Endocrine System Flashcards
How hormones work
Hormones are secreted into the circulatory system
Hormones reach all parts of the body, but only affect cells that have a receptor for that hormone
Nervous system vs. endocrine system
Nervous system: fast and wired (ex-muscle contraction)
Endocrine system: slower and wireless (ex- growth and reproduction)
Endocrine signaling
Hormones are released into the blood and trigger signals anywhere
Paracrine signaling
Molecules trigger cells nearby
Autocrine signaling
Molecule triggers itself
Synaptic signaling
Neurotransmitter released from synapse triggers cell
Neuroendocrine signaling
Neurohormones released into blood from nerves trigger cells anywhere
Difference between endocrine and exocrine glands
Endocrine: ductless organs, release into bloodstream
Exocrine: ducts, release into a lumen
Tropic hormone
Causes release of other hormone
Path of hormone secretion
- Neurosecretory cells of hypothalamus secrete first hormone
- First hormone travels down portal vessels to anterior pituitary gland
- Endocrine cells of anterior pituitary gland release second hormone
- Second hormone travels out of anterior pituitary and into general circulation
- Second hormone triggers target cells to release their hormones
- Hormones from target cells take effect
3 major classes of hormones
Polypeptides and peptides (water soluble)
Amines (water soluble)
Steroids (lipid soluble)
Water soluble secretion pathway
Hormone is released from cell by exocytosis -> travels through bloodstream on its own (no carrier needed) -> binds to signal receptor on outside of target cell -> cytoplasmic response or gene regulation
Lipid soluble secretion pathway
Hormone diffuses through plasma membrane -> travels through bloodstream via protein carrier -> binds to signal receptor inside target cell -> gene regulation -> cytoplasmic response
Positive feedback
Reinforces stimulus, but must have end point
Example: oxytocin causes stretching of cervix -> more oxytocin -> more cervix stretching (endpoint: baby born)
Negative feedback
Decreases stimulus
Example: high glucose in blood causes release of insulin -> insulin causes decrease of glucose in blood
Insulin
Decreases blood glucose (causes body cells to take up glucose and causes liver to store glucose as glycogen)
Produced in pancreatic beta cells
Peptide
Glucagon
Increases blood glucose (causes liver to break down glycogen and release glucose into blood): opposite of insulin
Produced in pancreatic alpha cells
Peptide
Diabetes mellitus
Caused by deficiency of insulin or a decreased response to insulin in target tissues
Problem: elevated blood glucose levels
Damage to capillaries in kidneys, eyes, and feet
Become dehydrated
Type 1 diabetes mellitus
Autoimmune disorder: immune system destroys pancreatic beta cells
Juvenile onset
Treatment: insulin injections
Type 2 diabetes mellitus
Insulin deficiency or reduced response of target cells due to change in insulin receptors
Adult onset
Obesity is common cause
Treatment: diet and exercise (cells take up glucose)
Thyroid hormone
Pair of hormones: Triiodiothyronin (T3; 3 iodine atoms) and Thyroxine (T4; 4 iodine atoms)
Controls body metabolism
Steroid
Thyroid hormone cascade
TRH (thyrotropin-releasing hormone; hypothalamus) -> TSH (thyroid stimulating hormone; anterior pituitary) -> TH (thyroid hormone)
TH inhibits TSH and TRH
Hypothyroidism
Too little thyroid function
Symptoms: weight gain, lethargy, cold intolerance
Hyperthyroidism
Excessive production of thyroid hormone
Symptoms: high temperature, sweating, weight loss, irritability, high blood pressure
Graves’ Disease
Form of hypothyroidism caused by autoimmunity
Symptom: protruding eyes
Goiter
Enlarged thyroid gland caused by insufficient dietary iodine
