B455 Hormones flashcards

Opera singer - "the last castrato"

- He was castrated before he reached sexual maturity to preserve his beautiful voice.

- He demonstrates the effect that hormones have on development (in this case, voice).

Organizational effect - occurs early in development, having permanent effects (ex. in uterus, testosterone masculinizes brain)

Activational effects - short-term hormonal effects - reversible. Effects of removing testes and reimplanting them in male roosters.

• 1. Inferred that a substance excreted by glands could affect targets at a distance (hormones)
• 2. 3 groups of roosters. (1) control-normal (2) removed testes --> "capones" did not replace (3) removed testes than reimplanted.

1 and 3 looked the same in terms of comb, mounting behavior, aggression, and crowing.

Because he surgically removed it from the normal site of the body - had not been reinnervated. Had to have been traveling through blood supply.

• 1. Reciprocal - there's a reciprocal relationship between hormones and behavior
• 2. Coordinating - hormones are coordinating molecules.
• 3. Hormones affect probability of behavior
• 4. Hormonal action occurs gradually with long-lasting effects
• 5. Hormones regulate their own secretion
• 6. Hormones are secreted cyclically.

• Hormone release changes behavior which changes experience which changes hormone release - cycle continues.
• 
• (loser effect - lower testosterone) - same in observing fans and sexual behavior.

• 1. Seen in organizational effects - coordination of physical morphology - affects secondary sexual characteristics.
• 2. Hormones travel at a distance and have many targets - allowing them to have widespread effects coordinating many functions and systems simultaneously.

• 1. CAUSE behavior
• 2. In a certain context (i.e., seasonal)
• 3. No, not a 1:1 ratio

• 1. Positive and negative feedback
• 2. Negative feedback: brain has set point for that time of day/year --> tells glands to secrete certain amount of hormone --> brain and glands detect that hormone and readjust signals accordingly
• 3. Positive feedback

1. Hormones are slower, longer-lasting and analog (wide secretions with wide effects)

2. Neural communication is faster, short-lasting, and binary (all-or-nothing)

Both use receptor mechanisms and chemical mechanisms.

Receptor mechanisms - structure of signaling molecules of hormones and neural pathways are the same, so response mechanisms will be the same!!!!!!

1. Aromatase (testosterone --> estradiol) and 5a-reductase (testosterone --> dihydrosteosterone)

If testosterone reaches cell expressing aromatase, will turn into estradio.

Important for sexual differentiation and behavioral/activational effects of testosterone

Peptide hormones - oxytocin, vasopressin, hypothalamic releasing/inhibiting, and leptin - like peptide NTs, expressed in cells genetically.

Amines - norepinephrine and melatonin - synthesized from AAs (no specific genes)

Steroids: androgens, estrogens, cortisol - hydrophobic, all derived from cholesterol, produced by a particular cell determined by which enzymes that cell expresses.

Androgen receptor - testosterone and dihydrotestosterone

Estradiol receptor - estradiol

progesterone receptors - progesterone

Androstenedione - testosterone precursor.

Hydrophilic - Binds to metabotropic receptors on cell surface activating secondary cascade - rapid effects. Can affect gene transcription.

Hydrophobic(steroids) - diffuse through plasma membrane, binds to receptor in cytoplasm, complex diffuses into nucleus, binds to hormone response element, eliciting transcriptional regulation. - slower.

• 1. Hypothalamus - controls hormone secretions
• 2. Pineal gland - reproductive maturation and bodily rhythms
• 3. Anterior pituitary - hormone secretion by thyroid, adrenal cortex, gonads, growth; posterior pituitary - water & salt balance
• 4. Thyroid - growth & development, metabolic rate.
• 5. Adrenal cortex - salt & carb metabolism, inflammatory rxns.

Corticosteroids, epinephrine, norepinephrine

• 1. Leptin
• 2. Signal of energy reserves
• 3. Increased leptin secretion - but doesn't have as much of an effect on obese people
• 4. Food intake (decreases)
• 5. Puberty and reproductive ability (both obese & underweight have difficulty getting pregnant b/c brain-pituitary-gonad (BPG) axis is very sensitive to energy levels.

• 1. Median eminence
• 2. To take chemical signals to interact with cells in anterior pituitary - it links the hypothalamic neurons and anterior pituitary.
• 3. Releases hormones into general circulation.
• 4. Tropic hormones act upon glands.

1. Reproduction

2. Triggered by external cues (light - best indicator of season, rainfall , temp etc) --> gonadal activity increases to prepare for breeding season (takes long time to change neural circuits, growing gonads, creating gametes) to enhance reproductive potential ---> most animals use this method.

• Example - red-sided garter snake.
• 1. Before hibernation
• 2. Right after hibernation
• 3. Prepares to make gametes again while gonads are still working
• 4. VERY SHORT - within hours of waking up after hibernation

• 1. Acts on gonads to release FSH and LH.
• 2. Gonadotropins
• 3. Because once it's active, it's tonically active until the end of the season.
• 4. Thermostat feedback model
• 5. Cyclically (in pulses every 1-2 hrs) - causes cyclic release of gonadotropins in pulses too. Through electrically coupled cells.

1. Castrated rat + DHT (dihydrotestosterone) - can restore secondary sexual traits (neurons in spinal cord that innervate penis), but no desire to reproduce bc no DHT action on brain.

• 2. Castrated rat + estradiol - restores sexual behavior, not peripheral sexual capacity
• 3. Testosterone- both sexual behavior and peripheral traits

No, because humans can reproduce without estradiol.

• 1. LH Surge
• 2. Negative feedback to pituitary.
• 3. Higher estradiol
• 4. Decreased latency between LH surges - more relaxed, less stressed
• 5. Ovulation and menstruation - previous menstruation and next ovulation.
• 6. Estradiol --> increases GnRH --> increases LH and FSH for the LH surge necessary for ovulation

• 1. Autonomic NS (specifically the sympathetic NS)
• 2. Timekeeper (helps shift from day to night) and keeps track of seasonal changes
• 3. In winter: longer nights --> less light --> more melatonin --> inhibition of BPG axis by increasing BPG sensitivity in brain to negative feedback.

Important for seasonal breeders. Thought to cause early puberty in humans.

4. Increased screentime --> decreased melatonin --> less inhibition of BPG axis --> overactivity leads to increased reproductive cancer rates

• 1. Medulla - sympathetic nervous system in autonomic NS. These hormones play a huge role in stress.
• 2. Stress --> CRH release (corticotropin releasing hormone - primary hormone for activating this axis) --> stimulates ACTH (adrenocorticotropic hormone) --> stimulates adrenal gland to produce corticosteroids.

• 1. Mineralocorticoids (aldosterone) - targets kidney for water & electrolyte balance.
• 2. Glucocorticoids (cortisol) - contributes to GNG and inhibits immune response (metabolically expensive system).

= To anticipate the need to recover homeostasis after stressor ends.

LOL ITS NOT HAHHAAHHA I TRICKED YOU - it's generally good bc it keeps animal alert and responsive to environment.

Chronic stress leads to long-term inhibition of immune response and inhibition of BPA axis. Cushing's disease occurs when cortisol produced by BPA is not detected by BPG and there is no negative feedback of ACTH.

You have high levels of glucocorticoids (no negative feedback and high levels of ACTH) and high levels of depression.

ACTH challenge - inject glucocorticoids/cortisol and measure changes in ACTH levels.

In a normal person, there would be an initial burst of glucocorticoids, followed by a decrease in ACTH and CRH


Chronic stress and cortisol inhibit neurogenesis in hippocampus. SSRIs and exercise by blocking stress's effects on neurogenesis.

Cortisol (glucocorticoids).