Chemical Messengers
•Autocrine•self signal
•Paracrine•neighbor signal
•Endocrine•distant signal
•Pheromone•airborne signal•same species
•Allomone•airborne signal•different species
Homeostasis Mechanism
Receptorsinput signalsskin responds to cold temperaturesends signal to brain
Control Centerintegrating centerbrain interprets temp signalmakes you shiver
Effectorsoutput mechanismmuscles shiver creating heat
Negative Feedback
Results in an immediate reversalof the imbalanced system
Immediately negates thedisruption
Most systems in the body workvia negative feedback systems
temperatureglucose balancewater balanceblood pressure
Positive Feedback
Immediate further disruption of theimbalance so as to later return tohomeostasis
childbirthovulation
Neuroendocrine ReflexBaby suckling stimulates receptors on the nipple
Action potential travels to the hypothalamus
Hypothalamus sends oxytocin to posterior pituitary gland
Posterior pituitary releases oxytocin into the blood stream
Oxytocin travels to the breast and triggers milk release
Posterior Pituitary
Hormones synthesized in thehypothalamus
Released by the posterior pituitary
•Oxytocin•milk ejection•orgasm
•Vasopressin or ADH•water balance•blood pressure
Anterior Pituitary
Releasing hormones synthesizedin the hypothalamus
•CRF/CRH•GnRH•GHRH•TRH•PRH
Triggers hormone release in anterior pituitary
•ACTH•LH/FSH•GH•TSH•PRL
Stress The process by which we perceive and respond to certain events, called stressors, that we appraise as threatening or challenging
Stress Diathesis ModelExisting Correlations:
•Adult Depression : Elevated Cortisol levels•Childhood Abuse : Adult Depression
Stress Diathesis Model:•Genetic Predisposition plus•Early Abuse/Neglect leads to •Adult Depression
Animal Model shows:•More CRF neurons•Larger CRF neurons•More sensitive CRF neurons
Early abuse permanently alters the stressresponse increasing the risk of depression