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Anatomy and Physiology of Animals, Ammonia, Polypeptides and most amine…

- - - - Water enters and leaves cells, which occurs when two solutions separated by a membrane differ in total solute concentration
      - The unit of measurement for solute concentration is Osmolarity, the number of moles of solute per liter of solution
        
        osmolarity of human blood is about 300 milliosmoles per liter; seawater is about 1,000 milliosmoles per liter
      - isosmotic
        
        Two solutions with the same osmolarity
      - Hyperosmotic
        
        When two solutions differ in osmolarity, the solution with the higher concentration of solutes is said to be hyperosmotic
      - Hypoosmotic
        
        When two solutions differ in osmolarity, the solution with the more dilute solution is said to be Hypoosmotic
    - - Osmoconformer
        
        isoosmotic with its surroundings. All osmoconformers are marine animals. An osmoconformer’s internal osmolarity is the same as that of its environment, there is no tendency to gain or lose water.
      - to control internal osmolarity independent of that of the external environment. Osmoregulation enables animals to live in environments that are uninhabitable for osmoconformers, such as freshwater and terrestrial habitats, or to move between marine and freshwater environments
        
        carries a high energy cost
        
        frequently coupled to elimination of nitrogenous waste products, such as urea
        
        Transport epithelia
        
        one or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions
      - The ultimate function of osmoregulation is to control solute concentrations in cells
    - - a dormant state which involves loss of almost all body water
  - - - Urea
        
        Mammals use Urea
        
        Less toxic than Uric acid
        
        Most energy costly
        
        product of an energy-consuming metabolic cycle that combines ammonia with carbon dioxide in the liver
      - Uric acid
  - - - Protonephridia
        
        An excretory system, such as the flame bulb system of flatworms, consisting of a network of tubules lacking internal openings.
      - Metanephridia
        
        An excretory organ found in many invertebrates that typically consists of tubules connecting ciliated internal openings to external openings.
    - - functions in both osmoregulation and excretion
    - - remove nitrogenous wastes and that also function in osmoregulation
  - - - Mammals
        
        Mammals that excrete the most hyperosmotic urine, have many juxtamedullary nephrons with loops of Henle that extend deep into the medulla. Long loops maintain steep osmotic gradients in the kidney, resulting in urine becoming very concentrated
        
        aquatic mammals that spend much of their time in fresh water have mostly cortical nephrons, resulting in a much lower ability to concentrate urine
      - Birds and Other Reptiles
        
        birds have kidneys with juxtamedullary nephrons
        
        cannot concentrate urine to the high osmolarities achieved by mammalian kidneys
      - Freshwater Fishes and Amphibians
        
        Hyperosmotic to their surroundings
        
        kidneys excrete dilute urine while their skin accumulates certain salts from the water by active transport
  - - - A combination of nervous and hormonal controls manages the osmoregulatory function of the mammalian kidney
        
        controls contribute to homeostasis for both blood pressure and blood volume
      - Antidiuretic Hormone ADH
        
        A peptide hormone, also called vasopressin, that promotes water retention by the kidneys. Produced in the hypothalamus and released from the posterior pituitary, ADH also functions in the brain
        
        Both ADH and RAAS increase water reabsorption in the kidney
        
        ADH alone would lower blood concentration via water reabsorption in the kidney
        
        RAAS helps maintain body fluid osmolarity at the set point by stimulating reabsorption
      - renin-angiotensin-aldosterone system
        
        A hormone cascade pathway that helps regulate blood pressure and blood volume.
        
        Involves juxtaglomerular apparatus
        
        specialized tissue consisting of cells of and around the afferent arteriole, which supplies blood to the glomerulus
      - atrial natriuretic peptide
        
        A peptide hormone secreted by cells of the atria of the heart in response to high blood pressure. ANP’s effects on the kidney alter ion and water movement and reduce blood pressure.
        
        opposes the RAAS
- - - - Communication between animal cells via secreted signals; the type of secreting cell and the route taken by the signal in reaching its target
    - - ormones secreted into extracellular fluid by endocrine cells reach target cells via the bloodstream or hemolymph
        
        prostaglandins: promote inflammation and the sensation of pain in response to injury
    - - Paracrine: target cells lie near the secreting cell
      - Autocrine:the secreting cells themselves are the target cells
    - - Neurotransmitters: At synapses, neurons secrete molecules that diffuse a very short distanceand bind to receptors on the target cells
      - Neurohormones: diffuse from nerve cell endings into the bloodstream
      - Pheromones: chemicals that are released into the external environment communication functions in members between own species
    - - Polypeptides
        
        two chains in its active form
      - steroids
        
        largely nonpolar (hydrophobic)
        
        lipids that contain four fused carbon rings
      - amines
  - - - The activity of endocrine cells in the duodenum, the first part of the small intestine, provides a useful example of a simple endocrine pathway
    - - the stimulus is received by a sensory neuron rather than endocrine tissue.
    - - Negative feedback: the response reduces the initial stimulus.
      - Positive Feedback: reinforces a stimulus, leading to an even greater response
    - - Pituitary Gland:a gland located at the base of the hypothalamus
      - posterior pituitary: an extension of the hypothalamus.
      - anterior pituitary:endocrine gland that synthesizes and secretes hormones in response to hormones from the hypothalamus
    - - Thyroid gland:an organ in the neck consisting of two lobes on the ventral surface of the trachea
  - - - Parathyroid Hormone: raises the level of blood through direct effects in bones and the kidneys and an indirect effect on the intestines
      - Calcitonin:a hormone that inhibits bone breakdown and enhances excretion by the kidneys.
    - - norepinephrine:are catecholamine, a class of amine hormones synthesized from the amino acid tyrosine; also functions as a neurotransmitter
      - Glucocorticoids: make more glucose available as fuel by promoting glucose synthesis from noncarbohydrate sources, such as proteins
      - Mineralocorticoids:act principally in maintaining salt and water balance
    - - Testosterone:unctions before birth, promoting development of male reproductive structures
      - play a major role again at puberty, when they are responsible for the development of male secondary sex characteristics
    - - Estradiol
      - Progesterone: In mammals, is involved in preparing and maintaining tissues of the uterus required to support the growth and development of an embryo
    - - produced by pineal gland, a small mass of tissue near the center of the mammalian brain
    - - diethylstilbestrol (DES): a synthetic estrogen
        
        exposure to DES can alter reproductive system development in the fetus