Spinal and Cranial Nerves

Spasticity = STIFF muscles — If the muscles are stiff they have hypertonia
Hypertonia is the resistance to movement and increased muscle tone. People with hypertonia will also have reduced muscle flexibility
Any kind of muscle can be damaged, therefore our speech muscles could be damaged
- Damage to the speech muscles from UMN damage could come in the form of spastic dysarthria

2. The Peripheral Nervous System (PNS)

Lower Motor Neurons (LMN) are known as the second order neurons, which consists of the cranial and spinal nerves. They make up the final common pathway for nerve impulses. Their goal is to execute the job, whereas the UMNs make the decisions.

When there is damage to the LMN:

There can be lower motor neuron paralysis, which is when the muscle is no longer working
Lower motor neuron paresis is when the muscle is weakened
ipsilateral damage - meaning damage only happens on ONE side
Denervation can occur — this causes the muscles to become soft and flabby because of loss of muscle tone (hypotonia)
- damage to the speech muscles can result in flaccid dysarthria

SO MANY NERVES…SO LITTLE TIME!

We have about 31 PAIRS of spinal nerves! They start at the spinal cord and make up pairs. Whatever side they start on is the side they “work” for, meaning they innervate muscles that are on the same side they originate from. There are different kinds of spinal nerves:

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

Some of these nerves help with speech and language. For example,

The rest of your PNS is made up of your 12 pairs of cranial nerves, which are part of the corticobulbar tract — they are:

12 Cranial Nerves

Olfactory — Sensory
Optic — Sensory
Occulomotor — Motor
Trochlear — Motor
Trigeminal — Both
Abducens — Motor
Facial — Both
Auditory (Vestibulocochlear) — Sensory
Glossopharyngeal — Both
Vagus — Both
Accessory — Motor
Hypoglossal — Motor

Cranial nerves receive information from the context or the extrapyramidal nuclei. They branch out from the medulla and pons. They consist of efferent (downward) motor fibers that start at our brainstem and go where they are intended to go. Some of these cranial nerves have afferent sensory fibers. Cranial nerves either have sensory functions, motor functions, or a mix of both functions.

BASICS OF UPPER MOTOR AND LOWER MOTOR NEURONS

As we know, there are TWO types of nervous systems:

1. The Central Nervous System (CNS) -The Brain and Spinal Cord

Upper Motor Neurons (UMN) are also known as first order neurons, which consist of the brain and spinal cord. They make up the direct activation pathway where decisions are made. These “decisions” or impulses never leave the neuraxis

When there is damage to the cerebrospinal tract or corticobulbar tract, the UMNs can be damaged. Some examples and/or signs of this are:

http://sevneurology.com/pbvetsociety-spinal-cord-lecture/