neuroendocrinology, key position of hypothalamus

NEUROENDOCRINOLOGY, KEY POSITION OF HYPOTHALAMUS

Olga Vajnerová, 2nd Faculty of Medicine, Charles University, Prague,

2011

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

cingulate gyrusParahippocampal gyrusOrbitofrontal cortex

Anterior nuclei

Hippocampus

Amygdala

Functions of hypothalamus

Functions of hypothalamus

Relation to autonomic function

Parasympathetic responses

Urinary bladder contraction

Sympathetic responses

Increased adrenal medullary secretion

Vasoconstriction

Stress – fight or flight

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

Influence on respiratory and gastointestinal reflexes

Olfactory stimulus – from paleocortex

Signals to visceromotor centres in medulla – nausea, vomiting

Transmission of emotions from limbic system

Rage, anxiety and fear, joy, sadness

Is connected with visceromotor and somatomotor reaction

Hear rate, breathig rate, vasomotor reaction – pale or red skin, sweat glands, gastrointestinal motility and secretion, smooth muscle in skin, shivering

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 center

Lateral hypothalamus

Osmoreceptors – when the EF is too concetrated – develops intense desire to drink water

2. Antidiuretic hormone

Gastrointestinal and feeding regulation

Hunger center

Lateral 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 center

Ventromedial 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 infundibularis

The site where multiple hormones converge to regulate food intake and energy expenditure

Hypothalamus

Receives hormonal signals (from GIT, adipose tissue)

neural signals (from GIT)

chemical signals (from blood about nutrients)

signals from cerebral cortex (sight, smell and taste)

Draw a picture

Orexigenic substances ??

Anorexigenic substances

Orexigenic substances stimulate feeding

Ghrelin

Anorexigenic substances ???

Orexigenic substances stimulate feeding

Ghrelin

Anorexigenic substances inhibit feeding

CCK, insulin, leptin

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

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 receptors

Spinal cord, abdominal viscera and great veins

2. Central

Temperature detectors in hypothalamus

Heat 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

Sweating

Praeoptic area, via autonomic pathways to the spinal cord

Sympathetic but cholinergic

Decrease in heat production

Inhibition of shivering and thermogenesis

Temperature-decreasing

mechanisms

Vasodilation of skin blood vessels

Inhibition of the sympathetic centers in the posterior hypothalamus

Sweating

Praeoptic area, via autonomic pathways to the spinal cord

Sympathetic but cholinergic

Decrease in heat production

Inhibition of shivering and thermogenesis

Temperature-decreasing

mechanisms

Vasodilation of skin blood vessels

Inhibition of the sympathetic centers in the posterior hypothalamus

Sweating

Praeoptic area, via autonomic pathways to the spinal cord

Sympathetic but cholinergic

Decrease in heat

production

Inhibition of shivering

and thermogenesis

What are temperature-increasing mechanisms ??

No Vasodilation of skin blood vessels

NO Sweating

Increase in heat production

Temperature-increasing mechanisms

When the body is too cold

1. Vasoconstriction of skin blood vessels

Stimulation of the sympathetic centers in the posterior hypothalamus

2. Piloerection

via autonomic pathways to the spinal cord

Sympathetic stimulation causes

arrector pili muscles to contract

3. Increase in heat production, thermogenesis

Shivering, 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