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Endocrine SystemHormones
& Homeostasis
Regulation How we maintain homeostasis
nervous system nerve signals control body functions
endocrine system hormones chemical signals control body functions
Nervous vs. Chemical Regulation of Homeostasis
Nervous System Endocrine System
Mode of action
Neurons and neurotransmitters
Glands and hormones
Speed of action
Quick Slow
Duration of action
Short Long
Specificity Targets specific organs
Carried to all organs of the body
OBJ 47
A few glands… Pituitary
many hormones: master gland
Controlled by the hypothalamus
Pancreas insulin, glucagon
Stomach gastrin
Ovary Estrogen,
progesterone Testes
testosterone
Responding to hormones Lock and key system
hormone fits receptor on “target” cell
targetcell
non-targetcells
secretingcell
can’tread
signal
can’tread
signal
2 Hormone Signaling Pathways Protein hormones
Hydrophilic/water-soluble
Bind to a receptor on cell membrane
Activate secondary messengers
Steroid hormones Hydrophobic/lipid-
soluble Go through cell
membrane Bind to receptors
INSIDE the cell
OBJ 48
Hormone Signaling Pathways
Protein hormones
Steroid hormones
OBJ 48
Regulation of Hormone Secretion Antagonistic hormone pairs maintain
homeostasis through negative feedback Analogy: thermostat Examples: blood sugar level, blood
calcium level, acid in stomach.
OBJ 49
liver
pancreas
liver
Regulation of Blood Glucose
blood glucose level(90mg/100ml)
insulin
liver cells take
up glucosefrom blood
liver storesglucose as glycogen
(dehydration synthesis)
glucagon
pancreas
liver breaks glycogen into glucose (degradation
hydrolysis) and releases into blood
high
low
Negative FeedbackEndocrine System Control