Physiology exam prep 4
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Questions and Answers

What is the main component of small intestine juice responsible for splitting proteins into amino acids?

  • Proteases (correct)
  • Amylases
  • Lipases
  • Nucleases

    • What is the function of enterokinase in the small intestine?

  • Splitting amino acids into dipeptides
  • Converting trypsinogen into active trypsin (correct)
  • Catalyzing the hydrolysis of sucrose into fructose and glucose
  • Hydrolyzing lipids into fatty acids and glycerin

    • What is the primary function of the large intestine in relation to digestion?

  • Chemical processing of food with imported enzymes
  • Biologic processing of food with the help of microflora
  • Water and salt reabsorption (correct)
  • All of the above

    • What is the role of the heart in maintaining blood circulation?

    <p>Providing pressure to maintain blood flow</p> Signup and view all the answers

    What is the difference between the small or pulmonary circuit and the large or systemic circuit?

    <p>The small circuit is low pressure and the large circuit is high pressure</p> Signup and view all the answers

    What is the function of calcitonin in the body?

    <p>Regulating the level of calcium and phosphorus in the blood</p> Signup and view all the answers

    What is the role of the microflora in the large intestine?

    <p>All of the above</p> Signup and view all the answers

    What is the pH of the small intestine juice?

    <p>pH 7.5</p> Signup and view all the answers

    What is the function of the capillaries in the cardiovascular system?

    <p>Supplying blood to the tissues</p> Signup and view all the answers

    What is the functional unity of the cardiovascular system?

    <p>Systemic hemodynamics, blood circulation in organs, and microcirculation</p> Signup and view all the answers

    What percentage of cardiac output is received by the kidneys?

    <p>20%</p> Signup and view all the answers

    What is the name of the first capillary network in the kidney?

    <p>Rete mirabile</p> Signup and view all the answers

    Where are cortical nephrons primarily located?

    <p>Renal cortex</p> Signup and view all the answers

    What percentage of nephrons are juxtamedullary?

    <p>20%</p> Signup and view all the answers

    What is the composition of the primary urine or ultrafiltrate?

    <p>Similar to blood plasma</p> Signup and view all the answers

    What is the name of the artery that supplies blood to the kidneys?

    <p>Renal artery</p> Signup and view all the answers

    What is the function of peritubular capillaries?

    <p>Reabsorption and secretion</p> Signup and view all the answers

    What is the name of the two main divisions of the nephron?

    <p>Renal corpuscle and renal tubule</p> Signup and view all the answers

    How much of the arterial blood received by the kidneys goes to the medulla?

    <p>10%</p> Signup and view all the answers

    What is the pressure in the renal artery similar to?

    <p>Pressure in the aorta</p> Signup and view all the answers

    What is the primary source of fuel for the central nervous system (CNS)?

    <p>Glucose</p> Signup and view all the answers

    Where does the conversion of carbohydrates to volatile fatty acids (VFAs) occur in ruminant animals?

    <p>Forestomachs</p> Signup and view all the answers

    What is the primary function of aldosterone in the zona glomerulosa?

    <p>Regulation of electrolyte reabsorption</p> Signup and view all the answers

    What is the primary effect of cortisol on glucose metabolism?

    <p>Stimulation of glucose release from the liver into the blood</p> Signup and view all the answers

    What is the name of the axis that regulates glucocorticoid secretion?

    <p>Hypothalamic-pituitary-adrenal axis</p> Signup and view all the answers

    What is the function of corticoliciberins in the regulation of glucocorticoid secretion?

    <p>Inhibition of corticotropic hormone production</p> Signup and view all the answers

    What is the role of the zona reticularis in adrenal cortex function?

    <p>Production of sex hormones</p> Signup and view all the answers

    What is the effect of glucocorticoids on the immune system?

    <p>Suppression of allergic reactions</p> Signup and view all the answers

    What is the function of zona fasciculata in the adrenal cortex?

    <p>Production of glucocorticoids</p> Signup and view all the answers

    What is the effect of hyperfunction of the zona reticularis in childhood?

    <p>Acceleration of sexual maturity</p> Signup and view all the answers

    What is the primary function of calcitonin in the body?

    <p>Regulation of calcium and phosphorus levels in the blood</p> Signup and view all the answers

    What is the effect of triiodothyronine (T3) on cellular metabolism?

    <p>It increases the intensity of cellular metabolism</p> Signup and view all the answers

    What is the main function of aldosterone?

    <p>Regulation of electrolyte reabsorption from the nephron tubules</p> Signup and view all the answers

    What is the effect of a lack of thyroid hormones on the body?

    <p>It reduces the basal metabolism</p> Signup and view all the answers

    What is the primary source of energy for the nervous system?

    <p>Carbohydrates</p> Signup and view all the answers

    What is the primary function of the zona glomerulosa of the adrenal gland cortex?

    <p>Production of mineralocorticoids</p> Signup and view all the answers

    What is the effect of calcitonin on osteoclasts and osteoblasts?

    <p>It inhibits osteoclasts and stimulates osteoblasts</p> Signup and view all the answers

    What is the primary function of the renin-angiotensin system in regulating aldosterone secretion?

    <p>It stimulates aldosterone secretion</p> Signup and view all the answers

    What is the primary function of carbohydrates in the body?

    <p>They have multiple functions, including energy source and cell component</p> Signup and view all the answers

    What is the primary source of glucose synthesis in the liver?

    <p>From glucose, glycerin, fatty acids, amino acids, and volatile fatty acids</p> Signup and view all the answers

    What is the primary form of carbohydrates absorbed in the gastrointestinal tract?

    <p>Monosaccharides</p> Signup and view all the answers

    Which of the following factors affects the absorption of nutrients in the gastrointestinal tract?

    <p>Osmotic pressure of the food</p> Signup and view all the answers

    What is the primary function of bile acid in the absorption of fatty acids?

    <p>To solubilize fatty acids in water</p> Signup and view all the answers

    In which part of the gastrointestinal tract does the most intense absorption of water and minerals occur?

    <p>Large intestine</p> Signup and view all the answers

    What is the primary form of proteins absorbed in the gastrointestinal tract?

    <p>Amino acids</p> Signup and view all the answers

    In which part of the gastrointestinal tract does the absorption of volatile fatty acids occur?

    <p>Fore-stomachs</p> Signup and view all the answers

    What is the primary function of intestinal enzymes in the absorption of proteins?

    <p>To phosphorylate amino acids</p> Signup and view all the answers

    What is the primary difference between the absorption of carbohydrates in ruminants and non-ruminants?

    <p>Ruminants absorb more carbohydrates in the forestomachs</p> Signup and view all the answers

    What is the primary function of epithelial cells in the absorption of nutrients in the gastrointestinal tract?

    <p>To facilitate active cellular processes</p> Signup and view all the answers

    Which of the following is NOT absorbed in the gastrointestinal tract?

    <p>Oxygen</p> Signup and view all the answers

    What is the primary function of proteins in animal growth and development?

    <p>Plastic processes</p> Signup and view all the answers

    What is the main difference between complete and incomplete proteins?

    <p>The presence of all essential amino acids</p> Signup and view all the answers

    What is the primary function of the liver in protein exchange?

    <p>Deamination of amino acids</p> Signup and view all the answers

    What is the primary source of protein for cows?

    <p>Ruminal microorganisms</p> Signup and view all the answers

    What is the primary function of the cough reflex?

    <p>Defense against irritants in the airways</p> Signup and view all the answers

    What is the role of the vagus nerve in the cough reflex?

    <p>Transmission of sensory information</p> Signup and view all the answers

    What is the primary result of deamination of amino acids in the liver?

    <p>Formation of ammonia</p> Signup and view all the answers

    What is the primary function of urea in the body?

    <p>Waste product</p> Signup and view all the answers

    What is the primary difference between the small and large intestine?

    <p>Function in nutrient absorption</p> Signup and view all the answers

    What is the primary function of proteins in the body's defense against microorganisms?

    <p>Antibody production</p> Signup and view all the answers

    What is the primary function of the spinal cord in relation to reflexes?

    <p>To realize reflexes through its gray matter</p> Signup and view all the answers

    What is the result of damage to the white matter of the spinal cord?

    <p>Deficits in reflexive reactions</p> Signup and view all the answers

    What is the primary function of the sneezing reflex?

    <p>To expel foreign material from the lungs</p> Signup and view all the answers

    What is the role of the epiglottis in the cough response?

    <p>To trap air within the lungs</p> Signup and view all the answers

    What is the primary function of the reflexive tone in skeletal muscles?

    <p>To resist the force of gravity</p> Signup and view all the answers

    What is the primary function of the lower centers of the sympathetic nervous system?

    <p>To control sweating and urine output</p> Signup and view all the answers

    What is the primary function of the trigeminus nerve in the sneezing reflex?

    <p>To conduct sensory information to the brain</p> Signup and view all the answers

    What is the result of spinal shock below the damaged area?

    <p>Atony and loss of reflexes</p> Signup and view all the answers

    What is the primary function of the gray matter in the spinal cord?

    <p>To contain nerve centers and realize reflexes</p> Signup and view all the answers

    What is the primary function of the white matter in the spinal cord?

    <p>To conduct nerve signals up and down the spinal cord</p> Signup and view all the answers

    What is the primary function of conduction in the CNS?

    <p>Providing communication between different parts of the CNS</p> Signup and view all the answers

    Which of the following has a higher affinity for oxygen than hemoglobin?

    <p>Myoglobin</p> Signup and view all the answers

    What would occur if there are disturbances in impulse conduction in the CNS?

    <p>Paralysis</p> Signup and view all the answers

    What is the shape of the oxygen-hemoglobin dissociation curve for adult hemoglobin?

    <p>Sigmoidal (S-shaped)</p> Signup and view all the answers

    Why does fetal hemoglobin have a higher affinity for oxygen than adult hemoglobin?

    <p>Due to its slightly different molecular structure</p> Signup and view all the answers

    What is the primary function of myoglobin in muscle cells?

    <p>To store oxygen for aerobic respiration</p> Signup and view all the answers

    What is the result of the higher affinity of myoglobin for oxygen compared to hemoglobin?

    <p>Myoglobin saturates at extremely low O2 concentrations</p> Signup and view all the answers

    How does the oxygen-hemoglobin dissociation curve for fetal hemoglobin differ from that of adult hemoglobin?

    <p>It is shifted to the left</p> Signup and view all the answers

    What is the significance of the conduction paths in the spinal cord?

    <p>They facilitate the transmission of impulses between different parts of the CNS</p> Signup and view all the answers

    What is the result of the cooperative binding of oxygen molecules in adult hemoglobin?

    <p>A sigmoidal (S-shaped) oxygen-hemoglobin dissociation curve</p> Signup and view all the answers

    What is the primary function of the medulla oblongata?

    <p>Conduction of nerve fibers and reflex functions</p> Signup and view all the answers

    What is the role of the reticular formation in the brainstem?

    <p>Activation of the brain's non-specific functions</p> Signup and view all the answers

    Which part of the brainstem is involved in the regulation of reflector movements?

    <p>Pons</p> Signup and view all the answers

    What is the primary function of the centers in the red nucleus?

    <p>Regulation of skeletal muscle tone</p> Signup and view all the answers

    What is the primary auditory center in the midbrain?

    <p>Inferior colliculus</p> Signup and view all the answers

    What is the function of the superior colliculus in the midbrain?

    <p>Primary vision center</p> Signup and view all the answers

    Which part of the brainstem is responsible for the regulation of gastrointestinal centers?

    <p>Medulla oblongata</p> Signup and view all the answers

    What is the function of the centers in the medulla oblongata that regulate skeletal muscle tone?

    <p>Static and statokinetic reflexes</p> Signup and view all the answers

    Which part of the brainstem is involved in the regulation of defense reflexes?

    <p>Medulla oblongata</p> Signup and view all the answers

    What is the primary function of the midbrain in the brainstem?

    <p>Regulation of vision and hearing</p> Signup and view all the answers

    Which brain region is involved in the regulation of very precise, complex movements such as chewing, swallowing, and finger movements?

    <p>Midbrain substantia nigra</p> Signup and view all the answers

    What is the effect of a hypertonic solution on a live cell?

    <p>The cell shrinks due to the loss of water</p> Signup and view all the answers

    Which phase of gastric juice secretion occurs before eating and is responsible for about 30% of total acid secretion?

    <p>Cephalic phase</p> Signup and view all the answers

    What is the primary function of the pons in the brain?

    <p>Conduction pathway between higher and lower brain centers</p> Signup and view all the answers

    What is the effect of an isotonic solution on a live cell?

    <p>The cell remains unaffected</p> Signup and view all the answers

    Which phase of gastric juice secretion is triggered by the direct contact of food with the stomach wall?

    <p>Gastric phase</p> Signup and view all the answers

    What is the role of the vagus nerve in the regulation of gastric acid secretion?

    <p>It stimulates the release of gastrin and histamine</p> Signup and view all the answers

    What is the effect of a hypotonic solution on a live cell?

    <p>The cell swells and potentially bursts</p> Signup and view all the answers

    Which brain region is involved in the regulation of decerebrate rigidity?

    <p>Red nucleus</p> Signup and view all the answers

    What is the percentage of total gastric acid secretion that occurs during the cephalic phase?

    <p>30%</p> Signup and view all the answers

    What is the primary function of the renin-angiotensin-aldosterone system?

    <p>Maintaining systemic blood pressure and glomerular filtration rate</p> Signup and view all the answers

    What is the effect of decreased arterial blood pressure on the renin-angiotensin-aldosterone system?

    <p>Increased production of angiotensin II</p> Signup and view all the answers

    What is the primary function of phospholipids?

    <p>Maintaining the structure and function of cell membranes</p> Signup and view all the answers

    What is the primary mechanism of transport of oxygen from maternal blood to fetal blood across the placenta?

    <p>Passive diffusion</p> Signup and view all the answers

    What is the effect of increased levels of sodium ions in the filtrate on the renin-angiotensin-aldosterone system?

    <p>Stimulation of the adrenal glands to produce aldosterone</p> Signup and view all the answers

    What is the primary function of the juxtaglomerular cells in the kidney?

    <p>Receiving information about decreased arterial blood pressure and increased levels of sodium ions in the filtrate</p> Signup and view all the answers

    How does the fetus adapt to the relatively low oxygen levels in the placenta?

    <p>By having hemoglobin with higher affinity for oxygen than adult hemoglobin</p> Signup and view all the answers

    What is the primary function of aldosterone in the nephron?

    <p>Regulating the reabsorption of sodium ions</p> Signup and view all the answers

    What is the effect of angiotensin II on peripheral blood vessels?

    <p>Vasoconstriction</p> Signup and view all the answers

    What is the primary function of the placenta in relation to the exchange of respiratory gases?

    <p>Regulating the exchange of oxygen and carbon dioxide between the maternal and fetal blood</p> Signup and view all the answers

    What is the primary factor regulating ventilation?

    <p>pCO2</p> Signup and view all the answers

    How does an increase in pCO2 affect nerve impulse frequency to inspiratory neurons?

    <p>It increases the frequency</p> Signup and view all the answers

    What percentage of the effect of pCO2 on ventilation is attributed to peripheral chemoreceptors?

    <p>40%</p> Signup and view all the answers

    What is the primary role of central chemosensors in regulating ventilation?

    <p>They sense changes in pH in the surrounding fluid</p> Signup and view all the answers

    What happens to pulmonary ventilation when pCO2 increases by 2-3 mmHg?

    <p>It doubles</p> Signup and view all the answers

    What is the importance of pO2 in regulating ventilation in normal circumstances?

    <p>It is not important</p> Signup and view all the answers

    What is the primary function of oxytocin in milk ejection?

    <p>To induce contraction of myoepithelial cells, leading to milk ejection</p> Signup and view all the answers

    Which type of receptors are sensitive to mechanical energy?

    <p>Mechanoreceptors</p> Signup and view all the answers

    What is the location of the receptors that sense cold?

    <p>Krause end bulbs in the outer layer of the dermis</p> Signup and view all the answers

    What is the role of prolactin in milk production?

    <p>To promote milk production in the mammary glands</p> Signup and view all the answers

    What happens to oxytocin secretion when epinephrine is released?

    <p>It is immediately stopped</p> Signup and view all the answers

    What is the effect of oxytocin on the excretory ducts?

    <p>It decreases their resistance</p> Signup and view all the answers

    What is the role of the sympathetic nerve fibers in milk ejection?

    <p>To regulate blood flow and contraction of teat sphincters</p> Signup and view all the answers

    How long does oxytocin secretion last?

    <p>For a few minutes</p> Signup and view all the answers

    What is the effect of oxytocin on the alveoli?

    <p>It increases the hydrostatic pressure</p> Signup and view all the answers

    What is the time frame for milk ejection to occur after initial stimulation?

    <p>60-90 seconds</p> Signup and view all the answers

    What type of receptors are sensitive to specific chemicals?

    <p>Chemoreceptors</p> Signup and view all the answers

    What is the function of the preBötzinger complex in the medulla oblongata?

    <p>Generation of respiratory rhythm</p> Signup and view all the answers

    What is the effect of a partial agonist on a receptor?

    <p>Partial activation of the receptor</p> Signup and view all the answers

    What is the function of the pneumotaxic center in the pons?

    <p>Regulation of inspiration and expiration</p> Signup and view all the answers

    What type of chemical signaling occurs when a cell secretes chemical messengers that affect surrounding cells of a different type?

    <p>Paracrine</p> Signup and view all the answers

    What is the function of the apneustic center in the pons?

    <p>Stimulation of inspiration and inhibition of expiration</p> Signup and view all the answers

    What is the effect of a full agonist on a receptor?

    <p>Full activation of the receptor</p> Signup and view all the answers

    What is the function of the hypothalamus in regulating respiration?

    <p>Regulation of autonomic functions</p> Signup and view all the answers

    What is the function of the limbic system in regulating respiration?

    <p>Regulation of emotional responses</p> Signup and view all the answers

    What is the function of the inverse agonist on a receptor?

    <p>Reduction of the receptor's constitutive activity</p> Signup and view all the answers

    What type of hormone is vasopressin?

    <p>Neurohormone</p> Signup and view all the answers

    What type of effect do hemocrine/endocrine hormones have?

    <p>Distant and systemic</p> Signup and view all the answers

    What is the role of bile acids in the process of fat absorption?

    <p>Emulsify fats</p> Signup and view all the answers

    What is the name of the system that produces tissue hormones?

    <p>Diffuse neuroendocrine system</p> Signup and view all the answers

    What is the primary function of the thyroid hormone?

    <p>Regulate metabolism</p> Signup and view all the answers

    What is the source of choline in the body?

    <p>Lecithin</p> Signup and view all the answers

    What type of hormones are neurotransmitters?

    <p>Neurocrine</p> Signup and view all the answers

    What is the primary function of prostaglandins?

    <p>Regulate inflammation</p> Signup and view all the answers

    What is the function of magnocellular neuron bodies?

    <p>Synthesize neurohormones</p> Signup and view all the answers

    What is the name of the hormone that regulates water reabsorption in the kidneys?

    <p>Vasopressin</p> Signup and view all the answers

    What is the primary function of secretin and cholecystokinin (CCK) in the regulation of bile secretion?

    <p>Stimulate the release of bile into the duodenum</p> Signup and view all the answers

    Study Notes

    Nephron and Kidney Function

    • The nephron is the basic structural and functional unit of the kidney.
    • There are two types of nephrons:
      • Cortical nephrons (80%): located primarily in the renal cortex, with short nephron loops that either dip into the superficial part of the renal medulla or never leave the cortex.
      • Juxtamedullary nephrons: located close to the boundary between the renal cortex and the renal medulla, with long nephron loops that burrow deeply into the renal medulla.

    Blood Circulation in the Kidneys

    • The kidneys receive about 20% of the cardiac output, with 90% going to the kidney cortex and 10% to the medulla.
    • The kidneys receive blood from the renal artery, which branches from the abdominal aorta.
    • The renal artery has a large diameter, few branches, and a short length, with pressure almost the same as in the aorta.

    Intestinal Juice

    • Intestinal juice has a pH of 7.5 and contains various enzymes, including:
      • Proteases (e.g., enterokinase, aminopeptidases, dipeptidases)
      • Lipases (e.g., lipase, alpha-amylase, lactase, sucrase)
      • Nucleases
    • Intestinal juice is produced by glands in the small intestine and plays a crucial role in chemical processing of food.
    • The small intestine contains around 10,000 glands per 1cm³.

    Blood Circulation

    • Blood circulation is provided by the heart, which pumps blood through the circulatory system.
    • There are two main circuits: the pulmonary circuit (right side of the heart to lungs to left side of the heart) and the systemic circuit (left side of the heart to the body to right side of the heart).
    • Blood flow is regulated by the heart, with capillaries supplying blood to tissues and veins regulating blood flow to the heart.

    Thyroid Hormones

    • Calcitonin (thyrocalcitonin) is produced by the thyroid gland and regulates calcium and phosphorus levels in the blood.
    • Triiodothyronine (T3) and thyroxine (T4) are produced by the thyroid gland and play a crucial role in cell metabolism.
    • T3 is more active than T4 and increases the intensity of cell metabolism, leading to increased ATP production.

    Mineralocorticoids

    • Mineralocorticoids, such as aldosterone, are produced in the zona glomerulosa of the adrenal gland cortex.
    • Aldosterone regulates the reabsorption of electrolytes (mainly Na+ and K+) from nephron tubules, which helps maintain blood pressure and pH.

    Carbohydrate Metabolism

    • Carbohydrates are an energy source, cell component, and necessary for muscle contractions and relaxation, as well as the action of the nervous system.
    • Carbohydrate metabolism involves the breakdown of carbohydrates into glucose, which is then absorbed into the bloodstream and used by the body.
    • Glycogen can be synthesized from glucose, glycerin, fatty acids, amino acids, and volatile fatty acids.

    Adrenal Glands and Hormones

    • The adrenal glands produce corticosteroids, which include mineralocorticoids (zona glomerulosa), glucocorticoids (zona fasciculata), and sex steroids (zona reticularis).
    • Aldosterone is the most active mineralocorticoid, regulating electrolyte reabsorption from nephron tubules.
    • Glucocorticoids, such as cortisol, stimulate glucose release from the liver, suppress allergic reactions, and reduce inflammation.

    Absorption in the Gastrointestinal Tract

    • Absorption is the transfer of substances from the GI tract to the blood or lymph through epithelial cells
    • Nutrients, water, inorganic salts, hormones, and drugs are absorbed
    • Factors affecting absorption:
      • Degree of nutrient splitting
      • Absorption surface area
      • Physical processes (filtration, osmosis, diffusion)
      • Active cellular processes involving epithelial cells
    • Protein absorption:
      • As amino acids
      • Phosphorylated by intestinal enzymes
      • Animal proteins are better absorbed
    • Carbohydrate absorption:
      • As monosaccharides (glucose, galactose)
      • In ruminants, glucose is absorbed in small amounts in the intestines
    • Fat absorption:
      • Mainly as glycerol and fatty acids
      • Only well-emulsified fats can be absorbed whole
      • Glycerol is well-absorbed due to its water solubility
      • Fatty acids are absorbed in complex with bile acid
    • Water and mineral absorption:
      • Most intense in the large intestine
      • Depends on osmotic pressure of food

    Physiological Meaning and Regulation of Protein Exchange

    • Proteins are necessary for:
      • Plastic processes (growth, development, tissue restoration)
      • Defense reactions (immune substances, antibodies)
      • Enzymes and hormone function
      • Transporting chemical substances (e.g., hemoglobin)
      • Energy source (4.1 kcal/g)
    • Cows receive 25% of their daily protein requirement from ruminal microorganisms
    • The value of proteins is determined by:
      • Presence of all essential amino acids
      • Mutual ratio of essential amino acids
    • Liver is essential for protein exchange, and impaired liver function can disrupt protein exchange
    • Growing animals and those in lactation require well-balanced food due to increased protein formation

    Cough and Sneezing Reflex

    • Coughing:
      • Similar to sneezing reflex, but with irritation of receptors in the respiratory tract
      • Reflex involves sensory nerve activation, brainstem processing, and motor neuron activation
      • Phases: inspiratory, compressive, and expiratory
    • Sneezing:
      • Occurs when irritant receptors in the nasal cavity are stimulated
      • Consists of nasal/sensitive phase and efferent/respiratory phase
      • Results in explosive exit of air through the mouth and nose

    Functions of the Spinal Cord

    • Functions:
      • Reflector function (associated with nerve centers in gray matter)
      • Conduction function (provides communication between CNS parts)
    • White matter:
      • Made of myelin (proteins and lipids) and axon bundles
      • Conducts, processes, and sends nerve signals up and down the spinal cord
      • Damage can affect movement, sensory faculties, and reflexes
    • Spinal shock:
      • Disappearance of reflexes regulated through the brain
      • Atony (lack of tone) and loss of sensations below the damaged area

    Brainstem

    • The brainstem consists of three parts: medulla oblongata, pons, and midbrain
    • Medulla oblongata:
      • Performs conduction and reflex functions
      • Centers for life support, defense reflexes, gastrointestinal regulation, and muscle tone regulation
    • Pons:
      • Regulates reflector movements and muscle tone
      • Acts as a conduction pathway between higher and lower brain centers
    • Midbrain:
      • Functions include vision, hearing, and precise motion regulation
      • Contains the reticular formation, responsible for nonspecific functions of the CNS

    Solutions and Osmolarity

    • Solutions are classified into three categories based on osmolarity: isotonic, hypertonic, and hypotonic
    • Isotonic solutions:
      • Have the same osmolarity as the cytoplasm of the cell
      • No net movement of water into or out of the cells
    • Hypertonic solutions:
      • Have a higher osmolarity than the cytoplasm of the cell
      • Water moves out of the cells, causing them to shrink or crenate
    • Hypotonic solutions:
      • Have a lower osmolarity than the cytoplasm of the cell
      • Water moves into the cells, causing them to swell and potentially burst (lyse)

    Gastric Juice Secretion

    • Gastric activity is divided into three stages: cephalic, gastric, and intestinal phases
    • Cephalic phase:
      • Responds to sight, taste, or thought of food
      • About 30% of total acid secretion occurs before food enters the stomach
      • Involves the nervous system and neurotransmitters such as acetylcholine
    • Gastric phase:
      • Occurs during eating and accounts for 50-60% of total gastric acid secretion
      • Involves direct contact of food with the stomach wall and the release of gastrin and histamine
    • Intestinal phase:
      • Occurs after eating and accounts for 5-10% of total gastric acid secretion
      • Involves signals from the small intestine about stretchiness, pH, and osmotic concentration

    Renal Functions and Hormones

    • Humoral regulation of renal functions involves the renin-angiotensin-aldosterone system (RAAS)
    • RAAS:
      • Primary function: maintaining systemic blood pressure
      • Secondary function: regulating glomerular filtration rate (GFR)
      • Impacts tubular reabsorption, electrolyte balance, and blood volume
    • Hormones involved:
      • Renin (enzyme)
      • Angiotensin (hormone)
      • Aldosterone (hormone)
      • ADH (antidiuretic hormone)
      • Parathormone and calcitonin (regulate blood Ca levels)

    Placental Transfer of Respiratory Gases

    • The placenta is responsible for transporting materials and heat between the blood of the fetus and the mother
    • Placental transfer occurs through diffusion and active transport
    • Transfer of oxygen is limited due to the reduction in maternal pO2 along the maternal blood vessels
    • Adaptations in the fetus include:
      • Higher affinity for O2 in fetal hemoglobin
      • Increased hemoglobin content in fetal blood
      • Higher cardiac output relative to body mass

    Phospholipids

    • Structure: glycerol + 2 fatty acids + phosphate group
    • Functions:
      • Structural components of cell membranes
      • Emulsifiers, bringing water and fat together
      • Involved in lipid absorption and transport
      • Prevent fatty liver
      • Form surfactant in lungs
      • Play a role in blood coagulation

    Regulation of Ventilation

    • pCO2 (CO2 partial pressure) is the most important factor regulating ventilation
    • Increased pCO2 leads to:
      • Deeper and more rapid breathing to normalize pCO2 levels
      • Increased nerve impulse frequency to inspiratory neurons
      • Increased H+ concentration, but H+ does not cross the blood-brain barrier
    • Both peripheral and central chemoreceptors are highly sensitive to pCO2 changes (pH changes)
    • Peripheral chemoreceptors have a 40% effect on ventilation in response to pCO2 changes
    • Central chemosensor responds to pH changes in the surrounding fluid, not directly to pCO2
    • A mere 2-3 mmHg increase in pCO2 doubles pulmonary ventilation

    Regulation of Ventilation by pO2

    • pO2 (O2 partial pressure) is monitored by peripheral chemoreceptors
    • In normal circumstances, pO2 is NOT important in regulating ventilation (a paradox, considering O2's importance to the body)
    • Arterial pO2 must fall significantly for pO2 to play a role in ventilation regulation

    Milk Ejection

    • Milk ejection occurs through the contraction of myoepithelial cells, which surround each individual alveolus and milk ducts.
    • The process is induced by a neuroendocrine reflex, which involves the stimulation of sensory nerve fibers in the teats, leading to the release of oxytocin from the posterior pituitary gland.
    • Oxytocin binds to receptors on myoepithelial cells, causing contraction and increasing hydrostatic pressure in the alveoli.
    • This contraction decreases the resistance of excretory ducts, relaxes the sphincter muscle in the teat canal, and allows milk to move from the alveoli down the ducts, resulting in milk ejection.
    • The entire process takes around 60-90 seconds from initial stimulation to milk ejection.
    • Oxytocin secretion lasts for a few minutes, and prolactin from the anterior pituitary gland promotes milk production in the mammary glands.
    • Oxytocin secretion can be stopped by epinephrine, which is released in response to stress, pain, fear, or anxiety.

    Types of Receptors

    • Receptors can be classified based on the type of irritation they perceive and their location.
    • Examples of receptors include:
      • Photoreceptors: sensitive to visible wavelengths of light, found in rods and cones in the retina.
      • Mechanoreceptors: sensitive to mechanical energy, found in touch receptors in the skin and baroreceptors in blood vessels.
      • Thermoreceptors: sensitive to heat and cold, found in Krause end bulbs and Ruffini endings in the skin.
      • Osmoreceptors: detect changes in the concentration of solutes in body fluids and changes in osmotic activity, found in cells in the supraoptic nucleus.
      • Chemoreceptors: sensitive to specific chemicals, found in smell and taste receptors, receptors in the blood for O2 and CO2 concentrations, and receptors for the chemical content of the digestive tract.
      • Nociceptors: pain receptors sensitive to tissue damage or distortion, found in the skin.
    • Agonists and antagonists are ligands that bind to receptors, causing a response or blocking the response, respectively.
    • Types of agonists and antagonists include:
      • Full agonists: activate receptors, producing a strong biological response.
      • Partial agonists: partially activate receptors, producing a partial response.
      • Antagonists: bind to receptors but do not activate them, blocking the response.
      • Inverse agonists: reduce the activity of receptors by inhibiting their constitutive activity.

    Centres of Respiration

    • The centres of respiration are located in the medulla oblongata, pons, hypothalamus, limbic system, and cerebral cortex.
    • The medulla oblongata contains inspiratory and expiratory neurons, which are inhibited by each other.
    • The preBötzinger complex, a cluster of interneurons in the medulla oblongata, generates the respiratory rhythm.
    • The spinal cord regulates respiratory muscles through cervical and thoracic motor neurons.
    • The pons regulates the change from inspiration to expiration, with the pneumotaxic and apneustic centers modulating the length of inspiration and expiration.
    • The hypothalamus regulates changes in respiration due to autonomic functions, such as thermoregulation and metabolism.
    • The limbic system regulates changes in respiration during different emotions and pain.
    • The cerebral cortex regulates conditioned reflexes.

    Chemical Signaling between Cells

    • Chemical signaling between cells can occur through autocrine, paracrine, endocrine, neurocrine, and neuroendocrine signaling.
    • Autocrine signaling: a cell secretes chemical messengers that stimulate the same cell or nearby cells of the same type.
    • Paracrine signaling: a cell secretes chemical messengers that affect surrounding cells of a different type.
    • Endocrine signaling: chemical messengers are secreted into the bloodstream by endocrine glands and cells, affecting distant cells.
    • Neurocrine signaling: neurotransmitters are secreted into a synaptic cleft, affecting adjacent neurons, muscles, or glandular cells.
    • Neuroendocrine signaling: hormone is released both locally and distantly, affecting both adjacent neurons and distant cells.

    Types of Hormones

    • Hormones can be classified based on their place of synthesis, including:
      • Classical hormones: synthesized in the cells of endocrine glands, secreted directly into the bloodstream.
      • Tissue hormones (parahormones): synthesized in various types of cells, including nerves, and secreted into the interstitial fluid.
      • Neurohormones: synthesized in neuroendocrine cells and secreted into the blood, synapses, or magnocellular bodies.

    Composition of Bile

    • Bile is composed of:
      • Bile acids (cholic acid, deoxycholic acid, etc.)
      • Mucin (mucus)
      • Bile pigments (bilirubin, biliverdin)
      • Cholesterol
      • Lecithin (phosphatidylcholine)
      • Fatty acids
    • Bile acids, cholesterol, and lecithin are the three major lipid constituents in bile.

    Function of Bile

    • Bile emulsifies fats, making them more accessible for lipase.
    • Bile mixes fatty acids with bile acids, forming a water-soluble complex that can be absorbed.
    • Bile activates lipase and inactivates gastric pepsin.
    • Bile promotes the absorption of lipid-soluble vitamins (D, E, K, A).
    • Bile neutralizes excess stomach acid before it enters the ileum.
    • Bile promotes intestinal peristalsis.
    • Bile acids inhibit the development of microbes in the intestines.

    Neurohumoral Regulation of Bile Secretion

    • Bile secretion is regulated by both neural and humoral mechanisms.
    • Humoral regulation: secretin and cholecystokinin (CCK) are stimulated by the presence of chyme in the duodenum, leading to the secretion of bile from the liver and the contraction of the gallbladder.
    • Neural regulation: parasympathetic nerves stimulate the excretion of bile, while sympathetic nerves inhibit it.

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