Chapter 16 Flashcards
(52 cards)
What is the endocrine system?
The body’s second great regulatory system.
Integrated system of small organs that involve release of extracellular signaling molecules known as hormones
What does the endocrine system do?
Regulates cellular activities by means of chemical messengers called hormones.
Hormones act at sites independent of secretion.
Short and long-term regulatory functions.
How does the endocrine system differ from the nervous system control?
Neurons directly innervate a tissue.
Stimulation is direct and immediate.
What are the major endocrine organs are?
- Hypothalamus
- Pituitary gland (anterior and posterior)
- Thyroid and Parathyroid
- Pancreas
- Adrenal glands
- Gonads
- Other tissues and organs: adipose cells, pockets of cells in the walls of the small intestine, stomach, kidneys, and heart
What are hormones?
Chemical messenger secreted by cells into the extracellular fluids that affect other parts of the body
Classifications of hormones?
- Amino acid-based: 1 or more amino acids (amines, peptides, protein)
- Steroids: derived from cholesterol (gonadal, adrenocortical)
- Eicosanoids: biologically active lipids with local hormone-like activity
What are autocrines?
Chemicals that exert effects on the same cells that secrete them
What are paracrines?
Locally acting chemicals that affect cells other than those that secrete them
Are autocrines and paracrines considered hormones?
No because hormones are long-distance chemical signals
How do hormones exert a biological effect on a tissue?
Receptors !
1. Membrane bound
2. Intracellular
What is target cell specificity?
How the same hormones affect some tissues/organs differently than others
How do we regulate hormone activity?
- Hormone concentration: rate of release; rate of inactivation/removal; 1/2 life
- Receptor concentration: cells can increase or decrease the number of receptors expressed
How are hormones removed from the blood?
Degrading enzymes: the kidneys and liver enzyme systems
What are the three types of hormone interaction?
- Permissiveness: one hormone cannot exert its effects without another hormone being present.
- Synergism: more than one hormone produces the same effects on a target cell
- Antagonism: one of more hormones opposes the action of another hormone
What is humoral stimulation?
Pertaining to elements in the blood or other body fluids.
Capillary blood contains low concentration of Ca2+, which stimulates secretion of parathyroid hormone (PTH) by parathyroid glands
What is neural stimulation?
Regulated by direct nervous system input.
Preganglionic sympathetic fibers stimulate adrenal medulla cells to secrete catecholamines (epinephrine and NE)
What is hormonal stimulation?
Regulated by hormones.
The hypothalamus secretes hormones that stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones
What is neurohypophysis?
Posterior lobe (neural tissue) and the infundibulum.
Receives, stores, and secretes hormones from the hypothalamus.
Explain the pathway that oxytocin and ADH travel from the hypothalamus to the posterior pituitary gland.
- Hypothalamic neurons synthesize oxytocin and ADH.
- Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary.
- Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
- Oxytocin and ADH are released into the blood when hypothalamic neurons fire.
What is adenohypophysis?
Anterior lobe, made up of glandular tissue.
Pathology of Growth Hormone?
Class of hormone: protein.
Regulation of secretion: negative feedback control; hormonal stimulation.
Receptor: membrane bound.
Stimulated by: secretion of GHRH by hypothalamus. Produced by somatotropic cells of the anterior lobe.
Inhibited by: secretion of GHIH by hypothalamus.
Target: liver, muscle, bone, cartilage; somatic growth.
Effects:
- Direct effects: anti-insulin actions (stimulate secretion of energy substrates) and secretion of IGFs
- Indirect effects: stimulates bone growth (caused by secretion of IGFs)
Hypersecretion of GH
Childhood: pituitary gigantism (before growth plates seal).
Adults: acromegaly
Hyposecretion of GH
Infant: hypoglycemia.
Childhood: pituitary dwarfism.
Adult: loss of lean tissue mass
Pathology of thyroid hormones
Class of hormone: amine and lipid soluble.
Regulation of secretion: negative feedback control; hormonal stimulation.
Receptor: intracellular.
Stimulated by:
- secretion of TRH (thyrotropin releasing hormone) by hypothalamus.
- secretion of TSH (thyroid stimulating hormone) by anterior pituitary.
Inhibited by:
Targets: virtually every cell in the body. Permissive
Effects:
- glucose oxidation
- increasing metabolic rate
- heat production
- maintains BP
- regenerates tissues
- develops skeletal and nervous systems
- maturation of reproduction