Reflex arc diagram

Learning Objectives By the end of this section, you will be able to: • Compare the structure of somatic and autonomic reflex arcs • Explain the differences in sympathetic and parasympathetic reflexes • Differentiate between short and long reflexes • Determine the effect of the autonomic nervous system on the regulation of the various organ systems on the basis of the signaling molecules involved • Describe the effects of drugs that affect autonomic function The autonomic nervous system regulates organ systems through circuits that resemble the reflexes described in the somatic nervous system. The main difference between the somatic and autonomic systems is in what target tissues are effectors. Somatic responses are solely based on skeletal muscle contraction. The autonomic system, however, targets cardiac and smooth muscle, as well as glandular tissue. Whereas the basic circuit is a reflex arc, there are differences in the structure of those reflexes for the somatic and autonomic systems. The Structure of Reflexes One difference between a somatic reflex, such as the withdrawal reflex, and a visceral reflex, which is an autonomic reflex, is in the efferent branch. The output of a somatic reflex is the lower motor neuron in the ventral horn of the spinal cord that projects directly to a skeletal muscle to cause its contraction. The output of a visceral reflex is a two-step pathway starting with the preganglionic fiber emerging from a lateral horn neuron in the spinal cord, o...

\( \newcommand\) • • • • • • • Autonomic reflexes are unconscious motor reflexes relayed from the organs and glands to the CNS through visceral afferent signaling. Key Points • While the unconscious reflex arcs are normally undetectable, in certain instances they may trigger pain, typically masked as referred pain. • The sympathetic nervous system is a quick-response, mobilizing system while the parasympathetic system is a more slowly activated, dampening system—but there are exceptions, such as in sexual arousal and orgasm where both systems play a role. • Within the brain, the ANS is located in the medulla oblongata in the lower brainstem. The medulla’s major ANS functions include respiration, cardiac regulation, vasomotor activity, and certain reflex actions (such as coughing, sneezing, vomiting, and swallowing). Key Terms • reflex arc: A neural pathway that controls an action reflex. There are two types of reflex arcs: the autonomic reflex arc that affects the inner organs, and the somatic reflex arc that affects muscles. • referred pain: Pain perceived at a location other than the site of the painful stimulus. • somatic: Part of, or relating to, the body of an organism. The Autonomic Nervous System The autonomic nervous system (ANS, visceral nervous system, or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system. It functions largely below the level of consciousness, and controls visceral functions. The ANS affects hea...

Synonyms: Neuron motorium A major part of the a spinal reflex. The definition of a spinal reflex as well as their components, functions, pathways, and physiology will be described in this article and is a must-know for every student that is passionate about neurosciences. The clinical importance of spinal reflexes is also essential since the examination of them is an inevitable part of daily clinical practice. This article will discuss the Key facts about spinal reflexes Spinal reflex Receptor --> sensory fiber --> (interneuron) --> alpha motor neuron --> muscle Monosynaptic reflexes Biceps brachii, triceps brachii, brachioradialis, quadriceps femoris, triceps surae reflexes Polysynaptic reflexes Upper abdominal, lower abdominal, cremasteric, plantar, anal reflexes + Show all Basics The spinal cord is phylogenetically older than most structures of the brain, which means that reflexes are in charge of carrying out functions that the organism needs the most. Basically, it is more important to remove your hand from a heat source in order to avoid getting burnt than to be able to speak. Many of the protective functions necessary for survival are embedded within the spinal reflexes. By definition, a reflex is an involuntary, stereotypical response of the effector tissue from the stimulation of receptors. These reflexes are executed by the successive activation of a certain number of neurons that are mutually connected. The last neuron generally innervates the effector tissue, w...

Our body performs many actions that are not under our control. The nervous system of our body detects stimuli and responds even before we become aware of them. Reflex action, or reflex, is one such response of our body. A reflex arc is a pathway that a nerve impulse follows during a reflex action. Reflex arcs are highly beneficial in situations that require a quick response and do not involve conscious thought. A typical example of a reflex action is the patellar reflex (‘knee jerk’ response), which occurs when the patellar tendon is tapped. It is commonly employed to determine the presence of spinal lesions. Components and Steps of a Reflex Arc Reflex Arc A signal travels from the organ and initiates a response to the organ that reacts to the signal. This response causes various parts of the reflex arc to work in order. A simple reflex arc has the following parts: 1. Stimulus It is any change in the environment (internal or external) detected by a receptor. It initiates a response known as the reflex. It can be anything like a heat or cold sensation, an 2. Receptor It detects the stimulus and transmits the nerve impulses to the brain for decision-making. They can be of different shapes based on their origin, such as pain receptors (having free nerve endings), thermoreceptors (containing specialized heat and cold receptors), and mechanoreceptors (having specialized muscle endings like muscle spindle). 3. Sensory Neuron Also known as afferent neurons, they bring the impulse...

the junctions between neurons through which the signals can be sent are called the chemical synapses. they produce some chemicals when electrical signals reach them. these chemicals are neurotransmitters that can bind to the receptors on the motor neuron. this is like an electrochemical circuit which generate electrical signals in the motor neuron that leads to exactly what reaction is required. these reach the muscles cells in which the reflex action take place When we touch a hot surface, reflex action takes place and we move our hand. The doubt I have is that how did we know that that action we did was dangerous and that we knew that we need to remove our hand from the hot surface because we already know that during a reflex action, the message is not received by the brain. So how is it that without thinking, the muscle responds to the stimulus in the form of a reflex action. Basically, how do the muscles know that the action we did calls for a reflex action rather than a normal one? As we got to know the reflex actions are the ones which reacts to a stimulus. These are the actions which can cause any type of damage or harm to our body and this we get to know by our past experiences or what we might have suffered from and the information gets stored in our subconscious mind. Basically reflex actions reacts to physically harming actions. When we touch a hot cup we do know that it can hurt us because we have got hurt the first time we did the same thing and the same goes ...

\( \newcommand\) • • • • • A reflex arc defines the pathway by which a reflex travels—from the stimulus to sensory neuron to motor neuron to reflex muscle movement. Key Points • Reflexes, or reflex actions, are involuntary, almost instantaneous movements in response to a specific stimulus. • Reflex arcs that contain only two neurons, a sensory and a motor neuron, are considered monosynaptic. Examples of monosynaptic reflex arcs in humans include the patellar reflex and the Achilles reflex. • Most reflex arcs are polysynaptic, meaning multiple interneurons (also called relay neurons) interface between the sensory and motor neurons in the reflex pathway. Key Terms • motor neuron: A neuron located in the central nervous system that projects its axon outside the CNS and directly or indirectly control muscles. • sensory neuron: These are typically classified as the neurons responsible for converting various external stimuli that come from the environment into corresponding internal stimuli. • reflex arc: A neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. There are two types of reflex arcs: autonomic reflex arc (affecting inner organs) and...