Week 12 overview of hormones / endocrine system

Question 1

Intracellular messengers systems

Answer 1

Intercellular messenger systems are crucial for communication between cells, allowing them to coordinate and regulate various physiological processes. These
systems involve the release, transmission, and reception of signalling molecules
5 types;
-Neurotransmission
-Neuroendocrine
-Endocrine signalling
-Paracrine
-Autocrine

Question 2

Neurotransmission

Answer 2

Specialised form of signalling where neurons release
neurotransmitters across synapses to communicate with other neurons, muscle cells, or gland cells
Function: Enables rapid and precise communication within the nervous system, facilitating processes such as muscle contraction, sensory perception,
cognition, and reflex actions

Question 3

Neuroendocrine Signalling

Answer 3

Involves neurons that release hormones into the bloodstream,
bridging the gap between the nervous system and the endocrine system
Function: Regulates long-distance signalling and systemic processes such as stress responses, growth, metabolism, and reproduction

Question 4

Endocrine Signalling

Answer 4

Hormones are secreted by endocrine glands into the
bloodstream and carried to distant target cells
Function: Controls long-distance communication and systemic physiological processes such as metabolism, growth, and homeostasis

Question 5

Paracrine Signalling

Answer 5

Cells release signalling molecules that affect nearby target cells within the same tissue
Function: Important for local communication and coordination within tissues, such as immune responses, wound healing, and tissue repair
Signalling Molecules: Growth factors, cytokines, and local mediators like nitric oxide.
->Mechanism: Signalling molecules diffuse over short distances to bind to receptors on neighbouring cells

Question 6

Autocrine Signalling

Answer 6

Self regulation system;
Cells release signalling molecules that bind to receptors on their own surface
Allows cells to regulate their own activity, often involved in growth
regulation, survival, and differentiation
Signalling molecules are secreted by the cell and bind to receptors on the same cell, leading to a feedback loop

Question 7

Endocrine system

Answer 7

The endocrine system is a network of glands and organs that produce, store, and
secrete hormones. These hormones regulate various bodily functions, including
growth, metabolism, reproduction, and homeostasis. The endocrine system works in
conjunction with the nervous system to maintain the body’s internal environment and respond to external changes
Factors (hormones) produced by the glandular cells (site of production) are secreted into the bloodstream and travel to
their target cells (site of action) to produce a physiological response

Question 8

Key components of endocrine system

Answer 8

Glands: Specialised organs that produce and secrete hormones. (site of production)
Hormones: Chemical messengers released into the bloodstream, affecting distant target cells
Receptors: Proteins on or inside target cells (site of action) that bind to specific hormones, triggering a response

Question 9

Functions of endocrine system

Answer 9

->Regulation of Metabolism: Thyroid hormones (T3 and T4) increase the rate of metabolism in body cells
->Growth and Development: Growth hormone (GH) stimulates growth in tissues and bones
->Homeostasis: Insulin and glucagon from the pancreas regulate blood glucose levels
->Stress Response: Cortisol from the adrenal cortex helps the body manage stress
->Reproduction: Sex hormones (oestrogen, progesterone, testosterone) regulate reproductive cycles and gamete production

Question 10

Clinical relevance (endocrine system)

Answer 10

-Understanding the endocrine system is essential for diagnosing and treating
hormonal imbalances and related diseases
-Hormone replacement therapies and medications that modulate hormone levels are common treatments for endocrine disorders

Question 11

Hormone types

Answer 11

Structural (chemical) differences
distinguish the synthesis, storage, transportation and biological functions of hormones;
-Peptide hormones
-Steroidal hormones
-Amino acid- derived hormone
-Eicosanoids

Question 12

Hormones

Answer 12

Hormones are chemical messengers produced by endocrine glands and play crucial roles in regulating various physiological processes
They can be classified based on
their chemical structures, which influence their synthesis, storage, transportation,
and biological functions
The main types of hormones include;
Peptide hormones, steroid hormones, amino acid-derived hormones, and eicosanoids

Question 13

Peptide hormones

Answer 13

Chemical structure: chains of amino acids
-Small chains (e.g., TRH: contains 3 AAs)
-Large chains (e.g., LH/ FSH 80aas)
Mostly secreted from the hypothalamus, pituitary, pancreas and GIT
Examples: Insulin, glucagon, growth hormone (GH), oxytocin, antidiuretic hormone (ADH)

Question 14

Peptide hormone - synthesis

Answer 14

Synthesised in the rough endoplasmic reticulum (ER) as larger precursor molecules called preprohormones, which are then processed into prohormones and finally into active hormones
Peptide hormones are stored in the secretory granules/vesicles. They require stimuli for release (exocytosis)

Question 15

Peptide hormones - storage

Answer 15

Stored in secretory vesicles within the endocrine gland cells

Question 16

Peptide hormones - transport

Answer 16

Hydrophillic -> soluble in blood plasma, freely circulate in the blood vessel
Short half life -> minutes

Question 17

Peptide hormones -> biological functions

Answer 17

Generally act on cell surface receptors to trigger signal
transduction pathways, leading to rapid cellular responses. They are involved in processes such as metabolism, growth, and water balance

Question 18

Steroidal hormones - structure

Answer 18

Derived from cholesterol and has a characteristic four-ring structure
Examples: Cortisol, aldosterone, oestrogen, testosterone, progesterone

Question 19

Steroidal hormones - synthesis

Answer 19

Synthesised in the smooth endoplasmic reticulum and mitochondria from cholesterol-> Enzymatic conversion of precursor (cholesterol base) molecules into hormone
As these hormones are lipophilic, they easily diffuse through the cell membrane into blood vessel (concentration gradient)

Question 20

Steroidal hormones - storage

Answer 20

Not stored in the cells , not stored in large quantities - synthesised on demand

Question 21

Steroidal hormones - transportation

Answer 21

Insoluble in blood plasma and require carrier proteins (e.g., albumin, sex hormone-binding globulin) for transportation
Half-life: hours to days

Question 22

Steroidal hormones - biological functions

Answer 22

Typically act on intracellular receptors to regulate gene
expression, leading to slower but longer-lasting effects. They are involved in processes such as stress response, electrolyte balance, and sexual development

Question 23

Steroidal hormones - release

Answer 23

-Stimulus increase precursor level and enzyme activation
-Simple diffusion across the membrane

Question 24

Amino acid-derived hormones - structure

Answer 24

Derived from single amino acids, such as tyrosine or tryptophan
Examples: Thyroid hormones (thyroxine [T4], triiodothyronine [T3]), adrenaline (epinephrine), noradrenaline (norepinephrine), melatonin

Question 25

Amino acid-derived hormones - synthesis

Answer 25

Synthesised through enzymatic modifications of amino acids

Question 26

Amino acid-derived hormones - storage

Answer 26

Stored in vesicles within endocrine cells

Question 27

Amino acid-derived hormones - release

Answer 27

-Stimulus required
-Simple diffusion across the membrane

Question 28

Amino acid-derived hormones - transportation

Answer 28

Thyroid hormones are bound to carrier proteins (e.g., thyroxine-
binding globulin) due to their lipid solubility, while catecholamines (adrenaline,
noradrenaline) are transported freely in the blood
Half-life: hours to day

Question 29

Amino acid-derived hormones - biological functions

Answer 29

Thyroid hormones regulate metabolism and energy balance,
while catecholamines are involved in the fight-or-flight response. Melatonin regulates
sleep-wake cycles

Question 30

Eicosanoids