Neuroanatomy

Some Pictures from: Interactive Atlas Software< Copyright

 I. Anatomical Planes A. Cuts

1. Medial/SaggitalVisible Human: Planes of Sectioning

2. CoronalVisible Human: Planes of Sectioning

3. Horizontal/TransverseVisible Human: Planes of Sectioning

First we have the cuts. These are important so you know what you’re looking at with some of the brain structures. A corpus thalamus, for example, looks quite different if you’re looking at a saggital cut compared to a transverse cut.

This young woman was kind enough to pose for these pictures illustrating A) the transverse (or horizontal) plane, which divides the brain into top and bottom; B) the coronal plane, which divides the brain into front and back; and C) the sagittal plane, which divides the brain into left and right.

 I. Anatomical Planes A. Cuts

1. Medial/SagitatalVisible Human: Planes of Sectioning

2. CoronalVisible Human: Planes of Sectioning

3. Horizontal/TransverseVisible Human: Planes of Sectioning

B. Directional Reference1. Anterior/Posterior2. Superior/Inferior3. Rostral/Caudal4. Ventral/Dorsal5. Medial/LateralIn addition to the cuts above, we also have directional

references. Some of these are common to other anatomical locations in the body, and others are usually reserved for the brain.

You can see from this slide why we have some added directional terms for neuroanatomy. Posterior refers to “in back of,” however, in the brain it makes more sense to use the term “dorsal.” The very top of the brain– where you would place a hat– is dorsal to the chin. The back of the neck is also dorsal to the chin. However, the top or your head is superior to the chin, not posterior. Dorsal refers to a direction that is as if a dorsal fin were present along the top of the head and extending down the spine. The opposite direction is ventral.

Caudal, refers to “toward the tail.” In this case, we’re talking about our tail-bone or spine. While you’re referring to the spinal column, you may just as easily say “inferior,” however, because the brain has evolved in a superior/anterior direction, we need the paired opposites “caudal/rostral” as you can see in this slide.

Finally, we have medial/lateral, which refers to toward the midline and away from the midline.

In this slide you can see the consequences for some of these directional terms. For example, the coronal plane divides the brain into anterior and posterior portions. The face is ventral to the back of the head.

II. Neuron Basics

A. Cell Body

B. Dendrites

C. Axons

D. Synapses

E. Myelin

At the microscopic level, I want you to recognize the cell body, sometimes called the soma.

The dendrites receive neural impulses, usually from other neurons. Axons send or conduct impulses to other neurons or to muscle fibers. Synapses are the junctions between one neuron and the next.

When I say one neuron and the next, I want you to think of that first neuron as the “pre-synaptic” neuron, and the second neuron as the “post-synaptic” neuron.

Myelin is the name of a fatty substance that surrounds many of our axons– forming what we call a myelin sheath. Myelin is white in color, hence the term “white matter.” Two types of cells manufacture myelin. In the central nervous system that cell is called an oligodendrocyte. In the peripheral nervous system it’s called a Schwann cell.

The myelin sheath acts as an insulator, making the neural impulse more efficient. This will come up again when we get to some of the demyelinating diseases related to dysarthria.

III. Neurophysiology of Speech A. Central Nervous System

1. Brain

2. Spinal Cord

First let’s talk about the central nervous system. So we’re all on the same page, the CNS comprises the brain and the spinal cord.

So in this slide, the CNS includes everything EXCEPT the cranial and spinal nerves (the latter of which are labeled on the left-side of the slide).

III. Neurophysiology of Speech A. Central Nervous System

1. Brain

2. Spinal Cord

3. Neuronal Types

a) Tracts or Pathways

1) Commissural

2) Association

3) Projection Fiber Tracts

(a) Sensory

(b) Upper Motor Neurons

So we have neurons and we have a nervous system. Let’s talk about how these neurons fit into the system. We need to think of this in terms of centers and pathways. The centers comprise regions (mostly in the cortex) that provide a particular function. We call those centers nuclei if they’re in the central nervous system. So for example, the motor strip is a nucleus; Broca’s area is a nucleus.

If you picture those neuron cell bodies in the nucleus we call the motor strip, and you think about it long enough, eventually you’ll get to the questions of where do all the axons go that originate (i.e., whose cell bodies originate) in the motor strip. It turns out that they project down to the brain stem and ultimately to muscle tissue. But let’s talk about the three types of tracts or pathway.

Neurons, it turns out, tend to travel in one of three directions: a) from one hemisphere to another (commissural); b) within a hemisphere (association); or c) projection (from within the brain to outside the brain).

B. Peripheral Nervous System1. Sensory Nerves2. Skeletal Nervous system

a) Lower Motor Neurons1) Cranial Nerves2) Spinal Nerves