Chemical Mediators

Question 1

What are neurotransmitters, and where are they released from?

Answer 1

Neurotransmitters are chemicals released from the presynaptic nerve terminal that act on the postsynaptic membrane.

Question 2

How are neurotransmitters classified?

Answer 2

They can be classified as inhibitory or excitatory, depending on the properties of the receptor they bind to, not the nature of the neurotransmitter itself.

Question 3

What is an example of a neurotransmitter, and where is it released?

Answer 3

Acetylcholine is an example that is released at various tissues in the body, including epithelial, muscle, and nerve tissues.

Question 4

Name the three different chemical structures of hormones.

Answer 4

The three types are amino acid-derived hormones, peptide hormones, and lipid-based hormones.

Question 5

What role do hormones play in the body?

Answer 5

Hormones are part of endocrine signalling and are released from glands in the endocrine system, influencing various bodily functions.

Question 6

What are amino acid-derived hormones? Provide examples.

Answer 6

These are small molecules structurally related to amino acids. Examples include thyroid hormones, melatonin, and catecholamines (noradrenaline, adrenaline, dopamine).

Question 7

What is an example of a lipid hormone, and what is its significance?

Answer 7

Thromboxane is a lipid hormone produced by platelets, affecting various processes, and oestrogen is an example of a steroid hormone.

Question 7

Describe peptide hormones and provide examples.

Answer 7

Peptide hormones are chains of amino acids typically synthesized as prohormones that need conversion to become active. Examples include glycoproteins and insulin.

Question 8

What are cytokines, and what is their role in the immune system?

Answer 8

Cytokines are small proteins that modulate immune responses, playing vital roles in infection, inflammation, and cancer.

Question 9

Differentiate between autocrine, paracrine, and endocrine signalling of cytokines.

Answer 9

Autocrine: The same cell secretes and receives the signal.
Paracrine: The signal is secreted to nearby cells.
Endocrine: The signal travels through the circulatory system to distant cells.

Question 10

What are growth factors, and what are their effects?

Answer 10

Growth factors are chemicals that stimulate cell proliferation and wound healing. Their effects include proliferation, differentiation, cell growth, migration, and angiogenesis.

Question 11

Provide examples of growth factors.

Answer 11

Examples include epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF).

Question 12

What is the primary function of neurotransmitters?

Answer 12

Neurotransmitters transmit signals between neurons and other cells, facilitating communication within the nervous system.

Question 13

What is the role of the thyroid hormones?

Answer 13

Thyroid hormones regulate metabolism, growth, and development in the body.

Question 13

Can some neurotransmitters also function as hormones? If so, provide an example.

Answer 13

Yes, some neurotransmitters can act as hormones. An example is norepinephrine, which functions as both a neurotransmitter and a hormone.

Question 13

How do amino acid-derived hormones differ from peptide hormones in terms of structure?

Answer 13

Amino acid-derived hormones are small molecules derived from single amino acids, while peptide hormones are chains of amino acids.

Question 14

What is the significance of lipid-based hormones in the body?

Answer 14

Lipid-based hormones, such as steroid hormones, play crucial roles in regulating various physiological processes, including metabolism, immune function, and reproductive functions.

Question 15

What types of receptors do lipid hormones typically bind to?

Answer 15

Lipid hormones usually bind to intracellular receptors, as they can easily pass through cell membranes due to their lipid-soluble nature.

Question 16

Describe the role of chemokines in the immune response.

Answer 16

Chemokines are a subset of cytokines that direct the movement of immune cells to sites of infection or inflammation, aiding in the immune response.

Question 17

What is the effect of interferons in the immune system?

Answer 17

Interferons are cytokines that help regulate the immune response, particularly in antiviral defence, and can enhance the activity of immune cells.

Question 18

How do growth factors promote wound healing?

Answer 18

Growth factors stimulate cell proliferation, migration, and differentiation, all of which are essential for tissue repair and regeneration during the healing process.

Question 19

What is angiogenesis, and how is it related to growth factors?

Answer 19

Angiogenesis is the formation of new blood vessels. Growth factors, such as vascular endothelial growth factor (VEGF), promote this process, supplying oxygen and nutrients to healing tissues.

Question 20

What are eicosanoids, and what role do they play in the body?

Answer 20

Eicosanoids are signalling molecules derived from fatty acids that have various roles, including regulating inflammation and immune responses.

Question 21

Can the same growth factor have different effects on different cell types?

Answer 21

Yes, the effects of a growth factor can vary depending on the type of receptor present on different cell types and the specific signalling pathways activated.

Question 22

Why is the receptor type important for the action of neurotransmitters and hormones?

Answer 22

The type of receptor determines the response of the target cell to a neurotransmitter or hormone, as different receptors can initiate distinct signalling pathways.

Question 23

What distinguishes excitatory neurotransmitters from inhibitory neurotransmitters?

Answer 23

Excitatory neurotransmitters promote the generation of action potentials in the postsynaptic neuron, while inhibitory neurotransmitters decrease the likelihood of action potentials occurring.

Question 24

Name a common excitatory neurotransmitter and its function.

Answer 24

Glutamate is a common excitatory neurotransmitter involved in cognitive functions like learning and memory.

Question 25

What is the role of insulin as a peptide hormone?

Answer 25

Insulin regulates glucose levels in the blood by facilitating the uptake of glucose into cells, particularly in muscle and fat tissues.

Question 26

How do steroid hormones differ in their mechanism of action compared to peptide hormones?

Answer 26

Steroid hormones typically pass through the cell membrane and bind to intracellular receptors, affecting gene expression, while peptide hormones bind to receptors on the cell surface and activate signalling pathways.

Question 27

What is the function of tumour necrosis factor (TNF)?

Answer 27

TNF is a cytokine involved in systemic inflammation and is one of the cytokines that make up the acute phase reaction, playing a role in immune regulation and cell apoptosis.

Question 28

How do cytokines communicate their effects to target cells?

Answer 28

Cytokines bind to specific receptors on target cells, triggering intracellular signalling cascades that lead to physiological responses.

Question 29

What is the role of growth factors in angiogenesis?

Answer 29

Growth factors like VEGF promote the growth of new blood vessels from existing ones, facilitating increased blood supply to tissues, especially during healing.

Question 30

Can hormonal signals have both short-term and long-term effects? Provide an example.

Answer 30

Yes, hormonal signals can have both short-term and long-term effects. For example, adrenaline can trigger an immediate fight-or-flight response, while chronic stress can lead to long-term changes in cortisol levels, affecting metabolism and immune function.

Question 31

What type of signalling involves a cytokine affecting nearby cells?

Answer 31

This is known as paracrine signalling, where the cytokine is secreted to nearby cells to elicit a response.

Question 32

Describe the function of melatonin as a hormone.

Answer 32

Melatonin regulates sleep-wake cycles and circadian rhythms, primarily in response to light-dark cycles.

Question 33

What is the significance of feedback mechanisms in hormone regulation?

Answer 33

Feedback mechanisms help maintain homeostasis by regulating hormone levels. For example, negative feedback inhibits hormone production when levels are sufficient, while positive feedback enhances hormone production in response to specific stimuli.

Question 34

How do lipids contribute to the production of eicosanoids?

Answer 34

Eicosanoids are derived from fatty acids in membrane phospholipids; when released, they can produce various signalling molecules involved in inflammation and immune responses.

Question 35

What role do chemokines play in the immune system?

Answer 35

Chemokines act as signaling molecules that attract immune cells to sites of infection or injury, facilitating an effective immune response.

Question 36

Can growth factors be involved in both normal and pathological processes?

Answer 36

Yes, growth factors can promote normal physiological processes such as wound healing but can also contribute to pathological conditions like cancer by promoting excessive cell proliferation.

Question 37

What is the role of nitric oxide in the body?

Answer 37

Nitric oxide acts as a signalling molecule involved in various processes, including vasodilation, neurotransmission, and immune response modulation.