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=3
Perpiheral Endocrine Glands=6
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 and what is the difference between them?
examples?
which organ is BOTH types?
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
Speed?
what is it?
what are the two mechanisms involved + EXAMPLES.
- very fast
- the cell links up (communicates) with another cell through direct physical contract.
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 and small signalling molecules= very quick communication E.g. neurons , heart.
- Direct Link-Up of Cell Surface Markers (Cell-Cell Recognition): This involves direct contact between cell surface molecules, allowing cells to recognize and respond to each other. This is important in immune responses and tissue formation e.g. immune system
Indirect Cellular Communication
what is it?
where does the released signal molecules travel to?
how far?
what are the thee forms?
1-
2- what does it target? where is the signal released? how far do the paracrine signals diffuse?
example ?
3- what does it target how does it work? what does it involve?
summary !
cells communicate with each other without direct physical contact.
release of signalling molecules that travel to local target cells.
enables cells to transmit information over longer distances compared to direct communication.
3 forms/mechanism of indirect cellular
communication
1- endocrine signalling
2- Paracrine signalling:
- targets neighbouring cells
- signal is released into extracellular fluid.
-Paracrine signals diffuses a short distance through the extracellular space and bind to receptors on local target cells
- e.g. Hormones or neurotransmitters.
3-autocrine signalling:
- targets itself.
- a cell produces and releases signaling molecules binds to its OWN receptors or those of neighbouring cells of the same type.
- involves negative feedback loops/regulation = 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 local target cells like muscle cells).
- short distance: The neurotransmitter doesn’t travel through the bloodstream or over long distances. It diffuses across the synapse.
Endocrine Communication
what type of signalling?
how do the cells communiacte?
a form of indirect cellular signaling
cells communicate over long distances using hormones e.g. insulin from pancreas.
Neuroendocrine signalling
what is it?
How does it work?
what does if affect?
Example ?
- communication that combines aspects of both neural and endocrine signalling.
- 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.
- e.g. Oxytocin from the pituitary
Similarities and differences between endocrine and neuroendocrine.
Differences?
what is the hormone released by?
Regulation?
which hormones are involved?
speed of action?
Examples of Organs involved?
similarities:
-Hormonal Communication
- local distance signalling
-act on Target Cells (specific receptors)
Differences:
- ES= Hormones released by endocrine glands
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 (6)?
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
PCOS
Hyperparathyroidism
Achondroplasia
polycystic Ovarian Syndrome- dysregulation of reproductive hormones.
affects thyroid glands (control calcium and phosphate balance)
Dwarfism- short stature and short limbs= abnormal cartilage formation in growth plates
what are the common drugs that target endocrine systems (5).
- insulin
- Contraception / HRT / fertility
- Levothyroxine
- Steroids (immunosuppressants)
- Epipens
What is neurotransmitter concentration controlled by?
storing in vesicles and releasing in very specific areas.
what is hormone concentration controlled through?
through feedback loops—both positive and negative—which help maintain homeostasis by adjusting hormone levels in response to changes in the body.
Positive feedback amplifies a response, pushing the system further from its equilibrium (e.g., oxytocin during childbirth).
Negative feedback reduces or counteracts a response, maintaining balance (e.g., insulin regulation of blood sugar).
Hormone Signalling Complexity
How many hormones can one gland secrete. what are the glands that can do this?
Can ONE hormone be secreted by multiple glands?
How many target cells can ONE hormone have?
Can ONE target cell be targeted by more than one hormone?
Is the rate of secretion the same for all glands?
Can a molecule have more than one function?
which endocrine organ has function other than hormone secretion?
- One gland may secrete multiple hormones e.g. pituitary, thyroid. adrenal, pancreas, ovaries/testes.
- One hormone may be secreted by multiple glands e.g. epinephrine (adrenaline).
- One hormone may have multiple target cells (different effects) e.g. adrenaline consists of multiple receptors.
- One target cell may be targeted by multiple hormones
- Rate of secretion can vary
- Same molecule can act as a hormone or a neurotransmitter e.g. norepinephrine (adrneline).
- Some endocrine organs have functions other than hormone secretion. pancreas also produces digestive enzymes.
what is the strenth of a hormone proportional to?
what is the plasma concentration (amount of hormone in the blood plasma) dependent on?
the strength of a hormones effect on target cells is proportional to its concentration in the blood.
High Conc = Stronger effect and Low Conc = weaker effect.
Plasma concentration is dependent on:
- Rate of secretion (feedback loops)- how fast it is relased into the blood.
- Metabolic activation or conversion into its active form.
- Extent of binding to plasma proteins (Lipophilic)
- Inactivation or excretion- how fast it is broken down or removed from the body.
what is the Pituitary an example of?
How many different hormones can it secrete?
what is it controlled by?
- a gland may secrete
multiple hormones - 9
- the hypothalamus
hypothalamic-hypophyseal portal.
what is the special capillary network between hypothalamus and anterior pituitary called.
Anterior Pituitary (AP)
What does the hypothalamus synthesise?
How are these hormones sent to the AP?
what do they do once they reach the AP?
Hypothalamus makes hormones that control the secretion of hormones from the anterior pituitary:
- Releasing Hormones= stimulate the anterior pituitary to release specific hormones.
-Inhibiting Hormones= suppress the release of certain hormones from the anterior pituitary.
The hypothalamus sends these hormones to the anterior pituitary via the hypothalamic-hypophyseal portal.
These then stimulate the AP to release the hormones into the blood stream and act on the rest of the body.
