Somatosensory system-exam 2

What does somatosensory refer to

Bodily sensations of touch, pain, temperature, and proprioception

How are messages from sensory receptors transmitted to the CNS

Through electrical impulses or action potentials

What is an adequate stimulus

The type of stimulus that most easily activates a receptor and has the lowest threshold

Does adequate stimulus refer to the type or magnitude of stimulus

Type of stimulus

What is specificity

The amount of stimulus types that a receptor responds to

What does increased receptor specificity mean

The receptor responds to fewer types of stimuli

What is modality

The perceived sensory experience characteristic of a particular type of receptor

What are rapidly adapting receptors

Receptors that generate action potentials primarily when a stimulus starts or stops and provide information about changes

What are slowly adapting receptors

Receptors that generate action potentials for as long as stimulation is applied

What four properties can be used to classify sensory receptors

Origin of adequate stimulus, type of adequate stimulus, subjective sensory experience, and anatomy of receptor

What are exteroceptors

Receptors that mediate signals coming from outside the body and are mostly located in the skin

What are proprioceptors

Receptors that mediate impulses from muscles, tendons, joints, ligaments, and joint capsules

What are enteroceptors

Receptors that mediate impulses from visceral organs such as the stomach and blood vessels

What are mechanoreceptors

Receptors that respond to mechanical stimuli such as touch, pressure, or skin stretch

What are chemoreceptors

Receptors that respond to chemical substances

What are photoreceptors

Receptors in the retina that respond to light

What are thermoreceptors

Receptors that respond to heat or cold

How can receptors be classified based on anatomy

As encapsulated receptors or free receptors

What do nociceptors signal

A stimulus is producing tissue damage or will produce tissue damage if it continues

What type of receptors are all nociceptors

Free receptors

What are the two kinds of nociceptors

High-threshold mechanoreceptors and polymodal nociceptors

What activates high-threshold mechanoreceptors

Intense mechanical stimulation

What activates polymodal nociceptors

Intense mechanical stimuli, intense thermal stimuli, and chemicals present with tissue damage

Can sensory signals be suppressed or enhanced before reaching the brain

Yes, suppression or enhancement can occur at synapses in the spinal cord, brainstem, and cortex

What type of receptors are thermoreceptors and when do they fire most

Free receptors that generate the most action potentials during rapid temperature changes

What is the adequate stimulus for thermoreceptors

A relatively quick change in skin temperature

What are the four low-threshold mechanoreceptors

Meissner's corpuscles, Ruffini's endings, Merkel's disks, and Pacinian corpuscles

Where are Meissner's corpuscles located and are they encapsulated or free

Just beneath the epidermis and encapsulated

Are Meissner's corpuscles rapidly or slowly adapting

Rapidly adapting

What is the adequate stimulus for Meissner's corpuscles

Low-threshold depression or indentation of the skin

What information do Meissner's corpuscles provide

Direction and velocity of objects moving on the skin

Where are Ruffini's endings located and are they encapsulated or free

In the dermis and encapsulated

Are Ruffini's endings rapidly or slowly adapting

Slowly adapting

What is the adequate stimulus for Ruffini's endings

Stretching of the skin

What information do Ruffini's endings provide

Direction and magnitude of skin stretch and information about friction and slippage during grasping

Where are Merkel's disks located and are they encapsulated or free

At the epidermis and dermis junction especially in distal extremities, lips, and fingertips and are free endings

Are Merkel's disks rapidly or slowly adapting

Slowly adapting

What is the adequate stimulus and function of Merkel's disks

Pressure and providing information about light pressure

Where are Pacinian corpuscles located and are they encapsulated or free

Between the dermis and subcutaneous tissue and are encapsulated

Are Pacinian corpuscles rapidly or slowly adapting

Very rapidly adapting

What is the adequate stimulus for Pacinian corpuscles

Very rapid indentation of the skin at 100 to 400 Hz

Which receptor probably signals indentation frequencies below 100 Hz

Meissner's corpuscles

What two factors determine the size of a cutaneous receptive field

Density of receptors and number of receptors sending axons to one neuron

When does receptive field size increase

When the number of receptors increases or receptor density decreases

How does receptive field size differ between the distal and proximal upper extremity

Receptive fields are smaller distally and larger proximally

What is normal two-point discrimination at the fingertips versus the palm

2 to 3 mm at the fingertips and 5 to 7 mm in the palm

What does topographic organization of cutaneous afferent pathways mean

Impulses from adjacent parts of the body travel in adjacent fibers

What is stereognosis

The ability to recognize an object through touch without vision

What is hyperalgesia

An exaggerated reaction to a stimulus that is normally painful

What is allodynia

Pain from a stimulus that does not normally provoke pain