Structure of the CNS 

The CNS is a highly complex tissue that controls all of the body activities and serves as a processing center that links the body to the outside world. 
It is an assembly of interrelated “parts”and “systems”that regulate their own and each other’s activity. 

1-Brain                                  
2-Spinal cord 

The brain is formed of 3 main parts: 

I. The forebrain
• cerebrum
• thalamus
• hypothalamus

II. The midbrain
III. The hindbrain
• cerebellum
• pons
• medulla oblongata

Different Parts of the Different Parts of the CNS & their functions CNS & their functions
The cerebrum(cerebral hemispheres):
It constitutes the largest division of the brain. 
The outer layer of the cerebrum is known as the “cerebral cortex”. 

The cerebral cortex is divided into different functional areas: 
1.Motorareas(voluntary movements) 
2.Sensoryareas(sensation) 
3.Associationareas(higher mental activities   as consciousness, memory, and behavior).

Deep in the cerebral hemispheres are located the “basal ganglia” which include the “corpus striatum”& “substantianigra”. 

The basal gangliaplay an important role in the control of “motor”activities

The thalamus:

It functions as a sensory integrating center for well-being and malaise. 
It receives the sensory impulses from all parts of the body and relays them to specific areas of the cerebral cortex.

The hypothalamus:

It serves as a control center for the entire autonomic nervous system. 
It regulates blood pressure, body temperature, water balance, metabolism, and secretions of the anterior pituitary gland.

The mid-brain: 

It serves as a “bridge”area which connects the cerebrum to the cerebellum and pons. 
It is concerned with “motor coordination”.

The cerebellum:

It plays an important role in maintaining the appropriate bodyposture& equilibrium.

The pons:

It bridges the cerebellum to the medulla oblongata. 
The “locus ceruleus”is one of the important areas of the pons.

The medulla oblongata:
 
It serves as an organ of conduction for the passage of impulses between the brain and spinal cord. 
It contains important centers: 
• cardioinhibitory 
• vasomotor 
• respiratory 
• vomiting(chemoreceptor trigger zone, CTZ).

The spinal cord:

It is a cylindrical mass of nerve cells that extends from the end of the medulla oblongata to the lower lumbar vertebrae. 
Impulses flow from and to the brain through descending and ascending tracts of the spinal cord.
 

Nystatin

Candida spp. are sensitive to nystatin.

Uses: Cutaneous, vaginal,  mucosal and  esophageal  infections.

Candida infections can be treated with nystatin.

Cryptococcus is also sensitive to nystatin.

Nystatin is often used as prophylaxis in patients who are at risk for fungal infections, such as AIDS patients with a low CD4+ count and patients receiving chemotherapy.

MOA

nystatin binds to ergosterol, the main component of the fungal cell membrane. When present in sufficient concentrations, it forms a pore in the membrane that leads to K+ leakage and death of the fungus.

Factors affecting onset and duration of action of local anesthetics

pH of tissue

pKa of drug

Time of diffusion from needle tip to nerve

Time of diffusion away from nerve

Nerve morphology

Concentration of drug

Lipid solubility of drug

Chloral hydrate

1. Short-acting sleep inducer—less risk of “hangover” effect the next day.
2. Little change on REM sleep.
3. Metabolized to trichloroethanol, an active metabolite; further metabolism inactivates the drug.
4. Used for conscious sedation in dentistry.
5. Can result in serious toxicity if the dose is not controlled.

NSAIDs: Classification by Plasma Elimination Half Lives

Short Half Life (< 6 hours):

more rapid effect and clearance

• Aspirin (0.25-0.33 hrs),

• Diclofenac (1.1 ± 0.2 hrs)

• Ketoprofen (1.8± 0.4 hrs),

• Ibuprofen (2.1 ± 0.3 hrs)

• Indomethacin (4.6 ± 0.7 hrs)

Long Half Life (> 10 hours):

slower onset of effect and slower clearance

• Naproxen (14 ± 2 hrs)

• Sulindac (14 ± 8 hrs),

• Piroxicam (57 ± 22 hrs)

Sulfonylureas

1st generation
tolbutamide
chlorpropamide

2nd generation

glyburide
glimepiride
glipizide

Mechanism

glucose normally triggers insulin release from pancreatic β cells by increasing intracellular ATP
→ closes K+ channels → depolarization → ↑ Ca2+ influx → insulin release

sulfonylureas mimic action of glucose by closing K+ channels in pancreatic β cells 
→ depolarization → ↑ Ca2+ influx → insulin release

its use results in

↓ glucagon release
↑ insulin sensitivity in muscle and liver

Clinical use

type II DM

stimulates release of endogenous insulin 
cannot be used in type I DM due to complete lack of islet function

Toxicity

first generation

disulfiram-like effects
especially chlorpropamide

second generation

hypoglycemia
weight gain