What are the components of the endocrine system?
All cells, tissues, and organs that secrete hormones into the internal environment.
What is the difference between paracrine and autocrine secretions?
Paracrine secretions only affect neighboring cells, whereas autocrine secretions only affect the secreting cell itself.
What is the difference between endocrine and exocrine glands?
Endocrine glands secrete substances into the blood stream or interstitial fluid, whereas exocrine glands secrete their products onto an external surface through ducts.
What are the functions of endocrine glands and their hormones?
- Regulate chemical reactions
- Aid in the transport of substances across membranes
- Regulate water and electrolyte balance
- Play vital roles in reproduction, development and growth
What are the major endocrine glands?
Pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, pineal gland, reproductive glands, kidneys, and thymus.
What are the general types of hormones?
Steroids synthesised from cholesterol
Glycoproteins synthesised from amino acids
Outline the structure and properties of a steroid hormone
- Consist of complex rings of carbon, hydrogen and oxygen atoms
- Insoluble in water and soluble in lipids
- In the blood they are weakly bound to plasma proteins
- Can diffuse into cells easily
What are the events that occur when a steroid hormone molecule enters a target cell? 
- The steroid hormone diffuses through the cell membrane
- It binds to a specific receptor
- The hormone-receptor complex binds in the nucleus to specific DNA sequences, activating transcription in specific genes
- The mRNA molecules leave the nucleus and enters the cytoplasm
- The mRNA associates with ribosomes and synthesised specific proteins
How do nonsteroid hormones get inside their target cells?
They bind to receptors on the cell membrane
What are the two sites on a receptor molecule?
The binding site and activity site
What is the hormone that triggers the cascade after binding to a receptor is callled a what?
A first messenger
The biochemicals in the cell that induce changes in response to the hormone's binding are called what?
Outline the mechanism for how cAMP (cyclic adenosine monophosphate) is formed 
- A hormone binds to its receptor
- The hormone-receptor complex activates a G protein (a membrane protein)
- The G protein activates adenylate cyclase (an enzyme which is a membrane protein)
- In the cytoplasm, activated adenylate cyclase catalyses the formation of cAMP from ATP
- cAMP activates protein kinases. They phosphorylate their substrate molecules which activates them.
What are some of the changes that a second messenger can induce? 
- Altering membrane permeability
- Activating enzymes
- Promoting protein synthesis
- Stimulation/inhibition of metabolic pathways
- Moving the cell
- Initiating the secretion of hormones or other substances
What is the name of the enzyme that quickly inactivates cAMP?
Apart from cAMP, what are other second messengers?
DAG and IP3
What are prostaglandins and what are some of the cells that produce them?
They are a group of biochemicals synthesised from fatty acids that regulate cells.
They are produced in the cells of the liver, kidney, heart, lungs, thymus, pancreas, brain, and reproductive organs.
What are some examples of the functions of prostaglandins?
Prostaglandins produces diverse and even opposite effects.
- Relax smooth muscles in airways in the lungs and in blood vessels
- Contract smooth muscles in the uterus and intestines
- Stimulate hormone secretion from the adrenal cortex and inhibit the secretion of HCl from the stomach wall
- They influence the movement of sodium ions in the kidneys, help regulate bood pressure, and have powerful effects on male and female reproductive physiology
What are the three ways in which hormone secretion is controlled?
- The hypothalamus regulates the anterior pituitary gland's release of hormones that stimulate other endocrine glands to release hormones.
- The nervous system stimulates some glands directly
- Another group of glands responds directly to the changes in the composition of the internal environment.
The ________ _____ (hypophysis) is located at the base of the brain, where the _________ _____ (infundibulum) attaches it to the hypothalamus. The gland is about 1cm in diameter and consists of an ________ lobe, and a _________ lobe.
The pituitary gland (hypophysis) is located at the base of the brain, where the pituitary stalk (infundibulum) attaches it to the hypothalamus. The gland is about 1cm in diameter and consists of an anterior lobe, and a posterior lobe.
The brain controls most of the pituitary gland's activities. For example, the _________ pituitary releases hormones when _____ impulses from the hypothalamus signal the axon terminals of _____________ cells in the _________ pituitary. On the other hand, _________ hormones from the ___________ control secretion from the anterior pituitary.
The brain controls most of the pituitary gland's activities. For example, the posterior pituitary releases hormones when nerve impulses from the hypothalamus signal the axon terminals of neurosecretory cells in the posterior pituitary. On the other hand, releasing hormones from the hypothalamus control secretion from the anterior pituitary.
What veins give rise to the capillary network around the anterior pituitary?
Hypophyseal portal veins
What does growth hormone (GH) do?
It stimulates cells to increase in size and divide more frequently. It also enhances the movement of amino acids across cell membranes and speeds the rate at which cells utilise carbohydrates and fats.
What two hormones from the hypothalamus control GH secretion?
GH-releasing hormone (GHRH) and GH-release inhibiting hormone (GHIH)
What is the role of prolactin (PRL)?
It stimulates and sustains breast milk production following the birth of an infant. Abnormally elevated levels of PRL can disrupt sexual function.
What is the role of thyroid-stimulating hormone (TSH) and thyroid-releasing hormone (TRH)?
TSH controls thyroid gland secretions. TSH release is partially controlled by the hypothalamus which produces TRH.
What is the role of adrenocorticotropic hormone (ACTH) and corticotrophin-releasing hormone (CRH)?
ACTH controls the manufacture and secretion of certain hormones from the cortex of the adrenal gland.
CRH regulates ACTH secretion by being released by the hypothalamus in response to decreased concentrations of ACTH.
What is the role of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)?
They are gonadotrophins which act on the gonads: the ovaries and testes.
What does the posterior pituitary mainly comprise of?
Nerve fibers and neuroglia
Specialised neurons in the hypothalamus produce the two hormones associated with the posterior pituitary. What are these hormones?
Antidiuretic hormone (ADH) and oxytocin (OT)
Specialised neurons in the hypothalamus produce the two hormones associated with the posterior pituitary.
How are these transported and released?
They travel down axons through the pituitary stalk (infundibulum) to the posterior lobe, and are stored in veicles near the ends of the axons.
Nerve impulses from the hypothalamus release the hormones into the blood.
What's the difference between a diuretic and an antidiuretic?
A diuretic is a chemical that increases urine production, whereas an antidiuretic decreases urine formation.
How does the hypothalamus regulate ADH secretions?
Through osmoreceptors that sense a change in osmotic pressure.
What hormones are released from the anterior pituitary gland?
- Growth hormone (GH)
- Prolactin (PL)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
What hormones are released from the posterior pituitary gland?
- Antidiuretic hormone (ADH)
- Oxytocin (OT)
The follicular cells of the thyroid gland synthesize two hormones- _________, also known as T4 because it contains four atoms of iodine, and _______________, known as T3 because it includes three atoms of iodine.
The follicular cells of the thyroid gland synthesize two hormones- thyroxine, also known as T4 because it contains four atoms of iodine, and triiodothyronine, known as T3 because it includes three atoms of iodine.
Thyroxine and triiodothyronine have similar actions, although triiodothyronine is five times more potent. What are their actions?
These hormones help regulate the metabolism of carbohydrates, lipids, and proteins, They increase the rate at which cells release energy from carbohydrates, increase the rate of protein synthesis, and stimulate the breakdown and mobilisation of lipids.
Thyroid hormones are the major factors determining how many calories the body must consume at rest in order to maintain life, which is known as the _____ __________ _____ (___).
Thyroid hormones are the major factors determining how many calories the body must consume at rest in order to maintain life, which is known as the basal metabolic rate (BMR).
What is the role of calcitonin and parathyroid hormone (PTH)?
Together they regulate the concentrations of blood calcium and phosphate ions.
Give an example of a steroid hormone.
Give an example of an amine hormone.
Give an example of a peptide hormone.
- Antidiuretic hormone
- Thyrotropin-releasing hormone
Give an example of a protein hormone.
- Parathyroid hormone
- Growth hormone
Give an example of a glycoprotein hormone.
- Follicle-stimulating hormone
- Luteinizing hormone
- Thyroid-stimulating hormone
Why is calcitonin not referred to as a thyroid hormone?
It is not produced by the thyroid's extrafollicular cells.
Label the Thyroid:
Where are the parathyroid glands located?
On the posterior surface of the thyroid gland.
The parathyroid glands secrete ____________ _______ (___) which increases blood _______ concentration and decreases blood __________ ion concentration. ___ affects the bones, kidneys, and intestine.
The parathyroid glands secrete parathyroid hormone (PTH), which increases blood calcium concentration and decreases blood phosphate ion concentration. PTH affects the bones, kidneys, and intestine.
What does PTH inhibit and stimulate? What does this lead to?
PTH inhibits the activity of osteoblasts and stimulates osteoclasts to reabsorb bone and release calcium and phosphate ions into the blood.
At the same time, PTH causes the kidneys to conserve blood calcuim and to excrete more phosphate ions into the urine. It also stimulates calcuim absorption from food in the intestine, further increasing blood calcium concentration.
Negative feedback between the parathyroid glands and the blood ________ concentration regulates ___ secretion. As blood _______ concentration drops, more ___ is secreted; as blood _______ concentration rises, less ___ is released.
Negative feedback between the parathyroid glands and the blood calcium concentration regulates PTH secretion. As blood calcium concentration drops, more PTH is secreted; as blood calcium concentration rises, less PTH is released.
Label the adrenal gland:
The cells of the adrenal medulla secrete two closely related hormones, what are they and what are their functions?
Epinephrine and norepinephrine. They increase heart rate, the force of cardiac muscle contraction, breathing rate, and blood glucose level. They also elevate blood pressure and decrease digestive activity.
What stimulates the adrenal medulla to release its hormones?
Impulses from the sympathetic nervous system caused by the hypothalamus' response to stress.
What are the three most important adrenal cortical hormones?
Aldosterone, cortisol, and certain sex hormones.
- Where is it synthesised?
- What type of hormone is it?
- What does it do?
- It is synthesised in the outer zone of the adrenal cortex
- A steroid hormone which is a mineralocorticoid (regulates minerals and electrolytes)
- It causes the kidney to conserve Na+ ions and excrete K+ ions. This stimulates water retention indirectly by osmosis.
- Where is it produced?
- What type of hormone is it?
- What does it do?
- It is produced in the middle zone of the adrenal cortex
- It is a steroid hormone that is a glucocorticoid (affects glucose metabolism)
- Corticol has several functions:
Inhibition of protein synthesis in tissues → Increases blood concentration of amino acids
Promotes fatty acid release from adipose tissue → Utilises fatty acid use
Stimulation of liver cells to synthesise glucose from noncarbohydrates → Increases blood glucose concentration
- Inhibition of protein synthesis in tissues → Increases blood concentration of amino acids
- Promotes fatty acid release from adipose tissue → Utilises fatty acid use
- Stimulation of liver cells to synthesise glucose from noncarbohydrates → Increases blood glucose concentration