Lecture 5

Question 1

A hormone is

Answer 1

A chemical messenger secreted into the blood by specialized epithelial cells

Question 2

Properties of a hormone

Answer 2

1. Cell to cell communication: chemical signals, usually very low concentration are secreted by cells and transported by the blood to distant target tissues
2. Binding to target receptor initiates cellular response (response depends on receptor or signalling pathways of of the target cells)
3. Communication is eventually terminated (limiting secretion, inactivating hormone, terminating target cell activity)
4. Half-life: time for the hormone to reduce 1/2 in the blood

Question 3

Peptide hormone (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)

Answer 3

1. Made in advance and stored in secretory vesicles
2. Exocytosis
3. Dissolved in plasma
4. Short
5. Cell membrane
6. Altered activity of proteins

Example: insulin

Question 4

Steroid hormones (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)

Answer 4

1. Made from cholesterol and it’s synthesized on demand from lipophobic precursors
2. Simple diffusion
3. Bound to carrier proteins
4. Long
5. In cytoplasm or nucleus and some can be found in cell membrane
6. Induction of new protein synthesis

Example : Testosterone

Question 5

_____________ is the parent amino acid for ___________ and _____________

Answer 5

1. Tyrosine
2. Catecholamines (neurohormone)
3. Thyroid hormone

Question 6

Catecholamines (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)

Answer 6

1. Made in advance and stored in secretory vesicles
2. Exocytosis
3. Dissolved in plasma
4. Short
5. Cell membrane
6. Modification of existing proteins

Example: epinephrine

Question 7

Thyroid hormones (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)

Answer 7

1. Synthesized on demand from stored lipophobic precursors
2. Transport protein
3. Bound to carrier proteins
4. Long
5. Nucleus
6. Induction of new protein synthesis

Example: thyroxine

Question 8

Endocrine vs. Exocrine secretions

Answer 8

Endocrine glands: secretes it’s products for example hormones directly into the blood
Exocrine glands: secretes it’s products for example enzymes, into ducts that lead them to target tissues

Question 9

Alpha cells secrete….
Beta cells secrete….

Answer 9

Glucagon
Insulin

Question 10

Hormone actions are diverse: hormones may regulate cellular processes

Answer 10

1. Rates of enzymatic reactions
2. Transport of ions or molecules across the cell membrane
3. Gene expression and protein synthesis

Question 11

Example of an endocrine organ: Pituitary gland

Answer 11

The pituitary gland is two glands fused together
- The posterior pituitary gland is neural tissue and secretes 2 neurohormones: vasopressin (antidiuretic hormone) and oxytocin
- the anterior pituitary gland is endocrine tissue and it secretes 6 true hormones
- hormones released from anterior pituitary are controlled by neurohormones from the hypothalamus

Question 12

Portal circulatory system

Answer 12

Specialized modifications where two sets of capillaries are connected in series by a set of small veins

Hypothalamic releasing hormone: thyrotropin releasing hormone (TRH) that goes into portal system that acts on specialized cells in anterior pituitary gland that will then release thyrotropin stimulating hormone (TSH)