Topic 7 - Animal coordination, control and homeostasis Flashcards
Describe the endocrine system
Its response is long-lived and slow. It uses chemical messages (hormone are chemical messages carried in the blood). Hormones are produced in endocrine glands.
Describe adrenaline
It is a hormone produced in the adrenal gland. It is NOT controlled by negative feedback. It prepares the body for fight or flight, including:
-Causing the heart to beat faster and harder = increased heart rate
-Increased blood pressure
-increased blood flow to the muscles
-Raised blood sugar levels by stimulating the liver to change glycogen into glucose
This causes more glucose to be delivered to the muscles and more energy being released by respiration in the muscles.
This allows the body to prepare for action in situations where a quick response may be needed.
Explain how thyroxine controls metabolic rate
-Low levels of thyroxine stimulates production of TRH in hypothalamus
-This causes the release of TSH from the pituitary gland
-TSH acts on the thyroid to produce thyroxine
-When thyroxine levels are normal thyroxine inhibits the release of TRH and the production of TSH
Describe the stages of the menstrual cycle
The menstrual cycle is a cycle of changes in a woman’s reproductive system that takes about 28 days.
It begins with menstruation which lasts around 5 days. This is the shedding of the uterus lining and the unfertilised egg. After menstruation the uterus lining rebuilds.
Around day 14, ovulation takes place where an egg is released from the ovary. After ovulation, the uterus lining remains thick.
Describe FSH
It is a hormone made in the pituitary gland
It stimulates one egg cell to develop with a follicle (fluid-filled sac which contains an unfertilised egg cell inside the ovary).
It stimulates the production of oestrogen.
Describe Oestrogen
It is a hormone produced in a follicle in the ovaries.
It stimulates the rebuilding of the uterus wall.
It stimulates LH and inhibits FSH.
Describe LH
It is produced in the pituitary gland.
It stimulates follicles to burst and release ovum (resulting in ovulation)
It stimulates progesterone
Describe progesterone
It is produced in a corpus luteum (what is left of a follicle after ovulation).
It maintains the uterus lining
Describe the contraceptive pill.
The pill must be taken regularly (the same time every day) in order to be effective.
There is a mixed or progesterone-only pill.
The mixed pill contains oestrogen and progesterone.
The high oestrogen levels inhibit FSH so no eggs mature.
The lining also stops developing and the mucus in the cervix becomes thick so sperm cannot move through.
Describe methods of hormonal contraceptive other than the pill
Contraceptive patches contain oestrogen and progesterone.
Contraceptive implants, injections and IUS (hormonal coil) release progesterone to inhibit the maturation and release of eggs.
Evaluate hormonal contraception
Pros:
-IUS works for 3-8 years, Implant works for 3 years, shots work for three months
-Oral contraceptives are more than 99% effective if taken correctly and can reduce the risk of certain ovarian and endometrial cancers.
Cons:
-Doesn’t protect against STIs
-May not be as effective when taken
with certain medications
-May delay normal cycle
-Pill must be taken at the same time daily
-Possible side effects such as changes in weight, mood and increased blood pressure.
Describe non-hormonal contraceptives
-Physical barriers that prevent the sperm reaching an egg like condoms and diaphragms
-IUDs (copper coil) prevent the implantation of an embryo
-Spermicides kill or disable sperm
-Abstaining from sex (especially when an egg is most likely to be in the viaduct, such as after ovulation)
-Surgical sterilisation
State some drawbacks of non-hormonal contraceptives
-Condoms sometimes tear or rip
-Diaphragms need to be put in just before sex and left in several hours afterwards
-IUDs need to be fitted by a health professional and there is a small risk of causing an ectopic pregnancy
-Some people can have allergic reactions to spermicidical agents
-If the timings are not accurate when abstaining the chance of pregnancy is high.
-Surgical methods cannot be reversed, and is considered permanent
What are the benefits of non-hormonal contraceptives?
-Condoms are easy and quick to use and can also prevent STDs
-An IUD can remain in position for up to 10 years
-Spermicidal agents can be added to other physical barriers such as condoms
Explain the use of hormones in clomifene therapy
A drug is injected into a person to increase the concentration of FSH and LH in the blood. It’s useful for women who rarely or never release an ovum during their menstrual cycle.
Explain the use of hormones in In-Vitro Fertilisation
A woman is given LH and FSH in order to mature multiple eggs, These are extracted and mixed with sperm in a petri dish in order to form embryos. The embryo is then implanted into the uterus to develop.
Explain the importance of thermoregulation
Thermoregulation allows us to maintain a constant internal body temperature.
The optimum internal body temperature is 37℃. Temperatures away from the optimum may effect enzyme activity and cell functions, including: growth, replication and controlled cell death.
Explain the importance of osmoregulation
Osmoregulation is the control of water levels and mineral ions int he blood.
This is necessary to keep the concentrations the same inside the cells as around them. This stops too much water entering or leaving them by osmosis.
If the water concentration is too high outside, water enters the cell by osmosis and they may burst.
If it’s too low outside, water will leave by osmosis and the cells may shrivel.
Explain how thermoregulation through sweating takes place when the blood temperature is too high
The change is detected by the hypothalamus.
In response, sweat is produced from sweat glands in the dermis layer of the skin onto the epidermis. The sweat evaporates, transferring heat energy from the skin to the environment.
Explain how thermoregulation through vasodilation takes place when the blood temperature is too high
The change is detected by the hypothalamus.
In response, vasodilation causes blood vessels to expand, transferring heat energy from the skin to the environment.
Explain how thermoregulation through shivering and piloerection takes place when the blood temperature is too low
The change is detected by the hypothalamus.
In response:
-Rapid muscle contractions release heat energy and we shiver
-Erector muscles in the dermis contract to trap gas and stop heat loss, this raises the skin hairs, resulting in hairs standing on end (piloerection)
Explain how thermoregulation through vasoconstriction takes place when the blood temperature is too low
The change is detected by the hypothalamus.
In response, vasoconstriction causes blood vessels to narrow in order to prevent the transfer of heat energy from the skin to the environment, so that less heat is lost.
Explain how the hormone insulin controls blood glucose concentration
When glucose level is too high, the pancreas causes insulin to be secreted into the blood. This results in the liver converting glucose into glycogen. This causes the glucose level to go down.
Explain how blood glucose concentration is regulated by glucagon
When glucose level is too low, the pancreas causes glucagon to be secreted into the blood. This results in the liver converting glycogen into glucose. This causes the glucose level to go up.
