Endocrine and excretory system

Question 1

What is the structure and function of the hypothalamus?

Answer 1

Located under the thalamus in the brain.

> Tells the glands what to do based on the information it gets from the senses and other nerve functions.

Question 2

What is the structure and function of the pineal gland?

Answer 2

Located on the roof of the diencephalon of the brain.

> Produces and secretes the hormone melatonin which helps to regulate the sleep-wake cycle. Light inhibits it and darkness triggers it.

Question 3

What is the structure and function of the pituitary gland?

Answer 3

Connected to the hypothalamus. has 2 lobes which are actually 2 glands fused together.

> Makes hormones that instruct other glands to. make hormones that actually do the work.

Anterior pituitary:
>Manufactures and secretes a whole range of hormones.

Posterior pituitary:
>Secretes hormones made by the hypothalamus.
eg. Oxytocin - stimulates contraction of the uterus during childbirth and helps with breastfeeding.
eg. Antidiuretic hormone - tells the kidneys to retain water.

Question 4

What is the structure and function of the thyroid gland?

Answer 4

Located at the front of the neck below the Pharynx. Has 2 lobes, one on each side of the trachea.

> Regulates BP, HR, metabolism, appetite, muscle function

> Interacts with the pituitary via negative feedback loop
ie. the the pituitary is like a thermostat for the thyroid. it measures how much thyroid hormone is in the blood and if levels are low, it sends out thyroid stimulating hormone which travels to the thyroid which then secretes more thyroid hormone which boosts metabolism. This increase in metabolism is detected by the pituitary which stops secreting thyroid stimulating hormone.

Question 5

What is the structure and function of the thymus?

Answer 5

The thymus lies under the breastbone.

> Secretes thymosin, a hormone necessary for T cell (a lymphocyte) development and production.

Question 6

What is the structure and function of the pancreas?

Answer 6

Located behind the stomach.

> When BSL concentration rises, the pancreas secretes insulin which travels around the body and stimulates cells to absrob glucose. Liver and muscles convert it to glycogen for storage and adipose cells in the connective tissues convert it to fat.

> When BSL are low, the pancreas releases glucagon which stimulates liver and muscle cells ti start the process of breaking down glycogen and fat to make glucose.

Question 7

What is the structure and function of the adrenal glands?

Answer 7

Located right on the of the kidneys.

> Make hormones that help the kidneys maintain the level of salt and water in the body.

> They respond to stress. When the sympathetic NS sends the signal that a potential threat is near, the hypothalamus tells the pituitary to secrete adrenocorticotripic hormone. This stimulates the adrenal glands to make epinephrine and release it into the bloodstream which tells the organs to begin sympathetic response.

Question 8

What is the structure and function of the ovary?

Answer 8

Located in the lower abdomen.

> Make estrogen and progestin which stimulate the growth of the uterine lining among other things.

> during puberty, estrogens and progestins start menstruation and breast growth in preparation to help the female start to grown and nurse a baby.

> Estrogen is required for the manufacture of serotonin, a neurotransmitter that gives us a sense of calm and wellbeing.

Question 9

What is the structure and function of the testes?

Answer 9

Located inside the scrotum.

> Make androgens like testosterone which helps with sperm making.

> During puberty, the testes make even more androgens which lower the voice, make hair grow and increase muscle and bone mass.

Question 10

What are the principal differences between the endocrine and the nervous system?

Answer 10

Endocrine:
>Response is slower and more prolonged
>Uses chemical messengers/hormones
>Affects most body cells

Nervous:
>Rapid response
>Uses electrochemical impulses and neurotransmitters
>Mainly affects muscles fibres, smooth muscle and glands.

Question 11

Where are hormones produced?

Answer 11

Hormones are produced by endocrine glands specific to the hormone produced.
eg. Insulin is produced by the pancreas and released directly into the bloodstream.

Question 12

What factors influence the way a target cell responds to a hormone?

Answer 12

> The hormone’s concentration in the blood.

> The number of hormone receptors on the target cell.

> Influences exerted by other hormones.

> Some hormones work more effectively when a second hormone is present to assist them (synergistic effect).

> Some hormone oppose the action of others (antagonistic effect).

Question 13

Describe how protein based hormones exert their affect on target cells

Answer 13

Protein hormones are water soluble and therefore cannot pass directly through the plasma membrane of the target cell. They need to bind to receptors on the plasma membrane. This causes a structural change in the cell membrane, and the activation of intracellular second messengers which exert changes.

Question 14

Why is insulin not given orally?

Answer 14

Insulin is a small peptide hormone which would be broken down in the stomach.

Question 15

Which organs synthesise and release steroid hormones?

Answer 15

> The adrenal cortex (adrenal glands)
eg. Glucocorticoids (cortisol), mineral corticoids (aldosterone) and gonadocorticoids (androgens).

> The gonads (ovaries and testes)
eg. Testosterone, estrogen and progesterone.

Question 16

What are steroid hormones?

Answer 16

Steroid hormones are those made of cholesterol.

Question 17

How do steroid hormones that are lipid soluble exert their effect on target cells?

Answer 17

Lipid soluble steroid hormones diffuse across both the nell and nuclear membranes and exert their effects directly on the nucleus.

Question 18

Explain the term “tropic hormone”

Answer 18

A hormone that is produced by one endocrine gland and regulated the secretion of a hormone in another endocrine gland.

Question 19

List the four tropic hormones produced by the anterior pituitary

Answer 19

1. Thyroid stimulating hormone (TSH) - stimulates the thyroid gland to product thyroid hormone.
2. Adrenocorticotropic hormone (ACTH) - stimulates the adrenal cortex to produce cortisol.

3&4. Follicle stimulating hormone (FSH) and leuteinising hormone (LH) - stimulate the gonads to produce gametes as well estrogen and progesterone and testosterone.

Question 20

Name the non-tropic hormones produced by the anterior pituitary.

Answer 20

1. Growth hormone (GH) - stimulates growth, promotes protein synthesis and fat metabolism and increases BGLs.
2. Prolactin (PRL) - stimulates milk production.
3. Melanocyte stimulating hormone (MSH) - stimulates pigmentation and plays a role in appetite control in the CNS.

Question 21

Explain how regulating hormones secreted from the hypothalamus exert their effects on the anterior pituitary

Answer 21

The hypothalamus and the pituitary gland work together to control other endocrine glands.

> Releasing and inhibiting hormones secreted by neurones in the hypothalamus travel via the blood (the hypophyseal portal system) to the anterior pituitary to stimulate or inhibit release of the appropriate anterior pituitary hormones.

Question 22

Explain the function of the posterior pituitary

Answer 22

Connected to the hypothalamus via a nerve bundle.

> Does not make any hormones
Stores and releases 2 hormones produced by the hypothalamus.
1. Oxytocin - responsible for uterine contractions during birth and for milk ejection during suckling.
2. Vasopressin/ antidiuretic hormone - causes water reabsorption from the renal tubules into the bloodstream therefore reducing urine volume.

Question 23

What hormones are produced by the thyroid gland? What do they do?

Answer 23

> T3 (tri-iodo-thyronine) - a very potent hormone which increases BMR and stimulates cells to increases glucose utilisation.

> T4 (tetra-iodo-thyronine) - less potent - is converted into T3 and regulates growth and development especially in the nervous tissue and the reproductive system.

> Calcitonin - decreases blood calcium by increasing bone absorption of calcium which is important for bone growth.

Question 24

What mineral is essential for synthesis of the thyroid hormone?

Answer 24

Iodine!

Thyroid cells are the only cells in the body that absorb iodine.

Question 25

What endocrine disorder may result in areas where there is little iodine in the diet?

Answer 25

Iodine deficiency.

This can result in developmental delays and mental retardation.

Question 26

Name 2 major hormones that are produced by the pancreas and describe the function of these hormones

Answer 26

1. Insulin - lowers BGLs
   >It is essential for w=entry of glucose into most body cells.
   >Inhibits the breakdown of glycogen into glucose
   >Inhibits the conversion of amino acids or fats into glucose.
2. Glucagon - increases BGLs
   >Promotes breakdown of glycogen into glucose.
   >Promotes the synthesis of glucose from lactic acid and non-carbohydrate molecules.
   >Promotes the release of glucose from the liver.

Question 27

Name the 3 stress hormones.

Answer 27

1. Adrenaline
2. Noradrenaline
3. Cortisol

Question 28

Where are adrenaline and noradrenaline produced and what effect does it have?

Answer 28

Produced in the adrenal medulla.

Noradrenaline is secreted by the post-ganglionic, sympathetic nerve terminal and the adrenal medulla.

> Triggers fight or flight response (except sweating).
ie. Increased HR, BP, papillary dilation and brochodilation.

Question 29

Where is cortisol manufactured and what effect does it have?

Answer 29

Produced in the adrenal cortex.

> helps control blood sugar levels, regulate metabolism, help reduce inflammation.
It has a controlling effect on salt and water balance and helps control blood pressure.

Question 30

Explain why adrenaline/epinephrine is sometimes considered a neuroransmitter but is also considered a hormone

Answer 30

Adrenaline is a neurotransmitter in the sense that, within the brain it helps neurones to communicate with one another.

However, because adrenaline is mainly produced by the adrenal glands and has functions peripherally (i.e., outside the brain), it can also be considered a hormone.

Question 31

Describe the structure of the kidney

Answer 31

> The renal cortex contains millions of blood filters called nephrons.

> The renal medulla is divided into renal pyramids with renal columns made of cortical tissues between them.

> The renal medulla is hypertonic to filtrate in the nephron and hence aids in the reabsorption of water.

Question 32

Outline the functions of the kidneys

Answer 32

> Removes wastes (urea and creatinine)

> Regulates BP

> Regulates water, pH and electrolytes

> Erythropoiesis

> Vitamin D activity

Question 33

Outline the structure and function of the renal corpuscle.

Answer 33

The renal corpuscle is where blood is delivered to the nephron. It consists of:

1. The glomerulus - a tangle of capillaries that allows materials to move out of it.
2. The glomerular/bowman’s capsule - surrounds the glomerulus. Absorbs the filtrate leaving the glomerulus. The capsule has a visceral layer (on the inside) and a parietal layer (on the outside), between these layers is where primary urine is produceed.

Question 34

Outline the structure and function of a nephron.

Answer 34

Each nephron includes a glomerulus and a tubule.

The nephron is the functional unit of the kidneys where it:
>Removes wastes 
>Regulates BP
>Regulates water, pH and electrolytes
>Erythropoiesis
>Vitamin D activity

Question 35

Briefly outline what drives filtration in the glomeruli and their permeability.

Answer 35

Glomeruli are permeable to water and solutes (molecules smaller than 3mm pass through the filtration membrane).

They are impermeable to large molecules like proteins and blood cells.

Hydrostatic pressure drives the glomerular filtration rate.

Question 36

Define glomerular filtration rate

Answer 36

The glomerular filtration rate describes the flow rate of filtered fluid through the kidney.

Creatinine clearance rate is a useful measure for approximating glomerular filtration rate.

Glomerular filtration is tightly regulated at about 125mL/min = 180L/day.

Over 99% of filtrate is reabsorbed and around 2L of urine is produced.

Question 37

What would lead to decreased glomerular filtration rate?

Answer 37

>Dehydration
>Fluid loss
>Long term damage from diabetes
>Hypertension
>Kidney injury
>Drugs

Question 38

What is the relationship between systemic blood pressure and urine output?

Answer 38

An increase in systemic BP would cause an increase in renal blood flow and a corresponding increase in glomerular filtration rate and thus, urine output.

Question 39

Explain how the kidneys maintain a relatively constant glomerular filtration rate during normal daily activities

Answer 39

Renal auto-regulation maintains a relatively constant glomerular filtration rate by altering the diameter of afferent (to the CNS) arterioles.

If BP increases, the arteriole would constrict in order to protect the glomerular capillaries from increased pressure.

If BP decreases, the arteriole would dilate in order to maintain glomerular filtration rate.

If the arteriole maintain normal diameter all the time, there would be an increase in glomerular filtration rate resulting in severe water loss and dehydration.

Question 40

What happens to the glomerular filtration rate when there is a large drop in BP?

Answer 40

> auto-regulation stops and extrinsic regulation is activated.

> Glomerular filtration rate drop sin order to maintain BP.

> The sympathetic nervous system causes strong constriction of the arterioles, inhibiting glomerular filtration rate.

> The renin-angiotension mechanism stimulates renin to be released from the kidneys. Renin acts on angiotensin, turning it into angiotensin 1 and then angiotensin 2. Angiotensin 2 is a strong vasoconstrictor that also stimulates the release of aldosterone from the adrenal cortex. Aldosterone increases Na+ and water reabsorption from the distal convoluted tubule and collecting ducts.

> Plasma volume increases, BP increases and urine production decreases.

Question 41

How do they kidneys help to maintain fluid balance? What are the hormones involved?

Answer 41

The hormones involved are antidiuretic hormone and aldosterone.

Antidiuretic hormone:
>Controls water reabsorption from urine filtrate.
>Inhibits diuresis (production of urine)
>Makes collecting ducts permeable to water.

Aldosterone:
>Conservation of Na+ and the secretion of K+ which leads to increased water retention and increased BP.

Question 42

How do the kidneys respond to exercise?

Answer 42

Exercise promotes sweating, waster is lost and osmolarity is increased.

Osmoreceptors are stimulated and antidiuretic hormone is released.

If BP increases significantly, afferent arterioles will constrict.

Question 43

How does the kidney regulate electrolyte concentrations?

Answer 43

By reabsorption from renal tubules and then secretion of unwanted electrolytes.

> When pH falls, so does K+ secretion.
When Na+ is retained, K+ is secreted.

Question 44

How do kidneys respond to excess salt intake?

Answer 44

High Na+ will cause an increase in plasma osmolarity which is detected by osmoreceptors.

Antidiuretic hormone is released, causing an increase in water reabsorption from the collecting ducts. This will result in more concentrated urine. The increased osmolarity will also trigger the thirst mechanism.

Question 45

What does urine consist of?

Answer 45

> 95% water and 5% solutes

> Solutes include nitrogenous wastes - urea, uric acid and creatinine as well as Na+, K+, phosphate, sulfate, Ca+, Magnesium and bicarbonate ions.