The Endocrine System Flashcards
What hormones are lipophilic and can cross membranes?
Steroid hormones
(Vice versa)
Non-steroid, non lipophilic
Give an example of a short chain non-steroid hormone
Antidiuretic hormone
Give an example of a long chain non-steroid hormone
Human growth hormone, insulin, glucagon.
Where in the cell are pre-pro-hormones activated? How does activation occur.
The golgi apparatus.
Pre-pro-hormones are broken down and folded into an active quaternary structure.
How do second messengers work?
Penetrate the cell, enter the nucleus and induce translation and transcription.
What is up regulation?
Down regulation
Increases sensitivity, when there are more membrane receptors present.
(Vice versa for down regulation.)
What is hyperfunction?
Excess production and secretion of a hormone. Caused by upregulation.
What is hypofunction?
Decreased production and secretion. Caused by down regulation or lack of receptor function.
What are the functions of the hypothalamus?
Thermoregulation, hormone secretion, circadian rhythms (day/night cycles over 24 hour period) motivation (thirst, sexual behaviour) and emotions.
Name the two types of hormone secretions.
Primary: Acts directly.
Trophic: Cascade event that then produces the hormone..
Describe the process of thermoregulation.
Core body temperature changes, thermoreceptors detect the change, compared to a set point where it establishes if the body is too hot/cold, effectors then either increase heat production or decrease heat production.
What is adenohypophysis?
The interaction between the hypothalamus and the anterior pituitary gland.
Hormones from the hypothalamus are released and passed to the pituitary gland via blood vessels.
What is neurohypophysis?
The interaction between the hypothalamus and the posterior pituitary gland.
Hormones produced by the hypothalamus are passed to the pituitary gland via nerve axons.
Trophic hormones tend to be..
Inhibiting or releasing (i.e. controlling actions)
What two hormones are produced in the nuclei of the hypothalamus?
Antidiuretic Hormone and Oxytocin
How many nuclei has the hypothalamus got?
2
What hormones does the thyroid hormone secrete?
T3 & T4 (thyroxine)
Calcitonin.
What conditions are caused by hypothyroidism?
Cretinism and myxoedema.
Myxoedema associated with alopecia and can be reversed by introducing the thyroid hormone.
What conditions are caused by hyperthyroidism?
Grave’s disease. Autoimmune disease. Causes exophthalmos.
What is the purpose of the parathyroid hormone?
Regulate blood calcium.
What controls insulin secretion?
Glucose dependant insulinotropic peptide, vagus nerve activity.
Name the actions of glucagon:
Glycogenolysis and gluconeogenesis in the liver
What controls glucagon secretion?
Cholecystokinin.
Autonomic nerve activity.
What characterises type 1 diabetes?
Reduced insulin secretion due to destruction of beta cells.
What characterises type 2 diabetes?
Decreased sensitivity to insulin. Common in overweight individuals.
What hormones do the adrenal glands secrete? Name them.
Cortex hormones: Corticosteroids. Aldosterone, cortisol and androgens.
What type of cortex hormone is aldosterone?
Mineralocorticoids
What type of cortex hormone is cortisol?
Glucocorticoid
What is the action of cortisol?
Metabolic effects.
Anti-inflammatory.
What is the action of aldosterone?
Promotes reabsorption of sodium and water in the kidney.
Increases hydrogen and potassium excretion.
What type of cortex hormone is androgen?
Gonadocorticoid.
What is the action of the androgens?
Growth and sexual characteristics.
Pubertal growth.
What does the adrenal medulla produce?
Adrenaline.
What is the adrenal medulla controlled by?
Pre-ganglionic sympathetic nerves.
What does the endocrine response to stress depend on?
Duration, severity of the stimuli and the effectiveness of the response.
Name the stages of the general Adaptation Syndrome (stress).
Alarm, resistance and exhaustion.
What are the components of an alarm response (stress)?
Neural and hormonal.
What is the neurological alarm response controlled by (stress)?
Sympathetic nerves.
What happens in the neurological response (stress)?
Increased cardiac output: (Increased heart rate and ventricular contractility)
Redistribution of cardiac: output. (Blood redirected from gut to muscle)
Glycogen breakdown.
Adrenal release.
What hormones are released in the hormonal component?
Adrenaline and glucocorticoids (cortisol)
What is the function of adrenaline?
Prolongs the action of sympathetic nerves.
What are the actions of glucocorticoids?
Increased energy production from glucose. Gluconeogenesis of amino acids and fats.
Anti-inflammatory.
Immunosuppression.
What is the function of corticosteroid therapy?
Suppresses the body’s natural response, corticotropin and adrenocorticotropin hormone.
What happens in long term use of corticosteroids?
Disrupts the normal stress control mechanisms.
What is stress analgesia?
How does it work?
Pain diminished during physical stress.
Suppression of nociceptors and pain.
What occurs in the adaptation phase?
Response effectively removes the stressor.
What occurs if the individual fails to adapt?
Peptic ulcers, adrenal failure, immunosuppression and Cyclic vomiting Syndrome.
What is a type A individual?
Competitive, prone to high blood pressure and cardiac disease.
What is a type B individual?
Relaxed and less impatient.
What hormones achieve calcium homeostasis?
Parathyroid hormone, calcitonin and vitamin D.
What hormone is released in response to low plasma calcium?
The parathyroid hormone.
How does the parathyroid hormone increase plasma calcium?
Increased resorption of bone.
Increased calcium resorption in the kidney and decreased phosphate resorption.
Increased calcium uptake from the kidneys. (assisted by vitamin D)
What hormone is secreted in response to high plasma calcium?
Calcitonin.
How does Calcitonin decrease plasma calcium?
Increasing bone formation.
Decreasing calcium resorption in the kidney.
What are the sources of vitamin D?
Diet and 7-dehydrocholesterol synthesised in the skin.
What hormone regulated the process of vitamin D formation?
The parathyroid hormone.
What are the functions of vitamin D?
Calcium absorption in the intestine.
Calcium and phosphate retention in the kidney.
Calcium and phosphate release in bone.
What hormones promote bone formation and increase bone mass?
Calcitonin.
Growth hormone.
Insulin.
Oestrogen and Testosterone.
What hormones promote bone resorption and decrease bone mass?
Cortisol.
Parathyroid hormone.
Thyroid hormone.
What is the function of osteoblasts?
Secrete and synthesis collagen to forma matrix.
Matrix (osteoid) can be mineralised by calcium.
What is the function of osteocytes?
Trapped cells in bone matrix.
What is the function of osteoclasts?
Resorb bone. (Derived from macrophages)
In bone remodelling; what hormone produces enzymes that encourages the breakdown of bone?
The parathyroid hormone.
What is alkalosis?
A reduction in calcium.
What is hypocalcaemic tetany?
Decrease in calcium causes muscle excitability. Muscle spasms. ‘pins and needles’
Lack of vitamin D results in what disorder? (adult and child)
Child: Rickets.
Adult: Osteomalacia.
What is osteoporosis?
Bone lacks mass and density.
Why are woman more likely to suffer osteoporosis earlier than men?
Menopause.
What is osteopetrosis?
Increased bone mass and density.
Reduced blood supply.
More likely to suffer from fractures as bone loses its flexibility.
Greater effects on the mandible.
Define shock.
Decreased blood volume results in fallen blood pressure which prevents nutrients reaching cells.
State the 4 physiological responses to blood loss. What occurs at each stage?
Immediate: Stop the bleeding.
Short: Restore blood pressure.
Medium: Restore fluid volume.
Long: Replace blood constituents.
What occurs in the immediate response to stop blood loss? Name the 3 responses.
Haemostasis.
Vascular, platelet and plasma response (coagulation).
The immediate vascular has 2 further responses; what are they?
Myogenic: Contraction of blood vessels when intravascular pressure increases.
Hormone: Adrenaline = vasoconstriction.
Describe the steps that occur in the platelet response.
Damaged blood vessel creates turbulent flow.
Platelets come into contact with the vessel wall.
Platelets adhere and clump to the wall (aggregation)
Chemicals are released that encourage further aggregation.
Plug formed.
In what type of blood vessels are platelet response effective in?
Arterioles and venules. (smaller vessels)
What is the function of Thromboxane A2?
Vasoconstrictor.
What is another term for the plasma response?
Coagulation (clotting)
What vitamin is essential for clotting?
Vitamin K
What coagulation pathway initiates a clot after an injury?
Extrinsic pathway.
What coagulation pathway maintains the clotting process?
Intrinsic pathway.
What is fibrinolysis?
Dissolving a blood clot.
What enzyme assists the breakdown of a clot?
Plasmin.
In the short term response; what triggers the compensatory mechanisms of low blood volume and pressure?
Arterial baroreceptors.
What are baroreceptor reflexes mediated by?
Sympathetic nervous system.
What occurs in the medium term response?
Interstitial fluid shifted into blood vessels.
Decreasing fluid loss in the kidneys.
What occurs in the long term response?
Blood cells (esp red) replaced by erythropoiesis. Regulated by erythropoietin.
Name the three types of shock?
Hypovolaemic.
Low resistance.
Cariogenic.
What causes Hypovolaemic shock?
Reduced extracellular fluid, haemorrhage, burns, diarrhoea.
What causes low resistance shock?
Widespread vasodilation.
e.g. anaphylactic.
What causes cariogenic shock?
Heart failing to pump blood. e.g. stroke.
In terms of water and electrolytes; what is the only factor in water balance that is under homeostatic control?
Urinary excretion.
What are electrolytes controlled by?
The kidneys.
What is sodium retention controlled by? How does it work?
Renin-angiotensin aldosterone. Sodium retained whilst potassium and hydrogen leaves.
What hormone controls excretion of sodium?
Atrial natriuretic hormone.
What enzyme does medicine for high blood pressure inhibit?
Angiotensin converting enzyme.
What is potassium regulated by?
Aldosterone.
What condition does hypo secretion of ADH cause?
Diabetes insipidus.
What does hyper secretion of ADH cause?
Water retention.
What is hyperplasia?
Increase in the number of cells.
What is hypertrophy?
Increase in cell size.
What hormones influence growth?
Thyroid.
The growth hormone.
Sex hormone.
What is different about the effects of the thyroid hormone in children and adults?
Irreversible effects in children.
Reversible in adults.
Name accessory hormones for growth.
Insulin, parathyroid/vitamin D and cortisol.
Name the functions of the thyroid hormone.
Protein synthesis in foetus/infants brain.
Development of neurons.
The effects of the thyroid hormone are..?
Indirect
The effects of the growth hormone are..?
Indirect
What increases the effects of the growth hormone? What does this do?
IGF-1.
Allows cartilage proliferation in long bones until the epiphyseal plate closes.
Name the types of dwarfism.
What causes each?
Hypothyroid: Lack of thyroid hormone.
Hypopituitary: Lack of growth hormone.
What is the sex hormone mediated by?
The growth hormone and IGF-1
What hormone, in excess, is detrimental to growth and increases in stress?
Cortisol.
What does an excess of the growth hormone in childhood cause?
Gigantism.
What does an excess of the growth hormone in adults cause? Why is this?
Acromegaly: Growth in extremities i.e. Hands, feet and jaw increase in bulk.
Due to longitudinal growth in adults not possible.
What is achondroplasia?
Reduction in cartilage cell growth.
