6.6 Syllabus

U1. ​Insulin and glucagon are secreted by beta and alpha cells of the pancreas respectively to control blood glucose concentrations.

  • Blood glucose concentrations is carefully monitored by negative feedback mechanisms
  • Cellular respiration is constantly lowering blood glucose levels
  • Receptors in the pancreas sense when the blood glucose level is too low
  • Alpha cells in the islets in the pancreas secrete glucagon into the blood stream
  • Glucagon stimulates the liver to breakdown stored glycogen into glucose which is released into the bloodstream
  • Blood glucose levels rise back to their normal limits
  • After a person eats, digestion breaks large carbohydrates into glucose molecules
  • Glucose levels rise in the blood
  • If the glucose levels get too high, receptors sense the increased glucose levels causing the pancreas to secrete insulin by the Beta cells of the islets 
  • Insulin stimulate the absorption of glucose from the blood into skeletal muscles and fat tissue, and thus allowing the liver to convert glucose into glycogen 
  • Glucose levels decreases back to the normal range
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A1. ​Causes and treatment of Type I and Type II diabetes.

-Type I diabetes 
  • Is an autoimmune disease characterized by the inability of the pancreas to produce insulin. The insulin producing B-cells of the pancreas are attacked and destroyed by one's own immune system
  • This type of diabetes usually develops in children, but can occur at any age
  • Therefore, the body loses the ability to take up glucose into its cells and convert glucose into glycogen. 
  • People that have type I diabetes must take insulin shots or injections 

-Type II diabetes
  • Occurs when the insulin receptors on certain body cells lose their ability to process or respond to insulin
  • Pancreas still produces insulin
  • Type II diabetes is usually a result of obesity, age, lack of exercise and genetic predisposition
  • Type II diabetes is usually considered late onset as it usually occurs later on in life
  • Insulin injections are not needed. Diabetes II can be treated by lifestyle and diet changes
  • Most common form of diabetes 
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U2. Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.

  • Thyroxin is a hormone secreted by the thyroid gland of the endocrine system. 
  • Thyroxin contains iodine: therefore, prolonged deficiency to iodine in the diet prevent the production of thyroxin
  • Thyroxin is important in the regulation of the body's metabolic rate
  • The body's metabolic rate is the amount of energy a body uses at rest; combination of the catabolic and anabolic reactions
  • Since thyroxin causes an increase in the body's metabolic rate, there is an increase in oxygen consumption and the hydrolysis of ATP; thereby causing an increase in the body's temperature
  • Increase in thyroxin stimulates the breakdown of lipids and the oxidation of fatty acids
  • Thyroxin also stimulates carbohydrate metabolism, including the uptake of glucose and the breakdown of glycogen into free glucose
  • In a regular person, if the bodies temperature drops, a release in thyroxin will stimulate heat production causing the body's temperature to rise
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U3. ​Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.

  • Leptin is a hormone made by adipose cells that helps to regulate energy balance by inhibiting hunger
  • Leptin acts on the receptors in the arcuate nucleus of the hypothalamus to regulate appetite in order to achieve energy homeostasis
  • The concentration of leptin in the blood is controlled by food intake and the amount of adipose tissue in the body
  • If the amount of adipose tissue in an individual increases, then their concentrations of leptin also increases, leading to long term suppression of appetite and reduced food intake
  • In obese individuals a decreased sensitivity to leptin can occurs, resulting in an inability the recognize when they are full
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U4. ​Melatonin is secreted by the pineal gland to control circadian rhythms.

  • Melatonin is a hormone made by the pineal gland, a small gland in the brain
  • The secretion of melatonin by the pineal gland is controlled by cells in the hypothalamus
  • Light exposure to the retina is relayed to the suprachiasmatic nucleus (SCN) of the hypothalamus. These fibres from the hypothalamus relay a message to the nerve of the spinal cord which is relayed back to the pineal gland to release melatonin. 
  • Melatonin helps control your sleep and wake cycle (circadian rhythms) 
  • Very small amounts of melatonin are found in foods such as meats, grains fruits and vegetables
  • Melatonin levels generally begin to rise in the mid to late evening, remaining high for most of the night, and then drop in the early morning hours
  • Light from the sun can also affect how much melatonin your body produces. During the shorter days of the winter months, your body may produce melatonin either earlier or later in the day than usual. This change can lead to symptoms of seasonal affective disorder (SAD) or winter depression
  • Natural melatonin levels slowly drop with age. Same older adults make very small amounts of it or non at all. 
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S1. ​Annotate diagrams of the male and female reproductive system to show names of structures and their functions.

U5. ​A gene on the Y chromosomes causes embryonic gonads to develop as testes and secretes testosterone.

  • The Y chromosome has a gene called the SRY gene that causes the embryonic gonads to become testes and begin secreting testosterone
  • SRY codes for a protein called TDF that stimulates the expression of other genes located on the Y chromosome that cause testis development
  • Is there are two X chromosomes, the gonads develop as ovaries
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U6. ​Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty.

-Testosterone
  • Secreted in the testes of males or the early stage testosterone-secreting cells that will become testes 
  • Aid in the development and maturation of the male genitalia as a fetus at about 8th 9th week
  • During puberty, testosterone aids in the development of male secondary sexual characteristics such as pubic and facial hair
  • Stimulates production of sperm and promotes the male libido
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U7. Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty.

  • If the SRY gene on the Y chromosome is not present in the embryo, the gonads develop into ovaries
  • Estrogen and progesterone which are secreted by the mother's ovaries and then by the placenta, will cause the female reproductive organs to develop in the absence of testosterone
  • During puberty, estrogen and progesterone cause the development of secondary sexual characteristics in females, including breast development, menstrual cycle. 
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U8. THE MENSTRUAL CYCLE IS CONTROLLED BY NEGATIVE AND POSITIVE FEEDBACK MECHANISMS INVOLVING OVARIAN AND PITUITARY HORMONES.
TITLE TEXT. 

-FSH 
  • Produced and secreted by the anterior pituitary gland
  • Stimulates the growth of the follicles in the ovaries to create a mature Graafian follicle
  • Promotes the thickening of the follicle wall
  • Stimulates the secretion of the hormone estrogen

-LH
  • Produced and secreted by the anterior pituitary gland
  • Triggers the release of the egg (ovulation)
  • Stimulates the growth of the corpus luteum
  • Stimulates the secretion of hormone estrogen and progesterone

-Estrogen
  • Produced by the developing follicles in the ovaries and the corpus luteum
  • Promotes the thickening of the uterine wall and the growth of blood vessels, in preparation of egg implantation 
  • Inhibits FSH and LH when the estrogen levels are high. This would prevent the development and release of another egg

-Progesterone
  • Produced by the ovaries and the corpus luteum
  • Helps maintain the thickening of the uterine wall for egg implantation
  • Inhibit the production of FSH and LH
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