SFIII Physiology - Unit 1 : Somato-Visceral Sensitivity Receptors Cartes | Quizlet

What is a sensory receptor?

A specialized structure that detects a specific type of stimulus and converts it into a neural signal.

What is the sensory pathway?

Stimulus → receptor → sensory fiber → spinal cord → brain.

Where are sensory receptors found?

Skin, epithelium, muscles, bones, joints, internal organs, cardiovascular system.

What does somato-visceral sensitivity include?

Touch, thermoreception, proprioception, visceral sensitivity, pain.

What is a primary receptor?

The receptor is the axon terminal of a sensory neuron (the ending itself detects the stimulus).

What structures can primary receptors have?

Free nerve endings or encapsulated endings.

What do free nerve endings detect?

Pain, temperature, itch, crude touch.

What do encapsulated endings detect?

Touch, pressure, vibration.

What is a secondary receptor?

A separate specialized cell that detects the stimulus and synapses with a sensory neuron.

Example of a secondary receptor

Photoreceptors in the retina.

What are mechanoreceptors?

Receptors activated by mechanical deformation (touch, pressure, stretch, vibration).

What are thermoreceptors?

Receptors detecting temperature changes.

What are nociceptors?

Receptors detecting harmful or potentially damaging stimuli.

What are photoreceptors?

Light-sensitive receptors in the retina.

What are chemoreceptors?

Receptors detecting chemical changes (taste, smell, pH, gases).

What are proprioceptors?

Mechanoreceptors detecting joint position, muscle length, tension, and body orientation.

What is superficial somatic sensitivity?

Touch & temperature from skin and mucous membranes.

What is deep somatic sensitivity?

Proprioception from muscles, tendons, bones, joints.

What is visceral sensitivity?

Sensory input from thoracic & abdominal organs.

What is nociception?

Detection of harmful or painful stimuli.

What sensations does the sense of touch include?

Pressure, touch, vibration, itching.

What are the different physiological classifications of mechanoreceptors ?

slowly adapting

rapidly adapting

type C

Where are Merkel discs located?

Beneath epidermis, mainly non-hairy skin.

What do Merkel discs detect?

Continuous pressure, texture, fine touch.

How do Merkel discs adapt?

Slowly (tonic).

Where are Meissner corpuscles found?

Dermal papillae of fingertips, lips, tongue, non-hairy skin.

What do Meissner corpuscles detect?

Fine touch, low-frequency vibration, movement across skin.

How do Meissner corpuscles adapt?

Fast (phasic).

Where are Pacinian corpuscles found?

Deep dermis and hypodermis, sometimes muscles.

What do Pacinian corpuscles detect?

Deep pressure and high-frequency vibration.

How do Pacinian corpuscles adapt?

Very fast (very phasic).

Where are Ruffini endings located?

Deep dermis of hairy skin.

What do Ruffini endings detect?

Skin stretch, continuous pressure, joint angle.

How do Ruffini endings adapt?

Slowly.

Where are Krause end bulbs found?

Tongue and genital regions.

What do Krause end bulbs detect?

Light touch, initial contact.

How do Krause end bulbs adapt?

fast

What do hair follicle receptors detect?

Movement of hair (light touch).

How do hair follicle receptors adapt?

Fast.

Where are free nerve endings located?

Epidermis and superficial dermis.

What do free nerve endings detect?

Pain, temperature, itch, crude touch.

Which fibers innervate free nerve endings?

C fibers (unmyelinated).

What is a tonic receptor?

A receptor that fires continuously as long as the stimulus is present.

Examples of tonic receptors

Muscle spindle, Merkel disc, joint capsule receptors.

What is a phasic receptor?

A receptor that fires only when the stimulus changes.

Examples of phasic receptors

Pacinian corpuscles, Meissner corpuscles, hair follicle receptors.

What is proprioception?

The sense of body position, movement, muscle activity, orientation in space.

Where are proprioceptors located?

Muscles, tendons, bones, joints, skin.

Why do fast-moving animals need more proprioception?

To maintain posture and coordinated movement.

Where are muscle spindles located?

Inside muscles, within intrafusal fibers.

What do muscle spindles detect?

Muscle length and velocity of length change.

What neuron regulates muscle spindle sensitivity?

Gamma motor neurons.

Where is the Golgi tendon organ located?

At the junction between muscle and tendon.

What does the Golgi tendon organ detect?

- tendon tension / rate of change

- muscle tension

Main function of Golgi Tendon Organ

Protects from excessive force

Are visceral sensations usually conscious?

No, they are mostly unconscious.

When do visceral sensations become conscious?

During intense mechanical or chemical stimuli.

Is visceral pain well localized?

No, it is poorly localized and diffuse.

Does injury severity correlate with pain intensity?

No: small lesions may cause severe pain and vice versa.

What is referred pain?

Visceral pain perceived at a different location, usually on the skin.

Why does referred pain occur?

Due to convergence of visceral and somatic afferents on the same second-order neuron.

Example of referred pain

Heart pain felt in the left arm.

What are nociceptors structurally?

Free nerve endings.

Where are nociceptors found?

Skin, periosteum, peritoneum, muscles, joints, arterial walls

Where are nociceptors absent?

CNS & most viscera (kidney, liver, lungs)

Do nociceptors adapt?

No, they show little or no adaptation.

What is hyperalgesia?

Increased sensitivity to pain due to lowered activation threshold.

What are the two types of somatic pain?

Superficial and deep.

Which fibers conduct fast, sharp pain?

Group III myelinated fibers.

Which fibers conduct slow, burning pain?

Group IV unmyelinated C fibers.

Causes of visceral pain

kidney/gallstones

gastrointestinal ulcers

inflammation (appendicitis)

Visceral smooth muscle spasms

Visceral ischemia

What activates mechanical nociceptors?

Extreme mechanical stress (pinch, crush, pressure).

What activates thermal nociceptors?

Extreme temperatures (<10°C or >48°C).

What activates chemical nociceptors?

sensitive to irritable chemicals

What activates polymodal nociceptors?

Extreme mechanical, thermal, or chemical stimuli.

Which fibers do polymodal nociceptors use?

C fibers (Group IV).

What are the 4 main painful stimuli?

Mechanical, thermal, chemical, polymodal.