5.5 - Plant and animal responses Flashcards
Why does the sympathetic system inhibit digestion?
The sympathetic system prepares the body for activity – oxygen and nutrients must be supplied to the muscles. Therefore blood is diverted towards the muscles and away from the digestive system.
Explain why relay neurones have multiple connections?
This enables a large number of alternative nervous pathways to be created. One neurone will receive signals from many sources and can contribute to many pathways by sending the impulse to many other regions of the brain or effectors.
How do stretch receptors convert the movement of the muscle to an action potential?
The stretch receptor maintains a potential across its membrane – the membrane is polarised. When the muscle is stretched the membrane of the stretch receptor is deformed. This opens sodium ion channels and sodium ions flow into the receptor cell causing depolarisation. This depolarisation is a generator potential. If sufficient ions enter the cell the generator potential reaches the threshold and causes more sodium ion channels to open. This produces the action potential.
Accelerating the heart rate is likely to produce more carbon dioxide in the heart muscle. What effect might this have on the heart rate? What type of feedback is this?
It is positive feedback because increasing the CO2, may increase the heart rate.
What stretches out the muscle after contraction in
b) the blood vessels?
The recoil of the elastic fibres in the walls of the blood vessels and the pressure of the blood in the vessels.
What stretches out the muscle after contraction in the walls of the heart
The recoil of the elastic fibres in the walls of the blood vessels and the pressure of the blood in the vessels.
What stretches out the muscle after contraction in
c) the airways
The recoil of the elastic fibres in the walls of the airways and the elasticity of the cartilage.
Describe three ways in which a neuromuscular junction is similar to a synapse.
They both use acetylcholine as a neurotransmitter, both stimulated by action potentials, both transmit signals across small gap(cleft).
Identify precisely where the three types of muscle can be found in the chest cavity.
Cardiac muscle is in the walls of the heart chambers, smooth muscle is in the walls of the airways and blood vessels, striated muscle is in the intercostal muscles.
