Endocrine System Part 2 Flashcards
What is the Thyroid Gland?
Has a multifunctional role in body function and homeostasis, located close to the parathyroid glands.
Maintains normal blood pressure, heart rate, muscle tone, digestion, reproduction, calcium homeostasis (calcitonin).
What does the Thyroid Gland produce in humans?
T4 (thyroxine) -> iodine (inactive form)
T3 (active form)
Moderately lipophilic; enter target cell by carrier-mediated transport (negatively charged)
What does insufficient T3 and T4 cause?
Hypothyroidism (Goiter) - enlargement of thyroid; iodine deficiencies?
What do Thyroid hormones control in Frogs?
Controls metamorphosis; surgical removal of thyroid gland in tadpole inhibits development and emergence of adult form. An increase in T3/T4 ratio triggers metamorphosis.
Explain: Endocrine control of growth and development is ubiquitous in animals.
Juvenile Hormone (Fatty Acid - derivative) - controls metamorphosis in insects; secreted by corpora allata. PTTH (Brain Hormone - peptide hormone, brain secretion, directly acts on endocrine gland) and Ecdyson (steroid hormone, regulates molting, level spikes) also play a role. The absence of a hormone is an important regulator.
The ___ of a hormone is an important regulator.
Absence.
What two ways does the body respond to stress?
Acute Response and Chronic Response. Different adrenal gland hormones mediates both phases.
What is the Acute Response to Stress?
Induced immediately due to the activation of sympathetic nervous division, release of hormones from adrenal medulla.
What is the Chronic Response to Stress?
Delayed by a few minutes, due to the activation of hypothalamus-pituitary-adrenal cortex axis.
What happens during the Acute Phase?
The adrenal gland secretes 2 hormones when the sympathetic nervous system is maximally active (epinephrine [75%] and norepinephrine [25%]). It prolongs the fight or flight response in the body; increasing heart rate, dilating blood vessels and airways, increasing glycogenesis, inhibiting nonessential functions.
What happens during the Chronic Phase?
[Follows acute response] Delayed for a few minutes, can go on for minutes to days. Prepares the body to cope with stress over a long period due to glucocorticoid hormones from adrenal cortex [cortisol in humans and teleost fish, corticosterone in all other vertebrates, including rates and birds].
Suppresses immunes system, regulates sodium and chloride balance, stimulates lung maturation, stimulate gluconeogenesis.
Where are Sex Hormones produced and secreted?
By the gonads (ovaries, testes).
What are the Sex Hormones?
Estrogens - maintain female reproductive system development of female features
Androgens - stimulate embryo to become male, maintain male reproductive system
What are Sex Hormones regulated by?
The Hypothalamus and Anterior Pituitary; hypothalamic pituitary gonadal axis.
Hypothalamus -> anterior pituitary -> follicle-stimulating hormone (FSH) & luteinizing hormone (LH) -> gonads
FSH and LH have different roles in different genders.
