Physiology and Anatomy - Endocrine System

What are 5 diseases caused by the disruption of the endocrine system?

Gigantism

Hypothyroidism

Grave's disease

Cushing's disease

Addison's disease

What is the coordinating system?

The combination of nervous sytem and the endocrine system

Example of a non-endocrine organ which secretes hormone?

Heart secretes ANP which is a vasostimulant

What is the definition of an hormone?

Hormones are blood-borne chemical messengers

What are the 3 different categories of hormones?

Steroids, peptides and amines

What are two properites of steroid hormones?

They are derivatives of cholesterol

They are typically hydrophobic

What is the precursor of oestrogen?

Estradiol

What is an example of a peptide hormone?

Insulin

What are amine hormones derived from? And what is an example of one?

Derived from amino acids

Eg: thyroxine

How do smaller hormones bring about change?

Pass through cell membrane and directly affect transcriptional regulators. These are also diffusible

Eg: steroids

How do larger hormones bring about change?

Bind to receptors on the membrane to affect transcriptional regulators

Allows precise cell targeting

In a diagram, which pituitary is on the left and which is on the right?

Posterior is on the left (as if looking at patient) and anterior is on the right

What is responsible for signalling between the hypothalamus and the anterior pituitary?

Hypophyseal portal vessels

Hormones from hypothalamus travel in blood to the anterior pituitary

How does the hypothalamus communicate with the posterior pituitary?

Connected via neural network as posterior pituitary and hypothalamus develop from the same tissue

What 4 things is the thyroid controlled by?

Hypothalamus

Pituitary

Sympathetic nervous system

Parasympathetic nervous system

What two hormones does the thryroid secrete and what do these contain?

Triiodothyronine (T3) and thyroxine (T4)

Contain iodine

Which cells produce T3 and T4?

Follicle cells

What takes in iodine from the blood and where is it accumulated?

Thyroid globulins

Follicles filled with colloid

What cells produce calcitonin?

C cells or parafollicular cells

What type of hormone is calcitonin?

Peptide hormone

What are the effects of T3 and T4 and which is more active?

Increase the basal rate of oxygen consumption and heat production

Modifies the metabolism of carbohydrates and fats to provide substrate for oxidation (heat production)

Increases blood volume for increased cardiac activity

After birth, stimulates the ossification of bone

T3 is more active

What is hypothyroidism?

Insufficient supply of T3 and 4

Weight gain and feeling cold

Can be due to genetic factors

What is hyperthyroidism?

Aka grave's disease

Too much T3 and T4

Sweating, weight loss, anxiety and palpitation

What is the function of TSH and where is it released from?

Increases energy of follicular cells to stimulate production of T3 and T4

Stimulates the uptake of iodine from the blood

Released from the anterior pituitary

What are the parathyroid hormones (PTH) and where are they secreted from?

Peptide hormone secreted by chief cells in the parathyroid

What is the size of parathyroid gland tissue?

5mm

3 things calcium is important for?

Bones

Blood clotting

Muscle contraction

What is an important role of calcitonin and PTH?

Regulating plasma mineral levels, especially calcium

What should plasma levels be in an healthy individual?

2.3 - 2.4 mmol/L

Skeleton contains how much of body's calcium?

99%

What are osteoblasts?

Cells responsible for desposition(accretion) of bone

Builds bone

What are osteoclasts?

Cells responsible for resorption (eating) of bone

Calcium and phosphate are released into plasma

Dissolves bone

What does PTH do and when is it released?

PTH is released when the conc of calcium in the blood is too low

It binds to osteoblasts which indirectly stimulates osteoclasts and bone is resorbed, increasing concentration of calcium in the blood

Also causes the kidneys to reabsorb more calcium, increasing levels

What does calcitonin do and when is it released?

Calcitonin lowers blood calcium levels by inhibiting the activity of osteoclasts and it promotes the secretion of calcium by the kidneys

What can unregulated levels of calcium lead to?

Skeleton integrity issues

Where are the adrenal glands located?

Located on top of each kidney

What is the adrenal cortex derived from?

Future muscle tissue and hence relies on hormonal regulation

What is the adrenal medualla derived from?

Embryonic neural crest which will go onto form the spinal cord hence has direct connections with the nervous system

What are the sections of the adrenal gland from the cortex to the medulla?

Zona glomerulosa

Zona fasciculata

Zona reticulatris

Adrenal medulla

What hormones does the medulla?

Adrenaline and noradrenaline

Which cells release adrenaline and noradrenaline and what are they derived from?

Chromaffin cells

Derived from cholesterol

What hormone is released by the zona glomerulosa?

Aldosterone

What hormone is released by the zona fasciculata?

Cortisol

What hormone is released by the zona reticularis?

Androgens which are sex steroids

What is the combined name for adrenaline and noradrenaline?

Catecholamine

What trigers the release of adrenaline and noradrenaline?

Neurons from the spinal cord

What does aldosterone do?

Day-to-day blood pressure response

What does cortisol do?

Involved with responses to environmental cues such as circadian rhythms and stress responses

Also increases glucose production and storage and metabolic rate

Has immunosuppressive effefts in large doses and reduces inflammation

What is caused by an overproduction of cortisol?

Cushing's syndrome

What are 6 symptoms of Cushing's syndrome?

Red cheeks

Buffalo hump

Bruise easily

Abdominal stretch marks

Pendulous abdomen (fat cells)

Thin arms and legs (loss of amino acids)

What is aldosterone secretion controlled by?

Renin-angiotensin system (RAAS)

During RAAS, how is blood pressure increased?

Precursors from the liver stimulare the adrenal glands to release aldosterone

This causes the reabsorption of NaCl and H20 and the excretion of potassium, increasing the blood pressure

What is Conn's syndrome?

Overproduction of aldosterone which amplifies the effects and can arise due to adrenal tumour

What are the 4 symptoms of Conn's syndrome?

High blood pressure

Low blood potassium

Polyuria (needing to urinate frequently)

Fatigue

Which organ degrades glycogen to obtain more glucose?

Liver

What two organs is the pancreas in close proximity to?

Liver and stomach

Which section of the pancreas does hormone secretion?

Islets of Langerhans

What are the 3 cell types within the islets of Langerhans?

Alpha: glucagon

Beta: insulin

Delta: somatostatin

What kind of hormones are insulin and glucagon?

Peptide hormones which are antagonistic of each other

How does insulin work?

Stimulates glucose uptake by the liver and skeletal muscles

Inhibits the production of glucose by liver and fatty tissues

Inhibits gluconeogenesis and lipolysis (breaking down of white adipose tissue for glucose)

How does glucagon work?

Promotes glycogen and lipid degradation

Promotes gluco

What 4 locations is somatostatin produced in?

Delta cells (pancreas)

Hypothalamus

GI tract

Central nervous system

What does somatostatin do in the pancreas?

Inhibits the production of insulin and glucagon

Where are receptors for insulin located?

Liver and skeletal muscles

Once insulin binds, what is the main point of the signalling cascade?

The export of glucose transporters into the plasma membrane

What is it called when a substance increases blood glucose levels?

Hyperglycemic

What is it called when a substance decreases blood glucose levels?

Hypoglycemic

What is it called when pregnant people temporarily develop diabetes?

Gestational diabetes mellitus (GDM)

How long are embroys undifferentiated until?

Until 5-6 weeks of gestation

What are female ducts called?

Mullerian duct

What are male ducts called?

Wolffian duct

What gene is expressed at 6 weeks if the Y chromosome is present and what does this encode?

SRY gene which encodes the testes determining factor (transcriptional regulator protein triggering development of testes)

What 2 hormones are released by the testes once developed?

Anti-Mullerian hormone (AMH/MIS/MIH) and testosterone

What does AMH do?

Causes the Mullerian ducts to regress

What hormone is released by the prostate?

Testosterone

What 3 tissue types develop due to testosterone stimulating the Wolffian duct?

Seminal vesicles (produces semen)

Epididymis (Site of maturation of stem cells)

Vas deferens (carries sperm out of testes)

What 4 reproductive organs does the Mullerian duct grow into?

Fallopian tube (egg travels from ovary to uterus)

Uterus (aka womb, site of foetal development)

Cervix (connection between vagina and uterus which contracts and expands during birth)

Upper vagina (part of birth canal)

What are the testes divided into

What do these contain

What do these merge into

Lobules

Seminiferous tubules

Epididymis

What are leydig cells?

Cells in the spaces between the tubules

What are sertoli cells?

Cells that surround immature sperm cells and nourish them

What reproductive hormones are released by the hypothalamus?

Gonadotrophin-releasing hormone (GnRH) and Luteinising hormone-releaseaing hormone (LHRH)

What reproductive hormones are released by the anterioir pituitary?

Follicle stimulating hormone (FSH)

Luteinising hormone (LH)

In the male reproductive system, what does LH doe?

Triggers the Leydig cells to release testosterone which combines with FSH to trigger the Sertoli cells to stimulate the development of sperm cells

Which layer of the seminiferous tublue stores the spermatogonium?

Basal layer

What does testosterone inhibit, forming a negative feedback loop?

GnRH and LH

What is inhibin?

Peptide hormone produced by the sertoli cells in response to production of testosterone from the Leyding cells

It travels to the anterior pituitary and inhibits FSH production

What kind of hormones are FSH and LH?

Glycoproteins

What kind of hormone is GnRH?

Peptide hormone

What kind of hormone is testosterone?

Steroid hormone

What is the site of oogenesis and what is oogenesis?

Follicles

Development of ovules

What do the non-dominant follicles grow into?

Corpus luteum

What are the layers of the follicles from the inside out?

Oocyte

Zona pellucida

Granulosa cells

Are theca cells part of the follicle or ovary?

Ovary

What 3 hormones control follicle development?

FSH, LH and oestrogen

What does the spike in LH trigger?

Ovulation

What happens during the luteal phase?

FSH and LH stimulate the progesterone production by the corpus luteum

What do androgens from theca cells do?

They are converted to oestrogen by granulosa cells, promoting follicle growth

What are the precursors to oestrogen and progesterone?

Androgens

What triggers ovule expulsion?

Large amount of LH

How is there a positive feedback look in the female reproductive system?

LH stimulates theca cells to produce androgens

FSH stimulates granulosa cells to convert androgen to oestrogen

This stimulates further LH and FSH production