An interesting characteristic of pain is that there are not universal levels across the globe. For instance, in some parts of the world people endure rituals (that involve self mutilation and burning) with stoic indifference, whereas others would cry out in pain. Learning, experience, emotion, and culture all affect the perception of pain in striking ways.
- McGill's Three Aspects of Pain

Measuring Human Pain

Pain, although in some aspects emotional, can find its basis in the physiological occurrences of the human body.
- Damaged Tissue and Chemical Release
- Nociceptors
- Specialized Pain Fibers
- Pain in the Spinal Pathways
- Cortical Substrates for Pain
- Neuropathic Pain and Phantom Limbs
- The Pain of Social Rejection 
- Controlling Pain

Biological Basis of Pain

Pain is an unpleasant experience that encompasses both physical sensations and psychological elements.

Experience of pain

Headache library

A headache is defined as a sustained pain in the head. Primary headaches, the most common form, have no underlying cause (ex. migraine, tension, headaches, cluster headaches). Secondary headaches have an underlying cause (ex. infection, vascular disease, trauma, brain tumor).

Headache

The sensation of pain serves a crucial adaptive role by alerting an individual to injury. It motivates behavior to move away from the source of harm and encourages protective actions, such as being more gentle with an injured area, to prevent further damage and facilitate healing.

Adaptive Functions of Pain

Based on the case presented, evaluate the statement: 'A life without the sensation of pain would be ideal.' In your evaluation, justify your position by explaining the primary function of pain and predicting the long-term health challenges this individual is likely to face.

The Paradox of a Pain-Free Life

Congenital insensitivity to pain, or congenital analgesia, is a very rare genetic disorder in which an individual is born without the ability to feel pain. Although individuals with this condition can detect differences in temperature and pressure, their inability to experience pain frequently leads to significant injuries, such as young children repeatedly biting their mouths and tongues. Because of these injuries and resulting secondary infections, those affected typically have much shorter life expectancies.

Congenital Insensitivity to Pain

The somatosensory system is partly responsible for detecting painful stimuli. Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
- Importance of Pain
- Congenital Insensitivity to Pain
- Classifying Pain
- Biological Basis of Pain

Johns Hopkins University

Google

Sensory receptors such as eyes or taste buds develop differently in different species. Sensory processing refers to the ways the brain integrates information received from sensory receptors in order to process appropriate behavioral or cognitive response. 

- Sensory organs
- Stimuli
- Receptor Cells
- Touch and the skin
- Pain
- Sensory processing disorder
- Synesthesia

Sensory processing, touch and pain

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Sensory receptor organs act as filters of the environment by responding to certain stimuli (ie. eyes for vision, ears for hearing). These organs, often times body parts, are particularly sensitive to some forms of energy.
- Receptor cells
- Hierarchy of Sensory Systems

Sensory Organs

A stimulus (plural: stimuli) is an event that affects the sensory organ. Stimuli can be sound waves, light entering the eye, or food touching the tongue.
- Adequate stimulus
- Labeled Lines
- Stimulus localization
- Selection and analysis along sensory pathways
- Selectivity and Range of Response to Stimuli

Stimuli

A condition in which a stimulus in one modality can trigger experiences in another or multiple other modalities. For example, to someone with this condition (a synesthete), the letter could be seen as green, or a particular musical tone could evoke a particular taste sensation. 
For the colored letters and numbers, some studies have pointed to this association with popular toys that depict these figures in the same colors. 

Synesthesia

A large part of our somatosensory system is responsible for our perception of touch.
- Sensory Organ: Skin
- Dorsal Column System
- Primary Sensory Cortex
- Secondary Sensory Cortex
- Skin sensory receptors

Somatosensory System: Touch

Somatosensory System: Pain

Sensory processing, touch and pain references

A condition where the brain has trouble receiving and responding to sensory input. May affect one or multiple senses. Symptoms could include over-sensitivity to certain stimuli, difficulties with coordination, or failure to respond to outside stimuli. This disorder is often seen in individuals on the Autism spectrum. It is not currently recognized as a distinct medical diagnosis.

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