Unit 2 - Cells And Control Flashcards by edward waller

Mitosis occurs in

Body cells only

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Examples of when mitosis is needed

Growth

Repair

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Mitosis is a type of

Cell division

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5 stages of mitosis

IMPAT
Interphase
Prophase
Metaphase
Anaphase
Telophase

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What happens during interphase

DNA copies (chromosome is visible)

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What happens in prophase

Each chromosome consists of two chromatids

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What happens during metaphase

Nuclear membrane breaks down

Chromosomes line up along middle of cell

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What happens during anaphase

Chromatids become chromosomes as they separate and one from each pair is pulled to each pole of the cell

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What happens during telophase

Spindle fibres disappear and new nuclear membrane forms around each group of chromosomes

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What is it called when the cell splits into 2

Cytokinesis

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Why does cancer occur

Uncontrolled mitosis causes tumour

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How does cell division occur in animals

Mitosis causes identical cells
These differentiate
Then can become specialised eg nerve cells

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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

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What is a percentile chart

Show typical trend of growth of an organism

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When is a percentile chart used

To monitor growth eg of baby

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3 types of stem cell

Embryonic
Adult
Meristems

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Embryonic cells is

From an embryo
Early stage (8cells)

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What can embryonic cell be used for

Replace/repair brain cell
Retina cell
Drug testing

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Positive of using embryonic cell

Easy to get
Can produce (specialise) into any other cell
Replace faulty cell with good one

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Negatives of using embryonic cells

Ethical (alive)

May not stop dividing so cause cancer

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What is an adult stem cell

From differentiated tissue, such as skin or bone

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What are adult stem cells used for?

Leukaemia treatment

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Positives of using adult stem cells

No ethical issue
No rejection to body
Replace faulty cell with good one

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Negatives of using adult stem cells

Produce few types of cell

May not stop dividing so cause cancer

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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