[BIO] Chapter 13 - Hormone

© Hee Xin Wei (Copyrighted) Topic 1 3: Hormone

Chapter Analysis FOCUS EXAM WEIGHTAGE •Constitute to around 5% in Paper 2 in the past 5 years •commonly tested in MCQ and structured questions •tested twice in section B in the past 5 years •one of the three chapters under umbrella topic of Co-ordination and Response in Humans •linked to nervous system and homeostasis

hormone insulin and glucagon diabetes Key Concept

hormone •Hormone is a chemical substance, produced by endocrine gland and secreted directly to blood •It is transported by blood to target organ to exert its effect •After they have performed their functions, they are destroyed by the liver. There are 2 types of glands 1.Exocrine glands are glands that secrete their products via ducts eg sweat glands and salivary glands 2.Endocrine glands are glands that secrete their products directly into the bloodstream (our focus) •Some glands are both exocrine and endocrine, eg pancreas, which secretes pancreatic juice via the pancreatic duct, and also secretes the hormone insulin and glucagon from the islets of Langerhans directly into the bloodstream. •Other examples of endocrine glands that secrete hormone is as below: •Pituitary gland secretes antidiuretic hormone (ADH) •Hypothalamus regulates the secretion of some pituitary hormones. •Adrenal gland secretes adrenaline. •Pancreas islets of Langerhans secrete insulin and glucagon. •Testis (in males) secretes testosterone. •Ovary (in females) secretes oestrogen and progesterone.

blood glucose regulation insulin and glucagon 1.When blood glucose level increases beyond the norm, more insulin is released by islets of Langerhans in pancreas to the bloodstream 2.Blood transport insulin to the effector cells which are muscles cells and liver cells 3.Insulin decreases blood glucose concentration by: •Stimulating body cells to increase glucose uptake by increasing permeability of plasma membranes to glucose •Stimulating the liver and muscle cells to store glucose in the form of glycogen •Decreasing glycogen breakdown in the liver •Decreasing the conversion of fatty acids and amino acids to glucose in the liver 1.When blood glucose level falls below the norm, more glucagon is released by islets of Langerhans in pancreas to the bloodstream 2.Blood transports glucagon to the effector cells which are liver cells 3.Glucagon increases blood glucose concentration by stimulating liver cells to: •Convert stored glycogen in liver to glucose •Convert amino acids and fatty acids to glucose •Convert lactic acid into glucose normal blood glucose level

diabetes mellitus •Diabetes mellitus is a condition in which the body does not produce sufficient insulin or does not respond to insulin. •The excess glucose cannot be converted to glycogen and cannot be completely reabsorbed in the kidneys and are excreted in the urine. There are 2 types of diabetes 1.Type 1 diabetes or early onset diabetes develops early in a person’s life. •It is usually genetic. •The islets of Langerhans are unable to produce or secrete sufficient insulin 2.Type 2 diabetes or late onset diabetes develops later in a person’s life. •It is usually due to lifestyle factors such as overweight people are more likely to develop type 2 diabetes. •The target cells, such as the muscle and liver cells, do not respond well to insulin.

diabetes mellitus Symptoms 1.A persistent high blood glucose concentration even a few hours after meal 2.Presence of glucose in the urine as selective reabsorption could not fully absorb all glucose presence in the blood 3.Difficulty of wound healing 4.Excessive urination, excessive thirst and weight loss Treatment •For type 1 diabetes, islets of Langerhans are unable to produce or secrete sufficient insulin, thus the patients have to inject insulin directly into their bloodstream. They also have to ensure that they have a supply of sugary food such a glucose sweets, as their blood glucose can drop too low if they use too much insulin, exercise too much or eat too little. •For Type 2 diabetes, their target cells do not respond to insulin. The patients can control their blood sugar level through diet and lifestyle changes. For example, regulate the carbohydrate content in their diet, regular exercises

Adrenaline nervous control vs endocrine control Key Concept

Adrenaline When faced with danger or stress, we have a fight-or-flight response. no matter which we choose, adrenaline will be secreted by adrenal gland located above the kidney EFFECTS OF ADRENALINE 1.Stimulate liver to increase conversion of glycogen to glucose so more glucose are available for muscle contraction 2.Increased glucose release into blood by liver cells 3.Increased metabolic rate, causing more energy to be released in cellular respiration 4.Increased heart rate and blood pressure to increase oxygen and glucose supply to muscle cells 5.Dilated bronchioles to increase breathing rate and depth, allowing more oxygen to be taken in for cellular respiration 6.Increase the rate of blood clotting 7.Constrict arterioles to the digestive system, so to channel blood supply to important organs such as heart, brain and skeletal muscles 8.Constricts arterioles in skin, causing paleness, so to channel blood supply to important organs such as heart, brain and skeletal muscles. 9.Pupils dilate to enhance vision 10.Contracted hair erector muscles, causing hair to stand and produce ‘goose bumps’

nervous control vs endocrine control Nervous Control Endocrine Control means of coordination within our bodies. a stimulus causes the transmission of a message to effector which carries out the response. Involve nerve impulses which are electrical signals Involve hormones which are chemical substances Impulses are transmitted by neurons Hormones are carried by blood Usually fast responses Usually slow responses Responses are short lived Responses can be both short lived or long lasting Maybe voluntary or involuntary Always involuntary Effect is usually localised Can affect more than one organ