ANHB1102 Lecture Notes - Lecture 17: Hypophyseal Portal System, Sex Steroid, Anterior Pituitary
25 May 2018
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Homeostasis Notes:
Homeostasis:
-maintenance of constant internal environment despite variable external environment
-Short term (minute to minute): blood pressure, body temperature
-Medium term (hours to days): physical activity, food intake, sleep
-Long term: body weight, blood pressure
-Requires communication between cells
Classes of Hormones:
-Hormones are ligands - bind to specific receptors (target organ is defined by the receptors it
expresses)
-Steroids: bind intracellular receptors
-Derived from cholesterol molecule; small weight, hydrophobic, cross bi-lipid membrane
-Peptides: bind membrane receptors
-Peptide hormone signals are mediated via ‘2nd messengers’ - mediate effect of hormone
inside cell
-Large; cannot cross membrane
Peptide Hormone Action (requires 2nd messengers):
Steroid Hormone Action:
-Hypothalamus: synthesises
hormones
-Penal Gland: melatonin - regulates
light/dark cycles
-Gonads + Testes: sex hormones
-Thyroid Gland: metabolism
-Thymus: immune system
-Adrenal Glands: adrenaline
-Pancreas: blood sugar levels,
endocrine and exocrine
Endocrine - Neural Interactions:
-The brain impacts on the function of most
endocrine organs
-Effects are mediated via the pituitary gland
-Neural and vascular connections between brain
and pituitary both important
Document Summary
Maintenance of constant internal environment despite variable external environment. Short term (minute to minute): blood pressure, body temperature. Medium term (hours to days): physical activity, food intake, sleep. Hormones are ligands - bind to speci c receptors (target organ is de ned by the receptors it expresses) Derived from cholesterol molecule; small weight, hydrophobic, cross bi-lipid membrane. Peptide hormone signals are mediated via 2nd messengers" - mediate effect of hormone inside cell. Penal gland: melatonin - regulates light/dark cycles. Pancreas: blood sugar levels, endocrine and exocrine. The brain impacts on the function of most endocrine organs. Effects are mediated via the pituitary gland. Neural and vascular connections between brain and pituitary both important. Hypothalamic releasing hormones stimulate anterior pituitary hormones. Anterior pituitary: not directly connected to brain. Posterior pituitary: connects to brain through neural pathways. Low blood glucose levels compromise normal brain function (only fuel used by the brain) High blood glucose levels damage blood vessels and nerves.
