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Pharm: CNS properites Block 3


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Describe the capillary endothelium of the brain.
-not support vesicular transport
-histamine, 5HT, and NE do not inc. its permeability
-no contractile proteins
-enzymes regulating transport of AA, amines and hexoses
Where else is capillary endothelium of the brain found?
pia and arachnoid, retina
How many membranes must CNS drugs cross?
2 lipid membranes: the basement membrane from the glial cells and the endothelium layer that is connected by tight junctions
What is the choroid plexus? type of cells?
secretes the CSF and lines the ventricles.

Areas with fenestrated epithelial linings of the CNS? (i.e. no BBB)
pineal gland
pituitary gland
median eminence
area postrema
wall of the optic recess (suprachaismatic and supraoptic nuclei of the hypothalamus-control bio rhythms and pit. control)
Areas with fenestrated epithelial linings of the PNS?
*olfactory receptor cells
*terminal endings of *peripheral nerves (site entry for virus)
*sensory ganglia of SC and CN
*part of the optic nerve (P scleral foramen)
What impairs the BBB?
*heavy metals (Pb, Hg, Mn)
*degenerative, inflammatory and autoimmune dz
*HTN (>200)
*convulsions (electroshock, hypoglycemia)
Factors that facilitate diffusion rate across BBB?
*lipid/water partition coefficeint
*Carrier-mediated facilitated diffusion
Factors that impede diffusion rate across BBB?
*level of ionization of the drug in plasma (ionic not cross)
*binding to plasma proteins
*Hydrogen bonding with H20
*enzymatic degradation within endothelial cells
General description of CNS drugs.
*high lipid solubility
*large Vd,extensively redistributed
*duration of action << half-life
*Cleared by hepatic metabolism
*no diffusion barrier between CSF and ECF, intrathecal admin
Only CNS drug that is not highly lipid soluble?
Which class of drugs produces a life threatening withdrawal?
Sedative hypnotics:
Benzos, barbituates, and alcohol
Name the catecholamines
NE, epinephrine, dopamine
What are the neurotransmitters of the CNS?
NE, Epi, Dopamine, serotonin, histamine
Name the types of NE receptors and what they are coupled to?
B-receptors: inc. CAMP--excites
A1R: inc. neuronal excitability
A2R: neuronal inhibition (pre and post-synaptic)--sedation, analgesia, hypotension
Describe the Locus coeruleus.
*NE cell bodies
*collaterals to entire brain
*stress, nociceptive stimuli, maintenance of waking state.
*Part of Reticular Activating System
Parts of the brain richly innervated by NE neurons
*dorsal horn-snesory modulation
*intermediolateral cell column-
BP and other sympath. funct.
*most autonomic medularry nuclei
*hypothalamic nuclei (some)
*limbi system
Role of adrenergic neurons in the CNS

*central regulation of stress
*autonomic functions
Location of dopamine cell bodies
*mesencephalon (ventral tegmental area (VTA), substantia nigra)
*diencephalon (thalamus, hypothatlamus)
Location of Dopamingergic neurons and their role/function
* Midbrain (substantia nigra)-motor function
*Basal forebrain-personality and affects/motivation and reward
*Hypothalamus- endocrine- inhibit prolactin release
Location of serotonergic cell bodies in CNS
midline series of brainstem nuclei: raphe nuclei
Projections of Serotonergic neurons and their function?
*limbic system-mood
*hypothalamus-appetite and hormone production
*dorsal horn-pain
*intermediolateral column and ventral horn-inc. sympathetic and somatic motor outflows
*brainstem-breathing [infant-respiration; adult-airway diameter]
Describe the cycle of sertonergic neuron action.
active during waking, less so during SWS and not active in REM.
Location of Serotonin in the periphery?
*In platelets-not produced here;absorbed from blood
*Enterochromaffin cells of the GI tract
Location of histamingeric neurons in the CNS
Not produced in CNS; except for a cluster in the hypothalamus
Receptors H1 and H2 located in a cluster in the hypothalamus
regulation of sleep-waking cycle

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