neuroendocrinology, key position of hypothalamus olga vajnerová, 2nd faculty of medicine, charles...
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NEUROENDOCRINOLOGY, KEY POSITION OF HYPOTHALAMUS
Olga Vajnerová, 2nd Faculty of Medicine, Charles University, Prague, 2011
Ascending arousal system
Frederic Bremer (30. years of 20. century)
Cerveau isolé (intercollicular midbrain transection between colliculi superiores and inferiores)
uncosciouness, EEG of sleep type
Encephal isolé (transection at C1)
Sleep and wakefulness alternate
Excitatory-activating system of the brain
Pyramidový neuron
Thalamocortical modulation
Neurohormonal control of brain activity
The locus ceruleus and norepinephrine system
Excitatory effects
Modulatory effects (raise the excitability level of the cell and make it more likely to fire AP)
REM sleep
Neurohormonal control of brain activity
The substantia nigra and the dopamin
Nigrostriatal system to caudate and putamen
Either excitation or inhibition
Destruction:
Parkinson‘s disease
Neurohormonal control of brain activity
The substantia nigra and the dopamin
Ventral tegmental nucleus to the frontal lobe, ventral striatum, amygdala, other limbic structures
Excessive activity:
schizophrenia
Neurohormonal control of brain activityThe raphe nuclei and the serotonin system
Fibers to thalamus, cortex
Descend to the spinal cord
inhibitory
Non REM sleep
Supress pain
Hypothalamus, a major control headquarters for the limbic system
Hypothalamus, a major control headquarters for the limbic system
Hypothalamus Cortex
Thalamus Temporal lobe Basal ganglia Septum Paraolfactory
area
Hypothalamus, a major control headquarters for the limbic system
Hypothalamus Cortex
Thalamus Temporal lobe Basal ganglia Septum Paraolfactory
area
cingulate gyrusParahippocampal gyrusOrbitofrontal cortex
Hypothalamus, a major control headquarters for the limbic system
Hypothalamus Cortex
Thalamus Temporal lobe Basal ganglia Septum Paraolfactory
area
cingulate gyrusParahippocampal gyrusOrbitofrontal cortex
Anterior nuclei
Hypothalamus, a major control headquarters for the limbic system
Hypothalamus Cortex
Thalamus Temporal lobe Basal ganglia Septum Paraolfactory
area
Cortex:cingulate gyrusParahippocampal gyrusOrbitofrontal cortexSubcallosal gyrus
Anterior nuclei
Hippocampus
Amygdala
Functions of hypothalamus
Functions of hypothalamus
Connections:
Caudally to the brain stem
Rostrally to diencephalon
limbic cortex
Pituitary gland
Hypothalamus controls:
1. Vegetative and endocrine functions
2. Behavior and motivation
Functions of hypothalamus
Olga Vajnerováusing Mital Patel presentation
Vegetative and endocrine functions
Hypothalamic hormones Adenohypophysis
Feed back regulation
Kortizol
Tyroxin
Hypothalamic hormones Neurohypophysis
QUESTION
PATIENT : EXTREME THIRST EXCESSIVE DILUTED URINATION DAY AND
NIGHT DEHYDRATION
WHATS THE DIAGNOSIS?
QUESTION
PATIENT : EXTREME THIRST EXCESSIVE DILUTED URINATION DAY AND
NIGHT DEHYDRATION
WHATS THE DIAGNOSIS?
DIABETES INSIPIDUS
ADH DEFICIENCY
Cardiovascular regulation
Arterial pressure
Heart rate
Specific cardiovascular control centres are in….
Reticular regions of the pons and medulla
Cardioexcitatory area
Cardioinhibitory area
Vasomotor area
Via Sympathetic and Parasympathetic nerves
Posterior and lateral hypothalamus increases
Preoptic area decreases
Biological rhythms
Suprachiasmaticus nuclei – retinohypothalamic tract
Pacemaker of circadian rhythms
Sleep – wake cycle
ACTH secretion
Melatonin secretion
Body temperature rhythm
Activity patterns of animals
Regulation of body water
1. Thirst centerLateral hypothalamus
Osmoreceptors – when the EF is too concetrated – develops intense desire to drink water
2. Antidiuretic hormone
Gastrointestinal and feeding regulation
Hunger centerLateral nuclei of the hypothalamus
stimulation – extreme hunger, appetite,
craving for food, hyperphagia
Destruction of this area – lethal starvation, weight loss, muscle weakness, decreased metabolism
Is permanently active
Satiety centerVentromedial nuclei of the hypothalamus
Stimulation – sense of complete satiety, refusal of food, aphagia
Destruction – hunger centers overactive, continuing eating, obesity
Other important nuclei in feeding regulation
Paraventricular, dorsomedial and arcuate nuclei of the hypothalamus
ncl arcuatus = ncl infundibularisThe site where multiple hormones converge to regulate food intake and energy expenditure
HypothalamusReceives hormonal signals (from GIT, adipose tissue)
neural signals (from GIT)
chemical signals (from blood about nutrients)
signals from cerebral cortex (sight, smell and taste)
Feedback mechanisms for control of food intake
Stretch receptors in the stomach
PYY
Cholecystokinin
Insulin
Leptin
Supress futher feeding
Ghrelin – during fasting
Stimulates apetite
Short-term regulation of food intake
- gastrointestnal filling- GIT hormonal factors – CCK, insulin, ghrelin
- oral receptors meter food intake
Oral factors related to feeding
such as chewing, salivation, swallowing, tasting
Intermediate and long-term regulation of food intake
- concentration of glucose, amino acids, and lipids
glucostatic theory of hunger and feeding regulation(rise in blood glucose level increases firing of neurons in the satiety center, decrease in hunger center
- Temperature regulation and food intake
Cold increased feeding
Interaction between temperature-regulating systém and food intake-regulating systém
- Feedback signals from adipose tissue - leptin
Orexigenic substances stimulate feeding
Ghrelin
Anorexigenic substances inhibit feeding
CCK, insulin, leptin, PYY
Regulation of body temperature
Temperature regulating centers
Temperature receptors
Regulation of body temperature
Temperature regulating centers
Temperature receptors
1. Peripheral
Skin receptors (cold and warm)
Deep body temperature receptorsSpinal cord, abdominal viscera and great veins
2. Central
Temperature detectors in hypothalamusHeat sensitive neurons, cold sensitiv neurons
Praeoptic area
Posterior hypothalamus integrates the central and peripheral temperature sensory signals
Control Heat-producing
Heat- conserving reaction of the body
Set point – crucial temperature level 37.1ºC
Feedback gain for body temperature control
Temperature-decreasing mechanisms
Vasodilation of skin blood vessels
Inhibition of the sympathetic centers in the posterior hypothalamus
SweatingPraeoptic area, via autonomic pathways to the spinal cord
Sympathetic but cholinergic
Decrease in heat productionInhibition of shivering and thermogenesis
Temperature-decreasing
mechanisms
Vasodilation of skin blood vessels
Inhibition of the sympathetic centers in the posterior hypothalamus
SweatingPraeoptic area, via autonomic pathways to the spinal cord
Sympathetic but cholinergic
Decrease in heat productionInhibition of shivering and thermogenesis
Temperature-decreasing
mechanisms
Vasodilation of skin blood vessels
Inhibition of the sympathetic centers in the posterior hypothalamus
SweatingPraeoptic area, via autonomic pathways to the spinal cord
Sympathetic but cholinergic
Decrease in heat
productionInhibition of shivering
and thermogenesis
What are temperature-increasing mechanisms ??
No Vasodilation of skin blood vessels
NO Sweating
Increase in heat production
Temperature-increasing mechanismsWhen the body is too cold
1. Vasoconstriction of skin blood vessels
Stimulation of the sympathetic centers in the posterior hypothalamus
2. Piloerectionvia autonomic pathways to the spinal cord
Sympathetic stimulation causes
arrector pili muscles to contract
3. Increase in heat production, thermogenesisShivering, sympathetic excitation of heat production,
Thyroxin secretion
3. Increase in heat production, thermogenesis
ShiveringPrimary motor center for shivering in the dorsomedial portion of the posterior hypothalamusExcited by cold signals from the skin and spinal cordTr hypothalamoreticularis, hypothalamospinalis to spinal motoneuronsNon rhytmical signals, increase the tone of the skeletal musclesProbably feedback oscillation of the muscle spindle stretch reflex
Sympathetic excitation of heat productionChemical thermogenesis, E and NE uncouple oxidative phosphorylation, energy in the form of heat but do not cause ATP to be formed
Thyroxin secretion
Sympathetic excitation of heat productionChemical thermogenesis, E and NE uncouple oxidative phosphorylation, energy in the form of heat but do not cause ATP to be formed
Thyroxin secretion
Transmission of emotions from limbic system
Rage, anxiety and fear, joy, sadness
Is connected with visceromotor and somatomotor reaction
Heart rate, breathig rate, vasomotor reaction – pale or red skin, sweat glands, gastrointestinal motility and secretion, smooth muscle in skin, shivering
Influence on respiratory and gastointestinal reflexes
Olfactory stimulus – from paleocortex
Signals to visceromotor centres in medulla – nausea, vomiting
Relation to autonomic function
Parasympathetic responses
Urinary bladder contraction
Sympathetic responses
Increased adrenal medullary secretion
Vasoconstriction
Stress – fight or flight
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