Human anatomy: Endocrine System Module 7

Define the term; hormone

Hormones are chemical messengers, A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.

Describe the organs that are affected by diabetes mellitus

Organ/tissue responses to Insulin deficiency: adipose tissue & muscle -Decreased glucose uptake and utilisation Organ/tissue responses to Insulin deficiency: Liver -glycogenolysis Organ/tissue responses to Insulin deficiency: liver & muscle -protein catabolism and gluconeogenesis Resulting condition In blood -Hyperglycemia Resulting condition In blood -Glycosuria -Osmotic diuresis signs and symptoms -Polyuria (and dehydration, soft eyeballs) -Polydipsia (and fatigue, weight loss) -Polyphagia Organ/ tissues involved: liver and adipose tissue Organ/tissue responses to Insulin deficiency: Lipolysis and ketogenesis Resulting condition in blood -Lipidemia and ketoacidosis Resulting condition in urine -Ketonuria Loss of Na+, K+; electrolyte and acid-base imbalances signs and symptoms Acetone breath Hyperpnea Nausea, vomiting, abdominal pain Cardiac irregularities Central nervous system depression; coma

Discuss the adrenal gland including how the secretions are controlled and regulated, and their functions

The adrenal glands are located just superior to the kidneys and have two distinct regions, the medulla and the cortex. The adrenal medulla releases norepinephrine and epinephrine which accentuate the effects of the sympathetic branch of the autonomic nervous system increase heart rate, mobilise blood glucose stores, enhance alertness, and increase blood pressure The adrenal cortex releases steroid hormones; glucocorticoids, gonadocorticoids and mineralocorticoids: their release is stimulated by ACTH from the anterior pituitary. the main glucocorticoid is cortisol, also called hydrocortisone, and other glucocorticoids include corticosterone and cortisone; supplement the glucose-sparing effect of growth hormone, enabling glucose metabolism needs to be met and cortisol also reduces inflammation gonadocorticoids are androgens which are male sex hormones that may be converted to oestrogens in the blood; targets skin, bone and other tissue and stimulates the development of pubic hair in males and females prior to puberty mineralocorticoids include aldosterone which controls fluid and electrolyte balance; activated by angiotensin in the renin-angiotensin system, aldosterone targets the kidneys where it increases reabsorption of both water and sodium ions

Discuss the pancreas including how the secretions are controlled and regulated, and their functions

the pancreas releases hormones which influence blood glucose levels the pancreas is also an exocrine gland as it secrete enzymes into the gastrointestinal tract located close to a number of digestive organs sitting inferior to the stomach and the proximal part of the small intestine, with its head snug with the duodenum of the small intestine pancreatic islets; the alpha islets release the hormone glucagon and the beta islets release the hormone insulin Glucagon is released in response to a low level of glucose in the blood and targets the liver, stimulating glycogen breakdown (i.e. glycogenolysis) and the release of glucose into the blood Insulin is released when blood glucose levels are greater than the homeostatic range and targets cells generally, to take up glucose for their own metabolic requirements; excess glucose is converted to glycogen for energy storage

Discuss how the endocrine system facilitates long-term responses in the human body.

nitiated at least 30 mins after exposure to stressors Hypothalamus stimulates release of major glucocorticoid; cortisol CRH → ACTH → cortisol [and aldosterone] Cortisol is released from the adrenal cortex: Stimulates lipolysis and gluconeogenesis Releases amino acids from skeletal muscle Vasoconstricts blood vessels of non-essential organs Inhibits inflammation and the immune response Normally, diurnal pattern of cortisol secretion generated by hypothalamus; peaks about 2hrs before awakening and troughs just before falling asleep; regulated by negative feedback Stress can override the diurnal pattern and negative feedback regulation Severe pain and prolonged exercise typically cause secretion of cortisol Activation of cell-mediated immunity increases ACTH and cortisol; link between endocrine and immune systems Cortisol allows critical processes in the body to occur: Amplify effects of other hormones (i.e. glucagon) Facilitates enzyme induction Most important overall effect of cortisol is to stimulate conversion of amino acids and fatty acids to glucose to "save" glucose for the brain ⇒ glucocorticoid

short term response to stress

-heart rate increases -blood pressure increases -bronchioles dilate -liver converts glycogen to glucose and releases glucose to blood -blood flow changes, reduces digestive system activity and urine output -metabolic rate increaes

Long term response to stress

-kidneys retain sodium and water -blood volume and blood pressure rise -proteins and fats converted to glucose or broken down for energy -blood glucose increases -immune system supressed

What are the phases of the stress response

Alarm Phase ("Fight or Flight") -increased mental awareness -increased energy used by all cells -mobilisation of glycogen and lipid reserves -changes in circulation -reduction in digestive activity and urine production -increased sweat gland secretion -increased sweat gland secretion -increased heart rate and respiratory rate. Resistance Phase -mobilisation of remaining energy reserves: lipids are released by adipose tissue; amino acids are released by skeletal muscle -conversion of glucose: peripheral tissues (except neural) break down lipids to obtain energy -increased blood glucose concentrations: liver synthesises glucose from other carbohydrates, amino acids, and lipids -conservation of salts and water, loss of K+ and H+ Exhaustion Phase -exhaustion of lipid reserves and the breakdown of structural proteins as the body's primary energy source, damaging vital organs -infections that develop due to the suppression of inflammation and of the immune response, a secondary effect of the glucocorticoids that are essential to the metabolic activities of the resistance phase -cardiovascular damage and complications that are related ti ADG and Aldosterone- related elevations in blood pressure and blood volume -inability of the adrenal context o continue producing glucocorticoids which results in a failure to maintain acceptable blood glucose concentrations -failure to maintain adequate fluid and electrolyte balance.

Discuss the control and regulation of pituitary gland hormones in the human body.

All of anterior pituitary hormones are stimulated or inhibited by specific hypothalamic hormones For example, if growth hormone is required in the body, the hypothalamus will release GHRH (growth hormone releasing hormone); if growth hormone is not required then the hypothalamus will release GHIH (growth hormone inhibiting hormone)

compare and contrast the transport and mechanism of action of amino acid-based and steroid hormones;

Amino acid-based and peptide hormones are usually water soluble; transported in the blood easily as they diffuse from their site of release towards their target tissue Steroid based hormones are not soluble in water; synthesised from cholesterol and require a carrier protein to be transported in the blood to their target tissue Steroid hormones diffuse into the cell across the phospholipid bilayer and bind to intracellular receptors in the cytoplasm or in the nucleus and activate a specific gene and a specific protein is then synthesised which will result in a specific alteration in cellular activity or structure. Amino acid-based hormones bind to a protein receptor on the external surface of the cell which activates an intracellular protein called a G protein, this activates a second messenger such as cyclic AMP to activate enzymes or open ion channels causing a metabolic effect which stimulates metabolic activity in the cell.

Describe how glucose homeostasis is maintained by pancreatic hormones and non-pancreatic hormones;

Blood glucose levels are homeostatically controlled by the pancreatic hormones; insulin and glucagon Increasing blood glucose levels: 1. Homeostasis disturbed, increasing blood glucose levels 2. beta cells secrete insulin 3.- increased rate of transport into target cells -increased rate of glucose utilisation and ATP generation -increased conversion of glucose to glycogen -increases amino acid absorption and protein synthesis -increased triglyceride synthesis un adipose tissue 4. Homeostasis restored, blood glucose levels drop Decreasing blood glucose levels 1. Homeostasis disturbed, Decreasing blood glucose levels 2. alpha cells secrete glucagon 3. -increased breakdown of glycogen to glucose (in liver, skeletal muscle) -increased breakdown of fat to fatty acids (in adipose tissue) -increased synthesis and release of glucose (in liver) 4. Homeostasis restored, blood glucose levels rise

What is located in the infundibulum

Both the hypophyseal portal system and the hypophyseal tract are located within the infundibulum

Describe the hypofunction disorder of the pancreas; diabetes mellitus;

Diabetes mellitus results from hyposecretion or hypoactivity of insulin The three cardinal signs of diabetes mellitus are: Polyuria Polydipsia Polyphagia The two common types of diabetes mellitus are: type1 (insulin-dependant diabetes mellitus); and type 2 (non-insulin dependant diabetes mellitus) A number of organs are affected by diabetes mellitus

Discuss the different methods of intercellular communication that occur in the human body

Direct Communication: transmits through: Through gap junctions Chemical mediators: Ions, Small solutes, lipid-soluable materials Distribution of effects: Usually limited to adjacent cells of the same type that are interconnected by connexons Paracrine communication: transmits through:Through extracellular fluid Chemical mediators: Paracrine factors Distribution of effects: Primarily limited to the local area where paracrine factor concentrations are relatively high; target cells must have appropriate receptors Endocrine communication: transmits through: Through the bloodstream Chemical mediators: Hormones Distribution of effects: Target cells are mainly in other distant tissues and organs and must have appropriate receptors Synaptic Communication: Across synapses transmits through: Neurotransmitters Chemical mediators Distribution of effects: Limited to very specific area; target cells must have appropriate receptors

Discuss how the endocrine system facilitates short-term responses in the human body.

During fight or flight the hypothalamus stimulates the sympathetic nervous system and the adrenal medulla Sympathetic responses include: Increases in cardiac output, ventilation and sweating Changes in BP and redirecting blood flow to vital tissues and skeletal muscle Epinephrine responses include: Enhancing sympathetic response and mobilising carbohydrate and fat stores → Short term responses The Adrenal medulla is a specialised sympathetic ganglion which releases epinephrine; part of the sympathetic response Epinephrine is also secreted in response to mild hypoglycaemia, moderate hypoxia and fasting Metabolic effects of epinephrine include liver glycogenolysis, lipolysis, gluconeogenesis and increased metabolic rate → ensure glucose is available for the central nervous system; essential to cope with stress

Describe the chemical nature of hormones

Endocrine hormones are chemicals and are usually amino acid-based or steroid-based. Classified into three groups; amino acid derivatives, peptide hormones, and lipid derivatives Amino acid derivatives include thyroid hormones, catecholamines and tryptophan derivatives such as melatonin. Peptide hormones include a number of different hormones such as anti-diuretic hormone, insulin and prolactin as well as glycoprotein hormones such as thyroid-stimulating hormone and luteneising hormone Lipid derivatives includes steroid hormones released from the reproductive organs and the cortex of the adrenal glands and local hormones which are biologically active lipids. These are known as eicosanoids.

outline the role of negative and positive feedback in the endocrine system.

Hormone levels then need to be regulated according to the body's requirements. This regulation occurs through feedback mechanisms; negative feedback Blood glucose levels increased above homeostatic range(due to absorption of chocolate bar) ↓ Pancreas stimulated to release insulin ↓ Insulin stimulates cellular uptake of glucose ↓ Blood glucose levels decrease to homeostatic level ↓ Pancreas no longer stimulated to release insulin positive feedback Baby suckles nipple - stimulates stretch receptors ↓ Hypothalamus and posterior pituitary stimulated ↓ Oxytocin released ↓ Oxytocin stimulates milk secretion from mammary glands ↓ Hypothalamus and posterior pituitary continue to be stimulated until birth occurs (ie stimulus is lost!)

Name and describe the three types of stimuli that control hormone release in the human body

Humoral Stimulas Hormone release caused by altered levels of certain critical ions or nutrients. E.g. stimulus: low concentration of Ca2+ in capillary blood. Response: parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+. Neural stimulation hormone release caused by neural input e.g. Stimulus: action potentials in preganglionic sympathetic fibers to adrenal medulla. Response: adrenal medulla cells secrete epinephrine and norepinephrine Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). e.g. stimulus: hormones from hypothalamus. Response: anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones.

Discuss how the hypothalamus controls the anterior and posterior lobes of the pituitary gland;

In the central nervous system, the main endocrine glands are the hypothalamus and pituitary gland. The hypothalamus is the master gland of the endocrine system as it controls the anterior and posterior pituitary gland The connection between the hypothalamus and anterior pituitary gland is vascular and is referred to as the hypophyseal portal system hormones are released into one capillary bed in the hypothalamus and then travel through a group of veins to a second capillary bed in the anterior pituitary This second capillary bed enables the endocrine cells in the anterior pituitary to be stimulated The connection between the hypothalamus and posterior pituitary gland is neural and is called the the hypophyseal tract Action potential are released from neurosecretory cells to the posterior pituitary

using examples, describe the various functions of hormones in the human body?

Insulin: hormone is released by pancreas. It allows the body to use glucose or sugar from carbohydrates in the food for energy or to store glucose for future use as glycagon Estrogen: released by the ovaries. It is responsible for the reproduction, menstruation and menopause. Cortisol: This hormone is produced by the adrenal gland. It helps you stay healthy and energetic. Its main role is to control physical and psychological stress. In danger condition it increases heart rate, blood pressure, respiration etc. Adrenaline/ epinephrin: secreted in the medulla in the adrenal gland as well as some of the central nervous system's neurons. It is also known as emergency hormone because it initiates the quick reaction which makes the individual to think and respond quickly to the stress. It increases the metabolic rate, dilation of blood vessels going to the heart and the brain. Growth Hormone: it stimulates growth, cell reproduction cell regeneration and in boosting metabolism.

Discuss the parathyroid gland including how the secretions are controlled and regulated, and their functions

Parathyroid glands control calcium homeostasis and are located in the posterior surface of the thyroid gland Parathyroid hormone also known as PTH is released in response to low blood calcium levels and directly targets two areas; the renal system and the skeletal system. PTH targets bone cells and stimulates the release of calcium from bone by affecting osteoblast and osteoclast activity PTH targets kidney tubule cells and stimulates calcium reabsorption and also stimulates the formation and release of calcitriol Calcitriol stimulates the absorption of calcium in the intestinal tract, an indirect action of PTH Calcitonin (secreted from the thyroid gland) and parathyroid hormone (from the parathyroid glands) work together to maintain calcium homeostasis in the human body

Describe the functions of endocrine hormones released the posterior pituitary gland;

Releases a total of six hormones. Trophic hormones are hormones that act as a hormonal stimuli and may have a specific function as well; thyroid-stimulating hormone (TSH) TSH stimulates the thyroid gland to release hormones adrenocorticotrophic hormone (ACTH) ACTH stimulates the release of hormones from the cortex of the adrenal glands follicle stimulating hormone (FSH) & luteneising hormone (LH). FSH and LH stimulate the male gonads (the testes) and the female gonads (the ovaries) and have additional effects on their target tissues stimulating egg and sperm cell production and the release of an egg cell from the ovary as part of the ovarian monthly cycle Non-trophic anterior pituitary hormones that do not fulfil a role as a hormonal stimuli are prolactin Prolactin stimulates the production of milk in the female mammary glands growth hormone. Growth hormone stimulates growth by stimulating protein synthesis thereby enhancing cell growth and reproduction through an indirect process and also has other functions; targets liver cells which release insulin-like growth factors or somatomedins; these bind to receptors on skeletal muscle fibres, cartilage cells and other target cells and enhance the uptake of amino acids into cells and their incorporation into new proteins directly stimulates cell division and cell differentiation in epithelial and connective tissues influences blood glucose levels stimulating the release of glucose from energy stores in the human body

Describe the functions of endocrine hormones released the anterior pituitary gland

Secretes two hormones; oxytocin and ADH Oxytocin functions in childbirth and breastfeeding Anti-diuretic hormone (ADH) functions in fluid and electrolyte balance by targeting special tubule cells in the kidneys to inhibit diuresis which is the release of water from the body

Name the endocrine organs and non-endocrine organs which secrete hormones;

Specific endocrine glands secrete specific hormones (chemical messengers) typically into the circulatory system The endocrine glands in the central nervous system are the hypothalamus, pituitary gland and pineal gland Other endocrine glands include the thyroid gland, parathyroid glands, the pancreas, and the adrenal glands Hormones can also be secreted from other organs Heart Small intestines Gonads Thymus Kidneys

How does the hypothalamus direct the stress response

Stimuli activates receptors ↓ Nerve impulses sent to hypothalamus ↓ Nervous system and endocrine system activated ↓ Stress response occurs to try to maintain homeostasis and enable body to cope

Discuss the pineal gland including how the secretions are controlled and regulated, and their functions

The pineal gland located in the diencephalon and releases the hormone melatonin which affects reproductive function and controls the sleep-wake cycles of the human body, also referred to as circadian rhythms.

Describe the location of the peripheral endocrine glands; the pineal, thyroid, parathyroid, pancreas and adrenal gland in the human body;

Thyroid Gland located in the neck region across the anterior surface of the trachea (or windpipe) just inferior to the thyroid cartilage Parathyroid Glands located in the posterior surface of the thyroid gland Adrenal Glands The adrenal glands are located just superior to the kidneys Pancreas The Pancreas is located in the abdominal cavity, Pineal Gland the pineal gland located in the diencephalon

Discuss the thyroid gland including how the secretions are controlled and regulated, and their functions

composed of two lobes which are joined by a narrowing called the isthmus The thyroid gland contains follicles and requires iodide to produce hormones that controls metabolism two main hormones are thyroxine, also known as T4, and triiodothyronine, also known as T3 thyroid hormones are produced and then stored within thyroglobulin in thyroid follicle cells Iodide ions are required to synthesise thyroid hormones T4 and T3 are synthesised and incorporated into thyroglobulin which is released into the thyroid follicle cavity; follicle cells can then remove the thyroglobulin and release T3 and T4 when the thyroid gland is stimulated up to 75% of the T3 and T4 molecules in the blood are bound to thyroid-binding globulin which acts as a transport protein and releases the thyroid hormones gradually - Importance? T4 and T3 have an effect on a variety of peripheral tissues; they stimulate other endocrine tissues, enhance oxygen delivery to cells, increase heart rate and often blood pressure, accelerate the turnover of minerals in bone, increase sensitivity of tissues to sympathetic nerve stimulation and overall, both T4 and T3 enhance metabolic rate and therefore influence energy metabolism. A third thyroid gland hormone is calcitonin which helps to regulate calcium levels in body fluids. Calcitonin lowers blood calcium levels by stimulating calcium uptake into bone cells. This occurs when there is surplus calcium in the blood.

Describe the role of the endocrine system as a control system in the human body;

endocrine system is much slower as it utilises chemical hormones secreted in the blood to inhibit or stimulate a physiological event

Describe the glucose tolerance test

fast for 8-12 hours, have blood drawn for a baseline glucose level and every 30 minutes for 2 hours A glucose tolerance test measures how well your body is able to absorb glucose or sugar after you ingest a given amount of sugar.