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Health Sciences > L34, 35, 36 ENDOCRINOLOGY > Flashcards

L34, 35, 36 ENDOCRINOLOGY Flashcards

1
Q

L34: Endocrine system

What is the function of the endocrine system?

A

It regulates homeostasis by secreting hormones that influence metabolism, growth, and organ function

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2
Q

L34: Endocrine system

How do endocrine glands differ from exocrine glands?

A

Endocrine glands are ductless and release hormones directly into the bloodstream, while exocrine glands use ducts to transport secretions.

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3
Q

L34: Endocrine system

Where is the hypothalamus located?

A

At the base of the brain, just above the pituitary gland.

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4
Q

L34: Endocrine system

What are the main functions of the hypothalamus?

A

It regulates body temperature, thirst, hunger, sleep, blood pressure, and hormone secretion.

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5
Q

L34: Endocrine system

Where is the pituitary gland located?

A

It sits in the sella turcica (a cavity in the sphenoid bone) and is connected to the hypothalamus by the infundibular stalk.

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6
Q

L34: Endocrine system

What are the two parts of the pituitary gland?

A

Anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis).

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7
Q

L34: Endocrine system

What is the embryological origin of the anterior pituitary?

A

It develops from pharyngeal tissue.

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8
Q

L34: Endocrine system

Name six hormones secreted by the anterior pituitary.

A
  1. ACTH (Adrenocorticotropic hormone) – Stimulates the adrenal cortex.
  2. TSH (Thyroid-stimulating hormone) – Stimulates the thyroid.
  3. LH (Luteinising hormone) – Regulates ovulation and testosterone production.
  4. FSH (Follicle-stimulating hormone) – Stimulates egg and sperm production.
  5. PRL (Prolactin) – Stimulates milk production.
  6. GH (Growth hormone) – Stimulates cell growth and metabolism.
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9
Q

L34: Endocrine system

What is the embryological origin of the posterior pituitary?

A

It develops from neural tissue.

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10
Q

L34: Endocrine system

What hormones are stored and released by the posterior pituitary?

A

Oxytocin – Stimulates uterine contractions and milk ejection.

Antidiuretic hormone (ADH) – Regulates water retention in the kidneys.

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11
Q

L34: Endocrine system

How are these hormones transported to the posterior pituitary?

A

Via the hypothalamohypophyseal tract (nerve axons).

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12
Q

L34: Endocrine system

What system connects the hypothalamus to the anterior pituitary?

A

The hypothalamohypophyseal portal system.

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13
Q

L34: Endocrine system

How does negative feedback work in hormone regulation?

A

High hormone levels signal the hypothalamus to reduce hormone production, preventing excess secretion.

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14
Q

L34: Endocrine system

Where is the thyroid gland located?

A

In the anterior neck, in front of the trachea, spanning C5 to T1.

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15
Q

L34: Endocrine system

What are the two main thyroid hormones and their functions?

A
  1. Thyroxine (T4) – Regulates metabolism.
  2. Triiodothyronine (T3) – Active form, increases basal metabolic rate.
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16
Q

L34: Endocrine system

What hormone lowers blood calcium levels, and how?

A

Calcitonin – It promotes calcium storage in bones.

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17
Q

L34: Endocrine system

How many parathyroid glands are there, and where are they located?

A

Four glands (two superior, two inferior) on the posterior surface of the thyroid.

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18
Q

L34: Endocrine system

What hormone does the parathyroid gland secrete, and what is its function?

A

Parathyroid hormone (PTH) – Increases blood calcium levels by stimulating bone resorption and enhancing kidney and intestinal calcium absorption.

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19
Q

L34: Endocrine system

Where are the adrenal glands located?

A

On the superior-medial aspect of the kidneys, at T11/T12 level.

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20
Q

L34: Endocrine system

Name the three layers of the adrenal cortex and the hormones they produce.

A
  1. Zona glomerulosa → Aldosterone (regulates water & salt balance).
  2. Zona fasciculata → Cortisol (regulates glucose metabolism, reduces inflammation).
  3. Zona reticularis → Androgens (precursors for sex hormones).
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21
Q

L34: Endocrine system

What does the adrenal medulla produce, and what is its function?

A

Adrenaline & noradrenaline → Initiate the sympathetic (fight-or-flight) response.

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22
Q

L34: Endocrine system

What are the two functions of the pancreas?

A
  1. Exocrine function → Secretes digestive enzymes into the duodenum.
  2. Endocrine function → Releases hormones into the bloodstream.
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23
Q

L34: Endocrine system

What are the four cell types in the Islets of Langerhans and their hormones?

A
  1. Alpha cells → Glucagon (raises blood glucose).
  2. Beta cells → Insulin (lowers blood glucose).
  3. Delta cells → Somatostatin (inhibits insulin & glucagon).
  4. PP cells → Pancreatic polypeptide (regulates pancreatic enzyme secretion).
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24
Q

L34: Endocrine system

Where are the ovaries and testes located?

A

Ovaries → Pelvic cavity.

Testes → Scrotum (outside the body cavity).

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25
# L34: Endocrine system What hormones do the ovaries and testes secrete?
Ovaries → Oestrogen & progesterone (regulate the menstrual cycle & pregnancy). Testes → Testosterone (develops male secondary sexual characteristics).
26
# L34: Endocrine system How does the hypothalamus communicate with the anterior and posterior pituitary?
Anterior pituitary → Hypothalamohypophyseal portal system. Posterior pituitary → Hypothalamohypophyseal tract (nerve axons).
27
# L34: Endocrine system What are hormones?
Chemical messengers secreted by endocrine glands that regulate bodily functions.
28
# L34: Endocrine system What is the difference between endocrine and nervous system signalling?
Endocrine system → Uses hormones, slower but longer-lasting effects. Nervous system → Uses electrical impulses, faster but short-lived responses.
29
# L34: Endocrine system What are the three major types of hormones?
1. Peptide hormones – Made of amino acids (e.g., insulin, ADH). 2. Steroid hormones – Derived from cholesterol (e.g., cortisol, oestrogen). 3. Amino acid-derived hormones – Modified amino acids (e.g., adrenaline, thyroxine).
30
# L34: Endocrine system How do hormones travel in the body?
Through the bloodstream, binding to target cells via specific receptors.
31
# L34: Endocrine system What are releasing hormones from the hypothalamus?
Hormones that stimulate the anterior pituitary to release specific hormones, e.g.: TRH (Thyrotropin-releasing hormone) → Stimulates TSH release. CRH (Corticotropin-releasing hormone) → Stimulates ACTH release. GnRH (Gonadotropin-releasing hormone) → Stimulates FSH & LH release.
32
# L34: Endocrine system What are inhibiting hormones from the hypothalamus?
Hormones that prevent the anterior pituitary from releasing specific hormones, e.g.: Somatostatin → Inhibits GH & TSH release. Dopamine (Prolactin-inhibiting hormone, PIH) → Inhibits prolactin release.
33
# L34: Endocrine system How is the anterior pituitary different from the posterior pituitary?
Anterior pituitary → Produces its own hormones, regulated by the hypothalamus. Posterior pituitary → Stores & releases hypothalamic hormones (ADH & oxytocin).
34
# L34: Endocrine system What is the function of Melanocyte-Stimulating Hormone (MSH)?
Controls melanin production in the skin and may influence appetite & sexual function.
35
# L34: Endocrine system What mineral is required for thyroid hormone production?
Iodine – Found in iodised salt and seafood.
36
# L34: Endocrine system What condition results from iodine deficiency?
Goitre – An enlarged thyroid due to insufficient T3 & T4 production.
37
# L34: Endocrine system What is the difference between hyperthyroidism and hypothyroidism?
Hyperthyroidism → Excess thyroid hormones → Weight loss, rapid heartbeat, heat intolerance. Hypothyroidism → Insufficient thyroid hormones → Weight gain, fatigue, cold intolerance.
38
# L34: Endocrine system What is the antagonist hormone to calcitonin?
Parathyroid Hormone (PTH) – Raises blood calcium by increasing bone breakdown.
39
# L34: Endocrine system What are the three zones of the adrenal cortex and their primary hormones?
1. Zona Glomerulosa → Aldosterone (Water & sodium retention). 2. Zona Fasciculata → Cortisol (Glucose metabolism, stress response). 3. Zona Reticularis → Androgens (Sex hormone precursors).
40
# L34: Endocrine system What is Cushing’s syndrome?
Excess cortisol production → Causes weight gain, moon face, muscle weakness, high blood sugar.
41
# L34: Endocrine system What is Addison’s disease?
Adrenal insufficiency → Causes low cortisol & aldosterone levels, fatigue, low blood pressure.
42
# L34: Endocrine system How does aldosterone regulate blood pressure?
It increases sodium retention, which increases water retention, raising blood pressure.
43
# L34: Endocrine system What is the role of prolactin?
It stimulates milk production in breastfeeding women.
44
# L34: Endocrine system Which hormone is responsible for contractions during childbirth?
Oxytocin
45
# L35: Hormone Action What are the three superfamilies of hormones?
Peptide hormones, steroid hormones, and amino acid derivatives.
46
# L35: Hormone Action Give an example of each hormone superfamily.
Peptide hormone: Insulin Steroid hormone: Cortisol Amino acid derivative: Epinephrine/Adrenaline
47
# L35: Hormone Action What are the key properties of hormone receptors?
- High specificity and affinity - Present in specific tissues - Limited binding sites (saturable) - Reversible binding - Must mediate a biological response
48
# L35: Hormone Action What are the two types of hormone receptors?
Cell surface receptors (for hydrophilic hormones) Intracellular receptors (for hydrophobic hormones)
49
# L35: Hormone Action What are the two main types of cell surface receptors?
Tyrosine Kinase Receptors G-Protein Coupled Receptors (GPCRs)
50
# L35: Hormone Action How do Tyrosine Kinase Receptors function?
Transfer phosphate from ATP to tyrosine residues Activation leads to phosphorylation and a conformational change
51
# L35: Hormone Action What are the two types of Tyrosine Kinase Receptor activation?
Intrinsic (e.g., Insulin Receptor) Recruited (e.g., Growth Hormone Receptor)
52
# L35: Hormone Action What are the three main signalling pathways of Epidermal Growth Factor Receptor (EGFR)?
Ras pathway Phosphatidylinositide 3-kinase (PI 3-kinase) JAK-STAT pathway
53
# L35: Hormone Action How is Ras activated in signal transduction?
GDP-bound Ras is inactive Ligand binding activates Ras via GRB and SOS proteins GDP is exchanged for GTP, leading to downstream effects
54
# L35: Hormone Action What do GPCRs mediate?
Second messenger activation
55
# L35: Hormone Action What are three common second messengers in GPCR signalling?
Cyclic AMP (cAMP) Inositol 1,4,5-triphosphate (IP₃) Diacylglycerol (DAG)
56
# L35: Hormone Action What is the structure of a G-protein?
Composed of α, β, and γ subunits (α subunit is key for signalling)
57
# L35: Hormone Action Describe the GPCR signalling mechanism.
Hormone binds to receptor Conformational change occurs GDP on α-subunit is replaced with GTP α-subunit dissociates and activates downstream messengers Cellular response occurs
58
# L35: Hormone Action What is the role of DAG and Ca²⁺ in GPCR signalling?
DAG activates Protein Kinase C (PKC) IP₃ releases Ca²⁺, which activates calmodulin and kinases
59
# L35: Hormone Action How do peptide hormone receptors function?
They use second messengers like cAMP and IP₃ to change cell function.
60
# L35: Hormone Action How do steroid hormones differ from peptide hormones in their mechanism?
Peptide hormones use cell surface receptors and second messengers Steroid hormones use intracellular receptors to directly regulate gene transcription
61
# L35: Hormone Action How are steroid hormones transported in the blood?
Bound to plasma protein carriers; only unbound steroids diffuse into target cells.
62
# L35: Hormone Action What are the two types of steroid receptors?
Cytoplasmic receptors – activated steroids translocate to the nucleus Nuclear receptors – already in the nucleus and activated upon ligand binding
63
# L35: Hormone Action Describe the process of steroid receptor activation.
1. Steroid hormone diffuses into the cell 2. Receptor-hormone complex forms 3. Complex binds to DNA 4. Gene transcription is altered 5. mRNA is translated into proteins
64
# L35: Hormone Action What is the difference between Type I and Type II nuclear receptors?
Type I (homodimers): In cytoplasm, translocates to DNA upon activation (e.g., glucocorticoid receptor) Type II (heterodimers): Always bound to DNA, activated by ligand binding (e.g., Vitamin D receptor)
65
What are the five regions of nuclear receptor structure?
A/B Region – Transcriptional activation C Region – DNA-binding domain (zinc fingers) D Region – Hinge region (allows conformational change) E Region – Ligand-binding domain F Region – Variable domain
66
# L35: Hormone Action What are the three types of Hormone Response Elements (HREs)?
Palindromic HREs (AGAACA ------- TGTTCT) Direct Repeat HREs (AGGTCA ------- AGGTCA) Inverted Palindrome HREs (AGAACA ------- TCTTGT)
67
# L35: Hormone Action What enables nuclear receptors to bind DNA?
Zinc finger domains
68
# L35: Hormone Action What is the role of the P-box in nuclear receptors?
Binds to DNA to enable transcription.
69
# L35: Hormone Action Final summary of hormone mechanisms?
Peptide hormones use surface receptors and second messengers Steroid hormones use intracellular receptors to regulate transcription Tyrosine Kinase Receptors and GPCRs are key surface receptors Nuclear receptors act as transcription factors, altering gene expression
70
What is the function of the hypothalamus in the endocrine system?
It acts as the main integrative centre between the nervous and endocrine systems, regulating homeostasis and secreting releasing/inhibiting hormones that act on the anterior pituitary.
71
Name the hormones secreted by the hypothalamus.
CRH, TRH, GnRH, GHRH, somatostatin, dopamine, and vasopressin (ADH) and oxytocin (via the posterior pituitary).
72
What type of feedback primarily regulates hypothalamic hormone release?
Negative feedback.
73
List the hormones secreted by the anterior pituitary. | AKA Adenohypophysis
ACTH, TSH, LH, FSH, GH, and prolactin.
74
What hormone stimulates ACTH release?
Corticotropin-releasing hormone (CRH).
75
What does TSH do?
Stimulates the thyroid to release T3 and T4.
76
What is the function of prolactin?
Stimulates milk production; inhibited by dopamine.
77
What hormones are released from the posterior pituitary? | AKA Neurophypophysis
Oxytocin and vasopressin (ADH).
78
Where are posterior pituitary hormones produced?
In the hypothalamus (paraventricular and supraoptic nuclei).
79
What stimulates GH release and what inhibits it?
Stimulates:GHRH and ghrelin. Inhibits: Somatostatin and IGF-1 (negative feedback)
80
What is the function of IGF-1?
Promotes growth of bones and tissues; mediates many of GH's effects.
81
What are the effects of GH?
Increases protein synthesis, lipolysis, and blood glucose levels.
82
# (Hypothalamic–Pituitary–Adrenal) What is the role of ACTH in the HPA axis?
Stimulates cortisol release from the adrenal cortex.
83
What triggers CRH release? | Corticotropin-releasing-hormone
Stress and circadian rhythm.
84
What inhibits ACTH and CRH?
Cortisol (negative feedback).
85
What does GnRH stimulate? | Gonadotropin-releasing hormone
Release of LH and FSH from the anterior pituitary.
86
What do LH and FSH do in females?
LH triggers ovulation; FSH stimulates follicle growth.
87
What do LH and FSH do in males?
LH stimulates testosterone production; FSH supports spermatogenesis.
88
What provides negative feedback to the HPG axis?
Oestrogen, progesterone, and testosterone.
89
What is the function of TRH?
Stimulates TSH release.
90
What does TSH do?
Stimulates the thyroid gland to produce T3 and T4.
91
What inhibits TRH and TSH?
High levels of T3 and T4.
92
What regulates prolactin secretion?
Mainly inhibited by dopamine.
93
What can stimulate prolactin release?
Suckling, oestrogen, TRH, and stress.
94
What are the effects of prolactin?
Milk production and inhibition of GnRH release - this can be a good birth control
95
What stimulates ADH release?
Increased plasma osmolality and low blood volume.
96
What are the actions of ADH?
Water retention (via kidneys) and vasoconstriction.
97
What stimulates oxytocin release?
Stretch of cervix, nipple stimulation (suckling), and emotional bonding.
98
What are the functions of oxytocin?
Uterine contraction during labour and milk ejection.
99
What is the neuroendocrine system?
A system where the nervous system interacts with the endocrine system to regulate physiological processes via hormone release.
100
What is the key difference between endocrine and exocrine glands?
Endocrine glands secrete hormones directly into the bloodstream, while exocrine glands secrete through ducts to the outside of the body or into the digestive tract.

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