscle spindles, and cutaneous touch, pressure, and stretch receptors

Medium

What is the diameter of the axon afferent being described? | Convey crude touch, nociceptive, and temperature information from both the musculoskeletal system and the skin

Smallest

Roman numerals are for ___________ axons, and letters are for all others.

Proprioceptive

_______________ is necessary for accurate control of movements and protects against injury

Somatosensation

The primary somatosensory cortex is essential for:

two point discrimination graphesthesia stereognosis simultaneous awareness of stimulation on both sides of the body

In a nerve conduction study, amplitude often serves as a measurement for what?

How many axons are conducting

To determine whether an NCS is normal, three numeric values are compared:

distal latency amplitude of the evoked potential conduction velocity

What does conduction velocity measure?

The distance between the electrodes divided by the amount of time from the stimulus to the first depolarization at the recording electrode

______ _______ is the time required for the depolarization evoked by the stimulus to reach the distal recording site.

distal latency

Incoordination that is not due to weakness:

Ataxia

The Romberg test is used to differentiate between what two types of ataxia?

cerebellar and sensory

Lesions that produce sensory ataxia are located where?

peripheral sensory nerves dorsal roots dorsal columns of the spinal cord medial lemnisci

What is the Romberg sign?

People have better balance with their eyes open but become unsteady with their eyes closed

What does a positive Romberg sign indicate?

sensory ataxia

Dysfunction or pathology of one of more peripheral nerves is __________

neuropathy

What is the order of sensory loss involved with peripheral neuropathy?

``` Conscious perception and discriminative touch Cold Fast pain Heat Slow Pain ```

After compression on a peripheral nerve is relieved, sensations return in the ________ order that they were lost

reverse

Because large axons are the most heavily myelinated, demyelination of axons in a peripheral nerve often affects proprioception and vibratory sense most severely, resulting in diminished or lost _______________.

Proprioception

Complete transection of the cord prevents all sensation how far below the level of the lesion from ascending to higher levels in the cord?

1-2 levels

A hemisection of the spinal cord interrupts pain and temperature sensation from what side of the body? Why?

Contralateral | the axons transmitting nociceptive and temperature information cross to the opposite side of the cord upon entering

A hemisection of the spinal cord interrupts discriminative touch and conscious proprioception from what side of the body? Why?

Ipsilateral This information ascends on the same side that it enters the spinal cord on

In a lesion of the posterior column, what 3 senses are lost?

Vibration conscious proprioception two point discrimination

What system regulates homeostasis and the reproductive system?

ANS

The maintenance of optimal internal environment, including body temperature and chemical composition of tissues and fluids

Homeostasis

The _________ nervous system regulates the viscera, vasculature, and glands

autonomic

What three cranial nerves convey autonomic afferent information?

Facial (VII) Glossopharyngeal (IX) Vagus (X)

Most of the visceral information entering the brainstem via cranial nerves converges in the ________ ________

solitary nucleus

Areas within the medulla control:

heart rate respiration vasoconstriction vasodilation

Areas of the ____ are also responsible for controlling respiration

pons

The ___________ is considered to be the master controller of homeostasis

hypothalamus

Neurons that adapt quickly to a pressure stimulus, but stop sending action potentials when pressure is continually applied

Rapid Adapting

Neurons that continually create action potentials at a slower rate when pressure is continually applied

Slow Adapting

Coarse touch, pain, and temperature are all received by what type of receptor?

Free nerve endings (A delta and C fibers)

What type of receptor has slow adapting fibers and detects object pressure and form (Static sense)?

Tonic Receptor

What type of receptor has fast adapting fibers that detect motion and vibration (respond to a change)?

Phasic Receptor

What four attributes comprise signal conduction of a neuron?

Modality Location Intensity Duration

______, ___________, and ________ ________ cross the midline in the spinal cord

pain, temperature, and course touch

_______ _______, _________, and _______________ pathways cross the midline in the medulla

fine touch, vibration, and proprioception

Diameter of the axons, degree of axonal myelination, and number of synapses in the pathway determine the _____ of information processing

speed

What is it called when synapses spread action potentials to several areas of the CNS?

Divergence

What is it called when synapses focus action potentials from several sensors on narrow areas of the CNS?

Convergence

Many primary sensory neurons converging onto single secondary neuron creates a very large _________ ______. The two stimuli will be perceives as a single point excuse both stimuli fall within the same receptive field

Receptive field

When fewer neurons converge, secondary receptive fields are much _______. The two stimuli activate separate pathways are are perceived as distinct stimuli.

smaller

Training of certain neurons by repeatedly stimulating a specific neuron and the pathway closest to the stimulus inhibits neighboring neurons, thus enhancing perception of the stimulus:

Activity-dependent neuroplasticity

Somatosensory information protects the body against ______

injury

Varicella-zoster virus causes chickenpox and infects the _______ ______ _________.

dorsal root ganglion