topic 11 (endocrine system) Flashcards
1
Q
Explain the difference between neural and hormonal control of homeostasis
A
- 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.
2
Q
Explain how hormone release is regulated.
A
- 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).
3
Q
Explain half-life, onset, and duration of hormone activity.
A
- 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.
4
Q
Describe the three different types of interaction of hormones.
A
- 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).
5
Q
Describe the structure and function of the hypothalamus.
A
- 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).
6
Q
Describe the structure and function of the pituitary gland.
A
- 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).
- Anterior Pituitary: Produces hormones
- Posterior Pituitary: Stores and releases hormones made by the hypothalamus (e.g., ADH, oxytocin).
7
Q
Describe the structure and function of the thyroid and parathyroid glands.
A
- 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.
- Structure: Located in the neck;
- Parathyroid Glands:
- Structure: Four small glands located
on the posterior surface of the
thyroid. - Function: Produce parathyroid
hormone (PTH) which raises blood
calcium levels.
- Structure: Four small glands located
8
Q
Describe the structure and function of the adrenal glands.
A
- 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.
9
Q
Describe the structure and function of the pineal gland.
A
- Structure: Small, pea-shaped gland located in the brain.
- Function: Produces melatonin which regulates sleep-wake cycles and circadian rhythms.
10
Q
Describe the structure and function of the pancreas.
A
- 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.
11
Q
Explain the mechanism of blood glucose regulation.
A
- 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.
12
Q
Describe the action of hormones.
A
- 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.
13
Q
Describe feedback cycles in the endocrine system.
A
- 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).
14
Q
Identify the location of major endocrine glands.
A
- 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.
15
Q
Describe the hypothalamus as the control center of the endocrine system.
A
- 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).
