Lecture 8 - Endocrine System Part 2 Flashcards
What are the effects of growth hormone?
Acts on the liver to promote the release of somatomedins e.g. Insulin like Growth Factors (IGF’s)
These stimulate tissue growth and increase protein synthesis
GH acts directly on tissues to stimulate cell division in epithelial and connective tissue
Triglyceride breakdown in adipocytes
Liver glycogen breakdown
Outline ADH
Released by osmoreceptors which detect water concn - they retain fluid be reabsorbing water at the kidneys
What is the pineal gland?
Contains neurons that are collaterals from the visual pathways so is effected by light detection
Pinealocytes secrete melatonin - low in the daylight
Function of melatonin - influences circadian rhythms and antioxidant - reduces the effects of free radicals
What is the thyroid gland?
Anterior to the thyroid cartilage of larynx
Two lobes connected by narrow isthmus
Stores and secretes thyroid hormone (T4) and triiodothyronine (T3)
T3 contains iodine
Aid membrane health as they increase sodium potassium ATPase production
What are the effects of thyroid hormones?
Increase oxygen and energy consumption
Increase HR
Increase sensitivity to sympathetic stimulation
Stimulate rbc formation
Affects activity of other endocrine tissues
Increases bone turnover
What are thyroid follicles?
Hollow spheres lined by cuboidal epithelium, surrounded by capillaries
Contains colloid - protein rich fluid
Follicle cells synthesis tyrosine rich thyroglobulin
Iodine incorporated to form T4 and T3 - T3 more bio active
Outline iodine deficiency
Causes a swelling of the thyroid gland as they get bigger to try and capture more iodine to make thyroid hormones
What are C cells?
Produce calcitonin
Important in calcium homeostasis
Reduces serum calcium
- Deposition in bone
- Increased excretion by kidney
Outline the role of calcitonin in regulation of calcium ion concn?
Rising Ca levels in blood
Thyroid gland produces calcitonin
Increased excretion of Ca by kidneys and deposition in bone
Homeostasis restored
What is the role of PTH in regulation of calcium ion concn?
Falling Ca levels in blood
Parathyroid glands secrete PTH
Increased reabsorption of calcium in kidneys
Ca released from bone
Increased calcitrol production causes Ca2+ absorption by digestive system
Homeostasis restored
What are the parathyroid glands?
Small glands on posterior of thyroid
Chief cells produce parathyroid hormone (PTH)
PTH is released to increase serum calcium when levels drop
Outline the adrenal glands
Located above the kidneys
Consists of the capsule
Cortex - steroid hormones e.g. glucocorticoids
Medulla - catecholamines
Outline the structure of the adrenal gland
Adrenal medulla - catecholamines - fight or flight response increased hr and blood glucose
Cortex
Zona reticularis - Androgens (steroid hormones) anabolic effects
Zona fasciculata - glucocorticoids e.g. cortisol, fat and protein catabolism, anti inflammatory
Zona glomerulosa - Mineralocorticoids e.g. aldosterone - electrolytes
Capsule
Outline the regulation of blood pressure and volume
Falling blood pressure
Lower renal blood flow and O2
Erythropoietin and Renin released
This increases rbc production
Renin activates angiotensinogen which activates angiotensin 1 and 2
Aldosterone and ADH are secreted and thirst is stimulated increasing fluid intake and retention
These both rise blood pressure and volume
Outline the pancreatic islet and acini
Pancreatic acini - exocrine cells that secrete into the digestive tract
Pancreatic islet of langerhans - Alpha cells - produce glucagon (increases blood glucose)
Beta cells - Produce insulin (lower blood glucose)
Outline the role of insulin in blood glucose regulation
Rising blood glucose levels, insulin secreted
Increased rate of glucose transport into target cells, glucose utilisation and ATP generation,
conversion of glucose to glycogen,
protein synthesis,
triglyceride synthesis in adipose tissue
Glucose levels decreased
Outline the role of glucagon in blood glucose regulation
Falling blood glucose levels
Glucagon secreted
Increased breakdown of glycogen to glucose in liver and muscle
Breakdown of fat to fatty acids in adipose tissue
Synthesis and release of glucose by liver
Glucose levels increased
What is diabetes mellitus?
Abnormally high blood glucose (hyperglycaemia)
Untreated - results in
Kidney damage
Retinal damage
Peripheral nerve damage
Increased CV disease risk
What are the types of diabetes?
Type 1 - insulin dependant
5-10% of cases diagnosed in childhood
Pancreatic insulin production inadequate
Injections required
Type 2 - non insulin dependent
Diagnosed in older age
Reduced tissue response to insulin
Managed with diet and exercise
What are the patterns of hormonal interaction?
Antagonistic effects e.g. PTH and calcitonin
Synergistic effect e.g. GH and glucocorticoids
Permissive effects - one hormone for another to produce effect
Integrative effects - Hormones produce different but complementary results
What are the hormones needed for normal growth?
GH - protein synthesis
Thyroid hormones - nervous system development
Insulin - Supply of energy and nutrients
PTH and calcitriol - Ca absorption/ deposition in bones
Reproductive hormones - Cell growth and differentiation
Outline the alarm phase of general adaptation syndrome (fight or flight)
- Mobilisation of glucose reserves
- Changes in circulation
- Increases in HR and respiratory rates
- Increased energy use by all cells
Outline the resistance phase of the general adaptation syndrome (long term metabolic adjustments)
- Mobilisation of remaining energy reserves - lipids released by adipose tissue
- Conservation of glucose - peripheral tissue break down lipids for energy
- Elevation of blood glucose concn - liver gluconeogenesis
- Conservation of salts and water, loss of K+ and H+
Outline the exhaustion phase of general adaptation syndrome (collapse of vital systems)
Causes may include - Exhaustion of lipid reserves
Inability to produce glucocorticoids
Failure of electrolyte balance
Cumulative structural or functional damage to vital organs
