Lecture 4: Endocrine System Flashcards
Major Components of the Endocrine system and their Basic functions
Pineal gland
body rhythms; sleep, hunger, maturation
Hypothalamus & Pituitary gland
o part of same system, structurally linked
o in charge of controlling the rest of the system
o “start of the cascade”
Thyroid
o growth and development
o metabolism
Pancreas
o metabolism of sugar, production of insulin
Gut (G.I. tract)
o hunger
o satiety
HPA-axis
Hypothalamus – Pituitary – Adrenal (HPA) Axis
o emotional arousal
o metabolism (adrenal glands are attached to the kidneys–near the stomach)
o inflammation
- Over release of adrenal gland → panic attack
- Underperformance→ fatigue, depression, weight loss
HPG-axis
Hypothalamus – Pituitary – Gonads (HPG) Axis
o reproductive hormones
estrogen, progesterone, testosterone [among others]
Hormones, general
- similar to drugs, hormones travel through the vascular system and affect multiple areas
- hormones connect on more than one organ
- each organ can be sensitive to more than one hormone
Hormones Operate on a Feedback Loop:
Experience→change in hormone levels→ change in behavior→ change in experience
Posterior Pituitary
o oxytocin – milk for breast-feeding
o vasopressin – blood pressure, water retention
o both oxytocin and vasopressin are considered social hormones as they promote attachment
Anterior Pituitary
o Release of TROPICS [etym tropics “downward]–which cause hormone release in other parts of the system
o Reproductive
• follicle stimulating hormone (FSH)
• luteinizing hormone (LH)
o Non-Reproductive • growth hormone • thyroid stimulating hormone (TSH) • adrenocorticotropin (ACTH) • cortisol • epinephrine • norepinephrine
Reproductive hormones
Follicle stimulating hormone (FSH)
• release of estrogen, stimulates maturation of ova
• maturation of sperm
Luteinizing hormone (LH)
- triggers ovulation
- in males, triggers production of testosterone
- works synergistically with FSH
Non-Reproductive Hormones
- growth hormone
- thyroid stimulating hormone (TSH)
- adrenocorticotropin (ACTH)
- cortisol
- epinephrine
- norepinephrine
Epinephrine
o Increases blood pressure
• constricts vascular system [water hose analogy]
o metabolizes glucose and proteins for more energy (similar to cortisol), but major effect is on vascualar system
Adrenocorticotropin (ACTH)
Principal effects are increased production and release of corticosteroids–“stress hormones” e.g. Cortisol
Norepinephrine
o increases flow of blood [not through vascular constriction]
o conscious experience of stress
• more related to cognitive response
Cortisol
o steroid which “ramps up” the sympathetic nervous system
o stimulates metabolism
o increases heart rate
o *can also disrupt reproductive strength if cortisol levels persists over time
Homeostasis
- consistent physiological state
- active maintenance of our internal system
• maintaining a neutral state
o energy, temperature, fluids, salt concentration
• general idea – we have a “set point” of homeostasis
o more of a target range than a specific point
• system works through “negative feedback”–activated by information which communicates you are not where you are supposed to be
4 kinds of bodily fluids
intracellular fluid
&
extracellular fluids:
• intravascular
• cerebrospinal fluid [acts as a cleaning mechanism]
• interstitial fluid [between all cells, not just neurons]
Osmometric Thirst
o leaking fluid out of system
o fluid leaves intracellular becomes interstitial
o caused by excess sodium, overconsumption
o osmosensory neurons in hypothalamus trigger release of thirst hormones
Volumetric Thirst
o overall loss of bodily fluid
o loss of blood volume→ drop in blood pressure
o baroeceptor in heart [think barometer]
• response to drop in blood pressure
- stimulates posterior pituitary to release vasopressin for water conservation
- limits fluids to kidney
- decreased urge to urinate
- strongly concentrated urine
o volumetric thirst increases desire for salts which then increase desire for water and also helps retain the water
Basal Metabolic Rate
85% of total energy is used just to keep you alive
when we talk about changes in metabolism, we are really talking about changing the basal metabolic rate
[only 15% energy is diverted toward active use]
Glucose
o metabolized by the pancreas
o liver converts glucose into glycogen for long term storage (more stable form)
- glycogen is only a storage form, cannot be used
- when energy is needed, pancreas converts glycogen to glucose
Lipids
o triglycerides are converted into adipose tissue for long-term storage
o adipose cells create leptin, a hormone which tracks how much fat we have in our bodies
• leptin→ “satiety hormone”
• when the system is not functioning properly, fat cells either don’t recognize leptin or the leptin receptors are nonexistent
o as a last resort, when no fat is left/no energy is available, muscle tissue is converted into triglycerides
• this also releases ketones, a toxic byproduct
• ketones may cause breath to become sweet
• clinical implication—when ED is suspected, may be useful to check breath for sweetness
Hypothalamus (individual eating episodes)
o lateral hypothalamus: creates appetite
o ventromedial hypothalamus: controls satiety
• tells you when your full
• lesion to the ventromedial hypothalamus results in chronic hunger [mnemonic VH: Very Hungry without Ventromedial Hypothalamus]
o magnitude of signal is mediated by leptin levels
Gut & appetite
o stomach releases Grehlin when you haven’t eaten in a long time
[*mnemonic: Grehlin, stomach is “growlin”]
Intestines: PYY 3-36
• Acts to suppress appetite
• Since it’s farther down the GI tract, takes longer for pyy3-36 to be released→ which is why one reason the advice for weight loss is to eat slower, to allow more time for the appetite to suppressed, in turn helps to prevent overeating
