B3.2 Flashcards
What type of signal is used in the endocrine system?
Chemical
What type of signal is used in the nervous system?
Electrical
What is the transmitter in the endocrine system?
Hormones in bloodstream
What is the transmitter in the nervous system?
Nerve cells
What is the speed of response in the endocrine system?
Slower
What is the speed of response in the nervous system?
Very fast
What is the duration of response in the endocrine system?
Long
What is the duration of response in the nervous system?
Short
Where is adrenaline produced?
Adrenal glands above kidneys
What is the role of adrenaline?
Triggers ‘fight or flight’, increases heart rate and breathing rate, dilates pupils, makes hairs stand up (erect)
Where is thyroxine produced?
Thyroid gland in the neck
What does thyroxine control?
Metabolic rate, growth
What happens if thyroxine levels are low?
Hypothalamus releases TRH, pituitary releases TSH (thyroid stimulating hormone) → thyroid makes more thyroxine
What happens when thyroxine levels return to normal?
TRH and TSH secretion inhibited (negative feedback)
What does testosterone do?
Produced by testes, develops sperm and secondary sexual characteristics in males
What does oestrogen do?
Produced by ovaries, develops secondary sexual characteristics in females
What does oestrogen do in the menstrual cycle?
Thickens uterus lining for implantation
When do oestrogen levels peak?
Day 10
What does FSH (follicle stimulating hormone) do?
Matures egg in ovary
What does LH (luteinising hormone) do?
Stimulates ovulation
What causes FSH and LH to increase?
Drop in oestrogen levels
When does ovulation occur?
Day 14 – when FSH and LH peak
What does progesterone do?
Maintains thick uterus lining
What hormones does progesterone inhibit?
FSH and LH
When does progesterone peak?
Day 17 (3 days after ovulation)
What happens if egg is not fertilised?
Progesterone drops, uterus lining sheds over 5 days (period)
What is menopause?
When a woman no longer has periods (around age 50–55)
What hormones do oral contraceptives (pill) contain?
Progesterone and oestrogen - inhibit production of FSH so egg doesn’t mature
How do contraceptive implants work?
Release progesterone slowly - stop egg release, thicken cervical mucus - sperm cannot swim through
How do condoms work?
Barrier method -sperm can’t reach egg, protects from STIs
What is a vasectomy/female sterilisation?
Sperm tubes/oviducts (fallopian tubes) cut to stop fertilisation (almost 100% effective) but can be irreversible
What does the copper IUD do?
T shaped device implanted in uterus copper kills sperm and stops implantation (lasts 10+ years)
What do fertility drugs contain?
FSH and LH to mature and release egg
What happens in IVF?
FSH and LH given (eggs mature) → eggs collected and fertilised by fathers sperm in a lab→ embryos implanted into uterus
How long does the menstrual cycle usually last?
28 days
How effective are oral contraceptives (pill)?
More than 99% effective if taken properly (daily)
What are the side effects of oral contraceptives (the pill)?
Mood swings
Weight gain
How effective are contraceptive implants?
More than 99% and will not need to take every day
How effective are physical barrier methods (condoms etc)?
Over 99% - can be made more effective w spermicidal agents but some ppl allergic
What is the downside of copper IUD?
Must be fitted by doctor and a small chance of ectopic pregnancy
What is one form of contraception that doesn’t require anything medical?
Abstinence - don’t participate in sexual activity
Reasons for infertility?
Bad sperm quality or quantity, lack of FSH to mature egg, blocked sperm ducts, inability to release eggs by ovary
Downsides of IVF
Very expensive
Could end up with twins or more
Or no pregnancy at all
What is phototropism?
Plant’s growth response to light
What is gravitropism/geotropism?
Plant’s growth response to gravity
Where does auxin accumulate in phototropism?
Shaded side of the shoot
What does auxin do in shoots?
Stimulates cell growth – shoot bends toward light
What does auxin do in roots?
Inhibits growth on lower side – root grows downward
How can you investigate phototropism?
Use a cardboard box with light from one side
How can you investigate gravitropism?
Use a petri dish attached vertically to a wall
How do auxins work as weed killers?
Cause uncontrolled growth in broad-leaved weeds but not in grass
How is auxin used in rooting powder?
Encourages cuttings (from original plant) to grow roots quickly
How is auxin used in tissue culture?
When cells from plant are placed in growth medium contain in nutrients -auxin stimulates formation of roots and shoots
What does gibberellin do?
Stimulates seed germination, flowering, and fruit growth
How is gibberellin used in brewing?
Ends seed dormancy for barley - germination rate increase to make malt
How is gibberellin used for flowering?
Used regardless of day length or temperature - bigger flowers
How is gibberellin used for fruit size?
Increases size of seedless fruit
What is ethene used for?
Ripening fruit and controlling cell division
Why is fruit picked unripe?
To avoid bruising – ripened later using ethene
How do auxins create positive phototropism (growth towards light)?
- Plant exposed to light on one side
- Auxin moves to shaded side of shoot
- then stimulates cells on to grow more on that side
- means shoot bends towards the light
Beneficial - plants gets more light - photosynthesis occur at faster rate
How does auxin create negative gravitropism in shoots(growth away from gravity)?
If shoot is horizontal:
- auxin moves to lower side
- stimulates cells to grow more here
- makes shoot bend and grow away from ground
beneficial - light levels likely to be higher further away from ground
How does auxin create positive gravitropism in roots (growth towards gravity)?
- Auxin moves to lower side
- cells of root grow more on side w less auxin: cells grow on upper side
- root bend and grows down
beneficial - more water & nutrients lower down & provides stability for plant
