Module 6: Endocrinology Flashcards
What are the 3 stages of cell signalling?
- Reception (Hormone and neurotransmitter is directly involved)
- Transduction
- Response
An example of Local signalling - Paracrine signalling
A secreting cell acts on nearby target cells by secreting molecules of a local regulator (a growth factor, for example)
An example of Local signalling - Synaptic signalling.
A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell, such as a muscle or nerve cell.
An example of Long-distance signalling - Endocrine (hormonal) signalling
Specialised endocrine cells secrete hormones into body fluids, often blood. hormones reach virtually all body cells, but are bound only by some cells.
Types of Chemical Signalling
- Endocrine Signalling
- Synaptic Signalling
- Neuroendocrine Signaling
- Paracrine Signaling
- Autocrine Signaling
Endocrine Signalling is
Long-distance signalling and secretes hormones (e.g. thyroid)
Synaptic Signalling is
Local Signalling and secretes neurotransmitters
Neuroendocrine Signalling is
Long-distance signalling and secretes neurohormones (to diffuse across a synapse)
Paracrine Siganling is
Local signalling and secretes local regulators, response in neighbouring cells
Autocrine Signaling is
Local signalling and secretes local regulators, binds to the same cell, important for immune system
Autocrine Signaling is
Local signalling and secretes local regulators, bind to the same cell, important for the immune system
Regulation and Homeostasis: Animals manage their INTERNAL environment by
Regulating their internal environment despite external fluctuations,
Allowing internal condition to conform to the external environment
Regulation and Homeostasis: Organisms use homeostasis to maintain a “Steady-state” or internal balance
Independent of conditions in the external envrionment
What do endocrine hormones do in the body?
- Communication
- distribute into the bloodstream
- Messengers - tell the cells how to behave and act
Water-soluble hormones
Polypeptide - Insulin, Amine - Adrenaline
Lipid-soluble hormones
Steroids - Cortisol, Amine - Thyroxine
What is the similarity between water-soluble and Lipid-soluble hormones?
Both hormones are ductless gland (their secretions are released directly into the blood, not to any tubes or ducts)
What is the differences between Water-soluble and Lipid-soluble hormones?
A key difference is the location of the receptor proteins in target cells;
1. Water-soluble hormones secreted by exocytosis
2. Travel freely in the bloodstream
3. Cell-surface receptors such as G-protein coupled receptors or thyroxine link receptors
whereas Lipid-soluble hormones
1. are able to diffuse across the membrane
2. bind to transport proteins, which keeps them soluble in blood.
3. Does NOT need cell-surface receptors, but typically binds to receptors in the cytoplasm or nucleus
Thyroid hormones regulate:
- Homeostasis (e.g. body temperature)
- development
Adrenaline in Liver Cell
In the Liver cell, Adrenaline binds to a b-type receptor in the plasma membrane. This receptor activates the enzyme protein kinase A, which in turn regulates enzymes of glycogen metabolism, causing the release of glucose into the blood. (Signal transduction)
Adrenaline in Smooth muscle cell in wall of blood vessel that supplies the “skeletal muscle”
In the smooth muscle cells that line blood vessels supplying skeletal muscle, the same kinase activated by the same adrenaline receptor (b-type) The result is smooth muscle relaxation, leading to vasodilation and hence increased blood flow to skeletal muscles
Adrenaline in Smooth muscle cell in wall of blood vessel that supplies “intestines”
In the smooth muscle cells lining blood vessels of the intestines, adrenaline binds to an a-type receptor. Rather than activating protein kinase A, this receptor triggers a signalling pathway involving. -> Blood vessel constricts, decreasing flow to intestines
Homeostasis occurs via
negative feedback
Steps of homeostasis
- Stimulus (such as blood glucose drops, body temperature rise and Cholesterol drop etc)
- Endocrine gland - releases hormones
- Target Tissue - bind to some target tissues that are relevant to the stimulus that you had initially
- Response
Negative Feedback can
reduce stimulus
Positive Feedback can
Reinforces stimulus
Describes the steps of the hormone cascade pathway of the Negative feedback when you have a cold
- Stimulus - Cold (Body temperature rises)
- Sensory neuron and Hypothalamus is recognise the changes in body temperature; Hypothalamus secretes thyrotropin-releasing hormone (TRH) -> “Neuroendocrine signalling”
- TRH triggers anterior pituitary to secretes thyroid-stimulating hormone (TSH or thyrotropin)
- it activates the Thyroid gland to secrete thyroid hormone (T3 and T4 - both amine, lipid-soluble)
- T3 and T4 binds to target cells in the body
- Response - Increased cellular metabolism
What happens if there is enough T3 and T4?
Once our body has enough T3 and T4 in the bloodstream, some of the cells ALSO, bind to the hypothalamus and anterior pituitary to offer negative feedback to stop producing any more TRH and TSH -> restore homeostasis by the negative feedback loop
Describes the steps of the hormone cascade pathway of the Positive Feedback when a hungry baby suckling
- Stimulus - a hungry baby suckling
- Sensory neuron, hypothalamus/posterior pituitary called thyroid axis is recognised that; releases Oxytocin
- Oxytocin binds to target cells where smooth muscle in mammary glands
- Respond - Milk release