Physiology of Glandular tissues
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Questions and Answers

What is the primary method of communication used by the endocrine system?

  • Thermal signaling
  • Mechanical signaling
  • Chemical signaling (correct)
  • Electrical signaling

    • What is the main difference between neural and endocrine signaling?

  • Distance of signaling
  • Type of signal
  • Type of receptor
  • Speed of response (correct)

    • What is the role of neurotransmitters in neural signaling?

  • To transmit electrical signals
  • To stimulate muscle contraction
  • To bind with receptors on target cells (correct)
  • To amplify electrical signals

    • What is the function of hormones in the endocrine system?

    <p>To induce a characteristic response in target cells</p> Signup and view all the answers

    How do hormones travel through the body?

    <p>Through the bloodstream</p> Signup and view all the answers

    What is the approximate time it takes for target cells to respond to certain reproductive hormones?

    <p>Up to 48 hours</p> Signup and view all the answers

    What is the name of the response triggered by the release of adrenal hormones, such as epinephrine and norepinephrine?

    <p>Fight-or-flight response</p> Signup and view all the answers

    What type of tissue produces hormones?

    <p>Glandular tissue</p> Signup and view all the answers

    What is the primary function of liberins and statins in the body?

    <p>To stimulate or inhibit the release of other hormones</p> Signup and view all the answers

    What type of hormones are synthesized in neuroendocrine cells and secreted from nerve terminals directly into the blood?

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

    What is the main difference between neurotransmitters and neurotransmitters?

    <p>Neurotransmitters are secreted into a synaptic gap, while neurohormones are secreted into the bloodstream</p> Signup and view all the answers

    What is the primary function of prostaglandins in the body?

    <p>To have diverse hormone-like effects, including vasodilation and bronchodilation</p> Signup and view all the answers

    What category of hormones includes epinephrine and norepinephrine?

    <p>Amino acid-derived hormones</p> Signup and view all the answers

    What is the characteristic of steroid hormones?

    <p>They are lipid-soluble and insoluble in water</p> Signup and view all the answers

    What is the primary function of magnocellular neurons in the hypothalamus?

    <p>To synthesize and secrete antidiuretic hormone and oxytocin</p> Signup and view all the answers

    What is the primary difference between peptide hormones and lipid-derived hormones?

    <p>Peptide hormones are water-soluble, while lipid-derived hormones are lipid-soluble</p> Signup and view all the answers

    What is the primary function of glandular tissues?

    <p>To produce and release secretory products, such as sweat and hormones</p> Signup and view all the answers

    What is the primary difference between local mediators and hormones?

    <p>Local mediators are quickly degraded or removed, while hormones circulate throughout the body</p> Signup and view all the answers

    Which type of chemical signaling involves the release of a chemical messenger into the bloodstream, where it affects cells distant from its source?

    <p>Hemocrine or endocrine signaling</p> Signup and view all the answers

    What is the primary function of the endocrine system?

    <p>To produce and release hormones that affect cells distant from their source</p> Signup and view all the answers

    Which type of hormone is synthesized by cells of various tissues, including nerves, and has paracrine or autocrine effects?

    <p>Tissue hormones</p> Signup and view all the answers

    What is the primary difference between classical hormones and tissue hormones?

    <p>Classical hormones are synthesized by endocrine glands, while tissue hormones are synthesized by cells of various tissues</p> Signup and view all the answers

    What is the primary function of neurotransmitters released in the axo-vasal synapse?

    <p>To facilitate the transmission of nerve impulses</p> Signup and view all the answers

    Which type of chemical signaling involves the release of a chemical messenger that stimulates the cell that originally secreted it, and sometimes nearby cells of the same type?

    <p>Autocrine signaling</p> Signup and view all the answers

    What is the function of the thyroid-stimulating hormone (TSH) produced by the pituitary gland?

    <p>Stimulates thyroid hormone release</p> Signup and view all the answers

    What is the role of antidiuretic hormone (ADH) produced by the posterior pituitary gland?

    <p>Stimulates water reabsorption by kidneys</p> Signup and view all the answers

    What is the function of insulin produced by the pancreas?

    <p>Reduces blood glucose levels</p> Signup and view all the answers

    How are steroid and thyroid hormones transported in the blood?

    <p>Associated with various proteins</p> Signup and view all the answers

    What is the role of the receptor in hormone action?

    <p>To bind with the hormone molecule to produce an effect</p> Signup and view all the answers

    Which hormone is responsible for stimulating milk production in lactating females?

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

    What is the second messenger in hormone action?

    <p>Cyclic AMP</p> Signup and view all the answers

    How do steroid hormones enter the cell?

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

    What is the primary effect of a decrease in receptor numbers on the target cell's response?

    <p>Decreased maximal responsiveness</p> Signup and view all the answers

    Which type of hormone binds to intracellular receptors and activates transcription?

    <p>Thyroid hormones</p> Signup and view all the answers

    What is the result of adaptation or desensitization of receptors?

    <p>Decreased sensitivity of the target cell to the hormone</p> Signup and view all the answers

    What is the purpose of downregulation of receptors?

    <p>To allow cells to become less reactive to the hormone</p> Signup and view all the answers

    What is the effect of two hormones having a synergistic effect?

    <p>An amplified response</p> Signup and view all the answers

    How do steroid hormones circulate in the blood?

    <p>Bound to protein carriers</p> Signup and view all the answers

    What is the main organ responsible for the metabolism of steroids?

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

    What is the result of rebound in target cells?

    <p>Increased sensitivity of the target cell to the hormone</p> Signup and view all the answers

    What is the primary function of glandular tissues?

    <p>To respond to stimuli with a specific reaction: the production of a specific secretion</p> Signup and view all the answers

    Which type of glands have ducts and secrete to the surface?

    <p>Exocrine glands</p> Signup and view all the answers

    What is the primary difference between exocrine and endocrine glands?

    <p>Exocrine glands have ducts, while endocrine glands do not</p> Signup and view all the answers

    Which glands retain ducts to body surfaces?

    <p>Exocrine glands</p> Signup and view all the answers

    What is the primary function of ceruminous glands?

    <p>To produce cerumen</p> Signup and view all the answers

    What is the characteristic of glands that have both exocrine and endocrine parts?

    <p>They produce multiple secretions through both ducts and bloodstream</p> Signup and view all the answers

    What is the primary difference between compound and simple glands?

    <p>Compound glands have multiple branches, while simple glands do not</p> Signup and view all the answers

    What is the characteristic of tubuloacinar glands?

    <p>They have a mix of tubular and acinar structures</p> Signup and view all the answers

    What type of connection exists between the hypothalamus and the adenohypophysis?

    <p>Humoral connection</p> Signup and view all the answers

    What is the function of the neurohypophysis?

    <p>To store and secrete hormones produced by the hypothalamus</p> Signup and view all the answers

    Which type of neurons produce hormones in the hypothalamus?

    <p>Magnocellular neurons</p> Signup and view all the answers

    What is the function of the hypothalamic-hypophyseal portal system?

    <p>To coordinate the neural and humoral regulation of physiological functions</p> Signup and view all the answers

    What is the difference between the adenohypophysis and the neurohypophysis?

    <p>The adenohypophysis produces hormones, while the neurohypophysis stores and secretes them</p> Signup and view all the answers

    What is the function of the intermediate pituitary?

    <p>To produce melanotropic hormone</p> Signup and view all the answers

    What is the connection between the hypothalamus and the neurohypophysis?

    <p>Neural connection</p> Signup and view all the answers

    What type of hormones are produced by the cells of the adenohypophysis?

    <p>Tropic hormones</p> Signup and view all the answers

    What is the primary characteristic of holocrine secretion?

    <p>The whole cell disintegrates to release its secretion</p> Signup and view all the answers

    Which of the following glands is NOT a peripheral endocrine gland?

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

    What is the primary function of the hypothalamus?

    <p>To regulate and coordinate activity of various tissues and organs</p> Signup and view all the answers

    What is the term used to describe the concept that many organs house clusters of cells that secrete hormones?

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

    What is the primary function of liberins in the hypothalamus?

    <p>To stimulate the secretion of pituitary hormones</p> Signup and view all the answers

    What is the term used to describe glands that store their secretory products in a special chamber until stimulated to release them?

    <p>Neurohemal organs</p> Signup and view all the answers

    Which of the following types of glands releases its products through apocrine secretion?

    <p>Mammary glands</p> Signup and view all the answers

    What is the term used to describe the type of hormone produced by cells of various tissues, including nerves, and has paracrine or autocrine effects?

    <p>Tissue hormone</p> Signup and view all the answers

    What is the main function of antidiuretic hormone (ADH) produced by the neurohypophysis?

    <p>Decreases diuresis and stimulates water reabsorption in nephron tubules</p> Signup and view all the answers

    What is the role of oxytocin produced by the neurohypophysis?

    <p>Stimulates contractions of uterine smooth muscles and promotes milk letdown during lactation</p> Signup and view all the answers

    What is the main function of somatotropic hormone (STH) produced by the adenohypophysis?

    <p>Promotes protein synthesis and tissue formation</p> Signup and view all the answers

    What is the result of decreased somatotropic hormone (STH) production during the growth period?

    <p>Pituitary dwarfism</p> Signup and view all the answers

    What is the mechanism by which the body maintains hormone levels?

    <p>Negative feedback mechanism</p> Signup and view all the answers

    What is the role of the hypothalamus in regulating hormone production?

    <p>It regulates the secretion of tropic hormones through the secretion of peptide-releasing hormones</p> Signup and view all the answers

    What is the result of increased hormone concentrations in the blood?

    <p>Decreased production of peptide-releasing hormones</p> Signup and view all the answers

    What is an example of a positive feedback loop in the endocrine system?

    <p>The release of oxytocin during childbirth</p> Signup and view all the answers

    What is the result of excessive STH production in adults?

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

    What hormone regulates the growth of follicles in ovaries and stimulates spermatogenesis in testes?

    <p>Follicle stimulating hormone (FSH)</p> Signup and view all the answers

    What is the primary function of somatoliberin and somatostatin in the hypothalamus?

    <p>Controlling STH production</p> Signup and view all the answers

    What is the primary function of corticoliberin and corticostatin in the hypothalamus?

    <p>Regulating ACTH production</p> Signup and view all the answers

    What is the primary difference between pituitary dwarfism and pituitary giantism?

    <p>Hormone production rates</p> Signup and view all the answers

    What is the primary function of Luteotropic hormone (LTH) in females?

    <p>Stimulating progesterone synthesis</p> Signup and view all the answers

    What is the primary function of ACTH in the adrenal cortex?

    <p>Regulating glucocorticoid production</p> Signup and view all the answers

    What is the relationship between thyroliberin and TSH production?

    <p>Thyroliberin stimulates TSH production</p> Signup and view all the answers

    What is the primary factor that regulates the synthesis of mineralocorticoids?

    <p>Renin-angiotensin system</p> Signup and view all the answers

    What is the primary function of aldosterone?

    <p>Regulating electrolyte balance</p> Signup and view all the answers

    What is the primary stimulus for the release of renin from the juxtaglomerular apparatus?

    <p>Decreased blood pressure</p> Signup and view all the answers

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

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

    What is the primary regulator of aldosterone secretion in response to hyperkalemia?

    <p>Potassium levels</p> Signup and view all the answers

    What is the primary function of the zona glomerulosa?

    <p>Producing mineralocorticoids</p> Signup and view all the answers

    What is the primary substrate for steroid hormone synthesis in the adrenal cortex?

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

    What is the primary role of angiotensin-converting enzyme (ACE) in the renin-angiotensin system?

    <p>Converting angiotensin I to angiotensin II</p> Signup and view all the answers

    What is the primary cause of hypothyroidism due to problems with thyroid hormone production?

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

    What is the effect of reduced basic metabolism processes on the body?

    <p>Reduced heart rate and body temperature</p> Signup and view all the answers

    Which of the following foods is a rich source of iodine?

    <p>Cod liver</p> Signup and view all the answers

    What is the function of the adrenal cortex?

    <p>Produces aldosterone</p> Signup and view all the answers

    What is the characteristic of the adrenal glands?

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

    What is the effect of very low mental activity and slower reflexes on the body?

    <p>Reduced heart rate and body temperature</p> Signup and view all the answers

    What is the term for the accumulation of mucopolysaccharides in the skin, leading to non-pitting edema?

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

    What is the role of the zona glomerulosa in the adrenal cortex?

    <p>Produces mineralocorticoids</p> Signup and view all the answers

    What is the primary function of cortisol in the body during stress situations?

    <p>To stimulate the release of glucose from the liver and increase gluconeogenesis</p> Signup and view all the answers

    What is the primary function of calcitonin produced by the parafollicular cells of the thyroid gland?

    <p>Inhibit the activity of osteoclasts</p> Signup and view all the answers

    What is the effect of progesterone on the smooth muscle of the uterus during pregnancy?

    <p>It inhibits the effect of oxytocin on the smooth muscle of the uterus.</p> Signup and view all the answers

    Which of the following hormones is produced in the corpus luteum and is essential for pregnancy?

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

    What is the most common cause of goiter worldwide?

    <p>Iodine deficiency in the diet</p> Signup and view all the answers

    What is the primary function of the placenta during pregnancy?

    <p>It provides nutrition and oxygen to the embryo.</p> Signup and view all the answers

    What is the role of corticotropic hormone in the regulation of glucocorticoid secretion?

    <p>It stimulates the production of hormones in the zona fasciculata of the adrenal cortex</p> Signup and view all the answers

    Which of the following is a characteristic of steroid hormones?

    <p>They are lipid-soluble and can diffuse through the plasma membrane</p> Signup and view all the answers

    Which type of secretion is characteristic of pancreatic islets?

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

    What is the role of luteinizing hormone (LH) in the ovulation process?

    <p>It induces ovulation and stimulates the development of the corpus luteum.</p> Signup and view all the answers

    What is the effect of testosterone on the body?

    <p>It promotes the synthesis of protein and gain in skeletal muscle mass.</p> Signup and view all the answers

    What is the primary function of glucocorticoids in the body?

    <p>To regulate the metabolism of carbohydrates, proteins, and fats</p> Signup and view all the answers

    What is the result of an oversecretion of TSH in the thyroid gland?

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

    What is the role of parathyroid hormone (PTH) in the body?

    <p>It increases the concentration of calcium ions in the blood.</p> Signup and view all the answers

    What is the primary function of the parafollicular cells in the thyroid gland?

    <p>Regulate calcium levels</p> Signup and view all the answers

    Which of the following hormones is produced by the zona reticularis of the adrenal cortex?

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

    What is the role of the hypothalamus in the regulation of glucocorticoid secretion?

    <p>It produces corticoliberins that inhibit the production of hormones in the zona fasciculata of the adrenal cortex</p> Signup and view all the answers

    What is the effect of progesterone on the development of follicles in the ovaries?

    <p>It inhibits the development of follicles in the ovaries.</p> Signup and view all the answers

    What is the effect of a simple goiter on the thyroid gland?

    <p>Increase in thyroid tissue</p> Signup and view all the answers

    What is the primary function of the corpus luteum during pregnancy?

    <p>It produces progesterone to maintain pregnancy.</p> Signup and view all the answers

    What is the target organ of exocrine secretion from the pancreas?

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

    What is the primary function of estrogen hormones in the female body?

    <p>To stimulate the growth and development of the female gonads</p> Signup and view all the answers

    What is the primary difference between endocrine and exocrine glands?

    <p>Mode of secretion</p> Signup and view all the answers

    What is the role of the placenta in the second half of pregnancy?

    <p>It takes over the functions of the corpus luteum.</p> Signup and view all the answers

    What is the percentage of biological activity of proinsulin compared to insulin?

    <p>7-10%</p> Signup and view all the answers

    Where is insulin secreted from in the pancreas?

    <p>β-cells</p> Signup and view all the answers

    What is the function of amylin in the body?

    <p>Inhibits gastric emptying and promotes satiety</p> Signup and view all the answers

    How is glucose reabsorbed in the kidneys?

    <p>Active transport</p> Signup and view all the answers

    What is the role of C-peptide in the body?

    <p>Links the A and B chains of insulin</p> Signup and view all the answers

    What is the half-life of insulin in the blood?

    <p>5-6 minutes</p> Signup and view all the answers

    What is the function of GLUT2 in β-cells?

    <p>Uptakes glucose into the cell</p> Signup and view all the answers

    What is the ratio of amylin to insulin secretion?

    <p>1:100</p> Signup and view all the answers

    What is the effect of increased glucose concentrations on insulin secretion?

    <p>Increases insulin secretion</p> Signup and view all the answers

    What is the function of SGLT in the small intestine and kidneys?

    <p>Carries out active transport of glucose</p> Signup and view all the answers

    What is a characteristic of insulin-dependent tissues?

    <p>They require the hormone insulin to take up glucose into the cell</p> Signup and view all the answers

    What is the primary function of GLUT-4 transporters?

    <p>To respond to insulin and facilitate glucose uptake</p> Signup and view all the answers

    What happens to insulin synthesis and release after a meal?

    <p>It increases significantly, around 10-15 times</p> Signup and view all the answers

    In which type of tissues is glucose transported without insulin stimulation?

    <p>Non-insulin dependent tissues</p> Signup and view all the answers

    What is the effect of insulin on glucose metabolism?

    <p>It stimulates glucose uptake and metabolism</p> Signup and view all the answers

    What is the role of insulin receptors on cell membranes?

    <p>They change the permeability of the cell membrane for small molecules</p> Signup and view all the answers

    What is the primary function of GLUT-3 transporters?

    <p>To transport glucose in non-insulin dependent tissues</p> Signup and view all the answers

    What is the effect of insulin on glycogen synthesis?

    <p>It stimulates glycogen synthesis</p> Signup and view all the answers

    What percentage of cells in the pancreas are α cells?

    <p>25%</p> Signup and view all the answers

    What is the result of insulin binding to its receptor?

    <p>It starts many protein activation cascades</p> Signup and view all the answers

    What is the primary function of insulin in the body?

    <p>To stimulate glucose uptake and metabolism in cells</p> Signup and view all the answers

    What is the primary function of amylin, a hormone synthesized with insulin?

    <p>To inhibit food intake, delay gastric emptying, and decrease blood glucose levels</p> Signup and view all the answers

    What is the approximate diameter of an islet of Langerhans?

    <p>0.3 mm</p> Signup and view all the answers

    What is the primary target organ for the hormones produced by the endocrine part of the pancreas?

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

    What is the number of amino acids that make up insulin?

    <p>51</p> Signup and view all the answers

    Where is insulin synthesized in the cells of the islets of Langerhans?

    <p>Rough endoplasmic reticulum</p> Signup and view all the answers

    What is the function of somatostatin, a hormone produced by δ cells?

    <p>To inhibit the release of other hormones</p> Signup and view all the answers

    What is the primary function of pancreatic polypeptide, a hormone produced by PP cells?

    <p>To regulate the metabolism of proteins and fats</p> Signup and view all the answers

    What is the percentage of the pancreas that is made up of islets of Langerhans?

    <p>2-3%</p> Signup and view all the answers

    How long does it take for insulin to be produced in the β cells of the islets of Langerhans?

    <p>1 hour</p> Signup and view all the answers

    What is the primary reason for considering the sympathetic nervous system and the adrenal medulla as a single system?

    <p>They are functionally connected</p> Signup and view all the answers

    What type of glands are the liver and pancreas?

    <p>Both exocrine and endocrine</p> Signup and view all the answers

    What is the characteristic of unicellular glands?

    <p>Consist of one gland cell</p> Signup and view all the answers

    What is the primary function of glandular tissues?

    <p>Respond to stimuli with a specific reaction</p> Signup and view all the answers

    What is the difference between endocrine and exocrine glands?

    <p>Endocrine glands secrete hormones, exocrine glands secrete substances onto a surface</p> Signup and view all the answers

    What type of glands have ducts and secrete to the surface?

    <p>Exocrine glands</p> Signup and view all the answers

    What is the characteristic of multicellular glands?

    <p>Consist of a group of cells</p> Signup and view all the answers

    What is the name of the system that includes the sympathetic nervous system and the adrenal medulla?

    <p>Sympatho-adrenal system</p> Signup and view all the answers

    What is the primary difference between diffuse, central, and peripheral endocrine glands?

    <p>Their location in the body</p> Signup and view all the answers

    What is the characteristic of glands that have both exocrine and endocrine parts?

    <p>They have both exocrine and endocrine functions</p> Signup and view all the answers

    What is the primary function of ceruminous glands?

    <p>To produce cerumen, or earwax, to protect the ear</p> Signup and view all the answers

    What is the primary function of the lacrimal gland?

    <p>To produce tears to lubricate and protect the eyes</p> Signup and view all the answers

    What is the primary function of the Meibomian glands?

    <p>To produce an oily layer to stabilize the tear film</p> Signup and view all the answers

    What is the primary function of mammary glands?

    <p>To produce milk for newborn mammals</p> Signup and view all the answers

    What is the primary function of the orbicularis muscle?

    <p>To contract and relax to promote tear drainage</p> Signup and view all the answers

    What is the primary function of the tear film?

    <p>To refract light and focus images on the retina</p> Signup and view all the answers

    What is the primary function of the conjunctival goblet cells?

    <p>To produce mucin to form and bind the tear film to the cornea</p> Signup and view all the answers

    What is the primary function of the lacrimal sac?

    <p>To drain tears from the eye into the nasal cavity</p> Signup and view all the answers

    What is the primary function of the ductus nasolacrimalis?

    <p>To drain tears from the lacrimal sac into the nasal cavity</p> Signup and view all the answers

    What is the primary function of the mammary gland during lactation?

    <p>To produce milk for newborn mammals</p> Signup and view all the answers

    What is the primary function of oxytocin in lactation?

    <p>Stimulates milk release and ejection from the udder</p> Signup and view all the answers

    What is the composition of milk sugar (lactose) formed in the alveoli?

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

    What is the function of the sphincters of the teat canal in milk ejection?

    <p>Controls the active ejection of milk</p> Signup and view all the answers

    How does stress affect oxytocin levels?

    <p>Decreases oxytocin levels</p> Signup and view all the answers

    What is the function of salivary amylase in saliva?

    <p>Breaks down starch</p> Signup and view all the answers

    What is the main component of saliva?

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

    What is the function of lactoferrin in saliva?

    <p>Protects against microorganisms</p> Signup and view all the answers

    What is the primary function of prolactin in lactation?

    <p>Keeps milk secretion at a certain level</p> Signup and view all the answers

    What is the result of the neural regulation of milk ejection?

    <p>Stimulates milk ejection</p> Signup and view all the answers

    What is the function of the tuboalveolar glands in milk synthesis?

    <p>Secretes milk</p> Signup and view all the answers

    What is the primary characteristic of mucous cells?

    <p>They produce mucin that dissolves in water</p> Signup and view all the answers

    What is the main difference between merocrine, apocrine, and holocrine secretion?

    <p>The method of excretion</p> Signup and view all the answers

    What is the function of the glandular portion of an exocrine gland?

    <p>To produce and secrete substances</p> Signup and view all the answers

    What is the characteristic of a branched gland?

    <p>The glandular portion branches</p> Signup and view all the answers

    What is the primary function of sebaceous glands?

    <p>To produce sebum</p> Signup and view all the answers

    What is the characteristic of a mixed gland?

    <p>It produces both mucin and serous secretions</p> Signup and view all the answers

    What is the primary function of atrichial sweat glands?

    <p>To regulate body temperature</p> Signup and view all the answers

    What is the function of the clear cells in the secretory part of the sweat gland?

    <p>To actively transport sodium to the lumen of the gland</p> Signup and view all the answers

    What is the primary function of the excretory part of the sweat gland?

    <p>To reabsorb sodium and potassium into the blood</p> Signup and view all the answers

    What is the characteristic of the secretion produced by epitrachial sweat glands?

    <p>It is oily and does not evaporate easily</p> Signup and view all the answers

    Which neurotransmitter stimulates the secretion of thick, protein-rich saliva?

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

    What is the primary component of sebum secretion from sebaceous glands?

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

    What is the effect of testosterone on sebaceous glands?

    <p>Increases sebum secretion</p> Signup and view all the answers

    What type of glands are sebaceous glands?

    <p>Holocrine glands</p> Signup and view all the answers

    What is the function of sebum secretion on the skin?

    <p>Maintains skin elasticity</p> Signup and view all the answers

    What percentage of net energy from intake is required for lactation in a dairy cow?

    <p>80%</p> Signup and view all the answers

    How many liters of blood flow through the udder for every liter of milk produced in cows?

    <p>400-500 L</p> Signup and view all the answers

    What is the result of abrupt weaning in intensively managed production animals?

    <p>Involution begins after 1-2 days of not emptying the udder</p> Signup and view all the answers

    What type of cells continue to proliferate during the first part of lactation in cows?

    <p>Secretory epithelial cells</p> Signup and view all the answers

    What is the source of blood supply to the mammary gland?

    <p>Caudal aorta</p> Signup and view all the answers

    What is the primary function of the sebaceous gland in birds?

    <p>To help maintain the integrity of feathers and repel water</p> Signup and view all the answers

    What is the role of myoepithelial cells in the mammary gland?

    <p>To surround each individual alveolus and milk ducts, facilitating milk ejection</p> Signup and view all the answers

    What is the function of lanolin in sheep?

    <p>To make coats water-repellent</p> Signup and view all the answers

    What is the structure of the mammary gland in cattle?

    <p>Each udder has four mammary glands, with each gland having separate glandular tissue, milk collection system, and teat</p> Signup and view all the answers

    What percentage of cardiac output is taken up by mammary blood flow at high production?

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

    What is the function of suint in sheep?

    <p>Sheep sweat, making wool greasy</p> Signup and view all the answers

    Which hormone induces growth of secretory epithelial cells in the udder?

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

    What is the term for the rate of decrease in daily milk yield after peak production throughout the remainder of lactation?

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

    What is the name of the protein that inhibits milk synthesis and is secreted by mammary epithelial cells?

    <p>Feedback Inhibitor of Lactation (FIL)</p> Signup and view all the answers

    What is the effect of not milking an animal regularly on milk production?

    <p>Decreases milk production due to feedback inhibition</p> Signup and view all the answers

    What is the primary difference between colostrum and regular milk?

    <p>Colostrum has a higher fat and protein concentration than regular milk.</p> Signup and view all the answers

    What is the approximate time frame during which newborns can absorb immunoglobulins from colostrum?

    <p>6 hours</p> Signup and view all the answers

    What is the primary function of immunoglobulins in colostrum?

    <p>To protect against environmental microorganisms</p> Signup and view all the answers

    What is the primary factor that determines the fat content of milk in an individual cow?

    <p>Breed of cow</p> Signup and view all the answers

    What is the result of not receiving colostrum in young animals?

    <p>They grow more slowly and not to their full potential</p> Signup and view all the answers

    What is the main determinant of the amount of milk secreted in a cow?

    <p>Lactose concentration</p> Signup and view all the answers

    Which of the following factors does not influence the fat content of milk in cows?

    <p>Protein deficiency</p> Signup and view all the answers

    What is the primary function of milk fat in marine mammals?

    <p>To build up blubber, a heat-insulating layer of fat</p> Signup and view all the answers

    What is the relationship between lactose and ion concentration in milk?

    <p>They are inversely proportional</p> Signup and view all the answers

    What is the effect of underfeeding on the solids-not-fat content of milk in cows?

    <p>It decreases the solids-not-fat content</p> Signup and view all the answers

    What is the primary mechanism that regulates lactation in dairy cows?

    <p>Pressure in alveoli after suckling</p> Signup and view all the answers

    What is the term for the coordinated redirection of metabolic resources during lactation?

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

    What is the primary function of PRL in pigeons and doves?

    <p>Regulation of 'pigeon milk' production</p> Signup and view all the answers

    What is the consequence of not emptying the udder completely in dairy cows?

    <p>Involution of secretory tissue</p> Signup and view all the answers

    What is the role of leptin and placental lactogen during pregnancy?

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

    What is the primary function of the milk ejection reflex?

    <p>To induce the emptying of mammary glands</p> Signup and view all the answers

    What is the effect of sympathetic activation on milk let-down?

    <p>It inhibits the response of myoepithelial cells to oxytocin</p> Signup and view all the answers

    What is the characteristic of the lactation curve?

    <p>It reaches a peak production around lactation days 40–50</p> Signup and view all the answers

    What is the effect of anxiety or pain on milk let-down?

    <p>It inhibits the response of myoepithelial cells to oxytocin</p> Signup and view all the answers

    What is the difference between the milk ejection mechanism in calves and goat kids?

    <p>Calves mimic the process of machine milking, while goat kids mimic the process of hand milking</p> Signup and view all the answers

    Study Notes

    Here are the study notes for the text:

    Types of Intercellular Communication

    • The nervous system uses two types of intercellular communication: electrical and chemical signaling.
    • Electrical signaling involves direct action of an electrical potential, while chemical signaling involves neurotransmitters such as serotonin and norepinephrine.

    Endocrine System

    • The endocrine system uses chemical signaling to send messages throughout the body.
    • Hormones are secreted by endocrine glands into the extracellular fluid, where they bind to receptors on target cells.
    • Hormone signaling requires more time than neural signaling to prompt a response in target cells.
    • Hormones are produced by glandular tissue, which also produces other secretory products such as sweat, saliva, and digestive enzymes.

    Types of Chemical Signaling

    • Autocrine signaling: a chemical messenger stimulates the cell that originally secreted it, and sometimes nearby cells of the same type.
    • Paracrine signaling: a chemical messenger acts locally on nearby cells of a different type.
    • Hemocrine or endocrine signaling: a chemical messenger is secreted into the bloodstream and affects cells that are distant from its source.
    • Neurocrine signaling: a chemical messenger is released locally in a synaptic gap, and activates an adjacent cell.
    • Neuroendocrine signaling: a hormone is released both locally and distantly.

    Classification of Hormones

    • Hormones can be classified into three types based on their chemical structure: amino acid-derived, peptide, and lipid-derived.
    • Amino acid-derived hormones are derived from the amino acids tryptophan and tyrosine, and have names that end in "-ine".
    • Peptide hormones are composed of polypeptide chains, and include molecules that are short polypeptide chains, small proteins, and large glycoproteins.
    • Lipid-derived hormones are derived from cholesterol, and include steroid hormones such as testosterone and estrogen.

    Endocrine Glands and Their Hormones

    • The pituitary gland produces several hormones, including growth hormone, prolactin, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, and luteinizing hormone.
    • The thyroid gland produces thyroxine and triiodothyronine, which stimulate basal metabolic rate.
    • The parathyroid gland produces parathyroid hormone, which increases blood calcium levels.
    • The adrenal gland produces several hormones, including aldosterone, cortisol, and epinephrine.

    Transport of Hormones in the Blood

    • Protein and peptide hormones are transported in the plasma in dissolved form.
    • Steroid and thyroid hormones are transported in the blood through association with various types of proteins.
    • Carrier proteins have high affinity for specific hormones, but low capacity due to low plasma concentration.
    • Albumins have low affinity for steroid hormones, but high capacity due to high plasma concentration.

    Hormone Receptors

    • Hormone receptors are present on cells in much greater numbers than required for eliciting a biological response.
    • Hormone receptors can be present on the cell membrane or embedded in the cell membrane.
    • Lipid-soluble hormones bind to intracellular receptors to activate transcription, resulting in a slow response.
    • Plasma-soluble hormones bind to cell surface receptors, which activate a second messenger, resulting in a rapid response.

    Factors Affecting Target Cell Response

    • Presence of a significant level of a hormone can cause target cells to decrease their number of receptors (downregulation).
    • Prolonged absence of a hormone can cause target cells to increase their number of receptors (upregulation).
    • Hormones can interact with each other to affect the response of cells, through permissive, synergistic, or antagonistic effects.

    Metabolism of Hormones

    • Peptide hormones are degraded by the liver and cleared by the kidney with half-lives of a few minutes.
    • Steroid hormones and thyroid hormone circulate bound to protein carriers, which extends their half-life in the blood.
    • Metabolism of steroids involves reduction, followed by conjugation with sulfates and glucuronides, allowing them to be excreted in urine.

    Glandular Tissues

    • Glandular tissues are excitable tissues that respond to stimuli with a specific reaction – the production of a specific secretion.
    • Glands are divided into two main categories:
      • Exocrine glands: have ducts and secrete to the surface (e.g., sebaceous and sweat glands, salivary glands)
      • Endocrine glands: do not have ducts; their secretions (hormones) are secreted into the bloodstream

    Exocrine Glands

    • Retain ducts to body surfaces
    • Examples:
      • Sweat glands (sweat)
      • Ceruminous glands (cerumen)
      • Salivary glands (saliva)
      • Mammary glands (milk)
      • Lacrimal glands (tears)
      • Sebaceous glands (sebum)
      • Liver and pancreas (exocrine part)

    Endocrine Glands

    • Divided into three categories based on localization:
      • Peripheral endocrine glands
      • Diffuse endocrine glands
      • Central endocrine glands

    Peripheral Endocrine Glands

    • Anatomical formations whose basic function is the synthesis and secretion of hormones into the blood
    • Examples:
      • Thyroid gland (T3, T4)
      • Parathyroid glands (parathormone - PTH)
      • Thymus (thymosin and other hormones that stimulate the development of T lymphocytes)
      • Gonads (testes and ovaries)
      • Adrenal glands (cortex and medulla)
      • Pancreas (endocrine part - Islets of Langerhans)

    Diffuse Neuroendocrine Glands

    • Include neuroendocrine cells scattered throughout the body that synthesize and secrete hormones
    • Examples:
      • Cells of adrenal gland medulla
      • Enterochromaffin cells
      • Thyroid gland C cells
      • Hypophysis endocrine cells
      • Pancreas endocrine cells

    Central Endocrine Glands (Neurohemal Organs)

    • Store their secretory products (neurohormones) in a special chamber until stimulated to release it by a signal from the nervous system
    • Examples:
      • Hypothalamus
      • Hypophysis (pituitary gland)
      • Epiphysis

    Hypothalamus

    • Link between the nervous and endocrine systems
    • Receives information about the internal and external environment of the body
    • Regulates and coordinates activity of various tissues and organs
    • Produces:
      • Vasopressin (antidiuretic hormone, ADH)
      • Oxytocin
      • Liberins (stimulating hormones)
      • Statins (inhibiting hormones)

    Hypophysis (Pituitary Gland)

    • Composed of three parts:
      • Adenohypophysis (anterior pituitary): secretes tropic hormones that regulate the action of several peripheral endocrine glands
      • Intermediate pituitary (pars intermedia): produces melanotropic hormone (melanocyte stimulating hormone)
      • Neurohypophysis (posterior pituitary): stores and secretes hormones produced by the hypothalamus (oxytocin and vasopressin)

    Hypothalamic-Hypophyseal System

    • Connection between the hypothalamus and the hypophysis
    • Humoral connection: blood flows from the hypothalamus to the adenohypophysis, transporting liberins and statins
    • Neural connection: axonal transport of hormones from the hypothalamus to the neurohypophysis

    Hypothyroidism

    • Occurs due to problems with thyroid hormone production (iodine deficiency, tumor, or atrophy of thyroid follicular cells)
    • Can also occur due to failure of the hypothalamus to secrete TRH or failure of the adenohypophysis to secrete TSH
    • Characteristics:
      • Reduced basic metabolism processes
      • Lowered body temperature
      • Reduced heart rate
      • Weight gain
      • Hair loss and changes in skin and hair color
      • Prone to skin infections
      • Reduced libido and infertility
      • Very low mental activity and slower reflexes
      • Can lead to myxedema or mucus edema

    Iodine Sources

    • Found in food:
      • Sea cabbages
      • Cod liver
      • Shrimps
      • Milk
      • Eggs
      • Prunes (dried plums)
      • Cranberries
      • Strawberries
      • White bread
      • Rhubarb

    Adrenal Glands

    • Consists of two independent secretion glands:
      • Adrenal medulla (modified ganglion of the sympathetic nervous system)
      • Adrenal cortex (three parts from histology)
    • Each part has a separate blood supply and innervation
    • Adrenal cortex part is necessary for life-support, especially mineralocorticoid aldosterone

    Corticosteroids

    • Produced in the adrenal cortex
    • Types:
      • Mineralocorticoids (zona glomerulosa)
      • Glucocorticoids (zona fasciculata)
      • Sex steroids (zona reticularis)
    • Regulation of synthesis:
      • Under the influence of the adenohypophysis (ACTH)

    Zona Glomerulosa

    • Produces mineralocorticoids (aldosterone and deoxycorticosterone)
    • Absolutely necessary for life-support
    • Regulates the reabsorption of electrolytes (mainly Na+ and K+) from the nephron tubules
    • Aldosterone secretion is regulated by:
      • Renin-angiotensin system
      • Blood potassium concentration
      • Blood sodium level
      • ACTH stimulation

    Zona Fasciculata

    • Produces glucocorticoids (cortisol and corticosterone)
    • Stimulate the release of glucose from the liver into the blood and gluconeogenesis
    • Suppress allergic reactions in the body
    • Suppress inflammatory reactions
    • Reduce the number of eosinophils
    • Increase the body's resistance to harmful effects
    • Increase gastric hydrochloric acid secretion

    Zona Reticularis

    • Produces androgens (male), estrogens (female), and progesterone (female)
    • Important for animals (and humans) until reaching sexual maturity
    • Hyperfunction contributes to the onset of sexual maturity, including premature puberty

    Gonads

    • Produce gametes and sex hormones
    • Sex hormones:
      • Estrogens (female)
      • Androgens (male)
    • Regulation of gonadal hormones:
      • By gonadotropic hormones of the adenohypophysis (FSH, LH, LTH)

    Female Sex Hormones

    • Produced in ovaries and placenta
    • Types:
      • Estrogens (estradiol and estrone)
      • Progesterone
    • Functions:
      • Stimulate the growth and development of female gonads
      • Stimulate the growth and development of genital organs
      • Promote the proliferation of the uterine mucosa
      • Inhibit the development of atherosclerosis in blood vessels

    Male Sex Hormones

    • Produced in testicular interstitial Leydig cells
    • Types:
      • Testosterone
      • Androsterone
    • Functions:
      • Stimulate protein synthesis and body weight gain
      • Stimulate the growth, development, and functions of genital organs
      • Determine the expression of sexual instinct

    Endocrine Glands Independent of the Hypothalamo-Hypophyseal System

    • Parathyroid glands (PTH)
    • Thyroid gland C cells (calcitonin)
    • Pancreas (insulin, glucagon)
    • Thymus (thymosin)
    • Adrenal medulla (epinephrine, norepinephrine)

    Pancreatic Hormones

    • The pancreas has four types of cells: α cells (~25%), β cells (~60%), δ cells (~10%), and PP cells.
    • These cells produce hormones that regulate glucose levels in the blood.

    Insulin and Glucagon

    • α cells produce glucagon, which increases blood glucose levels.
    • β cells produce insulin, which decreases blood glucose levels.
    • Insulin is a polypeptide formed from 51 amino acids and is synthesized in the rough endoplasmic reticulum.
    • Insulin is essential for life and affects carbohydrate, protein, and fat metabolism.

    Insulin Synthesis and Secretion

    • Insulin is synthesized as preproinsulin in the ribosomes, then cleaved to proinsulin in the Golgi apparatus.
    • Proinsulin is cleaved into equimolar amounts of insulin and C-peptide in the secretory granules.
    • Insulin is released into the blood when blood glucose is elevated, and β-cells uptake glucose through facilitated diffusion.
    • Insulin release is regulated by the concentration of glucose in the blood.

    Regulation of Insulin Secretion

    • When blood glucose is elevated, β-cells uptake glucose, and the concentration of ATP increases, closing K ion channels and causing depolarization.
    • This leads to the opening of Ca ion channels, breakdown of insulin and C-peptide granules, and release of insulin and C-peptide into the blood.
    • In normoglycemia, insulin is secreted minimally, but along with insulin and C-peptide, β-cells also secrete amylin, which inhibits gastric emptying and promotes satiety.

    Glucose Transport

    • Glucose is transported from the small intestine and kidneys into the blood through active transport and facilitated diffusion.
    • Glucose transport in insulin-dependent tissues (myocytes, adipocytes, and cardiomyocytes) requires insulin to bind to insulin receptors and change the permeability of the cell membrane.
    • Insulin stimulates the entry of glucose into cells and promotes its intracellular metabolism, activates lipogenesis, and stimulates glycogen production in muscles.

    Effect of Eating on Insulin Secretion

    • Between meals, the concentration of glucose in the blood and β-cells is low, and insulin secretion is minimal.
    • After a meal, glucose concentration increases, and insulin synthesis and release increase, ensuring glucose transport and use in insulin-dependent tissues.
    • In non-insulin dependent tissues, such as nervous tissue, glucose is transported by GLUT-3 transport-proteins without insulin receptor stimulation.

    Sympatho-Adrenal System (SAS)

    • The sympathetic nervous system and the adrenal medulla are connected anatomically and functionally, forming a single SAS.
    • The SAS regulates the production of epinephrine and norepinephrine, which are stimulated by the sympathetic nervous system.

    Glands

    • Glands are classified into two types: endocrine and exocrine.
    • Endocrine glands produce hormones that are secreted directly into the bloodstream.
    • Exocrine glands produce secretions that are released through a duct or tube.

    Exocrine Glands

    • Types of exocrine glands:
      • Unicellular (e.g., goblet cells, mucous cells)
      • Multicellular (e.g., submandibular gland)
    • Exocrine glands have a glandular portion and a duct portion, which can be classified as simple or compound.
    • Modes of exocrine secretion:
      • Merocrine secretion (e.g., pancreatic acinar cells)
      • Apocrine secretion (e.g., mammary glands)
      • Holocrine secretion (e.g., sebaceous glands)

    Sweat Glands

    • Types of sweat glands:
      • Atrichial (formerly Eccrine) - found in the skin, functions in thermoregulation and excretion
      • Epitrichial (formerly Apocrine) - found in the armpits and around the anus, functions in releasing pheromones
    • Sweat gland structure:
      • Secretory part (tubular, twisted into a ball, wrapped around by blood capillaries)
      • Excretory part (tubular, straight part)

    Ceruminous Glands

    • Specialized sweat glands located in the external auditory canal
    • Produce cerumen (earwax) by mixing their secretion with sebum and dead epidermal cells
    • Functions of cerumen:
      • Keeps the eardrum pliable
      • Lubricates and cleans the external auditory canal
      • Waterproofs the canal
      • Kills bacteria and traps foreign particles

    Lacrimal Glands

    • Produce tears, which have multiple functions:
      • Forms the watery part of the tear film
      • Cleanses the eyes
      • Moisturizes and lubricates the eyes
      • Rinses off allergens and irritants
      • Protects the surface of the eye against infections
    • Tear film composition:
      • Oil layer (Meibomian glands)
      • Watery layer (tear gland)
      • Mucous layer (conjunctival goblet cells)

    Mammary Glands

    • Produce milk for the survival of newborn mammals
    • Milk composition:
      • Casein (protein)
      • Lactose (carbohydrate)
      • Fat
      • Vitamins
      • Calcium
    • Modes of milk secretion:
      • Apocrine at the beginning of secretions
      • Merocrine during intense lactation
      • Holocrine at the end of the lactation period
    • Regulation of milk production:
      • Neural regulation (afferent part) induced by massage or other stimuli
      • Humoral regulation influenced by metabolic and stress hormones, directly by oxytocin and prolactin

    Salivary Glands

    • Types of salivary glands:
      • Large glands (sublingual, mandibular, parotid, zygomatic)
      • Small glands scattered throughout the oral cavity
    • Saliva composition:
      • 99% water and 1% solids
      • Viscosity determined by mucin, glycoproteins, and other proline-containing proteins
      • Inorganic compounds (e.g., potassium, sodium, calcium, magnesium)
      • Metabolic end products (e.g., CO2, carbonic acid salts, urea)
      • Enzymes (e.g., ptyalin, salivary amylase)
    • Functions of saliva:
      • Evaluates food
      • Aids in swallowing
      • Cleans the oral cavity
      • Protects against microorganisms
      • Protects against irritating substances
      • Participates in urea circulation (for ruminants)
      • Participates in thermoregulation

    Regulation of Saliva Secretion

    • Saliva secretion is regulated by the autonomic nervous system
    • Both cholinergic and adrenergic neurotransmitters can stimulate the secretion of thick, protein-rich saliva
      • Cholinergic receptors (M-cholinergic) stimulate saliva secretion through Ca ion channels
      • Adrenergic receptors (α-adrenergic) stimulate saliva secretion through Ca ion channels
      • Adrenergic receptors (β-adrenergic) stimulate saliva secretion through cAMP

    Sebaceous Glands

    • Compound alveolar glands located in the dermis and open at the root of the hair
    • Holocrine glands that secrete an oily substance called sebum
    • Sebum secretion is stimulated by testosterone
    • Increases during puberty
    • Sebum consists mainly of triglycerides, cholesterol, esters, and other substances
    • Forms a slightly oily film on the skin, keeping it elastic and preventing water loss

    Physiology of Lactation

    • Lactation is the combined process of milk secretion and milk removal
    • Mammary gland structure:
      • Alveoli (acini): basic functional units
      • Lobules: clusters of alveoli
      • Lobes: collections of lobules
    • Milk synthesis and secretion:
      • Alveolar cells produce milk
      • Myoepithelial cells contract to release milk
      • Milk letdown: oxytocin stimulates milk ejection
    • Udder anatomy and blood flow:
      • Blood supply essential for mammary function
      • 500 liters of blood pass through the udder to produce 1 liter of milk
    • Mammary gland development:
      • Rapid growth during fetal life, puberty, and pregnancy
      • Estrogen, progesterone, and prolactin stimulate growth and differentiation of secretory tissue

    Lactation Performance

    • Lactation curve: milk production increases to a peak and then decreases
    • Maintenance of lactation:
      • Hormonal control of lactation: prolactin, oxytocin, and other hormones
      • Frequent milking or suckling stimulates milk production
    • Milk composition:
      • Colostrum: high in fat, proteins, minerals, and vitamins; low in lactose
      • Regular milk: changes in composition throughout lactation
    • Factors affecting milk composition:
      • Genetic factors
      • Interval between milkings
      • Stage of lactation
      • Age of the cow
      • Feeding regime
      • Disease
      • Completeness of milking### Milk Composition and Lactation
    • Milk fat in marine mammals is used to build up blubber, a heat insulating layer of fat.
    • In cows, lactose and dissolved ions make up most of the osmolarity, with 50% represented by lactose.
    • Lactose and ion concentration are negatively correlated, meaning that if there is more lactose, there will be less ions.
    • Lactose is the main determinant of the amount of milk secreted.
    • Milk also contains vitamins, trace elements, and hormones needed by offspring.
    • Milk composition is a factor that regulates growth rate, with faster-growing species having higher protein and mineral content in their milk.

    Milk Ejection

    • Milk ejection is the contraction of myoepithelial cells, which increases hydrostatic pressure in the alveoli.
    • Teats have a high density of sensory nerve fibers, and sympathetic nerve fibers help regulate blood flow and contraction of teat sphincters.
    • The mammary epithelial cells are not affected by the autonomic nervous system, but milk ejection is.
    • When myoepithelial cells are relaxed, most of the secreted milk remains in the alveoli.
    • During milking and suckling, myoepithelial cells contract and force milk from the alveoli into the excretory ducts.

    Milk Ejection Reflex

    • The milk ejection reflex is a neuroendocrine reflex that induces the emptying of mammary glands.
    • The reflex is elicited by sensations on the udder and teats, which send nerve impulses to the CNS.
    • Oxytocin is released from the posterior pituitary, binds to receptors on myoepithelial cells, and induces contraction.
    • The contraction increases hydrostatic pressure in the alveoli, decreases resistance of the excretory ducts, and relaxes the sphincter muscle in the teat canal.
    • It takes 60-90 seconds from initial stimulation to milk ejection, and oxytocin secretion lasts for a few minutes.

    Lactation Curves

    • Milk production increases in the early post-partum period, reaches a peak, and declines steadily.
    • This is called a lactation curve.
    • In dairy cows, peak lactation is usually 4-6 weeks after calving and declines until 40 weeks after calving.
    • Some goats can start lactating in the absence of pregnancy.
    • The lactation curve is influenced by factors such as genetic potential, feeding, milking regimes, and feeding regimes.

    Metabolism during Lactation

    • During lactation, uptake of glucose and amino acids in the udder and uterus is prioritized over other organs.
    • Additional energy stores are taken from adipose and muscle tissue.
    • Glucose utilization in other tissues is reduced, and amino acids are used for milk protein synthesis, with muscle proteins broken down and utilized.
    • Homeorhesis, a coordinated redirection of metabolic resources, is regulated by hormones such as leptin, placental lactogen, PRL, and GH.

    Pigeon Milk

    • Pigeons and doves produce a milk-like substance, secreted by epithelial cells in the crop.
    • The substance has a high protein and fat content, and contains IgA and some bacteria.
    • It has a yellow cottage-cheese-like consistency and is regulated by PRL, similar to mammals.
    • This is essentially bird lactation!

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    This quiz covers the physiology of neural signaling, including electrical and chemical signaling, neurotransmitters, and their role in intercellular communication.

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