topic 11 (endocrine system)

Question 1

Explain the difference between neural and hormonal control of homeostasis

Answer 1

• Neural Control: Fast-acting, short-duration responses through nerve impulses; involves neurotransmitters.
• Hormonal Control: Slower onset, longer-duration responses through hormones released into the bloodstream; involves endocrine glands.

Question 2

Explain how hormone release is regulated.

Answer 2

• Negative Feedback: Most common; hormone levels inhibit further release (e.g., thyroid hormones).
• Positive Feedback: Rare; hormone levels stimulate further release (e.g., oxytocin during childbirth).
• Neural Stimuli: Nerve fibers stimulate hormone release (e.g., adrenaline from adrenal medulla).
• Hormonal Stimuli: Hormones stimulate other endocrine glands to release their hormones (e.g., hypothalamus and pituitary gland).

Question 3

Explain half-life, onset, and duration of hormone activity.

Answer 3

• Half-life: Time taken for the hormone concentration to reduce by half; varies from minutes to hours.
• Onset: Time from hormone release to the first signs of activity; varies by hormone and target cell.
• Duration: Length of time the hormone exerts its effects; depends on hormone half-life and receptor interaction.

Question 4

Describe the three different types of interaction of hormones.

Answer 4

• Permissiveness: One hormone needs another to exert its effects (e.g., thyroid hormone increases the effect of epinephrine).
• Synergism: Multiple hormones produce a greater effect together than the sum of their individual effects (e.g., glucagon and epinephrine).
• Antagonism: One hormone opposes the action of another (e.g., insulin and glucagon).

Question 5

Describe the structure and function of the hypothalamus.

Answer 5

• Structure: Located below the thalamus in the brain; composed of several nuclei.
• Function: Regulates homeostasis; controls the pituitary gland; synthesizes and releases hormones (e.g., TRH, CRH, GnRH, GHRH).

Question 6

Describe the structure and function of the pituitary gland.

Answer 6

• Structure: Located at the base of the brain; divided into anterior and posterior lobes.
• Function:
  
  • Anterior Pituitary: Produces hormones
    (e.g., ACTH, TSH, GH, PRL, FSH, LH).
• Posterior Pituitary: Stores and releases hormones made by the hypothalamus (e.g., ADH, oxytocin).

Question 7

Describe the structure and function of the thyroid and parathyroid glands.

Answer 7

• Thyroid Gland:
  
  • Structure: Located in the neck;
    consists of two lobes connected by an
    isthmus.
  • Function: Produces thyroid hormones
    (T3, T4) regulating metabolism and
    calcitonin which lowers blood calcium
    levels.
• Parathyroid Glands:
  
  • Structure: Four small glands located
    on the posterior surface of the
    thyroid.
  • Function: Produce parathyroid
    hormone (PTH) which raises blood
    calcium levels.

Question 8

Describe the structure and function of the adrenal glands.

Answer 8

• Structure: Located above the kidneys; consists of the cortex and medulla.
• Adrenal Cortex: Produces corticosteroids (glucocorticoids, mineralocorticoids, androgens).
• Adrenal Medulla: Produces catecholamines (epinephrine, norepinephrine).
• Function: Regulates stress response, metabolism, immune response, and blood pressure.

Question 9

Describe the structure and function of the pineal gland.

Answer 9

• Structure: Small, pea-shaped gland located in the brain.
• Function: Produces melatonin which regulates sleep-wake cycles and circadian rhythms.

Question 10

Describe the structure and function of the pancreas.

Answer 10

• Structure: Located behind the stomach; contains endocrine and exocrine tissues.
• Islets of Langerhans: Endocrine cells producing insulin (beta cells), glucagon (alpha cells), and somatostatin (delta cells).
• Function: Regulates blood glucose levels and aids digestion through enzyme secretion.

Question 11

Explain the mechanism of blood glucose regulation.

Answer 11

• Insulin: Lowers blood glucose by promoting glucose uptake in cells and glycogen storage.
• Glucagon: Raises blood glucose by promoting glycogen breakdown and glucose release from the liver.
• Negative Feedback Loop: Insulin and glucagon secretion are regulated by blood glucose levels to maintain homeostasis.

Question 12

Describe the action of hormones.

Answer 12

• Mechanism: Hormones bind to specific receptors on target cells.
• Steroid Hormones: Pass through cell membranes, bind to intracellular receptors, and affect gene expression.
• Peptide Hormones: Bind to surface receptors and initiate a second messenger cascade.
• Effects: Can influence metabolism, growth, reproduction, and homeostasis.

Question 13

Describe feedback cycles in the endocrine system.

Answer 13

• Negative Feedback: Common mechanism; a rise in hormone levels inhibits further release (e.g., thyroid hormone regulation).
• Positive Feedback: Rare; a rise in hormone levels promotes further release (e.g., oxytocin during labor).

Question 14

Identify the location of major endocrine glands.

Answer 14

• Hypothalamus: Brain, below the thalamus.
• Pituitary Gland: Base of the brain, in the sella turcica.
• Thyroid and Parathyroid Glands: Neck, around the trachea.
• Adrenal Glands: Above the kidneys.
• Pineal Gland: Brain, near the center.
• Pancreas: Abdomen, behind the stomach.

Question 15

Describe the hypothalamus as the control center of the endocrine system.

Answer 15

• Function: Regulates homeostasis, controls autonomic functions, and links the nervous system to the endocrine system.
• Hormone Production: Produces releasing and inhibiting hormones that regulate the pituitary gland (e.g., TRH, CRH, GnRH).

Question 16

Discuss diabetes and its relation to the endocrine system.

Answer 16

• Type 1 Diabetes: Autoimmune destruction of beta cells; insulin deficiency.
• Type 2 Diabetes: Insulin resistance and eventual beta-cell dysfunction.
• Symptoms: High blood glucose, frequent urination, increased thirst, and hunger.
• Management: Insulin therapy (Type 1), oral medications, lifestyle changes (Type 2).

These flashcards cover the essential aspects of the endocrine system, including the structure and function of major glands, hormone regulation, and mechanisms of action, providing a comprehensive overview of the system’s role in maintaining homeostasis.