Endocrine System Flashcards
(28 cards)
List the 4 characteristics of hormones.
- Hormones are chemical messengers
- They travel through the bloodstream
- They act on target cells with specific receptors
- They regulate physiological processes
Do nearly all organs of the body release hormones?
Yes, almost every organ releases hormones, even if it is not an endocrine gland.
Define target cell.
A target cell is a cell that has specific receptors for a particular hormone.
Define receptor (for a hormone).
A receptor is a protein on a target cell that binds to a hormone, allowing the cell to respond.
True or False: A target cell must have the appropriate receptor for a hormone to respond.
True
Explain why the same hormone can have different effects on different tissues.
Different target cells may have different receptors, signaling pathways, or enzymes that alter the hormone’s effect.
Give an example of a hormone that has different effects on different tissues.
Epinephrine causes vasodilation in skeletal muscles but vasoconstriction in the intestines.
Distinguish lipophobic and lipophilic hormones.
- Lipophobic (water-soluble): bind to receptors on the cell membrane
- Lipophilic (fat-soluble): pass through the membrane and bind to intracellular receptors
Contrast how lipophobic and lipophilic hormones are transported in the blood.
- Lipophobic hormones dissolve in plasma
- Lipophilic hormones require carrier proteins
Identify where the receptors of the target cell are located for lipophobic and lipophilic hormones.
- Lipophobic hormones: Cell membrane receptors
- Lipophilic hormones: Intracellular receptors (in cytoplasm or nucleus)
Describe how a target cell can reduce its response to a hormone.
By downregulating receptors (reducing receptor number or sensitivity).
Distinguish 4 hormone-hormone interactions.
- Antagonistic: Hormones have opposite effects (e.g., insulin vs. glucagon)
- Additive: Two hormones together have a greater combined effect
- Permissive: One hormone allows another to function effectively
- Synergistic: Two hormones amplify each other’s effects
List the 3 general mechanisms that control endocrine reflexes (hormone secretion).
- Humoral stimuli: Changes in blood levels (e.g., glucose → insulin release)
- Neural stimuli: Nerve signals (e.g., stress → adrenal gland activation)
- Hormonal stimuli: One hormone triggers another (e.g., hypothalamus → pituitary)
Describe the role of the hypothalamus in controlling endocrine organs.
The hypothalamus controls hormone release from the pituitary gland and regulates other endocrine organs.
True or False: Not all endocrine glands are controlled by the hypothalamus.
True
Describe the role of feedback loops in controlling endocrine secretions.
- Negative feedback: Hormone release decreases once the desired effect is achieved
- Positive feedback: Hormone release increases (e.g., oxytocin in childbirth)
Recognize that some feedback loops are initiated by the nervous system.
The nervous system can directly stimulate hormone release (e.g., adrenal medulla in stress).
Define clearance.
Clearance is the removal of hormones from the bloodstream.
Describe 2 general ways that hormones can be cleared from the body.
- Enzymatic breakdown (in liver/kidneys)
- Excretion (through urine or bile)
Describe the location, hormones, and effects of (primary) endocrine glands and organs.
- Pituitary gland: Growth hormone, ADH, etc.
- Thyroid: Metabolism control via thyroxine
- Adrenal glands: Stress hormones (cortisol, adrenaline)
- Pancreas: Insulin & glucagon (blood sugar regulation)
Identify endocrine glands controlled by the hypothalamus and those that are not.
- Controlled: Pituitary, thyroid, adrenal cortex, gonads
- Not controlled: Pancreas, parathyroid glands
Describe two differences between the anterior and posterior pituitary.
- Anterior: Produces its own hormones
- Posterior: Stores and releases hormones made by the hypothalamus
Describe two differences between the adrenal medulla and cortex.
- Medulla: Releases epinephrine (fast stress response)
- Cortex: Produces cortisol and aldosterone (long-term stress, water balance)
Distinguish the effects of insulin and glucagon.
- Insulin lowers blood sugar (cells absorb glucose)
- Glucagon raises blood sugar (liver releases glucose)
