Exam 3: The Endocrine System Flashcards
What does the endocrine system do?
- Regulates and controls many metabolic processes
- Helps maintain body homeostasis
- e.g., maintaining blood glucose levels during erratic food intake
- Serves as one of the two major control systems of the body
- with the nervous system
What is the endocrine system composed of?
Endocrine glands located throughout the body
What do endocrine glands do?
- synthesize and secrete hormones
- released into the blood and transported through the body
- Very active in small amouts
What is a Hormone?
Mediator molecule released from one part of the body but regulates the activity of cells in other parts of the body
What is the difference between exocrine and endocrine?
Exocine secretes OUT of the body, endocrine secretes IN the body.
What happens when the Target cell binds it’s hormone?
Initiates or inhibits selective activities.
What are target cells?
Cells with a specific receptor for a hormone
What are the features of the endocrine system that are different than the nervous system?
–Hormones transported within blood to target cells
–Causes metabolic changes in target cells
–Target any cells with receptors
–Exhibit longer reaction times
–More widespread effects throughout the body
–Longer-lasting effects (minutes to days and weeks)
What are the features of the endocrine system that are in common with the nervous system?
–Release chemical substances, ligands
–Bind to cellular receptor on particular target cells
–Initiates cellular change in target cells
What are the general functions of the Endocrine System?
- ) Maintaining homeostasis of blood composition and volume
- )Controlling reprodictive activites
- ) Regulating development, growth, and metabolism
- ) Controlling digestive processes
–Maintaining homeostasis of blood composition and volume
- regulate amount of substances dissolved in blood
- e.g., glucose, cations, anions
- regulate blood volume, cellular concentration, and platelet number
–Controlling reproductive activities
- affect development and function
- affect expression of sexual behaviors
–Regulating development, growth, and metabolism
- regulatory roles in embryonic cell division and differentiation
- involved in catabolism and anabolism of proteins, carbohydrates, and lipids
–Controlling digestive processes
- influence secretory processes
- influence movement through digestive tract
What is an endocrine organ?
single organ that is entirely endocrine in function
What are some of the endocrine organs?
- pituitary gland
- pineal gland
- thyroid gland
- parathyroid glands
- adrenal glands
Endocrine Cells Within Other Organs
–Housed in tissue clusters in specific organs
–Secrete one or more hormones
- organ with additional primary function
What are some of the endocrine cells within other organs?
- hypothalamus, skin, thymus
- heart, liver, stomach
- pancreas, small intestine
- kidneys, gonads
Hormones affect only specific target cells that have the necessay for the hormone to bind
Receptor
Receptors constantly synthesized and degraded in order to modulate effect of hormone
Down-regulation
Up-regulation
What are the hormone types?
Circulating
Local Hormones
Circulating Hormones
circulate in blood throughout body – affect target tissues
Local Hormones
–act locally
- Paracrine
- Autocrine
Paracine
Act on neighboring cells
Autocrine
Act on the same cell that secreted them
What are the chemical classes of hormones?
Lipid-soluble
Water-soluble
Lipid- Soluble
•Do not readily dissolve in blood and therefore must be attached to a carrier protein while being transported in the blood
–Steroids
–Thyroid hormones T3 and T4
–Nitric oxide (NO)
Water-Soluble
•Readily dissolve in blood and therefore circulate in “free” form without a carrier protein
–Amine
–Peptide/ protein
–Eicosanoids
Circulating Hormones
Local Hormones
Lipid Soluble Hormone
How does the lipid soluble hormone get into the cell?
- The unbound lipid-soluble hormone diffuses through the plasma membrane and binds with an intracellular receptor, (either within the cytosol or the nucleus) to form a hormone-receptor complex.
- The hormone-receptor complex then binds with a specific DNA sequence called a hormone-response element.
- This binding stimulates mRNA synthesis.
- mRNA exits the nucleus and is translated by a ribosome in the cytosol. A new protein is synthesized.
Endocrine Reflexes
- Regulated secretion of hormone controlled through reflex
- Usually negative feedback system
- There are a few examples of positive feedback systems
- Preprogrammed response to certain stimuli
Endocrine Reflexes are initiated by which types of stimulation?
hormonal, humoral, or nervous
Hormonal Stimulation
- e.g., thyroid stimulating hormone released from anterior pituitary
- stimulates thyroid gland to secrete thyroid hormone
Humeral Stimulation
- respond to changing level of nutrients or ions
- act on target cells to offset further loss or eliminate excess
Nervous Stimulation
e.g., release of epinephrine and norepinephrine by adrenal medulla in response to sympathetic nervous stimulation
Types of receptors on target cells
- Membrane Bound Receptors
- Intracellular Receptors
Membrane Bound Receptors
– In plasma membrane of target cell
– Water soluble hormones are the ligand
– Binding activates intracellular signaling cascades
Intracellular Receptors
_Inside of the cell somewhere (cytosol or nucleus)
– Lipid soluble hormones are the ligand
– Binding alters gene expression – increase in mRNA
synthesis (transcription)
What are the three different results of water soluble hormones binding to membrane-bound receptors?
- Alteration of membrane permeability
- Activation of G proteins
- Receptors linked to intracellular
enzymes through intracellular mediators
Alternation of Membrane Permeability
Activation of G-Proteins
– Binding of some water-soluble hormones causes activation of G- proteins
– Initiate series of biochemical events, signal transduction pathway
- initiated by the hormone, the first messenger
– Docking results in formation of second molecule
- termed second messenger
- modifies some cellular activity
GTP=
ON
GDP=
OFF
