HMB200H1 Study Guide - Midterm Guide: Saccade, Deep Brain Stimulation, Circadian Rhythm
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Midterm Review HMB200
The cause of narcolepsy/cataplexy in humans appears to be due to the gradual loss of orexin/hypocretin
neurons. These neurons are located in the lateral hypothalamus.
Circadian rhythms in mammals are controlled by a negative feedback loop in which two proteins, per
and cry combine (dimerize) to inhibit the gene transcription factors Clock and Cycle
Amphetamine acts on dopamine neurons in two ways: block dopamine transporters in the nucleus
accumbens causing less reuptake, and stimulating dopamine release at the VTA.
3 sensory systems that activate a fast startle reflex are : tectal, auditory, and vestibular stimuli sensing
slap on the skin (trigeminal CN 5) , bone conducted auditory stimuli (vestibulocochlear CN8) , and a head
acceleration via vestibular apparatus (vestibulocochlear CN8).
Mauthner (M) cells are found in the medulla of fish and tadpoles and serve to evoke a fast escape
response (C reflex).
The rubrospinal tracts begins in the red nucleus then descends to the spinal cord in the lateral column.
Inputs to the red nucleus come mainly from the cerebellum and motor cortex.
3 ways of treating Parkinson’s disease: Ingesting the precursor L-Dopa, transplanting dopamine neurons,
and Deep brain stimulation.
List 2 ways that startle can be potentiated by events or genetic conditions that precede the startle
- You can cause a startle reflex by a blow to the head, or a loud acoustic stimuli
- Mutation in one glycine receptor leads to hyperekplexia which causes a spasmodic startle
response due to the loss of inhibitory control by the glycine alpha receptor.
Short period circadian rhythms results from mutation in homologous genes for an enzyme in fruit flies,
hamsters and humans.
- The enzyme is called caseine kinase, the fruit fly mutant is called dbt, The hamster mutant is
Histamine neurons are found in the posterior hypothalamus.
Upper layers of superior colliculus
- visual inputs for saccades (scd. Eye mvmnt doesn’t happen here)
Middle layers of S.C
- Approach turns (and saccadic eye movement)
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