Unit 2 - Cells And Control Flashcards
Mitosis occurs in
Body cells only
Examples of when mitosis is needed
Growth
Repair
Mitosis is a type of
Cell division
5 stages of mitosis
IMPAT Interphase Prophase Metaphase Anaphase Telophase
What happens during interphase
DNA copies (chromosome is visible)
What happens in prophase
Each chromosome consists of two chromatids
What happens during metaphase
Nuclear membrane breaks down
Chromosomes line up along middle of cell
What happens during anaphase
Chromatids become chromosomes as they separate and one from each pair is pulled to each pole of the cell
What happens during telophase
Spindle fibres disappear and new nuclear membrane forms around each group of chromosomes
What is it called when the cell splits into 2
Cytokinesis
Why does cancer occur
Uncontrolled mitosis causes tumour
How does cell division occur in animals
Mitosis causes identical cells
These differentiate
Then can become specialised eg nerve cells
How does cell division occur in plants
Mitosis causes new cells
Cells have vacuoles to take in water by osmosis and can elongate
These can then differentiate into specialised cells
They grow and differentiate throughout life
What is a percentile chart
Show typical trend of growth of an organism
When is a percentile chart used
To monitor growth eg of baby
3 types of stem cell
Embryonic
Adult
Meristems
Embryonic cells is
From an embryo Early stage (8cells)
What can embryonic cell be used for
Replace/repair brain cell
Retina cell
Drug testing
Positive of using embryonic cell
Easy to get
Can produce (specialise) into any other cell
Replace faulty cell with good one
Negatives of using embryonic cells
Ethical (alive)
May not stop dividing so cause cancer
What is an adult stem cell
From differentiated tissue, such as skin or bone
What are adult stem cells used for?
Leukaemia treatment
Positives of using adult stem cells
No ethical issue
No rejection to body
Replace faulty cell with good one
Negatives of using adult stem cells
Produce few types of cell
May not stop dividing so cause cancer
What are meristem stem cells
Found in plant cells (roots tips and shoots)
What can meristem stem cells be used for
To produce any kind of plant cell
What is the cerebellum
Part of the brain that coordinates and controls precise smooth movement
What is the cerebral hemisphere
Part of the brain the controls voluntary movement and is responsible for learning and memory
What is the medulla oblongata
Part of the brain that regulates heart beat and breathing rate
2 methods of accessing brain tissue under the skull
CT (computerised tomography) scan
PET (positron emission tomography) scan
Why is it difficult to repair brain
Radiotherapy could damage healthy tissue
Skull protects the brain
Why is it difficult to get the the spinal cord
Spine protects it
What are sensory receptors
Dendrites of a sensory neurone
What does a sensory neurone do
Carries impulses to CNS
What do motor neurones do
Carry impulses from CNS to effector organs
Where are relay neurones
Only in the CNS
What is a synapse
Where 2 neurones meet
How does impulse cross the synapse
Causes chemical neurotransmitter to be released
This diffuses across the synapse and fits into receptors, causing new electrical impulse to be released in next neurone
What does an axon do
Carries impulses away from the cell body
What does a dendrite do
Receives impulses from receptor cells and other neurones
What is myelin sheath
Fatty layer of insulation around a neurone
What is a reflex arc
Involves only 3 neurones, with impulses passing to and from spinal cord
Why is a reflex arc needed
For fast responses eg blinking
What is a reflex arc a faster response
Brain doesn’t have to process it so less synapses have to be crossed
What is an eye
Sensory receptor that detects the stimulus of light
What does a cornea do
Refracts the light in to the eye
What is the iris
Muscle that controls how much light comes in
What is the iris muscle controlling
The diameter of the pupil
What does a lens do
Refracts light to focus on the retina
What is the retina
A layer of tissue at the back of the eye containing receptor cells for light and colour
Nerves convert image into electrical impulses, what sends the signal to the brain?
Optic nerve
What are ciliary muscles
They change the shape of the lens, depending on distance of object
What are suspensory ligaments
Connect lens to ciliary muscles
What does the optic nerve do
Carry impulse from retina to brain
What happens to ciliary muscles, suspensory ligaments and the shape of the lens when an object is near
Ciliary muscles - contracted
Suspensory ligaments - slack
Shape of lens - fat and rounded
What happens to ciliary muscles, suspensory ligaments and the shape of the lens when an object is far
Ciliary muscles- relaxed
Suspensory ligaments - tight
Shape of lens - thin and flattened
What is myopia
Short sightedness
How can myopia be treated
Concave lens
What is hyperopia
Long sightedness
How can hyperopia be corrected
Convex lens
3 types of vision correction
Contact lenses
Laser surgery
Lens replacement
What is cataracts
When the lens becomes cloudy
How can cataracts be treated
Replacing lens with clear, artificial lens
Why does colour blindness occur
When one type of cone is missing or not functioning properly
What do cones do
Determine colour of the image depending on how much they are stimulated
