Exam #3 - Exercise Endocrinology Potential Short Answer Question Topic

Compare & contrast the roles of insulin & glucagon in regulating blood glucose

- Insulin and glucagon are pancreatic hormones that work together to maintain blood glucose.

- Insulin is secreted by beta cells when blood glucose rises, especially after a meal. It promotes glucose uptake in muscle and adipose tissue, stimulates glycogen and fat storage, and suppresses glucose production by the liver. In muscle, insulin activates signaling that moves GLUT4 transporters to the cell membrane.

- Glucagon is secreted by alpha cells when blood glucose is low. It acts primarily on the liver through a GPCR/cAMP pathway, stimulating glycogen breakdown and gluconeogenesis to release glucose into the bloodstream. Therefore, insulin favors glucose uptake and storage, while glucagon favors glucose mobilization and production.

How hormones regulate metabolism and change during exercise

Hormones coordinate the availability and use of carbohydrates, fats, and proteins.

- During exercise, epinephrine generally rises with intensity, helping increase cardiovascular support and mobilize stored fuels.

- Glucagon often rises and insulin often falls, helping maintain blood glucose while working muscle increases glucose uptake through contraction-mediated GLUT4 movement.

- GH may increase during sufficiently intense or prolonged exercise, supporting lipolysis and fuel availability.

- Cortisol may also increase during prolonged or stressful exercise and supports gluconeogenesis and substrate mobilization

Compare and contrast the roles of leptin, ghrelin, and CCK in regulating hunger

- Leptin is released mainly by adipose tissue and signals longer-term energy stores to the brain, generally suppressing appetite.

- Ghrelin is produced mainly by the stomach and stimulates hunger, often rising before meals.

- CCK is released from the intestine in response to nutrients, especially fats and proteins, and supports digestion while contributing to meal-related satiety.

Explain the "Central Dogma of Genetics": transcription and translation in relation to adaptations to training

Describes how genetic information is used to produce proteins.

- During transcription, a gene's DNA sequence is used as a template to produce messenger RNA (mRNA).

- During translation, ribosomes read the mRNA and assemble amino acids into a protein.

Discuss a cell-signaling pathway and explain how it works (cAMP)

A hormone binds a GPCR, activating a Gs protein. Gs activates adenylyl cyclase, which produces cAMP from ATP. cAMP activates protein kinase A (PKA), which phosphorylates target proteins and changes their activity. The cellular response depends on the hormone and tissue

Discuss a cell-signaling pathway and explain how it works (JAK/STAT)

Growth hormone binds its cell-surface receptor, activating receptor-associated JAK enzymes. JAK phosphorylates STAT proteins, which pair up and enter the nucleus. STAT proteins regulate gene transcription, changing the production of proteins involved in growth and metabolism.

Discuss a cell-signaling pathway and explain how it works (AMPK)

During exercise, muscle contraction increases energy demand and can activate AMPK-related energy sensing. AMPK helps coordinate energy supply by promoting energy-producing processes and supporting fuel use. Exercise also activates other contraction pathways that increase GLUT4 movement to the muscle-cell membrane, allowing more glucose to enter even when insulin signaling is impaired.

Explain the renin-angiotensin system

- When kidney perfusion or blood pressure falls, sodium chloride delivery to the macula densa decreases, or sympathetic beta-1 stimulation increases, the kidneys release renin.

- Renin cleaves angiotensinogen into angiotensin I. ACE converts angiotensin I into angiotensin II.

- Angiotensin II constricts blood vessels and stimulates aldosterone release, thirst, and other water-conserving responses.

- Aldosterone increases sodium reabsorption by the kidneys, and water can follow sodium, helping restore blood volume and pressure.

- As perfusion and effective circulating volume recover, renin release decreases through negative feedback.

How and why specific hormones level respond to acute exercise and how these responses may change after months of training

After months of training, the same absolute workload may produce a different hormonal response because the person has become more efficient and the workload represents a different relative intensity. Regular exercise generally improves insulin sensitivity and muscle glucose handling.