Regulation and Disruption Flashcards
Homeostasis
the maintenance of a constant, optimal internal environment despite changes in the external environment
Homeostatic mechanisms
controlled by the nervous and endocrine system; the nervous system sends electrical impulses, endocrine system secretes hormones to counteract the stimulus
Negative Feedback Loop
The response reduces or eliminates the stimulus causing the effect
Eg. Dropping body temperature
Positive Feedback Loop
The response intensifies the stimulus
Dynamic Equilibrium
Fluctuations around the set point, controlled by homeostasis
Set Point
The optimum level around which levels fluctuate
Location of thermoreceptors
Thermoreceptors are found within the skin and mucous membrane (peripheral thermoreceptors) and in the hypothalamus and vital organs (central thermoreceptors)
Function of peripheral thermoreceptors
provide info about the external environment: cold and hot receptors
Function of central thermoreceptors
detect changes in internal temperatures
Heat Exhaustion
Caused by dehydration and continuous vasodilation, causing low blood pressure.
Person may collapse, but internal body temperature remains normal
Heat Stroke
Caused by high temperatures and humidity – body temperature increases past 42˚C.
Causes regulatory mechanisms to cease
Hypothermia
Core temperature falling below 33˚C; causes metabolic rate to slow, decreased heat production
Heat Transfer
Conduction, radiation, evaporation, convection
Intracellular fluid
found inside the cells
Extracellular fluid
outside the cells, including blood plasma
Intercellular Fluid
between cells (interstitial fluid)
Plasma
fluid within the blood stream
Lymph
any fluid found within the lymph vessels
Lyphedema
Lymphatic obstruction causing excess extracellular fluid to collect outside the lymph vessels
Dehydration
Water loss exceeds water intake through vomiting, sweating, or diarrhoea
Severe thirst, low blood pressure, dizziness, headache
Water Intoxification
Dilation of bodily fluids, leading to cells taking in more water by osmosis
Effect of Alcohol on Water Regulation
Inhibits ADH production – decreased water reabsorption in the collecting duct
Insulin
produced by the beta cells in the pancreas, and decreases blood glucose levels
Ways Insulin lowers BGL
Accelerates the transport of glucose from blood to cells, conversion of glucose to glycogen, stimulates conversion of glucose into adipose tissue, increase in protein synthesis
Glucagon
produced in the alpha cells in the pancreas, and increases blood glucose levels
Ways glucagon increases BGL
Stimulates glycogenolysis
Adrenaline and Cortisol (Blood Sugar regulation)
Stimulates glycogenolysis
Stimulates gluconeogenesis
Glycogenesis
Glucose to glycogen
Glycogenolysis
Glycogen to glucose
Gluconeogenesis
Conversion of non-glucose sources into glycogen (deamination)
Ions that regulate gas concentrations
Concentration of oxygen, carbon dioxide and hydrogen ions (pH) regulate breathing
Regulation of oxygen
Extremely low concentrations of oxygen are detected by the aortic and carotid bodies, as well as the medulla; these send a nerve impulse to the respiratory centre in the medulla, which then stimulates the intercostals and diaphragm to contract
Regulation of carbon dioxide
A relatively small increase in carbon dioxide concentration can stimulate an increase in breathing rate and depth
An increase in CO2 concentrations leads to an increase in hydrogen ion concentration
This is detected by peripheral and central chemoreceptors; medulla is most sensitive to CO2 changes
Regulation of hydrogen ions
As hydrogen ions increase, blood pH decreases
Decrease in pH is detected by the peripheral chemoreceptors
Breathing structures
To increase breathing rate, both the intercostal muscles and the diaphragm are stimulated to contract via the intercostal nerve and the phrenic nerve respectively
Danger of hyperventilation before diving
Reduced levels of CO2 in the blood stream prior to diving means the urge to breath won’t be triggered at the right time. Decreased O2 levels mean the person will blackout whilst underwater, causing them to inhale whilst under the water
Disruptions to homeostasis
Hormonal disruptions and disease
Diabetes
Blood sugar levels are regulated by insulin and glucagon; either doesn’t secrete enough insulin, or cells are resistant to the effects of insulin
Type 1 Diabetes
Insulin dependent/ juvenile diabetes
Autoimmune disease – leucocytes attack beta cells
Insulin is injected
Type 2 Diabetes
Adult onset / non-insulin dependent
Insulin in produced, but the cells don’t respond to it – lifestyle disease
- Lack of physical disease
Lifestyle factors contributing to type 2 diabetes
Lack of physical exercise, overweight / obese, diet high in fat, sugar and salt, low in fibre, high blood pressure, high blood cholesterol, smoking
Hyperthyroidism (Grave’s Disease)
Excessive thyroxine
Genetic predisposition; rapid heart rate, weight loss, increased appetite, fatigue, sweating, anxiety, protruding eyeballs
Treatment of hyperthyroidism
Drugs blocking thyroid’s use of iodine
Surgery
Radioactive Iodine
Hypothyrodism
Too little thyroxine, can be caused by iodine deficiency
Thyroid may enlarge, causing a goitre
Slow heart rate, weight gain, fatigue, intolerance to cold, swelling of the face
Pregnant women with an iodine deficiency can give birth to mentally and physically handicapped babies (cretinism)
Hashimoto’s Disease
Autoimmune disease - leucocytes attack thyroid cells
Treatment of hypothyroidism
Either supplementation with iodine, thyroid hormone replacement therapy
