15.1. Control and coordination in mammals
A subsection of Biology, 9700, through 15. Control and coordination
Listing 10 of 98 questions
Outline the roles of sensory receptor cells in the mammalian nervous system. shows the changes in potential difference (p.d.) across the membrane of a receptor cell over a period of time. The membrane was stimulated at time A and at time B with stimuli of different intensities. –80 –60 –40 –20 +20 +40 +60 time / ms stimulus A stimulus B membrane potential / mV threshold potential threshold potential E D C D C State which of the letters C, D and E on correspond to each of these events. You may use each of the letters C, D or E once, more than once or not at all. The Na+ / K+ pump is operating The voltage‑gated Na+ channels are open The voltage‑gated K+ channels are open Explain why stimulus A did not result in an action potential being produced whereas stimulus B did. Describe the importance of the refractory period in the transmission of action potentials. Describe how action potentials are transmitted along a myelinated axon.
9700_w18_qp_43
THEORY
2018
Paper 4, Variant 3
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Voltage-gated channels are involved in the generation of an action potential. is a diagram of the voltage-gated channels of sodium ions and potassium ions in the membrane of an axon. The channels are shown in three different states, 1, 2 and 3. state tissue fluid axon cytoplasm state state Key voltage-gated Na+ channel voltage-gated K+ channel Na+ K+ is a diagram of different phases of an action potential in an axon. The phases are labelled A, B, C, D, E, F and G. –80 –60 –40 –20 +20 +40 time / ms membrane potential / mV A B C D E F G Complete Table 9.1 to match each of the listed phases of the action potential with the appropriate state of the voltage-gated channels: 1, 2 or 3. Table 9.1 phase of action potential state of voltage-gated channels A C E F G Many neurones are surrounded by myelin sheaths. Describe and explain the role of the myelin sheath in the transmission of an action potential.
9700_w22_qp_42
THEORY
2022
Paper 4, Variant 2
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Green lacewings are a family of insects with more than 1300 species. The common green lacewing, Chrysoperla carnea, is shown in . Green lacewings have sense organs, known as tympanal organs, that detect sound. The tympanal organ of green lacewings has evolved to detect the high frequency sounds that bats make when they are hunting. Bats eat green lacewings. When a green lacewing senses the presence of a bat, it moves away or closes its wings in flight to escape. Outline how the tympanal organ of green lacewings could have evolved by natural selection. When high frequency sound is detected, the receptor cells in the tympanal organ stimulate the transmission of impulses in sensory neurones. Describe the sequence of events that results in an action potential in a sensory neurone. The first event in the sequence has been given for you. Calcium ions enter the cytoplasm of the receptor cell Two species of green lacewing, C. carnea and C. downesi, evolved from a common ancestor. The two species have populations with overlapping distributions in parts of North America. Table 9.1 shows a comparison of the characteristics of overlapping populations of the two species. Table 9.1 characteristic C. carnea C. downesi breeding months June to September April to May courtship song song with a regular rhythm song with no regular rhythm colour light green dark green Suggest how speciation occurred to produce the two different species of green lacewing.
9700_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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Green lacewings are a family of insects with more than 1300 species. The common green lacewing, Chrysoperla carnea, is shown in . Green lacewings have sense organs, known as tympanal organs, that detect sound. The tympanal organ of green lacewings has evolved to detect the high frequency sounds that bats make when they are hunting. Bats eat green lacewings. When a green lacewing senses the presence of a bat, it moves away or closes its wings in flight to escape. Outline how the tympanal organ of green lacewings could have evolved by natural selection. When high frequency sound is detected, the receptor cells in the tympanal organ stimulate the transmission of impulses in sensory neurones. Describe the sequence of events that results in an action potential in a sensory neurone. The first event in the sequence has been given for you. Calcium ions enter the cytoplasm of the receptor cell Two species of green lacewing, C. carnea and C. downesi, evolved from a common ancestor. The two species have populations with overlapping distributions in parts of North America. Table 9.1 shows a comparison of the characteristics of overlapping populations of the two species. Table 9.1 characteristic C. carnea C. downesi breeding months June to September April to May courtship song song with a regular rhythm song with no regular rhythm colour light green dark green Suggest how speciation occurred to produce the two different species of green lacewing.
9700_w23_qp_43
THEORY
2023
Paper 4, Variant 3
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outlines how a cholinergic synapse works. A A A B ACh wave of depolarisation A C B B acetylcholinesterase With reference to : name A and B A B name the process occurring at C state the effect of B entering the post-synaptic neurone explain the role of acetylcholinesterase in the synapse. Some synapses in the brain use the neurotransmitter dopamine. After the postsynaptic membrane has been depolarised, dopamine leaves the receptor proteins and moves back into the presynaptic neurone through specific transporter proteins. Schizophrenia is a condition in which there is a higher than usual concentration of dopamine in certain areas of the brain. The drug phenothiazine has a similar shape to dopamine and is used to treat schizophrenia. Suggest and explain what occurs at the synapse when phenothiazine is used in the treatment of schizophrenia. DRD4 is a dopamine receptor in humans. The gene coding for the DRD4 receptor has a large number of alleles, of which an individual can have only two. Three alleles of the DRD4 receptor gene have the following mutations: • a single base substitution • a 21 base-pair deletion • a 13 base-pair deletion. The 13 base-pair deletion has the most serious consequences for the structure of the DRD4 receptor protein. Suggest why this is so. One allele of the DRD4 gene has been found more frequently amongst individuals whose personality is described as ‘impulsive and exploratory’. Describe the mechanism whereby an allele such as this could have become common in the human population.
9700_s13_qp_41
THEORY
2013
Paper 4, Variant 1
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outlines how a cholinergic synapse works. A A A B ACh wave of depolarisation A C B B acetylcholinesterase With reference to : name A and B A B name the process occurring at C state the effect of B entering the post-synaptic neurone explain the role of acetylcholinesterase in the synapse. Some synapses in the brain use the neurotransmitter dopamine. After the postsynaptic membrane has been depolarised, dopamine leaves the receptor proteins and moves back into the presynaptic neurone through specific transporter proteins. Schizophrenia is a condition in which there is a higher than usual concentration of dopamine in certain areas of the brain. The drug phenothiazine has a similar shape to dopamine and is used to treat schizophrenia. Suggest and explain what occurs at the synapse when phenothiazine is used in the treatment of schizophrenia. DRD4 is a dopamine receptor in humans. The gene coding for the DRD4 receptor has a large number of alleles, of which an individual can have only two. Three alleles of the DRD4 receptor gene have the following mutations: • a single base substitution • a 21 base-pair deletion • a 13 base-pair deletion. The 13 base-pair deletion has the most serious consequences for the structure of the DRD4 receptor protein. Suggest why this is so. One allele of the DRD4 gene has been found more frequently amongst individuals whose personality is described as ‘impulsive and exploratory’. Describe the mechanism whereby an allele such as this could have become common in the human population.
9700_s13_qp_43
THEORY
2013
Paper 4, Variant 3
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shows a type of neurone found in the brain, called a pyramidal cell. cell body many dendrites single axon On , draw one arrow to indicate the direction in which a nerve impulse will travel, as it leaves the cell body of the pyramidal cell. shows the percentage of energy used for various processes involved in the maintenance of resting potentials and in the reception and transmission of action potentials by a pyramidal cell. 34% 47% 3% maintaining resting potentials recycling transmitter back into presynaptic vesicles setting up gradient for presynaptic Ca2+ restoring Na+ gradient at post-synaptic membrane transmitting action potentials 3% 13% Explain why maintaining a resting potential requires energy. Outline the role of calcium ions in passing on an impulse from the pyramidal cell to another neurone. Pyramidal cells contain large numbers of mitochondria. There are more mitochondria in each dendrite than in the axon. With reference to , suggest reasons for this distribution of mitochondria.
9700_s15_qp_42
THEORY
2015
Paper 4, Variant 2
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is an electron micrograph of part of a cholinergic synapse. $ On , use label lines and letters to label each of the following: X – a structure that indicates that A is a pre-synaptic neurone Y – an area that contains many voltage-gated Na+ channels Z – an area that contains both acetylcholine and acetylcholinesterase. Some insecticides have a similar structure to acetylcholine. Suggest how these insecticides may affect the functioning of acetylcholinesterase. Outline the roles of synapses in the nervous system.
9700_s16_qp_42
THEORY
2016
Paper 4, Variant 2
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Describe how an action potential arriving at a presynaptic neurone can result in the release of acetylcholine into the synaptic cleft. Lidocaine is a local anaesthetic drug which blocks voltage-gated Na+ channels in the postsynaptic membrane of a synapse. Explain the effect of lidocaine action on the postsynaptic neurone. is a diagram of a neuromuscular junction. A B C With reference to , name structures A, B and C. A B C Outline the importance of structure A in the transmission of nerve impulses. Explain why the structures labelled C are needed in a neuromuscular junction.
9700_s18_qp_42
THEORY
2018
Paper 4, Variant 2
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Questions Discovered
98