Endocrinology

Question 1

What are the functions of the endocrine system?

Answer 1

Make hormones and control their release
Maintain internal homeostasis
Regulates growth, development, metabolism, energy balance

Question 2

What are the differences of hormone communication and neuron communication?

Answer 2

Hormone is long-term and slow chemical signals which are slower to respond
Neuron is short-term and fast chemical and electrical signal which are faster to respond

Question 3

What are hormones?

Answer 3

Chemical messengers, release in the blood stream, that act through receptors to cause a change in target cell.
Secreted by endocrine system into the ECF

Question 4

What are the hormone funcions?

Answer 4

Circulate through blood
Only affect target cell/tissue/organ
Can change:
- plasma membrane permeability
- opening or closing ion channels
- activate or inactive enzyme

Question 5

How do target cell respond to hormone?

Answer 5

Respond with hormone specific protein

Question 6

Explain the direct gene activation

Answer 6

Only steroid and thyroid hormones use this mechanism
1. Hormone enters the nucleus
2. Binds to specific hormone receptor
3. Hormone receptor complex, then binds to specific sites on cell DNA
4. Activates certain gene to transcribe messenger RNA (mRNA)
5. mRNA is translated in cytoplasm
6. Resulting in synthesis of new protein

Question 7

Explain the second messenger system

Answer 7

Not all steroid hormone, protein and peptide hormones use this mechanism
1. Hormone binds to receptor protein on membrane
2. Activated receptors set off series of reaction that activates an enzyme
3. Enzyme catalyzes reactions that produce second messenger
4. Cyclic adenosine monophosphate (cAMP) oversee intracellular changes that promote the typical response of target cell to hormone

Question 8

What are the three hormone classifications?

Answer 8

Amino acid derived hormone
Peptide hormone
Lipid derived hormone

Question 9

Explain amino acid derived hormone

Answer 9

• Small water-soluble hormones that can cross the cell membranes
• Structurally related to amino acids (tyosine and trypotophan)
  Examples: thyroid hormones, catecholamines, serotonin and melatonin
• Water soluble which means they bind to receptor on cell membrane (second messenger)

Question 10

Explain peptide hormone

Answer 10

• Chains of amino acids, glycoproteins, short polypeptide, and small proteins
• Cannot pass through cell membrane due to their size and water-soluble nature
• Must abundant type of hormone
  Examples: TSH, LH, FSH, Insulin
• Water soluble which means they bind to receptor on cell membrane (second messenger)

Question 11

Explain lipid derived hormone

Answer 11

• Short chain polypeptides
• Two types:
  . steroids: derived from cholesterol (androgens, estrogens, progesterone)
  . eicosanoids: arachidonic acid, phospholipids found in cell membrane
  (prostaglandins, clotting factors, leukotrienes)
• Lipid soluble which means pass through cell membrane (direct messenger)

Question 12

What is hormone transport and inactivation?

Answer 12

Hormones may circulate freely or travel bound to special carrier proteins
Free hormones remain functional for less than 1 hour

Question 13

When are free hormones inactivated?

Answer 13

1. Diffuse out of bloodstream and bind to receptors on target cells
2. Are absorbed and broken down by liver or kidneys
3. Broken down by enzymes in blood or interstitial fluids

Question 14

What are the five types of intracellular communication?

Answer 14

Direct communication
Autocrine communication
Paracrine communication
Endocrine communication
Synaptic communication

Question 15

Explain direct communication

Answer 15

Exchange of ions and molecules between adjacent cells across gap junctions
Occurs between two cells of same type
Highly specialised and relatively rare

Question 16

Explain autocrine communication

Answer 16

Hormones are produced by a cell and act locally on the same cell
Chemicals involved are autocrine
- prostaglandins secreted by smooth muscle cells cause same cells to contract

Question 17

Explain paracrine communication

Answer 17

Chemical signals transfer information from cell-to-cell within a single tissue

Question 18

Explain endocrine communication

Answer 18

Endocrine cells release hormones that are transported into bloodstream
Alters metabolic activities of many organs

Question 19

What is the negative feedback and positive feedback?

Answer 19

Negative feedback: inhibition of further secretion of hormone
Positive feedback: release of further secretion of hormone

Question 20

What is an example of feedback loops?

Answer 20

Hypothalamic-pituitary pathways - long loop negative feedback

Question 21

Explain hypothalamic-pituitary pathway?

Answer 21

Pituitary hormone feedback to decrease hormone secretion by hypothalamus
Hormones secreted to peripheral endocrine “feed back” to suppress secretion of anterior pituitary and hypothalamic hormones

Question 22

What are the major organs of the endocrine system?

Answer 22

Pituitary gland and hypothalamus
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary/Testes

Question 23

Explain the pituitary glands

Answer 23

Hangs from the hypothalamus
Anterior = adenohypophysis
Posterior = neurohypophysis
All tropic hormones (except for prolactin, growth hormone)

Question 24

What are the hormones released by the anterior pituitary?

Answer 24

Growth hormone: anabolic, protein-conserving, promotes body growth to skeletal muscle and bones
Prolactin: stimulates production of breast milk
Adrenocorticotropic hormone: stimulates adrenal cortex to release its hormone
Thyroid-stimulating hormone: stimulates thyroid gland to release thyroid hormones
Gonadotropic hormones: FSH and LH

Question 25

What the hormones released by posterior pituitary?

Answer 25

Oxytocin: stimulates powerful contractions for childbirth, milk ejection
Antidiuretic hormone: kidney tubule cells to reabsorb and retain body water, increase blood pressure by constricting blood vessel

Question 26

Explain the pineal gland

Answer 26

Releases melatonin which affect circadian rhythm
Targets hypothalamus

Question 27

Explain the thyroid gland

Answer 27

Thyroid hormone into two subtypes:
- thyroxine T4 (secreted by thyroid follicles) and triiodothyronine T3 (formed by target tissue)
Major metabolic hormone
Increase rate of cell oxidise glucose
Calcitonin: released by parafollicular cells surrounding thyroid follicles, response to high blood level of calcium ions, decreases blood calcium by depositing calcium into bones

Question 28

Explain parathyroid glands

Answer 28

Four tiny masses of glandular tissue
- Parathyroid hormone: response to low blood calcium drops below threshold, liberates calcium from bones, stimulated kidneys and intestine to absorb more Ca2+

Question 29

Explain the thymus

Answer 29

Located in upper thorax
Thymosin: promotes maturation of T cells

Question 30

Explain adrenal glands

Answer 30

Paired glands perched on the kidneys
Cortex hormones:
- mineralocorticoids (aldosterone): regulate sodium ions, reabsorption potassium ion, kidneys
- glucocorticoids: increase blood glucose level, depress inflammatory response
- sex hormones
Medulla hormones:
- catecholamines (epinephrine, norepinephrine): in response to sympathetic nervous system stimulation

Question 31

Explain pancreatic islets

Answer 31

Located in abdomen close to stomach.
Insulin (b-cells): blood level of glucose high, increase rate of glucose uptake
Glucagon (a-cells): blood level of glucose low, stimulates liver to release glucose to blood