F214 Notes

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Biology Unit F214:
Spread: Specification: Content: Other:
1.1.1 Outline the need for External Environments: The environmental change is a stimulus and the Definitions:
communication systems way in which the organism changes its physiology or behaviour is its A stimulus is any change in the
within multicellular response. environment that causes a
organisms, with response
reference to the need to Internal Environments: The environment of cells in multicellular organisms A response is a change in
respond to changes in is tissue fluid. As cells undergo various activities they may produce behaviour or physiology as a
the internal and external unwanted products, such as CO2. Carbon dioxide can build up in the tissue result of a change in the
environment and to fluid and thus disrupt enzyme activity by changing of ph. Therefore this environment.
coordinate the activities accumulation of excess wastes must act as a stimulus to cause removal of Communication:
of different organs. these waste products. Within Cells:
mRNA is produced by
State that cells need to Coordination: Good communication system will have: transcription in nucleus but is
communicate with each Cover the whole body `read at ribosomes
other by a process called Enable cells to communicate with each other cAMP produced by adenylyl
cell signalling. Enable specific communication cyclase but activates other
Enable rapid communication enzymes in cytoplasm
State that neuronal and Enable both short-term and long-term responses Between cells:
hormonal systems are Synthetic PGs are used:
examples of cell Cell Signalling: 2 major systems of communication that work by cell o Reduce hypertension
signalling. signalling: o Control symptoms of
1. The Neuronal system is a network of neurones that communicate asthma
across synapse junctions. (short-term; rapid) Between tissues:
2. The Hormonal system uses the blood for signals. {Long-term; Typical communication between
Slow(sometimes fast, e.g. Adrenaline)} hormones(e.g. Oestrogen,
cortisone, homeostasis)
Between individuals of same species:
Typical Pheromones
1.1.2 Define the terms Homeostasis: Many living organisms have to keep a great number of Definitions:
negative feedback, conditions constant inside the body. These may include: Homeostasis is the maintenance
positive feedback and Temperature: of the internal environment in a
homeostasis. o Low temperatures -> slow down metabolic reactions constant state despite any
o High temperatures -> can cause proteins to denature ( external changes.
Explain the principles of causing damage to enzymes and plasma membranes Negative feedback is a process
homeostasis in terms of Amount of H20: that brings about a reversal of any
receptors, effectors and o Low water supply -> causes H20 to move out of cells by change in conditions. It ensures
negative feedback. osmosis, which causes metabolic reactions to slow that an optimum steady state can
down/stop be maintained, as the internal
o High water supply -> causes water to move into cells by environment is returned to its
osmosis, which can cause cells to swell/burst original set of conditions after any
Concentration of glucose: change. It's essential for
o Low supply of glucose -> causes respiration to slow homeostasis.
down/halt, as the cells now have no energy source Positive feedback is a process that
o High supply of glucose -> causes H20 to move out cells by increases any change detected by
osmosis, which can cause metabolic reactions to slow the receptors. It tends to be
down/stop harmful and doesn't lead to
Others include: Salt concentration, blood pressure and CO2 homeostasis.
Principles of Homeostasis (1): A negative feedback mechanism requires a
receptor and an effector and an efficient means of communication
between them. The receptor monitors the factor that's being in control. If
value of factor is not within a suitable range, then the receptor
communicates with the effector to cause an action that brings the factor
back to its norm.
Stimulus -> Receptor -> communication pathway -> effector -> response
Note: Since there is a short time delay between change in factor, detection
by the receptor, communication with the effector and the action of the
effector, the control does not happen instantly. Resulting in an oscillation
around a set point. Fact File:
Substances produced during
Number of structures required: certain bacterial infections
Sensory receptors, such as thermo receptors or glucose conc. temporarily shift the core body
receptors. These monitor conditions inside the body. temp. above 37^C. The
A communication system such as the nervous system or the hormonal substances are called pyrogens.
system. This acts by signalling between cells. Used to transmit They affect the heat loss centre in
information from the receptors to the effector cells. This may also not the hypothalamus. The infected
pass through a coordination centre such as the brain. person appears flushed and
Effector cells, such as liver cells or muscle cells. This reverses the produces a lot of sweat...both
response detected by the receptor cells. symptoms of a fever. If

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Biology Unit F214:
Principles of Homeostasis (2): A positive feedback mechanism tends to homeostatic control breaks down,
push the parameter further and further away from the norm, rather than then positive feedback reinforces
keeping it constant. Examples include: further increase in core body
If a person breathes air that has a very high conc. of CO2 content, temperature with possible fatal
producing a high conc. of CO2 in the blood. This is sensed by the CO2 results.…read more

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Biology Unit F214:
Control of temperature regulation:
Endotherms monitor the temperature of their blood in the hypothalamus of
the brain. If the core temperature falls below normal, hypothalamus sends
signals to reverse the change. This will involve several changes:
Increased rate of metabolism in order to release more heat from
exergonic reactions
Release of heat through extra muscular contraction
Decreased loss of heat to the environment
If core temp rises above normal, hypothalamus will act to reverse change.…read more

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Biology Unit F214:
1.1.5 Outline the roles of Sensory Receptors: Some sensory receptors are specialised to detect Definitions:
Sensory receptors in changes in our surroundings. They are energy transducers that change one A polarised membrane is one that
mammals in converting form of energy to another. Each change in energy levels in the environment has a potential difference across
different forms of is called a stimulus. Whatever the energy, sensory receptors convert it into it.…read more

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Biology Unit F214:
just outside the spinal cord. potential
Intermediate neurones, sometimes called relay neurones have their cell The stronger the stimulus, the
bodies and cytoplasmic processes inside the CNS. They are adapted to carry greater is the generator potential
impulses from and to numerous other neurones.…read more

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Biology Unit F214:
channels in the membrane open. Na+
5 6 that was pumped out now goes back
into the cell. They do this because there
is an electrical gradient for them ­ the
membrane has a more +ve charge on
4 the outside than on the inside, so the
7 ions tend to move to balance the
charges.…read more

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Biology Unit F214:
The myelin sheath: It's made up largely of lipids, together with some o Repolarization of the
proteins. Myelin sheath contains myelin, a phospholipid which does not membrane when K+
conduct an electrical current. There are no transmembrane ion movement leave the axon
across myelinated membranes. Thus, the ionic movements that create an Information conveyed along a
action potential cannot occur over much of the length of the neurone.…read more

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Biology Unit F214:
Transmission across the synapse (chemical synapses): glutamate occur only in the brain.
An action potential arrives at the synaptic knob Neuromuscular junction:
The voltage-gated Ca²+ channels open It's a synapse between the end of a
Ca²+ diffuse into the synaptic knob motor neurone and a muscle.…read more

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Biology Unit F214:
and eyes. In the future, when you hear the voice, information flowing synaptic neurones. The numerous
from your ears along this pathway automatically flows into the other synaptic connections allow the
pathway too, so that your brain `pictures' the face that goes with the cell to combine different sources
voice. of information before responding.
Above all it's the pathways created by synapses that enable the nervous Its response will depend on the
system to convey a wide range of messages.…read more

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Biology Unit F214:
1.1.10 Define the terms Signalling by using hormones: Many animals, including mammals, also have Definitions:
endocrine gland, another communication system (other than the nervous system), the Hormones are molecules that are
exocrine gland, endocrine system, which transmits information from one cell or organ to released by endocrine glands
hormone and target another. Thus system is made up of endocrine glands, which secret directly into the blood. They act as
tissue chemicals called hormones.…read more





This is really a great, sound set of notes, specific to the spec and full of detail thankyou!!


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