Chapter 2 - Cells and Control Flashcards
1
Q
Chromosomes
A
- Within the nucleus of cells
- Contains genetic material
- Coiled up lengths of DNA molecules
- Have two copies of each chromosome making them diploids. One comes from the mother, the other comes from the father
- It is reproduced through mitosis
2
Q
Cell Cycle
A
- Body cells divide and replicate during a process called the cell cycle
- Multicelluar organisms use mitosis to grow or reproduce cells that have been damaged
- Mitosis can be used as asexual organism in which only one organism is used to reproduce
3
Q
Stages of mitosis
A
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokenesis
4
Q
Interphase of mitosis
A
- The cell begins to expand and increase in subcelluar structures such as ribosomes
- The DNA duplicates so there is one copy for each cell
- The DNA forms an X shape
5
Q
Prophase of mitosis
A
- The chromosomes condense
- The membrane around the nucleus break down and the chromosomes lie free in the cytoplasm
6
Q
Metaphase of mitosis
A
- The chromosomes line up at the centre of the cell
7
Q
Anaphase of mitosis
A
- Cell fibres pull the chromosome apart
- The ends of each chromosome go to opposite ends of the cell
8
Q
Telophase of mitosis
A
- Membranes form around each sets of chromosomes
- These form nuclei and begin to divide
9
Q
Cytokensis of mitosis
A
- The cell membrane and cytoplasm divide
10
Q
Results of mitosis
A
- Two daughter cells are produced with exactly the same set of DNA
- They are genetically identical diploids
11
Q
Growth
A
The increase in size or mass
12
Q
Cell Differentiation
A
- The process in which a cell changes to become specialised for its role
- Allows multicellular organisms to work more efficently
13
Q
Cell Division
A
Mitosis
14
Q
Cell Elongation
A
This is where a plant cell expands making it grow and bigger
15
Q
Growth in animals
A
- Occurs by mitosis
- Happens whilst young
- Reach full growth
- Cell division in adults is for repair
- Cell differentiation is lost at an early age
16
Q
Growth in plants
A
- Growth in height is due to cell elongation
- Cell division only occurs in meristems
- Plants continuously grow with them developing new branches
- Plants continue to differentiate
17
Q
Cancer
A
- Caused by uncontrollable cell division
- The rate at which mitosis occurs is controlled by genes
- If there is a change in one of the genes that control mitosis, then there will be an uncontrollable division
- This creates a mass of abnormal cells called a tumour
- This destroys tissue
18
Q
Percentile charts
A
- Used to monitor growth
- Assess the development of a child so that a pattern can be shown that outlines any issues such as obesity and dwarfism
- A baby is regularly monitored to see if it is growing normally
- Measurements are taken from the height, weight and head circumference
- This is represented in percentiles. The 50th percentile means 50% of babies have reached that measurement at a certain age
19
Q
Stem Cells
A
- Differntaite to become different types of specialised cells
- Stem cells are originally undifferentiated
- Depending on their role, they divide to become new cells and then differentiate
- These can be found in human embryos. They have the potential to divide into any cell
- These cells are important for growth and development
- Adults also have stem cells but they are only found in select places such as bone marrow
- These are not as versatile and can not produce all types of cell
- In adults, they are used to replace damaged cells
20
Q
Meristems
A
- These are the only parts in the plant that divide through mitosis
- Meristem tissue is found in the areas of the plant that are growing such as as roots and leaves
- The meristems produce unspecialised cells and form any cell type in the plant. Unlike humans, they can differentiate to any cell through out the plants life
- These cells can form xylem and phloem
21
Q
Stem cell uses
A
- Doctors already use some adult stem cells to treat diseases such as blood diseases like sickle cell anaemia with a bone marrow transplant
- Scientests have experimented with embryonic stem cells and growing them. Under certain conditions they can specialise
22
Q
Uses of embryonic stem cells
A
- Replace cells damaged by injury or disease
- An example is that new cardiac muscles can be implanted into someone with heart disease
- This leads to the potential of new curwa
- However further research and development is needed
23
Q
First stage of embryonic stem cell development: Tumour Development
A
- Stem cells divide quickly
- If scientests can not control the division of stem cells within a patient then a tumour may develop
- This needs to be 100% eradicated before stem cells are used as common medicine
24
Q
Second stage of embryonic stem cell development: Disease transmission
A
- Viruses can be located in cells
- If the stem cells used contain a virus, it can pass it on to the patient
- This can further decline their health
- A method needs to be developed to always detect a virus before the commercial development of stem cells
25
Third stage of embryonic stem cell development: Rejection
- If the transplanted cells are not grown within the body, the body may trigger an immune response in which the body tries to remove the foreign cells
- Drugs can supress this, but the immune system becomes weaker
- This issue needs to be overcome
26
Ethical issues with stem cells
- People may disagree the use of stem cells because they believe that the medical researchers may be playing God
- Also the embryonic stem cells used may have the potential for human life which may anger some people
27
The CNS
- Central Nervous System made up of the brain and spinal cord
- The spinal cord is a long column of neurones that runs from the base of the brain down through the spine
- It branches off at some point to connect with other parts of the body
- This relays information
- The brain is connected by billions of interconnected neurones
28
Cerebrum
- Largest part of the brain
- Divided into two parts called cerbral hemispheres
- The left hemisphere controls the muscles on the right side of the body and vice versa
- The cerebrum is important for movement, intelligence, memory anf vision
29
Cerebellum
Responsible for muscle coordination and balance
30
Medulla Oblongata
Controls unconscious activitis such as breathing and heart rate
31
CT scanning
- Uses x-rays to produce an image of the brain
- Shows main structures of the brain but not their functions
- If a CT scan shows disease or damage in the brain structure and if the patient has lost wome function, the function of that part of the brain can be worked out
32
PET scanning
- Use radioactive chemicals to show which parts of the brain are active when the person is inside a scanner
- Investigate both the stucture and the functions of the brain in real time
- Useful for studying disorders such as Alzheimers as it shiws areas of the brain that sre usually active or inactive
33
Issues with treating the CNS
- There are many things that can go wrong with the CNS such as tumors or injuries
- Its hard to repair damage as the neurones in the CNS do not readily repair and scientest have not developed a way to repair nervous tissue
- It is not easy to access the CNS. e.g it is hard to remove tumors in the CNS
- If the treatment goes wrong, then it could lead to permanent damage
34
The Nervous System
- The CNS coordinates responses to stimulants
- This is done through neurones through all parts of the body
- The body has many sensory receptors that dectect a stimulus
- Different stimuli are detected by different receptors e.g light is detected by the eyes
- When a stimulus is deteced, then it is converted into nervous impulses whcih are sent along to the CNS
35
CNS respones
- Coordiantes a response in relation to a stimulus
- Impulses travel through the CNS along relay neurones
- The CNS sends impulses to an effector (a muscle or a gland) along a motor neurone. The effector then responds accordingly such as by contracting or relaxing
- The time it takes for this to occur is called the reaction time
36
Neurones
- All neurones have a cell body
- This cell body has extensions to other neurones
- Dendrites and Dendrons carry nerve impulses to the cell body and
- Axons carry nerve impulses away from the cell body
- Some axons are surrounded by a myelin sheath which acts as an electrical insulator and speeds up impulses
37
Myelin Sheath
- Joins between nerves slow down the speed of the impulses, the myelin sheath reduces this delay
38
Sensory Neurone
- One long dendron carries impulses from receptors tothe cell body which is located in the centre of the neurone
- One short axon carries the impulse to the CNS
39
Motor Neurone
- Many short dendrites, surrounded by the myelin sheaths that carry impulses from the CNS to the cell body
- One long axon carries the impulse from the cell body to the effector cells
40
Relay Neurone
- Many short dendrites carry nerve impulses from sensory neurones to the cell body
- An axon carries nerve impulses from the cell body to motor neurones
41
Synapses
- Connect neurones
- Nerve signals are transferred by chemicals calld neurotransmitters which diffuse
- These transfer electrical signals
- Ths transmission of s nervosu impulse is very fast but it is slowed down a bit at the synapse because of the diffusion of neurotransmitters across the gap
42
Reflexes
- Prevent injury due to quick action
- Automatic and rapid
- The passage from recpetor to effector is called the reflex arc
- These go through the spinal cord and the medulla
- When a stimuli is detected impulses are sent along the CNS
43
Process of a reflex
1. Stimulant occurs
2. Stimulation of pain receptor
3. Impulses moves along sensory neurone
4. Impulses are passed along a relay neurone through a synapse
5. Impulses travel along a motor neurone
6. The muscles contracts or relaxes
This does not involve thinking time so it is quicker than normal action
44
Relfexes in the eye
- Very bright light can damage the eye so a relfex protects it
- Light receptors detect light and send an impulse through a sensory neurone to the brain
- The message moves along a relay neurone to a motor neurone which causes muscles in the iris to relax or contract
45
Parts of the eye
- Cornea
- Iris
- Lens
- Retina
- Rods
- Cones
- Optic Nerve
46
Role of the cornea
Refracts light into the eye
47
Role of the iris
Controls how much light enters the pupil
48
Lens
Refracts light, focuses on the retina
49
Retina
The light sensitive part with receptor cells called rods and cones
50
Rods
Dims light but do not detect colour
51
Cones
Detect colour but not good in dim light
52
Optic Nerve
Carries impulses from the recptors to the brain
53
Looking at distant objects
- The ciliary muscle relaxes which allows suspensory ligaments to pull tight
- This pulls the lens into a less rounded shape so light is refracted less
54
Looking at close objects
- Ciliary muscle contracts which causes slackens suspensory ligaments
- Lens becomes more rounded which refracts the light more
55
Longsightedness
- People are unable to focus on near objects
- The lens does not bend light enough or the eyeball is too short
- Light from near objects is brought into focus behind the retina
- Glasses with convex lenses can fix this
56
Shortsightedness
- People who are unable to focus on distant objects
- The lens bends the light too much or the eyeball is too long
- Light from distant objects is brought into focus from the retina
- Glasses with concave lenses can fix this
57
Colourblindness
- The most common form of colourblindness is red-green
- Caused by the red-green cones in the retina do not work properly
- There is no cure as cone cells can not be replaced
58
Cataracts
- Cloudy patch on the eyes
- Stops light from being able to enter the eye causing blurred vision
- Colours may not be seen as vividly
- Treated by replacing the lens with an artificial one
- Caused by a faulty lens
