Endocrine System Flashcards
What are endocrine glands?
Endocrine glands produce hormones and secrete them directly into the bloodstream (without ducts) for a distant target organ
Define endocrine communication
Endocrine: this is the most common type of cell signaling and involves sending a signal throughout the whole body by secreting hormones into the bloodstream of animals or the sap in plants (Figure2). The cells that produce hormones in animals are called endocrine cells. For example, the pancreas is an endocrine gland and produces the hormone insulin, which regulates the uptake of glucose in cells all over the body. Examples of hormones that function in an endocrine manner include testosterone, progesterone and gonadotropins.
Define paracrine communication
Paracrine: signalling molecules are released from paracrine cells and diffuse locally through the extracellular fluid, targeting cells that are nearby, thus acting as local mediators. Many of the cells that are involved in inflammation during infection, or that regulate cell proliferation utilise this type of signalling. For example cancer cells sometimes enhance their own survival or proliferation in this way. Examples of signalling molecules that often function in a paracrine manner include transforming growth factor-β (TGF-β) and fibroblast growth factors (FGFs).
Define autocrine signalling
Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on that same cell, leading to changes in the cell.
Define neurocrine signalling
A type of cell signaling involving the release of a hormone from a nerve cell that has an effect on another cell.
E.g. hypothalamus, posterior pituitary, adrenal medulla
Name the major endocrine glands/organs
Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid gland Thymus Adrenal glands Pancreas Gonads
What is the thymus? Explain its role
• It is located in the superior mediastinum, is fully formed and functional at birth, it involutes after puberty and by the late teens is mostly fat
• Its role is the maturation of bone marrow derived stem cells into
immunocompetent T cells. This is called thymic cell education. It
produces thymosin, a hormone that promotes T cell maturation
How many types of hormone are there?
At least 50
What do hormones control and regulate?
- Reproduction
- Metabolism and energy balance
- Growth and development
- Body defences
- General homeostasis and water, nutrient, and electrolyte balance of the blood
Name 4 types of hormones?
Peptide hormones
Steroid hormones
Catecholamines (tyrosine derived)
Thyroid hormones (tyrosine derived)
How are peptide hormones synthesised and stored?
Made in advance; stored in secretory vesicles
How are steroid hormones synthesised and stored?
Synthesised on demand from precursors
How are catecholamines synthesised and stored?
Made in advance; stored in secretory vesicles
How are thyroid hormones synthesised and stored?
Made in advance; precursor stored in secretory vesicles
How are peptide hormones transported in blood?
Dissolved in plasma
How are steroid hormones transported in blood?
Bound to carrier proteins
How are catecholamines transported in blood?
Dissolved in plasma
How are thyroid hormones transported in blood?
Bound to carrier proteins
Where are the receptors for peptide hormones?
Cell membrane
Where are the receptors for steroid hormones?
Cytoplasm or nucleus; some have membrane bound receptors
Where are the receptors for catecholamines?
Cell membrane
Where are the receptors for thyroid hormones?
Nucleus
What is the response when peptide hormones bind to receptors?
Activation of second messenger systems; may activate genes
What is the response when steroid hormones bind to receptors?
Activation of genes for transcription and translation; may have nongenomic actions
