China
Africa
Explore chapters and articles related to this topic
The Central Nervous System Organization of Behavior
Published in Rolland S. Parker, Concussive Brain Trauma, 2016
Spinal segments (neuromeres) preserve the primitive arrangement. They have an arrangement of sensory and motor columns similar to the brainstem, where there are motor and sensory roots represented by cranial nerve nuclei. The neuromeres are reflected in somatic segments (metameres), and are subdivided as myotomes, scleratomes, and dermatomes (Parent, 1996, pp. 264–268, 325).
The Skin and Muscles of the Back
Published in Gene L. Colborn, David B. Lause, Musculoskeletal Anatomy, 2009
Gene L. Colborn, David B. Lause
Thirty-one pairs of spinal nerves arise segmentally from the spinal cord - including eight cervical, twelve thoracic, five lumbar, five sacral and one coccygeal pair. Each pair of spinal nerves arises from a segment or neuromere of the spinal cord by a number of rootlets. The first cervical spinal nerve emerges from the spinal canal between the atlas (the first vertebra) and the base of the skull. The other spinal nerves are formed at the intervertebral foramen present between each two adjacent vertebrae.
System level analysis of motor-related neural activities in larval Drosophila
Published in Journal of Neurogenetics, 2019
Youngteak Yoon, Jeonghyuk Park, Atsushi Taniguchi, Hiroshi Kohsaka, Ken Nakae, Shigenori Nonaka, Shin Ishii, Akinao Nose
Having determined the motor state in each time frame, we next searched for and found neurons whose activity is biased toward forward or backward fictive locomotion. Both FW-biased and BW-biased neurons were found to exist throughout the anterior–posterior axis of the VNC, which suggests that the circuits regulating forward and backward locomotion are scattered in the VNC. This is consistent with the previous ablation experiments, which suggested that any segment from A2/3 to A8/9 is able to initiate both forward and backward waves (Pulver et al., 2015). Identified biased neurons included a cluster of neurons near the midline at the boundary between the SEZ and thoracic segments, which are among the earliest to be activated during BW. The location of these cells overlaps with the region that contains downstream circuits of Wave neurons in the A1 neuromere (Takagi et al., 2017). Wave neurons are segmentally repeated interneurons present in abdominal segments that differ in function depending on their location along the anterior–posterior axis: anterior Wave neurons elicit backward locomotion in response to touch stimuli in the head whereas posterior Wave neurons elicit forward locomotion in response to touch stimuli in the tail. While Wave neurons are activated by the sensory stimuli but not during spontaneously occurring fictive backward locomotion, the downstream neurons are likely to involve those that are specifically active during backward locomotion and actuate the motor program. The BW-biased neurons identified in this study may include such neurons.
Axon length maintenance and synapse integrity are regulated by c-AMP-dependent protein kinase A (PKA) during larval growth of the drosophila sensory neurons
Published in Journal of Neurogenetics, 2019
Tijana Copf, Mildred Kamara, Tadmiri Venkatesh
The phenotype caused by the elevated PKA levels is more prominent in the posterior neuromeres where the axons of class IV neurons originating from A4 to A8 body segments target. The posterior neurons form the longest axons, as they must cover the longest distance during the fast larval body growth. Final length of the axon by the end of third instar stage depends on the position of its soma on the larval body wall. An axon coming from the most posterior abdominal segment (A8) is on average 4–5 times longer than the axon coming from the first abdominal segment (A1). The approximate length of the axon of class IV neuron positioned on the first abdominal segment (A1) is 0.6 mm, while the length of the axon of class IV neuron positioned on an A8 segment extends up to 2.6 mm in length. During the transition from the first to the second, and finally third larval stage the larval body extends at much a faster rate than does the VNC. A first instar larva has a body approximately 2–2.5 mm long, while a third instar larva has body approximately 7–8 mm long. Thus, the body will grow by approximately 3- to 4-fold between these two stages. On the other side, the length of the VNC does not change at the same rate. VNC grows by only around 1.7-fold between these two larval stages. In particular, the length that spans the eight abdominal neuromeres (A1–A8) in a first instar larva is approximately 130 μm, while this length in a third instar larva becomes approximately 230 μm. This means that the neurons projecting to the anterior abdominal neuromeres (A1–A3) need to extend much less than the axons projecting to the posterior neuromeres (A4–A8). While a class IV da neuron projecting to A1 needs to grow an axon that is several hundred micrometers long, a class IV neuron projecting to A8 will have to extend its axon over several millimeters of length. PKA appears to affect a cellular process that is required during this fast time of axonal elongation.