Sensory Pathways – Sensory Processing (PSY, BIO)

00:02 Okay, now -- now that we have a sensory stimulus coming in, we need to detect that and that needs to go through a sensory pathway.

00:10 So it’s a really, really cool unique thing.

00:12 And now with all these different types of sensory receptors, that allows us to actually capture all the different senses that we’re inundated with.

00:20 And again, I think you and I all take this for granted when we’re thinking of all the different stimuli that we, on an everyday basis, deal with, interact with and assess.

00:28 But when you start getting down to the physiology behind in the fact that, “Oh my God. We actually detect a lot of different things.” It’s super cool So sensory receptors are sensory nerves that are -- one of two things, either a cell or nerve endings.

00:41 And they can detect both internal and external stimuli.

00:45 So things that are happening within our own bodies or things that are happening from the outside affecting our bodies.

00:51 Activation initiates a signal transduction by creating graded or action potential.

00:56 So you remember from the biology sections, an action potential has an all or none activation.

01:01 It causes opening of voltage-gated ion channels, you have influx of ions.

01:05 That whole process can be initiated through activation of these, of these receptors.

01:12 So sensory pathways begin with the receptor.

01:15 The receptor then gets activated and it goes through some ganglion cells and then through another process, it goes through the spinal cord, it gets sent up to the central nervous system where it’s processed.

01:25 So the idea is, think of your body as an antenna and it’s trying to detect all types of stimulus.

01:31 And all that information gets converted into whatever medium it is, into basically an electrical signal, because everything in our body is electrochemical.

01:39 And now it gets converted, gets passed along the ganglion cells, goes up through the spinal cord, through the central nervous system where your brains says, “Okay, what just happened? Let me interpret that and let me respond to that.” Okay? So we’re going to walk through that in a sort of a flowchart here so this makes a little more sense.

01:56 So a receptor activated by a sensory stimulus and that will all be done through a sensory receptor.

02:02 So that sensory receptor will then initiate a -- sorry, will activate a sensory ganglion cell.

02:08 And that’s a term that you should know, a sensory ganglion cell, and that will cause an action potential or graded potential.

02:15 And that cascade, the electrical signal, will then continue and it will go to the spinal cord and that signal is then sent up and processed in the central nervous system.

02:24 So here’s kind of a scary looking complicated diagram and we’re going to break it down to something pretty simple.

02:29 And what you’re seeing here is an individual and various types of sensory pathways that can be activated.

02:35 So we can have things like your taste bud.

02:38 You can have your derma layer in your skin.

02:41 And really the point that I want you to have here is that you have a receptor somewhere.

02:45 Whether it’s taste, whether it's dermal, whether it’s, you know, your urinary bladder which would be an internal receptor and it’s going to get activated.

02:55 And once it’s activated, it will initiate that sequence of having electrical signal and that will go down the ganglion cell.

03:01 And what you’re seeing here in the middle of this looking thing with an X is the spinal cord has been transacted and you’re seeing the dorsal horn.

03:09 And it’s going to actually go cross lateral.

03:11 So it’s going to -- what you’re feeling on the, say, your right hand is actually going to cross the spinal cord and go up to the left side of your brain and vice versa for either side.

03:21 So what we’re looking at here is the movement of information.

03:25 So activation of the sensory receptor going into an electrical signal up the spinal cord to the brain.

03:31 Okay? So, for the MCAT, for example, I don’t think you’re going to need to redraw a diagram like this, but you would need to understand that process that we just outlined.

03:41 And we’ll do it again through this diagram, which is again, an arbitrary diagram showing various types of receptors.

03:47 At the very top where you see A, B, and C, we’re seeing different types of receptors, whether it’s a free nerve ending, whether it’s a sensory cell, whether it’s a peripheral cell.

03:56 They’re going to get activated.

03:58 And they’re all designed to detect a certain type of stimulation.

04:01 And now we’ll activate the ganglion cells.

04:05 Those get sent down and through the spinal cord up to the central nervous system, in the CNS, where they’re processed.

04:11 Okay?