cells and control Flashcards
mitosis
a type of asexual cell division which results in the production of two genetically identical daughter cells
what are the 3 parts of the cell cycle
interphase
mitosis
cytokinesis
interphase
when not dividing, the DNA is spread out in long strings
before division the cell has to grow and make more subcellular structures
DNA is then duplicated to form X-shaped chromosomes
what are the 4 stages of mitosis
PMAT prophase metaphase anaphase telophase
prophase
chromosomes condense
nuclear membrane starts to break down
metaphase
chromosomes line up in the centre of the cell
anaphase
spindle fibres pull chromosomes apart
two arms of each chromosome go to opposite ends of the cell
telophase
new nuclear membranes form around each set of chromosomes to become the two separate nuclei
cytokinesis
the cytoplasm and cell membrane divide to form two separate cells
number of cells after x number of divisions formula
number of cells = 2^x (where x is the number of divisions)
growth
an increase in size or mas
animals and plants grow and develop due to what 3
cell differentiation
cell division
cell elongation (in plants only)
what is cell division and growth like in animals (5)
- all growth happens by cell division
- tend to reach full size when young and then stay that size
- cells divide quickly when young
- as an adult, division is mainly for REPAIR
- cell differentiation is lost at a very young age
what is cell division and growth like in plants (3)
- growth in height is mainly due to cell elongation
- cell division occurs mainly in the tips of the roots and shoots (meristem areas)
- plants continue to grow and differentiate throughout their whole lives
cancer
case of uncontrollable cell division
what can cause cancer
is there is a change in one of the genes that controls cell division then a cell may begin to divide uncontrollably
this results in an abnormal mass of cells known as a tumour - if the tumour invades and destroys surrounding tissue it is a cancer
what is the use of percentile charts
growth charts can be used to assess a child’s growth to identify an overall pattern and see any potential problems
when would doctors be likely to investigate further based on a percentile chart
if the baby is above the top or below the bottom percentile line
if they change two or more percentile lines
if there is an inconsistent pattern
stem cells
undifferentiated cells
where are human stem cells found
PLURIPOTENT stem cells are found in early human embryos
adults have stem cells found in certain places such as the bone marrow that are MULTIPOTET are used to replace damaged cells
where are plant stem cells found
MERISTEMS produce unspecialised cells that act like embryonic stem cells, they remain PLURIPOTENT
how can stem cells be used in medicine
- treat diseases (eg sickle cell anaemia can be cured with a bone marrow transplant)
- embryonic stem cells can be stimulated to differentiate into specialised cells
- these cells can be used to replace those damaged by disease or injury
risks of using stem cells in medicine (4)
rejection (if grown from someone else, may be recognised as foreign and trigger an immune response - taking suppressant drugs makes them more susceptible to disease) tumour development (if scientists can't control the rate of division of transplanted cells) disease transmission - if donor cells are infected the virus could be passed on research into using embryonic stem cells raises ethical issues because of potential human life
what is the path from stimulus to response
stimulus -> receptor -> sensory neurone ->CNS ->motor neurone ->effector ->response
how is information in the nervous system sent
as an electrical impulse via neurons
neuron structure
cell body with nucleus
dendrons and dendrites
axons
myelin sheath
dendrons and dendrites
carry the impulses to the cell body
axons
carry impulses away from the cell body
myelin sheath
insulates some axons and acts as an electrical insulator, speeding up the impulse
are dendrites and axons long or short in each type of neuron
sensory long dendron short axon
motor short dendron short axon
relay short dendron long axon
synapse
the connection between 2 neurons
describe what happens at a synapse
neurotransmitters carrying the signal diffuse across the synaptic left to trigger an electrical impulse in the next neuron
reflex
automatic, rapid responses to stimuli
reflex arc
the passage of information in reflex form from receptor to effector
what are the 6 stages of a reflex
1) a stimulus is detected by receptors
2) impulse is sent along sensory neuron to a relay neuron in the CNS
3) synapses carry impulse across to the next neuron
4) impulses are passed from relay neuron to motor neuron
5) impulse travels from the motor neuron to the effector such as a muscle
6) a muscle contracts and you move away from the source of danger
example of reflexes in the eyes
light receptors in the eye detect very bright light and sends a message along the reflex ac that tells circular muscles in the iris to contract making the pupil smaller, allowing less light in so that very bright light doesn’t damage the eyes
5 parts of the eye
cornea lens iris retina optic nerve
cornea
refracts light into the eye
lens
refracts light, focusing it onto the retina
iris
controls how much light enters the eye
retina
light sensitive part covered in receptor cells (rod and cone)
rod cells
more sensitive in dim light
can’t sense colour
cone cells
less sensitive in dim light
sensitive to colour
optic nerve
carries electrical impulses from the receptors to the brain
colour blindness(definition, most common version, cure?)
can’t tell the difference between certain colours
most common form is red-green colour blindness caused by red and green cone cells not working properly
currently no cure as cone cells can’t be replaced
cataract (what is it, effects, cure?)
cloudy patch on the lens, stopping light from being able to enter the eye properly
blurred vision, less vivid colours, difficulty looking at bright light
can be treated by replacing the faulty lens with an artificial one
how does the eye focus
the lens is elastic, so the eye can focus light onto the retina by changing the shape of the retina
how does the eye focus when looking at close objects
ciliary muscle contracts
suspensory ligaments slacken
lens becomes more rounded
light is refracted more
how does the eye focus when looking at faraway objects
ciliary muscle relaxes
suspensory ligaments pull tight
lens becomes less rounded
light is refracted less
long sightedness
can’t focus on nearby objects
light is focused behind the retina
what causes long sightedness
- wrong shape lens doesn’t bend light enough
- eyeball is too short
how to fix long sightedness
convex lens ()
short sightedness
can’t focus on faraway objects
light is focused in front of the retina
what causes short sightedness
- wrong shape lens bends light too much
- eyeball is too long
how to fix short sightedness
concave lens )(
spinal cord
a long column of neurons that runs from the base of the brain down the spine
at several places, neurons branch off and connect with other parts of the body
relays information between brain and the rest of the body
cerebelllum
responsible for motor coordination
medulla oblongata
controls unconscious activities such as breathing and heart rate
cerebrum
largest part of the brain
two halves called cerebral hemispheres which control the opposite side of the body
different parts of the cerebrum are responsible for different tasks; memory, intelligence, vision, language etc.
CT scanning
uses x-rays to produce an image of the brain
shows map but no function
if a structure is damaged or there is loss of function that can be identified
PET scanning
use of radioactive chemicals to show which parts of the brain are most active
very detailed
shows structure and function
shows if some areas of the brain are usually inactive or active (useful for studying disorders affecting brain’s activity)
why are there issues with treating problems in the CNS (3)
- no way to repair neurons or nervous tissue
- if a problem develops it is inaccessible
- treatment for problems in the CNS can lead to permanent damage
