A knee-jerk reflex is a test used to examine a reaction that is caused automatically without thinking or managing it. So let’s say a patient is sitting down with their legs hanging off the chair. We can take a tendon hammer and apply pressure to the patellar tendon by striking it. The strike will stimulate sensory neurons which will send a signal to the central nervous system, which is the brain and spinal cord. At the central nervous system the sensory neuron makes a synaptic connection to a motor neuron. The motor neuron will send the signal to stimulate the quadriceps to contract which causes the leg to be extended. The connection of the sensory neuron and motor neuron form a simple reflex arc. A simple reflex arc does not contain any interneurons. …show more content…
The mechanism is simple, but we must understand what lies beneath the knee-jerk reflex such as the initiation of an action potential, the propagation of a signal and the excitation of the skeletal muscle.
An action potential can be defined as a short lasting electrical event on the plasma membrane of a cell, meaning that it is an electrical current that travels in the human body through neurons and muscle cells. In a neuron, the action potential is referred to as a nerve impulse. First, let’s go over the many parts of a neuron to get a better understanding. The neurons have these antenna like ends that are called dendrites. Dendrites are the part of the neuron that can capture a chemical signal and conduct that signal to other parts of the cell. The chemical signal travels from the dendrites to the body of the neuron which is also known as the soma. An interesting thing about the soma of a neuron is that it has a specific area called the hillock. Once the nerve impulse passes the dendrites, the soma and then finally the hillock, the signal will go through a long axis which is called the axon. The hillock can be described as the connection between the soma and …show more content…
There is a direct relationship between cross sectional and force production. This means that the bigger your muscles are the more force you can produce. We know that if we do hypertrophy training our muscles get larger and we will be able to lift more weight. Strength doesn’t just come from having a large muscle it can also come from a greater neuromuscular efficiency or greater recruitment. Fascicle arrangement is more of an anatomical term, such as that muscles that have a pennate shape are stronger then muscles that have a parallel or longitudinal shape. An example of a pennate muscle is the deltoid, which has fibers that run in many different directions and angles. Abdominal muscle fibers only run in one direction so they aren’t going to be as strong as deltoids. If the size and motor unit is larger it will be able to contract more forcefully. This depends on what the responsibility of a particular muscle is. If its main job is just gross motor movement, like walking or bending your leg, then it will have larger motor units and it is going to be capable of more force production. Recruitment is when you use more of the muscle that we have available, which comes from training. Temporal summation is if the action potential arrive at frequent intervals that will cause a buildup of stimulus. If the frequency of stimulation is greater the force production will be greater. The length tension relationship is the