1. April 28, 2014 – Chemical signals and hormones II
Announcements:
Lab this week will meet in the computer labs
Final Exam: May 15
ICES evaluation
Pre-lecture quiz
Review of cell-to-cell signaling & thyroid hormones (T3 & T4)
Specificity
Lipid soluble hormones – Steroids
G-coupled protein receptors –
Tyrosine kinase receptors
Hormone-mediated physiological tradeoffs

2. Endocrine systems are regulated by negative feedback
Endocrine pathway
Neuroendocrine pathway
Neuroendocrine-to-endocrine pathway
Stimulus
Stimulus
Stimulus
Endocrine cell
Endocrine
signal
Sensor cell
Sensor cell
Feedback inhibition
Effector
cell
Feedback inhibition
Feedback inhibition
Neural signal
Neural signal
Response
CNS
CNS
Neuroendocrine
signal
Neuroendocrine
signal
Effector
cell
Endocrine cell
Endocrine
signal
Response
Effector
cell
Response

3. Chemical characteristics of hormones – major classes
Peptides and Polypeptides
Amino Acid
Derivatives
Steroids
Secretin
Epinephrine
Cortisol
Receptor
Receptor
Not lipid soluble;
bind to receptors on
surface of target cell
Most not lipid soluble;
bind to receptors on
surface of target cell
Lipid soluble;
bind to receptors
inside target cell
Receptor
Target cell

4. Hormone Transport and Action on Target4 4

5. Hydrophobic messengers pass into cell where they bind with transcription factors which affect gene expression.

6. Hydrophilic hormones bind to a receptor on the cell membrane which causes several reactions known as a signal transduction
pathway. This can affect the properties of enzymes/proteins, etc. or it may affect gene expression.

7. Thyroid Hormone Thyroid hormone: - Actually two hormones (T3/T4)
Mammals mainly secrete T4
- but some T4 is converted under certain
circumstances
- Same receptor binds both,
but ↑affinity for T3
T3/T4 are membrane soluble
- ↑metabolism in muscles, heart, liver & kidney T4 T3

9. Figure 47-8 T3 T3 Juvenile frog (tadpole) Adult frog Locomotion
Swim via movements of muscular tail
Locomotion
Tailless; walk or hop
Respiration
Gas exchange occurs in gills, across skin,
and in lungs
Respiration
Gas exchange occurs across skin, and in
lungs
Nutrition
Most are herbivorous; have a long gut
specialized for digesting algae and plants
Nutrition
Most are carnivorous; have a large mouth
or long tongue for catching prey; short gut
specialized for digesting proteins
Excretion
Most nitrogenous wastes excreted as
ammonia
Excretion
Most nitrogenous wastes excreted as urea

11. Thyroid hormone levels go up as flat fish go through this metamorphosis.

12. Anadromous versus Resident Stream Sticklebacks
Higher metabolic rates
Migrate from ocean to freshwater to breed
Bigger
Lower metabolic rates
Permanent residents in freshwater
Smaller

13. Take home message: The same hormone can have multiple physiological effects
How do we explain this?

14. Altering individual behaviors by altering overall thyroid levels seems like a pretty blunt way to go about changing specific phenotypes.
How could this system be fine-tuned to optimize specific traits under different contexts?
A.) changes in TRH expression
B.) changes in TSH expression
C.) alterations of TSH receptors
D.) alteration of T3/T4 receptors in specific cell types.

16. Hormonal specificity: G-protein coupled receptors

17. Hormonal specificity: G-protein coupled receptors

18. Hormonal specificity: Tyrosine kinase receptors

19. Hormonal specificity: Steroids and gene transcription
STEROID HORMONE ACTION
Nucleus
Hormone
receptor
mRNA
Proteins
DNA
Steroid
hormone
Hormone-
response
element
RNA
polymerase
Hormone-receptor
complex
3. Hormone-receptor
complex enters
nucleus and binds
to DNA, induces
start of transcription.
4. Many mRNA
transcripts are
produced,
amplifying
the signal.
Ribosome
1. Steroid
hormone
enters
target cell.
2. Hormone binds
to receptor, induces
conformational
change.
5. Each transcript is
translated many times,
further amplifying the
signal.

20. Hormone-mediated Tradeoffs: Interactions between stress, reproduction and immune function
Extraordinary ordinary Junco:

21. Hormone-mediated Tradeoffs Interactions between stress, reproduction and immune function

22. Stress

23. Short-Term Stress Response
“Fight or flight” response is stimulated by epinephrine

24. Figure 47-7a-hypothesis

25. Figure 47-7b-setup

27. Some additional effects of the “fight or flight response
1.) Redirection of blood flow from the skin and digestive system toward heart, brain, and muscles.
2.) Relaxation vascular smooth muscle to aid in vasodilation
Take home message:
1.) Short term stress responses are EXTREMELY beneficial over the short term.
2.) Prolonged stress responses can be harmful.
*Radio Lab episode on stress:

28. Long term stress responses

30. This graph shows the . . .
a. Positive influence ACTH has on cortisol release
b. Inhibitory feedback of cortisol on ACTH release

31. This graph shows the . . .
a. Positive influence ACTH has on cortisol release
b. Inhibitory feedback of cortisol on ACTH release

33. ACTH also stimulates the release of aldosterone
ACTH also stimulates the release of aldosterone. Why should this be a part of the stress response?