#8 What is a disease? Concepts and applications Flashcards
define disease
Disease: a condition that disturbs the normal functioning of the body with symptoms and causes.
Disease has been traditionally classified as four types. List them
- Infectious
- Degenerative
- Genetic
- By organ systems
To provide a structure that reflects both evolutionary causes and proximate mechanisms of disease, disease can be classified into 7 distinct categories. List the categories and give an example for each.
- Genetic disease – ex: down syndrome, Huntington’s, Duchene’s
- Environmental disease – infections, starvation, dehydration, toxins pollutants
- Byproduct of defense system – ex: autoimmune, allergies, asthma
- Diseases of homeostasis – ex: T2DM, obesity, atherosclerosis, hypertension
- Diseases of maintenance – aging diseases
- Diseases resulting in developmental problems – trisomy 18 and 21
- Diseases caused by disruptions of equilibria – diseases of pregnancy
What is Crohn’s disease? What is ulcerative colitis? What are the
symptoms of Crohn’s disease?
Crohn and Ulcerative colitis are inflammatory bowel diseases.
Crohn’s disease:
- Affects anywhere in GI tract
- Immune related disease triggered by pathogen in GI tract
- Symptoms: abdominal pain, diarrhea (and blood in stool), and weight loss, malabsorption
- Due to deregulation of the immune response to intestinal microbiota.
Ulcerative colitis:
- only affects the large intestine
- autoimmune disease triggered by self
What are the mechanistic and evolutionary explanations for Crohn’s disease?
Mechanistic: GWAS that homozygous mutants in the NOD2 gene have a 17-fold greater risk of Crohn’s disease and that heterozygous mutants have a 2.4-fold greater risk. (NOD2 protein are in the cytoplasm of intestinal epithelial cells and in macrophages which regulate innate immune response)
Evolutionary: have coevolved with microbiota but this new environment is a mismatch from where we evolved in so diseases arise
Briefly describe a treatment for Crohn’s disease.
By putting the pig whipworm (Trichuris suis) into the body because Helminths diminish immune responsiveness in naturally colonized humans and reduce inflammation which can prevent or alleviate Crohn’s.
At the molecular level, what are the three general steps leading to inflammation?
- GI cell presents an antigen for an infectious molecule which bonds with T helper cells
- T helper cells release cytokines
- Cytokines attract macrophages
- Macrophages release more inflammatory cells (proteases, free radicals, platelet activating factor)
What are two types of genetic causes of disease?
Defects: like genetic mutations from category 1
Predisposition: often polygenic and have environmental interactions
What are two types of environmental causes of disease?
Environmental catastrophes: accidents, infection from virulent pathogens like Ebola
Accumulative environmental affects: includes carcinogens
Can disease be explained by genetic or environmental causation alone?
Explain your answer.
No, because many genetic causes are polygenic and environmental causation can be accumulative so the combination of these effects increase the likelihood of developing a disease. Factors alone could cause a disease but usually it’s a combination of factors.
What is homeostasis? What is maintenance? What is defense? Explain how they are different from one another.
Homeostasis: is the stability of key regulated variables in cells, tissues and organisms.
Maintenance mechanisms: sustain the normal functioning of cells and tissues by preventing, repairing, and reducing malfunctions.
Defense mechanisms: protect from specific hostile environmental factors —perturbations that exceed the homeostatic capacity of the organism.
What are two types of maintenance mechanisms. What is an example of each?
constitutive: Maintenance in supporting normal developmental and physiological processes
example is removing damaged proteins and lipids.
Inducible: promote survival from harsh environments. Example is hibernation.
List three environmental factors that can affect reproductive success.
Nutrition, toxins, disease
Some environmental challenges that elicit inducible defense responses. Describe three examples of environmental challenges and the corresponding defense response.
When a hostile environmental factor is frequently encountered inducible responses are formed. Some environmental challenges are starvation, dehydration, cold, and hot temperatures, hypoxia, predators, injuries, toxins and pathogens.
Starvation causes a shift in glucose allocation so that the brain and other high-priority tissue continue to consume glucose (independent of insulin).
Cold stress stimulates the hypothalamus to activate antagonistic skeletal muscles, inducing shivering thermogenesis. The body also reduces heat loss by decreasing cutaneous circulation to the skin and extremities, and heat is retained in the body core.
Hypoxia: The short-term response to hypoxia is hyperventilation and increased allocation of oxygenated blood to the brain and heart. The longer-term acclimation to reduced oxygen tension at high altitudes is mediated by increased red blood cell numbers
Defense plays an essential role in the survival of multicellular organisms. Explain how defense by the immune system can lead to disease.
Expression of defenses can be excessive in intensity or duration, mistargeted, or activated inappropriately (at wrong time/place) resulting in pathological consequences.
