Midterm Review HMB200.docx

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Human Biology
Ingrid L.Stefanovic

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 stimulus: - 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 called tau. Histamine neurons are found in the posterior hypothalamus. Matching 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) Deepest layers of S.C - Avoidance Turns Dorsolateral PAG - Fighting Responses (defense threat + defense attack) Lateral PAG - Flight Responses (+ non opiate analgesia) Ventrolateral PAG - Freezing Response (+opiate analgesia and lordosis in females via estrogen receptors) Definitions: Melanopsin: Found only in the retinoganglian cells that project to the SCN and intergeniculate nuclus (IGN) via the retinohypothalamic path in mammals and surrounding the pineal gland in birds. It is an opsin that detects light, but is much less sensitive then rhodopsin and needs a lot of light averaged over a long time to detect light. The ganglian cells containing the melanopsin have huge receptive fields and do not adapt to light, they are also involved in pupillary reflex. Melanopsin has an important function in the cirdacian rhythm, entraining the internal clocks found inside the SCN. REM sleep REM sleep is a type of sleep that involves rapid eye movement, atonia (muscular paralysis) and active brain involving high frequency waves (Beta/Gamma and Alpha). Starts about an hour after sleep, and you have 4-5 REM sleep cycles in a normal sleep, with REM phases becoming longer toward the morning. At the onset of REM Cholinergic systems are active whereas NOREPI and Serotonin are quiet. REM sleep is important for mental recovery, and this is where you see dreams. Also called paradoxical sleep. Enkaphalin Is a small endogenous opiate released my many brain ar
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