Topic 2 - cells and control Flashcards
What is the cell cycle?
A series of event that take place in a cell involving cell growth, DNA replication and cell division
It is described as the life cycle of a cell
What is interphase?
The cell grows. New organelles are synth sized and the DNA is replicated
What are the stages of mitosis?
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
What is a chromosome?
A linear DNA molecule tightly coiled around proteins
What happens to chromosomes during DNA replication?
The DNA in the ‘arm’ of each chromosome is replicated
What is mitosis?
a form of cell division that produces two diploid ‘daughter’ cells, both genetically identical to the parent cell
Why is mitosis important in organisms?
Asexual reproduction
Growth
Repair of damaged cells
Cell replacement
Outline prophase
DNA condenses, chromosomes become visible
Nuclear membrane disappears
Outline metaphase
Chromosomes line up along the cell equator
Outline anaphase
Spindle fibres attach to each chromosome
‘Arms’ of each chromosome pulled to opposite poles
Chromatids separated
Outline telophase
Nucleus of the cell divides
New membrane forms around each set of chromosomes
What does cytokinesis involve?
Division of the cell membrane and cytoplasm
Two genetically identical ‘daughter’ cells produced
What is cancer?
Non-communicable disease
Uncontrolled cell division which results in the formation of a primary tumour
Tumour cells break off and spread to other tissues forming secondary tumours
What are percentile charts?
A chart used to monitor growth
Measurements can be compared to the expected values at a certain age
What does the 95th percentile mean?
95% of measurements will be below the value of the 95th percentile
What can doctors determine from percentile charts?
Slower growth than normal
Faster growth than normal
Abnormal growth
Describe growth in animals
Cell division occurs in body Cells. It occurs at a slower rate in adults that in younger animals as growth stops and cell division is only required for replacement and repair
Most cells differentiate at an early stage and become specialised some adult stem cells retain their ability to differentiate
Describe growth in plants
Cell division can only occur in meristemic tissue. The rate of cell division remains the same throughout a plant’s life
Meristematic stem cells can differentiate into any cell type for as long as the plant lives
Cell elongation occurs in all cells. Cells expand and enlarge
What are stem cells?
Cells that are unspecialised and capable of differentiating into a range of different cell types
What is meant be differentiation?
The process by which stem cells become specialised
Some genes switch on or off determining cell types
Why is cell differentiation important?
It enables the formation of specialised tissues with specific functions
What are embryonic stem cells?
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
What is the function of embryonic stem cells?
Enable the growth and development of tissues in human embryos
What are adult stem cells?
Stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells
What is the primary function of adult stem cells?
Replacement of dead cells
Where are stem cells found in plants?
Meristem
Where is the meristem tissue found?
In regions of the plant where cells are continuously diving
What are meristematic stem cells?
Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant
How can stem cells be used in medicine?
Stem cells collected
Stem cells stimulated to differentiate into specific cell types
Specialised cells transplanted into the patient
Used to treat damage or disease
Where can embryonic stem cells be collected from?
Donor stem cells removed from embryos grown in vitro
Patients own stem cells removed from the umbilical blood before birth
What are the benefits of using stem cells in medicine?
Treat damage or disease
Treat diseases that would otherwise be untreatable
Used in scientific research
Growing organs for transplants
What are the risks of stem cell use in medicine?
Transplanted stem cells could cause tumours
Finding suitable stem cell donors is a difficult task
Stem cells may be rejected by the body
Potential side effects
Long term risks of using stem cells Unknown’s
Stem cells may become contaminated during preparation and when transplanted transmit infections to the patient, making them sicker
What are the ethical issues related to the use of stem cells in medicine?
The embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
May lead to the reproductive cloning of humans
What is the central nervous system?
Brain and spinal cord
What is the spinal cord?
A long, thin structure composed of neurones that extends from the medulla oblongata
What is the function of the spinal cord?
Connects the peripheral nervous system to the brain
Describe the structure of the brain
Consists of three main regions:
Cerebrum
Cerebellum
Medulla oblongata
Describe the structure of the cerebrum
Largest region of the brain
Divided into two hemispheres
What is the function of the cerebrum?
Involved in: Intelligence Language Memory Emotion Visual and sensory processes
What is the function of each cerebral hemisphere?
Left hemisphere receives sensory information form the right side of the body and controls the muscles
Right hemisphere receives sensensory information and controls the muscles
Where is the cerebellum located?
Lower region of the brain
What is the function of the cerebellum?
Involved in:
Coordination of muscles
Voluntary movement
Non-voluntary movement
What is the function of the medulla oblongata?
Controls automatic processes in the body
What methods, other than surgery, are used by doctors to observe the brain?
Ct scan
PET scan
What is a CT scan?
A procedure that uses X-rays to produce 3D cross-sectional images of the brain
Describe how CT scams are useful to investigate brain function
CT scans show damaged regions oft the brain
Observations of the patient’s symptoms can enable scientists to determine the function of the damaged region
What does a PET scan involve?
Radioactive substance unjected into a patient’s bloodstream and taken up by tissues in the brain
Radiation emitted by tissues detected, enabling the identification of active inactive regions of the brain
Describe how PET scans are useful to investigate brain function
Show which areas of the brainier active and which areas are not
Comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine the functions of inactive regions
Why is it difficult to treat damage to the CNS?
Damage to neurones is permanent and cannot be repaired
Hard to reach some areas of the brain
Risk of further permanent damage to others areas of the CNS during surgery
What is the function of the nervous system?
Allows an organism to rapidly react to environmental and internal changes
What are neurones?
Nerve cells adapted to quickly transmit nerve Impulses
They are the functional units of the nervous system
What is the function of the axon?
Carries impulses away from the cell body
Enables the transmission of the nerve impulses over long distances
What is the function of the dendrites and dendrons?
Carry impulses towards the cell body
Dendrites provide a large surface area to receive impulses
What is the role of the myelin sheath?
Electrically insulating layer
Surrounds the axon and increases the speed of impulses
Outline the function of a sensory neurone
Carries impulses from receptors to the central nervous system
Describe the structure of a sensory neurone
Long dendron carties impulses from receptior to the cell body
Cell body found part way along the neurone
Short axon carries impulses from the cell body to the CNS
Outline the function of a motor neurone
Carries impulses from the central nervous system to effectors
Describe the structure of a motor neurone
Short dendrites carry impulses from the CNS to the cell body
Cell body found at one end of the neurone
Long axon carries impulses from the cell body to the effectors
Outline the function of a relay neurone
Carries impulses from sensory neurones to motor neurones within the central nervous system
Describe the structure of the relay neurone
Short dendrites carry impulses from sensory neurones to the cell body
Short axon carries impulses from the cell body to motor neurones
Describe how the central nervous system coordinates a response to a stimulus
Sensory receptor detects stimulus
Sensory receptor sends impulses along sensory neurone to CNS
CNS sends information to effector along motor neurone effector produces a response to the stimulus
What is a synapse?
A small gap between neurones across which a nerve impulse Is transmitted via neurotransmitters
How are nerve impulses transmitted across a synapse?
Nerve impulse reaches presunaptic neurone
This triggers the release of neurotransmitters
Neurotransmitters diffuse across the synapse
They bind to receptors on the postsynaptic neurone
This stimulates an impulse in the postsynaptic neurone
Why do synapses slow doe. The transmission of nerve impulses?
It takes time for the neurotransmitters to diffuses across the synapse and bind to receptors on the postsynaptic neurone
What is a reflex?
Automatic response to a stimulus by the body
Involuntary - does not involve conscious part of the brain
Protective mechanism
Describe the reflex arc
Stimulus -> sensory receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
