Lecture 1

Question 1

What is a gland?

Answer 1

A collection of cells that secrete a transmitter cell into the bloodstream with the aim of influencing target cells/tissues/organs.

Question 2

What is the endocrine system?

Answer 2

A system of ductless glands that secrete chemical messengers (hormones) into the blood. The hormones are then carried in the blood and are able to act on cells possessing the appropriate hormone receptors (target tissues). Each hormone may act on several target tissues.

Question 3

Where does the nervous system meet the endocrine system?

Answer 3

Hypothalamus

Question 4

What is the main function of the pineal gland?

Answer 4

Mostly circadian rhythm, more important in other animals (lizards) than humans

Question 5

What are other names for the pituitary gland and the stalk above it?

Answer 5

Hypophysis, or master gland. The stalk is infundibulum,

Question 6

What are the location and parts of the thyroid? What are its main functions?

Answer 6

Situated in neck (4 parathyroid to posterior of thyroid). Important in control of (thyroid) metabolic rate, maturation and (parathyroid) calcium homeostasis.

Question 7

What are the endocrine and exocrine functions of the pancreas?

Answer 7

Exocrine: Digestive enzyme release. Endocrine: Glucagon and insulin release.

Question 8

What are the adrenal glands also called? What are their parts and functions?

Answer 8

Suprarenal glands, divided into outer cortex for long-term stress, sodium, and glucose homeostatis and the inner medulla for short-term stress. Both secrete adrenaline.

Question 9

What are the gonads and their endocrine responsibilties?

Answer 9

Ovaries and testes, development of secondary sexual characteristics and reproductive cycle.

Question 10

How do hormones create change?

Answer 10

Hormones produce effects by interaction with receptors which may be intracellular or membrane bound.

Question 11

What are the major types of recptors involved in hormonal activity?

Answer 11

Steroid hormone receptors, G-Protein couple receptors, tyrosine kinase receptors.

Question 12

Describe steroid hormone receptors.

Answer 12

For steroid hormones (not water soluble, lipid soluble, from testes, ovaries, and adrenal cortex). Steroids are bound to plasma proteins to be transported through plasma (like water). Cross lipid membrane of cells (favorable to protein). Receptor carries to nucleus, where it influences gene expression and protein synthesis. Slow (order of days).

Question 13

Describe G-Protein coupled receptors.

Answer 13

Hormone binds to extra-cellular portion of receptor (7TM receptor), second messengers (cAMP for smooth muscle relaxation and IP3 for smooth muscle contraction) phosphorylate intracellular, regulatory protein to influence cellular activity.

Question 14

Describe tyrosine kinase (TK) receptors.

Answer 14

Typically single strand of protein, membrane-bound. Often 2 needed (dimerized). Hormone binds to extracellular portion, tyrosine is phosphorylated, causes intracellular portion to increase enzyme production. TKs typically involved with growth and development.

Question 15

What are the 2 broad classes of hormones?

Answer 15

Peptide hormones and steroid hormones (also, structurally dissimilar thyroid hormone but behaves like steroid hormone because lipid soluble)

Question 16

Describe peptide hormones.

Answer 16

not orally active (broken by digestive enzymes), highly water soluble, susceptible to protease attack, unable to cross cell membrane without carrier protein, act on membrane-bound receptors.

Question 17

Describe steroid and thyroid hormones.

Answer 17

Highly lipid soluble, must be transported inblood bound to plasma protein. Only unbound hormone bilogically active, able to cross cell membrane and act on intracellular receptors.

Question 18

How can you tell whether a hormone is peptide or steroid/thyroid?

Answer 18

Look at: water solublility (peptide is soluble, s/T fat soluble), oral activity (only S/T orally active, Peptide not), Look at short-ter/long-term activity (Peptides have rapid onset action, but short duration and short plasma half-life, while steroids have slow onset of action but high duration an high plasma half-life).

Question 19

What controls most hormone secretions?

Answer 19

Anterior pituitary gland via secretion of stimulating (stimulates a glad to release its hormone) or trophic (stimulates a gland to grow and produce more hormone) hormones.

Question 20

What controls the pituitary gland?

Answer 20

Hypothalamus via secretion of releasing hormones

Question 21

Give 3 examples of negative feedback in the endocrine system.

Answer 21

1-high levels of cortisol in the blood stop production of ACTH and CRH. 2- Thyroid hormone decreases secretion of TRH and TSH. 3- Oestrogens act to decrease secretions of GnRH and FSH.

Question 22

Explain negative feedback.

Answer 22

Negative feedback: counteraction of an effect by its own influence on the process giving rise to it.

Question 23

What is an unintended consequence of negative feedback in the endocrine system? Give one example

Answer 23

Cyclical variation in hormone concentration, so no steady level in bloodstream. Menstrual Cycle.