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69 Cards in this Set

  • Front
  • Back
Define how an endocrine cell differs from an exocrine cell
- Endocrine cells secrete their hormones directly into blood.
- Endocrine cells are richly associated with a network of capillaries.
What is a negative feedback system?
A negative feedback system is one in which disturbance to the set point elicits a system response that acts to counteract the direction of
the change. So, for example, a central heating system will cut off if the temperature on the thermostat is exceeded, thus reducing the temperature.
What is a positive feedback system?
A positive feedback (cascade) system is one in which distrubance to the set point elicits a system response that acts to enhance the direction of the change. Positive feedback mechainisms usually control episodic events i.e. those not needing continous adjustments. Oxytocin release is stimulated by pressure on the cervix, and causes vigorous contraction of the uterus. Oxytocin release ceases at birth.
Give an example of how a negative feedback system controls homeostasis.
-
How are hormones classified according to their solubility?
Hormones are either hydrophilic (water soluble) or hydrophobic (lipid soluble). Solubility affects the hormones ability to pass across the lipid cell membrane, and determines the hormone's method of action.
What are the general mechanisms of hormone action?
Hormones either
(a) ACT DIRECTLY - pass through the lipid bilayer of the cell membrane and bind with the cell DNA directly - influencing gene expression, or
(b) ACT VIA SECOND MESSENGER - can't pass across the cell membrane and instead bind to a receptor on the cell surface, which triggers a second messenger molecule to influence RNA within the cell cytoplasm.
What is the "thyroid axis"?
The thyroid axis is made up of the hypothalamus, pituitary and thyroid. The hypothalamus releases thyroid releasing hormone TRH which causes the pituitary to secrete thyroid stimulating hormone TSH, which in turn stimulates the thyroid to secrete thyroxine and triiodothyronine.
Is the thyroid axis a negative or positive feedback system?
The thyroid axis is a negative feedback system.
Draw a diagram of the thyroid axis.
(draw diagram)
What are the clinical signs of hyperthyroidism?
Overactive thyroid results in:
1) high BMR and weight loss
2) anxiety and restlessness
3) diarrhoea
State the clinical signs of hypothyroidism.
Underactive thyroid causes:
1) slowed BMR, weight gain
2) slowed mental process, lethargy
3) constipation
State the two classes of hormones based on their molecular composition.
Hormones may be either:
a) lipid-based
b) peptide-based
Name the three factors on which target cell activation by the hormone-receptor interaction is contingent.
The extent of target cell activation depends on:
1) blood hormone levels
2) the number of receptors for the hormone on/in target cells
3) the affinity between hormone and receptor.
Explain "up-regulation".
Up-regulation is where target cells form more receptors in response to higher levels of the specific hormones to which they respond.
What is "down-regulation"?
Down-regulation is caused by prolonged exposure to high hormone levels, and involves desensitisation/loss of receptors and reduced response to hormonal stimulation.
State the components of a feedback system.
All feedback systems have 5 common components:
1) stimulus
2) receptor organ/tissue
3) integration centre
4) effector organ/tissue
5) response
Define "hormone"
A hormone is a chemical messanger which is transported via the blood and acts on a specific target organ/tissue.
Name the hormones and target tissue of the thyroid gland
Thyroid gland secretes thyroxine and triiodothyronine. They act on almost every cell in the body. Thyroid hormone stimulates enzymes concerned with glucose oxidation.
Name the hormones and target tissue of the Anterior Pituitary.
The Anterior pituitary is also known as the adenohyophysis, secretes:
FSH (target=ovaries
TSH (target=thyroid)
Prolactin (mammary glands)
LH (target=Ovaries/testes)
Adrenocorticotrophic hormone
Growth hormone (targets=all cells)
What hormones originate in the posterior pituitary?
Oxytocin and ADH are released by the neurohypophysis (posterior pituitary gland) by exocytosis.
What does Growth Hormone do?
Growth hormone stimulates protein synthesis and growth and division of body cells.
What do the thyroid hormones do?
Thyroid hormones thyroxine and triiodothyronine
1) increase BMR
2) regulate metabolism of carbs, fats & proteins
What hormones does the thyroid secrete?
The thyroid secretes three hormones:
1) thyroxine
2) triiodothyronine
3) calcitonin
What is the action of calcitonin?
Calcitonin is secreted by the thyroid gland and acts on the skeleton. It is bone-sparing, i.e. it stops calcium resorption from bones and stimulates its uptake by the bone matrix.
What are the effects of excessive thyroid hormone secretion?
Symptoms of hyperthyroidism include:
1) Increased BMR
2) Weight loss despite good appetite
3) Tachycardia
4) Anxiety & physical restlessness

"speeded up"...can't W.A.I.T.
What are the signs/symptoms of hyposecretion of thyroid hormones?
Too little thyroid hormones cause:
1) low BMR
2) bradychardia
3) mental slowness, depression
4) weight gain or anorexia

"slowed down"
Name the main endocrine hormone of the hypothalamus.
The main endocrine hormone of the hypothalamus is Thyroid Releasing Hormone.
What is a "tropic" hormone?
A Tropic hormone is a hormone which regulates the function of another endocrine organ.
What does calcitonin do?
Oxytocin is bone sparing. It is involved in regulation of blood calcium levels and inhibits resorption of bone calcium and encourages calcium uptake into bone matrix.
What is the action of oxytocin?
Oxytocin is released from the posterior pituitary by exocytosis and stimulates vigorous contractions of the uterus during labour.
In which endocrine organ is oxytocin synthesized?
Oxytocin is synthesized in the hypothalamus and transported to the posterior pituitary by axonal transport via the infundibulum.
What is the action of ADH?
Anti Diuretic Hormone (ADH)stimulates the kidney tubules to reabsorb more water from the forming urine and return it to the bloodstream. The effect of ADH is to reduce urine volume and increase blood volume.
What is an "antidiuretic"?
An antidiuretic agent is a chemical substance that inhibits or prevents diuresis i.e. urine formation.
What is the action of growth hormone?
Growth hormone is an anabolic hormone that acts stimulates somatic growth, primarily of bone and muscle.
What endocrine gland secretes growth hormone?
Growth hormone is secreted by the anterior pituitary gland, i.e. the adenohypophysis.
What disorder would result from deficit and excess of growth hormone?
Deficit of growth hormone in children causes pituitary dwarfism.
Excess GH in adults causes acromegaly, excess GH in children causes gigantism.
What does Luteinising Hormone do?
Luteinising hormone stimulates the testes to produce testosterone, and the ovaries to produce oestrogen and progesterone.
What does Follicle Stimulating Hormone do?
FSH stimulates sperm production (testes) and ovarian follicle maturation (ovaries).
What does Adrenocorticotrophic Hormone do?
-
Tropic hormones...do what?
Tropic hormones regulate the hormonal functioning of other endocrine glands.
True or false?
All anterior pituitary hormones affect their target cells via second-messenger systems.
True - all adenohypophysis hormones use second messenger systems to affect target cells.
Lactation is stimulated by which hormone?
Prolactin, secreted from the anterior pituitary, stimulates lactation.
Which endocrine gland also has exocrine function?
The pancreas has both endocrine and exocrine cells. Its exocrine function is secreting pancreatic juice which contains digestive enzymes.
Name four main ways in which chronic hyperglycemia can cause secondary damage to the body.
Chronic hyperglycemia can cause:
1) kidney damage (nephropathy)
2) eye damage (retinopathy)
3) neuropathy
4) angiopathy (accelerating cardiovascular disease)
How does Thyroid Stimulating Hormone get from the Hypothalamus to the anterior pituitary ?
TSH is transported to the anterior pituitary via Portal Veins between the primary plexus and the secondary plexus of the adenohypophysis.
How do pituitary hormones exit the pituitary lobes?
Pituitary hormones exit both lobes via the Anterior and Posterior Hypophyseal Veins.
Name one major difference between the tissue of the anterior and posterior pituitary lobes.
Anterior lobe is glandular tissue, posterior lobe is neural tissue.
What stimulus triggers the release of ADH and Oxytocin by the posterior pituitary?
Release of ADH and Oxytocin is triggered by nerve impulses from the Hypothalamus.
What is the main function of the Hypothalamus?
The Hypothalamus is the main link between the endocrine and nervous systems.
What structural feature of endocrine glands facilitates their function?
Endocrine glands consist of secretory cells surrounded by a rich network of blood capillaries. This facilitates direct hormone into the bloodstream.
Explain the action of hydrophilic hormones.
1) Hydrophilic hormones cannot cross the cell membrane, so must employ second messenger systems.
2) Insulin molecule bonds to receptor cell in membrane
3) This interaction acts like a switch to activate glycogen synthase enzyme causing changes within the cell
Explain, using an example, how lipid-soluble hormones act on their target cells.
1) Lipid soluble hormones are hydrophobic and can cross the lipid cell membrane.
2) Once in cell, testosterone binds with its receptor, forming a complex.
3) the hormone-receptor complex enters the nucleus and directly influences gene expression (by binding with chromatin sites and activating mRNA transcription)
Where are the adrenal glands located?
The adrenal glands are located atop the kidneys.
Compare and contrast hydrophilic/hydrophobic hormones.
Hydrophobic hormones:
- act more slowly
- effects are irreversible
- can cross cell membrane
- modulate gene expression

Hydrophilic hormones:
- act rapidly
- effects are reversible
- need second messenger system
- activate enzymes that stimulate changes within cell
Name some LIPID hormones
Lipid hormones include:
- Testosterone
- Thyroid hormones
Name the three main ways in which hormone secretion is controlled.
Hormone secretion is controlled by:
1) Chemical changes in blood
2) Other hormones
3) Signals from the nervous system
What is "up-regulation" and "down regulation"?
Up-regulation = excess of hormone leads to decrease in number and sensitivity of target cell receptors. There is a decrease in response to the hormone by the body.
Up-regulation - deficient ofthe hormone leads to increase in number and sensitivity of target receptors. The body'responsiveness to the hormone increases.
What factors influence how sensitive a particular cell is to a hormone?
Cell sensitivity to a particular hormone depends on:
- other hormones in the bloodstream
- number of hormone receptors in/on cell
- how concentrated the hormone is in the blood at the time
What podiatric complications are common with hyperthyroidism?
Podiatric sequelae of hyperthyroidism include:
1) Hyperhydrosis
2) Tarsal Tunnel syndrome
What problems of the feet are often caused by hypothyroidism?
Hypothyroidism can cause the following foot problems:
1) Anhydrosis
2) Thick Skin
What are the adrenal hormones?
The adrenal gland secretes:
1) mineralocorticoids - which regulate electrolyte balance and help maintain blood pressure
2) glucocorticoids - concerned with metabolism and stress response
3) gonadocorticoids -
What is the main consequence of endocrine malfunction of the mineralocorticoids?
Mineralocorticoids (aldosterone) encourage reuptake of sodium from the forming urine in kidney tubules.
Excess sodium retention can cause high blood pressure and oedema.
Lack leads to Addison's disease (low sodium & glucose, severe dehydration, hypotension)
What happens if there is over- or under- secretion of the gonadocorticoids?
Gonadocorticoids:
1) undersecretion = female virilisation
2) oversecretion = not known
What are the main effects of lack/excess glucocorticoids?
Lack of glucocorticoids leads to Addison's disease (low sodium, low glucose, severe dehydration & hypotension)
Excess cortisol is anti-inflammatory and anti-immune.
Name a glucocorticoid hormone.
Cortisol is a glucocorticoid, synthesized by the adrenal glands.
Name a mineralocorticoid hormone.
Aldosterone is a mineralocorticoid, produced bythe adrenal glands.
Name a gonadocorticoid hormone.
Testosterone is a gonadocorticoid hormone, produced in the adrenal glands (and also mainly in the testes).
Which two hormones together control blood calcium levels?
Calcitonin (from thyroid) decreases blood calcium levels, whilst Parathormone increases blood calcium levels.
What would be the effect of chronic parathormone deficiency?
Parathormone increases blood calcium level by stimulating reabsorption of calcium from bone.
Hypercalcemia = extreme bone wasting
Hypocalcemia = tetany and respiratory paralysis