Topic 2: Cells and Control Flashcards
What is the cell cycle?
A series of events that take place in a cell involving cell growth, DNA replication and cell division. It’s described as the lifecycle of a cell
What are the three stages of the cell cycle?
Interphase, mitosis and cytokines
What is interphase?
The longest stage of the cell cycle that involves cell growth, the synthesis of new organelles and DNA replication
What does DNA replication involve?
Double helix ’unzips’ exposing two strands, DNA bases align next to complementary bases on the DNA strand, complementary base pairs join and two identical DNA molecules formed
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 (chromatid) 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 production, growth, repair of damaged cells and cell replacement
What are the four stages of mitosis?
Prophase, Metaphase, Anaphase and Telophase
What happens in Prophase?
DNA condenses, chromosomes become visible and nuclear membrane disappears
What happens in Metaphase?
Chromosomes line up along the cell equator
What happens in Anaphase?
Spindle fibres attach to each chromosome, ‘arms’ of each chromosome pulled to opposite poles and chromatids separated
What happens in Telophase?
Nucleus of the cell divides and new membrane forms around each set of chromosomes
What does cytokines involve?
Division of the cell membrane and cytoplasm and two genetically identical ‘daughter’ cells produced
What is cancer?
Non-communicable disease, uncontrolled cell division results in the formation of a primary tumour
What are percentile charts?
A chart used to monitor growth and measurements can be compared to the expected values at a certain age
What can doctors determine from percentile charts?
Slower growth and faster growth than normal and abnormal growth
What is growth in animals?
Cell division occurs in all 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 and some adult stem cells retain their ability to differentiate
What is growth in plants?
Cell division can only occur in meristematic tissue and the rate of cell division remains the same throughout a plants life. Meristematic stem cells can differentiate into ant cell type for as long as the plant lives. Cell elongation occurs in all cells and cells expand and enlarge enabling grown of the plant
What are stem cells?
Cells that are unspecialised and capable of differentiating into a range of different cell types
What is meant by ‘differentiation’?
The process by which stem cells become specialised and some genes switch on or off, determining cell type
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?
Enables the growth and development of tissues in human embryos
What are adult stem cells?
Stems cells that can differentiate into a limited range of cell types
What is the primary function of adult stem cells?
Replacement of dead cells
Where are stem cells found in plants?
Meristems
Where is meristem tissue found?
In regions of the plant where cells are continuously dividing
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 and used to treat damage or disease
Where can embryonic stem cells be collected from?
Donor stem cells removed from embryos growth in vitro and 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 and growing organs for transplant
What are the risks of stem cell use in medicine?
Transplanted stem cells could cause damage, finding suitable stem cells donors is a difficult task, stem cells may be rejected by the body, potential side effects, long term risks of using stem cells unknown and stem cells may become contaminated during preparation and when transplanted transmit infection to the patient
What are the ethical issues related to the use of stem cells in medicine?
May lead to the production of human cloning and the embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
What is the function and structure of the cornea?
Transparent outer covering or the eye and refracts light entering the eye
What is the function and structure of the iris?
Pigmented ring of circular muscles and radial muscles and controls the size of the pupil to alter how much light enters they eye
What is the pupil?
A hole in the iris centre that allows light rays to enter the eye
What is the function and structure of the lens?
Transparent, bi-convex structure, suspensory ligaments attach the lens to a ring and refracts light, focusing it onto the retina
What is the function of the ciliary muscles and suspensory ligaments?
Change the shape of the lens (accommodation) to focus light onto the retina
What is the function and structure of the retina?
Light sensitive layer composed of rod and cone cells and converts light rays energy into neural signals which are sent to the brain via the optic nerve
What are rod cells?
Cells in the retina that are sensitive to low light intensity
What are cone cells?
Cells found in the retina that are sensitive to high light intensity (bright light) and can detect different colours
What is the function of the optic nerve?
It transmits nerve impulses to the brain from the retina
How does dim light affects the size of the pupil?
Light receptors detect dim light, circular muscles relax, radial muscles contract, pupil dilates and more light enters the pupil
How does bright light affects the size of the pupil?
Light receptors detect bright light, circular muscles contract, radial muscles relax, pupil contracts and less light enters the pupil
Why is the iris reflex important?
It prevents bright light from damaging the retina
What is accommodation?
Process by which the elastic lens change its shape to focus on heat or distant objects and light is focused onto the retina
How does the eye focuses on near objects?
Near object, ciliary muscles contract, suspensory ligaments slacken, lens becomes more convex, light is refracted more and light rays focused onto the retina
How does the eye focuses on distant objects?
Distant object, ciliary muscles relax, suspensory ligaments tighten, lens becomes less convex, light is refracted less and light rays focused onto the retina
What is long-sightedness?
Can focus on distant objects clearly and cannot focus on near objects
What are the causes of long-sightedness?
Eyeball is too short, lens is less elastic and light rays are not focussed onto the retina, instead converging behind the retina
How is long-sightedness treated?
Using a convex lens in glasses, contact lenses, replacement lenses and laser eye surgery
What is short-sightedness?
Can focus on near objects clearly and cannot focus on distant objects
What are the causes of short-sightedness?
Eyeball is too long, lens is too thick and too rounded and light rays are not focussed onto the retina, instead converging in front of the retina
How is short-sightedness treated?
Using a concave lens in glasses or contact lenses, replacement lenses and laser eye surgery
What are cataracts?
A cloudy patch forms on the lens of the eye which negatively affects visions and vision becomes blurry, difficult to see the intensity of colours, problems with glare
How are cataracts treated?
The clouded lens is exchanged for a synthetic lens during surgery
What is colour-blindness?
A deficiency of the eye that makes it difficult to distinguish between colours
What is the cause of colour-blindness?
Damage to cone cells in the retina
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 oblong at a down the spine
What is the function of spinal cord?
Connects the peripheral nervous system to the brain
What is the structure of the brain?
Consists of three main regions: cerebrum, cerebellum and medulla oblongate
What is the structure of the cerebrum?
Largest region of the brain and is divided into two hemispheres
What is the function of the cerebrum?
It’s involved in: intelligence, language, memory, emotion, visual and sensory processes
What is the structure of the each cerebral hemisphere?
Left hemisphere recurved sensory information from the right side of the body and controls muscle coordination on the right whereas the right hemisphere receives sensory information from the left side of the body and controls muscle coordination on the left
Where is the cerebellum located?
Lower region of the brain
What is the structure of the cerebellum?
It’s involved in: coordination of muscles, voluntary movement and 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 and PET scan
What is a CT scan?
A procedure that uses X-rays to produce 3D cross-sectional images of the brain
How are CT scans useful to investigate brain function?
CT scans show damaged regions of the brain and 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 injected into a patient’s bloodstream and taken up by tissues in the brain and radiation emitted by tissues detected, enabling the identification of active and inactive regions of the brain
How are PET scans useful to investigate brain function?
Show which area of the brain are active and which areas are not and comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine the function 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 and risk of further permanent damage to other 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 and enables the transmission of nerve impulses over long distances
What is the function of the dendrites and dendrons?
Carry impulses towards the cell body and dendrites provide a large surface area to receive impulses
What is the role of the myelin sheath?
Electrically insulating layer and surrounds the axon and increases the speed of impulses
What is the function of a sensory neurone?
Carries impulses from receptors to the central nervous system
What is the structure of a sensory neurone?
Long dendron carries impulses from receptors to the cell body, cell body found part way along the neurone and short axon carries impulses from the cell body to the CNS
What is the function of a motor neurone?
Canaries impulses from the central nervous system to effectirs
What is 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 neurones and long axon carries impulses from the cell body to the effectors
What is the function of a relay neurone?
Carries impulses from the sensory neurones to the motor neurones within the CNS
What is the structure of a relay neurone?
Short dendrites carry impulses from sensory neurones to the cell body and short axon carries impulses from the cell body to motor neurones
How does the CNS coordinates a response to a stimulus?
sensory receptors detects stimulus, sensory receptors sends impulses along sensory neurones to CNS, CNS coordinates response, CNS sends information to effectors along the motor neurones and effector produces a response to the stimulus
What is a synapse?
A small gaps between neurones across which a nerve impulse is transmitted via neurotransmitters
How are nerve impulses transmitted across a synapse?
Nerve impulse reaches presynaptic neurones, this triggers the release of neurotransmitters, neurotransmitters diffuse across the synapse, they bind to receptors on the postsynaptic neurone and this stimulates an impulse in the postsynaptic neurone
Why do synapses slow down the transmission of nerve impulses?
It takes time for the neurotransmitters to diffuse across the synapse and bind to receptors on the postsynaptic neurone
What is a reflex?
Automatic response to a stimulus by the body, involuntary and protective mechanisms
What is the reflex arc?
Stimulus -> sensory receptors -> sensory neurones -> relay neurones -> motor neurones -> effector -> response
