NURS 1750 Lecture Notes - Lecture 8: Pancreatic Polypeptide, Eicosanoid, Cortisol
28 Jun 2018
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Week Ten (November 20 - 25, 2017)
Anatomy and Physiology
Chapter Eighteen: Endocrine System
Control by the Nervous System and Endocrine Systems
- Nervous and Endocrine systems work together to coordinate all
systems of the body
- Nervous system releases neurotransmitters
- Endocrine system releases hormones
- Both hormones and neurotransmitters bind to receptors on “target
cells.”
Endocrine vs. Exocrine Glands
Exocrine
- Secrete products into ducts
- Empty onto the surface - skin
- Harmful if enters the bloodstream
Three Types:
- Merocrine
- Secretory vesicles via exocytosis
- Most exocrine glands of the body
- Salivary glands and pancreas
- Apocrine
- Secretory product- pinches off by
exocytosis
- Release the secretion (sweat, mammary)
- Holocrine
- Secretory product (oily substance) it
ruptures
- Contains large amounts of lipids
(sebaceous)(hair follicles)
Endocrine
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- Endocrine glands secrete hormones
- Secrete into the interstitial fluid
surrounding the secretory cells, rather
than into ducts. From the ISF,
hormones diffuse into blood.
- They are then distributed throughout
the body by the bloodstream
(circulating hormones)
- Endocrine glands include the pituitary,
thyroid, parathyroid, adrenal and
pineal glands.
Hormone Activity
- Hormones only affect target cells that
possess specific protein receptors. Hormones
(like neurotransmitters) influence their target
cells by chemically binding to specific protein
receptors.
- Example: Thyroid-Stimulating Hormone (TSH) binds to
receptors on cells of the thyroid gland, but it does not bind to
cells of the ovaries because ovarian cells do not have TSH
receptors.
-Receptors: are continually being synthesized
and broken-down (based on demand).
- Receptors, like other cellular proteins, are
constantly being synthesized and broken down.
- If a hormone is present in excess, the number of
target-cell receptors may decrease—an effect
called down-regulation. For example, when
certain cells of the testes are exposed to a high
concentration of luteinizing hormone (LH), the
number of LH receptors decreases.
- Down-regulation makes a target cell less
sensitive to a hormone.
- In contrast, when a hormone is deficient, the
number of receptors may increase. This
phenomenon, known as up-regulation, makes a
target cell more sensitive to a hormone.
Circulating and Local Hormones
- Circulating hormones are carried through
the bloodstream to act on distant target cells.
- Local hormones, act locally on neighboring cells or on the same cell that
secreted them without entering the bloodstream
- Paracrines are local hormones that act on neighboring cells. (don’t circulate)
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Week Ten (November 20 - 25, 2017)
- Autocrines act on the same cells that produced/secretes them.
- An example of a local hormone is interleukin-2 (IL-2), which is released by helper
T cells (a type of white blood cell) during immune responses.
- IL-2 helps activate other nearby immune cells, a paracrine effect.
- It also acts as an autocrine by stimulating the same cell that released it
to proliferate. This action generates more helper T cells that can secrete
even more IL-2 and thus strengthen the immune response.
Tropic
Hormones
→
Endocrine gland
working on another
endocrine.
- Have other endocrine organs as their target
- Most tropic hormones are produced and secreted
by the pituitary gland
- Adrenocorticotropic hormone (ACTH) from anterior
pituitary gland stimulates the cortex of the adrenal
gland (another endocrine gland) to secrete
glucocorticoids.
Chemical Class of Hormones
→ Chemically, hormones can be divided into two broad
classes: those that are soluble in lipids, and those that are soluble in water.
Lipid-Soluble Hormones
- Lipid-soluble include steroid hormones, thyroid hormones, nitric oxide. -
bound to transport protein (intracellular)
- Lipid-soluble hormones bind to receptors within target cells.
- Slower than water-soluble since it needs to bind.
1.Steroid hormones are derived from cholesterol. Each steroid hormone is unique due to
the presence of different chemical groups attached at various sites on the four rings at the
core of its structure. These small differences allow for a large diversity of functions.
2.Two thyroid hormones (T3 and T4) are synthesized by attaching iodine to the amino
acid tyrosine. The presence of two benzene rings within a T3 or T4 molecule makes these
molecules very lipid-soluble.
3.The gas nitric oxide (NO) is both a hormone and a neurotransmitter. Its synthesis is
catalyzed by the enzyme nitric oxide synthase.
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Document Summary
Control by the nervous system and endocrine systems. Nervous and endocrine systems work together to coordinate all systems of the body. Both hormones and neurotransmitters bind to receptors on target cells. Contains large amounts of lipids (sebaceous)(hair follicles) Secrete into the interstitial fluid surrounding the secretory cells, rather than into ducts. They are then distributed throughout the body by the bloodstream (circulating hormones) Endocrine glands include the pituitary, thyroid, parathyroid, adrenal and pineal glands. Hormones only affect target cells that possess specific protein receptors. Hormones (like neurotransmitters) influence their target cells by chemically binding to specific protein receptors. Example: thyroid-stimulating hormone (tsh) binds to receptors on cells of the thyroid gland, but it does not bind to cells of the ovaries because ovarian cells do not have tsh receptors. Receptors: are continually being synthesized and broken-down (based on demand). Receptors, like other cellular proteins, are constantly being synthesized and broken down.
