3-6 Markers Flashcards
Explain how an impulse is transmitted from one neurone to another (4)
Synapse
• Synapse is a gap between two neurones
• Neurotransmitters
• Diffuse across the synapse
• Electric impulse transmitted down next neurone
You see a car and need to jump out of the way.
Describe how the reflex arc keeps you safe from danger (6)
• Stimulus is the light reflecting from car
• Receptor in eve detect light
• Electrical impulse transmitted through sensory neurone
• Neurotransmitters cross synapse - a gap between two neurones
• Relay neurone
• Motor neurone
• Effector is muscle
• Response is muscles contract - jump from road
• Bypasses brain to speed up reactions
Explain how convex and concave lenses can be used to correct vision (6)
Concave / diverging lens:
• Corrects short-sightedness
• Lens bends light away from concave lens onto the cornea
• lens then refracts light and focuses light onto retina
Convex / converging lens:
• Corrects long-sightedness
• Lens bends light from the convex lens onto the cornea
• lens then refracts light and focuses light onto retina
Describe how hormones control blood glucose levels (6)
Lowering blood glucose levels:
• Pancreas secretes insulin
• Converts glucose to glycogen
• Increases glucose absorption into cells and increases rate of respiration
• Glycogen stored in liver
Increasing blood glucose levels:
• Pancreas secretes glucagon
• Glucagon converts glycogen in liver to glucose
Explain how type-1 and type-2 diabetics control their diabetes (6)
Type-1 diabetics: Produce no insulin
• Insulin injections to lower glucose blood concentration
• Insulin converts glucose to glycogen (stored in liver)
• Exercise increases rate of respiration - lowers glucose conc.
• Low sugar diet prevents high blood glucose concentration
Type-2 diabetics: Produce insulin
• Exercise
• Low sugar diet
Explain how adrenaline effects organs for flight or fight (6)
Heart:
• Increases heart muscle contractions & higher blood pressure
• Increased oxygen & glucose to cells
• Increased respiration & more energy released
Liver:
• Converts glycogen to glucose
• Increases glucose levels in blood
Blood vessels:
• Widen blood vessels to muscles
• Narrows blood vessels to non-vital organs
• Increases blood supply to muscles
Explain how negative feedback controls thyroxine levels in the blood (6)
Low thyroxine levels in the bloodstream:
• Stimulate the hypothalamus to release TRH
• This causes the pituitary to release TSH
• Causing the thyroid releases more thyroxine
(H) Effects of Thyroxine
Normal thyroxine levels in the bloodstream:
• Inhibit TRH release from the hypothalamus
• Inhibiting the release of TSH from the pituitary
• Thyroid releases less thyroxine
Explain how ADH regulates water reabsorption in the collecting duct (6)
• Hypothalamus detects blood water levels
• Pituitary gland secretes ADH
When water levels are low / dehydrated:
• ADH levels increase
• Permeability of collecting duct membrane increases
• More reabsorption of water • Decreased volume of urine
When water levels are high / hydrated:
• ADH levels decreases
• Permeability of collecting duct membrane decreases
• Less reabsorotion of water
• Increased volume of urine
Explain how vasodilation and vasoconstriction help control body temperature (6)
Vasoconstriction:
• Blood vessel to capillaries near skin to narrow
• Restricts blood flow to surface of skin
• Reduces heat loss to surroundings
• Increases bod temperature
(S) Vasoconstriction & Vasodilation
Vasodilation:
• Blood vessel to capillaries near skin widen
• Increases blood flow to skin
• Increases heat loss to surroundings
• Decreases bod temperature
Explain how hormones control the menstrual cycle (6)
• FSH released by pituitary gland causes egg follicle to grow and mature
•Oestrogen released from ovary
• Oestrogen causes uterus lining to thicken
• Oestrogen inhibits FSH / causes LH to be released
• LH spike on day 14
• LH causes ovulation / egg to be released from ovary
• Progesterone maintains uterus lining
• If fertilisation progesterone levels stay high to maintain uterus lining
• If no fertilisation progesterone levels decrease
• Uterus lining breaks down - menstruation
Explain how the hormones in the contraceptive pill prevent pregnancy (4)
• Oestrogen and progesterone in combined pill
• Oestrogen inhibits FSH production
• Egg follicle doesn’t grow and mature
• No LH spike
• No ovulation / egg not released
Contraceptive Pill
• Progesterone causes mucus around cervix
• Reducing sperm ability to enter uterus
• Less sperm and no egg means no fertilisation
Explain which two hormones help the woman produce and release mature eggs (4)
FSH - causes multiple egg (follicles) to grow and mature
• LH - causes ovulation / egg release
Describe how the mature eggs are used in IVF treatment so that the woman may become pregnant (4)
Multiple eggs removed from ovary
• Male provides sperm sample
• Sperm and eggs are mixed
• Egg is fertilised by sperm
• Embryos incubated
• Multiple embryos placed into uterus of mother
Describe how pre-implantation genetic diagnosis (PGD is used to screen embryos for genetic disease (4)
PGD screens embryo for genetic diseases
• during IVF
• Cell removed from fertilised embryos
• Cell’s DNA screened
• If faulty gene is found - embryo destroyed & not used
Describe how pre-implantation genetic diagnosis (PGD is used to screen embryos for genetic disease (4)
• PGD screens embryo for genetic diseases
• during IVF
• Cell removed from fertilised embryos
• Cell’s DNA screened
• If faulty gene is found - embryo destroyed & not used