Endocrine System Prerecording 1 Flashcards
What is the thyroid?
Endocrine organ
Overall, the endocrine system is a ______ system
Regulatory
Label the endocrine tissues and organs
The endocrine system is a collection of _____ and _____ that secrete _____ ____ (______) into the blood, directly or via interstitual fluid or lymph
The endocrine system is a collection of glands and tissues that secrete chemical messengers (hormones) into the blood, directly or via interstitual fluid or lymph
What is a gland?
Glandular epithelium = consists of specialized cells that synthesize, store and secrete chemical substances
What are the two types of glands?
- Exocrine
- Endocrine
What is the difference between Exocrine glands and endocrine glands?
Exocrine: release their secretions into ducts that carry the secretions to an epithelial surface (eg sweat, mammary, salivary)
Endocrine: Release their secretions into blood (directly or via interstitial fluid)
Hormones are produced by which type of gland?
Endocrine
What is a hormone?
(include where hormones are produced, how they “get around” and why they don’t elicit responses from every cell they encounter)
A chemical messenger that:
- is produced and secreted by an endocrine cell
- travels through the circulatory system to reach other tissues
- acts upon specific target cells within the tissue (via receptors)
Paracrine signalling:
Autocrine signalling:
These are not hormones by our definition
Paracrine signalling: cells secrete messengers to communicate with neighbouring cells
Autocrine signalling: cell secretes messengers to act on self
These are not hormones by our definition
How is the endocrine system targeted/specific with its hormones?
Cells have receptors that are selective to specific hormones.Only matching hormones can bind to that receptor
=only cells with that receptor will respond
how can you have graded responses with hormones?
By the number of receptors a cell has
Compare the nervous system to the endocrine system:
- Signals are sent by:
- Signals are:
- Duration
- Specificty
Compare the nervous system to the endocrine system:
- Signals are sent by: neurons (NS) or endocrine glandular cells (endocrine)
- Signals are: electrical impulses conducted along axons + transmitters or hormones secreted in bloodstream
- Specificity: highly specific; widespread activity
- Duration: short term; long duration (takes time to get a response and also come down from that response)
What are some examples of overlap between the endocrine and NS? (4)
- Brain regulates secretions from endocrine glands; hormones impact CNS function
- Both secrete chemical messengers that act on target cells
- In some cases, the same molecule can act as NT and hormone (Adrenaline and vasopressin)
- Some neurons (neurosecretory cells or neuroendocrine cells) release Hormones (into blood)
What are the four types of hormones?
- Amino acid (eg adrenaline)
- Peptide (oxytocin)
- Steroid (estrogen)
- Eicosanoid (prostaglandins)
What do thyroid hormones do?
- Raise metabolic rate
- elevate cellular oxygen use
- Important for growth and development (formation of organs)
The thyroid gland is _____ to the trachea, just ____ to the larynx. It is anchored to the ______ ______ ______
The thyroid gland is anterior to the trachea, just inferior to the larynx
TIt is anchored to the first 2-3 tracheal rings
Why do glands have a large blood supply?
To enable it to get its secretions into the bloodstream
Describe the anatomical location of the Thyroid Gland
The thyroid is anchored to the first 2-3 tracheal rings, anterior to the trachea, just inferior to the larynx
What is being shown in the image?
A thyroid follicle is composed of an outside ring of epithelial cells called ________(or ________), and an inside globular mass of viscous ______-rich fluid called ______.
A thyroid follicle is composed of an outside ring of cells called follicular cells (or T Thyrocytes), and an inside globular mass of viscous, protein-rich fluid called colloid.
The thyroid gland sits right in front of the ______, just below the ______. The thyroid gland sits below the thyroid _______, the tip of which makes the ______ ______
The thyroid gland sits right in front of the trachea, just below the larynx. The thyroid gland sits below the thyroid cartilage. The tip of which makes the adam’s apple
The protein in the Colloid is the stored precursor hormone called:
Thyroglobulin
T thyrocytes produce a large protein, _____ and store it in the lumen of the follicle.
The cells pump ______ into the lumen. _____ on their luminal surface will add this to the Tg
T thyrocytes produce a large protein, Thyroglobulin and store it in the lumen of the follicle.
The cells pump Iodine into the lumen. Enzymes on their luminal surface will add this iodine to the Tg
What induces thyrocytes to remove Tg from the lumen, cleave off T3 and T4 (the thyroid hormones) and release them into the blood?
Thyroid Stimulating Hormone (TSH)
Describe the events that lead to the release of thyroid hormones into the blood.
Try not to look at the fill in the blank, but use it to recall if necessary:
The thyrocytes receive an activation hormone _______. This causes the cells to take up (endocytose) the ____ from within the lumen and break off small pieces (via ______ filled with enzymes) (these small pieces are the thyroid hormones, ____ and _____)
The thyrocytes receive an activation hormone Thyroid Stimulating Hormone (TSH). This causes the cells to take up (endocytose) the Tg (thyroglobulin) from within the lumen and break off small pieces (via lysosomes filled with enzymes). These “small pieces” are the thyroid hormones, T3 and T4 which are then released into the blood
Thyroid hormones are derivatives of the amino acid _____ with the addition of ______
Thyroid hormones are derivatives of the amino acid tyrosine with the addition of iodine
Why are the thyroid hormones called T3 and T4
T3 has 3 iodine
T4 has 4 iodine
The thyroid gland releases mainly ______, but _____ is the more active form.
______ _____ can convert T4 to T3. Both regulate ______
The thyroid gland releases mainly thyroxine (T4), but triiodothyronine (T3) is the more active form.
Peripheral Tissues can convert T4 to T3. Both regulate metabolism
What two structures act as the master regulators of the endocrine system?
Hypothalamus and Pituitary Gland
Describe the regulation of the thyroid from the hypothalamus and pituitary gland.
The hypothalamus releases TRH (thyrotropin-releasing hormone) which acts on the pituitary and stimulates it to release TSH (thyroid-stimulating hormone) which activates the thyroid and induces the release of the thyroid hormones (T3 and T4) (and production of more thyroglobulin).
Downregulation:
The pituitary and hypothalamus sense higher levels of T4 and T3 and reduce the amount of TRH and TSH
