Review #5 , 2 Flashcards
(19 cards)
Endocrine glands
DUCTLESS; secrete hormones DIRECTLY into bloodstream (pancreas, pineal gland, pituitary gland, ovaries, testes, adrenal gland, and thyroid )
Hormones
chemical messengers produced in one part of body, secreted into/ transported via bloodstream, affects/ acts on/ distant target cells. Hormones = highly specific for target cells (only bind to specific receptors). Once hormones bind, activate those cells and tissues to regulate body functions (slower to initiate response, but more prolonged than nervous system).
Two main types of hormones:
Steroid hormones and Peptide hormones
Steroid Hormones
Examples:
Estrogen, Testosterone, Progesterone
Made From:
Cholesterol (lipid soluble/ nonpolar)
How They Work:
Pass through plasma membrane (phospholipid bilayer) of target cells (small/ hydrophobic)
Bind to receptor protein(s) in cytoplasm of target cell, forming receptor-hormone complex - note that these receptor proteins are often gene regulatory proteins
Receptor-hormone complex moves into nucleus (through nuclear membrane) and regulates gene expression/ acts directly on DNA/ binds to DNA (directly promotes or inhibits transcription of specific genes - which controls protein production in a cell – drastically altering the biochemistry of the cell/ tissue etc.)
Does not require use of ATP
Peptide Hormones
Examples:
Insulin, ADH, Glucagon, FSH, LH, Prolactin, Oxytocin, Growth hormones, Leptin
Made From:
Amino acids (proteins/ water soluble/ polar)
How They Work:
Do NOT enter target cells (cannot pass through plasma membrane), so bind to receptors on plasma membrane surface (of target cells)
Binding to receptors activates cascade of reactions, carried out by secondary messengers in cytoplasm of cell (such as cAMP), which activates or inhibits enzymes/ changes cell’s physiology (such as protein kinase, in the cell).
Requires use of ATP
Emphysema
chronic/ progressive disease, walls of alveoli damaged/ lose elasticity = form of COPD
-Consequences= alveoli break down/ rupture, become large/ irregularly shaped with gaping holes in them, ↓
elasticity (so ↑total lung volume at rest), ↓ SA, ↓O2 can reach the bloodstream
-Causes = SMOKING/ tobacco/marijuana/fumes/coal dust/air pollution (irritants cause damage, then phagocytes
(WBC’s) come to “help” damaged tissue/ secrete elastase = breaks down elastic fibers in alveolar walls) - In rare
cases, hereditary gene mutation causes deficiency in elastase enzyme inhibitor (causes hereditary emphysema)
Treatments = NO CURE, but treatments help = bronchodilators (improve airflow by relaxing bronchial muscles),
inhaled steroids (reduce inflammatory response/ phagocytes), oxygen supplementation, elastase enzyme inhibitors,
surgery (remove damaged tissue/ lung transplant)
Over time, body IS able to acclimate to lower O2 in air! HOW?
- RBC production increases (more RBC’s = more hemoglobin = more O2 transport) - causes kidneys to excrete excess
fluid though = more urination = dehydration (so need more H2O)- RBCs are produced with more hemoglobin molecules (these also have slightly different structure so higher affinity for
oxygen - shifts oxygen dissociation curve left - ↑ % saturation of Hb at lower pO2) - Vital capacity increases (more air in/out per breath = increased rate of gas exchange)
- Muscles make more myoglobin (capillaries more dense too – more O2 diffusion into cells and binding by myoglobin)
- Kidneys secrete alkaline urine (remove excess HCO3- to improve buffering of blood pH)
- Greater lung surface area/ larger chest size – if living permanently at high altitude
- RBCs are produced with more hemoglobin molecules (these also have slightly different structure so higher affinity for
At higher altitudes
At higher altitudes, less pressure = less O2 = lower % saturation of hemoglobin in lungs = less O2 to cells/ tissues
Symptoms of low oxygen intake/ hypoxia = breathlessness, headache, fatigue, rapid pulse, nausea - note that increased ventilation rate causes ↑ loss of H2O too
Myoglobin
Higher affinity for oxygen than hemoglobin, so shifted farthest left (shows it is saturated at EXTREMELY LOW oxygen concentrations, so can STORE O2 in skeletal muscle no matter what body O2 concentrations are);
Curve for myoglobin is NOT S-SHAPED (because only ONE polypeptide chain, so NO COOPERATIVE binding, and only binds ONE O2 molecule at a time)(oxygen binding protein in skeletal muscles)
-Only 1 polypeptide chain with heme group; binds REVERSIBLY (but NOT cooperatively) with oxygen; stores O2 (“oxygen reserve”) in skeletal muscles to delay anaerobic respiration when O2 in blood is very low
Fetal hemoglobin:
Different structure/ shape so has HIGHER AFFINITY for oxygen (than adult hemoglobin) so binds O2 more readily (at lower pressures/ concentrations), ensuring O2 moves from mom’s hemoglobin to baby’s hemoglobin in capillaries in placenta
Hemoglobin
(oxygen binding protein in RBC’s)
-4 polypeptide chains, each with heme group; heme binds REVERSIBLY/ COOPERATIVELY with oxygen = O2 binding changes shape so hemoglobin has HIGHER affinity for O2 and binds more of it more readily/ easily (and vice versa too) - promotes oxygen loading in lungs and oxygen release at/ to respiring tissues
Oxygen-dissociation curves show affinity/ saturation of hemoglobin for oxygen at different concentrations (partial pressures = partial pressure of gas in a mixture) of oxygen
-At LOW pO2 (partial pressure of oxygen), affinity/ saturation of
hemoglobin is also LOW; happens when hemoglobin is RELEASING O2 to
respiring/ exercising cells/ tissues (oxyhemoglobin dissociates)
-At HIGH pO2, affinity/ saturation of hemoglobin is also HIGH; happens in
alveoli in lungs (forming more oxyhemoglobin in RBC’s)
For HEMOGLOBIN, shows an S-shaped (sigmoid) curve due to cooperative
binding of oxygen molecules with hemoglobin
Gas Transport
Alveoli in lungs carry out gas exchange with the blood; made up of:
-type I pneumocytes (flat/ increased surface area for gas exchange via diffusion),
-type II pneumocytes (cuboidal - secrete surfactant to reduce surface tension to prevent alveoli collapse/ sticking together and allow gases to dissolve for easier diffusion into blood)
-capillaries (red blood cells carry O2/ CO2; endothelium one cell thick = minimize diffusion distance)
Growth Hormone
Growth hormone (HGH/ somatotropin) is NATURALLY occurring hormone in body
An anabolic, peptide hormone that stimulates growth:
acts directly on adipose tissue (reduces adipose cells)
acts indirectly on muscles/ bones (increases mass/ growth) - does this by activating IGF (insulin growth factor) in liver; IGF increases bone growth and muscle mass
Some athletes use as a performance enhancer - difficult to detect through urine, but now able to distinguish between natural and “doping” forms in blood tests (use is banned in sports/ athletic competitions) -has a SHORT half life though!
Hypothalamus controls ….
hormone secretion by anterior and posterior pituitary
Anterior Pituitary
Hypothalamus produces “releasing factors,” released into portal blood vessels by neurosecretory cells, cause endocrine cells in anterior pituitary to release hormones into blood
-TSH (thyroid-stimulating hormone): Targets cells of the thyroid to make and secrete thyroxin (increases metabolic rate/ energy use/ heat production)
-FSH (follicle-stimulating hormone): Targets cells of gonads. In males causes meiosis I to produce secondary spermatocytes. In females it causes primary oocyte to mature and complete meiosis I to produce one secondary oocyte and one polar body.
-LH (luteinizing hormone): Targets cells of the gonads In males it causes Leydig cells to make and secrete testosterone (for sperm production). In females, it causes ovulation of an oocyte.
-Prolactin: Targets cells of the mammary glands for lactation (growth and produce milk; inhibited by progesterone so no milk prior to birth)
-Growth hormone (GH): Targets cells throughout the body; stimulates mitosis
Posterior Pituitary
Hypothalamus neurosecretory cells extend down into posterior pituitary and release hormones into blood (hormones produced by hypothalamus)
-ADH (Antidiuretic hormone): Targets cells of the collecting duct of kidney, increasing the amount of water that is reabsorbed into the blood
-Oxytocin: Produced in neurosecretory cells in hypothalamus but stored in/ secreted from posterior pituitary; Targets cells of uterine muscles and mammary glands, causing contractions (for birth) and milk secretion during lactation (note that nursing/ suckling then causes oxytocin to be released to allow milk to be secreted too - positive feedback until baby finished feeding)
Overall, pituitary controls MARGE:
Metabolism (TSH), Adult development
(FSH/ LH), Reproduction (FSH/ LH), Growth (GH), Equilibrium/
homeostasis (ADH and water balance)
BOTH Steroid and Peptide Hormones
Act on target cells/ organs; Travel through the bloodstream; Effective at very low concentrations; Effects last longer than neurotransmitters
