Hypothalamus Flashcards
Hypothalamus regulates ___ (5)
- BP and electrolyte balance
- body temp
- energy metabolism
- reproduction
- emergency response
3 Mechanisms
- receives sensory signals from the body (vision, olfaction, somesthetic, visceral, hormonal)
- compares signals with biologically set oints
- Restores homeostasis by – adjusting ANS, endocrine, behavior
Functions (6)
- control release of 8 hormones
- temp regulation
- food/water intake regulation
- sexual behavior, reproduction
5l control daily cycles in physiolodical state and behavior - mediate emotional responses
Adenohypophyseal System (Portal System)
- HT neurons produce releasing or inhibiting factors
- goes to portal system
- adenohypophysis (ant pituitary) produces/stores releasing factors
- peripheral glands produce/release hormones
Neurohypophyseal Systems
- HT produces hormones – go via hypophyseal tract to neurohypophysis (post pituitary)
- regulates blood concentation (ADH)
- oxytocin, vassopressin
HT nuclei – med -> lat
- periventricular
- medial
- lateral
Regulation of Body Fat and Feeding
watches leptin levels - leptin decreases appetite, increases energy expenditure, regulates body mass
-leptin depletion incites adaptive responses to fight starvation
Lateral Nuclear Group
= feeding center
- lesion lateral = starve
- lesion medial = fat
Arcuate nucleus
- reads leptin levels
- activation -> release of anorectic peptides -> decreased apetite (paraventricular nuc stim SNS, release of ACTH)
Decreased Leptin
- arcuate nuc activate PSNS, stimulate feeding
- inhibit ACTH release
phases of eating
- cephalic = food introduced
- gastric = eat it
- substrate = digest
Factors affecting appetite
- Satiety - nuc sol
- gastric distention - vagus
- CCK - hunger suppresant
- insulin
- dopamine - self-stimulatioin
Dopamine and Motivation
- low dope = lack motivation to seek food, but enjoy it when its available
- stim dope = craving for food without increaseing hedonic (like food) impact
Serotonin levels
low - postabsorption
rise - anticipating food
spike - during meals
Drinking motivation
- Hypovolemia - low blood volume
2. Hypertonicity - increased concentration
Volumetric Thirst (triggered by hypovolemia)
- incr angiotensin II to kidney – kidney sends info to subfornical organ (monitors blood volume) – signal to HT
- mechanoreceptors in vessels, heart – vagus – nuc sol, – HT
Osmometric Thirst
- OVLT regulates osmolarity
- OVLT excites lat. HT area and magnocellular neurosecretory cells –> stim osmometric thirst
- diabetes: lack vassopressn –> don’t release enough ADH –> water leaves
Temp reg – areas of HT
- neurons for temp homeostasis in ANTERIOR HT
- humoral/visceromotor response in MEDIAL PREOPTIC AREA
- somatic motor (behavior) responses in LATERAL HT
Temp Reg – decreased temp
- visceromotor - goosebumps
- somatic motor – shiver
- TSH released by ant pit –> stim release of thyroxin from thyroid –> incr cell metabolism
Temp rise
slow metabolism by reducing TSH release
Suprachiasmatic Nucleus
-circadian signals (light/dark cycle)
Pre-optic area
- switch from wakefulness to sleep
- inhibits BS, neurons that maintain arousal
Awake waves
Alpha and beta - low amp high freq
Stage I sleep
light sleep
theta waves
Stage 2 sleep
breathing, HR slows, slight drop body temp
theta waves
Stage 3 sleep
beginning of deep sleep
beginning of delta waves
Stage 4
very deep sleep
delta
Stage 5
REM - ms relax, HR increases, rapid/shallow breathing
beta
REM - hormones
- ACH promotes entry
- Serotonin, NE inhibit
Orexin
chemical used by HT for neurotransmission
-regulates arousal, wakefulness
Narcolepsy
cant regulate sleep-wake cycles regularly
Cataplexy
sudden transient loss of ms tone followed by full concious awareness (70% w narc)
REM - HT
- lateral HT (orexin) inhibits
- preoptic turns on
synchronous
- stage 1-4 - EEG is slower, larger
- high amp, low freq
Desynchronus
- stage 5 REM
- low amp, high freq
- paradoxical sleep - body deeply asleep, EEG looks like waking brain
