Endocrine System Flashcards
what is the endocrine system?
A system of glands that secrete signalling molecules
(hormones) into the bloodstream.
List the different important glands?
CNS (Brain)
- Pineal
- Hypothalamus
- Pituitary
peripheral endocrine glands
- Thyroid
- Parathyroid
- Thymus
- Adrenal gland
- Pancreas
- Ovaries/testes (reproductive glands).
Other areas include heart/kidneys/liver/intestines/skin(vitamin C)
etc.
what is a gland?
An organ which releases a substances with a specific function into the body
what are the two types of glands?
Endocrine glands secrete hormones directly into the bloodstream, while exocrine glands secrete other substances through a duct, either into the body or onto its surface.
Endocrine
* Ductless – bloodstream
* Hormones e.g. insulin, adrenaline,
cortisol
Exocrine
* Ducts – target specific area close by
* Mucus, digestive juices, sweat,
tears, milk, bile
Some organs can do both e.g. pancreas.
Direct Intracellular Communication
- refers to the communication between cells without the need for signaling molecules to diffuse through the extracellular space.
- rapid
- occurs in specific contexts where cells need to coordinate their actions orexchange information directly. - There are two primary mechanisms for direct communication:
1- Gap junctions: specialized protein channels that directly connect the cytoplasm of adjacent cells, allowing the passage of ions, metabolites, and small signaling molecules.
E.g. neurons , heart)
- Direct Link-Up of Cell Surface Markers (Cell-Cell Recognition):involves direct physical interactions between surface proteins (or cell markers) on adjacent cells have specific receptors (like cadherins, integrins, or other cell surface glycoproteins) that interact with corresponding ligands on neighboring cells. interactions often mediate recognition, adhesion, or signaling processes that are essential for immune responses, tissue development, and cell differentiation.
In this type of communication, cells have specific receptors (like cadherins, integrins, or other cell surface glycoproteins) that interact with corresponding ligands on neighboring cells.
e.g. immune system
Indirect Cellular Communication
-involves the use of signaling molecules or mediators that are secreted by one cell and travel through the extracellular space to affect a target cell.
- enables cells to transmit information over longer distances compared to direct communication.
- essential for coordinating complex processes such as growth, metabolism, immune responses, and cellular differentiation.
- 3 forms of indirect cellular
communication
1- endocrine signalling
2- Paracrine signalling:signaling molecules (e.g. hormones and neurotransmitters ) are secreted by a cell and affect nearby (but not necessarily adjacent) cells in the local environment. These molecules do not enter the bloodstream and typically have short-range effects.
-Paracrine signals diffuse LOCALLY through the extracellular space and bind to receptors on nearby target cells
- e.g. Growth factors and cytokines.
3-autocrine signalling:
- a cell produces and releases signaling molecules (often cytokines or growth factors) binds to its own receptors or those of neighboring cells of the same type.
- involves feedback loops/regulation where the cell responds to the signals it has emitted.
paracrine-targets neighbouring cells.
Autocrine- targets itself.
Most neuronal signalling is what type
Paracrine- because it involves the release of signaling molecules (neurotransmitters) from one cell (the presynaptic neuron) to act on nearby cells (the postsynaptic neuron or other target cells like muscle cells).
fits the paracrine definition beacause:
- local action: Neurotransmitters are released into the synaptic cleft, where they act on nearby target cells
short distance: The neurotransmitter doesn’t travel through the bloodstream or over long distances. It diffuses across the synapse.
Targeted response: The neurotransmitter binds to specific receptors on the target cell (like a neighboring neuron or muscle cell), triggering a response such as depolarization or muscle contraction.
Endocrine Communication
a form of indirect cellular signaling in which cells communicate over long distances using hormones e.g. insulin from pancreas.
Neuroendocrine signalling
- a specialized form of cellular communication that combines aspects of both neural and endocrine signaling. - where A neural signal (such as an action potential) reaches a neurosecretory cells (neurons)(in hypothalamus or brain) release neurohormones (e.g. oxytocin and vasopressin) into the bloodstream to affect distant target cells.
Similarities and differences between endocrine and neuroendocrine
similarities:
-Hormonal Communication
- local distance signalling
-act on Target Cells (specific receptors)
Differences:
- ES= Hormones released by endocrine glands e.g. thyroid, adrenal glands, pancreas), NS= hormone released by neurosecretory cells (neurons)
regulation :
ES= feedback loop
NS=neural input (action potentials)
Hormones involved:
ES= insulin, thyroid hormones, cortisol, etc.
NS=oxytocin, vasopressin, corticotropin-releasing hormone (CRH), etc.
Speed of action: ES= slower
NS= faster
Examples of organs:
ES=Pancreas, thyroid, adrenal glands, gonads.
NS=Hypothalamus, pituitary gland, pineal gland, adrenal medulla.
why are salivary glands, stomach and sebaceous glands NOT endocrine glands.
they done secrete into the bloodstream:
- stomach releases acid to help digest food.
- salivary glands release saliva
- sebaceous glands releases sebum
Functions of hormones?
Metabolism
Growth
Reproduction
Appetite and digestion
Mood
Circadian rhythms
What does ECF stand for?
Extracellular Fluid
what are the three types/classes of hormones?
Peptides
Amines
Steroids
types of hormones:
Transport and sites of action
Mechanisms of action
WORD
Briefly look at page 644 of Sherwood
