biology topic 5 Flashcards
what is Homeostasis
the maintaining of a constant internal
environment in the body.
how is homeostasis maintained
Maintained by negative feedback; Opposite response to a
change occurring in your body to bring conditions back the
optimum level.
why is homeostasis important
Ensures enzymes work at optimum conditions
what is Negative feedback
- occurs when there is a change in the body
- the nervous system detects the change
- this stimulates an opposite hormonal response
- this reverses the effect back to homeostasis.
what is positive feedback
- a change starts
- the nervous system detects the change
- then stimulates more hormones to be released to accelerate the
change.
what are Receptor cells
specialised cells that detect a stimulus (changes in the environment).
describe Structure of Nervous system (reflex arc)
Stimuli – change in environment
↓
Receptor – detects changes
↓
Sensory neurone – sends electrical signals TO CNS
↓
CNS - Central nervous system (Brain + Spinal cord) relay neurones
↓
Motor neurones – sends electrical signals FROM CNS
↓
Effector – Muscle or gland
↓
Response – Muscle contracts or gland releases a hormone
Synapses – gap between 2 neurones where chemical
messengers diffuse
what are Reflex actions
Reflex actions are automatic and rapid; they do not involve the
conscious part of the brain. Only use the spinal cord NOT THE BRAIN
why are Reflex actions important
Reflex actions are important as
they protect the body from injury.
what do coordination centers do
they receive and process information from receptors.
how does the brain work as a coordination center
Coordinates information from the
receptor cells and sends signals to
the muscles and glands.
how does the spine work as a coordination center
Coordinates messages from the
brain and receptor cells and
coordinates reflexes.
how does the pancreas work as a coordination center
Coordinates the glucose levels in the blood.
what are the three parts of the brain
- Cerebral Cortex
- Medulla
- Cerebellum
what is the function of the Cerebral cortex
Controls consciousness, intelligence, memory and language
what is the function of the Medulla
Controls unconscious activities; heartbeat and breathing
what is the function of the Cerebellum
Coordinates muscle activity
how have people been able to map regions of the brain
- studying patients with brain damage,
- electrically stimulating different parts of the brain
- using magnetic resonance imagery (an MRI)
what is the practical for reaction time
1) Person A sits on chair with arm hanging off table
2) Person B hold ruler just above person A’s hand – control variable; keep start position or ruler the same
3) Person B drops ruler without warning
4) Person A catches ruler
5) Write down distance from ruler (shorter distance = faster reaction time)
what is the eye
The eye is a sense organ containing receptors sensitive to light intensity and colour.
what does the Cornea do
Refracts (bends) light into the eye.
what does the Iris do
Contains muscles that control the amount of light entering the eye.
what does the Pupil do
Lets light into eye
what does the lens do
Refracts (bends) light onto the retina.
what does the retina do
Contains receptors for light and colour.
what do the Ciliary muscles do
Change the shape of the lens - connected to the lens by the suspensory ligaments
what do the Suspensory ligaments do.
Connect lens to the ciliary muscles.
what does the Optic nerve do
Carries impulses from the retina to the brain.
what is Accommodation
Accommodation is the process of changing the shape of the lens to focus on near or distant objects.
what happens if a object is near
Ciliary muscles - contract
Suspensory ligaments - loosen
Lens shape - thick
Light rays - refracted more strongly
what happens if an object is far
Ciliary muscles - relax
Suspensory ligaments - tighten
Lens shape - thin
Light rays - refracted less strongly
what is Myopia
(short sightedness)
- Can’t focus on objects that
are far away. - Light rays from distant
objects focus in front of the
retina. - Corrected with concave
lenses
what is Hyperopia
(long sightedness)
- Cant focus on objects that
are near. - Light rays focus behind the
retina. - Corrected with convex
lenses
how can poor sight be treated
Contact lenses
Laser surgery
Lens replacement
how do contact lenses work and what are the advantages and disadvantages
Contact lenses – sit on the cornea. This then refracts the light rays.
Advantages – lightweight
Disadvantages – Can cause irritation and infections.
how does laser surgery work and what are the advantages and disadvantages
Laser surgery – lasers change the shape of the cornea so light rays will refract
Advantages – permanent solution
Disadvantages – Can cause infections.
how does Lens replacement work and what are the advantages and disadvantages
Lens replacement – artificial lens implanted
Advantages – permanent solution
Disadvantages – Can cause infections
what is the temprature of the human body
37 degrees Celsius
how is body temprature controlled
Body temperature is controlled by
thermoregulatory centre
(hypothalamus) in the brain.
how does your body react to low temperatures
- Blood vessels supplying the skin
constrict (vasoconstriction) - Less blood flows to skin
- So less energy is lost to the
surroundings - Skeletal muscles contract (shiver).
- Due to respiration
how does your body react to high temperatures
Blood vessels supplying the
skin dilate (vasodilation)
More blood flows to skin
So more energy is lost to the
surroundings
Sweat is produced from the
sweat glands
Sweat evaporates carrying
heat away from the skin
what is the endocrine system
The endocrine system is composed of glands which secrete chemicals
called hormones directly into the bloodstream.
what are hormones
Hormones are chemical messengers released by endocrine glands into
the blood and act on target organs
what glands release adrenalin.
Adrenal
what does adrenalin do
Adrenalin prepares the body for rapid activity by increasing the heart rate and blood glucose.
where is thyroxine released
Thyroid
what does thyroxine do
Thyroxine regulates the basal metabolic rate
Reflex (nerves) vs Hormones
reflex action quicker
effect of reflex action over shorter period of time
hormone involves blood system and reflex involves neurones / nerve cells
reflex involves electrical impulses and hormone involves chemicals
reflex action affects only one part of the body
what If blood glucose
concentration TOO HIGH
The PANCREAS detects this and releases INSULIN
LIVER and MUSCLE cells take in
glucose and convert it into GLYCOGEN
what If blood glucose concentration
TOO LOW
The PANCREAS detects this and
releases GLUCAGON
LIVER and MUSCLE cells convert
GLYCOGEN into GLUCOSE
what does Diabetes cause
Diabetes causes a person’s blood sugar level to become too high.
describe type 1 diabetes
- pancreas doesn’t
produce enough insulin. - causes uncontrolled
high blood glucose levels. - Treated with insulin
injections or pancreas transplant
describe Type 2 diabetes
- Body cells no longer respond to insulin
- Obesity is a risk factor for
Type 2 diabetes. - Treated by reducing carbohydrate in the diet and by exercise.
describe Hypertonic solutions
higher concentration of water inside cell than outside cell so water leaves the cell via osmosis causing them to shrink
describe Hypotonic solutions
lower concentration of water inside cell than outside cell so water enters the cell via osmosis causing them to burst
describe Protein digestion
Excess proteins are digested into
amino acids that are absorbed into
the blood.
The excess amino acids are then
deaminated in the liver to form
ammonia.
Ammonia is a very toxic substance
and so it is immediately converted
to urea for safe excretion from the
body in the urine.
explain the Kidney function
- Filtration of glucose, urea, ions (salts) and
water from the blood. - Selective reabsorption of ALL glucose, some ions (salts) and some water into the blood.
- Excretion of ALL urea, excess ions (salts) and excess water into the urine.
what happens when there is Increased water content of the blood (more dilute)
The PITUITARY GLAND STOPS releasing ADH into the blood
Kidney tubules LESS permeable and
reabsorb LESS water MORE urine is produced
what happens when there is Decreased water content of the blood (more
concentrated)
The PITUITARY GLAND RELEASES ADH into the blood
Kidney tubules MORE permeable
and reabsorb MORE water LESS
urine is produced
describe what happens in a In a dialysis machine
- Blood high in urea flows between partially permeable membranes in the opposite direction to the dialysis fluid (maintains the concentration gradient)
- The dialysis fluid contains the same concentration of useful substances as the blood - this ensures that glucose and ions(salts) are not lost.
- Urea passes out from the blood into the dialysis fluid.
what is a KIDNEY TRANSPLANT
A diseased kidney is replaced by a healthy donor kidney. This can be from a live donor or from someone who has died.
how can risk of organ rejection be reduced during a kidney transplant
- Immune-suppressant drugs are
given - A donor kidney with a similar
‘tissue type’ issued
advantages of kidney transplants
- Transplant is
permanent - Kidney works all the
time - Concentrations in blood
kept constant
advantages of dialysis
- Works for everyone
- No need to take drugs
disadvantages of kidney transplant
May be rejected
Need to use immuno-
suppressant drugs
Transplant may need to be replaced
shortage of donors
high initial cost
High risk on infection
during surgery
disadvantages of dialysis
- Dialysis is a repetitive
treatment and short term - Substances build up in blood
between dialysis sessions - Damage to body by build-up
of substances - Risk of blood clots with
dialysis - Expensive
- Have to sit for up to 8 hrs
what does Testosterone do
controls the development of
male secondary sexual characteristics
what does Oestrogen do
controls the development of
female secondary sexual characteristics
where is FSH produced and what does it cause
produced in Pituitary Gland
- Stimulates eggs to mature
- Stimulates oestrogen production (in
ovaries)
where is oestrogen produced and what does it cause
produced in ovaries
- Lining of the womb to develop.
- Stimulates pituitary gland to make LH
- Inhibits FSH production
where is LH produced and what does it cause
produced in Pituitary Gland
- Stimulates egg release
- Stimulates progesterone
production in the ovaries - Inhibits oestrogen
where is progesterone produced and what does it cause
produced in Ovaries
- Maintains the lining of the womb
- Inhibits LH
how does the pill work
contain oestrogen to inhibit FSH so no eggs mature
contains progesterone to inhibit LH so an egg can’t be released.
advantages and disadvantages of the pill
Advantage: Easy to use, convenient
Disadvantage: Remember to take every day, Doesn’t protect against
STDs
what is Injection, implant
work the same as the pill but act over a longer time
what are the advantages and disadvantages of Injection, implant
Advantage: Don’t need to remember to take it every day.
Disadvantage: Doesn’t protect against STDs
what is a woman given if they are struggling to get pregnant
be given a ‘fertility
drug contains FSH and LH’
- FSH stimulates the maturation of
the eggs - LH stimulates the release of the
egg
how does In Vitro Fertilisation (IVF) work
- IVF involves giving a mother FSH and LH to stimulate the
maturation and release of several eggs. - The eggs are collected from the mother and fertilised by sperm
from the father in the laboratory. - The fertilised eggs develop into embryos.
- Embryos are genetically screened to see the most viable
- At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).
advantages and disadvantages of IVF
Advantages:
Able to have a baby
Disadvantages:
Emotionally and physically stressful
Expensive
Doesn’t always work
Increases risk of complications
Can lead to multiple births
what is Tropism
Plant growth response to a stimulus
what is Phototropism
Plant growth response to light
what is Gravitropism/Geotropism
Plant growth response to gravity
what is Positive Tropism
Towards the stimulus
what is Negative Tropism
Away from the stimulus
describe how phototropism happens
Auxin produced in the tip of the shoot
Auxin moves to shaded side of the stem
Auxin causes cell elongation of the shaded side (unequal growth)
Which causes the stem to grow towards the light (positive phototropism)
how are auxins used
- as weed killers
- as rooting powders
how is ethene used
Ethene is used to control ripening of fruit
during storage and transport.
how can gibberellins be used
- end seed dormancy
- increase fruit size.
what is the practical for plant responses
1) Have several seedlings
2) Measure heights of shoots
3) Some seedlings in total darkness
4) Some seedlings in darkness with light from one side
5) After 2 weeks record appearance of seedlings based on light direction
6) Re-measure heights of shoots – use string and measure length of string
Control variables
same temperature / water / soil type / number of seedlings in each investigation
