L6 The Endocrine System Flashcards
What is the definition of a hormone?
Signalling molecules/mediators secreted from endocrine cells into the bloodstream
What are the 7 classic endocrine glands?
- Pituitary (anterior and posterior)
- Thyroid
- Parathyroids
- Adrenals (cortex and medulla)
- Ovaries
- Testes
- Pancreas
Can you name 6 endocrine tissues?
- Hypothalamus
- Kidneys
- GI tract
- Heart
- Liver
- Adipose tissue
Name the three main chemical classes of hormones.
- Peptide
- Amino acid derived
- Steroids
How do peptide hormones differ in synthesis from steroid hormones?
Peptide hormones are synthesized from amino acids, while steroid hormones are metabolites of cholesterol.
How do steroid hormones differ in which receptors it would bind to?
Steriod hormones would diffuse into cells and then bind to the intracellular/ nuclear receptors whereas the other two types of hormones would bind to the cell membrane on the surface receptors
What are the response times in the 3 different classes of hormones?
Peptide - Seconds to minutes
Amino acid derived - Seconds to minutes
Steriods - Hours to days
What is the release mechanism for steroid hormones?
Lipid soluble, they diffuse into cells and bind to intracellular/nuclear receptors.
What is a key characteristic of endocrine glands?
They do not have ducts.
Fill in the blank: Endocrine signaling enables cell signaling across _______ distances.
long
True or False: Endocrine signaling is fast.
False
What regulates the release of parathyroid hormone (PTH)?
Plasma calcium levels sensed by Chief cells
What does the parathyroid gland do?
They are responsible for regulating calcium levels in the blood. They produce PTH which helps maintain Ca2+ levels
How does the parathryoid gland lower calcium levels?
- Increased calcium conc sensed by chief cells
- PTH release ⬇️
- Kidney tubule reabsorption ⬇️
- Bone calcium resorption ⬇️
- Intestinal calcium absorption ⬇️
- Resulting in lowering plasma calcium conc
Describe the role of the hypothalamus in endocrine control.
Regulates the anterior pituitary (adenohypophysis) through releasing hormones and the posterior pituitary (neurohypophysis).
What hormones do the adrenal cortex release?
- Glucocorticoids (e.g., cortisol)
- Mineralocorticoids (e.g., aldosterone)
The adrenal gland is seperated into two parts. What are they?
Adrenal cortex
Adrenal Medulla
What is the primary function of insulin?
Decrease blood glucose levels by increasing glucose storage in muscle and decreasing glucose synthesis in the liver.
What type of feedback loop regulates parathyroid hormone (PTH)?
Simple negative feedback loop
Fill in the blank: The anterior lobe of the pituitary is also known as the _______.
adenohypophysis
What is the function of the Leydig cells in the testes?
Produce the steroid hormone testosterone, stimulating protein synthesis and development.
What do the adrenal medulla chromaffin cells release?
Catecholamines, including adrenaline and noradrenaline.
How does the thyroid gland regulate metabolism?
Through T3 and T4 hormones, which bind to nuclear receptors to regulate transcription.
What two things does the thyroid gland regulate?
Metabolism - basal metabolic rate
Development and growth
True or False: Hormones can interact with specific tissues/organs.
False
They are specific to receptors but not specific to tissues/organs
What is the role of the islets of Langerhans in the pancreas?
Release insulin from β cells and glucagon from α cells into portal blood.
Which hormone is produced by the ovaries?
Oestrogen and Progesterone
What influences the synthesis and release of thyroid hormones?
Hypothalamic-pituitary hormones and iodine
What is the mechanism of action for peptide and amino acid-derived hormones?
Bind to cell membrane surface receptors.
Define endocrine gland
A ductless organ that produces hormones and releases them directly into the bloodstream
Define endocrine cells
A specialised tissue that produces hormones and releases them into the bloodstream
Where are endocrine cells generally located?
- Close proximity to capillary beds
- Found in endocrine tissues or glands
What is the adenohypophysis?
The front lobe (anterior lobe) of the pituitary gland
Develops from an upward projection of the pharynx
What is the neurohypophysis?
Also known aas the posterior pituitary, it is the back lobe of the pituitary gland
Develops from a downward projection of the brain
How does the hypothalamus control the function of the anterior pituitary gland?
The adenohypophysis is controlled by the hypothalamus through the release of hormones (into the hypophyseal portal system). These hormones, produced by the hypothalamic neurons, stimulate or inhibit the activity of the troph cells, thereby regulating their hormone secretion
How does the hypothalamus control the function of the posterior lobe (neurohypophysis) of the pituitary gland?
It releases hormones from** large diameter neurons** directly into the systemic cirulcation
What two ways can hormonal release can be regulated by?
-Simple negative feedback loops e.g PTH
- Hierarchical control: cortical control, inhibition of releasing hormone release, inhibition of tropic hormones release
Give me examples of simple negative feedback loops in hormone release
- Blood glucose regulation (insulin and glucagon)
- Thyroid hormone regulation (T3 and T4)
- Calcium regulation (PTH)
