Describe structural and functional relationships between the hypothalamus and the pituitary gland.
The pituitary gland is a pea-sized gland located immediately beneath the hypothalamus connected by the pituitary stalk, or more technically, the infundibulum.
Posterior Pituitary Lobe is a down growth of hypothalamic neural tissue.
Anterior Pituitary Lobe has vascular connection to hypothalamus. Functional relationship: The hypothalamus controls release of hormones from the pituitary gland in two different ways:
-Posterior pituitary lobe has a neural connection with the hypothalamus via nerve bundle called the hypothalamic-hypophyseal tract., OXYTOCIN & ADH, are hormones made and released by neurons in the hypothalamus through neurosecretion into the posterior pituitary lobe were they are then stored.
-The Anterior pituitary lobe has vascular connection with the hypothalamus, which carries releasing and inhibiting hormones to anterior pituitary lobe to regulate hormone secretion [GH, TSH, ACTH, FSH, LH, PRL]
List and describe the chief effects of anterior pituitary hormones.
• Growth Hormone (GH) – Anabolic hormone, stimulates somatic growth, mobilizes fats, spares glucose Glycogen breakdown and glucose release to blood (anti-insulin effect) – target organs liver, muscle, bone, cartilage and other tissue
• Thyroid stimulating hormone (TSH)– stimulates thyroid gland to release thyroid hormone. Stimulates normal development and secretory activity of thyroid. Release triggered by thyrotropin-releasing hormone from hypothalamus.
• Adrenocorticotropic hormone (ACTH) – promotes the release of glucocorticoids and androgens (mineralocorticoids to a lesser extent) target Adrenal cortex
• Follicle-stimulating hormone (FSH) – In females stimulates ovarian follicle maturation and estrogen production, in males stimulates sperm production. Targets ovaries and testes
• Luteinizing hormone (LH) - in females triggers ovulation and stimulates ovarian production of estrogen and progesterone, in males promotes testosterone production. Targets ovaries and testes
• Prolactin (PRL) – promotes lactation. Target breast secretory tissue.
Discuss the structure of the posterior pituitary, and describe the effects of the two hormones it releases.
Structure: posterior pituitary is an outgrowth of hypothalamic neural tissue
Oxytocin: stimulates uterine contractions, initiates labor and initiates milk injection. Acts as neurotransmitter in the brain: involved in sexual & affectionate behavior, promotes nurturing, couple bonding & trust.
ADH: stimulates kidney tubule cells to reabsorb water, inhibits/ prevents urine formation and helps body avoid dehydration and water overload.
List three kinds of interaction of different hormones acting on the same target cell
-Permissiveness: one hormone cannot exert its effects without another hormone being present.
Lack of thyroid hormone delays reproductive development.
-Synergism: more than one hormone produces same effects on target cell amplification. both glucagon (pancreas) and epinephrine causes the liver to release glucose into the blood if they act together, the amount of glucose released is about 150% of what is released when each hormone acts alone.
-Antagonism: one or more hormones oppose(s) action of another hormone.
Insulin which lowers blood glucose levels, is antagonized by glucagon, which raises blood glucose levels.
Describe structure, location and important effects of the two groups of hormones produced by the thyroid gland. Structural relationship: Two lateral lobes connected by median mass called isthmus. The thyroid gland is shaped like a butterfly and usually weighs less than one ounce. The thyroid cartilage covers the larynx and produces the prominence on the neck known as the Adam's apple.
T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms
T3 (triiodothyronine); has