B5

Question 1

What is homeostasis?

Answer 1

Homeostasis is an organism’s ability to regulate and maintain internal conditions so enzyme activity can take place at optimum levels.
E.G, blood glucose conc, water levels.

Question 2

Nervous System

Answer 2

1) A receptor detects a change in environment (stimulus).
2) An electrical signal travels to the spine through the sensory and relay neurone.
3) The signal travels across the synapse via a neurotransmitter chemical.
4) Signal can then go to the brain where the brain can make the conscious decision to act.
5) Signal then travels to the effector (muscle/gland) via relay and motor neurone.

Question 3

Reaction Times Practical

Answer 3

1) Drop ruler between person’s finger and thumb
2) Measure distance fallen before caught
3) Repeat 10 times and calculate mean

Independent variable: Stimulant (increases neurotransmission)
Depressant (decreases neurotransmission)

Question 4

What is a reflex arc?

Answer 4

A reflex arc is where the signal bypasses the brain and goes straight to the spine to the receptor.

Question 5

What is the endocrine system?

Answer 5

System of glands that secrete hormones to send signals to effectors, transported via blood.

Question 6

Which glands/organs are involved in the endocrine system?

Answer 6

Pituitary gland; ‘master gland’ sends signals to all other glands.
Thyroid; controls growth and metabolism.
Adrenal Glands; releases adrenaline, which increases heart rate and breathing rate.
Pancreas; releases insulin and glucagon
Ovaries; releases eggs and secretes hormones
Testes; produces sperm

Question 7

What happens if thyroxine levels are too low?

Answer 7

Thyroid releases thyroxine which controls metabolism; if thyroxine levels are too low, the hypothalamus in brain releases TRH which causes pituitary gland to release TSH which causes thyroid to release more thyroxine.

Example of negative feedback.

Question 8

What happens when blood glucose levels are too high?

Answer 8

Pancreas secretes insulin, causing glucose to move out of bloodstream into cells to be used for respiration.
Excess glucose is converted into glycogen as an energy store, which is done by the liver

Question 9

What happens when blood glucose levels are too low?

Answer 9

Pancreas secretes glucagon, causes liver and muscles to convert glycogen back into glucose.

Example of negative feedback.

Question 10

What is the difference between type I and II diabetes?

Answer 10

Type I: Pancreas cannot produce (enough) insulin, insulin injections are needed.
Type II: cells don’t absorb glucose as they should, obesity increases risk of developing.

Question 11

Menstrual Cycle

Answer 11

1) FSH released from the pituitary gland, causes an egg to mature and ovaries to produce oestrogen.
2) Oestrogen causes uterus lining to thicken, and inhibits FSH until the next cycle so no eggs are matured. Also causes the pituitary gland to secrete LH.
3) LH causes an egg to be released; a sperm cell can fertilise this whilst in the oviducts.
4) Progesterone is secreted by the ovaries which maintains the uterus lining.

Question 12

Types of contraception

Answer 12

-FSH inhibiting pills
-Progesterone implant/injection; eggs are released
-Condom/Diaphragm; sperm cannot enter
-IUD; stops eggs embedding in uterus lining.
-Avoid sex after release of eggs
-Clamping oviduct/vasectomy

Question 13

Fertility Treatments

Answer 13

-FSH/LH injections - simple
-IVF - hard/expensive!
1) Eggs are collected after being induced with LH to be fertilised in a lab with the father’s sperm.
2) Viable embryos are inserted back into the uterus

Disadvantages; success rate is very low, can be emotionally distressing, ethical concerns (one of both parents may not want it to happen), can potentially cause multiple embryos to develop.