Concept explainers
FOCUS ON EVOLUTION
An action potential is an all-or-none event. This on/off signaling is an evolutionary adaptation of animals that must sense and act in a complex environment. It is possible to imagine a nervous system in which the action potentials are graded, with the amplitude depending on the size of the stimulus. Describe what evolutionary advantage on/off signaling might have over a graded (continuously variable) kind of signaling.
Want to see the full answer?
Check out a sample textbook solutionChapter 37 Solutions
Campbell Biology in Focus; Modified Mastering Biology with Pearson eText -- ValuePack Access Card -- for Campbell Biology in Focus (2nd Edition)
Additional Science Textbook Solutions
Human Anatomy & Physiology (11th Edition)
SEELEY'S ANATOMY+PHYSIOLOGY
MARINE BIOLOGY
Anatomy & Physiology: The Unity of Form and Function
Biology: Life on Earth (11th Edition)
- You learned in this chapter that Na+/K+ active transport pumps in the plasma membrane of the axons are responsible for creating the imbalance between Na+ and K+ inside and outside of the neuron that produces the resting membrane potential. In early research studying the role of ions and the involvement of active transport of ions in neural signaling, investigators used the giant axon of a squid as a model. The diameter of a giant axon is far greater than that of a mammalian axon, which enabled researchers to isolate it easily and use it in in vitro experiments. In one early experiment, researchers investigated the active transport of Na+ out of the axon in response to the presence of cyanide. Experimentally they hooked up a section of axon to a syringe, immersed the axon in artificial seawater, introduced radioactive 22Na (as 22NaCl) into the axon, and then quantified the transport of 22Na out through the axons plasma membrane. The rate of 22Na transport out of the axon was determined by measuring the radioactivity released into the fluid sur- rounding the axon over a period of time. The Figure shows the results of the experiment. What is the effect of cyanide on Na1 transport out of the squid axon? How do the data show the effect? Source: P. C. Caldwell et al. 1960. The effects of injecting energy-rich phosphate compounds on the active transport of ions in the giant axons of Loligo. The Journal of Physiology 152:561590. Cengage Learning 2017arrow_forwardNeed help Different behavior patterns can be created by interactions of one or more pattern generators - in response to light touch, the sea slug, Tritonia, exhibits reflexive withdrawal of the body away from the stimulus (i.e. the sea slug “cringes”). However, a stronger mechanical stimulus induces the release of serotonin from specific neurons within the central nervous system and subsequent swimming behavior (i.e., an escape response). Both withdrawals of the body and swimming are driven by the same central pattern generator circuitry. This illustrates which important characteristic of central pattern generators? A. Model central pattern generators are not as complex as their real-world counterparts. B. Their rhythmic output is an emergent property of the neural network. C. Their output is not fixed but can be modifiedarrow_forwardPut the steps of the process of G-protein signal transduction in the order (1-4) in which they occur. Second messenger molecules are activated and amplify the signal A signal molecule binds to a receptor on the outside of the cell The alpha (a) subunit of the G-protein inside the cell moves and binds to a nearby enzyme The receptor changes shape, transducing the signal into the cellarrow_forward
- a scientist that works on autism and you think that the mutation in the sodium channel found in 3 of your patients can be one of the causes for this disorder. Describe an experiment you could do to test this hypothesis. the scientist need to be specific from the beginning of of the experiment by identifying the mutation to the end including experiment, propagation of action potential, its effect on signal transmission and synapse and give an example of the phenotype you anticipate to observearrow_forwardYou recently read about Justin Bieber's unfortunate run-ins with glass doors and walls. Since then, you learned about how neurons are the unique cell of the nervous system and that signals are sent via action potential along those cells. You have further learned about how signals "jump" from one neuron to the next, allowing for your nervous system to function every single day. Explain, using language from your learning of signal transduction and the nervous system, just what Justin Bieber's neurons should have been doing to prevent his unfortunate accidents. In other words, describe how are signals received, sent, and passed along in the nervous system (a system primarily responsible for preventing people from walking into doors and walls). You may enhance your answer by comparing the effects of drug use with the inability to avoid these accidents. *Hint: half of your response should be about neuron anatomy and action potential and the other half should be about signaling across…arrow_forwardThe figure below shows a signaling pathway activated by the bindiıng of adrehalMNe LU the beta-adrenergic receptor. Binding of adrenaline to the receptor causes GTP-binding and activation of G proteins. Active GTP-bound G protein activates adenylate cyclase to initiate a signaling cascade that affects cellular responses, and includes cellular changes to mediate increased heart rate and accounts for the flight-or-fight response. activated adenylate cyclase adrenaline activated B-adrenergic receptor adenylate cyclase G protein subunit 22 GTP SDP conformational ATP CAMP change in receptor heterotrimeric G protein ACAMP inactive protein kinase A active protein kinase A 4 cellular responses Consider the homozygous mutation in which a cell produces a variant of adenylate cyclase that can no longer be activated Which of the following are true in this cell? Select all that apply. Heart rate increases Protein Kinase A is not activated CAMP levels are lower than normal Heart rate decreasesarrow_forward
- You can choose one or more than one option The dissociation constant (Kd) of a receptor is: BIOCHEMISTRY basic the concentration of a ligand that produces 100% occupancy of the receptor the concentration of a ligand that produces 50% of the maximal effect. the measurement of specificity between ligand and its receptor. the measurement of speed by which a ligand will dissociate from its receptor. the measurement of affinity between a ligand and its receptor and the inverse of the association constant. During an experiment with Drosophila, it was discovered that all females had red eyes. unlike males. A conclusion based on this observation would be: MOLECULAR BIOLOGY basic The gene for eye color is located on the X chromosome. The females are homozygotes The gene for eye color is dominant. The eye color results from multigenic linkage. The eye color phenotype is sex-linked A secondary lysosome: CELL BIOLOGY advanced a lysosome that provides a backup to the primary…arrow_forwardThe giant squid axon has a diameter = 1mm and 1 = 13mm. Compared to a mammalian neuron with a diameter = 1 um and ^ = 0.2mm, which of the following is correct? graded potentials can generate action potentials in the mammalian axon but not in the squid axon. graded potential of similar magnitude would result in action potentials with larger amplitude in the mammalian axon graded potentials of similar magnitude would result in action potentials with larger amplitude in the squid axon graded potentials of similar magnitude would travel furthest from their point of origin in the mammalian axon graded potentials of similar magnitude would travel furthest from their point of origin in the squid axonarrow_forwardDescribe the 5 basic steps of electrical and chemical neural signaling. A strong action will explain each step. Also, describe at least one way synaptic connections can change as a result of experience or learning.arrow_forward
- Except for?, all of the following signals may trigger receptor conformational changes without reaching the plasma membrane. o a. Receptors for steroid hormones. Tyrosine kinase receptors are a kind of receptor that binds to tyrosine phosphatase. Voltage-gated ion channels (OC). G protein-coupled receptors (GPCRs).arrow_forwardIn most neurons, membrane depolarization leads to the opening of voltage-dependent ion channels, generation of an action potential, and, ultimately, an influx of Ca2+, which causes release of neurotransmitter at the axon terminus. Devise a cellular strategy by which hyperpolarization in rod cells could produce excitation of the visual pathway and passage of visual signals to the brain. (Hint: The neuronal signaling pathway in higher organisms consists of a series of neurons that relay information to the brain. The signal released by one neuron can be either excitatory or inhibitory to the following, postsynaptic neuron.)arrow_forwardWhich membrane proteins are involved in the potentiation of the membrane signalling that travels along a nerve cell? Na* channels Nat/K* pumps K* carriers Ca2+ channelsarrow_forward
- Anatomy & PhysiologyBiologyISBN:9781938168130Author:Kelly A. Young, James A. Wise, Peter DeSaix, Dean H. Kruse, Brandon Poe, Eddie Johnson, Jody E. Johnson, Oksana Korol, J. Gordon Betts, Mark WomblePublisher:OpenStax CollegeBiology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning