Homeostasis And Response Flashcards
Define homeostasis.
The regulation of the conditions inside an organism and cells to maintain a stable internal environment, in response to changes in both internal and external conditions.
Why is homeostasis important ?
Cells need the right conditions in order to function properly, including the right conditions for enzyme action.
What 3 things are controlled in your body through homeostasis ?
Body temperature, blood glucose level and water content.
Define automatic control systems found in the body.
Systems that regulate your internal environment. E.g. nervous and hormonal communication systems.
What 3 main components are all automatic control systems made up of ?
Receptors, coordination centres and effectors.
How do our body’s automatic control systems keep our internal environment stable ?
By using a mechanism called negative feedback.
When is negative feedback used in order to keep a stable internal environment ?
When the level of something ( water content, body temperature or blood glucose levels ) get too high or low the body uses negative feedback to bring it back to normal.
How does the automatic control system react when the level of something ( water or temp ) gets too high ?
1) the receptor detects a stimulus where the level is too high
2) the coordination centre receives and processes the information, then organises a response.
3) the effector produces a response which counteracts the change and restores the optimum level by decreasing the level.
How does the automatic control system react when a stimulus is detected and the level is too low ?
1) the receptor detects the stimulus where the level is too low of something.
2) the coordination centre receives and processes the information, then organises a response.
3) the effector produces a response, which counteracts the change and restores the optimum level with an increase of the level of something.
How might the effector cause negative feedback to be ineffective ?
And How is this regulated to make sure it does not happen ?
This is because the effectors will continue to produce a response for as long as they’re stimulated by the coordination centre. Therefore the level of change may be too much and not restore the internal environment to an optimum level.
However the receptor regulates this problem by detecting the level change if it becomes too different and negative feedback starts again.
What is the difference to how single - celled organisms respond to their environment and how multicellular organisms respond to changes their environment ?
A single celled organism can just respond to its environment, but the cells of multicellular organisms need to communicate with each other first m.
Why have nervous and hormonal communication systems been evolved aa multicellular organisms have Evolved ?
This is because multicellular organisms need to communicate with each other first in order to make a change to its environment to restore the internal environment to optimum levels in response to an external stimuli therefore need communication systems.
What are the 4 parts of the Nervous system ?
1) the central nervous system
( the brain and spinal cord )
2) sensory neurones
3) motor neurones
4) effectors
Explain the function / role for each of the 4 parts of the nervous system.
1) the CNS - connected to the body by sensory neurones and motor neurones.
2) sensory neurones - carry information as electrical impulses from the receptors to the CNS.
3) motor neurones - neurones that carry electrical impulses from the CNS to effectors.
4) effectors - all the muscles and glands, which respond to nervous impulses.
Define what a receptor does.
Cells that detect stimuli
Define what an effector does.
Muscles or glands which Respond to nervous impulses and brings about a change.
Describe how a muscles job as an effector is different to how a gland acts as an effector.
- muscles contract in response to a nervous impulse.
- glands secrete hormones
Describe how the central nervous system ( CNS ) coordinates a response in relation to a change in the environment.
1) a change in the environment occurs, either internal or external ( the stimulus)
2) the receptors in an organism or cell are stimulated.
3) sensory neurones carry the information from the receptors to the CNS
4) the CNS coordinates a response.
5) the CNS then sends information to the muscles/ glands in an organism along motor neurones
6) the muscles/ glands produce a response in order to survive.
What is the connection between two neurones called ?
A synapse
How is a nerve signal transferred from one neurone to another ?
Transferee by chemicals which diffuse across the synapse ( gap between two neurones)
What happens after a nerve signal is transferred from one synapse to another via diffusion ?
The Chemicals that had transferred the previous nerve signal then set off a new electrical signal in the next neurone.
Write a definition for a reflex.
Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain that can reduce the chances of being injured.
What is the passage of information in a reflex (from receptor to effector) called ?
refelex arc
What parts of the CNS do neurones in a reflex arc go through ?
they go through the spinal cord or through an unconscious part of the brain.
Describe the pathway of the reflex from stimulus to effector.
1) when a stimulus is detected by receptors, impulses are sent along a sensory neurone to the CNS.
2) When the impulses reach a synapse between the sensory neurone and a relay neurone, they trigger chemicals to be released which then cause impulses to be sent along the relay neurone.
3) when the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. chemicals are released and cause impulses to be sent along the motor neurone.
4) the impulses then travel along the motor neurone to the effector ( muscle or gland ).
5) the muscle contracts or the gland secretes hormones very quickly in response to the original stimulus to protect ourselves.
define reaction time.
the time it takes to respond to a stimulus.
Describe the steps of the practical to measure reaction time.
1) the subjects arm should be resting on the edge of the table.
2) hold a ruler vertically between there thumb and finger making sure the the zero end is level with the thumb and finger.
3) let go without giving any warning
4) the subject should try top catch the ruler as fast as possible.
5) the reaction time can then be measured by the number on the ruler where its caught.
6) repeat test several times to calculate a mean distance that the ruler fell.
7) steps 1-5 can then be repeated with different factors such as caffeine and the amount of sleep.
8) make sure variable are controlled ( give examples )
9) describe a risk and precaution of carrying out the experiment.
describe the term hormone.
chemical molecules released directly in to the blood.
how are hormones produced ?
hormones are secreted by various glands.
what is the duration of a hormone response like ?
long lasting effects.
what is the duration of a hormone response like ?
long lasting effects.
Where is the pituitary gland found ?
in the middle of the brain.
What are the functions of the pituitary gland ?
- produces many hormones that regulate body conditions.
- called the master gland because the hormones produced by this gland stimulate other glands to release there specific hormones.
Where are the ovaries found ?
either side of the uterus.
what is the function of the ovaries ?
produces oestrogen in females which is involved in the menstrual cycle.
Where are the testes found ?
underneath the penis.
What is the function of the testes ?
produces testosterone in males which controls puberty and sperm production.
Where is the thyroid gland found ?
in the front of the neck.
What is the function of the thyroid ?
produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
Where is the adrenal gland located ?
above the kidneys
What is the function of the adrenal gland ?
produces adrenaline, which is used to prepare the body for a flight or fight response .
Where is the pancreas located ?
behind the stomach and in front of the spine.
What is the function of the pancreas ?
produces insulin, which is used to regulate the blood glucose level.
Where is the pituitary gland found ?
in the middle of the brain.
List the 6 main glands.
Pituitary glands, Thyroid gland, ovaries, testes, pancreas, adrenal gland and
compare the endocrine and nervous system in terms of the speed of response.
hormone - slower than the nervous system
nerve - very fast action
compare endocrine and the nervous system in terms of how the signal is carried.
nervous system - neurones
endocrine system - bloodstream
What type of signal does the endocrine system produce ?
chemicals (hormone)
What type of signal does the nervous system produce ?
electrical impulse
Compare the endocrine system and the nervous system in terms of the duration of the response.
nervous system - short
endocrine - long
What kind of effector carry’s out an endocrine system response ?
a gland
What kind of effector(s) carry out a nervous system response ?
a muscle or gland
True or false. Hormones act on a very precise area with their response.
False - nerves act on a very precise area whilst hormones act in a ore general way.