Lecture 5 Flashcards
A hormone is
A chemical messenger secreted into the blood by specialized epithelial cells
Properties of a hormone
- Cell to cell communication: chemical signals, usually very low concentration are secreted by cells and transported by the blood to distant target tissues
- Binding to target receptor initiates cellular response (response depends on receptor or signalling pathways of of the target cells)
- Communication is eventually terminated (limiting secretion, inactivating hormone, terminating target cell activity)
- Half-life: time for the hormone to reduce 1/2 in the blood
Peptide hormone (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)
- Made in advance and stored in secretory vesicles
- Exocytosis
- Dissolved in plasma
- Short
- Cell membrane
- Altered activity of proteins
Example: insulin
Steroid hormones (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)
- Made from cholesterol and it’s synthesized on demand from lipophobic precursors
- Simple diffusion
- Bound to carrier proteins
- Long
- In cytoplasm or nucleus and some can be found in cell membrane
- Induction of new protein synthesis
Example : Testosterone
_____________ is the parent amino acid for ___________ and _____________
- Tyrosine
- Catecholamines (neurohormone)
- Thyroid hormone
Catecholamines (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)
- Made in advance and stored in secretory vesicles
- Exocytosis
- Dissolved in plasma
- Short
- Cell membrane
- Modification of existing proteins
Example: epinephrine
Thyroid hormones (Synthesis & storage, release, transport in the blood, half-life, receptor location, general cellular response)
- Synthesized on demand from stored lipophobic precursors
- Transport protein
- Bound to carrier proteins
- Long
- Nucleus
- Induction of new protein synthesis
Example: thyroxine
Endocrine vs. Exocrine secretions
Endocrine glands: secretes it’s products for example hormones directly into the blood
Exocrine glands: secretes it’s products for example enzymes, into ducts that lead them to target tissues
Alpha cells secrete….
Beta cells secrete….
Glucagon
Insulin
Hormone actions are diverse: hormones may regulate cellular processes
- Rates of enzymatic reactions
- Transport of ions or molecules across the cell membrane
- Gene expression and protein synthesis
Example of an endocrine organ: Pituitary gland
The pituitary gland is two glands fused together
- The posterior pituitary gland is neural tissue and secretes 2 neurohormones: vasopressin (antidiuretic hormone) and oxytocin
- the anterior pituitary gland is endocrine tissue and it secretes 6 true hormones
- hormones released from anterior pituitary are controlled by neurohormones from the hypothalamus
Portal circulatory system
Specialized modifications where two sets of capillaries are connected in series by a set of small veins
Hypothalamic releasing hormone: thyrotropin releasing hormone (TRH) that goes into portal system that acts on specialized cells in anterior pituitary gland that will then release thyrotropin stimulating hormone (TSH)
