These messages are action potentials , and they travel along the neurons and send messages, special parts of the neurons are involved. The neuron has three different parts that allow signals to be sensed, to travel, and then move to another neuron or muscle.
These three parts are called the dendrites, the axon, and the nerve ending Figure 1. The dendrites receive information from the sensor or other neurons. This information then moves to the axon, which travels to or from the spinal cord. The action potential travels from the nerve endings at one end of the neuron to the next neuron. Many reflexes start at the muscle or skin and go to the spinal cord.
When the action potential reaches the nerve ending, the signal is transferred to another neuron, such as an interneuron or motor neuron. The action potential then travels outside the spinal cord to a muscle. But the neurons do not touch each other in the spinal cord and do not touch at the muscle. There are tiny spaces called synapses that the action potential must jump across. Doctors will perform a test to make sure reflexes are working properly because reflexes can change if you are sick and as you grow.
Imagine you are sitting up on the exam table and the doctor taps you just below the knee with a rubber hammer. Hopefully, the doctor moved out of the way! The response to the tap of the rubber hammer is called a knee-jerk reflex, but scientists and doctors call it a monosynaptic reflex —the simplest reflex that occurs inside your body [ 2 ].
Monosynaptic is an important word because it describes how the reflex works. When broken into two parts, the word is easier to remember. That means, in the knee-jerk reflex, there is only one point where the message transfers between neurons, so it is monosynaptic.
This monosynaptic reflex is called simple because it works through only four separate parts, whereas most reflexes work through five parts. The five parts of most reflexes are:. A sensor, which is a receptor that senses or detects a change. The monosynaptic knee-jerk reflex skips the interneuron, so it involves the sensor, sensory neuron, motor neuron, and muscle fiber Figure 2. In a monosynaptic reflex, the message travels from the sensory neuron to the motor neuron with only one synapse.
If you think about a relay race with a baton, this is similar to the way a reflex works. The runner with the baton is the action potential, and it is carried down the neuron, which is part of the track.
When the runner and baton get to a specific area on the track, the baton is transferred to the next runner to move along the track. A reflex is just like a relay race, but in a reflex, it is the action potential that moves between neurons rather than a baton and runner along parts of the track Figure 3.
In the above example of a monosynaptic reflex, the interneuron is not used. It is easy to add an interneuron; just add another runner and baton, but this runner travels a very short distance. In our body, interneurons are in the spinal cord. So, when an interneuron participates in a reflex, there is more than one synapse, and these reflexes are then called complex reflexes. There are many different reflexes in the body.
Some of them are complicated and involve multiple interneurons and many synapses. This adaptation, however, is obtained only within narrow boundaries, because as a rule it is given as a response to a relatively small amount of stimuli, and has a generalized character, not too variable.
They are inborn and constant reflexes that allow a relatively imperfect adaptation of the organism to the variable conditions of life. Then, what brings the child when he is born?
He brings a group of unconditioned reflexes that allow his survival, that is:. The grasping reflex, the Moro reflex, and the natatorial reflex, among others. Of survival reflexes, one of the most important in child's development is the suction reflex, which permit the nourishment of the newborn child.
If this reflex does not manifest itself, or if it is manifested with limitations, this may be an indication of problems in development of the child. Because of this, any person working with children must be very much aware of the manifestation of this reflex so as to take the corresponding actions.
The defense reflex allows a newborn baby, in a way, to fight for its survival. The defense reflex is commonly accompanied by immediate cry, which can be the indication that a noxious stimulation is acting upon the baby and compels to give it the most immediate attention. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1.
DNA Structure 2. Transcription 3. Translation 8: Metabolism 1. Metabolism 2. Cell Respiration 3. Photosynthesis 9: Plant Biology 1. Xylem Transport 2. Phloem Transport 3. Plant Growth 4. Plant Reproduction Genetics 1.
Meiosis 2. Inheritance 3. Speciation Animal Physiology 1. Antibody Production 2. Movement 3.
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