Vertebrates 20 - Endocrine Flashcards
5 ways of chemical signaling
Autocrine, paracrine, endocrine, neruoendocrine, exocrine
Endocrine
Go through bloodstream to travel to target
Neuroendocrine
Stimulated and release hormones into blood. Neurons from hypothalamus
Exocrine
Especially pheromones, sensed by another organism
Peptides and proteins
Small. Insulin, ADH. Bind to membrane receptors.
Amines
From amino acids, epinephrine and thyroxine. Bind to membrane receptors
Steroids
From cholesterol. Testosterone, estrogen, cortisol. Hydrophobic so they have carrier proteins and then diffuse through membrane
Pituitary gland/Hypophysis
Ant. and Post. Controlled by the hypothalamus
Hypothalamus
Homeostatic mechanisms: hunger, thirst, temp. Responds to brain inputs (stress, circadian rhythms, etc).
Anterior pituitary
Adenohypophysis. Releases TSH, FSH, LH, GH, Prolactin (milk and some brain), ACTH, MSH. Connected by a portal system to hypothalamus which sends hormone messages.
Posterior pituitary
Neurohypophysis. Nerves from hypothalamus enter and release hormones from there. ADH and oxytocin.
Agnatha endocrine
Hypothalamus, less obvious pituitary. No distinct adrenal or thyroid glands.
Chondrichthyes endocrine
More developed pituitary. Adrenal in separate places, cortex (suprarenal - cortisol) and medulla (interrenal - adrenalin).
Osteichthyes endocrine
Pituitary lacks portal system but has nerve connection to hypothalamus. Adrenal glands together but in multiple places.
Amphibian endocrine
Portal system present. thyroxine stimulates metamorphosis
Reptilia endocrine
One pair of adrenal glands
Aves endocrine
Prolactin stimulates crop milk (secretion to feed young in some birds). 10x Glucagon, more thyroxine for higher metabolism
Catabolic and anabolic pathways
Catabolic breaks down, so lower body weight (cortisol, thyroxine); anabolic builds (testoterone)
Know the thyroid, cortisol and testosterone axes
Hypo - TRH - Ant Pit - TSH - Thyroid - Thyroxine - shut off the others, increase metabolism. … ACTH - Adrenal - Cortisol - shut these off; Hypothalamus - GnRH - Ant Pit - LH - Testes - Testosterone - build muscle etc, turn off the other
Effects of hormones (general)
Cell response and also trophic effects (growth of cells)
Why use male castrated animals in endocrine testing?
Females have hormone cycles that can complicate results; castrate to eliminate testosterone
