BISC 101 Lecture Notes - Lecture 18: Posterior Pituitary, Anterior Pituitary, Thyroid

74 views8 pages
BISC 101 – Lecture 18 – Hormones and the Endocrine System
Intercellular Communication
1. Endocrine Signaling: Secreted molecules diffuse into the bloodstream and
trigger responses in target cells anywhere in the body
2. Paracrine Signaling: Secreted molecules diffuse locally and trigger a response in
neighboring cell
3. Autocrine Signaling: Secreted molecules diffuse locally and trigger a response in
the cells that secrete them
4. Synaptic Signaling: Neurotransmitters diffuse across synapses and trigger
responses in cells of target tissues
5. Neuroendocrine Signaling: Neurohormones diffuse into the bloodstream and
trigger responses in target cells anywhere in the body
Hormones
Animal Hormones: Chemical signals secreted into the circulatory system and
communicate regulatory messages within the body
Glandular Cells: Secrete hormone into the bloodstream
Target Cells: Cells with hormone receptors that respond to the hormone
Hormones reach all parts of the body but only target cells are equipped to respond
Mediate responses to environmental stimuli and regulate growth, development, and
reproduction
Endocrine Glands: Ductless glands that secrete hormones directly into surrounding
fluid
oSecretes into the extracellular fluid and then diffuse into the bloodstream
Exocrine Glands: Glands with ducts that secrete substances onto body surfaces or
into body cavities
oBody cavities include tear glands, sweat glands, and salivary glands
Basic categories of hormones are based on:
oAmino acids
Modified amino acids or amines
Peptides or short chains of amino acids and Proteins or long chains
of amino acids
Glycoproteins
oSteroids
Lipid molecules derived from cholesterol
Cellular Response Pathways
Water and lipid soluble hormones differ in their paths through a body
Water Soluble Hormones
oSecreted by exocytosis
oTravel freely in the blood stream
oBind to cell – surface receptors
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
oThe binding of water – soluble hormones to cell surface receptors alerts a
second messenger molecule inside the cell that activates enzymes and
other cellular proteins or influences gene expression
oResponses to water – soluble hormones are indirect
Epinephrine has many effects in mediating the body’s response to short
– term stress
Epinephrine binds to receptors on the plasma membrane of liver cells
This triggers the release of secondary messenger molecules that
activate enzymes and result in the release of glucose into the
bloodstream
oNorepinephrine or noradrenaline, ADH, OT, TRH, PTH, GH, ACTH, insulin,
glucagon
Lipid Soluble Hormones
oDiffuse across cell membranes
oTravel in the bloodstream bound to transport proteins
oDiffuse through the membrane of target cells to bind to intracellular
receptors
oThe response to a lipid soluble hormone is direct upon binding to its
receptors
oTherefore, no secondary messengers are available
Ex: Steroids and thyroid hormones, and the hormonal form of vitamin D
enter target cells and bind to protein receptors in the cytoplasm or
nucleus
oProtein – receptor complexes then act as transcription factors in the
nucleus by regulating transcription of specific genes
oEx: T3 and T4, testosterone, progesterone, estrogen, cortisol,
aldosterone
Hormone Pathways
1. Hormones are released from an endocrine cell
2. Hormones travel through the blood stream
3. Hormones interact with the receptor or a target cell to cause a physiological
response
Negative Feedback Loop: Inhibits a response by reducing the initial stimulus
Negative feedback regulates man hormonal pathways involved in homeostasis
Insulin and Glucagon
Insulin and glucagon control the levels of blood glucose
Insulin and glucagon are antagonistic hormones that help maintain glucose
homeostasis
Insulin reduces blood glucose
oPromotes the cellular uptake of glucose
oSlowing glycogen breakdown in the liver
oPromoting fat storage
Glucagon increases blood glucose
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
oStimulates conversion of glucogen to glucose in the liver
oStimulates breakdown of fat and protein into glucose
Islets of Langernans: Clusters of endocrine cells found in the pancreas
Alpha Cells: Cells in the pancreas that produce glucagon
Beta Cells: Cells in the pancreas that produce insulin
Diabetes Mellitus
Diabetes Mellitus: Endocrine disorder where glucose levels are very high
Caused by a deficiency of insulin or a decreased response to insulin in target
tissues
Type 1 Diabetes Mellitus: Autoimmune disorder in which the immune system
destroys pancreatic beta cells, eventually eliminating insulin production
oInsulin dependent
o5 – 10% of those diagnosed with diabetes mellitus have this type
oPeople must take insulin through injections or through an insulin pump
Type 2 Diabetes Mellitus: Insulin deficiency or reduced response of target cells due
to change in insulin receptors
o90 to 95% of those diagnosed with diabetes mellitus have this type
oCan be prevented or delayed with a healthy lifestyle
oType 1 cannot be prevented
Coordination of Endocrine and Nervous Systems in Vertebrates
Hypothalamus: Receives information from the nervous system and initiates
responses through the endocrine system
Pituitary Gland: Attached to the hypothalamus and is composed of the posterior
and anterior pituitary
Posterior Pituitary: Stores and secretes hormones that are made in the
hypothalamus
oNeurohypophysis
Neurohormones are produced by neurosecretory cells of the
hypothalamus which spans directly to the posterior pituitary
Neurohormones are transported through the axon of
neurosecretory cells
Neurohormones are stored in the axon terminals that lie in the
posterior pituitary
Posterior pituitary produces no hormones but stores them for the
hypothalamus
When the neurosecretory cells are stimulated, the action potential
generated triggers the release of neurohormones into capillary
network of the posterior pituitary
oOxytocin: Peptide neurohormone which induces uterine contractions and
the release of breast milk from lactating mammary glands
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class