DELLA degradation results in the release and activation of phytochrome interacting factor (PIF) transcription factors, such as PIF3 and PIF4, as well as other bHLH transcription factors

TLS Online TPP Program

#Id: 5617

#Unit 7. System Physiology – Animal

Somatosensory receptors are divided into the major groups of receptors according to specific sensation: 

Mechanoreceptors (for touch and proprioception)

Thermoreceptors (for temperature)

Nociceptors (for pain or noxious stimuli)

TLS Online TPP Program

#Id: 5618

#Unit 7. System Physiology – Animal

Proprioceptors relay information about muscle length and tension

Chemoreceptor for taste and smell as well as visceral receptors such as those sensitive to changes in the plasma level of O2 , pH, & Osmolality

Photoreceptors respond to light

TLS Online TPP Program

#Id: 5619

#Unit 7. System Physiology – Animal

Touch and pressure are sensed by four types of mechanoreceptors:

Meissner’s corpuscles

Merkel cells

Ruffini corpuscles

Pacinian corpuscles

TLS Online TPP Program

#Id: 5620

#Unit 7. System Physiology – Animal

The sensory nerves from mechanoreceptors are large myelinated Aα and Aβ fibers whose conduction velocities range from ∼70–120 & ∼40–75 m/s, respectively.

TLS Online TPP Program

#Id: 5621

#Unit 7. System Physiology – Animal

Impulses from nociceptors are transmitted via two

fiber types:

Thinly myelinated Aδ fibers (2–5 μm in diameter) that conduct at rates of ∼12–35 m/s 

Unmyelinated C fibers (0.4–1.2 μm in diameter) that conduct at low rates of ∼0.5–2 m/s

TLS Online TPP Program

#Id: 5622

#Unit 7. System Physiology – Animal

Activation of Aδ fibers, which release glutamate, is responsible for first pain (also called fast pain or epicritic pain)