topic 7

• Endocrine system


  - made up of endocrine glands that release hormones into the blood stream

  - effects of hormones are slower but they act for longer, so the endocrine system is used to control functions that do not need instant responses

  
• Gland

  A group of cells that produces and releases one or more substances (secretion)
• Pituitary gland


  - 'master gland'

  - hormones such as FSH and LH
• Thyroid

  - produces thyroxine

  - this controls metabolic rates and affects growth
• Pancreas

  - produces insulin

  - this regulates blood and glucose levels
• Adrenal glands


  - produces adrenaline
• Testes

  - males

  - produce testosterone
• Ovaries

  - females

  - produce oestrogen
• Hormone

  - a chemical substance produced by a gland

  - carried by the blood and can circulate around the whole body
• What do hormones do?

  - chemicals that transmit information from one part of the organism to another and bring about a change (a signal that triggers a response)- alter the activity of specifictarget cells, tissues or organs- make people kinda weird
• Adrenaline and its effects (6) potentially

  - known as the 'fight or flight' hormone produced where the body may be in danger

  - increase in heart rate and breathing rate - ensures glucose and oxygen can be delivered to muscle cells (CO2 can be taken away) at a faster rate

  - diverting blood flow towards muscles and away from non-essential parts of the body such as the alimentary canal - ensures an increased supply of the reactants of respiration

  - dilation of the blood vessels inside muscles- ensures more blood can circulate through them (again, supplying more glucose and oxygen)

  - breaking down of stored glycogen to glucose in the liver and muscle class, with glucose released by the liver being transported to active muscle cells - ensures a higher blood glucose concentration for increased respiration in muscle cells (more ATP for movement)

  - dilating pupils to allow as much light as possible to reach retina - more information can be sent to the brain
• Why must blood sugar level be controlled?

  - blood glucose concentration must be kept within a narrow range (example of homeostasis)

  - too high: cells of the body lose water by osmosis (plasmolysis, hypertonic)

  - too low: insufficient glucose for respiration, leading to a coma or even death
• What controls the blood glucose levels?

  pancreas and liver
• What happens when the blood glucose concentration gets too high?

  - cells in the pancreas detect the increased blood glucose levels

  - pancreas produces insulin, secreting it into the blood

  - insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen (polymer of glucose)

  - reduces the concentration of glucose in the blood back to normal levels

  - pancreas stops secreting insulin
• What happens when the blood glucose concentration gets too low?

  - cell in the pancreas detect the decreased blood glucose levels

  - pancreas produces glucagon

  - glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood

  - increases the concentration of glucose in the blood

  - pancreas stop secreting glucagon
• Testosterone


  - produced in the male testes

  - main sex hormone in males

  - responsible for the development of secondary sexual characteristics in males

  - stimulates sperm production
• Progesterone

  - produced in the female ovaries

  - it is responsible for maintaining the endometrium during pregnancy
• Oestrogen

  - produced by the female ovaries

  - main sex hormone in females

  - responsible for the development of secondary sexual characteristics in females and regulating the menstrual cycle
• Negative feedback mechanisms


  - this in homeostasis help to maintain conditions in the body within an optimal narrow range; any movement away from ideal conditions results in changes occurring which bring them back

  - thyroxine and control of the basal metabolic rate is an example of negative feed back

  
• Thyroxine

  - release from the thyroid gland (neck)

  - stimulates the basal metabolic rate (BMR); rate at which chemical reactions occur in the body when it is at rest

  - thyroxine levels controlled by negative feedback with levels of TSH released from the pituitary gland
• TSH


  thyroid stimulating hormone
• If the level of thyroxine is too high

  - the release of TSH is inhibited, so less thyroxine is released from the thyroid gland
• If the level of thyroxine falls below a normal level

  - released of TSH from the pituitary gland is increased which stimulates the thyroid to release more thyroxine
• Hyperthyroidism


  - caused by an overactive thyroid gland secreting too much thyroxine into the bloodstream which causes an increase in BMR and protein synthesis
• Hypothyroidism


  - caused by an under active thyroid gland secreting too little thyroxine into the bloodstream

  - can lead to nerve and heart problems, and death
• Stages of the menstrual cycle

  - average 28 days

  - menstruation

  - the lining starts the thicken

  - ovulation

  - lining maintained to ready to accept a fertilised egg

  
• Menstruation


  Loss of lining form the uterus, occurs at the start of the cycle if no fertilisation has occurred
• Ovulation


  Occurs around the middle of the cycle (day 14~) egg travels down the oviduct towards the uterus
• FSH


  - follicle-stimulating hormone

  - released in pituitary gland

  - targets ovaries

  - stimulates the follicle to grow

  - ovum to mature

  - stimulates oestrogen release
• Oestrogen (role in menstrual cycle)

  - release in ovaries

  - targets uterus (endometrium)

  - build the endometrium

  - stimulates and triggers release of LH

  - stops the release of FSH
• LH


  - released in pituitary gland

  - targets ovaries

  - a surge around day 14 causes ovulation

  - causes follicle to rupture and the ovum to be released

  - inhibits release of oestrogen

  - stimulates the follicle to grow into corpus luteum for the production of progesterone
• Progesterone (role in the menstrual cycle)

  - produced in corpus luteum (placenta takes over during pregnancy)

  - targets uterus

  - stops the endometrium from breaking down, maintains it

  - inhibits the release of LH and FSH
• Hormone level graph LH & FSH

  
• Hormone level graph oestrogen & progesterone


  - oestrogen levels rise from day 1 to peak just before day 14

  - progesterone stays low from day 1 - 14 and starts to rise after ovulation

  
• Abstinence


  - natural method

  - 100% safety guaranteed trust
• Rhythm method


  - natural method

  - avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs

  - exact time of ovulation happens can be worked out by monitoring body temperature and quality of cervical mucus

  - least reliable L
• IUD/ IUS


  - chemical

  - small device fitted inside the uterus

  - releases sex hormone which thicken the mucus produced in the cervix, making it difficult for sperm to swim into the uterus

  - thins the lining of uterus (more difficult for fertilise egg to implant)

  - interferes with the passage of sperm through the uterus, acts as a barrier method kind of
• Contraceptive pill, implant, injection

  - chemical

  - may contain just progesterone but also a mixture of oestrogen

  - very effective when taken regularly

  - hormones can also be delivered from a small skin implant or inject (lasts several months) removes risk of forgetting pill

  - mimics the hormone levels during pregnancy

  - raising levels of progesterone and oestrogen the uterus lining is maintained and development of egg cell is prevented (no egg released)
• Condom


  - barrier

  - latex sheath worn over the penis

  - prevents sperm entering the vagina

  - protects against STIs

  - massive dub
• Femidom


  - latex sheath inserted into the vagina

  - no entry of sperm