The History of Reflexes Part 2
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Speed and Segmentation Control Mechanisms Characterized in Rhythmically- Active Circuits Created from Spinal Neurons Produced Fr
RESEARCH ARTICLE Speed and segmentation control mechanisms characterized in rhythmically- active circuits created from spinal neurons produced from genetically-tagged embryonic stem cells Matthew J Sternfeld1,2, Christopher A Hinckley1, Niall J Moore1, Matthew T Pankratz1, Kathryn L Hilde1,3, Shawn P Driscoll1, Marito Hayashi1,2, Neal D Amin1,3,4, Dario Bonanomi1†, Wesley D Gifford1,4,5, Kamal Sharma6, Martyn Goulding7, Samuel L Pfaff1* 1Gene Expression Laboratory, Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, United States; 2Biological Sciences Graduate Program, University of California, San Diego, La Jolla, United States; 3Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, United States; 4Medical Scientist Training Program, University of California, San Diego, La Jolla, United States; 5Neurosciences Graduate Program, University of California, San Diego, La Jolla, United States; 6Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, United States; 7Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, United States *For correspondence: pfaff@salk. edu Abstract Flexible neural networks, such as the interconnected spinal neurons that control Present address: †Division of distinct motor actions, can switch their activity to produce different behaviors. Both excitatory (E) Neuroscience, San Raffaele and inhibitory (I) spinal neurons are necessary for motor behavior, but the influence of recruiting Scientific Institute, Milan, Italy different ratios of E-to-I cells remains unclear. We constructed synthetic microphysical neural networks, called circuitoids, using precise combinations of spinal neuron subtypes derived from Competing interests: The mouse stem cells. Circuitoids of purified excitatory interneurons were sufficient to generate authors declare that no oscillatory bursts with properties similar to in vivo central pattern generators. -
What's the Connection?
WHAT’S THE CONNECTION? Sharon Winter Lake Washington High School Directions for Teachers 12033 NE 80th Street Kirkland, WA 98033 SYNOPSIS Students elicit and observe reflex responses and distinguish between types STUDENT PRIOR KNOWL- of reflexes. They then design and conduct experiments to learn more about EDGE reflexes and their control by the nervous system. Before participating in this LEVEL activity students should be able to: Exploration, Concept/Term Introduction Phases ■ Describe the parts of a Application Phase neuron and explain their functions. ■ Distinguish between sensory and motor neurons. Getting Ready ■ Describe briefly the See sidebars for additional information regarding preparation of this lab. organization of the nervous system. Directions for Setting Up the Lab General: INTEGRATION Into the Biology Curriculum ■ Make an “X” on the chalkboard for the teacher-led introduction. ■ Health ■ Photocopy the Directions for Students pages. ■ Biology I, II ■ Human Anatomy and Teacher Background Physiology A reflex is an involuntary neural response to a specific sensory stimulus ■ AP Biology that threatens the survival or homeostatic state of an organism. Reflexes Across the Curriculum exist in the most primitive of species, usually with a protective function for ■ Mathematics animals when they encounter external and internal stimuli. A primitive ■ Physics ■ example of this protective reflex is the gill withdrawal reflex of the sea slug Psychology Aplysia. In humans and other vertebrates, protective reflexes have been OBJECTIVES maintained and expanded in number. Examples are the gag reflex that At the end of this activity, occurs when objects touch the sides students will be able to: or the back of the throat, and the carotid sinus reflex that restores blood ■ Identify common reflexes pressure to normal when baroreceptors detect an increase in blood pressure. -
Deconstructing Spinal Interneurons, One Cell Type at a Time Mariano Ignacio Gabitto
Deconstructing spinal interneurons, one cell type at a time Mariano Ignacio Gabitto Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy under the Executive Committee of the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2016 © 2016 Mariano Ignacio Gabitto All rights reserved ABSTRACT Deconstructing spinal interneurons, one cell type at a time Mariano Ignacio Gabitto Abstract Documenting the extent of cellular diversity is a critical step in defining the functional organization of the nervous system. In this context, we sought to develop statistical methods capable of revealing underlying cellular diversity given incomplete data sampling - a common problem in biological systems, where complete descriptions of cellular characteristics are rarely available. We devised a sparse Bayesian framework that infers cell type diversity from partial or incomplete transcription factor expression data. This framework appropriately handles estimation uncertainty, can incorporate multiple cellular characteristics, and can be used to optimize experimental design. We applied this framework to characterize a cardinal inhibitory population in the spinal cord. Animals generate movement by engaging spinal circuits that direct precise sequences of muscle contraction, but the identity and organizational logic of local interneurons that lie at the core of these circuits remain unresolved. By using our Sparse Bayesian approach, we showed that V1 interneurons, a major inhibitory population that controls motor output, fractionate into diverse subsets on the basis of the expression of nineteen transcription factors. Transcriptionally defined subsets exhibit highly structured spatial distributions with mediolateral and dorsoventral positional biases. These distinctions in settling position are largely predictive of patterns of input from sensory and motor neurons, arguing that settling position is a determinant of inhibitory microcircuit organization. -
Delineating the Diversity of Spinal Interneurons in Locomotor Circuits
The Journal of Neuroscience, November 8, 2017 • 37(45):10835–10841 • 10835 Mini-Symposium Delineating the Diversity of Spinal Interneurons in Locomotor Circuits Simon Gosgnach,1 Jay B. Bikoff,2 XKimberly J. Dougherty,3 Abdeljabbar El Manira,4 XGuillermo M. Lanuza,5 and Ying Zhang6 1Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada, 2Department of Neuroscience, Columbia University, New York, New York 10032, 3Department of Neurobiology and Anatomy, Drexel University, Philadelphia, Pennsylvania 19129, 4Department of Neuroscience, Karolinska Institutet, Stockholm SE-171 77, Sweden, 5Department of Developmental Neurobiology, Fundacion Instituto Leloir, Buenos Aires C1405BWE, Argentina, and 6Department of Medical Neuroscience, Dalhousie University. Halifax, Nova Scotia B3H 4R2, Canada Locomotion is common to all animals and is essential for survival. Neural circuits located in the spinal cord have been shown to be necessary and sufficient for the generation and control of the basic locomotor rhythm by activating muscles on either side of the body in a specific sequence. Activity in these neural circuits determines the speed, gait pattern, and direction of movement, so the specific locomotor pattern generated relies on the diversity of the neurons within spinal locomotor circuits. Here, we review findings demon- strating that developmental genetics can be used to identify populations of neurons that comprise these circuits and focus on recent work indicating that many of these populations can be further subdivided -
Regulation of Spinal Interneuron Development by the Olig-Related Protein Bhlhb5 and Notch Signaling Kaia Skaggs1,2, Donna M
RESEARCH ARTICLE 3199 Development 138, 3199-3211 (2011) doi:10.1242/dev.057281 © 2011. Published by The Company of Biologists Ltd Regulation of spinal interneuron development by the Olig-related protein Bhlhb5 and Notch signaling Kaia Skaggs1,2, Donna M. Martin2,3 and Bennett G. Novitch1,2,4,* SUMMARY The neural circuits that control motor activities depend on the spatially and temporally ordered generation of distinct classes of spinal interneurons. Despite the importance of these interneurons, the mechanisms underlying their genesis are poorly understood. Here, we demonstrate that the Olig-related transcription factor Bhlhb5 (recently renamed Bhlhe22) plays two central roles in this process. Our findings suggest that Bhlhb5 repressor activity acts downstream of retinoid signaling and homeodomain proteins to promote the formation of dI6, V1 and V2 interneuron progenitors and their differentiated progeny. In addition, Bhlhb5 is required to organize the spatially restricted expression of the Notch ligands and Fringe proteins that both elicit the formation of the interneuron populations that arise adjacent to Bhlhb5+ cells and influence the global pattern of neuronal differentiation. Through these actions, Bhlhb5 helps transform the spatial information established by morphogen signaling into local cell-cell interactions associated with Notch signaling that control the progression of neurogenesis and extend neuronal diversity within the developing spinal cord. KEY WORDS: Neurogenesis, Interneurons, Neuronal fate, Notch signaling, Spinal cord, Transcription factors, Mouse, Chick INTRODUCTION V0-V3 interneurons and MNs (Briscoe and Ericson, 2001; Briscoe The control of vertebrate motor behaviors depends on spinal and Novitch, 2008). In the case of MN formation, the patterning interneuron circuits that relay sensory information from the actions of Shh and RA culminate in the expression of the bHLH periphery and modulate motor neuron (MN) activities. -
Interneuron Diversity and Function in the Spinal Motor System
Available online at www.sciencedirect.com ScienceDirect Interneuron diversity and function in the spinal motor system Jay B Bikoff Neural circuits in the spinal cord are the ultimate arbiters of generating patterned motor output, while integrating movement, serving as the conduit through which the rest of the sensory input and supraspinal information arriving nervous system controls muscle contraction to implement directly or indirectly from cortical, basal ganglia, brain- behavior. Over the last two decades, the genetic identity of stem, and cerebellar systems to enable animals to move in neurons in the spinal cord has come into view, revealing the a manner that meets their behavioral needs [4–6]. Reveal- richness of cellular diversity that underlies motor control. ing the identity, organization, and function of spinal Despite this progress, our understanding of how discrete types interneurons is, therefore, essential to understanding of spinal interneurons contribute to motor output remains the neural control of movement. tenuous. Here, I review the landscape of interneuron diversity in the spinal motor system, and highlight key challenges and Early studies of spinal interneuron organization largely novel approaches to linking the molecular and genetic focused on locomotion, one of the most fundamental taxonomy of spinal interneurons to functional aspects of motor functions in an animal’s behavioral repertoire. Over movement. a century ago, Thomas Graham Brown showed that neurons intrinsic to the spinal cord can generate rhythmic Address patterns of locomotor activity, establishing the concept of Department of Developmental Neurobiology, St. Jude Children’s central pattern generators and setting the stage for dec- Research Hospital, Memphis, TN, 38105, USA ades of work dissecting the components of these networks Corresponding author: Bikoff, Jay B ([email protected]) [7]. -
Activity of Spinal Interneurons and Their Effects on Forearm Muscles During Voluntary Wrist Movements in the Monkey
Activity of Spinal Interneurons and Their Effects on Forearm Muscles During Voluntary Wrist Movements in the Monkey STEVE I. PERLMUTTER, MARC A. MAIER, AND EBERHARD E. FETZ Department of Physiology and Biophysics and Regional Primate Research Center, University of Washington, Seattle, Washington 98195 Perlmutter, Steve I., Marc A. Maier, and Eberhard E. Fetz. Dum and Strick 1996; Kuypers 1981; Ralston and Ralston Activity of spinal interneurons and their effects on forearm muscles 1985; Robinson et al. 1987). Spinal interneurons appear during voluntary wrist movements in the monkey. J. Neurophysiol. to integrate convergent supraspinal and peripheral afferent 80: 2475±2494, 1998. We studied the activity of 577 neurons in information and distribute appropriate signals to motoneu- the C6 ±T1 spinal cord of three awake macaque monkeys while they generated visually guided, isometric ¯exion/extension torques rons to activate muscles in coordinated patterns (Baldissera about the wrist. Spike-triggered averaging of electromyographic et al. 1981; Jankowska 1992). activity (EMG) identi®ed the units' correlational linkages with Although mammalian spinal pathways have been exam- °12 forearm muscles. One hundred interneurons produced changes ined extensively since Sherrington's re¯ex studies in the in the level of average postspike EMG with onset latencies consis- early 1900s (Sherrington 1910), virtually all physiological tent with mono- or oligosynaptic connections to motoneurons; investigations have been performed in anesthetized or re- these were classi®ed as premotor interneurons (PreM-INs). Most duced preparations. Of the few descriptions of interneuron PreM-INs (82%) produced postspike facilitations in forearm mus- properties in awake animals, most concern sensory responses cles. Earlier spike-related features, often beginning before the trig- (Bromberg and Fetz 1977; Cleland and Hoffer 1986; Collins ger spike, were seen in spike-triggered averages from 72 neurons. -
The Nervous System Reflexes Spinal Reflexes Reflex Arc the Stretch
1/17/2016 Reflexes • Rapid, involuntary, predictable motor response to a stimulus The Nervous System Spinal Reflexes Spinal Reflexes Reflex Arc • Spinal somatic reflexes • Components of a reflex arc – Integration center is in the spinal cord 1. Receptor—site of stimulus action – Effectors are skeletal muscle 2. Sensory neuron—transmits afferent impulses to the CNS • Testing of somatic reflexes is important clinically 3. Synapses in gray matter—either monosynaptic or to assess the condition of the nervous system polysynaptic region within the CNS 4. Motor neuron—conducts efferent impulses away from cord • Identical stimulus should always elicit the same 5. Effector—muscle fiber or gland cell that responds to response stereotyped reflex the efferent impulses by contracting or secreting Stimulus The Stretch Reflex Skin • Monosynaptic reflex – 2 neurons (sensory and motor), 1 synapse 1 Receptor Interneuron • Muscle spindles 2 Sensory neuron – Sensory receptors in belly of muscle 3 Integration center – Detects changes in length of muscle 4 Motor neuron • Muscle is stretched, reflex reverses the stretch 5 Effector • Important for coordination, maintenance of posture, keeps muscles from over stretching Spinal cord (in cross section) Figure 13.14 1 1/17/2016 Secondary sensory The patellar (knee-jerk) reflex—a specific example of a stretch reflex Efferent (motor) endings (type II fiber – fiber to muscle spindle senses when muscle 2 is still) Quadriceps 3a (extensors) 3b 3b ααα Efferent (motor) 1 Primary sensory fiber to extrafusal Patella endings (type Ia Muscle Spinal cord muscle fibers spindle Fiber – senses (L 2–L4) stretching) Extrafusal muscle 1 Tapping the patellar ligament excites fiber Hamstrings Patellar muscle spindles in the quadriceps. -
The Spinal Interneurons and Properties of Glutamatergic Synapses in a Primitive Vertebrate Cutaneous Flexion Reflex
9068 • The Journal of Neuroscience, October 8, 2003 • 23(27):9068–9077 Behavioral/Systems/Cognitive The Spinal Interneurons and Properties of Glutamatergic Synapses in a Primitive Vertebrate Cutaneous Flexion Reflex Wen-Chang Li, Stephen R. Soffe, and Alan Roberts School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, United Kingdom Unlike the monosynaptic “stretch” reflex, the exact neuronal pathway for a simple cutaneous reflex has not yet been defined in any vertebrate. In young frog tadpoles, we made whole-cell recordings from pairs of spinal neurons. We found direct, excitatory, glutama- tergic synapses from touch-sensitive skin-sensory neurons to sensory pathway interneurons, and then from these sensory interneurons tomotoneuronsandpremotorinterneuronsontheothersideofthebody.Weconcludethattheminimalpathwayforthisprimitivereflex, in which stroking the skin on one side leads to flexion on the other side, is disynaptic. This detailed circuit information has allowed us to ask whether the properties of glutamatergic synapses during the first day of CNS development are tuned to their function in the tadpole’s responses. Stroking the skin excites a few sensory neurons. These activate primarily AMPA receptors producing short, strong excitation that activates many sensory pathway interneurons but only allows temporal summation of closely synchronous inputs. In contrast, the excitation produced in contralateral neurons by the sensory pathway interneurons is weak and primarily mediated by NMDA receptors. As a result, considerable summation is required for this excitation to lead to postsynaptic neuron firing and a contralateral flexion. We conclude that from their early functioning, synapses from sensory neurons are strong and those from sensory pathway interneurons are weak. The distribution of glutamate receptors at synapses in this developing circuit is tuned so that synapses have properties suited to their roles in the whole animal’s reflex responses. -
Degradation of Mouse Locomotor Pattern in the Absence of Proprioceptive Sensory Feedback
Degradation of mouse locomotor pattern in the absence of proprioceptive sensory feedback Turgay Akaya,b,1, Warren G. Tourtellottec, Silvia Arberd,e, and Thomas M. Jessella,b,2 aHoward Hughes Medical Institute and bDepartments of Neuroscience, Biochemistry and Molecular Biophysics, Kavli Institute of Brain Science, Columbia University, New York, NY 10032; cDepartment of Pathology and Neurology, Northwestern University, Chicago, IL 60611; dBiozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; and eFriedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland Contributed by Thomas M. Jessell, October 8, 2014 (sent for review August 24, 2014; reviewed by Ansgar Büschges and John Martin) Mammalian locomotor programs are thought to be directed by the functional locomotor patterns in the absence of proprioceptive actions of spinal interneuron circuits collectively referred to as sensory feedback remains uncertain. “central pattern generators.” The contribution of proprioceptive Prior studies in cat have, nevertheless, provided evidence that sensory feedback to the coordination of locomotor activity proprioceptive feedback modifies stance and swing phase tran- remains less clear. We have analyzed changes in mouse locomotor sitions during walking to accommodate changes in task and ter- pattern under conditions in which proprioceptive feedback is at- rain (14–18), but have not resolved the extent to which tenuated genetically and biomechanically. We find that locomotor proprioceptive sensory feedback contributes to core elements of pattern degrades upon elimination of proprioceptive feedback mammalian locomotor pattern. Nor have the individual con- from muscle spindles and Golgi tendon organs. The degradation tributions of the two main functional classes of proprioceptors— of locomotor pattern is manifest as the loss of interjoint coordina- group Ia/II muscle spindle (MS) and group Ib Golgi tendon organ tion and alternation of flexor and extensor muscles. -
Building a Neuron Model of a Rat Spinal Interneuron
46 C h a p t e r 3 BUILDING A NEURON MODEL OF A RAT SPINAL INTERNEURON The previous chapter showed how simulation could be used to obtain a time se- ries of the extracellular voltage, Ve, in a volume conductor model as a function of time for various electrode combinations. This chapter will discuss a computational model for a rat spinal interneuron. In the next chapters, the extracellular voltage from the volume conductor model will be applied to this neuron model to study the effect of epidural stimulation on neurons in the spinal cord. In particular, I will study if particular patterns of extracellular voltage from the epidural stimulation process can cause or facilitate the release of neurotransmitters from the tip of the axon. The simulations of neuron dynamics used in this thesis are performed using NEU- RON version 7.3 (Michael L. Hines and Nicholas T. Carnevale, 1997). NEURON is a compartmental model neuron simulator. It simulates biological neurons by divid- ing each neuron into groups of compartments, called sections, which have similar membrane properties but may differ in diameter. The compartments in each sec- tion are referred to as segments and each may have a different diameter and 3D position. This thesis will not cover the background behind NEURON or compart- mental modeling in detail. Readers unfamiliar with this material are encouraged to read (Michael L. Hines and Nicholas T. Carnevale, 1997). I will only cover the details necessary to reproduce the results reported in this thesis using the NEURON simulator. Section 3.1 covers the neuron electrical properties which are used in the simula- tions. -
Spinal Reflexes
Spinal Reflexes Lu Chen, Ph.D. MCB, UC Berkeley 1 Simple reflexes such as stretch reflex require coordinated contraction and relaxation of different muscle groups Categories of Muscle Based on Direction of Motion Flexors Æ reduce the angle of joints Extensors Æ increase the angle of joints Categories of Muscle Based on Movement Agonist Æmuscle that serves to move the joint in the same direction as the studied muscle Antagonist Æ muscle that moves the joint in the opposite direction 2 1 Muscle Spindles •Small encapsulated sensory receptors that have a Intrafusal muscle spindle-like shape and are located within the fibers fleshy part of the muscle •In parallel with the muscle fibers capsule •Does not contribute to the overall contractile Sensory force endings •Mechanoreceptors are activated by stretch of the central region Afferent axons •Due to stretch of the whole muscle Efferent axons (including intrafusal f.) •Due to contraction of the polar regions of Gamma motor the intrafusal fibers endings 3 Muscle Spindles Organization 2 kinds of intrafusal muscle fibers •Nuclear bag fibers (2-3) •Dynamic •Static •Nuclear chain fibers (~5) •Static 2 types of sensory fibers •Ia (primary) - central region of all intrafusal fibers •II (secondary) - adjacent to the central region of static nuclear bag fibers and nuclear chain fibers Intrafusal fibers stretched Sensory ending stretched, (loading the spindle) increase firing Muscle fibers lengthens Sensory ending stretched, (stretched) increase firing Spindle unloaded, Muscle fiber shortens decrease firing 4 2 Muscle Spindles Organization Gamma motor neurons innervate the intrafusal muscle fibers. Activation of Shortening of the polar regions gamma neurons of the intrafusal fibers Stretches the noncontractile Increase firing of the center regions sensory endings Therefore, the gamma motor neurons provide a mechanism for adjusting the sensitivity of the muscle spindles.