ANHB1102 Lecture Notes - Lecture 6: Lipophilicity, Negative Feedback, Homeostasis
24 May 2018
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Endocrines & Homeostasis:
Homeostasis: the maintenance of a constant internal environment despite a variable external
environment.
- Short term (minute to minute) – blood pressure and
body temperature
- Medium term (hours to days) – physical activity, food
intake, sleep
- Long term – body weight, blood pressure
Requires communication:
- Negative feedback
Hormones:
Are ligands – bind to specific receptors:
- Target organ defined by receptors
Steroid hormones
- Bind to intracellular receptors
- Signal pass directly into cell
- Eg. Testosterone and cortisol. (small molecular weight,
highly lipophilic)
Peptide hormones
- Bind to membrane receptors.
- Signals mediated by 2nd messengers.
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Neural interactions:
Brain impacts function of most endocrine organs
- Effects mediated by pituitary gland
- Neural and vascular connections between brain and
pituitary important.
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find more resources at oneclass.com
Hypothalamus-pituitary Portal System:
Primary Hormone targets:
Nutrition
Why is the regulation of blood glucose so important?
- Low glucose comprise brain function
- High glucose damage vessels and nerves
- Homeostatic responses ensure appropriate glucose levels despite intermittent fuel supply and
variable rates of use.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Homeostasis: the maintenance of a constant internal environment despite a variable external environment. Short term (minute to minute) blood pressure and body temperature. Medium term (hours to days) physical activity, food intake, sleep. Testosterone and cortisol. (small molecular weight, highly lipophilic) Neural and vascular connections between brain and pituitary important. Homeostatic responses ensure appropriate glucose levels despite intermittent fuel supply and variable rates of use. Low blood glucose (hypoglycemia) a cells secrete glucagon glucagon stimulates glycogenolysis rise in glucose levels. B cells secrete insulin insulin stimulates tissue uptake of glucose and glycogenesis fall in blood glucose. Hyperglycemia (elevated blood glucose) glycosuria (glucose in urine) Type 1: inability to produce sufficient insulin (insulin-dependent diabetes mellitus (iddm)) Treated by self-monitoring of blood glucose and provision of exogenous insulin. Type 2 reduced responsiveness to insulin (non-insulin dependent diabetes mellitus (niddm)) New drugs targeting insulin action (ppar activators) Evolutionary perspective of nutrition: fitness defined by survival and reproduction.
