B 3.2 Endocrine System Flashcards
What are hormones
Where are they made, where secreted
Where do they cause a response?
Big question is how do hormones travel and cause an effect?
Hormones are CHEMICAL MESSENGERS. They are made in ENDOCRINE GLANDS and secreted in blood, where they travel in plasma and travel all around the body. However they only cause a response in Target hormones by binding the specific receptors for the hormone, found in the membrane / cytoplasm of the cells in the target hormone. These cells are the TARGET CELLS. Once binded with these cells, a response is stimulated…
What is homeostasis ?
Maintaining of internal environment / conditions in body
Where are the various glands found
Thyroxine , testosterone, progesterone oestrogen, insulin, others
Hypothalamus and Pituitary gland, the hormonal centre, produces hormones that REGULATE THE PRODUCTION OF OTHER HORMONES.
- Thyroid gland in neck produces thyroxine (actually takes amino acid tyrosine, which combines with iodine, to make thyroxine )
- pancreas produce insulin, and adrenal glands (ABOVE KIDNEY) produce adrenaline
- ovaries produce oestrogen progesterone
Testes testosterone
So what is the endocrine system then?
Collective term for all the glands and hormones they produce , which in turn coordinates body processes with the nervous system.
Similarity and differences between hormones and nerves?
4 differences need to know
Similar
- both send messages around the body to stimulate a response about changes in internal/ external environment
Differences
- speed, how they transmitted, duration of response, area targeted
- nerves communicate very fast, hormones slow
- nerves act very fast, hormones can act fast ish but mostly slow (think puberty)
- nerves messages are transmitted across an electrical impulse of the axon of neurone, hormone does their hormone secreted in blood
- nerves target a specific area, but hormones a more wide range
- finally nerve do ELECTRICAL signals, Hormone CHEMICAL
What is a negative feedback loop? Example
Negative feedback loop is when a change from conditions of the set point is detected by receptor cells and this is corrected by a mechanism. Once the change is corrected, the mechanism is switch off, like heating system. Things like thermoregulation and water balance are used with negative feedback loops.
What is thyroxine used for , how is negative feedback loop control levels of thryroxine in body?
Thyroxine is used to control the metabolic rate- the rate at which energy is transferred from food to chemical in our body,
When the HYPOTHALAMUS detects energy is needed, the hypothalamus CAUSES the Pituitary gland to release hormone TSH (thyroxine stimulating hormone). This stimulates the thyroid gland to produce and release thyroxine, which increases the metabolic rate, allowing cells to transfer more energy. Once the hypothalamus detects the cells have enough energy, it stops the pituitary gland from producing more tsh which in turn stops the thyroid gland from producing thyroxine.
However when too much energy being produced- it stops.
What does the hormone adrenaline do and how is that controlled?
Adrenaline prepares you for fight or flight response. This is detected by stress levels.
When hypothalamus detects stress levels are high, it sends signals to the adrenal glands to produce adrenaline, which does a range of things:
- it increases the rate of respiration, which allows you to transfer ATP more. (Bunds to liver cells, which stimulates it to break down glycogen to glucose with glucagon …)
- it increases rate of breathing and heart rate to cope with the increase of respiration (binds to receptor cells in heart)
- diverts blood away from not vital organs (like digestive system) to vital organs and mainly MUSCLES.
when hypothalamus detects that stress levels are normal again, it stops sending signals for the adrenal gland to produce adrenaline, and so the body systems return to previous state.
Not necessarily a negative feedback loop
What is normal body temperature, what happens if it goes below 35 or above 42?
37
Below 35 causes hypothermia, causing enzyme reactions to happen too slowly and so enough energy is not produced, and cells begin to die.
Above 42 is HYPERTHERMIA (more movement= hyper). Amino acids in chain in enzymes begin unravel, changing shape of active siege causing enzymes to denature. Reactions stop happening, and you die.
How is temperature controlled (in terms of receptor cells etc)
The thermoreguslotry centre in YOUR BRAIN, is responsible for regulation.
- it relies on receptor cells in skin and internal receptor cells in blood to determine what is happening, monitoring external and internal temps.
Change is detected, body fix, mechanism removed, negative feedback, maintains homeostasis…
Hypothalamus btw
What happen if body too cold
4 things
- Body stops sweating (so no more energy can be transferred from Body to surroundings when sweat evaporates)
- hairs on skin raise- all the hairs raise which traps a layer of air between them, insulating the body -making you warm
- vasoconstriction happens- blood vessels SUPPLYING CAPILLARIES near the skin constrict ( marrow) , REDUCING BLOOD FLOW AND So less heat is lost to surroundings.
- Shivering takes place: this is when muscles contract and relax really quickly, making your cells respire more for energy to do so, and since respiration exothermic reaction - it transfers energy by heating .
What happens if body too warm?
3 things, reverse of cold.
- sweat glands produce sweat (mixture if water urea salts). When this gets evaporated, what is transferred from body to surrounding schooling you down
- Hairs lower, so insulating layer of air goes away
- vasodilation : when blood vessels supplying capillaries widen, increasing blood flow, and therefore more heat is lost by RADIATION.
- shivering stops
Hormones for reproduction and what do they do?
Testosterone for males, stimulates speem production and importwnt for development of male reproductive system such as enlargement of penis, growth etc
Oestrogen for females, involved in menstrual cycle and involved similarly for growth of female characteristics, such as breast development
Menstrual cycle
How does it work simply 4 stages
What is OVULATION, when does this happen
How long is the menstrual cycle?
1) menstrual cycle is 28 days. Day1 when it starts, 1-4 the uterus lining breaks down and is released
2) Uterus lining thickens in anticipation if a fertilised egg. At the same time, an egg begins to mature in the ovaries. Day 4-14
3) the egg is fully matured and released into the uterus at 14 days. This is ovulation
4) if the egg is fertilised until day 28, then women is pregnant. The egg is protected and treated with oxygen and nutrients
If the egg is not fertilised, then the uterus lining breaks down , and exits with the egg… day 1 starts again….
How do hormones control the mesnrtual cycle (full)
So what happens at the end, how does the cycle restart? (What hormone)
1) FSH (secreted by pituitary gland- all stimulating ones in there). Is secreted. This causes a follicle (egg) to start maturing. FSH ALSO stimulates the production of oestrogen .
2) Oestrogen (made and secreted in ovaries) causes the uterus lining to thicken and grow. It also stimulates (pituitary to ) production of Luteinising hormone , but INHIBITS production of FSH- so only one egg is released per cycle.
3) LH stimulates ovulation at day 14. Basically once LH levels hit a peak in the middle of the cycle, this happens, LH also therefore indirectly stimulates progesterone production, because after the egg is released, Progesteron there to keep the uterus lining…
4) Progesterone (made and secreted by ovaries) maintains uterus lining for the remainder 14 days. It also inhibits production if LH and FSH. The progesterone comes from the empty folicile, and this follicle gets released because if a peak of LH, this is why LH indirectly stimulates progesterone production.
5) IF FERTILISED EGG, PROGESTERONE LEVELS REMAIN HIGH TO MAINTAIN UTERUS LINING. ONCE PROGESTERONE LEVELS DROP WHEN UTERUS EXITS, FSH COMES BACK, RESTARTING THE WHOLE CYCLE AGAIN.
