Spinal Cord Flashcards
The (brain/spinal cord) is actually a very complex structure. I think we learn in entry-level content that the purpose of the spinal cord is to carry executive information down from the cortex to the limbs and send sensory information back from the limbs into the cortical regions. So overall the gross function of the (brain/spinal cord) is to carry executive order from the cortex and to send feedback to the cortex.
spinal cord; spinal cord
We have the decorticate cat. And just between the connection from the middle brain and the brainstem into the spinal cord itself, the organism is able to initiate and maintain movement. It does not have the central drive from the cerebral cortex to be able to tell the organism how hard to contract. So it doesn’t have that information. So it needs something to hold itself up, this harness that you see here. But once that harness is there, (motor/sensory) input from the treadmill and from the ground is adequate to produce motion from the spinal cord and some brainstem motions.
sensory
As far as the structure of the spinal cord is concerned, all of these different colored parts represent specific parts of the cord. And each of those parts have different functions depending on where it sits in the cord, but also where it sits with respect to is it in the cervical spine, thoracic spine, or in the lumbar spine. So when we’re just orienting ourselves, this is the anterior aspect ((right/left) of the screen), the big cleft that we see here. So this big divot here represents the anterior or ventral aspect of the spinal cord. And then you have these two larger clumps on the right side, so that is the (anterior/posterior) or (ventral/dorsal) aspect of the cord. And then you have this butterfly shaped structure in the middle. And that’s the (gray/white) area. And then coming out of the cord we have the dorsal and ventral ____ which join together then to form the _____ spinal nerve that is going out into the periphery.
left; posterior; dorsal; gray; roots; peripheral
The distal most end of the neural tube that is going to turn into the (brain/spinal cord). We have the notochord, which is going to become the nucleus _____. So think of where the nucleus pulposus sits within the intervertebral disc and where that is with respect to an anterior or posterior relationship. Everything that is on the anterior or ventral aspect is going to differentiate into (motor/sensory) response neurons. Everything that’s in the posterior region is going to be (motor/sensory) related cells and (motor/sensory) related neurons. There is a dividing space that goes right down the middle here, which is called sulcus ____. And that sulcus _____is important because it (brings together/separates) the anterior and posterior or motor and sensory aspects of the spinal cord gray.
spinal cord; pulposus; motor; sensory; sensory; limitans; limitans; separates
The basal plate is turning into (motor/sensory) related cells and the alar plate is what’s turning into (motor/sensory) related cells. So that means the basal plate is (anterior/posterior) and the alar plate is (anterior/posterior).
motor; sensory; anterior; posterior
In cortical differentiation, the gray is on the outside with the white sitting on the inside, white being the axons because information has to come to and from the cortex. So all the information relays are in the center of the cortex. Here, information has to be transmitted out of the cord. So the white sits on the (outer/inner) aspect of the cord.
outer
In terms of the spinal cord structure within the (white/gray) matter, we have cell bodies and the cell bodies are cell bodies of neurons and interneurons. We also have dendrites, axons, synapsing fibers, and then glial cells, which make up the majority of the bulk of the (white/gray) matter. That blue cell comes in and it synapses with something called an ______. And the job of the ______ is to modulate the incoming signal. So it’s up to those ______to dictate, do I send a stimulating or inhibiting signal down to the receiving neuron based on sensory input that’s coming into me? So the role of the ______ is to take input that’s coming in, modulate and dictate is they’re excitatory or sensory that’s going to be sent down to the target neuron.
gray; gray; interneuron; interneuron; interneuron; interneuron
Volitional movement is something that we call a two motor neuron system. And there is an upper motor neuron and a lower motor neuron. The (upper/lower) motor neuron sits up in the cortical region and it travels from the cortex down the length of the (brain stem/spinal cord) into the (brain stem/spinal cord) to synapse onto the (upper/lower) motor neuron, which sits within the spinal cord. It’s essentially a relay system. So when the cortex wants to drive a volitional movement, so we’re talking about something that is not a reflex, it is something that you want to do, the (upper/lower) motor neuron in the cortex turns on, relays the signal down to the (upper/lower) motor neuron. And then it is up to the (upper/lower) motor neuron to send that signal down to the target organ (skeletal muscles, cardiac muscles, glands, and neurons in the peripheral nervous system).
upper; brain stem; spinal cord; lower; upper; lower; lower
The (upper/lower) motor neurons are neurons in the CNS that terminate on other neurons in the CNS.
upper
(Upper/Lower) motor neurons are neurons in the CNS whose axons terminate on effector organs
Lower
Within this two neuron system, with an upper and a lower motor neuron the motor neuron that is responsible for explicit contraction of the muscle is driven by what’s called the (alpha motor neurons/interneurons). It is the one responsible for activation of the muscle.
alpha motor neurons
(Alpha motor neurons/Interneurons) mediate the passages of signals.
Interneurons
The alpha motor neuron is going to sit within what we call the (dorsal/ventral) gray. It’s going to sit in the (basal/alar) portion of the spinal cord gray matter.
ventral; basal
A motor ___ from an operational definition, is the motor neuron, the alpha motor neuron, and the bundle of muscle fibers that it is responsible for. So within a big muscle, like the quadriceps where you have multiple muscle fibers, you’re going to have multiple motor ___ with multiple motor neurons responsible for a collaborative action potential, resulting in tetanic contraction of that muscle. If something goes wrong and only one motor neuron is activated and only one motor ____ goes to potential, you might see a twitch of the muscle and not a full tetanic contraction.
unit; units; unit
So in a perfectly normal state, it’s going to be the (CNS/PNS) that dictates how many motor units are turned on in order for you to be able to do what you need to do. Ex: I want to pick up a cup of water versus I want to go pick up a bowling ball. The cortical process dictates how that’s pretty light. I only need to bring, I don’t know, 10 motor units into I think it is pretty heavy, I need to bring 30 motor units into the picture.
CNS
The dorsal horn is the part that is responsible for dealing with (motor/sensory) information. So information from different (motor cortices/sensors) are coming in through the dorsal root and passing through the dorsal root ganglia (that big bump that you see in dissection).
sensory; sensors
The dorsal root ganglia and the dorsal root come off the ____ cells. #3 in the pic!
neural crest
In the dorsal root system, that cell body is tucked to the outside so that it (assists in the conduction/doesn’t impede the conduction) of the signal that is going from a receptor at the skin or joint or muscle receptor level all the way back to the spinal cord. And the purpose of that is processing speed and conduction speed.
doesn’t impede the conduction
When we take a look at the dorsal root ganglia, it is some of the (shortest/longest) nerves in the body because it can go from the (brain/spinal cord) all the way down to the fingers, all the way down to the feet. It is what’s called a (real bipolar/pseudo unipolar) neuron because the cell body sits off to the outside and there are no synapses happening on to the cell body. If we take a look at the other neurons that we looked at, there’s a cell body and then there are dendrites that come off of it, that doesn’t exist within this system here. There’s a mechanical receptor here that opens up, sensation is conducted all the way straight through without any other interfering synapses that need to occur to be able to get that information out and into the cord. So (there are/ there are NO) synapses!
longest; spinal cord; pseudo unipolar; there are NO
As far as the spinal nerve from a spinal segment, the spinal nerve is formed once the dorsal root and the ventral root (separate/come together). That is the delineation of the spinal nerve. It is the area that the dorsal root and the ventral root (separate/come together). Once they (separate/come together), those axons bundled together to form the spinal nerve.
come together; come together; come together
There is a another area of the spinal cord with the gray matter that we call the (ventricular/intermediate) zone. The (ventricular/intermediate) zone is a mix of sensory and motor driven cells.
intermediate; intermediate
The intermediate zone is much more prominent in the (cervical/thoracic) spine down to the high lumbar regions. One of the features of this intermediate zone is in (cervical/thoracic) levels from T_ down to L_. There’s this large bump that you see. And that bump is for the processing of the (motor unit/PNS) information. When we get up to regions where the limbs exist, that intermediolateral nucleus (is profound/is not as profound), but what that intermediate area is going to be responsible for is (somatosensation/proprioception). There is a little bit more proprioceptive input that happens at the thoracic level because think of the musculature that the thoracic gray has to innervate - External oblique, internal oblique, longissimus, and all of our trunk musculature has to stiffen to be able to keep us upright depending on what the limbs need to do.
thoracic; thoracic; T1 down to L3; PNS; is not as profound; proprioception
Within the (gray/white) matter of the spinal cord, there are things that we call ____– a passage or elongated continuous structure in the body to send information. These _____ have an ascending or afferent tract and a descending or efferent tract. So ascending is going (away/towards) from the end organ towards the (brain/spinal cord). And then we have information that is going down or descending from the (brain/spinal cord) and effecting the end organ. So we have what’s called afferent fibers, which are typically going to be (motor/sensory) input that’s being sent from receptors, from the skin, to give us a sense of what’s going on. And then we have descending tracts which are going to be there for the brain to communicate with the spinal cord itself.
white; tracts; tracts; away; brain; brain; sensory;
Focusing on afferent fibers… All this information comes through on that dorsal root here. And it separates into three different parts. We have the black part here, which is what we call the general (somatic/visceral) afferent responsible for (proprioception/exteroceptive). What am I doing? The red is responsible for general (somatic/visceral) afferent as well, but these are (proprioception/exteroceptive) fibers - What’s the outside doing to me, is something touching me, is something harming me? And then we have general (somatic/visceral) afferent, which are in the green. We’re going to find them in the (thoracic/lumbar) segments. And here, if we are in the (thoracic/lumbar) segments, those are our (exteroceptive/interoceptive) fibers. What are my insides doing? Those are coming off of visceral sensory endings, going through the communicating ramus and then rejoining the dorsal root within the ganglia and then coming into that dorsal gray region.
somatic; proprioception; somatic; exteroceptive; visceral; thoracic; thoracic; interoceptive
In the anterior aspect/root is where we have our (afferent/efferent) fibers. The general somatic efferent fibers are going to be responsible for synapsing onto (cardiac/skeletal) muscles and resulting in muscle contraction. We have in green coming here, going kinda does a little dip, it comes down, dips into the communicating ramus, and then back out into (skeletal/visceral) motor endings. There’s a processing of sensory input that happens here to take care of any sort of reflexing that didn’t happen, and then come back out via visceral motor endings. When we take a look here. So let’s take a look at the proprioceptive ending that’s coming in. This black dotted line here. Heavily myelinated fibers comes in. And there’s two tracks that happen. You see two arrows. One arrow is traveling up. That’s information that’s going up to the (brain/motor neuron). But there’s another big part that comes right off and it synapses directly onto (the brain/ a motor neuron) coming into the general somatic efferent fibers. That is the circuitry that we have for reflexive loop.
efferent; skeletal; visceral; brain; a motor neuron
A similar synapse region of 2 different fiber types coming from different areas and tissues, but (separating/coming together) in similar location on the spinal cord causes _____ pain.
coming together; referred
