Reflexes and Reflex Arcs (Nursing)

00:01 So we discussed really briefly a spinal reflex pathway.

00:05 Now let's take a closer look at how these reflexes occur.

00:11 A reflex is a fast involuntary, unplanned response to a particular stimulus.

00:18 Reflexes are necessary in order to help us maintain homeostasis.

00:24 And the grey matter of the spinal cord is very important as it serves as the integrating centre for the spinal reflexes.

00:35 So now let's take a closer look at the reflex arc.

00:40 A reflex arc is going to include the sensory information that goes in as well as the motor information that goes out.

00:49 It starts with sensory receptors and parts of the body that are going to receive a stimulus.

00:57 Next a nerve impulse is propagated down the sensory neuron into the posterior root of the spinal cord.

01:08 In the grey matter of the spinal cord you will have your integrating center.

01:14 After integration, a motor neuron is going to transport a nerve impulse to an effector.

01:23 In integration, there can be two different types.

01:26 The first type is monosynaptic where the sensory neuron is going to synapse directly with the motor neuron.

01:36 In the second type, we have polysynaptic.

01:40 In polysynaptic, the sensory neuron is going to actually synapse with an interneuron first or an association neuron and then that neuron will synapse with the motor neuron and then signal will go to the effector.

01:57 Also in a reflex arc, there are different types of arcs that we can have.

02:03 The first type of arc is an ipsilateral arc .

02:07 In an ipsilateral arc, the sensory information is going to be received and the output or the motor information is going to go to the same side of the body.

02:22 Another type of reflex arc is a contralateral reflex arc.

02:27 In this type of reflex arc, the sensory information comes in on one side of the body is integrated in the grey matter and then leaves out of the other side of the body So in the reflex arc, there are certain vocabulary terms that you should know.

02:45 First, e'll start with ipsilateral.

02:48 In an ipsilateral reflex arc, the sensory neuron and the motor neuron are going to come in and exit out of the same side of the body.

02:58 An example of this type of reflex arc will be a withdrawal reflex when you touch a hot pan.

03:06 In the contralateral reflex, the sensory neuron is going to come in on one side of the spinal cord and the motor neuron is going to leave at an opposite side of the spinal cord.

03:18 An example of this would be when you're trying to maintain your balance such as when you're falling over and your body corrects itself Also, there are two types of reflex arcs.

03:30 You can have monosynaptic where the sensory neuron is going to synapse directly with the motor neuron and you can have polysynaptic where the sensory neuron is going to synapse with an association or interneuron and then that neuron is going to synapse with a motor neuron.

03:52 Please note that a polysynaptic reflex arc can be ipsilateral or contralateral while a monosynaptic reflex arc is always ipsilateral The last term is reciprocal innervation.

04:09 In reciprocal innervation, our body is going to make sure that when the agonistic muscle is contracted, the antagonistic muscle is relaxed.

04:22 This helps us maintain homeostasis so that all of our muscles are not contracting at the same time