A/P 2 chapter 17
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what is the composition of the endocrine system?
Endocrine glands, lack ducts, and product is released directly into the blood
What is the main function of the endocrine system?
synthesis and release of hormones. Controls many activities of the body: homeostasis, controlling reproductive activities, regulating development, growth, metabolism and digestion
What are some similarities of the endocrine and nervous system?
They both release ligands in response to stimuli that bind to target cells
What is a target cell?
Cells with a specific receptor for a hormone
what is a ligand?
a ligand is a chemical substance (hormone or neurotransmitter) that is released by the endocrine or nervous system
What do the nervous system effect?
it affects two specific locations by means of neurons and neurotransmitters
What does the endocrine system affect?
The endocrine system has widespread effect and uses blood for distribution of hormones
How does the nervous system affect the body?
It has a rapid effect, but it is short lasting
how does the endocrine system affect the body?
Slow effect but longer lasting
Communication method of the nervous system?
Neurons release neurotransmitters into a synaptic cleft to stimulate their target cells
Communication method of endocrine system
hormones are secreted by endocrine cells. The hormones enter the blood and travel throughout the body to reach the target cells
What is the general functions of the endocrine system?
- Maintaining homeostasis of blood composition and volume
- Controlling reproductive activities
- Regulating development, growth, and metabolism
- controlling digestive processes
Composition of endocrine glands?
- epithelium-derived endocrine cells and connective tissue
- organization of cells differ between glands, but they have an extensive blood supply
What are the glands considered as endocrine organs?
- Pineal gland
- Pituitary gland
- thyroid gland
- Parathyroid gland
- Adrenal gland
What are some organs with main function other than the endocrine?
- small intestine
What does the pineal gland do?
- Hormones produced: melatonin
- Function: helps regulate the body's circadian rhythm
What does the posterior pituitary do?
- Hormones produced: Oxytocin (OT), Antidieuretic Hormone (ADH)
- Functions: Uterine contractions; breast milk release (OT)
- Fluid balance (ADH)
Anterior pituitary hormones
- Thyroid-stimulating hormone (TSH)
- Prolactin (PRL)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocorticotropic hormone (ACTH)
- Growth Hormone (GH)
Thyroid-stimulating hormone (TSH)
stimulates thyroid gland to release thyroid hormone
Breast milk production
Follicle-stimulating hormone (FSH)
Development of gametes (and follicle in female)
Luteinizing hormone (LH)
Development of gametes (and ovulation in female)
Adrenocorticotropic hormone (ACTH)
stimulates adrenal cortex to release corticosteroids
stimulates cell growth and division
- Anterior pituitary release thyroid stimulating hormone.
- TSH stimulates thyroid gland to release Thyroid hormone (TH)
- Blood glucose levels increase
- increased blood glucose stimulates pancreas to release insulin
- Sympathetic nervous system increases in activity
- Sympathetic preganglionic axons stimulate adrenal medulla to release epinephrine and norepinephrine
What are some circulating hormones?
- Steroid hormones
- Protein hormones
- Biogenic amines
- from cholesterol, therefore lipid soluble
- hormones from gonads and adrenal cortex
- from amino acids, therefore water-soluble
- consists of 3 groups: polypeptides, oligopeptides, and glycopeptides
- monoamines, modified amino acids
- hormones of adrenal medulla and thyroid hormone
What are local hormones?
- Large group of signaling molecules that do not circulate within the blood. They have a local effect
- may either affect the cell that produced the hormone (autocrine stimulation) or neighboring cells (paracrine stimulation
Example of a local hormone
Transport of lipid soluble hormones
- do not dissolve in blood plasma
- require carrier proteins that ferry the hormone through the blood (also offer protection from degradation)
- hormone must detach to be able to exit the blood and affect the target cell
- most lipid-soluble hormone is in bound state (90-99.9%)
Transport of water-soluble hormones.
- dissolves in blood plasma, and are transported easily
- many bind to protein carriers for protection
Levels and effects of hormones
Effect of hormones is directly related to the amount of hormone presented in blood, this is to prevent potential clinical consequences
what are two things that affect levels of hormone in the blood?
- hormone synthesis
- hormone elimination
- occurs in endocrine gland
- if rate of synthesis and release increase than the concentration of hormone w/in the blood is greater and vice versa
- degradation by enzymes usually in liver
- elimination by kidneys
- uptake of hormone by target cells
Interactions of target cells with hormones
- depends on composition of hormone
- a specific hormone generally has different types of target cells
Interactions of target cells with hormones: Lipid soluble hormones
- hormone slips easily inside the cell through the cell membrane
- forms hormone-receptor complex (either in cytosol or in nucleus)
- binds to hormone-response element (in nucleus)
- initiates transcription of mRNA
- translation of mRNA results in a protection that may alter the cell activity of cell structure
Interactions of target cells with hormones: water soluble hormones
Cannot cross the cell membrane, interacts with receptors on the outside
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