April 30, 2014 – Chemical signals and hormones III

1. No Pre-lecture quiz2. Review of Hormone specificity3. Hormone-mediated physiological tradeoffs4. Stress responses5. Introduction to sex hormones

Hormonal specificity: G-protein coupled receptors

Animation of g-protein coupled receptor example

http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter17/animation__membrane-bound_receptors__g_proteins__and_ca2__channels.html

Hormonal specificity: Tyrosine kinase receptors

Animation of tyrosine kinase receptors

• https://www.youtube.com/watch?v=apkY5c5DjlM

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

Extraordinary ordinary Junco: http://juncoproject.org/videos/chapter-2/

Stress

Stress response

Operates via two interrelated systems:

• SAM (Sympathetic-adrenomedullary) (Short Term Response)

• HPA (hypothalamic-pituitary-adrenocortical) (Chronic Response).

Adrenal Glands

Adrenal glands• On top of the kidneys• Two parts:

– Outer covering (cortex)– Inner part (the medulla)

• Both parts secrete stress hormones

Adrenals

Short term response

SAM – short term stress response

• Adrenal medulla (the inner part) releases epinephrine (adrenaline) and norepinephrine

• Stimulates rapid mobilization of metabolic resources: increased heart rate, BP, blood glucose

• "Rapid response"

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 pulmonary smooth muscle to dilate bronchi and increase O2 uptake

Take home messages:

1.) Short term stress responses are EXTREMELY beneficial over the short term.

2.) Prolonged stress responses can be harmful.

*Radio Lab episode on stress: http://www.radiolab.org/story/91580-stress/

Long term response

HPA axis and glucocorticoids

• Adrenal cortex produces glucocorticoid hormones (GC).

• Cortisol is most important human (GC), involved in regulating metabolism, immune response, and general homeostasis.

• Elevated cortisol leads to:– Short term metabolism of fat stores into

glucose– Increased hunger– Suppression of immune response;– Cardiovascular changes (e.g. increases in

BP)

HPA axis and the stress response

• Hypothalmus secretes CRH, which:

– causes the pituitary to secrete ACTH,

– which stimulates the adrenal medulla to

release epinephrine and norepinephrine

– and the adrenal cortex to release GC.

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

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

Hormone-mediated TradeoffsInteractions between stress, reproduction and immune function