Achievable logoAchievable logo
MCAT
Sign in
Sign up
Purchase
Textbook
Practice exams
Support
How it works
Exam catalog
Mountain with a flag at the peak
Textbook
Introduction
1. CARS
2. Psych/soc
2.1 Sensing the environment
2.1.1 Sensory perception
2.1.2 Signal detection and sensory adaptation
2.1.3 Psychophysics and receptors
2.1.4 Sensory pathways and sleep physiology
2.1.5 Touch/somatosensation
2.1.6 Vision
2.1.7 Hearing
2.1.8 Gustation
2.1.9 Olfactory, kinesthesia and vestibular
2.2 Making sense of the environment
2.3 Responding to the world
2.4 Individual influences on behavior
2.5 Social processes and human behavior
2.6 Attitude and behavior change
2.7 Self-identity
2.8 Psych/soc factors affecting interaction and perception
2.9 Elements of social interaction
2.10 Understanding social structure
2.11 Demographic characteristics and processes
2.12 Social inequality
3. Bio/biochem
4. Chem/phys
Wrapping up
Achievable logoAchievable logo
2.1.5 Touch/somatosensation
Achievable MCAT
2. Psych/soc
2.1. Sensing the environment

Touch/somatosensation

2 min read
Font
Discuss
Share
Feedback

Somatosensation refers to a general sense (not a special sense). It includes proprioception and interoception, along with sensory modalities such as pressure, vibration, light touch, tickle, itch, temperature, pain, and kinesthesia.

Instead of being housed in one specialized organ, somatosensory receptors are distributed throughout the body. You’ll find them in the skin, muscles, tendons, ligaments, joint capsules, and even within visceral organs.

Two important somatosensory signals - pain and temperature - are transduced by free nerve endings. These endings include:

  • Thermoreceptors, which respond to temperature differences from body temperature

  • Nociceptors, which detect potentially damaging mechanical, chemical, or thermal stimuli

  • When tissues are stressed or injured, they release chemicals that activate proteins in nociceptors. An example is capsaicin, the heat-inducing molecule in spicy foods, which binds to ion channels sensitive to temperatures above 37°C. Capsaicin remains attached for an extended period, reducing pain responses from the activated nociceptor; this property makes it useful as a topical analgesic.

  • When a textured surface causes the skin on your finger to vibrate, these low-frequency vibrations are detected by Merkel cells (also called type I cutaneous mechanoreceptors), located in the stratum basale of the epidermis. In contrast, deep pressure and higher-frequency vibration are registered by lamellated (Pacinian) corpuscles, found in deeper layers of the dermis or subcutaneous tissue.

  • Light touch is sensed by tactile (Meissner) corpuscles, while hairs on the skin are wrapped by the hair follicle plexus to detect hair movement (such as an insect crawling on the surface). Skin stretch is transduced by bulbous corpuscles (also known as Ruffini corpuscles or type II cutaneous mechanoreceptors).

Additional somatosensory receptors reside in muscles and joints. They monitor the degree of stretch in tendons and muscle tissue, helping prevent injury.

Muscle spindles are stretch receptors located in skeletal muscle fibers. They initiate reflexes that help prevent over-stretching or muscle tearing.

Golgi tendon organs detect stretch within tendons.

Bulbous corpuscles appear in joint capsules, measuring the stretch in skeletal components around the joint.

Somatosensation overview

  • General sense including proprioception, interoception, and modalities: pressure, vibration, light touch, tickle, itch, temperature, pain, kinesthesia
  • Receptors distributed throughout skin, muscles, tendons, ligaments, joint capsules, visceral organs

Pain and temperature

  • Detected by free nerve endings:
    • Thermoreceptors: sense temperature changes
    • Nociceptors: detect damaging stimuli (mechanical, chemical, thermal)
  • Capsaicin binds to heat-sensitive ion channels (>37°C), used as topical analgesic

Touch and vibration receptors

  • Merkel cells: detect low-frequency vibration, located in stratum basale
  • Lamellated (Pacinian) corpuscles: sense deep pressure, high-frequency vibration, found in deep dermis/subcutaneous tissue
  • Tactile (Meissner) corpuscles: sense light touch
  • Hair follicle plexus: detects hair movement
  • Bulbous (Ruffini) corpuscles: sense skin stretch

Muscle and joint receptors

  • Muscle spindles: stretch receptors in skeletal muscle, prevent overstretching
  • Golgi tendon organs: detect tendon stretch
  • Bulbous corpuscles: present in joint capsules, measure joint stretch

Sign up for free to take 4 quiz questions on this topic

All rights reserved ©2016 - 2026 Achievable, Inc.

Touch/somatosensation

Somatosensation refers to a general sense (not a special sense). It includes proprioception and interoception, along with sensory modalities such as pressure, vibration, light touch, tickle, itch, temperature, pain, and kinesthesia.

Instead of being housed in one specialized organ, somatosensory receptors are distributed throughout the body. You’ll find them in the skin, muscles, tendons, ligaments, joint capsules, and even within visceral organs.

Two important somatosensory signals - pain and temperature - are transduced by free nerve endings. These endings include:

  • Thermoreceptors, which respond to temperature differences from body temperature

  • Nociceptors, which detect potentially damaging mechanical, chemical, or thermal stimuli

  • When tissues are stressed or injured, they release chemicals that activate proteins in nociceptors. An example is capsaicin, the heat-inducing molecule in spicy foods, which binds to ion channels sensitive to temperatures above 37°C. Capsaicin remains attached for an extended period, reducing pain responses from the activated nociceptor; this property makes it useful as a topical analgesic.

  • When a textured surface causes the skin on your finger to vibrate, these low-frequency vibrations are detected by Merkel cells (also called type I cutaneous mechanoreceptors), located in the stratum basale of the epidermis. In contrast, deep pressure and higher-frequency vibration are registered by lamellated (Pacinian) corpuscles, found in deeper layers of the dermis or subcutaneous tissue.

  • Light touch is sensed by tactile (Meissner) corpuscles, while hairs on the skin are wrapped by the hair follicle plexus to detect hair movement (such as an insect crawling on the surface). Skin stretch is transduced by bulbous corpuscles (also known as Ruffini corpuscles or type II cutaneous mechanoreceptors).

Additional somatosensory receptors reside in muscles and joints. They monitor the degree of stretch in tendons and muscle tissue, helping prevent injury.

Muscle spindles are stretch receptors located in skeletal muscle fibers. They initiate reflexes that help prevent over-stretching or muscle tearing.

Golgi tendon organs detect stretch within tendons.

Bulbous corpuscles appear in joint capsules, measuring the stretch in skeletal components around the joint.

Key points

Somatosensation overview

  • General sense including proprioception, interoception, and modalities: pressure, vibration, light touch, tickle, itch, temperature, pain, kinesthesia
  • Receptors distributed throughout skin, muscles, tendons, ligaments, joint capsules, visceral organs

Pain and temperature

  • Detected by free nerve endings:
    • Thermoreceptors: sense temperature changes
    • Nociceptors: detect damaging stimuli (mechanical, chemical, thermal)
  • Capsaicin binds to heat-sensitive ion channels (>37°C), used as topical analgesic

Touch and vibration receptors

  • Merkel cells: detect low-frequency vibration, located in stratum basale
  • Lamellated (Pacinian) corpuscles: sense deep pressure, high-frequency vibration, found in deep dermis/subcutaneous tissue
  • Tactile (Meissner) corpuscles: sense light touch
  • Hair follicle plexus: detects hair movement
  • Bulbous (Ruffini) corpuscles: sense skin stretch

Muscle and joint receptors

  • Muscle spindles: stretch receptors in skeletal muscle, prevent overstretching
  • Golgi tendon organs: detect tendon stretch
  • Bulbous corpuscles: present in joint capsules, measure joint stretch