Understanding the Hypothalamus: Functions, Structure, and Connections

hello everyone and welcome back to my playlist of Nero Anatomy Johannes Nelson today we are going to do chapter number

13 which is hypothalamus now hypothalamus who has the word indicates this is something below Thalamus so

Thalamus hypo hypo means around below Thalamus okay and we'll see in a minute the location of hypothalamus so you will

realize that why is it called hypothalamus so it is a very small organ but it is considered as a very important

part of the central nervous system location is different parts of your central nervous

system and also stuff outside the central number system so for example the hypothalamus is known to control uh for

example the autonomic nervous system it is known to control the endocrine system and if you few other important systems

of your body so although it is small I mean if you calculate by weight point three percent only of the total brain

rate but it is very important part of the central nervous system it is essential for life this is not a

part of your body which if not present so it is not like appendix for example appendix

it is essential for life it controls now comes the important bit is it controls the autonomic nervous system the

endocrine system and does indirectly controls the body homeostasis so though important parts autonomic nervous system

and sympathetic as well as parasympathetic Loop and also the endocrine system so these systems are

being controlled by the hypothalamus the hypothalamus is well placed for this purpose

it is so it is well placed for the purpose of controlling uh your body lying in the

center of the limbic system it is the site of numerous converging and diverging yeah

these are called either the afferent Pathways or they are also called a converging Pathways

these are called the diverging Pathways or the efferent pathways it is a site of numerous converging and

diverging neural Pathways and through its Advocate blood supply it is able to uh I like this word so much it is able

to sample the blood chemistry a very important statement again uh hypothalamus blood supply

is so it is able to scan the blood it is able to sample the blood or something

so hypothalamus is able to trace the chemistry of the blood okay hormones make appropriate controlling response

following the integration of its nervous and chemical input so that's again a very important point

it is placed so well K is let's Supply before the chair okay it is able to scan the blood and then modulate uh the body

homeostasis one by control playing the autonomic nervous system and two by controlling the endocrine system okay

now let's talk about in further detail about hypothalamus it's part of the diencephalon so

different parts so hypothalamus is part of dance that extends from the region of optic chiasma

to the caudal border of the memory body so yes key boundaries so if you look at the side view this is the area of optic

chaosm so that's the optic chaos then you have to go up till the area of the memory body these are the memory

bodies so this is where you actually see the hypothalamus area okay and here you know that this is the thalamus yes

okay so is that clear all this area this is hypothalamus okay hypothalamus is from the inferior view Decay so this is

so if you have a look here now this is the optic chaosm and these are the mammalary bodies so area in between the

optic chiasm and the mammary body is the hypothalamus so hypothalamus locations and posteriorly by the caudal border of

the memory it lies below hypothalamus and forms the floor and the inferior part of the

lateral wall of the third ventricle so yeah so this is

in the lateral wall of the third ventricle anterior to the hypothalamus is an area that for functional reasons

is often included in hypothalamus because it extends forward from the optic chiasma to the lamina terminalis

and the anterior commissure it is known as the pre-optic area simple words it is present

um anteriorly to the hypothalamus and since it is present in relation to the optic area optic areas so therefore we

call this area as pre-optic area so the pre-optic area is just before the optic chiasm this area somewhere is the

pre-optic area but as part of hypothalamus because that area functionally is

related to hypothalamus this is actually included now quarterly the hypothalamus merges into the

tegmentum of the midbrain the lateral boundary of the hypothalamus is formed by the internal capsule so if you look

here there uh you know this is the hypothalamus literally there will be internal capsules

Anatomy for example foreign it is not demarcated well but you kind of for the sake of easiness to study you

divide them into different areas when observed from below the hypothalamus is seen to be related to the following

structures optic chiasma tuber cynarium and infungibulum and mammalary bodies infundibulum and mamillary body so these

are the structures which are visible from Below the small area of the brain will be seen in the following paragraphs

to control body homeostasis how important hypothalamus is so it basically play a vital role also

in controlling the emotional Behavior because I told you it is right in the center of the limbic system and you know

one of the jobs of the limbus system is to control the emotional Behavior so it is pretty obvious that hypothalamus is

also doing the same job organization of neurons say for example this is brain or brain

neurons there will be cell body of the neuron and then there will be a long Exon acid

structure yeah yeah there is a cell body and then an Exon where there are a lot of cell bodies

present and aggregated together so this aggregation is known as a nuclear your nucleus

this particular area or even a fluorescent sustaining electron microscopy routine microscopy

okay there are aggregation of cell bodies aggregation of cell bodies these are very overlapping structures

these are these are vague boundaries as a clear-cut boundaries but anyways for the purpose of description

so microscopically the hypothalamus is composed of small nerve cells that are arranged in groups called nuclei many of

which are not clearly segregated to form from one another either they are not clearly segregated from each other which

means they are very much overlapping which means their boundaries are not very sharp and clear-cut for functional

reasons the pre-optic area is included as part of the hypothalamus which is in relation to the optic chiasm

basically hypothalamus for purpose of description the nuclei are divided by an imaginary parasagital

plane into medial and lateral zones this is just for the purpose of description and the line dividing them is imaginary

so if you over line lying within the plane are The Columns of the fornix and memolothalamic track

will be obviously towards the medial side of the brain and later will be towards the lateral side of the brain

this is how it is labeled like it is so this is the midline for example these are the medial nuclei

these are the lateral so obviously is rather than this particular section because that's a side view

and that's a view through a different sections okay but anyways for the examination

purpose you have to remember it like this okay what are the different nuclei present in hypothalamus so you have to

tell them accordingly okay there is a medial zone of nuclei there is a lateral zone of nucleus

there are pre-optic nucleus and try to locate them in the diagram you see the pre-optic nucleus this is right at the

interior part of the hypothalamus then there is an anterior nucleus Supra chiasmatic nucleus para ventricular

nucleus asthmatic nucleus paraventricular nucleus so try to read

them from here and locate them on the diagram that's how you build your Concepts there is a dorsometal nucleus

there is a ventro medial nuclear players in fundibular and posterior nucleus so again if you go back to this diagram

many of them are visible either on this section or on this section you see ventero medial in fungibility nucleus

all these these are all part of the medial medial group of nuclei so medial group is towards the midline remember

this is the infundibular bilkul medial this is the Venture of media this then there is dorsomedial is

then there is paraventricular so these are all the nuclei which are in the medial Zone therefore called the medial

so some of them are visible in this particular section some of them are more clearly visible in this particular

section but my point is try to remember the names they're important for exams and you should know where actually they

are located then there is a lateral group of hypothalamic nuclei and they include

pre-optic nucleus Supra chiasmatic as a Supra chiasmatics part medial group may be here if you remember we just had this

name heard Supra asthmatic nucleus so this is also present in the medial Zone some part of it is also I told you this

is overlapping these are not sharp boundaries therefore it is quite understandable okay

lateral Zone then Supra optic nucleus how they uh control different hormonal functions of your body so Pro optic for

example the lateral nucleus thermomelier nucleus lateral tubercle nuclei so again if you go back to this diagram

mammilothermic track you see here then the memory bodies and the posterior nucleus so literal group of nuclei and

medial group of nuclei I remember the names okay art medial group Mayhem nuclei or six nuclei lateral group now

some of the nuclei such as the pre-optic nucleus and the suprachiasmatic nucleus and the mammalian nuclei they overlap

both the zones it should be emphasized that most of the hypothalamic nuclei have ill-defined

boundaries with the use of modern technology including histochemical immunochemical and Terror grade and

retrograde Tracer studies groups of neurons and their connections are being more precisely identified but at the

moment they're very overlapping particularly boundary has super optic nucleus

they're all kind of mixed things unfortunately is the new nuclear groups are discovered and given names the

reader has difficulty coming to terms with the old and the new nomenclature only the major groups with

well-established names and their connections are described on this account

um these are only for the famous group of nuclei and their connections otherwise

but unless that is part of the you know big literature or textbooks they are part of the General Studies

so this is how medicine goes actually if somebody you know publishes original article though a particular research

here and then people start doing clinical trials and then meta-analysis

foreigners so there are many Pathways which are coming towards the hypothalamus and then there are many

Pathways which are going out from the hypothalamus because it is in the center so there are afferent Pathways and then

there are if lines of communication the hypothalamus receives information from the rest of the body

rest of the body body information almost hypothalamus through nervous connection it has nervous connections number two it

has the bloodstream qka scan it can it can talk about the chemistry of the blood it can sense the chemistry

of the blood and one more thing it senses is the cerebrospinal fluid areas

can sense the neuronal pathways it can sense the blood it can also sense the cerebrospinal fluid the neurons of

the hypothalamic nuclei respond and exert their control via the same root yeah

uh either via the blood it will release some chemicals in the blood it may also release some chemicals in the central uh

cerebrospinal fluid so the hypothalamus is receiving information from three broader domains and it is also sending

out outputs into three broader domains that is into the neuronal circuit into the bloodstream as well as into the CSF

connections which lies in the center of the limbic system receives many afferent fibers

from viscera the olfactory mucous membrane the cerebral cortex the limbic system you see visrative information

then all faction then the cerebral cortex someric and visceral our friend General

sensation and gustatory and visceral sensation are you know coming to the hypothalamus through collateral branches

of the lemnescal afferent fibers you remember the liminal Sky which Ascend in the central nervous system they go to

the hypothalamus as well okay also the tractor solitarius through reticular formation so the point is a hypothalamus

is receiving somatic input visceral inputs via the liminal skill pathway and as well as via the tractor solitary

areas then there are visual afferents that leave the optic hair asthma and pass to the suprachiasmatic nucleus you

see suprachiasmatic nucleus medial Zone maybe lateral Zone maybe and it was in very close relation to the optic asthma

so if you studied this diagram very well we try to identify this is the suprachiasmatic nucleus that is the

optic asthma they are enclosed relation so some of the neuronal fibers leave from here go to the suprachiasmatic

nucleus and pass on to the information there then there are all factions travel through the medial forebrain bundle

auditory our friends cortico hypothalamic fibers Norm student cortico hypothalamine they're coming

from the cortex they arise from the frontal lobe of the cerebral cortex and pass directly to the hypothalamus then

there is hippocampo hypothalamic hippocampus they pass from the hippocampus through

the foreign body many neurophysiologists regard the hypothalamus as the main output pathway for the limbic system so

this is not something which can be ignored this is huge input uh you look at this diagram for example let me try

to find where is this one particularly so here we have this is the hypothalamus these are all the fibers so take mental

fibers from the midbrain for example olfactory fibers from the olfactory Center cortico hypothalamic frontal

cortex a fibers are in to the hypothalamus see these are all very important via the fornix these fibers

hippocampo hypothalamic fibers they are also coming in there then from the thalamus the fibers are coming so from

different parts of the body as well as you know you see the liminal pathway from the viscera in the somatic offering

information there is afferent coming into the hyper so if you have to draw a diagram for

offering fibers to the hypothalamus this is the diagram to remember and draw yes auditory or faction visual visceral for

example this is the visceral these are from the midbrain uh that is from the cortex these fibers are coming from

Thalamus these are from hippocampus so very important region sorry information you see tegmental fibers from the

midbrain Thalamus fibers hypothalamic from the amygdala they pass from the immature complex of that to the

hypothalamus through these trial terminals so big inputs from almost all parts of your body

so obviously if there is a lot of input there has to be a lot of output as well and this is true in case of hypothalamus

so there are efferent nervous connections which is what we call the output of the hypothalamus so the

efferent connections of the hypothalamus are also numerous and complex and only the main pathways are described

this is also very complex here okay and Main pathways are only listed here number one there are descending fibers

to the brain stem and the spinal cord and this is the way it controls the sympathetic parasympathetic system so

these fibers influence the peripheral neurons of the autonomy nervous system they descend through a series of neurons

in the reticular formation the hypothalamus is connected to the parasympathetic nuclei of oculomotor

facial glossopharyngeal vagus nerves in the brain stem so it is connected with these parasympathetic nuclei therefore

it is controlling the parasympathetic nervous system in a similar manner the reticulospinal fibers connect the

hypothalamus with the sympathetic cells of origin in the lateral gray horns of the first thoracic segment to the second

thoracolumbar outflow the spinal system so it is basically controlling the pns which is the parasympathetic nervous

system as well as the sympathetic nervous system so it is controlling both and therefore chapter

if you go back to the first page I told you that it controls the autonomic nervous system and now you know how does

it control the autonomic nervous system okay so this is one output the other output that I have to discuss with you

is the memolothalamic tract which arises in the memory body and terminates in the anterior nucleus of the thalamus here

the pathway is relayed to the cingulate gyrus so uh let me tell you where is the diagram this is the output diagram so in

this diagram you see this is the hypothalamus area and from the memory body it is going information is going to

the thalamus information is going down in the descending fibers to the brain stem as well as the spinal cord to

control the autonomic nervous system fibers also go to the midbrain mamulotech mental tract

fibers also go to the hypophyseal tract very important because from there uh your pressure gland have a Buddha

control by the hypothalamus so it is not only receiving inputs it is also giving out inputs okay so memolo tegmental to

the midbrain it also gives multiple Pathways to the limbic system so a very important discussion that we are at the

moment undertaking you must remember the inputs and the outputs of Thalamus designated area specialized discussion

okay what are although hypothalamus is connected with a lot of different parts of your brain

hypothalamus is connected in terms of efferent and afferent fibers to the thalamus to the optic chaosium to the

olfactory lobe to the cortex to the brain stem to the spinal cord and to the thalamus and what notes hypothesis

because hypothesis what is the other name for hypothesis cerebral is also known as the pituitary

gland pituitary gland Master gland of the body because it secretes all those important hormones

which control the job of other endocrine glands so for example thyroid stimulating hormone released from the

pituitary controls the release of thyroid hormones important follicle stimulating hormone

luteinizing hormones hormones such as thyroid such as the ovaries such as the testicles

foreign by the nerve fibers of these two nuclei or these travel they arise in the

hypothalamus and then go into the pituitary posterior lobe of the pituitary so this

is the connection there are two lobes there is an anterior lobe and a posterior lobe so the posterior lobe

case that is the nerve fiber connection here by the long and short portal blood vessels that connect the sinusoids of

the median Eminence and the infundibulum with the capillary plexus in the anterior lobe

okay what is the uh you know Venus yeah capillary yeah portal connection so one is neural connection yeah nervous

connection the other one is the portal blood supply connection portal blood supply connections

whatever is released in the hypothalamus enters into the portal circulation and then enters to the anterior lobe of the

the other with the posterior lobe of the tissue tree so if you look at this diagram here this is the hypothalamic

area and uh this is connection number one this is connection number two so let's have a

look this is so whatever is synthesized in the super optic nucleus and paraventricular

nucleus it travels down into the Exon and ultimately reaches the posterior low foreign

foreigners enter into the first capillary Network goes down or capillary network is

so things produce here will travel down into the blood supply and exit into the anterior lobe of the picture tray so

yahape chemicals are transferred from the hypothalamus to the posterior lobe of the pituitary by neurons and here the

things are transferred from the hypothalamus to the anterior lobe of the pituitary by Blood portal systems

the first one which is the neuronal connection which is also known as hypothalamo hypophysial tract

hypothalamo because it is arising from the hypothalamus hypophyseal because it is going to the hypophysis which is the

pituitary now the hormones vasopressin and oxytocin are synthesized in the nerve cells of supraoptic and

paraventricular nuclei the hormones are passed along the exons together with the carrier proteins known as the

neurophysins and release into the Exon terminals here the hormones are absorbed into the bloodstream and the fenestrated

capillaries of the posterior lobe of the pituitary vasopressin and oxytocin which are

produced in these nuclei these two nuclei they travel down and released here in the posterior lobe of the

pituitary the hormone vasopressin is which is also called antidiuretic hormone it's

produced mainly in the nerve cells of the supraoptic so why isoprocin in the super optic and oxytocin in the

paraventricular so that's something okay we know this now the other hormone uh oxytocin which is produced in the

paraventricular nucleus is important for contraction of the uterus during delivery also during lactation the

myoepithelial cells of the breast are contracted so the milk can be ejected from the breast so that's the job of the

oxytocin the supraoptic nucleus which produces vasopressin act as an osmoreceptor or

Isis and this we have discussed in very much detail in physiology lectures so you can

watch my renal physiology videos from Gretchen to understand what is the job of ADH okay but here my job to explain

the connections of hypothalamus with the pituitary basically foreign what is the composition of the

portal system at the hypothesis cerebral level so basically a branch from the internal carotid comes divides into

capillaries then a portal vein divides again into capillaries and then the vein so whatever is synthesized here in the

hypothalamus enters into the first capillary Network and then exits to the internal lobe of the pituitary by the

second capillary Network this is how it works and you will be surprised

going to be an extremely important discussion things which are synthesized in the

hypothalamus which will be synthesizing those things but the cells which synthesize those

things are called the neurosecretory cells and they are situated in the hypothalamus media

and they're responsible for production of either releasing hormones or release inhibitory hormones

if we look at this table first I want you to have a look at this particular column

hormones from the anterior pituitary [Music] functions growth hormones

growth hormone that is something that is mixed with this one and actually is the reduced

production of the growth hormone so growth hormonal produce from the pituitary it will stimulate growth so it

will decelerate the growth obviously important for lactogenesis which is important for stimulation of

the adrenal gland thyroid stimulating hormone for thyroid stimulation luteinizing and FSH reproductive

hormones these are all released from the anterior pituitary

you have a look at this particular column of those things which are released from

the hypothalamus and they control the release of the entry pituitary hormones growth hormone releasing hormone wow

growth hormone release but this hypothalamus is Master of the master yeah

growth that's the normal cycle order growth hormone release

foreign so release the growth hormone so I am the master hypothalamus is the main

master of your body okay so that's how basically the two connections work with the paraventricular nucleus and the

supraoptic nucleus they produce oxytocin and vasopressin or Dosa connection here by the portal connection

and that is the major releasing hormones or the inhibiting hormones of the main hormones

of the entry pituitary lovely discussion I so like it but try to spend time on this and understand it okay

another uh important uh you know this is now something that we have already covered

now you know your hypothalamus it has autonomic control because this message to fibers nickel Ray that are

going to control the parasympathetic nervous system also the sympathetic nervous system and therefore it controls

you know the heart rate and GI motility and gastric juice function automatically Under the

Umbrella of hypothalamus so now you realize okay how important is hypothalamus job number one autonomic

control then job number two endocrine control growth hormone releasing hormone release

hormone release hormone all the hormones of the entry pituitary they are being controlled by the hormones from the

hypothalamus so it is damn important then neurosecretion the secretion of vasopressin and oxytocin it comes under

this heading because they are both synthesized in the neurons therefore this is called neural secretion then

another job of hypothalamus is to control temperature the anterior portion of the hypothalamus controls you know

the temperature or heat loss mechanisms experimental stimulation of this area causes dilatation of the skin blood

vessels because a sympathetic or parasympathetic outflows for control therefore it is involved in there then

regulation of food and water intake a stimulation of the lateral region of the hypothalamus this is experimental

hypothalamus lateral region of the hypothalamus this lateral region sometimes is

referred to as the hunger Center also bilateral destruction of this Center results in anorexia yeah

evidence they are involved in phenomena satiety Center hunger Center

experimental stimulation also uh indicates okay there are thirst centers in the hypothalamus so hypothalamus is

not only controlling the autonomic nervous system the endocrine system neural secretion by secreting oxytocin

and vasopressin controlling the temperature also controls the hunger and water intake emotion Behavior because it

is situated right in the middle of the limbic system it is believed okay hypothalamus also has an important in

connection with the limbic system all those details but it also controls our emotions so emotions and behaviors are a

function of the hypothalamus limbic system and prefrontal cortex and all these are connected with each other by

different fibers some authorities believe that the hypothalamus is the integrator of afferent information

received from other areas of the nervous system and brings about the physical expression of emotion okay so it's it's

it's involved in emotional control then the control of the circadian rhythms the normal biological clock of your body the

hypothalamus controls many circadian rhythms including body temperature adrenocortical activity eosinophil count

renal secretion is obviously experimental studies for example anterior part of the

hypothalamus it seriously interferes with the rhythm of sleeping and waking it is all the cycle is all Disturbed

suprachiasmatic new nucleus which receives afferent fibers from retina appears to play an important role in

controlling the biological rhythms nerve impulses generated in response to variations in intensity of light are

transmitted via this nucleus to influence the activity so basically body circadian rhythms

for example I was in Glasgow for a few years so Glasgow May there Comes A Time In The Air jisme sunlight

sometimes and therefore in those times people go in depression and sleep pattern all

those sort of things okay now with this you should now realize how important is your hypothalamus functions

okay so hypothalamus get input from nerves and hormones and it gives output to control the autonomic system and the

endocrine system beautiful diagram uh short but important okay main hypothalamic nucleus

medial or lateral zones so very important so for example nuclei it controls the parasympathetic

system so read this table this is damn important okay and then this is nuclear origin of hypothesis

this is something that is kind of covered in this particular table so remember this table and this table in

particular so that then sums up our discussion on hypothalamus extremely important organ in your central nervous

system huge responsibility big connections so try to remember the wrong okay