autonomic nervous system department of human … autonomi… · autonomic nervous system...

Hpothalamus

AUTONOMIC NERVOUS SYSTEM

Department of human Physiology UPJS MF

Prof. Viliam Donic and Doc. Pavol Svorc

Distant teaching

6th week summer semester 2020

Autonomic nervous system – autonomic centers

The centers of the autonomic nervous system are seen as integrators of responses

to the internal and external facts, which are related to the control of autonomic

functions.

- of spinal cord - although all sympathetic and sacral parasympathetic fibers are

going out from spinal cord, it is not clear whether there are centers controlling and

coordinating the activities of the relevant part of the autonomic nervous system, or

they are only peripheral centers.

From this point of view, it is problematic inclusion:

- of cortex - which is involved in the control of autonomic functions, whose

importance is in the integration and the creation of conditioned reflexes associated

with the autonomic nerves.


Is taken into account brainstem and hypothalamus.

Reticular formation - is responsible for regulation of the cardiovascular system,

respiratory system and is the center of some autonomic reflexes.

Cardiovascular center includes the following structures:

- ncl. dorsalis n.vagi – source of vagal parasympathetic afferentation

- pressoric area – is located on both sides in the dorsolateral part of reticular

formation. Increased activity leads to an increase in blood pressure. Sympathetic

preganglionic neurons innervating heart, blood vessels and juxtaglomerular

apparatus are efferent pathways from this center.

- depressoric area - is located in the ventromedial part of both sides of reticular

formation. Increased activity leads to decrease of blood pressure and, reciprocally, it

is connected with pressoric area.


Respiratory center - is functionally situated into autonomic centers,

because it affects the spinal motor neurons controlling breathing

movements through the autonomic respiratory rhythm generator and

inspiration rhythm.

Autonomic reflexes - associated with input and processing of food. It is a

sucking reflex, swallowing, salivatory reflex, secretion of gastric and

pancreatic juices and vomiting reflex.


Sensory information from the somatosensory and visceral receptors goes

to the centers for homeostasis in the hypothalamus, in the pons and in the

medulla oblongata.

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pregangliové

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Nuclei of the hypothalamus

Paraventricular nucleus

(Water balance/stress)Lateral

hypothalamic

area

Dorsal

hypothalamic

area

Posterior

hypothalamic

area

(Shivering)

Dorsomedial

nucleus

(GI tract)

Ventromedial

nucleus

(Satiety)

Mammilary

body

(Feeding)

Suprachiasmatic

nuclei

(Biological Clock)

Posterior

pituitary

glandAnterior

pituitary

gland

Optic chiasm

Optic nerve

Supraoptic

nucleus

(Water balance)

Anterior

hypothalamic area

(Body temperature)

Medial preoptic

(Blood pressure)

Autonomic nervous system – hypothalamus

ANTERIOR HYPOTHALAMUS

Preoptic preoptic nucleus thermogegulation

Medial medial preoptic nucleus regulates the release of gonadotropic

hormones from the adenohypophysis

Contains the sexually dimorphic nucleus,

which releases GnRH, differential

development between sexes is based upon

in utero testosterone levels

thermoregulation

supraoptic nucleus vasopressin, oxytocin releasing

paraventricular nucleus thyrotropin-releasing hormone,

corticotropin releasing hormone, oxytocin,

vasopressin, somatostatin

anterior hypothalamic nucleus thermoregulation, panting, sweating,

thyrotropin inhibition

suprachiasmatic nuclei circadian rhythm

Lateral lateral nucleus primary source of orexin neurons that

project throughout the brain and spinal

cord

Autonomic nervous system – hypothalamus

TUBERAL HYPOTHALAMUS

Medial dorsomedial preoptic nucleus blood pressure, heart rate, GI stimulation

ventromedial nucleus satiety, neuroendocrinne control

arcuate nucleus growth releaing hormone, feeding,

dopamine mediated prolactin inhibition

Lateral lateral nucleus primary source of orexin neurons that


cord

POSTERIOR HYPOTHALAMUS

Medial mammilary nuclei memory

posterior nucleus increase blood pressure, pupilary

dilation, shivering, vasopressin release

lateral nucleus primary source of orexin neurons that


cord

Lateral tuberomammillary nucleus arousal (wakefulness and attention),

feeding and energy balance, learning,

memory, sleep

Autonomic nervous system – functions of hypothalamus

Hunger is a feeling (unconditioned reaction of the body), caused by lack of food. It

is an important signal, saying to the body about the need for food intake and

energy from it.

Center of hunger and satiety


Center of hunger and satiety

Satiety center is located in the hypothalamus, near the regulatory centers for

secretion of hormones and endocrine processes in our body. Center of hunger is

located near at the center of satiety.

Signals for center of satiety

- stretching of stomach and intestines

- increased external and internal temperature

- glucose, amino acids, fatty acids

- dopamine

- intestinal peptide PYY

- peptides released from the digestive tract (cholecystokinin, bombesin, glucagon,

enterostatin, somatostatin)

- leptin

- ghrelin

- insulin

Center of hunger Center of satiety

ncl. lateralis ncl. ventromedialis

- is continuously active

increase in plasma glucose levels


- lesion of ncl.ventromedialis

leads to hyperphagia- stimulation of the lateral hypothalamus leads to

increase in eating-oriented behavior (looking for

food)

activates glucoreceptors

located in

ncl.ventromedialis

Control of food intake


It is assumed that the information from

the periphery (sensory inputs from the

digestive tract, including gustatory

afferentation) are guided into

ncl.arcuatus in

hypothalamus

lateral part of

hypothalamusncl.paraventricularis ncl.dorsomedialis

projections

into

All of these structures contain two types of neurons:

- orexigenic neurons - synthesize substances, which higher levels correlate with increased

income of food and activate ncl.ventromedialis

- anorexigenic neurons – synthesize substances, which higher levels correlate with reduced

intake of food



Neurons releasing amphetamine (CART) and

proopiomelanocortin (POMC)

Neurons releasing agoutin-related protein

(AgRP), neuropeptide Y (NPY) and γ-

aminobutyric acid (GABA)

Important for the regulation of body weight



Ghrelin is "hunger hormone".

Ghrelin is a peptide hormone produced by

ghrelinergic cells in the gastrointestinal

tract which functions as a neuropeptid in

the CNS.

Ghrelin regulates appetite, and also

distributiom and rate of use of energy.

When the stomach is empty, ghrelin is

absorbed. When the stomach is stretched,

secretion stops.

Ghrelin acts on hypothalamic brain cells and

increases not only hunger, but also

increases gastric acid secretion and

gastrointestinal motility to prepare the body

for food intake.



Leptin is “the hormone of energy

expenditure“.

Leptin is a hormone predominantly made by

adipose cells that helps to regulate energy

balance by inhibiting hunger.

Leptin is opposed by the actions of the

hormone ghrelin, the "hunger hormone".

Leptin and ghrelin act on receptors in the

arcuate nucleus of the hypothalamus to

regulate appetite to achieve energy

homeostasis.

In obesity, similar to resistance of insulin in

type 2 diabetes , a decreased sensitivity to

leptin occurs, resulting in an inability to

detect satiety despite high energy stores and

high levels of leptin.

Center of thirst


Thirst is the body's response to lack of fluids.

We have two types of dehydrations:

One lies in the fact that man has shortage of water (mostly in well-trained athletes who

secrete thin "water" sweat). In this case, the blood is concentrated, but only briefly,

since immediately water from the intercellular spaces starts to flow into blood

resulting in increase the salt concentration in the extracellular fluid. For compensation

of this concentration with concentration in cells, water from cells moves into the

intercellular spaces and thus results in their partial dehydration.

A second type of dehydration of the body is that the person loses not only water but

also a large amount of salts (untrained athletes secrete dense "salty" sweat), which

are mainly in the blood and in the extracellular fluids. This usually results in only a

slight increase in the concentration of ions (salts) in the extracellular fluid. At this type

of dehydration, water content remains stable in the cells, but the amount of circulating

blood and intercellular fluid are reduced.

Center of thirst


Nc.paraventricularis - in this center are the cells that are in the contact with the blood flow and

cerebrospinal fluid and respond either by calling thirst or vice versa calling the urge to urinate.

Stimulus Osmoreceptors - increase of

osmotically active substances

(electrolytes - cations and anions)

in ECF.

Baroreceptors - decrease in

plasma volume. If the body fluid

deficiency there is, the pressure

in the veins is small and blood is

too "dense".

Renin - angiotensin system - at

the decreased plasma volume,

greater concentrations of

angiotensin II raise blood

pressure and causes a feeling of

thirst.

Psychological and social factors

The stimulus for thirst and thus for fluid intake is stimulation

of the mucous cells in the mouth and throat by the partial

dehydration of the cells (the stimulation can also sometimes

come from other causes, such as a cold, considerable moisture,

for example, after eating of ice cream).

Dry mouth can be result of using by certain drugs (e.g. drugs

for allergy), or can be due to insufficient production of saliva

(e.g. in disease called xerostomia), increases thirst.

In older people, generally, centre of thirst failures. Older

people do not feel thirst and they have to regulate the fluid

intake themselves.

Control of the body temperature

anterior hypothalamus posterior hypothalamus

- output of heat

hypothermia

- production of heat

hyperthermia


THERMOREGULATION – mechanisms of thermoregulation

HYPOTHALAMUS

centrum of thermoregulation

receives the informations about the central and

peripheral temperature and also about the temperature

of the environment

Central thermal

receptors

Peripheral thermal

receptors

- they are in the anterior

hypothalamus in the preoptic area

- the are sensitive for the higher

temperatures

- approximately 1/3 from the

total amount of the central

thermosensitive neurons reacts

for the decrease of the body

temperature

Cold receptors Warm receptors

THERMOREGULATION – nervous control

ncl. dorsalis

ncl. ventromedialis

ncl. paraventricularis

lamina terminalis

ncl. supraopticus

chiasma opticum

portal vessels

NEUROHYPOPHYSIS

ADENOHYPOPHYSIS

AREA

HYPOTHALAMICA

POSTERIOR

AREA

PREOPTICA

PREOPTIC AREA

AREA HYPOTHALAMICA

POSTERIOR

- it is responsible for monitoring of

the body temperature and also for

the reactions at the increase of

temperature

- at the injury of this area, we can

see the extreme increase of

temperature

- neurons don’t directly monitore

the body temperature, but they

react to the informations from

peripheral and central receptors

and activate output functions of

thermoregulation

- output functions of thermoregula-

tion are concentrated on the

maintenance of the adequate body

temperature and protection of the

organism before hypothermia

- irritation of this area causes the

muscle tremor

Control of the endocrine glands

Directly through nervous connections

posterior

pituitary gland

ncl. paraventricularis

- antidiuretic hormone (vasopressin)- oxytocin

adrenal medulla

- hypothalamic

sympathetic fibres

influence adrenaline

and noradrenaline

secretion

- control through

hypothalamus -

hypophyseal tract


ncl. supraopticus

Indirectly through vascular connections

aterior pituitary

gland

- releasing factors - liberins

- inhibitory factors -inhibins

Relation to sexual functions

- sexual development

- menstrual cycle

- ovulation

- erection

- copulation

- ejaculation

- pregnancy

- birth

- lactation

- sexual feeling

- sexual behavior

Injury of the anterior hypothalamus

- disordered interest about the sex

Injury of the posterior hypothalamus

- increased sexual activity


Control of the emotions

ncl. lateralis

Center of the fury

ncl. ventromedialis

Center of the placiditybalance

Brain cortex


Emotions are psychological processes that involve subjective experience of

comfort and discomfort linked to physiological changes (changes in heart rate,

respiratory rate change), motor manifestations (mimics, gesticulation), change

readiness and concentration. Induce and influence other psychological processes.

Hypothalamic nuclei, together with the anterior nuclei of the thalamus and

cingulate gyrus, form Papez circuit, which is an important part of the limbic

system. They represent a very close structural relationship, thus represent the

basis for the formation of autonomic manifestations of emotion.


information about

light-dark cycleretinal nerves Suprachiasmatic nuclei

(in hypothalamus)

The pineal gland (acts as a photo -

endocrine transducer)

MELATONIN (regulates circadian

timing of many physiological

functions)

Control of biological rhythms

- it is rhythmic activity generated by ncl.suprachiazmaticus. Rhythmic hypothalamic

processes extend into practically to all other functions of hypothalamus as

sympathetic tone, hormone secretion, regulation of temperature, intake of food or

fluids, sexual function, emotion or immune processes.

The light is projected into retina,

resulting in the release of the

neurotransmitter glutamate into

the suprachiasmatic nuclei

(SCN). Noradrenaline activates

the pineal gland, which produces

melatonin (in this case very little

melatonin) and melatonin acts

again in the SCN through the

melatonin receptor by blocking

the re-production of melatonin.

If the light is not projected into

retina (is the dark and have

closed eyes - ie, we sleep), this

process does not take place and

the production of melatonin is

not inhibited, so melatonin acts

in melatonin receptor vice versa.

Hypothalamus – suprachiasmatic nuclei and production

of melatonin

http://www.marie.cz/biorytmicke-cykly/

The mammalian circadian pacemaker in the

hypothalamic suprachiasmatic nucleus is organized into

two major subdisvisions, the core and the shell. The core

region of the SCN receives information about the daily

light cycle through the retinohypothalamic tract.

Both neuronal and humoral signals act as output signals

from the SCN to other regions of the brain and the

periphery. The SCN output pathways are responsible

for proper timing of various physiological functions,

including hormone release, sleep-wake cycle, feeding

behaviour, and thermoregulation. The SCN output to

the subparaventricular zone (sPVz) and to the medial

preoptic region (MPO) is for control of circadian

rhythms of body temperature, and a separate projection

through the dorsomedial nucleus of the hypothalamus

(DMH) controls daily hormone secretion through the

paraventricular nucleus (PVN) and sleep-wake cycles

through the lateral hypothalamus (LH) and

ventrolateral preoptic nucleus (VLPO).

A schematic diagram of the

suprachiasmatic nucleus and its input and

output pathways

Relation to sleep

- sleep center in anterior hypothalamus and center of wakefulness in posterior hypothalamus


Relation to immunity

Relation to memory

- Papez’s circuit – transmition of the short-term memory to the long-term memory

Complex behavior

- motivations, emotions

- it is mediated by changes in the production of hormones (glucocorticoids production) and

changes the tone of the autonomic nervous system. Sympathetic-immune interactions affect the

particular secondary lymphoid organs (spleen, lymph nodes) and is believed that to increase the

preparedness to escape/attack.

Control of metabolism

- through control of the endocrine glands – secretion of adrenaline, ACTH etc.

Sensory function

Relation to the motor system

- involuntary movements, extrapyramidal tract, basal ganglia


Viscero - visceral reflexes

visceral receptors

visceral organs (heart, smooth muscle,

gland cells)

afferent fiber

preganglionic fiber

postganglionic fiber

Autonomic nervous system – autonomic reflexes

Viscero - motor reflexes

visceral receptors

afferent fiber

preganglionic fiber

skeletal muscle

For example: the local contraction of the abdominal muscles is produced at the inflamation of

the appendix.


Viscero - cutaneous reflexex

visceral receptors

skin, vessels, sweat glands

aferent fiber

preganglionic fiber

postganglionic fiber

The capillary blood return, secretion of sweat are changed at the pathological processes in the

certain internal organs.


Cutaneous - visceral reflexex

skin receptors

effectors of visceral organs (smooth

muscle, cells of glands)

afferent fiber

preganglionic fiberpostganglionic fiber

Inhibition of the pain in the region of the visceral organ by the application of the cold or warm

stimulus.


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