Concept explainers
Table 7.3 (chapter 7) provides the axon diameters and conduction velocities required to answer the following questions.
Suppose, in a knee-jerk reflex, the sensory axon and motor axon extending between the muscle and spinal cord are each 16 inches long. The sensory axon has a diameter of
1 m/sec is equal to 2.24 miles per hour, answer the following questions.
Suppose the time from the start of action potentials in the sensory neuron and the end of action potentials in the motor neuron was measured to be 15 milliseconds. How much time was required for synaptic transmission?
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CONNECT W/APR & PHILS FOR FOX HUMAN PHYS
- The Baroreceptor reflex illustrates very well the principles and elements of a negative feedback loop.1) What is the typical circumstance in which the baroreceptor reflex is stimulated? What is the stimulus for the reflex and the response?2a) Using the terms for a homeostatic negative feedback loop or a reflex, describe both the function AND anatomical elements serving that function for each of the following as it applies to the baroreceptor reflex known as: an effector. 2b) applied to the baroreceptor reflex known as: the integration center?arrow_forwardStudy the diagram of a synapse between a sensory neuron and a motor neuron in a simple reflex arc involving only two neurons. Use the information provided by the diagram to answer the questions. 60 mV 2- +40 mv 3. d. -60 mV + 40 mV f 1. If the neurotransmitter substance was acetylcholine, describe two places where this synapse might be found in the body. Answer: From the diagram, identify where receptors for the neurotransmitter would be located. Explain your answer. 2. Answer: 3. Which letter indicates the axon of the sensory neuron? Justify your answer. Answer: 4. Identify where an action potential is occurring. Justify your answer. Answer: What structure is represented by the letter F? What is the function of F? What effect does F have on the transmission of action potentials along the neuron? 5.arrow_forwardWhy does the autonomic motor nervous system use twoneurons (preganglionic and ganglionic) in a chain to aneffector? (For the answer, read section 18.1a.)arrow_forward
- Which of the following statements regarding the motor end plate in the somatic motor division of the nervous system is true? After the activation of voltage-gated calcium channels, the neuron releases ACh onto the muscarinic receptors on the surface of the highly folded area of the muscle fibre. The preganglionic nerve fibre releases ACh onto the postganglionic nerve fibre, which then releases ACh onto the cholinergic receptors of the motor end plate. Chemically gated monovalent cation channels on the motor end plate are activated once the motor neuron releases ACh onto the nicotinic receptors on the surface of the muscle cell. The AChE enzyme enhances the amount of ACh released into the neuromuscular junctionarrow_forwardSensory fibers, or pathways, are referred to as “afferent.” Motor fibers, or pathways, are referred to as “efferent.” What can you infer about the meaning of these two terms (afferent and efferent) in a structural or anatomical context?arrow_forwardConsider three alpha-motor neurons of different sizes: small, medium and large. All three neurons receive input from the same excitatory interneuron. When the interneuron fires action potentials at low frequency, only one alpha motor neuron fires action potentials. As the action potential frequency of the interneuron increases, two alpha-motor neurons are recruited, and at maximum frequency, all three are recruited. In what order would the three alpha-motor neurons have been recruited? Large first, then medium, then small. Small first, then medium, then large. Medium first, then small, then large. Medium first, then large, then small.arrow_forward
- When the neurotransmitter acetylcholine (ACh) binds the acetylcholine receptor (a GPCR) on muscle cells, it causes them to contract. ZIGGY, a chemical analog of ACh, also binds to the same acetylcholine receptor on muscle cells, but instead causes the muscle cells to relax. For this reason, it is sometimes prescribed as a muscle relaxer. Explain in 3-4 sentences how ZIGGY could cause muscle relaxation. How can both ZIGGY and ACh bind the same GPCR? And then how can they have different effects on the cells, despite binding to the same receptor on the same cells?arrow_forwardIn the discussion section the authors wrote “In this study, we observed that different paradigms of tES application could ameliorate motor function impairments in ICH induced by collagenase administration into the striatum of rats.” a. Is the information in this quote about afferent of efferent? b.By what word or words do you know that your answer to the question is correct? c. Why did you choose this word or words as an answer to the question?arrow_forwardIn a combination of excitatory or inhibitory synaptic connections the following is true it is poorly exemplified by the stretch reflex during a knee jerk in the stretch reflex circuit the biceps or flexor muscle gets activated in the stretch reflex circuit the quadriceps or extensor muscle gets activated an inhibitory interneuron inhibits the flexor motor neuron an inhibitory interneuron inhibits the extensor motor neuron motor neuronarrow_forward
- A chemical synapse is a type of synapse that occurs between two neurons and between a motor neuron and skeletal muscle fibers (i.e. at a Neuromuscular junction, NMJ). Compare and contrast the specific events that occur at chemical synapses at these two sites. Describe clearly how they are similar and how they are different, starting at the arrival of a nerve impulse at the pre-synaptic neuron and ending up with the changes observed at the postsynaptic membranes.arrow_forwardA laboratory experiment is set up where you have two fully functional nerves properly aligned so that it potentially can transmit an action potential through a synapse to the second nerve. The buffer outside the cells contain Na+, H+ and Cl- as the only inorganic ions. When you stimulate the nerve, surprisingly the second nerve does not respond. What is the most likely explanation for the failure of the second nerve response? State why you chose your answer. a. The lack of K+ in the buffer prevents propagation of the action potential b. Neurotransmitter is not being released into the synaptic space. c. An action potential can only be initiated by opening a ligand-gated channel. d. Although neurotransmitter is released, it is unable to stimulate opening of the second nerve' ligand-gated channel. e. Repolarization of the axon does not occur in this buffer.arrow_forwardOne treatment for myasthenia gravis is a medication that blocks the activity of acetylcholinesterase. Suggest why this might be a successful treatment.arrow_forward
- Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage LearningHuman Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning