PATHO WEEK 3:

Nervous System Functions

The nervous system plays a critical role in the body, involving protection and various functions. Key components of the nervous system include different types of tissues. Each layer of the nervous system has a specific function, particularly neurons, which consist of three main parts: soma, dendrites, and axons. Dendrites are responsible for receiving information, while axons transmit it, often enhancing the action potential via electrical signals. Neurons communicate through two primary mechanisms: action potentials and chemical communication via neurotransmitters.

Neuronal Communication

1. Action Potentials: Relate to the movement of electrolytes and involve the crossing of a threshold of electrical charge.

2. Chemical Communication: Involves neurotransmitters that act as relay systems within the nervous system.

   • Reticular Formation: Acts as a gatekeeper for incoming information, meaning it can either stimulate or inhibit neuronal responses based on the input.

Insulation in Neurons

The axons of neurons are insulated to facilitate faster transmission of electrical signals, which is achieved through the interaction with glial cells. One type of receptor relevant to this discussion is molybdenum, which attaches to synthetic receptors like alpha and beta receptors.

Peripheral Nervous System (PNS)

The PNS consists of various nerves, including somatic and autonomic systems. The somatic nervous system controls voluntary muscle movements, while the autonomic nervous system regulates involuntary functions through sympathetic and parasympathetic responses. The sympathetic nervous system prepares the body for "fight or flight" responses, causing effects such as pupil dilation and increased heart rate, typically mediated by norepinephrine acting on alpha and beta receptors.

Neurological Conditions and Brain Function

The brain constitutes roughly 2% of body weight yet consumes about 20-30% of the body's oxygen and cardiac output, highlighting its high metabolic demand. Pressure changes in the cranium can cause significant issues, as noted in conditions such as hydrocephalus, characterized by excessive cerebrospinal fluid (CSF) accumulation. This often occurs due to blockages in areas such as the Aqueduct of Sylvius and Foramen of Monroe.

Hydrocephalus

• Causes: Can result from congenital mutations, such as the L1 CAM mutation known to cause developmental issues. Symptoms include a visibly enlarged head and various neurologic complications, like seizures.

• Neurological Imaging: Vital in assessing hydrocephalus, allowing for detection of excessive fluid accumulation.

Meningitis Types and Complications

Meningitis can be viral or bacterial, with viral forms labeled as aseptic meningitis. Key symptoms include fever, headache, and nuchal rigidity (stiff neck). The definitive diagnosis often requires lumbar puncture (LP) to analyze CSF, with significant differences between bacterial and viral forms regarding appearance, glucose, and white blood cell counts.

Important Signs

1. Brudzinski's Sign: Flexing the neck may cause involuntary leg flexion, indicating meningeal irritation.

2. Kernig's Sign: Involves the inability to straighten the leg when flexing the hip.

Diagnostic Imaging

In cases of suspected meningitis, a CT scan may be conducted before an LP to avoid complications like herniation based on elevated intracranial pressure. Common pathogens responsible include streptococcus pneumoniae and various viral pathogens.

Stroke Types and Treatment

Strokes can be ischemic or hemorrhagic, with the former being the most common. Ischemic strokes are further classified into thrombotic (caused by clot formation) and embolic (due to traveling clots). Symptoms and severity vary depending on the type of stroke experienced. Treatments for ischemic strokes focus on restoring blood flow, often through thrombolytics, while hemorrhagic strokes require careful management to stabilize the patient.

Conclusion

Understanding these mechanisms and signs is crucial for effective diagnosis and treatment within the neurological context. Proper intervention can drastically change the outcomes for patients suffering from neurological disturbances.