May 2, 2014 – Chemical signals and hormones IV
Announcements:
- Final is NOT CUMULATIVE*
- In lecture review session (Wed. May 7)
- TA led review session (10am – 12pm, Wed. May 14, 151 Everett Lab
1.
2.
3.
4.
5.
Pre-lecture quiz
Review of stress responses
Hormone-mediated physiological tradeoffs
Interactions between the HPA and HPG axes
Sex hormones
* I will ask about recurrent themes (e.g. tradeoffs, negative feedback, etc.)
Stress response
Operates via two interrelated systems:
• SAM (Sympathetic-adrenomedullary)
(Short Term Response)
• HPA (hypothalamic-pituitaryadrenocortical) (Chronic Response).
SAM, adrenals, and epinephrine
Summary of the “fight or flight” response
1.) Increases in HR, BP, O2 consumption, blood glucose and fatty
acid concentrations.
2.) Redirection of blood flow from the skin and digestive system
toward heart, brain, and muscles.
3.) 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.
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)
Feedback inhibition by cortisol on ACTH
Hypothalamus
Pituitary gland
Adrenal
gland
Figure 47-15
Stressed
individual
Unstressed
individual
Hormone-mediated Tradeoffs
Interactions between stress, reproduction and immune function
Hormone-mediated Tradeoffs:
Interactions between stress, reproduction and immune function
Testosterone treated
Control
Territory size
Larger
Smaller
Singing frequency
Higher
Lower
# of aggressive interactions
Higher
Lower
Number of matings
Higher
Lower
Number of offspring
Higher
Lower
Offspring quality
Lower
Higher
Survival
Lower
Higher
Hormone-mediated Tradeoffs:
Interactions between stress, reproduction and immune function
Montane
Urban
Breeding season
Shorter
Longer
Aggressiveness
Higher
Lower
Male parental investment
Higher
Lower
Testosterone
Higher
Lower
Cortisol
Higher
Lower
Stress response
Higher
Lower
Hormone-mediated Tradeoffs
Interactions between stress, reproduction and immune function
HPG axis
Gonads
• Male testes produce sperm cells
• Female ovaries produce ova
• Fertilization
– Sperm cell + ovum = zygote
• Sex chromosomes
– Humans: XX = female, XY = male
– Birds: ZW = female, ZZ = male
– Many vertebrates lack sex chromosomes entirely
Sex Hormones – Released by Gonads
• Androgens - e.g., testosterone (“male” hormones)
• Estrogens - e.g., estradiol (“female” hormones)
• Adult testes release more androgens and ovaries more
estrogens
• Progestins – also present in both sexes
– progesterone prepares uterus and breasts for pregnancy
• Adrenal cortex – also releases sex steroids
HPG axis & Reproductive System
Males
Also known as Leydig cells
Steps for spermatogenesis
1. GnRH released at hypothalamus -----> + section of FSH & LH at anterior pit.
2. a. FSH stimulates sertoli cells which stimulate spermatogenesis
b. LH simulates Leydig cells which secrete testosterone
Testosterone stimulates sertoli cells to stimulate spermatogenesis
3. a. testosterone has negative effects on GnRH
b. testosterone has negative effects on LH & FSH
c. Sertoli cells release inhibin which has negative effects on LH & FSH
HPG axis & Reproductive System
Males
Females
Figure 48-12
5. Degeneration of
corpus luteum
Secondary oocyte
to oviduct
4. Ovulation
Oocytes
Follicle
cells
3. Maturation of
follicle
1. Formation of primary
oocytes within follicles
2. Follicle growth
Figure 48-13-2
FOLLICULAR PHASE
Follicle growth
LUTEAL PHASE
Ovulation
Corpus luteum degeneration
Pituitary
hormone
cycle
Hormone levels
Ovarian
cycle
LH
FSH
0
7
14
Days
21
28
Figure 48-14
FOLLICULAR PHASE
LUTEAL PHASE
Ovulation
Follicle growth
Corpus luteum degeneration
Progesterone
Follicles and
corpus luteum
secrete
hormones
Estradiol
Negative
feedback
on LH
Positive
feedback
on LH
Negative
feedback
on LH,
FSH
Ovarian hormones and
pituitary hormones exert
feedback on each other