Cells And Control Flashcards
Chromosomes
Are coiled up lengths of dna molecules
Diploid
Two sets of chromosomes in a cell - 23pairs and 46
Haploid
Half the number of chromosomes- 23
Why is mitosis important?
We need to repair our cells
Help us grow
Asexual reproduction
What is interphase?
The cell increases the amount of sub cellular structures
It then duplicates its dna
What is prophase?
Spindle fibres start to form in the cell and the nuclear membrane starts to break down
What is metaphase?
The chromosomes line up in the centre of the cell
What is anaphase?
The spindle fibre pull the chromosomes apart.
What is telophase?
The nuclei start to reform
What is cytokinesis?
The cytoplasm and the cell membrane divide the two separate cells
What is the formula to calculate multiple divisions of mitosis?
Number of cells = 2n
N = number of divisions
N = to the power of
Cell differentiation
The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organismsto work more efficiently.
Cell division
Mitosis
- for growth in plants
Cell elongation
Where a plant cell expands, making the cell bigger and so making the plant grow.
What are stem cells?
Are cells that can turn into different types of cell - they are undifferentiated
What are embryonic stem cells?
They are found in a human embryo.
They can become almost any cell type in the body - they are pluripotent
What are the benefits of embryonic stem cells?
They can become any cell type in the body
Easy to remove
We can treat lots of diseases with them
Drawbacks of embryonic stem cells
Religious issues - people believe that life starts at fertilisation therefore it’s murder
Money spent on this research can be spent somewhere else
Risks of using embryonic stem cells
Can be rejected by the patient
What are adult stem cells?
They are found in adults but they’re only found in certain places like bone marrow or in a certain places in the body with differentiated tissues.
They can only become a limited range of cell types
They are multi potent
Benefits of adult stem cells
Can still treat certain disease
No ethical issues
Drawbacks of adult stem cells
Limited amount of cells that they can become
Difficult to find and collect from adult tissues
Risks of adult stem cells
Can be rejected by the patient
Where are meristems found in plants?
Meristem tissue is found in the areas of a plant that are growing eg the tips of the roots and shoots
What do meristems produce?
Unspecialised cells that are able to divide and form any cell type in the plant
They can divide and differentiate to generate into any type of cell as long as the plant lives
Example of how doctors use stem cells in medicine
They use them to cure sickle cell anaemia which can sometimes be cured with a bone marrow transplant
What are receptors?
Groups of cells that detect a change in the environment
What is a stimuli?
A change in the environment
What does the cns control?
The body’s response to a stimulus
What does the pns do?
Connects the sense organs to the cns using nerves
Describe a motor neurone
Many short dendrites carry impulses from the cns to the cell body
One long axon carries nerve impulses from the cell body to effector cells
How can you tell if it is a motor neurone?
Nervous impulse is going towards the effector to bring about a response
Describe a sensory neurone
One large dendron carries nerve impulses from receptor cells to the cell body which is located in the middle of the neurone
One short axon carries nerve impulses from the cell body to the cns
How can you tell that it is a sensory neurone?
Nervous impulse is going away from the sensory organ towards the cns
Dendrites
Carry nerve impulses towards the cell body
Axon
Carry nerve impulses away from the cell body
What are the main functions of the myelin sheath?
It speeds you the nerve impulses as it travels along the dendron
It insulated the electrical message
role of the neurotransmitters
The electrical message travelling along the axon, reaches the end of the neurone
Neurotransmitters are released from the end of the neurone
This chemical message travels across the synapse
This passes on the electrical message to the next neurone
Reflex reactions
They are fast automatic responses that bypass the brain - they help protect us from injury
What are synapses?
The connection between two neurones
How do synapses connect neurones?
The nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
The neurotransmitters then set off a new electrical signal in the next neurone
The transmission of a nervous impulse is fast but is slowed down by the synapse because the diffusion of neurotransmitters across the gap takes time
Describe the pathway of a nerve impulse through a reflex arc
The eye detects a stimulus
The sensory neurone sends a message to the spinal cord
The nerve impulses from the sensory neurone cross the synapse and trigger the relay neurone
The impulses are detected by the synapse which then cross the motor neurone
It then travels to the effector which causes a response
Normal cns
Slower response
Includes brain
Reflex arc
Faster responses
Does not go to the brain
Relay neurone
Both reflex and normal neurones
Sensory neurone Motor neurone Stimulus response Synapse Receptor cells Effector
