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Midterm

PSL300H1 Study Guide - Midterm Guide: Pretectal Area, Pupillary Light Reflex, Reticular Formation

by

Department
Physiology
Course Code
PSL300H1
Professor
Doug Mac Kay
Study Guide
Midterm

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REFLEXES AUTONOMIC
retinal ganglion cells contain absorbing pigment called melanopsin
(light absorbing pigment, depolarizes with light detecting general light levels)
also important for sychronizing circadian rhythms w/ day-night cycle. pupillary light reflex
**PUPILLARY LIGHT REFLEX: ON FINAL.
does NOT begin in same area as parasympathetic. organized in the pretectal area of midbrain
uses ON and OFF afferents to detect luminance and darkness, in olivary pretectal nucleus :
melanopsin detects light sends signals to pretectoral area in midbrain retinal ganglion cells detect light or dark info
prcessed in pretectual nucleus in the brain.
when too bright parasympathetic activated: reflex via 3rd cranial nerve to ciliary ganglion and circular iris muscles.
uses ACh for pupillary constriction.
when too dark sympathetic activated: reflex via thoracic cord, sympathetic chain to radial muscles. (uses NA for
pupillary dilation). cocaine can inhibit NA reuptake, causing eyes to stay dilated.
Central control of the ANS:
reticular formation: most direct influence over autonomic function sends signal to spinal cord.
hypothalamus: main integration center integrates diff signals. processes many types of things.
amygdala: main limbic region for emotions stimulates sympathetic activity, especially previously learned fear-relating
behaviour. can be voluntary when decide to recall a frightful experience, cerebral cortex acts through amygdala. some ppl
can regulate autonomic activities by gaining extraordinary control over their emotions.
AUTONOMIC CENTERS IN BRAIN
brainstem autonomic centers:
sympathetic modulatory tracts from raphé nuclei and locus coeruleus.
cardiovascular center, and respiratory pattern generator in lateral medulla/pons
periaqueductal gray: midbrain promoter center, for autonomic behavioural programs.
Reticular activating systems: diffuse collection of nuclei in brainstem. modulatory (cause global shift in CNS activity,
mainly metabotropic):
cholinergic: determines levels of attn. sleep-wake cycle, mainly ascending (pontine reticular formation and BNM nuclei)
serotonergic: stress situations, influences mood, sleep-wake cycle. too much serotonin aggression. 
adrenergic: for stressful situations and vigilance
serotonergic and adrenergic produce strong motor effects.
Histaminergic system: origins = posterior hypothalamus, TBN (tuberomamillary nucleus) specifically. projects
through forebrain and to other activating systems in brainstem.-> ascending and descending. important for sleep/wake
cycle. systems turns off when you fall asleep. histamine lvl decreases.
Autonomic Pattern Generators: CPGs controlling autonomic behaviors located in brainstem.
PAG in midbrain = major organizing center. most of these functions related to homeostatis.
Hypothalamic control centers:
NTS - info abt bloos pressure and gut distention (homeostatis)
Reticular formation - from CN X, info abt skin temperature, relayed to hypothalamus.
Retina - some fibers from optic nerve go directly to smallnucleus within hypothalamus called superchiasmatic nucleus,
which relates circadian rhythms, and couples them to light/dark cycles. (through melanopsin)
limbic and olfactory systems - regulates behaviour such as eating and reproduction.
temperature regulation: if skin temprature diff from body temp, info relayed from skin detecting changes in enviro.
thermoreceptors at base of hypothalamus, also detect enviro changes. warm-sensitive neurons outnumber cold-sensitive
neurons in brain, ultimately control thermogenesis.
when too cold skin vasoconstricts, piloerection, decreased circadian output, shift of fluid out of plasma , shivering -- a
somatomotor effect) posterior hypothalamus. need NA adrenergic input.
when too hot skin vasodilates, sweats, increased cardiac output, shift of fluid into plasma from extra-cellular space, ADH
released to prevent loss of fluid through urination. anterior hypothalamus. need serotonin serotenergic input
Cardiovascular center:
mainly in ventrolateral medulla, beside respiratory center.
NTS receives input from baroreceptors and cends this info to caudal VLM. rostral half excites sympathetic efferents
raises blood pressure and heart rate (pressure function). 
caudal half INHIBITS rostral hald blood pressure drops.
baroreflex: baroreceptors n. solitary tract ventro. lateral medulla sympathetic output (activate/inactivate)
Hypothalamic control of homeostatis:
hypothalamus = major regulator of core parameters (glucose in plasma, osmolality, temp regulation)
sensors located in hypothalamus to detect changes. corrective actions take place when detected, via autonomic endocrine
and somatomotor mechanisms. 
interacts with brainstem motor and autonomic centers via axonal projections.
interacts with endocrine system via pituitary
REGULATION OF FEEDING ****
in hypothalamus:
arcuate nucleus control: NPY neurons drive feeding via paraventricular nucleus., other neurons (melanocortin) are
antagonistic (suppress feeding).
ventromedial nucleus: glucoreceptors, discharge in relation to ambient glucose lvls, inhibit NPY-mediated drive to feeding
behaviours. glucose = NPY inhibition. 
leptin, secreted by white adipose tissue (fat), long term suppression of feeding, inhibiting NPY-containing neurons in
arcuate nucleus.
G.I tract to control feeding ghrelin from empty stomach promotes feeding (orexigenic hormone)
PPY release in intestine in response to food and insulin from pancreas, inhibiting feeding. borborygmus (release of ghrelin,
stomach growls)
Amygdala part of B.G., controls autonomic behav. input from limbic cortex, output generally inhibitory on PAG-
hypothalaumus (shutting down a lot of programs). lesions = uncontrolled autonomic behav. (sham rage, hypersexuality,
etc)
Emotion related behaviour memories related to emotional experiences (especially fearful, rely on amygdala for
consolidation)
amygdala is not a site of memory storage. 
Limbic cortex: border region of cerebral cortex. made up of cingulate gyrus, hippocampal region (consolidates memories)
+insula.
subserves emotional experience, motivation and memory consolidation.
neurons from this region project to hypothalamus, PAG and amygdala.
retinal ganglion cells
melanopsin
pupillary light reflex
olivary pretectal
nucleus
pretectal area of
midbrain
circular muscles
radial muscles
amygdala
periaqueductal gray
reticular activating
systems
histaminergic
TBN
autonomic pattern
generator
NTS
retina
superchiasmatic
nucleus
cadiovascualr center
homeostatis
paraventricula
nucleus
arcuate nucleus
ventromedial nucleus
ghrelin
orexigenic hormone
ANS AND ANS REFLEXES pt.2
June-04-132:01 PM
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