Flashcards in Case 7 Deck (20):
Outline the steps of the direct pathway
1)The stiratum is excited via D1 type receptors
2)The striatum usually sends inhibitory signals to GPi and SNpr, when stimulated it is more inhibitory
3)Usually the impulses from the GPi and SNpr are inhibitory, so when they are inhibited more their inhibitory signals to the thalamus stop.
3)The thalamus then increases its signals (which are excitatory) to the motor cortex, causeing an increased movement.
Outline the steps in the indirect pathway
1)Striatum excited by D2 receptors, increases impulses to GPe (more inhibitory)
2)GPe usually inhibits subthalamic nucleus, but this inhibition is stopped by the striatums impulses.
3)Subthalamic nucleussends more (excitatory) impulses to the GPi
4)The GPi sends inhibitory signals to the thalamus, which prevents the excitatory signals from the thalamus exciting the motor cortex, so there is less movement.
The spiny neurons of the corpus striatum project into the SNpc, which in turn sends widespread dopaminergic signals back to the spiny neurons. What does this cause?
Excitatory inputs mediated by D1 dopaminergic receptors and Inhibitory inputs mediated by type D2 dopaminergic receptors.
Disorders in which circuit lead to Parkinsons diseas?
What are the three functional subdivisions of the cerebellum?
Vestibulocerebellum, Spinocerebellum and cerebrocerebellum.
What is the spinocerebellum primarily concerned with?
Lateral part movements of distal muscles, such as the relatively gross movements of the limbs in walking. The vermis, is concerned with proxial muscles and regulates eye moevements.
What does the cerebrocerebellum control?
Motor skills associated with speech, hand-eye coordination, independent limb movements.
Where does the vestibulocerebellum recieve inputs from and what does it control?
Inputs from the vestibulat nuclei in the brainstem, muscle spindles, joint afferents in neck. Maintains the stability of the head.
What is a cerebellar peduncle?
A nerve tract that allows coommunication between the cerebellum and other parts of the CNS.
What are the 4 deep cerebellar nuclei?
Fastigial nucleus, interposed nucleus, dentate nucleus and the vestibular nuclei.
What toxins can cause Parkinsons?
Magnesium oxide, MPTP
What do the motor symptoms of Parkinsons result from
Death of dopamine generating cells in the substania nigra.
What other neurotransmitter is affected by the decrease in dopamine?
What are lewy bodies?
Abnormal deposits of protein, they can accumulate in several regions of the brain (esp substania nigra pars compacta). Hallmark of parkinsons.
What does PET stand for?
Positron emission tomography
What is a PET scan?
Nuclear imaging technique producing a 3d image of the body.
How does PET scans work?
A radiactive medicne is produced and tagged to a natural chemical (water, glucose), which becomes a radiotracer. This is inserted into a human and the energy emitted detected and a 3D image is produced.
Give 2 examples of radiotracers
1)18F-fluorodopa - radionuclide intorduced into dopamine
2)18F-fluorodeoxyglucose - radionuclide introduced into glucose.
What is a SPECT?
Single proton emission computed tomography. Uses a gama camra to acquire multiple 2d images from different angles which the computer then converts to 3d. You can then show thin slices along any chosen axis of the body.