Sleep, hunger, thirst, emotion

• Sleep


  function of sleep

  • body; energy conservation, muscle and immune system repair
  • brain; adenosine clearance, memory consolidation, reorganization, REM
• Rhythms

  • many actions have to be rhythmical
  • heartbeat, walking, breathing
  • many diff scales
  • diff brain mechanisms for generating these rhythms
  • simple pattern generator neurons (for fast rhythms)
  • hormonal fluctuations (for long-term rhythms)
• The wakefulness pathway

  • Light enters eyes
  • strikes intrinsically photosensitive ganglion cells (ipRCG), which express melanopsin
  • project directly to suprachiasmatic nucleus (SCN)
  • periventricular nuclei of the thalamus
  • down spinal cord
  • superior cervical region
  • back up pineal gland
  • releases melatonin
  • hormone that affects waking

  
• seeing the light


  Melatonin causes sleepiness

  • mostly released in the few hours before sleep
  • the wakefulness pathway is inhibited by light

  cells of the SCN are rhythm generators

  • can continue to generate a rhythm even in vitro
  • molecular mechanism
  • PER and TIM genes
• Individual differences 


  Different individuals' SCN and pineal are more active at diff time

  • melatonin production varies with age
  • younger adults usually more alter later in day
  • older adults usually more alert in the morning
  • individuals' differences peak alertness times
  • 'larks' and 'night owls'
  • activity cycles can change circadian rhythm
  • night shift workers have suppressed melatonin production
  • jetlag
• Stages of sleep

  • 5 diff types of sleep
  • normal sleep alternates between them approx. every 90 mins
  • stage 1
  • shallow sleep
  • EEG; very little activity
  • stage 2
  • shallow sleep
  • EEG; erratic
  • stages 3 and 4
  • deep sleep
  • EEG; large, slow waves
• REM (paradoxical sleep)

  • EEG activity irregular, low amplitude
  • large, rapid eye movement back and forth
  • paradoxical bc
  • lots of brain activity
  • body relaxed, muscles paralyzed
  • PGO waves (pons, geniculate, occipital)
  • REM is important
  • dreams occur
  • sleep deprivation leads to increase in REM
  • REM deprivation leads to increases in REM
  • PGO-like waves during waking (and hallucinations)
• Pathways of sleep and arousal

  • sleep is mostly a function of GABA release
  • sleep is modulated all over brain
  • sleep can be localized to only part of the brain
• Dreams

  • brain trying to make sense of day's info
  • brain lacking for other stimulation
• Internal regulation

  -body needs to maintain certain levels of chemicals

  • body requires glucose at a certain minimal rate
  • blood concentration and volume require water
  • parts of body need to be rebuilt, which requires raw material

  -mechanisms controlling substance intake (eating, drinking) mostly depends on hormones and neuropeptides

  • hypothalamus; regulates hormone release
• Water

  • concentration of the blood and volume of blood (blood pressure) must be kept within a narrow range
  • brain regulates water intake by thirst
  • two kinds:
  • osmotic thirst
  • consuming salty food increases the concentration of blood
  • drink water to reduce the concentration
  • hypovolemic thirst
  • sweating, bleeding, vomiting reduces volume of liquid in body
  • drink/eat salty things to increase volume but maintain concentration
• Mechanisms of thirst


  When decreased water volume is detected

  • brain releases vasopressin
  • contracts blood vessels, increases BP
  • reabsorbs liquid from urine
  • body releases angiotensin II
  • detected by neurons around third ventricle, which projects to hypothalamus, makes u drink

  when blood concentration increases

  • concentration of salts outside cells increases, cells lose water
  • neurons in OVLT, SFO detect loss of water
  • hypothalamus makes u drink
• You are what you eat

  • need to eat things our body needs for energy, repair, chemical balance, growth
  • brain needs to control
  • what we eat
  • when we eat
  • several diff mechanism for safety
  • foods may contain chemicals that affect brain
  • tryptophan, beta-adrenergic blockers, caffeine
  • current diet is not natural
• Brain mechanisms of eating 


  how much to eat:

  • stomach distension
  • full stomach stimulated vagus nerve (cranial nerve #10), affects hypothalamus
  • rich foods five more calories/weight
  • food in duodenum
  • releases CCK, stimulated vagus nerve, hypothalamus
  • more CCK u have, the less hungry you'll be
  • oral mechanisms (amount of chewing)
• When to eat, when to stop eating

  -Extraction of glucose has 2 stages

  • eating, digesting, storing excess as fat
  • entrance of glucose into cells
  • mediated by insulin levels

  -leptin

  • longer-term monitoring of fat levels
  • high levels indicate satiety, reduce eating
  • desensitization of hypothalamus to leptin contributes to obesity
• Hypothalamus and hunger


  -Hypothalamus receives lots of input from and body

  • Ghrelin: hormone indicating hunger (increasing appetite)
  • Leptin, insulin, CCK

  -signals go to the periventricular nucleus (PVN)

  • hunger inhibits PVN; satiety activates it

  -PVN projects to lateral hypothalamus

  • releases orexin which increases hunger and arousal
  • modulates digestion, insulin levels, taste sensitivity
  • hunger is the best flavouring bc of lateral hypothalamus (good will taste even more good, bad will taste more bad when hungry)
• Emotions


  -What is emotion (affect)?

  • three parts
  • cognition; evaluating the situation
  • feeling; happy, sad, angry
  • action; run away, attack, cry
  • the brain makes unconscious decisions about the situation
  • quickly, automatically
  • using heuristics; simple rules; not considering all info
  • emotions causes u to want to act (motion) or inhibit action
• Evolutionary aspects


  -reacting quickly is important

  • more important than considering all info
  • some situations are complex; emotions give the simple answer
• Specificity of action


  -Emotions motivate the action that is usually appropriate to the situation

  • fear-> run away, anger-> attack, happy-> smile, disgusted-> make a face
• Which emotions?


  -which things count as emotions?

  • 6 basic emotions; happy, sad, anger, fear, disgust, surprise
  • can combine into compound emotions
  • measured on 2 axes:
  • valence (positive or negative)
  • arousal (intensity; strong, weak)
• Creating emotion


  -emotional responses activate the peripheral nervous system

  • sympathetic; fight or flight
  • parasympathetic; rest and digest
• James-Lange theory 


  -Emotional timeline:

  • brain evaluates situation, decides on best response
  • peripheral system gear up for a response (preparing for action)
  • sensing peripheral activation causes feeling

  -response preceded feeling

  -experimental evidence

  • forcing the response can increase the emotion
  • preventing the response can limit emotion
  • damage to body can limit affect
• Where in the brain


  -No one has found an area where emotions are created, processed, control

  • occur all over brain
  • no clear correlation between valence or arousal and a particular region

  -the insula in involved in disgust

  • also contains primary gustatory cortex

  -possibly diff emotions in the two hemispheres
• Fight or Flight


  -Activation of sympathetic nervous system

  • anger, fear

  -anger:

  • some generic effects, interact with environmental factors
  • some of the mechanisms are hormonal
  • slower, longer-lasting response
  • triple imbalance theory of anger
• Triple imbalance


  -Testosterone

  • leads to aggression

  -cortisol

  • released by stress
  • increases fear and inhibition
  • reduction leads to aggression

  -serotonin

  • high levels inhibit aggression
  • also inhibits other behaviour
• Serotonin 


  -Made from tryptophan

  • tryptophan enters the brain through active transport
  • other amino acids can compete for space on the transporter
• Fear


  -no clear location in brain but closely related to amygdala

  • involved in: fear response, learning to fear things, directing attention to surprising/ scary stimuli

  -toxoplasmosis

  • can infect humans, not dangerous expect for compromised immune systems or fetuses
• Stress


  -response of the body to any threat; external dangers, disease, injury

  -3 stages (selye):

  • alarm
  • initial emotion (fear, anger)
  • activation of the SNS
  • short lived
  • resistance
  • long term rise in immune activity
  • Sympathetic system stands down
  • lots of cortisol
  • exhaustion
  • after a long time in resistance
  • nervous and immune systems crash
• Physiology of stress


  -activation of the HPA axis

  • hypothalamus release CRH
  • pituitary releases ACTH
  • locus coeruleus (in pons) release norepinephrine
  • adrenal glands release cortisol
  • increase/decrease immune function
  • increases available glucose (reduces fat reserves)
  • improves/impairs memory
  • reduces protein synthesis
  • complex relationship, still not understood
• Evolution of stress


  -why would we need this response?

  • for external threats
  • dangers some in groups
  • being primed increases speed of response
  • for disease
  • combatting disease requires that the body not interfere
  • body has limited resources and must prioritize
  • external threats are usually more immediate, activation of SNS inhibits immune response
  • disease responses reduce body activity
• Anxiolytic drugs 


  -amygdala projects to

  • hypothalamus which mediates physiological response to fear
  • inhibited by GABA

  -increasing GABA activity everywhere decreases fear activation

  • benzodiazepines (Valium,Xanax, lactium) bing to one subunit of GABAa receptors and sensitize them
  • alcohol increase GABA and is anxiolytic