Understanding Pain Theories

Intro to Pain

• Pain experts haven't yet fully explained pain's complexity, despite years of study and various theories.

Key Pain Theories

• Specific Theory: Pain directly results from injury or damage, with specific nerves signaling the brain.
• Pattern Theory: Pain is determined by nerve activity patterns, not specific pain receptors.
• Gate Control Theory: A spinal cord "gate" controls pain signals, either allowing them to reach the brain or blocking them.
• Neuromatrix Theory: Pain is created by a brain network, influenced by physical, emotional, and psychological factors, even without injury.

Pain Theory Descriptions

• Pain is a complex experience involving more than just physical injury.
• Ronald Melzack’s Gate Control Theory: Pain is shaped by experiences, expectations, and culture, not just a direct injury response and severe pain can be a burden, despite its warning function.
• International Association for the Study of Pain (IASP, 2020): Pain is an unpleasant sensory and emotional experience linked to potential or actual tissue damage.
• Pain is personal, influenced by biological, psychological, and social factors.
• Pain differs from nociception which is the nerve response to harmful stimuli.
• Pain is learned through life experiences and a person's report of pain should be respected.
• While pain serves a protective rule it can negatively affect well-being
• Sternbach and IASP (1968): Pain is a personal sensation signaling current or future tissue damage, prompting protective responses.
• McCaffery (1979): Pain is whatever the person says it is, whenever they say it exists.

Classification of Pain: Location

• Pain is classified based on location and duration.
• Cutaneous Pain: Sharp, well-localized pain in skin and subcutaneous tissue due to many pain receptors.
• Deep Somatic Pain: Diffuse, throbbing pain in bones, muscles, tendons, ligaments, joints; can radiate depending on tissue sensitivity.
• Periosteum and joint capsules are highly sensitive.
• Tendons, ligaments, and subchondral bone are moderately sensitive.
• Muscle and cortical bone are less sensitive.
• Synovium, articular cartilage, and fibrocartilage are almost insensitive.
• Visceral Pain: Diffuse, poorly localized pain from internal organs, often due to stretching, distension, or ischemia.
• Can cause referred pain, felt in a different area from the actual source.

Duration of Pain: Acute

• Sudden onset, often from trauma, surgery, or inflammation.
• Acts as a warning of tissue damage and is short term, improving as healing occurs.
• It can be localized or generalized and triggers autonomic responses, such as increased heart rate and high blood pressure.
• Emotional responses like anxiety and fear may be present and typically manageable, reducing over time.
• Starts as sharp and stabbing, becoming aching as it heals.

Duration of Pain: Chronic

• Can start suddenly, but usually develops gradually and lasts longer than 3-6 months and often continues beyond normal healing.
• Cause may be unknown, sometimes linked to nervous system changes (sensitization) and is often poorly localized and described as dull, aching, nagging, or tiring.
• Mostly transmitted by small, unmyelinated C-fibers, leading to persistent pain.
• Complete relief might not be possible, leading to changes in behavior and coping and is often accompanied by fatigue, sleep disturbances, loss of appetite, and depression.
• Possible link between chronic pain, depression, and low serotonin levels.

Classification of Pain: Other Types

• Localized Pain: Confined to the exact site of injury or origin.
• Projected Pain: Follows a specific nerve pathway, such as Herpes zoster, toothache, or sciatica.
• Radiation Pain: Spreads out from the original site but is not well-defined.
• Referred Pain: Felt in an area distant from the actual source and the skin and organ nerves share brain pathways, making pinpointing difficult.
• Phantom Limb Pain: Felt in a missing limb or body part, even when no longer there.

Pain Tolerance vs. Pain Threshold

• Threshold: Minimum intensity to begin feeling pain.
• Tolerance: Maximum pain level one can endure before seeking relief.

Pain Management

• Pain can be controlled at 3 levels.

Pain Management: At the Site of Pain (Periphery)

• Heat increases blood flow, while cold reduces swelling and numbs pain receptors.
• NSAIDs (ibuprofen) block chemicals that cause pain and inflammation.
• Local anesthetics numb nerve endings to stop pain signals.

Pain Management: At the Spinal Cord

• Epidurals, massage, and TENS block pain signals before they reach the brain.

Pain Management: At the Brain

• Opioids and antidepressants help manage pain, especially chronic pain.
• Relaxation techniques aid in like stress reduction, massage, physiotherapy, exercise, hypnosis, and acupuncture help distract from pain.
• Sedatives and anti-anxiety drugs reduce emotional distress from pain.

Pain Terms

• Nociception: Detecting pain through pain receptors (nociceptors) and feeling pain.
• Nociceptors: Free nerve endings detecting pain and respond to mechanical, thermal, and chemical stimuli.
• Skin has more nociceptors and does not adapt, continuing to send signals as long as stimulus is present.

Neuropathic vs. Nociceptive Pain

• Nociceptive Pain: Caused by tissue injury/damage activating pain receptors.
• Neuropathic Pain: Caused by nerve damage/dysfunction (peripheral/central nervous system), often chronic.

Pain Pathways: Nerve Fibers

• A-fibers: Large, myelinated nerve fibers transmitting sensory and motor signals that includes:
• A/Alpha (α): Motor control and body position (proprioception).
• A/Beta (β): Touch and pressure sensation.
• A/Gamma (γ): Touch and muscle movement.
• A/Delta (δ): Pain, temperature, and pressure.
• A-delta fibers are fast, sending signals at 10-30 meters/second and pain feels sharp and local.
• B-fibers: Small, myelinated fibers in the autonomic nervous system (ANS) transmitting motor signals only.
• C-fibers: Small, unmyelinated fibers carrying slow pain and itch sensations at 0.5-2.5 meters/second which feels dull, aching, and spread out.

Pain Pathways: Transmission of Pain

• With acute pain, signals serve:
• Reflex Response: First-order neuron signals muscle contraction to withdraw from a harmful Stimulus. Alerting the Brain: Signals reaches the brain for perception:
• Sensory system identifies pain location and intensity.
• Motivational system triggers emotions like fear or stress.
• Cognitive system interprets pain based on past experience.
• Pain modulation increases or decreases pain signals.

Pain Pathways: How The Brain Receives Pain Signals

• First-Order Neuron.
• Pain signals enter the spinal cord through the dorsal root
• Neurotransmitter release: Substance P and glutamate help transmit the pain signal.
• Second-Order Neuron.
• Delivers signal to the opposite side in and travels up spinal cord in spinothalamic tracts which also carry temperature and touch sensations

Pain Pathways to the Brain

• Two pain pathways to the brain:
• Neospinothalamic tract carries fast, sharp pain
• Paleospinothalamic tract carries slow, dull pain
• Fast pain (sharp, immediate): Travels via the neospinothalamic tract and reaches the thalamus, then the signal passes to the somatosensory cortex which pinpoints the location and intensity of the pain.
• Slow pain (dull, aching): Travels via the paleospinothalamic tract and passes through the reticular formation in the brainstem before reaching the thalamus, then to the cortex which the pain is felt as diffuse and ling-lasting.
• Additional Connections: Pain also stimulates autonomic responses, influences emotions, body functions and stress, and reaches different cortical areas like the limbs system.

Pain Modulation: Body Control

• Modulates pain naturally by the following.
• Production and triggering of brain pathways. Endogenous Painkillers:
• Endorphins, enkephalins, and dynorphins: Natural opioids blocking pain signals and bind to receptors as morphine
• Endorphins are found in the hypothalamus, limbic system, and pituitary gland which they reduce pain create euphoria (after exercise)
• Enkephalins that are found in the spinal cord, and prevent the release of substance P, stopping pain signals
• Dynorphins are found in the brain that help regulate fear stress, and pain

Pain Suppression

• Pain Suppression is done with the following.
• Acupuncture and TENS (electrical stimulation): activates and release natural opioids, that reduce pain
• Placebo effect: brain releasing painkillers when a person expects relief so there is some pain relief
• Endocannabinoids which are chemicals that and bind to CB1 receptors in the brain, reducing pain transmission
• Serotonin and norepinephrine: acts as and pain modulators in the brain and spinal cord

Emotional and Psychological Factors

• Pain can be naturally reduced by strong that affect emotions, stress, or focus on something else
• The adrenaline that causes pain can feel less intense because this explains during emergencies

Gate Control Theory of Pain

• Melzack and Wall proposed a spinal cord "gate" controls pain signals before they reach the brain.
• Touch signals (A/Beta fibers) block pain signals (C-fibers), closing the gate.
• Massage and TENS relieve pain by activating A/beta fibers that interfere with pain transmission.

Pain Sensitization

• Body becomes more sensitive to pain, easier for pain to start/feel stronger.
• Peripheral sensitization: happens at nociceptors, making them more reactive
• Central sensitization: happens in the brain and spinal cord, increasing perception
• Sensitization is a key factor in chronic pain conditions.

Causes of Pain (Etiology)

• Pain can be triggered by different stimuli:
• Ischemia (lack of blood flow): causes hypoxia and lactic acid buildup which activates pain receptors
• Distension or Contractions of organs: puts pressure on tissue or reducing blood flow (stomach or intestines)
• Extreme temperatures: causes high temps (over 43C) which can activate pain receptors
• Nerve compression: Causes neuropathic pain (pinched nerves, sciatica)
• Injury in forms of muscle strains and ligaments sprains: Inflammation and chemicals from damaged cells can sensitize pain receptors, leading to pain

Pain and Medications

• Corticosteroids: are lipid-soluble drugs that block inflammation by stopping arachidonic acid so they're commonly used to treat asthma and reduce mucus production in airways
• Aspirin & NSAIDs: block prostaglandin and thromboxane which and helps reduce pain, inflammation, and fever

Pain and Medications: COX Inhibitors

• COX medications (NSAIDs) and are are often used for persistent pain as they work by reducing prostaglandins which helps decrease pain, inflammation, and fever.
• COX-1 is found in all tissue and that helps with normal body functions compared to COX-2 being triggered by inflammation.
• COx inhibitors bind reversibly to these enzyme to reduce pain

Microbes Basics

• Definition: Invisible without microscope
• Ubiquity: Found everywhere there is water and/or earth
• Types: bacteria, fungi, viruses, protozoa, and others
• Importance:
• Beneficial: food production, vitamin synthesis, and drug production
• Harmful: Pathogenic, disease-causing, or food spoilage

Normal Flora

• Definition: Resident microorganism found in specific body sites
• Role:
• Prevent invasion by harmful organism
• Aid in vitamin K production and digestion in large intestine
• Opportunistic Pathogens: Normally harmless, but may cause disease if moved to other sites.
• Sterile sites: blood and bladder typically lack normal flora

Bacteria, Structure & Reproduction

• Structure: Simple, unicellular, prokaryotic (no nuclear membrane)
• Reproduction: Binary fission (splitting into 2 equal parts)
• Environment: thrives in moist, dark environment

Bacteria Nomenclature

• Scientific names consists of genus and species
• Names often described shape, color, or habitat
• Shape
• Coccus: spherical
• Bacillus: Rod-shaped
• Spiral: Corkscrew or curved
• Cell Wall
• Composed of peptidoglycan
• Differentiates bacteria based on cell wall composition for a gram stain
• gram-positive: Thick peptidoglycan layer with an outer membrane containing endotoxins
• Controls movement on nutrients and contains enzymes for ATP production in the Plasma membrane.
• Endospores: Dormant, resistant structures for harsh condition survival
• Capsule/slime layer: Protective outer layer that can contribute to violence
• Toxins and enzymes:Exotoxins: interfere with nerve conduction or cause vomiting through production of gram-positive bacteria.
• Endotoxins: causes fever or endotoxic shock and is found in gram-negative bacteria, released upon cell death.
• Enzymes: Some bacteria produce enzymes that damage host tissue

Viruses

• Structure: Acellular, consisting of genetic material (DNA or RNA) surrounded by a protein coat (capsid),
• Reproduction: Obligate intracellular parasites needing host cell to replicate which involves through attachment, penetration, replication.
• Dormancy: that Viruses can remain dormant in host cells before the body reactivates.
• Mutation: viruses mutate frequently that can may immunity challenging
• Cellular Effects
• Inhibit host cell DNA/RNA/protein synthesis
• Disrupt lysosomal membranes
• Prompt apoptosis or cancerous transformation
• Cause secondary bacterial infections

Fungi

• Types: yeast and molds
• Habitat: Found on animals, plants, humans, and food
• Examples
• Candida: causes yeast infection
• Tinea pedis: causes athletes foots

Protozoa

• Structure: Unicellular eukaryotes and Movement: via pseudopods (false feet), flagella, or cilia
• Lifestyle: can be solitary, parasitic, or feed on dead organic matter and move using amoebas and protozoa
• Microbes are diverse and role play significant roles in both beneficial and harmful processes
• Bacteria are shape, wall type, gram stain, an and endospore formation based on bacterial class
• Viruses are acellular, so they require host cells to replicate and can cause significant cellular damage to the host.
• Fungi includes yeasts and molds, while those mobile and protozoa are mobile are Unicellular eukaryotes
• Normal Flora are which are essential for health but can become pathogenic under certain conditions

Development of Infection

• Incubation: Time between germ and sign appearance and microbes reproducing
• Prodromal: Early like fatigue and early-mildness
• Acute: period for peak symptoms
• Recovery: Symptoms subside, with the agent being transmittable in convalescence period
• Chronic infection: Infection not fully being gone, with mile, in septicaemia is life threatening
• Resistance decreasing factors include age, genetics, deficiency, malnutrition, disease, ,or, and inflammatory

Virulence, agent transmission and means of contamination prevention

• Invasive, toxin, large numbers and mutations
• Agent transmission requires infectious agents, reservoirs to multiply in, agent exit, mode to spread itself , agent entry and must host be susceptible
• Transmission modes from infections agents are through direct physical, intermediate contact with bad food, vector ,droplet or from healthcare
• Prevention of agent in the chain of contamination requires locate, the portal exing,modes, the portal the host is in
• Microbes control requires sterilization, disinfection, growth prevention, bacteria reduction, an fungicidal

Bacterial infection and host immune responses

• Host immune responses includes stages, factors and sterilizations
• Bacterial infection in the skin involves the overview of skin barrier against infections
• Skin manifestation of disorders involves lesions and pigments

Skin Pigmentary Disorders

• Vitiligo
• White patches due to loss of melanocytes
• Autoimmune and genetic factors may play a role
• Albinism
• Genetic disorder with lack of melanin production
• Pale skin, white/yellow hair, and light colored eyes
• Melasma
• Darkened macule’s in the face
• Common in women, especially during pregnancy or with oral contraceptives

Fungal infection

• Tinea (ringworm)
• Superficial fungal infection affecting skin, hair, and nails
• Example: Tinea unguium: nails

Bacterial Infection

• Impetigo
• Superficial infection caused by staphylococcus or streptococcus
• Highly contagious, common in children Symptoms: honey-colored crust on the skin
• Acne vulgaris: *Example: whiteheads, papules
• Boils that is inflamed by the oil in hair and can get severe without treatment
• Cellulitis that causes the skin to swell but be careful for its necrosis
• All is infection that have to do with bacterias
• Verrucae (warts): Caused by strains of the human papillomavirus (HPV).
• Bacterial infection are a key required needed.

Viral Infection

• Herpes Simplex that causes cold sores and spread through bodily contact
• Shingles is cause as re activation of chickenbox virus
• Viral infections are caused by viruses that requires antiviral in order to treat or to prevent in worsening stages
• Impetigo is a bacterial skin infections
• A red itch is when arthropoids infrect such as scabies
• Allergens affects causing hives
• Disorders: Psoriasis and burns
• There some wounds that affect the body such cause by pressure called decubitus ulcers
• Key things to remember will be to use agents when required during impetigo and viruses etc ,

Common infectious disease

• Sars covid the agent of coronoavirus
• Influenza infection as well as the viral infection has symptoms such as body arches etc...
• Measles has symptoms or white spots
• Other viral infection that has to be known are mumps and Rubella
• Smallpox causes flu like and scarring
• Chickenpox/varicella which is viral infection that contagious and has fever
• Gastroenteritis that causes diarrhea requires immediate treatment
• Hepatitis type viral infections
• Pertussis also known as whooping cough is bacterial infection
• The 6 most known bacterial infections are diphtheria, Strep Throat, E-coli . difficile

Autoimmune response

• The immune system works well with the body by protecting the body from foreign invaders and to help the cells recover in any kind of physical wound or physical invader for example to treat a wound
• Hypersensitivity is the immune that overreacts to substance
• Allergies occur caused by the triggered of food and pollen (an overeaction)
• Autoimmunity happens when the immune system attacks ones body in any way due to system that are sensitive
• the immune system reacts to substances from another person (like an organ transplant

Immune reaction and Types

• The immune is split in time and immunity cells
• Immediate actions occurs by antibodies faster then longer
• The 4 types of hypersensitivity are caused by immune complexes,antibodies
• Fast reactions are allergic reactions to ig 1
• Immediate allergic is caused by igE, basophills
• When the igE are allergic to skin caused to to skin issues or genetic
• The common allergens caused by allergic reactions like food ,skin
• Severe cause be anaphylaxis and a severe issue that occurs if skin is not treated or relieved to the best possible.

Hypersensitivity and types

• A few of the common conditions that we know that allergies can cause allergic rhinitis , or anaphlaxis
• Igm and igG reacts can lead cell distraction
• IgE depends on the target cells that effects the complexes
• Those are type of allergic reaction

Serum sickness

• Is triggered after antibodies reaction during after the food and body react and Immune complexes form between the allergen and IgM/IgG antibodies
• symptoms include Edema (face, neck, joints), rashes, itchiness, and fever and Symptoms usually resolve within a few days but can worsen with prolonged exposure to the antigen
• To treatment this you should stop the usage of allergen causing food or item which we can use antihistamines.

Hypersensitivity and cause from allergens

• Is where blood vessels are reactive to cold and stressful factors
• is Mediated by T-cells and cytotoxic cells release cytokines, attracting macrophages and causing inflammation.
• Contact dermatitis, lung inflammation and allergic contact dermatitis are a source of problems
• Causes on skin from skin contact
• Causes is skin exposure to poison or skin topical substance

Latex Allergy

• Has 2 types of reactions

• Type 1

• Immediate reaction to latex proteins which can Cause anaphylaxis

• Type IV: Delayed and causes contact rashes

TIssue repair

• Inflammatory response is begining at the time of injury to clot the healing.

Process and Activity of healing

• Clotting is initiated to stop bleeding Arterioles dilate while allowing capillary permeability increase, allowing plasma to leak those are in cellurlar activity

• Begins 3-4 days, post injury, with those cellular ones creating strength to the muscles.

• Key processes in those times

• peaks at 5-7 days and continues through maturations phases 6-8 weeks.

• Maturation Phase as well collagen are created and its takes months .

Factors that wound and effects the healing

• Malnutrition (lowers healing levels).
• Blood flow, (ischemic wounds are prone to infections)
• Impared for inflammation (corticosteriod effects)
• And there some factors depending on the animals or people during bite or wounds
• Collagen has very critical formation which are key outcomes which are proper.
• There are proper wounds to occur that can may happen with the 3 phases