Anatomy II - Endocrine Physiology Flashcards
What is the function of the Endocrine System?
Secreting and producing hormones (chemical messengers)
Endocrine vs Nervous System
Nervous system:
- Effects are immediate
- Releases neurotransmitters to target cells
- Operates through series of NEURONS
Endocrine System:
- Hormones effect is longer-lasting and can take place within seconds, hours, or days.
- Releases Hormones into bloodstream
Describe the route hormones take to get to the target cell.
- Hormones are secreted into interstitial fluid, then diffuse into blood capillaries.
- Blood transports hormones to the heart via the veins.
- After leaving the heart, blood transports hormones to rest of the body via the arteries.
- In the capillary beds, the hormones diffuse out of the blood, into the interstitial fluid, and then bind onto the target cell receptors.
Endocrine signaling vs Paracrine signaling vs Autocrine signaling
Endocrine: Hormones are released into the bloodstream and travel LONG DISTANCES to target distant organs or tissues.
Paracrine: Hormones or signaling molecules act on nearby cells in the local area (SHORT DISTANCE).
Autocrine: The cell secretes a hormone or signaling molecule that acts on ITSELF (the SAME cell that produced it).
What are antagonists?
Two hormones that work against each other, opposing or counteracting one another’s effects.
Ex: Calcitonin lowers blood calcium levels, while parathyroid hormone raises them
What are Synergists?
Two or more hormones that work together to produce a stronger or more effective outcome.
Ex: Epinephrine and norepinephrine: Work together to increase the heart rate
Define: Amin-acid Hormones
hormones that are derived from amino acids (the building blocks of proteins). They are hydrophilic (water soluble) and bind to plasma membrane receptors.
Define: Steroid Hormones
Hormones derived from cholesterol, and are lipid-soluble & hydrophobic. They bind to receptors in cytosol or nucleus.
Three dimensional shapes are _____ specific for the hormone molecule that they bind to.
HIGHLY
Where are hormones embedded/reside in?
Embedded in plasma membrane and reside in cytosol or within nucleus of the target cell.
Hydrophilic hormones _____ cross plasma membrane while _______ hormones ________ cross through plasma membrane
CANNOT; HYDROPHOBIC; CAN
Hormone Action Mechanism: Up-Regulation
Target cell produces more receptors when hormone in blood decreases
Hormone Action Mechanism: Down-Regulation
Target cell decreases receptors when hormone in blood is high.
Explain the steps of the process of a Hydrophilic Hormone Signaling
- Hydrophilic hormone binds to receptors on plasma membrane.
- Receptors activate G-protein
- G-protein activates enzyme which creates the formation of the secondary messenger. (ex: G-protein activates AC enzyme which forms cAMP.)
- Secondary messenger initiates series of events within the cell that leads to changes in activity.
Explain the steps of the process of a Hydrophobic Hormone Signaling.
- Hydrophobic Hormone crosses plasma membrane & interacts with receptors on cytosol or nucleus of target cell.
- Hormone then forms complex with receptor (interacts with DNA)
- Complexes changes rate of protein synthesis of one or more proteins
Hormones continue to circulate in the blood stream UNTIL _______ or ______.
Taken up by target cell or broken down & deactivated.
How are hormones inactivated rapidly?
Reactions catalyzed by enzymes
What does the amount of a hormone within the bloodstream at a given moment depend on?
- How fast & how much of the hormone the endocrine gland produced
AND - How fast secreted hormone is removed from the blood
How are hormones inactivated slowly?
Eliminated in urine from the KIDNEYS and/or broken down by enzymes within the LIVER.
What does the rate at which hormones are eliminated depend on?
It depends on structure and degree of binding to proteins.
Define: Half-Life
Amount of time it take plasma concentration of hormone to reduce by half.
Who has the longer and shorter half lives between Hydrophobic and Hydrophilic hormones?
Hydrophobic hormones have longest half life (a week or more) because of protein-binding
while,
Hydrophilic hormones have shorter half lives (few minutes to seconds)
Describe a negative feedback pathway in a simple endocrine pathway.
Stimulus: Physiological Level changes from normal range
Receptor: Endocrine cell receptors detect the change
Control Center: Endocrine Cell increases or decreases stimulation of the particular hormone.
Effector/Response: Hormone triggers response that brings conditions back to normal range.
Why are hydrophilic hormones not able to cross through the plasma membrane unlike hydrophobic ones?
The phospholipid bilayer does not allow for hydrophilic hormones to pass through so they have to bind to receptors on the plasma membrane.
Humeral vs Hormonal vs Neural Stimulation
Humeral is anything BUT a hormone & neuron that releases a hormone because of something that is not a hormone.
Hormonal is when Hormones cause other hormones to be released.
Neural Stimulation is when an electrical impulse is sent via the nerves in order to cause the release of a hormone.
