In an autonomic reflex, the efferent branch typically contains a two-step pathway, where the efferent neuron enters a ganglion (i.e., a bundle of nerve cell bodies) before reaching the effector target. The autonomic reflex and somatic reflex often differ in their efferent branches of the reflex arc and their effector targets. What differentiates an autonomic reflex from a somatic reflex? This cross-extensor reflex is important when the body needs to shift weight to the other side of the body. The reflex can also include a cross- extensor response, whereas if one limb is withdrawn the opposite limb is extended. This reflex protects an individual from harmful situations, such as the fast retrieval of a hand off a hot stove. The withdrawal, or flexor, reflex is an important example of a polysynaptic reflex (reflexes with 2 or more synapses), where an extended body part is quickly flexed, or bent, in response to a harmful stimulus. The Golgi tendon organ is a web of nerve endings that surrounds the tendon fibers and stimulates the reflex during both passive stretching and active muscle contraction. The inverse stretch reflex is the relaxation response to high tension when stretching a muscle. This reflex is a type of deep tendon reflex tested during a neurological examination to identify abnormalities within this reflex arc. The most commonly identified type of stretch reflex is the knee jerk reflex, where tapping the patellar tendon (i.e., the tendon located at the front of the knee) causes the foot to kick forward. The impulses from the muscle spindles are transmitted to the central nervous system, followed by direct transmission to motor neurons, which return to the same muscle. The stretch reflex occurs when muscle spindles, or afferent neurons along the length of skeletal muscles, are stretched, causing muscle contraction. The stretch reflex, or tendon reflex, is one of the simplest monosynaptic reflexes (reflexes that have only one synapse between the afferent and efferent neurons). There are several somatic reflexes, with the most common categories of somatic reflexes including the stretch reflex, inverse stretch reflex, and the withdrawal reflex.
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Join millions of students and clinicians who learn by Osmosis! Start Your Free Trial What are the somatic reflexes? In the case of the hot stove, this movement may involve removing one’s hand from the stove. The efferent neurons transmit information via neurotransmitters to the muscle cells through the neuromuscular junction, thereby causing muscle contraction and movement. The afferent neuron enters the spinal cord through the back (i.e., dorsal) horn, and the efferent neuron exits through the front (i.e., ventral) horn of the spinal cord. When the information reaches the end of a neuron, it is passed to the next neuron through a synapse (i.e., a small gap between neurons) by chemical messengers called neurotransmitters.Īt the integration center in the spinal cord, the information may connect directly from an afferent neuron to an efferent neuron or may pass through an interneuron (a neuron that transmits information between other neurons). The information travels through a neuron as a result of action potentials, which are electrical signals that occur due to ion movement in and out of the neuron. This sensory information is then relayed through at least one afferent neuron.
The first part of a reflex arc is a sensory input from the environment, like touching a hot stove. This information is then relayed to the efferent, or motor, neurons. The basic pathway relays information from a sensory organ to muscle cells by passing through afferent, or sensory, neurons to the CNS. A somatic reflex arc is the neural pathway that occurs from the initial sensing of a stimulus to the response, such as the moving of a limb.
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