BIPN 100: Week 5

gland

cell or organ that secretes a chemical substance

exocrine gland

contents secreted into a duct

endocrine gland

contents secreted into the extracellular space then taken into the blood

hormones

chemical messengers secreted into bloodstream, each has its own receptor

Unlike the nervous system, the endocrine system has…

diffuse, widespread effects

peptide/protein hormones

made of linked amino acids, large and hydrophilic

steroid hormones

derived from cholesterol, smaller and hydrophobic

amine hormones

made of modified amino acids, all small, some hydrophilic, some hydrophobic

peptide hormones

ER, golgi, vesicles, soluble in blood and exposed to degradative enzymes, bind to cell-surface receptors (typically GPCRs)

steroid hormones (adrenal glands, testes, ovaries)

made in smooth ER and diffuses almost immediately (hydrophobic), not soluble in blood and bound to protein carriers, diffuse into cells and bind to intracellular receptors

amine hormones

made in cytosol by modifying amino acids, catecholamines behave like peptides, thyroid hormones behave like steroids

simple endocrine reflex

endocrine gland directly senses a stimulus and responds by secreting more or less hormone

hormone release via anterior pituitary gland

neurons in hypothalamus release hormones, hormones travel through portal system to anterior pituitary, endocrine cells of anterior pituitary release their own hormones

hormone release via posterior pituitary gland

neurons in hypothalamus make hormones, stored in vesicles at axon terminal that extend into pituitary gland, neurons release hormones

tropic hormone

stimulates another endocrine gland to secrete its own hormones

long-loop negative feedback

most downstream hormone causes inhibition in hypothalamic-pathway

short-loop negative feedback

hormone from anterior pituitary inhibits the hypothalamus

hormones released at the posterior pituitary originating in the hypothalamus

vasopressin/antidiuretic hormone, oxytocin

ADH/vasopresin

causes fluid in kidneys to retain more water

oxytocin

stimulates uterine smooth muscle contraction

nontropic hormones

regulation depends on the specific hormone and the specific effect achieved

hypersecretion

hormone is secreted in excessive amounts. caused by tumors that fail to respond to negative feedback

hyposecretion

insufficient amount of hormone secreted. caused by dietary deficiency or gland atrophy (fail to secrete hormones even if activated)

deficits in signal transduction

normal amounts of hormone but inadequate cellular response. caused by non-functional receptors or second-messengers

tertiary pathology (rare)

hormone issue arises in the hypothalamus

secondary pathology

hormone issue arises in the anterior pituitary

primary pathology

hormone issue arises in target/effector gland, primarily at source of hormone

additive results

effects of multiple hormones are the sum of their individual effects, rare

synergistic effect

when the combined effect of multiple hormones is even greater than the sum of individual effects

permissive effects

when one hormone allows the other to exert its full effects

antagonistic effects

when the actions of two hormones oppose each other (i.e. downregulating receptor expression)

pulmonary circulation

exchanges CO2 for oxygen in the lungs (enters right ventricle)

systemic circulation

delivers oxygen and nutrients to tissues (enters left ventricle)

arteries

carry blood away from the heart, aorta is largest artery

coronary artery

supply blood to the heart muscle itself

veins

carry blood towards the heart, vana cavae are the largest veins

branches from aorta

artery —> arterioles —> capillaries

capillaries

the location of oxygen, nutrient, and waste exchange with tissues

branches of veins

vein —> venule —> capillary

atrioventricular nerves

tricuspid valve, bicuspid/mitral valve

semilunar valves

pulmonary valve, aortic valve

cardiomyocytes

cardiac muscle cells

contractile cells (99% of cardiomyocytes)

-generate force for pumping blood

-fire action potential in response to depolarization from pacemaker cells

-contractile unit is sarcomere

-mainly use aerobic respiration to prevent fatigue

pacemaker cells/autorhythmic cells (1% of cardiomyocytes)

-spontaneously generate action potentials (set heart beat)

-no sarcomeres and do not contract themselves

-mainly located in the right atria

intercalated discs

joins neighboring contracticle cells, contains gap junctions that allows for direct spread of ions