Biology 30 Notes

Biology 30 Notes

Topic Categories

  • Textbook: Inquiry to Biology

  • Chapters:

    • 13: Homeostasis and the Endocrine System

    • 14: Reproductive Systems

    • 15: Human Development

    • 16: Cell Division

    • 17: Genetics and Inheritance

    • 18: Molecular Genetics

    • 11-12: The Nervous System & Sensory Reception

    • 19: Hardy-Weinberg Principle

    • 20: Population Dynamics

Chapter 13: The Endocrine System & Homeostasis

  • Homeostasis

    • Definition: the tendency of the body to maintain a relatively constant internal environment

    • Example: The body reacts to cold temperatures outside with special temperatures on the skin telling the brain to tell the skeletal muscles to shiver which will generate heat through increased muscular activity.

  • Endocrine System

    • Definition: in vertebrates, a system that works in parallel with the nervous system to maintain homeostasis by releasing chemical hormones from various glands

    • Composed of the endocrine glands and tissues of the body

  • Endocrine Glands

    • Definition: ductless glands that secrete hormones directly into the bloodstream

    • Secretes hormones into the body

  • Exocrine Glands

    • Definition: gland which secretes hormones via ducts

    • Secretes products outside the body

  • Hormone

    • Definition: chemical messenger sent to many parts of the body to produce a specific effect on a target cell or organ

    • Example: In the pancreas, an endocrine gland secretes the hormone insulin into the bloodstream to make its target cells more permeable to glucose

Homeostasis: Endocrine System vs. Nervous System

  • Endocrine System

    • Slower actions & longer acting effects

    • Affects a broader range of cell types

    • Some tissues secrete hormones (e.g., hypothalamus, pituitary gland, adrenal glands)

    • Responses regulated by negative feedback loops

    • Example: Breastfeeding

      • The baby’s suckling initiates a sensory message in the mother’s neurons that travels to the hypothalamus

      • The message in the hypothalamus triggers the pituitary gland to release the hormone oxytocin

      • Oxytocins travel in the bloodstream to the mammary glands of the breasts, and milk is secreted

  • Nervous System

    • Rapid actions

    • Affects specific cell types

    • Several chemicals work as both neurotransmitters and hormones depending on their location in the body (e.g., epinephrine)

      • Epinephrine acts as a neurotransmitter between specific neurons in the nervous system and as a hormone released by the adrenal glands in fight or flight response

    • Responses regulated by negative feedback loops

  • Endocrine and nervous systems work together to regulate several physiological processes

Proving the Existence of Hormones: Arnold Adolph Berthold (1849)

  • Berthold removed the testes of roosters (called capons), and they had different behaviours such as not crowing, fighting, or mating, and they didn’t grow very large

  • When the testes were put back into the capons, they began to look and behave like typical male roosters

  • Since the replaced testes weren’t connected to any nerves, then something in the bloodstream caused the developmental changes in male birds, which was testosterone.

Challenges in Studying Hormones

  • Removing endocrine glands from animals wasn’t useful for studying hormones since hormones often work together and another gland/hormone can replace a missing one

  • Some glands can even produce more than one hormone

  • Hormone concentration in the blood is also extremely low and isn’t released continually but is triggered through environmental factors or patterns

Technologies to Study Hormones and Endocrine Glands

  • Nuclear scanning devices (such as PET) and high-powered microscopes allow scientists to visualize glands, hormones, and target cell membranes

  • Fluorescent stains are also used to colour the different hormones in a tissue sample

  • For endocrine glands, doctors have patients ingest capsules with little radioactive material

  • This radioactive material accumulates in specific glands, making them easy to distinguish in PET scans or by other methods

The Principle Endocrine Glands

  • Hypothalamus

  • Anterior Pituitary

  • Posterior Pituitary

  • Thyroid

  • Parathyroid

  • Adrenal cortex

  • Adrenal Medulla

  • Pancreas

  • Ovaries

  • Testes

Hypothalamus

  • Definition: region of the forebrain just below the cerebral hemispheres, under the thalamus

  • A centre of the autonomic nervous system responsible for the integration and correlation of many neural and endocrine functions

  • Helps to regulate the body’s internal environment, as well as certain aspects of behaviour

  • Coordinates the actions of the pituitary gland by producing and regulating the release of certain hormones

  • Hormone secreted + Function:

    • Hypothalamic releasing-and inhibiting-hormones

    • Regulates anterior pituitary gland hormones

Anterior Pituitary

  • Definition: anterior lobe of the pituitary

  • Hormones secreted + Function:

    • Human growth hormone (hGH) - Stimulates cell division, bone and muscle growth, and metabolic functions

    • Thyroid-stimulating hormone (TSH) - Stimulates the thyroid gland

    • Adrenocorticotropic hormone (ACTH) - Stimulates the adrenal cortex to secrete glucocorticoids

    • Follicle-stimulating hormone (FSH) - Stimulates production of ova and sperm from the ovaries and testes

    • Luteinizing hormone (LH) - Stimulates sex hormone production from the ovaries and testes

    • Prolactin (PRL) - Stimulates milk production from the mammary glands

Posterior Pituitary

  • Definition: posterior lobe of the pituitary gland

  • Hormones secreted + Function:

    • Antidiuretic Hormone (ADH) - Promotes the retention of water by the kidneys

    • Oxytocin (OCT) - Stimulates uterine muscle contractions and release of milk by the mammary glands

  • The hormones are produced in the hypothalamus and transferred to the posterior pituitary by neural axons

Thyroid Gland

  • Definition: butterfly-shaped gland located below the larynx in the neck

  • Hormones secreted + Function:

    • Thyroxine (T4) - Affects all tissues; increases metabolic rate and regulates growth and development

    • Calcitonin - Targets bones and kidneys to lower blood calcium by inhibiting release of calcium from bone and reabsorption of calcium by kidneys

Parathyroid Gland

  • Releases the parathyroid hormone (PTH)

  • Parathyroid Hormone: hormone produced by parathyroid glands in response to falling concentrations of calcium in the blood

    • Stimulates bone cells to break down bone material (calcium phosphate) and reabsorb calcium into the blood

    • Stimulates the kidneys to reabsorb calcium from the urine

    • Activates vitamin D, which stimulates the absorption of calcium from food in the intestine

Adrenal Cortex

  • Definition: the outer layer of the adrenal glands

  • Hormones secreted + Function

    • Glucocorticoids (e.g., cortisol) - Stimulates tissues to raise blood glucose and break down protein

    • Mineralocorticoids (e.g., aldosterone) - Promote reabsorption of sodium and water by the kidneys

    • Gonadocorticoids - Promote secondary sexual characteristics

Adrenal Medulla

  • Definition: the inner layer of the adrenal glands

  • Hormones secreted + Function

    • Epinephrine and norepinephrine - Fight-or-flight response hormones raise blood glucose levels

Pancreas

  • Definition: small gland in the abdomen that secretes digestive enzymes into the small intestine, as well as bicarbonate to neutralize hydrochloric acid from the stomach

  • Hormones secreted + Function

    • Insulin - Lower blood glucose levels and promote glycogen formation in the liver

    • Glucagon - Raises blood glucose levels by converting glycogen to glucose

Ovary

  • Definition: in mammals, one of a pair of female reproductive organs (gonads)

  • Suspended in the abdominal cavity and produces eggs (ova)

  • Hormones secreted + Function

    • Estrogen - Stimulates uterine lining growth and promotes development of the female secondary sexual characteristics

    • Progesterone - Promotes growth of the uterine lining and prevents uterine muscle contractions

Testes

  • Definition: in mammals, a pair of male reproductive organs (gonads) that makes sperm

  • Hormone secreted + Function

    • Testosterone - Promotes sperm formation and development of the male secondary sexual characteristics

Hormones Affecting Target Cells

  • Each cell contains receptor proteins, that hormones bind to

  • Example: Human growth hormone (hGH) circulates in the bloodstream and interacts with the liver, muscle, and bone cells

  • Each of these cell types has receptor proteins shaped to bind with hGH

  • When the hormone binds to its receptor, the target cell receives and responds to the chemical message sent by the hormone

Lipid-Soluble Hormones vs, Water-Soluble Hormones

  • Lipid-Soluble

    • Lipid-Based

    • Can diffuse through the lipid bilayer of cell membranes

    • Example: Steroid hormones (testosterone, estrogen)

  • Water-Soluble

    • Amino-acid based

    • Cannot diffuse across the cell membrane and binds to a receptor protein on the surface of the cell

    • Example: Epinephrine, hGH

    • Can cause many reactions inside the cell and its impact is greatly amplified

Negative Feedback Mechanisms

  • Definition: mechanism of homeostatic response by which the output of a system suppresses or inhibits the activity of the system

  • When a certain blood concentration of hormone is reached, or when target cells have responded to a specific hormone, the endocrine gland releasing the hormone is inhibited, and the release of the hormone is slowed

  • Example: Antidiuretic hormone (ADH)

    • When the blood plasma becomes too concentrated, receptors in the hypothalamus detect this and send a neural sign to the posterior pituitary gland to release ADH

    • ADH targets the nephrons, causing the tubules to become more permeable to water, and water is reabsorbed and the body excretes less (but more concentrated) urine, and blood pressure rises

    • The hypothalamus detects this and sends a signal to the posterior pituitary to stop secreting ADH

Tropic Hormones

  • Definition: hormone that targets endocrine glands and stimulates them to release other hormones

  • These types of hormones are released from the anterior pituitary and the hypothalamus

  • Typically the hypothalamus secretes a releasing hormone into the anterior pituitary, causing the anterior pituitary to release a tropic hormone into the bloodstream

  • The tropic hormone then stimulates the target gland to release a third hormone into the blood which travels to another target tissue, producing an effect

  • This system is controlled by a negative feedback loop in which the third hormone prevents further release of the first two hormones in the pathway

Chapter 13.2 - Hormonal Regulation of Growth, Development, and Metabolism

The Pituitary Gland

  • Definition: small gland that lies just inferior to the hypothalamus

  • Consists of the anterior and posterior pituitary, both of which produce hormones that influence metabolism, growth, development, reproduction, and other critical functions

  • Known as “the master gland” as it releases several tropic hormones

  • Controlled by the hypothalamus via releasing hormones and neurons that run through the connecting stalk to maintain homeostasis

Posterior Pituitary

  • Definition: posterior lobe of the pituitary gland

  • Considered part of the nervous system

  • Stores and releases the hormones produced by the hypothalamus through neuronal axons

  • Hormone Secreted + Effects of Hormone

    • Antidiuretic hormone (ADH) - Promotes the retention of water by the kidneys

    • Oxytocin (OCT) - Stimulates uterine muscle contractions and release of milk by the mammary glands

Anterior Pituitary

  • Definition: anterior lobe of the pituitary

  • Its cells produce and release six major hormones

  • A series of blood vessels (portal system) carry hormones from the hypothalamus to the anterior pituitary, either stimulating or inhibiting the release of hormones from this gland

  • Hormone Secreted + Effects of Hormone

    • Human Growth Hormone (hGH) - Stimulates cell division, bone and muscle growth, and metabolic functions

    • Thyroid-stimulating hormone (TSH) - Stimulates the thyroid gland

    • Adrenocorticotropic hormone (ACTH) - Stimulates the adrenal cortex to secrete glucocorticoids

    • Follicle-stimulating hormone (FSH) - Stimulates production of ova and sperm from the ovaries and testes

    • Luteinizing hormone (LH) - Stimulates sex hormone production from the ovaries and testes

    • Prolactin (PRL) - Stimulates milk production from the mammary glands

Human Growth Hormone (hGH)

  • Definition: a hormone that ultimately affects almost every body tissue, by direct stimulation or via tropic effects

  • Stimulates the liver to secrete hormones called growth factors which, along with hGH, influence many physiological processes like protein synthesis, cell division and growth, and the metabolic breakdown of fats

  • Secreted by anterior pituitary

  • Majority of its effects are tropic

  • Stimulates muscle growth, connective tissue, and growth of plates at the end of long bones, causing bone elongation

Imbalance of Human Growth Hormone

  • Gigantism: Excessive hGH production during childhood, resulting in abnormally tall height in adulthood

  • Pituitary dwarfism: insufficient hGH production during childhood: resulting in abnormally short height in adulthood

  • Acromegaly: overproduction of hGH when skeletal growth is complete, meaning the excess hGH doesn’t increase the height of the bones, but rather widens them

    • Not only affect appearance, but if untreated, it will cause cardiovascular diseases, sugar intolerance (diabetes), breathing problems, muscle weakness, and colon cancer

Thyroid Gland

  • Definition: butterfly-shaped gland located below the larynx in the neck

  • Has two lobes, one on either side of the trachea which are joined by a band of tissue

  • Produces the hormone thyroxine to help regulate metabolism and growth

  • Thyroxine (T4): hormone produced by the thyroid and released into the bloodstream

    • Controls the rate at which the body metabolizes fats, proteins and carbohydrates for energy

    • Stimulates the cells of the heart, skeletal muscles, liver, and kidney to increase cellular respiration rate

    • Plays a role in the growth and development of children by influencing the organization of various cells into tissues and organs

    • Its secretion is controlled by negative feedback

Hypothyroidism

  • Definition: condition resulting when the thyroid produces low levels of thyroxine

  • If the thyroid fails to develop properly during childhood, a condition called cretinism can result, which is the cause of the low thyroxine production

    • People with cretinism are stocky and shorter than average, and without hormonal injections early on in life, they will have mental development delays

  • Adults with hypothyroidism often feel tired, have a slow pulse rate and puffy skin, and experience hair loss and weight gain

    • This explains why people with slow metabolism due to an underactive thyroid may eat very little but still gain weight

Hyperthyroidism

  • Definition: condition resulting when the thyroid produces extremely high levels of thyroxine

  • Symptoms: anxiety, insomnia, heat intolerance, irregular heartbeat, and weight loss

  • Grave’s disease is a severe state of hyperthyroidism that results when the body’s immune system attacks the thyroid

    • In addition to the other hyperthyroidism symptoms, Graves’ disease produces swelling of muscles around the eyes, causing them to protrude and affect vision

  • Can be treated by medications or removal or irradiation of part of the thyroid

Thyroid Stimulating Hormone (TSH)

  • Definition: a hormone released by the anterior pituitary which causes the thyroid gland to secrete thyroxine

  • Controlled by a negative feedback mechanism:

    • Rising thyroxine levels in the blood detected by the hypothalamus and anterior pituitary suppress the secretion of TSH and, therefore, thyroxine

  • Healthy bodies have a relatively constant thyroxine concentration in the bloodstream

  • The thyroid requires iodine to make the thyroid hormones

    • The thyroxine term, T4, refers to the four iodine molecules in the hormone

  • If there is insufficient iodine in the diet, thyroxine can’t be made, and there will be no signal to stop the secretion of TSH by the anterior pituitary

  • The relentless stimulation of the thyroid gland by TSH causes a goitre

  • Goitre: enlargement of the thyroid gland characterized by a large swelling in the throat

    • Often associated with a deficiency of iodine

    • Occurs when the thyroid gland is constantly stimulated by TSH but is unable to synthesize thyroxine to create a negative feedback loop

Calcitonin

  • Definition: hormone that regulates calcium levels in the blood

  • Stimulates the uptake of calcium into bones when the concentration of calcium in the blood rises too high

  • Calcium plays is essential for healthy teeth and skeletal development and plays a role in blood clotting, nerve conduction, and muscle contraction

  • Calcitonin’s regulation is more significant in some vertebrates but not in humans as we secrete a different hormone by the parathyroid glands for calcium homeostasis

Parathyroid Glands

  • 4 small glands attached to the thyroid, which produce parathyroid hormone

  • Parathyroid hormone: hormone produced by the parathyroid glands in response to falling concentrations of calcium in the blood

    • Stimulates bone cells to break down bone material (calcium phosphate) and reabsorb calcium into the blood

    • Stimulates the kidneys to reabsorb calcium from the urine

    • Activates vitamin D, which stimulates the absorption of calcium from food in the intestine

  • The effects of parathyroid hormone bring the concentration of calcium in the blood back within a normal range so that the parathyroid glands no longer secrete PTH

Chapter 13.3 - Hormonal Regulation of the Stress Response

Adrenal Glands

  • Definition: one pair of organs located on top of the kidneys

  • Composed of two layers:

    • Adrenal medulla (inner layer)

    • Adrenal cortex (outer layer)

  • Each layer produces different hormones and functions as an independent organ

  • The adrenal cortex produces hormones that are different in structure and function from the hormones produced by the adrenal medulla

Adrenal Medulla

  • Definition: the inner layer of the adrenal glands that produces epinephrine and norepinephrine, hormones that regulate the short-term stress response

  • Epinephrine: hormone produced by the adrenal cortex hormones that helps regulate the short-term stress response; AKA adrenaline

  • Norepinephrine: neurotransmitter released by sympathetic neurons of the autonomic system to produce an excitatory effect on target muscles; AKA noradrenaline

    • Another hormone produced by the adrenal medulla to function in short-term stress response

  • Short-term stress response: the body’s acute reaction to stress in which the sympathetic nervous system is stimulated; AKA flight-or-fight response

  • The effects of these hormones on the body are similar to those caused by stimulation of the sympathetic nervous system

  • In the developing embryo, sympathetic neurons and adrenal medulla cells are both formed from nervous system tissue, explaining why the adrenal medulla is considered a neuroendocrine structure

Regulating the Short-Term Stress Response

  • The adrenal medulla uses hormones to prepare the body for flight-or-flight by increasing metabolism

    1. In response to a stressor, neurons of the sympathetic nervous system carry a signal from the hypothalamus directly to the adrenal medulla

    2. These neurones stimulate the adrenal medulla to secrete epinephrine and a small amount of norepinephrine

    3. Epinephrine and norepinephrine trigger an increase in breathing rate, heart rate, blood pressure, blood flow to the heart and muscles, and the conversion of glycogen to glucose in the liver

    4. Pupils dilate and blood flow to the extremities decreases

  • Epinephrine and norepinephrine release is fast because it is under nervous system control

  • Although the hormonal effects are similar to those of the sympathetic nervous system, their influence on the body lasts about 10x longer

Adrenal Cortex

  • Definition: the outer layer of the adrenal glands that produce glucocorticoids and mineralocorticoids, hormones that regulate the long-term stress response

  • Also secretes a small amount of gonadocorticoids female and male sex hormones that supplement the hormones produced by the gonads

  • Long-term stress response: sustained physiological response to stressors, characterized by increases in blood glucose and blood pressure, and a decrease in inflammatory response

    • Regulated by hormones produced by the adrenal cortex

  • Glucocorticoids increase blood sugar

  • Mineralocorticoids increase blood pressure

Cortisol

  • Definition: a type of glucocorticoid hormone released by the adrenal cortex of the adrenal gland in a long-term stress response

  • Triggers an increase in blood glucose levels and reduces inflammation

    • Glucose levels rise due to cortisol promoting the breakdown of muscle protein into amino acids which are taken out of the blood by the liver where they are used to make glucose, then released back into the blood

    • Fat cells are also broken down to promote glucose release

    • Cortisol is a natural anti-inflammatory in the body

  • Most abundant glucocorticoid

  • Steroid hormone synthesized from cholesterol

  • When danger is detected, the brain tells the hypothalamus to secrete a releasing hormone, stimulating the anterior pituitary gland to secrete Adrenocorticotropic hormone

  • Adrenocorticotropic Hormone (ACTH): hormone synthesized by the anterior pituitary gland to target the adrenal cortex and regulate the production of glucocorticoids

    • Targets the adrenal cortex, causing the release of cortisol

  • Cortisol often works in conjunction with epinephrine but is longer-lasting

  • Increased cortisol levels in the blood cause negative feedback on the hypothalamus and anterior pituitary, suppressing the ACTH production and stopping cortisol release

  • Sustained high levels of cortisol in chronic stress can impair thinking, damage the heart, raise blood pressure, bring diabetes, increase susceptibility to infection, and even death

Aldosterone

  • Definition: a type of mineralocorticoid hormone secreted by the adrenal cortex

  • Stimulates the distal tubule and collecting duct of the kidneys to increase the absorption of sodium into the bloodstream, which is followed by the passive absorption of water and chloride

  • If the adrenal cortex is damaged, Addison’s disease can result, where the body secretes inadequate amounts of mineralocorticoids and glucocorticoids

  • Symptoms of Addison’s disease include, Hypoglycemia (Low blood sugar), Sodium and potassium imbalances, Rapid weight loss, and general weakness

  • Low aldosterone results in a loss of sodium and water from the blood due to increased urine output, which drops blood pressure

  • A person with this condition needs to be treated within days, or the severe electrolyte imbalance will be fatal

Chapter 13.4 - Hormonal Regulation of Blood Sugar

Pancreas

  • Definition: small gland in the abdomen secreting digestive enzymes into the small intestine, bicarbonate to neutralize hydrochloric acid from the stomach, and insulin

  • Located behind the stomach and is connected to the small intestine by the pancreatic duct

  • The islets of Langerhans are scattered throughout the pancreas to secrete their hormones into the bloodstream

Islet of Langerhans

  • Definition: cluster of endocrine cells found throughout the pancreas, consisting of glucagon-producing alpha cells and insulin-producing beta cells

  • Beta Cell: cell of the pancreas which secretes insulin to decrease the level of blood glucose

  • Alpha Cell: cell of the pancreas which secretes glucagon to increase the level of blood glucose

  • The two hormones that the islets of Langerhans secrete, insulin and glucagon, are antagonistic, meaning they have opposite effects

  • Both insulin and glucagon are regulated by negative feedback mechanisms

Insulin

  • Definition: a hormone secreted by the beta cells of the islets of Langerhans in the pancreas to make target cells more permeable to glucose

  • Enables the body to use sugar and other carbohydrates

  • When eating a meal, the digestive system breaks down the food and releases lots of glucose into the bloodstream

  • When blood glucose levels rise, the pancreatic beta cells secrete appropriate amounts of insulin

  • Insuline especially affects muscle cells, which use large amounts of glucose in cellular respiration, and liver cells, where glucose is converted to glycogen for temporary storage

  • As the glucose levels in the blood return to homeostasis insulin secretion slows

Glucagon

  • Definition: a hormone produced by the alpha cells of the islets of Langerhans in the pancreas to stimulate the liver to convert glycogen back into glucose, which is released into the blood

  • Rigorous exercise or fasting can cause blood glucose levels to drop

  • Low blood sugar stimulates the alpha cells of the islets of Langerhans to release glucagon

  • Other hormones, such as hGH, cortisol, and epinephrine also contribute to increasing the level of blood glucose

Diabetes Mellitus

  • Definition: a serious chronic condition that results when the pancreas does not make enough insulin or the body does not respond properly to insulin

  • Levels of blood glucose tend to rise sharply after meals and remain at significantly elevated levels

  • Hyperglycemia: a condition resulting from high levels of blood glucose

    • Occurs in individuals with diabetes mellitus

    • It has various short-term and long-term effects on the body

  • Without insulin, cells remain relatively impermeable to glucose and cannot obtain enough from the blood

  • Patients experience fatigue as cells starve for glucose

    • The body compensates by switching to protein and fat metabolism for energy

    • However, fats and proteins are less accessible and more difficult to break down

    • Fat metabolism also releases ketones such as acetone, as a toxic by-product

  • The kidneys can’t reabsorb all of the glucose that’s filtered through them from the blood, so glucose is excreted in the urine

    • This changes the osmotic gradient across the nephrons of the kidneys, which causes water to be excreted

  • People with untreated diabetes experience low energy and great thirst, and produce large volumes of glucose-rich urine

  • In the long-term, continued high levels of blood glucose can lead to blindness, kidney failure, nerve damage, and gangrene in the limbs (infection)

  • In many diabetics, the glucagon-producing alpha cells degenerate

  • Two major types of diabetes mellitus:

    • Type 1 diabetes

    • Type 2 Diabetes

Type 1 Diabetes (Juvenile Diabetes, Insulin-dependent Diabetes)

  • Definition: a condition in which the immune system produces antibodies that attack and destroy the beta cells of the pancreas so they are unable to produce insulin

  • Is usually diagnosed in childhood, and patients require daily insulin injections

Type 2 Diabetes (Adult-onset diabetes)

  • Definition: a condition that develops slowly over time either because the insulin receptors on the body’s cells stop responding to insulin or because the beta cells of the pancreas produce less and less insulin over time

  • Condition often appears in overweight adults

  • Can often be controlled with diet, exercise, and oral medications

  • Without proper care, type 2 can develop into type 1

Finding the Cure of Diabetes

  • Oscar Minkowski

    • Removed the pancreas from a healthy dog, causing it to develop diabetic symptoms, which established the relationship between the pancreas and diabetes

    • For the next two decades, researchers attempted to isolate a substance from the pancreas that could be used to treat diabetes

  • Frederick Banting & Charles Best

    • By tying off a dog’s pancreatic duct with some string they were able to remove some islets of Langerhans from the dog’s pancreas, then isolate insulin from the islets

    • This brought Banting’s research team to find a way to isolate insulin from the pancreas of embryonic calves, which were a by-product of the beef industry

    • Working with J.B. Collip, they further purified the extracted insulin and used it to successfully treat a boy with diabetes

  • James Shapiro

    • Pioneered the first successful islet cell transplants to restore functional beta cells

Treating diabetes

  • Synthetic insulin is produced by genetically engineered bacteria and other organisms

  • Blood glucose monitoring devices have been implemented

  • Insulin pumps were made to mimic the pattern of release of insulin

Science, Technology, Society, and the Endocrine System

  • To diagnose an endocrine disorder a doctor could do a blood test to check hormone levels

    • This is not always informative because hormones are secreted in very low amounts and sometimes not continuously

  • Urinialysis is also used for diagnosis

  • Scanning devices to visualize particular endocrine glands can also help with diagnosis

    • PET scans or MRIs can be used to visualize the gland from outside the body, providing information about the relative size or possible inflammation of a gland

  • Treating endocrine disorders usually involves hormone replacement therapy, which gives the patient the hormone that they are lacking

  • Using genetic engineering, we can insert genes for human hormones into bacterial cells so that they can produce hormones for us, giving us a safe, cheap, and reliable source of human hormones

  • Sometimes a tumour on an endocrine gland can cause hypersecretion of particular hormones; in that case, a removal of the tumour or even part of the gland itself can correct the problem

  • Advantages related to these technologies revolve around the improved quality of life for the patients

  • Disadvantages for these technologies can often deal with accessibility

Chapter 14: Reproductive Systems

Chapter 14.1 - The Male and Female Reproductive Systems

The Reproductive System (Introduction)

  • The human reproductive system is adapted to unite a single reproductive cell from a female parent with a single reproductive cell from a male parent

  • To achieve this, the male and female reproductive systems have very different structures and functions

  • The two systems also have any features in common

Gonad

  • Definition: an organ that produces reproductive cells (gametes)

    • The ovary produces eggs (ova)

    • The testis produces sperm

  • The glands also produce sex hormones

Sex Hormones

  • Definition: one of several chemical compounds that control the development and function of the reproductive system or secondary sex characteristics

Primary sex Characteristics

  • Definition: any structure (organ, duct, or gland) that plays a direct role in reproduction

  • The sex organs are internal and external

  • The ducts and glands play a role in forming and transporting gametes

Secondary Sex Characteristics

  • Definition: any of the physical manifestations that distinguish male from female but are not required for reproduction, such as…

    • Distribution of body fat

    • Female breasts

    • Change of voice pitch in adolescent males

    • Differences in muscularity

Table of Primary and Secondary Sex Characteristics

  • Sex - Primary Sex Characteristics - Selected secondary sex characteristics

  • Male

    • Gonads (testes)

    • Penis

    • Scrotum

    • Seminal vesicles

    • Epididymis

    • Prostate gland

    • Ductus Deferens

    • Cowper’s gland

    • Facial Hair

    • Body hair

    • Deeper voice, broader shoulders, narrower hips, and more obvious muscle development compared with female

  • Female

    • Gonads (ovaries)

    • Cervix

    • Oviducts

    • Vagina

    • Uterus

    • Vulva

    • Minimal facial hair

    • Minimal body hair

    • Prominent breasts (compared with male)

    • Higher voice, more rounded, shoulders, wider, hips, and less obvious muscle development compared with male

The Male Reproductive System

Sperm Cells

  • Definition: male reproductive cell (gamete)

  • Stored and produced by organs of the male reproductive system

  • Produced by the testes

  • A mature sperm is a tadpole-shaped structure, about 0.06mm long

  • Each sperm cell has three parts

    • An oval head

      • Contains a nucleus with 23 chromosomes, covered by a cap-like structure called the acrosome

      • The acrosome stores enzymes that are needed to penetrate the protective layer surrounding a female egg

    • A cylindrical middle piece

      • Contains mitochondria, providing energy for the movement of the tail

    • An extended tail

      • Propels the sperm with a lashing motion, allowing it to move at a rate of about 3mm/hour

Testes

  • Definition: in mammals, a pair of male reproductive organs (gonads) that produces sperm

  • Held outside the body in a pouch of skin called the scrotum

  • Scrotum: pouch that contains the testes in most mammals

    • Regulates the temperature of the testes

    • Sperm production is successful at temperatures around 35°C, which is a few degrees cooler than normal body temperature

      • Cold conditions: scrotum draws close to the body, so the testicles stay warm

      • Hot conditions: scrotum holds the testicles loosely, so they’re cooler than the body

  • The testes are composed of long, coiled tubes, called seminiferous tubules, as well as hormone-secreting cells, called interstitial cells, that lie between the seminiferous tubules

    • The interstitial cells secrete the male hormone testosterone

Seminiferous Tubules

  • Definition: long, coiled tube inside the testes in which sperm are produced

  • The production of sperm is called spermatogenesis

  • Each testis contains more than 250m of seminiferous tubules and can produce more than 100 million sperm each day

Sertoli Cells

  • Definition: cells within the seminiferous tubules that support and nourish developing sperm

Epididymis

  • Definition: in human males, a narrow, tightly coiled tube connecting the seminiferous tubules to the ductus deferens

  • Within, the sperm mature and become motile

Ductus Deferens

  • Definition: a storage duct from the epididymis leading to the penis via the ejaculatory duct

Ejaculatory Duct

  • Definition: tube connecting the