Sb2 Flashcards
Stages of mitosis and description of each
Interphase - the chromosomes copy themselves and extra sub cellular structures are made
Prophase - the nucleus starts to break down and spindle fibres appear
Metaphase: the chromosomes are lined up on the spindle fibres across the middle of the cell
Anaphase : the chromosome copies are seperated and move to opposite ends of the cell on spindle fibres
Telophase : a membrane forms around each set of chromosomes to form nuclei
Cytokinesis: a cell membrane forms to separate the two cells and two daughter cells are formed
Asexual reproduction summary
- reproduction only requires one parent
- produces offspring that are clone
- asexual reproduction relies on mitosis
Growth definition
The increase in size as a result of an increase in number or size of cells
What is cell differentiation
The process that changes less specialised cells into more specialised ones
A blood cell is a specialised cell . How is it adapted
- it has no nucleus allowing more space for red haemoglobin molecules .
- it has a large surface area which allows oxygen to diffuse in and out more quickly
A fat cell is a specialised cell . How is it adapted ?
- the cytoplasm of fat cells is filled with large fat droplets . The fat is stored until the body needs energy
What are nerve cells adapted to do
To carry electrical impulses from one place to another
What allows plants to continue growing throughout their life
A group of cells near the end of each shoot called meristems . The cells in meristems divide rapidly by mitosis and contribute to length and differentiate to carry out unique functions
Specialised plant cell and it’s features
A xylem cell : carries water throughout the plant
-Thickened wall to withstand water pressure
-Tiny pores in wall allow water and mineral salts to enter and leave the vessel
-No cytoplasm so vessel is empty
-loss of cell walls of two xylem cells to form a tube
Stem cells definition
Cells that can divide repeatedly over a long period of time to produce cells that then differentiate
Where are the stem cells found in plants
In the meristem
Difference between plant and animal stem cells
Plant stem cells are usually able to produce any kind of specialised cell throughout the plants life however with animals all the cells differentiate as an embryo
What is an adult stem cell and what does it do
Stem Cells in animals that can only produce the tissue around them . The adult stem cells in human tissue allow the tissues to grow or replace old or damaged cells
What do embryonic stem cells do
Divide to produce more and more stem cells
What happens once an embryo is three weeks old
The stems cells in the brain area start to differentiate
Where is the cerebral cortex
It is at the front of the brain and is divided into two hemispheres .
What happened to Phineas gage and what did it help prove
He was walking on a railway sight when dynamite exploded launching a pole straight into the front of the cerebral cortex at the front of his brain . After a few minutes unconscious he was able to get up and walk and talk again perfectly fine . However they found his personality changed . Before the accident he was kind and hard working but after he was lazy and irritable . This helped doctors learn that the cerebral cortex controls ur personality
Where is the cerebellum and what does it do
It’s located at the base of the brain . It is divided into two halves and controls balance and posture.
It also controls the timing and fine controls of muscle activity making sure movements are smooth.
Where is the medulla oblongata and what does it do
It controls ur heart rate and breathing rate and is also responsible for reflexes such as swallowing and vomiting . It is located at the bottom of the brain and the mass of neurons that make it up connects the brain to the spinal cord
What’s the CNS
The central nervous system . It controls ur body and is made up of the brain and spinal cord .
What do impulses in your body do
Allows all the parts of ur body’s to communicate using electric signals .
What is a stimulus
Anything ur body is sensitive to including changes inside your body and in its surroundings
What do receptor cells do
Detect stimuli
What are sense organs
Eyes skin and ears that detect stimuli . They do this with receptor cells
What do receptor cells do
Create impulses which usually travel to the brain. The brain then processes the information and can send impulses to other parts of the body to cause something to happen ( a response )
What is neurotransmissions and where does it happen
The travelling, or transmission, of impulses is called neurotransmission and happens in neurones (nerve cells).
Sensory neurone function
sensory neurone. Its function is to carry impulses from receptor cells towards the CNS.
How are impulses transmitted
A receptor cell impulse passes into a tiny branch called a dendrite. It is then transmitted along the dendron and the axon. A series of axon terminals allow impulses to be transmitted to other neurones.
How are sensory neurons adapted
Dendrons and axons are frequently long, to allow fast neurotransmission over long distances. There is also a fatty layer surrounding these parts, called the myelin sheath.
This electrically insulates a neurone from neighbouring neurones (e.g. in a nerve), stopping the signal losing energy.
What does the eye contain
The eye is a sense organ that contains receptor cells found in a layer called the retina
What are cones
Cones are receptor cells that are sensitive to the colour of light. Some cones detect red light, while others detect green or blue.
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What happens to the info from the cones
The information from all the cones is processed into full colour vision at the back of the cerebral hemispheres
What are rods
Rods are receptor cells that detect differences in light intensity, not colour.
Rods vs cones
Rods work well in very dim light whereas cones only work in bright light, which is why your colour vision is poor in dim light.
What is the cornea
Clear colourless covering that focuses light
The pupil
The pupil is the dark area in the middle of the eye, and is where light enters.
The amount of light entering the eye is controlled by muscles in the iris,
which can constrict the pupil (decrease its diameter or dilate it make it bigger). Bright light can damage the receptor cells in the retina.
How are images created from light rays Entering the eye
Light rays entering the eye need to be focused onto a point in the retina to produce a clear image. Most focusing is done by the cornea, which bends (refracts) light rays to bring them together. The lens then fine-tunes the focusing. Ciliary muscles make the lens fatter to focus light from near objects and thinner to focus light from distant objects.
Causes of short sightedness and long sightedness
Short sightedness - . This is because the rays of light from distant objects are focused in front of the retina
Long sightedness - rays of light from close objects are focused behind the retina
What is a cataract and how to fix it
Cataract is a protein build up inside the lens that makes it cloudy . Full vision can be restored by replacing the clouded lens with a plastic one.
What’s the cause of color blindness
People with colour-blindness have some cones that do not work properly and so have difficulty in seeing some colours.
What do effectors do
When the brain coordinates a response to a stimulus, impulses are sent to effectors and these carry out an action. Effectors include muscles and glands
What do motor neurons do
Motor neurons carry impulses to effectors . Doesn’t have a dendron and the dendrites are on the cell body .
What is a relay neuron
Relay neurones are short neurones that are found in the spinal cord, where they link motor and sensory neurones. Doesn’t have a dendron and the dendrites are on the cell body
What is a synapse
It is the tiny gap where one neuron meets another . When an impulse reaches an axon terminal a neurotransmitter substance is released into the gap . This is detected by the next neurone which generates a new impulses. In short a synapse is the tiny gal where neurotransmitters diffused into the next neuron
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The reflex arc steps
1) stimuli is detected by receptor cells
2) this then stimulates a sensory neurone which will carry an impulse to the spinal cord
3) in the spinal cord the impulse is then transferred to a relay neuron
4) the relay neuron then pases the impulse to a motor neuron
5) this then travels back out to the body to an effector which will cause an action based on the stimuli for example if you burn ur hand the effector would be ur wrist and the action the effector would be carrying out is moving ur wrist out the way.
