Endocrinology - Lecture 1

Question 1

Which two major systems represent the two major means by which physiological activities are coordinated?

Answer 1

CNS and endocrine system

Question 2

How is communication between cells that are not in contact happen?

Answer 2

through a number of chemical substances that interact with specific receptors on distant target cells

Question 3

What does endocrine signalling involve?

Answer 3

hormone secretion into the blood by an endocrine gland

Question 4

How are hormones transported to a distant target site?

Answer 4

by the blood

Question 5

What are the 7 steps in neuroendocrine signalling?

Answer 5

1. stimulus
2. hypothalamus secretes hormone A
3. hypothalamo-pituitary portal vessels increase plasma hormone A
4. anterior pituitary secretes hormone B
5. plasma hormone B increases
6. third endocrine gland secretes hormone C
7. target cells of hormone C respond to hormone C

Question 6

What are the 2 kinds of signalling?

Answer 6

paracrine and autocrine

Question 7

How does paracrine signalling work?

Answer 7

• Cells release signaling molecules (e.g., hormones, growth factors) into the extracellular fluid.
• These signaling molecules then travel short distances to target cells located nearby.
• The target cells have receptors for the signaling molecules and respond to them, but they are typically different cells from the ones that released the signaling molecules.

Question 8

How does autocrine signalling work?

Answer 8

• Cells release signaling molecules that act on receptors present on the same cell or cells of the same type.
• The cell signals itself or other cells of its own type.
• This type of signaling can be involved in self-regulation or coordination of activities within a population of similar cells.

Question 9

What are the 6 steps of communication by hormones (or neurohormones)?

Answer 9

(1) Synthesis of the hormone by endocrine cells (or neurons in case of neurohormone).
(2) Release of the hormone by the endocrine cells (or the neurohormones by the neurons).
(3) Transport of the hormone or neurohormone to the target site by the blood stream.
(4) Detection of the hormone or neurohormone by a specific receptor protein on the target cells.
(5) A change in cellular metabolism triggered by the hormone-receptor interactions
(6) Removal of the hormone, which often terminates the cellular response

Question 10

What are the “classical endocrine organs”?

Answer 10

1. brain (hypothalamus, anterior/posterior pituitary
2. thyroid and parathyroid glands
3. ANP
4. adrenal glands (cortex and medulla) and pancreas (islets of langerhans)
5. ovaries and testes

Question 11

How does hypothalamic-pituitary signalling happen?

Answer 11

via blood vessels of the pituitary stalk

Question 12

Where is the hypothalamic-hypophyseal portal system located?

Answer 12

from the hypothalamus to the adenohypophysis (anterior pituitary)

Question 13

What is the function of hypothalmic neurohormones?

Answer 13

they either activate or inhibit the activity of one of the six types of hormone-producing cells in the anterior pituitary

Question 14

What are the two kinds of hypothalmic neurohormones?

Answer 14

releasing hormones or inhibiting hormones

Question 15

What are the 4 classes of the hormones?

Answer 15

1. peptides and proteins (glycoproteins and polypeptides)
2. steroids
3. amines
4. ionic calcium

Question 16

What are the 5 locations in the synthesis of protein hormones?

Answer 16

1. synthesis on ribosomes
2. rough endoplasmic reticulum
3. golgi apparatus: prehormones packaged into secretory vesicles
4. vesicles: storage of hormone
5. co-release of hormone + other peptides

Question 17

What is the hormone called in the ribosome during synthesis of protein hormones?

Answer 17

preprohormones

Question 18

What do preprohormones turn into in the rough ER?

Answer 18

prohormones

Question 19

What do prehormones turn into in the golgi apparatus?

Answer 19

hormone + other peptides

Question 20

What are the 4 most common steroids?

Answer 20

1. cortisol
2. aldosterone
3. testosterone
4. estradiol

Question 21

What are the 3 kinds of thyroid hormones?

Answer 21

1. tetraiodothyronine (T4)
2. triiodothyronine (T3)
3. triiodothyronine (rT3; reverse T3)

Question 22

Which thyroid hormone is the most popular?

Answer 22

tetraiodothyronine T4 (90%)

Question 23

Which thyroid hormone is the least popular?

Answer 23

triiodothyronine rT3 (0.9%)

Question 24

What are the 4 properties of hormone receptors?

Answer 24

(A) SPECIFICITY: RECOGNITION OF SINGLE HORMONE OR HORMONE FAMILY.


(B) AFFINITY: BINDING HORMONE AT ITS PHYSIOLOGICAL CONCENTRATION.


(C) SHOULD SHOW SATURABILITY; I.E. A FINITE NUMBER OF RECEPTORS.


(D) MEASUREABLE BIOLOGICAL EFFECT: A MEASURABLE BIOLOGICAL RESPONSE DUE TO INTERACTION OF HORMONE WITH ITS RECEPTOR.

Question 25

How can receptors be regulated?

Answer 25

upregulated or downregulated

Question 26

How can receptors be upregulated?

Answer 26

either by increasing their activity in response to hormone or their synthesis

Question 27

How can receptors be downregulated?

Answer 27

by decreasing their activity or their synthesis

Question 28

What are the 3 mechanisms by which a hormone can exert effects on target cells?

Answer 28

(1)Direct effects on function at the cell membrane.
(2)Intracellular effects mediated by second messenger systems.
(3) Intracellular effects mediated by genomic or nuclear action.

Question 29

How is hormone secretion precisely regulated?

Answer 29

by feedback mechanisms

Question 30

What does an excess of hormone or excess hormonal activity lead to?

Answer 30

a diminution of hormone secretion

Question 31

What does a deficiency or a hormone lead to?

Answer 31

an increase in hormone secretion

Question 32

What acts in a negative feedback loop to regulate plasma calcium levels?

Answer 32

calcium

Question 33

What increases CRH?

Answer 33

hypothalamus

Question 34

What increases ACTH?

Answer 34

anterior pituitary

Question 35

What increases cortisol?

Answer 35

adrenal cortex