Response to Stimuli Flashcards
(45 cards)
Describe how a Pacinian corpuscle works
During resting potential sodium channels are too narrow to allow sodium ions through;
When pressure is applied, membrane stretches;
Sodium ion channels open;
Sodium ions enter causing depolarisation of membrane;
Causing generator potential which creates an action potential
Describe how increased sympathetic stimulation increases cardiac output.
Increased stimulation of SAN;
Increase in heart rate;
Increase in stroke volume
Describe how rod cells act as transducers of energy.
Convert light energy to electrical energy;
Light energy causes change in rhodopsin
Describe how the Pacinian acts as a transducer of energy.
Converts mechanical energy to electrical energy
The diameter of the pupil is reduced in bright light. Describe the part played by the autonomic nervous system in reducing the diameter.
Bright light stimulates impulses from eye to brain;
Parasympathetic system;
Stimulates contraction of circular muscles
Earthworms move away from light. Why does this increase their chances of survival?
Leads them into the soil;
So they can conserve water, find food and avoid predators.
Explain how a Pacinian corpuscle produces a generator potential in response to external pressure.
Stretches membrane;
Sodium ion channels open;
Sodium ions enter causing depolarisation
Explain how retinal convergence enables a person to see in dimly lit conditions.
Action potentials or generator potentials from several receptors sent to single synapse;
Sufficient neurotransmitter released;
Action potential more likely to be generated in this neurone
Explain how stimulation of chemoreceptors during exercise results in a change in heart rate.
Increase in carbon dioxide from respiration;
Decrease in blood pH detected by chemoreceptors;
More impulses to medulla;
More impulses from medulla along sympathetic nerve;
To SAN, increasing heart rate
Explain how stimulation of pressure receptors during exercise results in a change in heart rate.
When blood pressure is higher than normal, they send an impulse to the medulla;
Fewer impulses from medulla along parasympathetic nerve;
To SAN, decreasing heart rate;
When blood pressure is lower than normal, they send an impulse to the medulla;
More impulses from medulla along sympathetic nerve;
To SAN, increasing heart rate
Explain the effect of the parasympathetic division of the autonomic nervous system on cardiac output.
Decreases activity of SA node;
Decreases rate of contraction of heart muscle
Explain the importance of reflex actions.
Avoids damage to tissues;
Helps escape from predators
Explain the trichromatic theory of colour vision.
three types of cones;
each sensitive to different wavelength
Explain why it takes time for the rod cells to recover their sensitivity to light after moving into darkness.
rhodopsin broken down by light;
time for resynthesis;
The heart muscle is myogenic. What does this mean?
The muscle contraction originates from within the heart muscle itself
Increased intensity of exercise leads to an increased heart rate. Explain how.
Carbon dioxide detected by chemoreceptors;
Changes to heart rate controlled by medulla;
More impulses to SAN
In humans, both sympathetic and parasympathetic divisions of the autonomic nervous system influence the secretion of saliva. When food is in the mouth, increased
parasympathetic stimulation of the salivary glands results in increased secretion of saliva. Explain the benefit of increased sympathetic stimulation of the salivary glands
once the food has been swallowed.
Will reduce secretion of saliva;
And prevent unnecessary expenditure of energy
The iris of the eye contains antagonistic muscles which control the diameter of the pupil. Use your knowledge of the iris muscles to explain what is meant by antagonistic
muscle action.
radial and circular muscles in iris;
opposing action = antagonistic;
radial contraction increases pupil diameter / circular contraction
reduces (or vice versa for iris).
A person looks at two spots of blue ink on a piece of white paper in bright light. The two spots are close together. Under these conditions, the person can clearly see two blue, circular spots.
Explain how rays of light from a spot are made to form a distinct circular image on the retina.
Correct reference to refraction;
By cornea and/or lens;
Shape of lens changes
Neurones of type A are found in the autonomic nervous system. The autonomic nervous system consists of the sympathetic division and the parasympathetic division.
Suggest the effect that stimulation by neurones of the sympathetic division would have on the diameter of arterioles leading to skeletal muscle. Explain your answer.
Dilates;
More blood to muscles
As well as pulling the finger away, the gardener also feels pain caused by the thorn. Explain how she becomes aware of the pain.
impulses to brain;
sensory areas (in brain);
processing by association area
Explain what the results of cutting the sympathetic and parasympathetic nerves demonstrate about the control of resting heart rate.
Resting heart rate controlled by both divisions;
Heart rate changes when parasympathetic/sympathetic nerve cut;
Larger change in heart rate when parasympathetic nerve is cut
Reflexes are described as being rapid, automatic responses. Use the information in the diagram to explain those features of a reflex arc which result in the response being rapid and automatic.
Rapid because only involves three neurones;
Automatic because same pathway used each time;
no thinking involved
Rod cells allow us to see objects in dim lights. Explain how the connections of rod cells to neurones in the retina make this possible.
Several rods have connections with one neurone;
Generator potentials exceed the threshold;
Individual generator potentials do not exceed the threshold
