HPG Axis

nervous system

physical contact- structures for communication

sensory output/input= helps animal react to internal/external environment

rapid, short-lived responses

endocrine system

body fluid used to transport messages (hormones)

helps maintain internal environment

longer lasting response

hormones

chemical substance produced by ductless glands and secreted into the blood supply to affect a tissue distant for the gland

ligand (an actor)

agonist

can bind and create a response

antagonist

binds and prevents a response

autocrine signaling

requires hormone release (not into blood)

hormone acts on the cell that created it

paracrine signaling

hormone acts on neighboring cell

endocrine signaling

requires hormonal release into the blood

travels through the blood to find right match

neuroendocrine signaling

hormone is produced by neuron, goes into blood

amines

derived from tryptophan or tyrosine

ex: thyroid hormones

protein and peptides

derived from amino acids

ex: growth hormones, prolactin, LH

prostaglandins

derived from arachidonic acid

ex: prostaglandin F2a

steroids

derived from cholesterol

ex: estradiol, testosterone, cortisol, progesterone

negative feedback

hormone binds, decrease of downstream effect

ex: “hitting the breaks”

positive feedback

hormone binds, increases downstream effect

ex: “go, go, go”

hypothalamus

base of the brain

the control center for reproductive hormones (GnRH)

several different nuclei

anterior hypothalamus

optic chiasma

posterior hypothalamus

mammillary bodies

dorsal hypothalamus

thalamus

ventral hypothalamus

sphenoid bone

pituitary gland

known as the hypophysis

found in the sella turcica of the sphenoid bone

two main parts; anterior/posterior lobe

anterior lobe of pituitary gland

adenohypophysis

posterior lobe of pituitary gland

neurohypophysis

pars distalis

main hormonal production site

produces gonadrophs

FSH + LH

pars intermedia

produces melanocytes stimulating hormone