B2 - cells and control Flashcards
what part of cell contains chromosomes
nucleus
what are chromosomes
coiled up lengths of DNA molecules
how many copies of chromosomes do cells have
two copies of each, theyre diploid cells, one from mother and one from father
how do cells divide
cell cycle, the stage where cells actually divides is called mitosis
what is mitosis
asexual reproduction, used in multicellular organisms to grow/ replace damaged cells
what are the stages of the cell cycle
- interphase
- prophase
- metaphase
- anaphase
- telophase
- cytokenisis
which stages of the cell cycle are part of mitosis
- prophase
- metaphase
- anaphase
- telophase
(PMAT)
interphase
- DNA in the chromosomes duplicates
- Sub cellular structures also duplicate
prophase
- DNA in chromosomes condenses
- Nuclear membrane, breaks down chromosomes lie free in the cytoplasm
metaphase
chromosomes line up along the centre of the cell
anaphase
- chromosomes pulled to opposite ends of the cell
telophase
- New nuclear membrane forms around the chromosomes at each end of the cell
cytokinesis
cytoplasm and cell membrane divide forming two genetically, identical daughter cells
what is growth
increase in size or mass
cell differentiation
cell becomes specialised for a job
cell division
mitosis
cell elongation
plant cell expands causing plant to grow
how are tumours formed
when cell begins to divide uncontrollably due to a change in one of the genes that controls cell division resulting in a mass of cells
how does cancer occur
when a tumor invades and destroys healthy tissue
what are percentile charts used for
assess a childs growth over time to show an overall pattern of development and highlight any problems
what 3 measurements are used to monitor a babies growth
- height
- weight
- head circumference
which percentile is average
50%
what are stem cells
undifferentiated cells, can divide by mitosis forming new cells which can then differentiate
embryonic stem cells
found in early human embryos, can divide and produce any kind of cell
adult stem cells
only found in places such as bone marrow and arent as versitile as embryonic stem cells, can only produce certain types of cell
what are adult stem cells used for
replace damaged cells eg. new skin cells or blood cells
where are stem cells found in plants
meristem
what is meristem
found in growing areas of plants eg. roots and shoots
Contains undifferentiated cells (stem cells)
what do meristems do
produce unspecialised cells that can differentiate into any kind of cell needed (like embryonic cells) as long as the plant lives
medical advantages of stem cells
- cure diseases eg. Sickle cell anaemia
- extract stem cells from embryos used to differentiate into specific specialised cells
- replace damaged or diseased cells
risks of using stem cells medically
- tumor development
- transmitting diseases already inside cells
- rejection
what is a stimulus
a change in environment detected by sensory receptors
what is response
A change in behaviour in response to a stimulus.
What is the central nervous system (CNS) made of?
brain and spinal cord
What is the nervous system for?
It is an organ system that allows allows your body to communicate, using electrical signals called impulses.
What is a sense organ? Give an example.
An organ that contains receptor cells to detect stimuli. E.g. eyes
How does the body create a response to a stimulus?
Sense organs contain receptor cells. When these receptor cells detect a stimulus, they create impulses which usually travels to the brain. The brain then processes this information and can send impulses to other parts of the body to cause a response.
What are different steps to get from a stimulus to a response for a normal action?
Stimulus
- receptor
- sensory neurone
- CNS
- motor neurone
- effector
Response
what happens when a stimulus is detected by a receptor
info is converted to an electrical impulse and sent along sensory nurones to CNS
what is reaction time
time it takes to respond to a stimulus
3 types of nurone
motor, relay and sensory
sensory nurone
- long dendron carries impulse from receptor to cell body
- short axon carries impulse from cell body to CNS
motor nurone
- many short dendrites carry impulses from CNS to cell body
- long axon carries impulse from cell body to effector cells
relay nuron
- many short dendrites carry impulses from sensory nurones to cell body
- axon carries impulse from cell body to motor nurone
myelin sheath
insulates neurone to speed up the transmission of electrical impulses
- sensory, motor and relay can be myelinated or unmyelinated
synapse
connection between two nurones
why does transmission of nervous impulse slow down at a synapse
diffusion of neurotransmitters across the gap takes time
what is a reflex
- rapid, automatic responses to a stimuli that bypasses the brain
- can reduce chance of injury
reflex arc
the passage of information in a reflex (receptor to effector)
where do reflex arcs go through in nurones
spinal cord or an unconcious part of brain
Pathway of a reflex arc
Stimulus, receptor, sensory neuron, relay neurone, motor neurone, effector ——> RESPONSE
how to calc % change
((final value-start value)/start value)x100
What happens during the reflex arc?
- receptor detects, a stimulus initiating an electrical impulse
- The electrical impulse passes along the sensory relay and motor neurons to the effector
- The effector carries out a response, e.g. muscle contracts or gland secretes hormone
What happens at the synapse?
- neurone releases neurotransmitter that diffuses across the synapse
- Neurotransmitter attaches to next neurone triggering another electrical impulse
Where are relay neurones
In the spinal chord
Why are percentile charts used
- Can highlight developmental problems
- Useful as action can still be taken, e.g. change in diet or surgery
