Lecture 28 - Chapter 16 - Endocrinology

Question 1

What is the difference between endocrine and exocrine glands?

Answer 1

• Endocrine glands are duct-less that produce chemical messengers called hormones.
• Exocrine have ducts that carry secretion to membrane surface. They produce nonhormonal substances like : sweat and saliva

Question 2

The hypothalaums is a neuroendocrine organ. What does that mean?

Answer 2

That is has some endocrine and exocrine functions.

Question 3

Besides the hypothalamus, what other organs/tissues produce hormones?

Answer 3

1. Adipose cells
2. Thymus
3. Cells in walls of small intestine
4. Stomach
5. Kidneys
6. Heart

Question 4

BLANK are long distance chemical signals that travel in the blood or lymph.

Answer 4

Hormones

Question 5

What are the two classes of hormones?

Answer 5

1. Amino acid-based (Oxytocin & ADH)
2. Steroids (made from cholesterol; they’re gonadal and adrenocortical hormones)

Question 6

Hormones will only affect cells that have a receptor for a specific type of hormone. What is the hormone action on target cells? What happens to a cell once a hormone binds to its hormone receptor?

Hormone A will interact with receptor A. Hormone A will NOT interact with receptor B

Answer 6

Possibilities are:
* Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels
* Stimulate synthesis of enzymes or other proteins
* Activate or deactivate enzymes
* Induce secretory activity
* Stimulate mitosis

Question 7

Hormones act in one of two ways, depending on their chemical nature and receptor location. What are the two ways?

Answer 7

1. Water-soluble hormones (all amino-acid based hormones except thyroid hormones)
   * Act on plasma membrane receptors
   * Act via G-protein secondary messengers
   * CAN NOT ENTER THE CELL
2. Lipid-soluble hormones
   * Act on intracellular receptors that directly activate genes
   * CAN ENTER THE CELL

Question 8

What is the main secondary-messenger system for amino-acid based hormones?

Answer 8

Cyclic AMP

Question 9

Image of Lipid-soluble hormones (Steroid and Thyroid hormones) acting on intracellular receptor.

Answer 9

Question 10

Blood levels of hormones are controlled by negative feedback systems. What does this mean?

Answer 10

Increased hormone effects on target organs can inhibit further hormone release.

Question 11

What causes hormones to be released?

Two ways

Answer 11

1. Endocrine gland stimuli
2. Nervous system modulation

Question 12

Endocrine gland stimuli can be triggered by three different ways. What are they?

Answer 12

1. Humoral stimuli: changing blood levels of ions and nutrients directly stiumlate secretion of hormones
2. Neural stimuli: nerve fibers stimulate hormone release (Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines)
3. Hormonal stimuli: hormones stimulate other endocrine organs to release their hormones

Question 13

What is the hypothalamic-pituitary-target?

This involves the hormonal stimuli of endocrine glands.

Answer 13

Hormones from final target organs inhibit the release of anterior pituitary hormones.
Without this, hormones will keep sending a positive feedback loop to the anterior pituitary. This tells it to stop sending out the hormone.

Question 14

What is the nervous system modulation?

Answer 14

• The nervous system can make adjustments to hormone levels when needed
• Can override normal endocrine controls (Ex. under severe stress, hypothalamus and sympathetic nervous system override insulin to allow blood glucose to increase aka prepare for fight or flight)

Question 15

Like we mentioned, hormones will only bind to their specific target cell receptors. But there are three factors that determine if the hormone will actually activate the target cell. What are the three factors?

Answer 15

1. Blood levels of hormone
2. Relative number of receptors on/in target cell
3. Affinity (strength) of binding between receptor and hormone

Question 16

Hormones can influence the number of receptors for that hormone.
What are the two ways target cells change their receptors based on the amount of hormone in circulation?

Answer 16

1. Up-regulation: target cells form more receptors in response to low hormone levels
2. Down-regulation: target cells lose receptors in response to high hormone levels

Question 17

What type of hormones are bound to something while circulating in the blood?

Answer 17

Lipid-soluable proteins (steroids & thyroid hormones) are attached to plasma proteins

All other hormones circulate without carriers.

Question 18

Image of comparison between Lipid and Water soluble hormones

Answer 18

Question 19

Multiple hormones may act on same target at the same time.

BLANK: one hormone cannot exert its effects without another hormone being present.

Answer 19

Permissiveness

Question 20

Multiple hormones may act on same target at the same time.

BLANK: more than one hormone produces same effects on target cell, causing amplification. (Ex: glucagon and epinephrine both cause liver to release glucose)

Answer 20

Synergisim

Question 21

Multiple hormones may act on same target at the same time.

BLANK: one or more hormones oppose action of another hormone. (Ex: insulin and glucagon)

Answer 21

Antagonism

Question 22

The hypothalamus secretes releasing and inhibiting hormones to the BLANK so that it regulates hormone secretion.

Answer 22

Anterior pituitary

Question 23

In the posterior pituitary there are two axon terminals: Paraventricular and supraoptic.
What do those two axon terminals do?

Answer 23

1. Paraventricular neurons produce oxytocin
2. Supraoptic neurons produce antidiuretic hormone (ADH)

Question 24

Oxytocin and ADH are each made up of nine amino acids but they differ in two of them. What are the two amino acids that are different?

Answer 24

Question 25

What are the functions of oxytocin?

Answer 25

• Strong stimulant of uterine contractions
• Hormonal trigger for milk ejection
• Positive feedback mechanism
• Neurotransmitter in the brain

Question 26

What are the functions of ADH?

Answer 26

• Targets kidney tubules to reabsorb more water to inhibit or prevent urine formation
• Release is also triggered by low blood pressure and drugs
• Inhibited by alcohol, diruetics
• High concentration of ADH causes vasoconstriction (increases blood pressure)

Question 27

Image of Oxytocin and ADH comparison

Answer 27