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Chapter 41
Animal Hormons
| Question | Answer |
|---|---|
| What are hormones? | chemical signals secreted by cells of the endocrine system. There are circulating, paracrine and autocrine hormones |
| What are three types of hormones? | peptides/proteins: water soluble, transported in blood, but not across membranes. Steroid hormones: lipid-soluble; must be bound to carrier proteins to be carried in blood Amine hormones: water and lipid-soluble; derivatives of amino acid tyrosine |
| The nervous system stimulates adrenal cells to secrete epinephrine into circulating blood. What kind of responses in the body does this trigger? | Heart beats faster and stronger, blood vessels in some areas constrict to send more blood to muscles, in the liver glycogen is broken down to glucose to provide quick energy, in tissue fats are mobilized as another energy source |
| Describe the endocrine system | made up of nine major endocrine glands in vertebrates. Endocrine glands are aggregations of secretory cells. Hormones are secreted to the extracellular space. Some endocrine cells are single cells in a tissue |
| Where is the pituitary gland located? | It is attached to the hypothalamus of the brain |
| What purpose does the posterior pituitary serve? | It secretes neurohormones. Oxtocin: stimulates uterine muscle contraction during birth and lactation. ADH: increases water retention in kidney |
| What purpose does the anterior pituitary serve? | Secretes tropic hormones: control other endocrine glands, growth hormones: promote growth, prolactin: breast development and milk production, Enkephalins and endorphines: natural opiates |
| What is the anterior pituitary controlled by? | The hypothalamus, which produces releasing hormones that are carried to the anterior pituitary by portal blood vessels. |
| What is purpose does the thyroid gland serve? | The gland that produces thyroxine which elevates the metabolic rates of most cells and tissues. Activated by thyrotropin stimulating hormone (TSH) released from anterior pituitary |
| What is Goiter and what can it result from? | An enlarged thyroid gland that can result from either hyperthyroidism (thyroxine excess) or hypothyroidism (thyroxine deficiency). Epithelial cells produce excess thyroxine precursor, and the follicles enlarge |
| How are the parathyroid glands important in regulating low blood calcium levels? | release of parathyroid hormone. Causes specialized cells to dissolve bone & release calcium. Promoes calcium absorption by the kidney to prevent loss in urine. Promotes vitamin D activation, which stimulates the gut to absorb calcium from food |
| How are the parathyroid glands important in regulating high blood calcium levels? | release of calcitonin from thyroid lowers calcium levels in the blood |
| What is insulin and what results from lack of insulin? | Insulin binds to receptors on target cells and allows uptake of glucose. Lack of insulin results in type 1 diabetes, lack of insulin receptors on target cells results in type 2 diabetes |
| What are the Islets of Langerhans and what do the specialized cells produce? | Clusters of endocrine cells in the pancreas. Beta cells produce insulin, alpha cells produce glucagon (stimulates the liver to convert glycogen back to glucose) and gamma cells produce somatostatin (inhibits release of both) |
| What happens after a meal when blood glucose levels rise? | The beta cells are stimulated to release insulin. Insulin then stimulates cells to use glucose and to convert it to glycogen and fat |
| What happens when blood glucose levels fall? | The pancreas stops releasing insulin, and cells switch to using glycogen and fat for energy |
| What occurs if blood glucose levels fall too low? | The cells release glucagon which stimulates the liver to convert glycogen back to glucose |
| What is the adrenal gland? | two glands; made up of adrenal medulla and cortex located on the kidneys |
| Describe the adrenal medulla | at the core of adrenal gland. Produces epinephrine and norepinephrine, a neurotransmitter |
| Where is the adrenal cortex? | surrounding the adrenal medulla. |
| What are the corticosteroids that are produced from cholesterol in the adrena cortex? | 1. Glucocorticoids:influence blood glucose concentrations and other aspects of fuel molecule metabolism. 2. Mineralocorticoids:influence extracellular ionic balance 3.Sex steroids: stimulate sexual development and reproductive activity. |
| What are the sex steroids that are produced in the gonads of humans? | Androgens: testosterone in the testes Estrogens and Progesterone in the ovaries In development, sex hormones determine whether fetus will become male and female |
| Explain puberty | Production of the sex hormones increases. Controlled by tropic hormones from the anterior pituitary |
| What are the tropic hormones that control puberty? | Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) |
| What purpose does the pineal gland serve? | produces melatonin from tryptophan. Melatonin is released in the dark; light inhibits release. Involved in photoperiodicity, which is seasonal changes in light trigger physiological changes |
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cassidylm34
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