Introduction

Question 1

3 systems of regulation/communication within the organism

Answer 1

-SNC
-Endocrine system
-Inmunologic system

Question 2

General characteristics of SNC

Answer 2

-Allows for adaptation to the environment
-Respons is fast, targeted, and sustained

Question 3

Where is a hormone released?

Answer 3

Always to the bloodstream

Question 4

Characteristics of the endocrine system

Answer 4

-Nanomolarity: action in distant locations at low concentrations
-Latency: can go from minutes to hours
-One cell can be both a receptor and a recipient

Question 5

Parameters necessary for a correct hormonal response

Answer 5

-Receptor present and functioning
-Transport between secretor and receptor (steroids)
-Good affinity of attachment (Kd)
-Rate of degradation
-Elimination via kidney filtration

Question 6

The hypothalamus is special because…

Answer 6

It’s a neuroendocrine neuron. This means it is a neuron that receives messages from the environment, but the response is always hormonal.

Question 7

Historical periods of endocrinology

Answer 7

-Anatomo-clinic → definition of nature and physiological function (by using ablation and opotherapy)
-Endocrine biochemistry → isolation, identification of the structure, and hormone synthesis. Isolation of insulin.
-Molecular endocrinology → identification of mechanisms of action.

Question 8

Experiment of BAYLISS and STARLING

Answer 8

Demonstrated that acid instilled into the duodenum caused exocrine pancreatic secretion despite severing the duodenal and pancreatic nerves.
Further, they showed that an extract of duodenal mucosa injected into the animal mimicked the acid effect in the duodenum.
These were remarkable discoveries because they demonstrated that the intestine can release substances into the blood that have effects on other organs challenging the prevailing concept of “nervism”.

Question 9

What did SUTHERLAND discover?

Answer 9

That AMPc is the second messenger for hormones.

Question 10

Rhythmic fluctuations of hormone levels, how do we classify them?

Answer 10

-By their period
-By their dependency on the environment
REINBERG

Question 11

Parameters of hormone secretion

Answer 11

-Acrophase: the peak of secretion
-Bathyphase: lowest point of secretion

Question 12

Classification of periodes

Answer 12

-Ultradian: <24h. High frequency <1 min, low frequency >1 min
-Circadian: 20 heures < x <28 heures. Here falls the majority of endocrine hormones
-Circannual: Humans don’t have them anymore. Species who hibernate do.

Question 13

Ultradian rhythms

Answer 13

-Rapid and independency from the environment
-Tied to the genetical constitution
-Internal clock of peripherical organs

Question 14

Circadian rhythms

Answer 14

-The majority
-Tied to environmental cues
-Internal central clock

Question 15

Where is the “internal central clock”

Answer 15

It’s a region of the hypothalamus = noyau suprachiasmatique (NSC).
Without it, there is no rhythm. And without external cues, the rhythm lasts 25,2h.

Question 16

Regulation by light exposure

Answer 16

1. Direct via optic nerve form retine to NSC
2. Indirect via genes sensitive to luminous variations. (Gene PER1)
3. Via melatonin: inhibited by light. Acrophase during the night and secreted by the pineal gland.

Question 17

Predictive homeostasis

Answer 17

The hormonal variation takes place a bit before the variation itself. They make sure to maintain relative consistency.

Question 18

Reactive homeostasis

Answer 18

Hypothalamus responds in two ways to stress:
-Nervous: Rapid, fight or flight
-Hormonal: Slow, can have a long duration

Question 19

The rhythm of cortisol and ACTH

Answer 19

Nycthemeral. ACTH has acrophase a few minutes before cortisol does.

Question 20

The rhythm of testosterone

Answer 20

Nycthemeral. An older and young man have more or less the same average production, but the amplitude becomes lower in an old man.
Production is ultradian.

Question 21

Importance of the cicles

Answer 21

-GnRH is continuously prescribed to males with prostate cancer to block the reproductive system. To women, it is prescribed in a pulsatile manner to help ovulation.
-ACTH is less effective when injected depending on the time of the day.