Co-ordination and Response CHECK ALL Flashcards
What is homeostasis?
The maintenance and self-regulation of a constant internal environment
Which physiological factors are controlled in mammals through homeostasis?
Body temperature
Water concentration
Glucose concentration
Blood pH
Levels of metabolic waste in blood
Carbon dioxide concentration
What are the four things which a co-ordinated response requires?
A stimulus (e.g. change in body temperature)
A receptor (e.g. receptor cells)
A co-ordination centre (e.g. brain or spinal chord which receives and processes information from receptors
An effector (e.g. muscle shivering) which brings about the response
What is the difference between a phototrophic response and a geotrophic response in plants?
A photrophism is a directional growth-response to the stimulus of light
A geotrophism is a directional growth-response to the stimulus of gravity
What are the phototrophisms which happen in plants and are the responses positive or negative?
Plants will grow their leaves towards the sun (to absorb more light for photosynthesis), this is a positive photrophism
Plants will grow their roots into the soil away from the sun, this is a negative phototrophism
What are the geotrophisms which happen in plants and are the responses positive or negative?
Plants grow their shoots up against gravity, this is a negative geotropism
Plants will grow their roots down (to anchor the plant and absorb nutrients), with gravity, this is a positive geotropism
What is auxin and what are its effects on plants?
Auxin is a growth regulator (similar to a hormone) which coordinates growth responses such as geotropisms and phototropisms
In shoots, auxin promotes cell elongation (so growth), in roots, auxin inhibits cell elongation (so less growth)
What determines auxin distribution in a plant and what happens to the plant as a result of this distribution?
In shoots, gravity causes auxins to be more concentrated in the lower side of the shoot, therefore stimulating growth in this area and causing the shoot to grow upwards
Also in shoots, light will cause auxins to collect on the shady side, stimulating growth in this area and causing the shoot to bend towards the light
In roots, gravity causes auxins to be more concentrated on the lower side, which inhibits growth in this area meaning the upperside will grow faster, causing the root to bend downwards towards the nutrients
What are the two control systems our body use to respond to stimuli?
The endocrine (hormonal) system
The nervous system
How does the encdocrine (hormonal) system work generally?
Chemical substances known as hormones are produced and released by glands
These hormones are carried by the blood and circulate the whole body
The are received by specific receptors and instigate a change on the target organ
What does the central nervous system consist of?
The brain
The spinal chord
What is the central nervous system linked to and what does that consist of?
It is linked to the peripheral nervous system
It contains all the nerves in the body
What are the three types of neurones?
Sensory
Relay
Motor
How does the nervous system work to carry out a response?
A stimulus is received by sensory neurones (in nerves)
When stimulated, the sensory neurone produces an electrical signal which travels along other sensory neurones (in nerves) to the co-ordinator (spinal chord or brain)
In the CNS, the electrical impulse is transferred to a relay neurone
The relay neurone links to a motor neurone, and along motor neurones the impulse travels until it reaches the effector, e.g. a muscle
Why are neurotransmitters needed?
The neurones do not come into direct compact to eachother, instead, the junction where the dendrites meet is called a synapse (where there is a small gap between the neurones)
Since the electrical impulse cannot jump the gap, it is briefly converted into a chemical messenger known as a neurotransmitter
