the tendon tap reflex can be elicited by a stretch in a muscle. what is the order of information flow from the primary sensory afferent to the lower motor neuron?

get the tendon tap reflex can be elicited by a stretch in a muscle. what is the order of information flow from the primary sensory afferent to the lower motor neuron? from EN Bilgi.

Golgi Tendon Organ

Golgi Tendon Organ

Golgi tendon organs (GTOs) are proprioceptors that are located in the tendon adjacent to the myotendinous junction.

From: Fundamentals of Hand Therapy, 2007

Related terms:

Motor NeuronMechanoreceptorEicosanoid ReceptorAlpha Motor NeuronStretch ReflexProprioceptionMuscle SpindleSkeletal MuscleInterneuronReflex

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Extraocular Muscles: Proprioception and Proprioceptors

R. Blumer, in Encyclopedia of the Eye, 2010

Occurrence, Distribution, and Number of Golgi Tendon Organs

Golgi tendon organs are exclusively found in the EOMs of even-toed ungulates (pig, sheep, camel, and cow). They have not been found in other mammals and man. In even-toed ungulates, Golgi tendon organs are distributed throughout the proximal and distal EOM tendons, their number always being higher in the distal tendons (Table 1). The number of Golgi tendon organs per muscle has been counted to be 46–128 and 30–90 in pig and camel, respectively. In both species, Golgi tendon organs are more frequent in the rectus EOMs than in the oblique EOMs.

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Somatosensation

James M. Goodman, Sliman J. Bensmaia, in The Senses: A Comprehensive Reference (Second Edition), 2020

4.02.4.2.2 Golgi tendon Organs (GTOs)

Golgi tendon organs (GTOs) are spindle-shaped end organs that, as mentioned above, are similar to Ruffini endings in structure and function (Nitatori, 1988; Zelená and Soukup, 1983). GTOs are situated at the transition between muscle fibers and their respective tendons and run in series, rather than in parallel, with their associated muscles. A GTO comprises a capsule that contains tendons spanning roughly 10 muscle fibers. Each GTO is innervated by a single group 1b afferent, also known as a GTO afferent, which distributes multiple terminal branches throughout the collagenous mesh within the capsule (Fig. 4A). GTO responses are likely evoked when this mesh experiences strain, thereby constricting the nerve contained therein (Fig. 1E) (Zelená and Soukup, 1983). As is the case with group 1a afferents, group 1b afferents are large-diameter rapidly-conducting Aα fibers (Hunt and Kuffler, 1951).

Group 1b afferents respond to active tension of the muscles (Fig. 4C) (Houk and Henneman, 1967; Jansen and Rudjord, 1964) and signal the force produced by the muscles. Group 1 b afferents are remarkably insensitive to passive stretch of the muscles, responding only to extreme levels thereof. Group 1 b afferents respond to increases in active force in discrete “steps” (Appenteng and Prochazka, 1984; Crago et al., 1982; Edin and Vallbo, 1990a), each of which reflects the recruitment of an additional muscle fiber. Unlike muscle spindles, GTOs are not innervated by any efferents. In contrast to spindle fibers, GTO fibers exhibit little baseline spiking activity and respond monotonically (if not linearly) with the recruitment of new motor units (Crago et al., 1982; Gregory and Proske, 1979; Proske and Gregory, 1980), implying a lack of “pacemaker” activity or competitive interference between spike initiation zones.

As muscle spindles' parallel position with respect to muscles explains their sensitivity to muscle stretch, GTOs' position in series with the muscle explains their sensitivity to muscle tension (Matthews, 1933, 2015; Zelená and Soukup, 1983); indeed, tension, but not strain, is constant among viscoelastic elements in series. Moreover, their situation in series with the muscles can explain GTO afferents' peculiar sensitivity to active force generation by the muscles despite the lack of descending input. When the muscle is not actively contracting, muscle stiffness is far lower than that of the tendon stiffness, so muscle tissue, rather than the tendon, experiences most of the strain. When the muscle is actively contracting, muscle tissue approaches stiffness comparable to that of the tendons (Cook and McDonagh, 1996), resulting in appreciable strain being experienced by the tendons and, thereby giving rise to the preferential response of GTO afferents.

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Balance, Gait, and Falls

Colum D. MacKinnon, in Handbook of Clinical Neurology, 2018

Golgi tendon organs

Golgi tendon organs (GTOs) are mechanoreceptors that provide output encoding the level of tensile load applied to the tendon (for review, see Mileusnic and Loeb, 2006). For this reason, GTOs, particularly those in the lower-limb extensors, are critical for sensing the forces exerted to resist imposed loads or the force of gravity acting on the body and regulating extensor activity required for maintaining vertical support and postural stability. These receptors are located in series between the muscle fibers and the collagen strands that compose the tendon. Each GTO is innervated by a single myelinated Ib afferent. Muscle contraction straightens the collagen fibers surrounding the GTO and compresses and depolarizes the sensory ending. Ib axons are fast conducting (72–120 m/s), bifurcate when entering the spinal cord, and send branches rostrally and caudally via the dorsal columns. Branches that enter the gray matter principally terminate in Rexed's laminae V–VII (Fig. 1.3C) and innervate premotor interneurons.

The reflex actions evoked by activation of Ib afferents can be quite complex. The classic GTO Ib reflex (termed autogenic inhibition) is characterized disynaptic inhibition of synergistic motoneurons, via Ib inhibitory interneurons, and di- or trisynaptic excitation of antagonist motoneurons. The ascending and descending branches of the Ib afferent axon allow these effects to be elicited at multiple joints. Unlike intrafusal muscle fibers, GTOs do not receive efferent projections that can modulate the sensitivity of the receptor. Nonetheless, the function of the Ib inhibitory reflex pathway can be dramatically modulated in a context- and task-dependent manner. For example, Ib reflex inhibition is reduced during standing compared with sitting (Faist et al., 2006) and further attenuated during situations of postural threat (e.g., unstable or small support surface) (Horslen et al., 2017).

Source : www.sciencedirect.com

Spinal Reflexes and Descending Motor Pathways (Section 3, Chapter 2) Neuroscience Online: An Electronic Textbook for the Neurosciences

Home Table of Contents Further Reading

Section 3: Motor Systems

Chapter 2: Spinal Reflexes and Descending Motor Pathways

James Knierim, Ph.D., Department of Neuroscience, The Johns Hopkins University

Last Review 20 Oct 2020

2.1 Spinal Reflexes

As noted in the previous chapter, a sense of body position is necessary for adaptive motor control. In order to move a limb toward a particular location, it is imperative to know the initial starting position of the limb, as well as any force applied to the limb. Muscle spindles and Golgi tendon organs provide this type of information. In addition, these receptors are components of certain spinal reflexes that are important for both clinical diagnosis as well as for a basic understanding of the principles of motor control.

Myotatic reflex (stretch reflex)

Figure 2.1

Myotatic reflex. This is also known as the stretch reflex, the knee-jerk reflex, and the deep tendon reflex.

Note: Locations of neurons within spinal cord are not meant to be anatomically accurate.

The myotatic reflex is illustrated in Figure 2.1. A waiter is holding an empty tray, when unexpectedly a pitcher of water is placed on the tray. Because the waiter’s muscles were not prepared to support the increased weight, the tray should fall. However, a spinal reflex is automatically initiated to keep the tray relatively stable. When the heavy pitcher is placed on the tray, the increased weight stretches the biceps muscle, which results in the activation of the muscle spindle’s Ia afferents. The Ia afferents have their cell bodies in the dorsal root ganglia of the spinal cord, send projections into the spinal cord, and make synapses directly on alpha motor neurons that innervate the same (homonymous) muscle. Thus, activation of the Ia afferent causes a monosynaptic activation of the alpha motor neuron that causes the muscle to contract. As a result, the stretch of the muscle is quickly counteracted, and the waiter is able to maintain the tray at the same position.

A major role of the myotatic reflex is the maintenance of posture. If one is standing upright and starts to sway to the left, muscles in the legs and torso are stretched, activating the myotatic reflex to counteract the sway. In this way, the higher levels of the motor system are able to send a simple command (“maintain current posture”) and then be uninvolved in its implementation. The lower levels of the hierarchy implement the command with such mechanisms as the myotatic reflex, freeing the higher levels to perform other tasks such as planning the next sequence of movements.

The myotatic reflex is an important clinical reflex. It is the same circuit that produces the knee-jerk, or stretch, reflex. When the physician taps the patellar tendon with a hammer, this action causes the knee extensor muscle to stretch abruptly. This stretch activates the myotatic reflex, causing an extension of the lower leg. (Because the physician taps the tendon, this reflex is also referred to as the deep tendon reflex. Do not be confused, however, between this terminology and the Golgi tendon organ. The myotatic reflex is initiated by the muscle spindle, not the Golgi tendon organ.) As discussed below, spinal reflexes can be modulated by higher levels of the hierarchy, and thus a hyperactive or hypoactive stretch reflex is an important clinical sign to localize neurological damage.

Reciprocal inhibition in the stretch reflex

Joints are controlled by two opposing sets of muscles, extensors and flexors, which must work in synchrony. Thus, when a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle (Figure 2.2). This inhibition is accomplished by an inhibitory interneuron in the spinal cord. The Ia afferent of the muscle spindle bifurcates in the spinal cord (See Chapter 6 of Section I for review). One branch innervates the alpha motor neuron that causes the homonymous muscle to contract, producing the behavioral reflex. The other branch innervates the Ia inhibitory interneuron, which in turn innervates the alpha motor neuron that synapses onto the opposing muscle. Because the interneuron is inhibitory, it prevents the opposing alpha motor neuron from firing, thereby reducing the contraction of the opposing muscle. Without this reciprocal inhibition, both groups of muscles might contract simultaneously and work against each other.

Figure 2.2

Reciprocal inhibition in stretch reflex. Both extensor and flexor motor neurons are firing to maintain the arm at its location. When the pitcher is placed on the tray, the stretch reflex activates the flexor and inhibits the extensor.

Note: Locations of neurons within spinal cord are not meant to be anatomically accurate.

Autogenic inhibition reflex

The Golgi tendon organ is involved in a spinal reflex known as the autogenic inhibition reflex (Figure 2.3). When tension is applied to a muscle, the Group Ib fibers that innervate the Golgi tendon organ are activated. These afferents have their cell bodies in the dorsal root ganglia, and they project into the spinal cord and synapse onto an interneuron called the Ib inhibitory interneuron. This interneuron makes an inhibitory synapse onto the alpha motor neuron that innervates the same muscle that caused the Ib afferent to fire.

Source : nba.uth.tmc.edu

BMS 300 Exam 2 Flashcards

Start studying BMS 300 Exam 2. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

BMS 300 Exam 2

Camillo Golgi was a

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reticularist

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Santiago Ramon y Cajal was a

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cellularist and the father of the neuron doctrine

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Camillo Golgi was a reticularist

Santiago Ramon y Cajal was a

cellularist and the father of the neuron doctrine

The dentrite is a. input b. conductile c. output a the axon is a. input b. conductile c. output b

The axon terminal is

a. input b. conductile c. output c

Protein synthesis occurs in the

a. cell body b. axon c. dentrite d. terminal a

the input region lacks ___, but contains ____

a. ligand-gated channels, voltage gated channels

b. K+ leak channels, voltage gated channels

c. voltage-gated channels, ligand gated channels

d. ligand-gated channels, K+ leak channels

c

The fast axoplasmic transport includes proteins from the __________ and transported on ___________. The slow axoplasmic transport includes proteins from the ____________.

a. rough ER, microtubules, cytoplasm

b. microtubules, cytoplasm, rough ER

c. cytoplasm, rough ER, microtubules

a

Proteins are transported via axoplasmic transport at slow rates (0.5 to 2 mm per day) and fast rates (200 to 400 mm per day). The difference in transport rate directly results from:

a. the difference in the time spend per day in transport

b. the site where the protein is synthesized

c. the substrate molecule used by the motor protein

d. the motor protein used to transport the proteins

a

In resting condition, ____ is high outside the cell and ___ is high inside the cell.

a. Na+, K+ b. K+, Na+ a

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BIOLOGY

Darwin’s finches have been used to study how differences in bird morphology are related to differences in diet. Morphological measurements (in mm) of three species are given in the table for three traits.

\begin{matrix} \text{Species} & \text{Wing length } & \text{Tarsus length} & \text{Beak length}\\ \text{G. difficilis} & \text{64} & \text{18.1} & \text{9.6}\\ \text{G. fuliginosa} & \text{62.1} & \text{17.9} & \text{8.6}\\ \text{G. scandens} & \text{73.1} & \text{21.1} & \text{14.5}\\ \end{matrix}

Species G. difficilis G. fuliginosa G. scandens ​ Wing length 64 62.1 73.1 ​ Tarsus length 18.1 17.9 21.1 ​ Beak length 9.6 8.6 14.5 ​

The proportion of time spent feeding on different types of food for these three species is given in the following table.

\begin{matrix} \text{Species} & \text{Seeds} & \text{Pollen} & \text{Other}\\ \text{G. difficilis} & \text{0.67} & \text{0.23} & \text{0.1}\\ \text{G. fuliginosa} & \text{0.7} & \text{0.28} & \text{0.02}\\ \text{G. scandens} & \text{0.14} & \text{0} & \text{0.86}\\ \end{matrix}

Species G. difficilis G. fuliginosa G. scandens ​ Seeds 0.67 0.7 0.14 ​ Pollen 0.23 0.28 0 ​ Other 0.1 0.02 0.86 ​

Thinking of the morphology of each species as a point in

\mathbb{R}^{3}, R 3

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Verified answer BIOLOGY

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