The endocrine system (Part 1)

Question 1

Compare/contrast the endocrine system and the nervous system.

Answer 1

The endocrine system’s responses are slower but longer lasting than those of the nervous system

Question 2

What does the endocrine system control and integrate?

Answer 2

Reproduction

Growth and development

Maintenance of electrolyte, water, and nutrient balance

Regulation of cellular metabolism and energy balance

Mobilization of the body’s defenses

Question 3

What’s the difference between endocrine and exocrine glands?

Answer 3

Exocrine Glands

• Produce nonhormonal substances (ex: sweat, saliva)
• Have ducts to carry secretions to membrane surfaces

Endocrine Glands

• Produce hormones
• Lack ducts

Question 4

Label the glands discussed in lecture as endocrine glands or both endocrine and exocrine glands.

Question 5

List the function of autocrines, paracrines, and hormones.

Answer 5

Hormones: long-distance chemical signals; travel through blood or lymph

Autocrines: chemicals that exert effects on the same cells that secrete them

Paracrines: locally acting chemicals that affect cells other than those that secrete them

Autocrines and paracrines are local chemical messengers – they are not considered part of the endocrine system

Question 6

What does it mean to be a target cell?

Answer 6

Target Cells: tissues with receptors for a specific hormone

Question 7

List the ways that a hormone can create change.

Answer 7

Alter plasma membrane permeability and/or membrane potential by opening/closing ion channels

Stimulate synthesis of enzymes or other proteins

Activate/deactivate enzymes

Induce secretory activity

Stimulate mitosis

?????

Question 8

What is the functional difference between water-soluble and lipid-soluble hormones?

Answer 8

Water-Soluble Hormones: all amino acid-based hormones except thyroid hormone

• Cannot directly enter a cell
• Act on plasma membrane receptors
• Typically, receptors are coupled to 1+ intracellular second messengers via regulatory molecules called G proteins

Lipid-Soluble Hormones: steroid and thyroid hormones

• Can directly enter a call
• Act on intracellular receptors that directly activate genes

Question 9

Does thyroid hormone function like a water-soluble or lipid-soluble hormone?

Answer 9

lipid-soluble hormone

Question 10

What is the purpose of a second messenger system? What is their function? List the 2 second messenger systems discussed in class.

Answer 10

…

• Cyclic AMP
• PIP2-Calcium

Question 11

What are the 5 steps for activating a second messenger? Look at the top image on slide 11!

Answer 11

Hormone (First Messenger) binds to receptor

Receptor activates a G Protein

G Protein activates or inhibits amplifier enzyme adenylate cyclase

Adenylate cyclase converts ATP to cAMP (Second Messenger)

cAMP activates proteins kinases that phosphorylate other proteins and generate responses within the cel

Question 12

In the cAMP pathway, G protein activates the enzyme _________________. In the PIP2-Calcium pathway, G protein activates the enzyme _________________.

Answer 12

adenylate cyclase

phospholipase C

Question 13

What happens when a lipid-soluble hormone enters a cell? Where does it go to create change?

Answer 13

Lipid-soluble steroid hormones and thyroid hormone can diffuse into target cells and bind with their intracellular receptors

Receptor-hormone complexes then enter the nucleus and bind to specific regions of the DNA

Binding helps to initiate transcription of DNA to produce mRNA

mRNA is then translated into specific proteins

The proteins synthesized have various functions – metabolic activities, structural purposes, or exportation from the cell

????

Question 14

Creation and release of most hormones is regulated by __________________________. Review what that means!

Answer 14

Negative feedback loops

Question 15

List 3 ways endocrine glands are stimulated to synthesize and release hormones. Give an example of each type of stimulus.

Answer 15

Humoral Stimuli - Example: Level of Ca2+ in Blood

Neural Stimuli - Example: in times of stress, fibers of the sympathetic nervous system stimulate the adrenal medulla to secrete catecholamines

Hormonal Stimuli - ??

Question 16

What is the hypothalamic-pituitary-target endocrine organ feedback loop? Outline how it works.

Answer 16

Hypothalamic hormones stimulate the release of most anterior pituitary hormones

Anterior pituitary hormones stimulate their targets to secrete still more hormones

Hormones from the final target organs inhibit the release of anterior pituitary hormones – the hypothalamic-pituitary-target endocrine organ feedback loop

???

Question 17

How does the nervous system modulate the activity of the endocrine system? Why is this useful?

Answer 17

The nervous system can adjust hormone levels when needed – can modify stimulation/inhibition of different endocrine glands

Nervous system can override mechanical endocrine controls

Question 18

List the 3 types of interactions between hormones affecting the same target cell? List an example of each type of interaction.

Answer 18

Permissiveness: one hormone cannot exert its effects without another hormone being present

Ex: reproductive hormones need thyroid hormone to have effect

Synergism: more than one hormone produces the same effects on the target cell – causes amplification

Ex: glucagon and epinephrine both cause the liver to release glucose

Antagonism: one or more hormones oppose(s) the action of another hormone

Ex: insulin and glucagon