Patho: Chapter 15 ( Disorders of Neuromuscular Function)

What is paralysis?

Loss of movement

What is paresis?

Weakness

What is plegia?

Stroke or paralysis

What body region does mono- refer to?

One limb

How many limbs are affected in monoplegia?

One limb

What body region does hemi- refer to?

One side of the body (left or right).

How many limbs are affected in hemiplegia?

Two limbs, on one side of the body (left or right).

What body region does para- refer to?

Two lower limbs

How many limbs are affected in paraplegia?

Two lower limbs

What body region does quadri- (or tetra-) refer to?

All four limbs.

How many limbs are affected in quadriplegia

All four limbs.

What is Muscular Dystrophy (MD)?

A group of inherited disorders characterized by progressive degeneration and necrosis of skeletal muscle.

What causes Muscular Dystrophy (MD)?

• Mutations in the dystrophin gene

• Defective or absent dystrophin protein

• X-linked recessive inheritance

What are some characteristics/manifestations of Muscular Dystrophy (MD)?

• Progressive muscle weakness

• Degeneration of skeletal muscle

• Necrosis of skeletal muscle

• Loss of muscle function

• May lead to replacement of skeletal muscle with connective tissue

Is Muscular Dystrophy (MD) an X-linked recessive disorder?

Yes

What is dystrophin?

A protein expressed in many tissues, including skeletal and cardiac muscle cells.

What is the function of dystrophin?

• Attaches portions of the muscle sarcomere to the cell membrane

• Maintains structural integrity of skeletal and cardiac muscle cells

What are Neuromuscular Junction (NMJ) problems?

• Drug-induced disorders

• Toxin-induced disorders

• Myasthenia gravis (MG)

What is botulism?

A neuromuscular junction disorder caused by the neurotoxin produced by Clostridium botulinum.

What causes botulism?

Neurotoxin produced by Clostridium botulinum.

What effect does botulism have on the Neuromuscular Junction (NMJ)?

• Decreases acetylcholine (ACh) release

• Produces paralysis

Do physostigmine, neostigmine, organophosphates inhibit acetylcholinesterase?

Yes

What happens when acetylcholinesterase is inhibited?

• Acetylcholine (ACh) action is prolonged

• Muscle contraction is prolonged

Can organophosphates be found in isecticides?

Yes

What happens when organophosphates inhibit acetylcholinerase?

• Acetylcholine (ACh) action is prolonged

• Muscle contraction is prolonged

What is Myasthenia Gravis (MG)?

An autoimmune disease characterized by gradual destruction of acetylcholine receptors (ACh receptors).

What causes Myasthenia Gravis (MG)?

Autoimmune destruction of acetylcholine receptors (ACh receptors).

What happens in a patients with Myasthenia Gravis (MG)?

• Gradual development of weakness

• Weakness progresses from proximal to distal portions of the body

What are the first signs of Myasthenia Gravis (MG)?

Drooping eylids (ptosis)

What is the development of Myasthenia Gravis (MG)?

• Thymus tumor

• Thymic hyperplasia

What happens in a Myasthenia crisis?

Respiration is compromised

What are Peripheral Nerve Injuries?

Disorders involving damage to peripheral nerves.

What causes Peripheral Nerve Injuries?

• Damage to the myelin sheath (demyelination)

• Schwann cell disorders

• Primary injury to a neuronal cell body

• Damage to axons in peripheral nerves

What are the types of Peripheral Nerve Injuries?

• Dymelination

• Axonal degeneration

• Mononeuropathy

• Polyneuropathy

What is dymelination?

Damage to the myelin sheath.

What is Axonal degeneration?

Damage to the neuron or its axon.

What is mononeuropathy?

Damage to one nerve.

What is polyneuropathy?

Damage to many nerves

What is Carpal Tunnel syndrome?

A mononeuropathy caused by compression of the median nerve as it travels through the carpal tunnel.

What causes Carpal Tunnel syndrome?

Compression of the median nerve in the carpal tunnel

Is Carpal Tunnel syndrome an example of a mononeuropathy?

Yes

What is Guillane-Barré syndrome?

An acute immune-mediated polyneuropathy that causes progressive nervous system manifestations.

What causes Guillane-Barré syndrome?

Immune-mediated damage to peripheral nerves

Is Guillane-Barré syndrome an example of a polyneuropathy?

Yes

What causes back pain?

• Compression of a nerve root by vertebrae

• Compression of a nerve root by a vertebral disk

• Problems involving spinal structures

• Peripheral nerve injury at the spinal roots

What is a herniated disk?

The protrusion of the nucleus pulposus into the spinal canal, causing irritation or compression of a nerve root.

What causes a herniated disk?

• Trauma

• Aging

• Degenerative disorders of the spine

What are the characteristics/manifestations of a herniated disk?

• Portrusion of the nucleus pulposus into the spinal canal

• Irritation of a nerve root

• Compression of a nerve root

What is Tourette syndrome?

A disorder characterized by tics and hyperkinesia resulting from basal ganglia dysfunction.

What causes Tourette syndrome?

Basal ganglia dysfunction

What are the characteristics/manifestations of Tourette syndrome?

• Tics

• Hyperkinesia (excessive movement)

What are Tics?

Sudden, repetitive, involuntary movements or vocalizations.

What is Hyperkinesia?

Excessive movement or abnormally increased movement.

What is Parkinson’s Disease?

A degenerative disorder characterized by progressive destruction of the nigrostriatal pathway and a reduction in striatal dopamine.

What causes Parkinson’s Disease?

• Progressive destruction of the nigrostriatal pathway

• Reduction in striatal dopamine.

What are the characteristics/manifestations of Parkinson’s Disease?

• Tremor

• Muscle rigidity

• Bradykinesia

• Loss of postural reflexes