6.6 hormones homeostasis reproduction Flashcards
1
Q
what is the difference between endocrine and exocrine system?
A
- endocrine system secretes products into the bloodstream of the body, and the products remains within the body until it is broken down
- exocrine system secretes products that technically leaves body, out of and onto external surface of epithelium
• examples include sweat glands, and also organs that secrete digestive juices, as intestinal tract is technically not within human body (within mesoderm bounded by ectoderm and endoderm) - most common product of the endocrine system are hormones
2
Q
what are hormones?
A
- can be in form of proteins, steroids, or other organic compounds
- act as chemical messengers, and binds to receptors to trigger responses in target cells
- secreted by endocrine glands, and transported by bloodstream
- can trigger different responses in a wide variety of cells (contrasted against a single source and single target with a single response as seen in the nervous system)
3
Q
what are the hormones that control blood glucose concentration and how do they work?
A
INSULIN
- insulin is a peptide hormone, secreted by β cells of pancreas
- increases glucose uptake in cells, especially in adipose cells and muscle cells
- also signals increased fat synthesis in adipose cells
GLUCAGON
- peptide hormone, secreted by α cells of the
pancreas
- increases blood glucose concentration by signalling cells to either breakdown glycogen (mainly in liver and muscles) or to produce glucose from non carbohydrate sources
- also promotes lipolysis in adipose cells
in tandem, insulin and glucagon are antagonistic hormones, working to regulate blood glucose levels
4
Q
what are the causes of type I diabetes?
A
- type I diabetes: form of diabetes where insufficient amount of insulin produced by pancreas
- caused by autoimmune destruction of β cells in pancreas, exact cause of Type I diabetes unknown, even though scientists suspect this to be due to a combination of genetic and environmental factors
- early onset diabetes, and is normally diagnosed in young children
5
Q
what are the causes of type II diabetes?
A
- type II diabetes arises when cells in body no longer responsive to insulin
- mainly caused by desensitization to insulin secretions due to high levels of insulin secretion in response to a high carbohydrate diet (and is linked to obesity)
- cells that take in glucose from bloodstream (and metabolise them) no longer do so, leading to increased blood glucose levels
- also known as late onset diabetes, and is normally diagnosed in adults
6
Q
how is type I diabetes treated / managed?
A
- having low carbohydrate diet and regular exercise can reduce symptoms of disease
- treatments include immuno-suppressant drugs to prevent excessive damage to pancreatic cells if diagnosed early
- most people rely on regular injections of insulin (normally around meal times) to regulate blood glucose
- in rare occasions, pancreatic and islet cells transplantation may be performed
7
Q
how is type II diabetes treated / managed?
A
- mainly via diet management and with regular exercise
- oral medication of drugs that can lower blood glucose
levels may be prescribed - injections of insulin to sufficient high levels may also be effective
8
Q
what is thryoxin? (where is it from, what’s its purpose?)
A
- thyroxin secreted by thyroid gland to regulate metabolic rate and help control body temperature
- thyroid gland located in neck, under voice box, and secretes many hormones that regulates many biological activities including metabolism, reproduction and growth and development
- 1 such hormone is known as thyroxin (T4)
- increased thyroxin secretion can lead to increases in metabolic rate of an individual, and this can also lead to increased body temperature
- thyroxin release is therefore controlled to regulate metabolic rate and body temperature of a person
- thyroxin contains iodine, and hence iodine is needed in its production in the thyroid
9
Q
what is leptin? (where is it from, what’s its purpose?)
A
- leptin is secreted by cells in adipose tissue and acts on hypothalamus of the brain to inhibit appetite
- high levels of leptin in bloodstream is linked to reduced appetite, and over time helps the body to regulate fat storage levels
- involved in self regulating loop, where people with more fat deposits (adipose tissues) secrete more leptin,
leading to reduced appetites, food consumed and less weight gain (fat stored)
10
Q
how did the testing of leptin on patients with clinical obesity work out?
A
- failed to control disease
- proposed that leptin can help people who are clinically obese to manage their appetite and weight gain
- however, clinical tests of treating humans with leptin injections did not work well in regulating appetite and weight gain
- underlying problem of such people is not due to insufficient leptin produced, but rather gaining resistance to effects of leptin (similar to the case for Type II diabetes)
- hence, leptin treatment usually fails to control the disease
11
Q
what is melatonin? (where is it from, what’s its purpose?)
A
- melatonin is secreted by pineal gland to control circadian rhythms
- pineal gland: pea-sized gland found near center of brain
- melatonin secreted by pineal gland mainly in response to environmental light conditions (darkness)
- animals able to use cyclical changes in levels of melatonin in regulation of circadian rhythm (body clock), where body changes in response to changes in time
- leads to temperature changes throughout the day and night, regulation of sleep cycles, etc
- sleepiness is not directly related to melatonin, there are other factors
12
Q
how is jet lag caused and how is it alleviated?
A
- jet lag: condition where body follows circadian rhythm of different time zones, with different timings of day and night cycle, after travelling long distances
- hence might feel sleepy at hours in day, as body is following a circadian rhythm of the place they were previously at
- suffer from headaches, fatigue and irritability, all associated with a lack of sleep
- taking melatonin at prescribed doses at predetermined times can help body to reset body clock, and help person adapt to the new time zones and sleep better
13
Q
how do embryos become male instead female?
A
- gene on Y chromosome causes embryonic gonads to develop as testes and secrete testosterone
- on Y chromosome, there is a gene known as sex- determining region Y (sry) gene, when expressed produces a DNA binding protein known as sry protein
- sry protein also known as testis-determining factor (tdf)
- protein initiates expression of other genes that lead to male development, including inducing embryonic gonads (organ that produces gametes) to develop into testes (instead of ovaries), and testosterone production, amongst many other traits
- important to note that without stimulation brought about by tdf, body will continue to develop as female
14
Q
what is the effect of testosterone?
A
- testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty
- under effects of tdf (testis-determining factor), gonads develop into testes
- testes start to produce testosterone, which has many wide-ranging effects, including development of male genitalia in fetus
- when male reaches puberty, increased testosterone secretion leads to sperm production in testes
- other secondary sexual characteristics will also develop, like increase in size of penis, growth of pubic hair, deepening of voice as well as increased muscle development
15
Q
what is the effect of oestrogen and progesterone?
A
- oestrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty
- during pregnancy, maternal production of oestrogen and progesterone lead to development of female reproductive organs (including the development of ovaries from the embryonic gonads)
- in males, presence of high levels of testosterone inhibit this development and development of male characteristics will take place instead
- during puberty, secretion of oestrogen and progesterone by ovaries leads to primary sexual characteristic of egg release
- secondary sexual characteristics of enlargement of breasts, growth of pubic hair will also take place
