+
Related Flashcards
Related Topics
Cards In This Set
| Front | Back |
|
Why do multicellular organisms need communication systems? Why does there need to be a specific range of regulation?
|
As an organism grows and
develops more cells, it becomes more difficult for the innermost cells/tissues
to gain nutrients and dispose of waste. Changes
in both the internal and external environments can lead to these fluxuations
in; pH, temperature and the toxins present. In order for these changes to
be reversed and regulated they must be monitored, for which a communication
system must be in place.
This results in the development of a series of internal systems, which all need to regulated within a specific range. This "range" is essential to the cellular activities (such as metabolic processes) as they tend to require enzymes that will denature once the conditions fluxuate too far from the constant. |
|
Why do animals need to respond to changes in external environment?
Give an exmple |
In order to increase chances of survival,
animals need to respond to changes in their external environment. As an
external environment changes, it places stress on the organism and it must
change its behaviour or physiology to reduce the stress. For example; a cooler
environment will increase heat loss, if the organism is to stay active and
alive, the changes must be made.
|
|
What must a communication system be able to do?
|
This "system" must;- cover the whole body- enable cells to communicate- detect and respond to
changes- allow long term and short term responses.
|
|
What is a stimulus, receptor and effector.
Describe and give examples of the two types of receptors. |
- The environmental change is called a stimulus; the change in
behaviour or physiology is its response.
-
A receptor detects the stimuli; they are specific and only
detect particular stimulus e.g. light, pressure of glucose concentration.
- Some receptors are cells such as photoreceptors, which connect
to the nervous system.
- Some receptors are proteins on cell surface membranes e.g.
glucose receptors are proteins found in the cell membranes of some pancreatic
cells.
-
Effectors are cells that bring about a response to a stimulus,
to produce an effect.
Effectors include muscles cells and cells found in
glands, such as the pancreas.
|
|
What happens in the environmental change is slow? Give an example.
What happens if it is quick? Give an example. |
-
If the environment change is slow the change will elicit a
gradual response. For example animals having thicker coats in winter. The
different coats adapt the animal to the changing conditions.
- If the environment changes much more quickly, such as day-to-day changes or light change, the change must again be monitored and the changes are faster. |
|
Why must internal environment be controlled, with reference to cells.
|
-
As cells undergo their various metabolic activities they use
up substances and produce products. Some of these products may be unwanted or
toxic; these substances diffuse out of the cells into the tissue fluid.
Therefore the activities of the cells alter their own environment.
|
|
How is tissue fluid composition maintained?
|
-
The blood maintains the composition of the tissue fluid. Blood
flows throughout the body and transports substances to and from the cells, any
waste of toxins accumulation in the tissue fluid are likely to enter the blood
and be carried away. They must be excreted in order to prevent accumulation.
|
|
Why is it important to mointor wastes and substances in the blood?
|
-
It is important that the concentrations of wastes and all
substances in the blood are monitored closely. This ensures that the body does
not excrete too much of any useful substance but removes enough of the wastes
to maintain good health. It also ensures that all the cells of the body are
supplied with the substrates they need.
|
|
What is cell signalling?
Describe the two major systems that use cell signalling |
Cells communicate with each other by a process called cell
signalling, one cell will release a chemical, which is detected and responded
to by another cell.
Neuronal and Hormonal. - The neuronal system is an interconnected network of neurones that signal to each other across synapse junctions. The neurones can conduct a signal very quickly and enable rapid responses to stimuli that may be changing quickly. - The Hormonal system uses the blood to transport its signals. Cells in an endocrine organ release the signal directly into the blood. It is carried all over the body to target cells. The hormonal system enables longer-term responses to be coordinated. |
|
Define Homeostasis
|
Homeostasis can be defined as keeping the
internal environment constant despite external changes. It is vital for your
cells to function properly, especially the core body temperature. Many living
organisms have to keep a great number of conditions constant inside the body.
These may include: Body temperature, blood glucose concentration, water
potential of the blood, blood salt concentration, water potential of the blood,
blood pressure and carbon dioxide concentration.
|
|
Define Negative Feedback
What must there be for negative feedback to work effectively? |
The reversal of a change in the internal
environment to return to a steady state or optimum position.
- For negative feedback to work effectively there must be a complex arrangement of structures that are all coordinated through cell signalling. These structures are part of a standard pathway that is used to produce a suitable response to a stimulus. |
|
Describe the standard response pathway.
|
Stimulus -> Communication pathway (cell signalling) -> response.
|
|
Name the three structures required for negative feed back pathway to work and describe them.
|
-
Sensory receptors, such as temperature receptor of glucose
concentration receptors. These receptors are internal and monitor conditions
inside the body. If they detect a change they will be stimulated to send a
message.
-
A communication system such as the nervous system or the
hormonal system. This acts by signalling between calls. It is used to transmit
a message from receptor to effector cells.
-
Effector cells, such as liver or muscle cells. These cells
will bring about a response that reverses the change detected by they receptor
cells.
|
|
Define Positive feedback
Give an example |
-
Positive feedback is used to stimulate an increase in a
change.
An example is seen at the end of pregnancy to bring about cervix dilation. As the cervix beings to stretch the change is signalled to the anterior pituitary gland, stimulating it to secrete the hormone oxytocin. Oxytocin increases the uterine contractions, which stretch the cervix more, which causes secretion of more oxytocin. Once the cervix is fully dilated the baby can be born. |
|
Why do we need to maintain body temperature?
|
The need to maintain body temperature:
Changes in body temperature can have dramatic effect upon
the structures of proteins, including enzymes.
-
Enzymes are globular proteins and their structure is very
specific to their function.
-
The core body temperature is very important and must stay at
the optimum temperature.
|
