Homeostasis and the Endocrine System Flashcards
Functions of the endocrine system
Coordinates and directs activity of body cells - reproduction - growth and development - electrolyte and water balance - nutrient balance - metabolism - mobilisation of body defences
What is the difference between an endocrine and exocrine gland?
Endocrine glands have no ducts, and release hormones directly into the bloodstream.
What are hormones?
Most hormones are proteins (amino acid based, water soluble, bind to receptors on cell membranes. Some (sex hormones, aldosterone, cortisol) are steroid, fat soluble, diffuse across the cell membrane to bind with receptors within the cell Hormones are released into the blood stream Hormones exert their effect when they bind to the relevant receptors Hormones regulate body functions. Hormone secretion is usually regulated by negative feedback mechanisms.
What are the major endocrine glands?
- Hypothalamus (control centre) - hunger, thirst, sleep/wake cycle - Pituitary gland (master endocrine gland) - Pineal gland - produces melatonin - Thyroid gland - metabolism - Parathyroid glands - embedded in the thyroid, detects low calcium - Thymus - immunity - Adrenal glands - aldosterone and stress - Pancreas - digestive enzymes and blood glucose - Ovaries/testes - sex hormones
Growth Hormone
- released by the pituitary - peaks in adolescence - mainly targets epiphyseal plates in bones and skeletal muscles. - Giantism or gigantism occurs when the growth hormone doesn’t dwindle after adolescence. - Acromegaly (pituitary adenoma) is a pituitary tumour that causes bony growths on the face, hands and feet (eg Andre the Giant)
What roles does the pancreas play?
The pancreas is both an endocrine and exocrine gland. As an exocrine gland, it secretes digestive enzymes via a duct into the duodenum. As an endocrine gland, it releases insulin (beta cells) and glucagon (alpha cells) to regulate blood glucose levels.
How are blood glucose levels regulated?
- normal range for blood glucose is between 4 and 8mmol/L. - increased sugar intake = increased blood glucose. Pancreas releases insulin. Cells take in glucose. Excess glucose is converted into glycogen or fat. Blood glucose levels return to normal range - fasting = decreased blood glucose. Pancreas releases glucagon. Glucagon stimulates liver to convert glycogen into glucose. Blood glucose levels return to normal range.
What are the signs and symptoms of Type I Diabetes Mellitis?
- Diabetes is a chronic metabolic disorder - Type 1 is an autoimmune disorder where the beta cells of the islets of Langerhans have been destroyed, so the body doesn’t produce any insulin - This causes Hyperglycaemia (excess blood glucose) - Glucosuria (glucose in urine) - Polyuria (excessive urination) - Polydipsia (excessive thirst) - Polyphagia (excessive hunger) - Ketoacidosis - Weight loss - Fatigue
What is ketoacidosis, and how does it relate to diabetes?
- because tissues can’t access the blood glucose, they metabolise fatty acids for energy - a byproduct of this metabolisation in ketone bodies, which are acidic - this lowers the pH of the blood, and can be fatal - the breath and urine of people with ketoacidosis smell of fruity acetone
What is hypoglycaemia?
- Low blood sugar - caused by excess insulin, which can happen with: - uncontrolled diabetes - insulin overdose - pancreatic tumour - As the brain relies on blood glucose, low blood glucose can cause: - cerebral changes - disorientation - convulsions - coma - death
Signs and symptoms of Type II DM?
- most common form of Diabetes (~90-95%) - increasing issue as linked to obesity - insulin is produced, but is less effective (insulin resistance) - can be managed solely by diet and exercise, or may need medication - symptoms the same as Type I except weight gain rather than weight loss
What is gestational diabetes
- the mother’s blood brings extra glucose to the fetus - the fetus makes more insulin to handle the excess glucose - extra glucose gets stored as fat and fetus becomes larger than normal - important to avoid, as half of mothers with gestational diabetes go on to develop Type II later in life
What is the function of the thyroid gland?
- regulates metabolisom in the tissues - releases thyroid hormones T4 (thyroxine) and T3 - the pituitary gland releases thyroid-stimulating hormones - the thyroid needs iodine to create thyroxine - hypo- (if caused by iodine deficiency) and hyper thyroidism both cause goitres (swollen thyroid). In hypothyroidism, these protrude out from the neck. In hyperthyroidism, they more often swell internally and can compress the trachea or oesophagus
What is hypothyroidism?
- inactivity of the thyroid gland - lack of thyroxine - possibly caused by lack of iodine - can also be caused by inflammation of the thyroid (Hashimoto’s disease) - metabolism and digestive function slows down - can be reversed in adults by administering thyroxine - hypothyroidism in infants causes cretinism (mental retardation). Blood samples are taken in maternity wards to check levels
What is Hyperthyroidism?
- Also known as thyrotoicosis or Graves diseases - often fatal in infants - symptoms include overactive digestive system, sweats, weight loss, tremors, muscle wastage, in-growing goitres, increased heart rate and exopthalmos (bulging eyes)
