1. sensory neurons

   Neuron Structure

 anaxonic neurons: many dendrites but     no visible axons
                                     nobody is sure              what they do...
 

 ​PNS:
​1. Schwann cells: myelinate axons of PNS neurons
2. Satellite cells: regulate levels of nutrients and neurotransmitters

        next up...
​what is an action potential and how is it initiated/propagated?

glucose, amino acids, thyroid hormones, choline, and some other molecules can cross the barrier using carrier mediated transport proteins.  

the myelin sheath allows electrical impulses to travel along the length of the axon quickly. 

2. motor neurons

Caffeine is often combined with pain relievers like aspirin because it can enhance their effectiveness by increasing the speed and efficiency of absorption. 
caffeine can cross the blood-brain barrier but it doesn't significantly impact aspirin's ability to cross and reach the brain. caffeine can improve overall pain relief by potentially tightening the blood-brain barrier and impacting pain perception mechanisms. 

The Nervous System:
​   Neural Tissue

         Types of
​   Neural Tissue

neuroglial cells with tight junctions form the barrier

the blood brain barrier (bbb)

        peripheral nerve regeneration

The blood-brain barrier creates a huge challenge for drug delivery to the brain. it restricts the passage of most drugs from the bloodstream into the brain. this hinders the development of effective treatments for brain diseases. 

multipolar neurons:   have two + dendrites and one axon
                                       most common type
                                       these are the motor        neurons that convey 
directions to effectors

 demyelination: destruction of myelin results in the loss of motor
control and sensation

 Welcome to Dr. Kate Brilakis' Learning Portal

Aspirin can cross the blood-brain barrier, meaning it can enter the brain. This ability is related to its chemical structure and the way it's metabolized. Aspirin's ability to cross the blood-brain barrier is primarily due to its lipid solubility, meaning it can dissolve in the fatty membranes of the barrier.

there are 100 x 10*9 neurons
​in our body
​neurons in CNS do not have centrioles so they cannot mitotically divide

proteins and polypeptides cannot cross the barrier


  bipolar neurons:  rare, tiny (<30micrometers)       cells that are            found in sense organs like the eye

  

 types of neuroglial (glial) cells:
​CNS vs PNS

   structural classification of neurons

        schwann cells and myelination

 water, CO2, O2, free steroid hormones, alcohol and lipid soluble molecules can diffuse at will across the BBB

 Motor/efferent neurons have cell bodies in the CNS. Their axons extend outside of the CNS to control muscles via a neuromuscular junction. Motor neurons are multipolar  with a single axon and multiple dendrites and are either:
1. somatic: innervate skeletal muscles cell body in CNS...axon runs to muscle junction
2. visceral: innervate all else...smooth/cardiac muscle and glands

  unipolar neurons: sensory neurons of  the PNS with axons    that may run 
>1 meter long!
axon starts where    the dendritic branches converge 

3. interneurons

 demyelination

 CNS:
1. Astrocytes:
    maintains the blood brain barrier, stabilizes damaged tissue, cytoskeleton provides
         CNS framework, directs fetal neuron development, regulates interstitial fluid
         (ions/nutrients/Co2)

2. Oligodendrocyt​es:
    provide myelination (membranous wrapping) for CNS axons via cytoplasmic "pad"
        wrapping around axolemma = myelin internodes, provide structural framework
        by binding adjacent neurons

3. Ependymal cells:
     line the ventricles/central canal of brain/spinal cord and produce CSF. 

4. Microglia: roving phagocytes that remove wastes and pathogens

 Interneurons are found in the CNS and serve to relay info between sensory and motor neurons. Their structure is also multipolar. 

   Neurons

 Sensory neurons/afferent neurons receive external stimuli like light, sound, smell, contact, heat from the environment and convey this information to the brain/spinal cord. Sensory neurons are often unipolar with an axon that branches into two extensions; one dendritic that receives the stimulus and and one axon that transmits the sensory info to the spinal cord. 
Their cell bodies are found in sensory ganglia. 

Sensory neurons may be:
1. somatic: receive info about outside environment
2. visceral: receive info about internal environment

there are:
interoceptors: monitor organ systems re stretch, pressure
exteroceptors: monitor external environment re touch, temp, pressure, taste, sight, hearing
proprioceptors: monitor skeletal system re position/movement

   in summary...

   functional classification of neurons