100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Summary Physiology Endocrine System Notes $5.26   Add to cart

Summary

Summary Physiology Endocrine System Notes

 13 views  0 purchase
  • Course
  • Institution
  • Book

Summary notes on the Endocrine System to adequately prepare for a first-year endocrine physiology exam.

Preview 2 out of 10  pages

  • No
  • Chapter 18
  • July 22, 2022
  • 10
  • 2021/2022
  • Summary
avatar-seller
Endocrine System
Endocrine communication occurs when the endocrine system uses chemical messengers called hormones that are
secreted into the bloodstream to relay messages and instructions to target cells all over the body. Target cells have
receptors on them that allow hormones to bind and read the hormonal message when it arrives.


Classes of hormones
Hormones can be divided into three classes based on their chemical structure
1. Amino acid derivatives - synthesised from amino acids (A) tyrosine and (B) tryptophan
a. Thyroid hormones, adrenaline and noradrenaline, dopamine (catecholamine)
b. Melatonin
2. Peptide hormones - chains of amino acids. can be divided into two groups: (A) glycoproteins and (B) short
polypeptides/proteins
a. Tsh, lh, fsh
b. Adh, oxytocin
3. Lipid derivatives - there are two groups: (A) eicosanoids and (B) steroid hormones
a. Signalling molecules and include leukotrienes, prostaglandins, thromboxanes and prostacyclins
b. Lipids structurally similar to cholesterol (androgens and corticosteroids from adrenal cortex


Transport AND INACTIVATION OF HORMONES
HORMONES ENTER THE BLOODSTREAM FOR DISTRIBUTION THROUGHOUT THE BODY. WITHIN THE BLOODSTREAM HORMONES MAY
CIRCULATE FREELY OR TRAVEL BOUND TO SPECIAL CARRIER PROTEINS. FREE HORMONES ARE INACTIVATED WHEN:
1. It diffuses out the bloodstream and binds to receptors on target cells
2. Absorbed and broken down by kidney or liver cells
3. Broken down by enzymes in blood or interstitial fluid
When free hormones are removed, bound hormones are released to replace them


Mechanism of hormone action
The binding of a hormone to its specific receptor may alter gene activity - stimulate synthesis of enzymes or
proteins by activating genes in the cell nucleus; alter the rate of protein synthesis by changing the rate of
transcription or translation; change membrane permeability. To affect a target cell a hormone must first interact

, with a specific receptor. Receptors are protein molecules to which hormones can bind to. If a cell has a receptor that
can bind a particular hormone, that cell will respond to that hormone.
● Receptors for catecholamines (A, NA, and dopamine) are extracellular receptors. Catecholamines cannot
penetrate a plasma membrane because they are not lipid soluble so the bind to the receptor proteins on the
outside of the cell to activate a second messenger system
○ cAMP, cGMP, IP3 and DAG second messenger system
● Steroid and thyroid hormones can diffuse across the lipid part of plasma membrane and bind to receptors
inside the cell in the cytoplasm or nucleus


Control of hormone secretion
Hormone secretion can be triggered by:
1. Humoral stimuli - changes in composition of extracellular fluid
2. Hormonal stimuli - changes in levels of circulating hormones
3. Neural stimuli - arrival of neurotransmitters at neuroglandular junctions
Hormones are secreted to adjust the activities of target cells and restore homeostasis. Hormone secretion or
activity is mainly controlled by negative feedback. An example is when blood glucose increases (humoral stimuli) the
pancreas will secrete insulin that will stimulate uptake of glucose and use. As the insulin level increases the glucose
level will decrease until it returns to normal and as a result insulin secretion will also return to resting levels.
This regulatory pattern is called negative feedback.


Describe the control of anterior pituitary hormone secretion
The hypothalamus regulates the functions of both the anterior and posterior pituitary gland and integrates the
activities of the nervous and endocrine system in three ways:
1. Hypothalamus acts as an endocrine organ and synthesises and releases hormones along the neurohypophysis
of the pituitary gland - adh and oxytocin
2. Secretes regulatory hormones that controls the secretory activity of the adenohypophysis
3. contains autonomic centres that exert direct neural control on the endocrine cells of adrenal medulla
The hypothalamus controls the production of hormones in the anterior lobe / adenohypophysis of the pituitary gland
by secreting specific regulatory hormones. Hypophyseal portal system ensures that when the hypothalamus releases
hormones into its bloodstream it enters portal vessels that link two capillary networks (hypothalamus and

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller tanyaswartz. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $5.26. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

83100 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
$5.26
  • (0)
  Add to cart