Sensory Receptors

Sensory receptors

Cells monitored by sensory neurons

Sensation

Arriving info

Perception

Conscious awareness of a sensation

If the receptive field is large, how does that affect localization?

It is more difficult to localize

Tonic receptors

• slow-adapting receptors

• Ex. Pain receptors

What are slow-adapting receptors?

Shows little peripheral adaptations- continues to respond even after stimuli is gone.

Ex. Tonic receptors and pain receptors

What are physic receptors?

• Normally inactive

• Fast-adapting

• ex. Pacinian and meissner corpuscles

What are fast-adapting receptors?

Responds strongly at first but then decreases

What are the classifications of sensory receptors?

• exteroreceptors

• Proprioceptors

• Interoceptors

Externoceptors

Provide info about environment

Proprioceptors

Report positions of skeletal muscles and joints

Interoceptors

Monitors visceral organs

What are the general sensory receptors?

• nociceptors

• Thermoreceptors

• Mechanireceptors

• Chemoreceptors

What are nociceptors?

Free nerve endings with large receptive fields

Where are nociceptors common?

• in superficial portions of skin

• In joint capsules and periostea of bones

• Around walls of blood vessels

What are nociceptors sensitive to?

• temperature extremes

• Mechanical damage

• Dissolved chemicals released by injured cells

What do Type A fibers carry?

Sensations of fast pain such as an injection or deep cut

• reach CNS and trigger somatic reflexes

• Relays to primary somatosensory cortex and receive conscious attention

Are type A fibers myelinated or unmyelinated?

Myelinated

What do type C fibers carry?

Sensations of slow pain

• activates reticular formation and thalamus

• Aware of pain but only know the general area of it

Are type C fibers myelinated or unmyelinated?

Unmyelinated

Where are the free nerve endings of thermoceptors located?

• dermis

• Skeletal muscles

• Liver

• Hypothalamus

Sensation pathway for thermoreceptors?

Reticular formation→ thalamus→primary somatosensory cortex

Are thermoreceptors tonic or phasic?

Phasic and quickly adapt to temp

How are mechanoreceptors changed by stimuli?

The plasma membranes are distorted by physical stimuli

Mechanically gated ion channels open and close in response to

Twisting, compression, stretching

Three classes of mechanoreceptors

• tactile receptors

• Baroreceptors

• Proprioceptors

Tactile receptors provide what sensations?

• touch

• Pressure

• Vibration

Baroreceptors detect what?

Pressure changes in blood vessels and in digestive, respiratory, and urinary tracts

Proprioceptors monitors what?

Positions of joints and skeletal

Types of tactile receptors in skins

• free nerve endings

• Root hair plexus

• Tactile disc

• Bulbous corpuscle (Ruffini corpuscle)

• Lamellar corpuscle (Pacinian corpuscle)

• Tactile corpuscle (Meissner’s corpuscle)

Free nerve endings are

• sensitive to touch and pressure

• Tonic receptors with small receptive fields

Root hair plexus nerve endings

• Monitors distortions and movements across body surface whenever hairs are located

• Adapts rapidly

Tactile discs

• fine touch and pressure receptors

• Tonic receptors with very small receptive fields

Bulbous corpuscles (Ruffini corpuscles)

• sensitive to pressure and distortion

• Located in reticular dermis

• Tonic receptors that show little adaptation

Lamellar corpuscles (Pacinian corpuscle)

• sensitive to deep pressure

• Fast-adapting receptors

• Most sensitive to pulsing or high frequency vibrating stimuli

• A single dendrite lies within a series concentric layers of collagen fibers

Tactile corpuscles (Meissner corpuscles)

• perceives sensations of fine touch, pressure, and low-frequency vibration

• Adapt to stimuli within 1 second after contact

• Fairly large structures

• Most abundant in eyelids, lips, fingertips, nipples, and external genitalia

What are different proprioceptors?

• muscle spindles

• Golgi tendon organs

• Receptors in joint capsules

Muscles spindles

Monitors skeletal muscle length

Triggers stretch reflexes

Golgi tendon organs

• at junction between skeletal muscle and its tendon- monitors tension during muscle contraction

Receptors in joint capsules

Free nerve endings that detect pressure, tension, and movement at the joint

Chemoreceptors

• responds to water and lipid soluble substances that are dissolved in body fluids

• Exhibits peripheral adaptation in seconds

• Monitors pH, CO2, O2 in arterial blood at carotid bodies and aortic bodies

Carotid bodies

Near origin of internal carotid arteries

Aortic bodies

Between major branches of aortic arch