Hypothalamus, Subthalamus and The Third Ventricle (Diencephalon)

Question 2

Hypothalamus and its function

Answer 2

• part of the diencephalon
• receives and integrates sensory information from the internal environment and directs actions to control homeostasis

helps regulate 5 basic physiological needs:

• controls BP and electrolyte
• regulates BT
• regulates energy metabolism
• regulates reproduction
• directs stress responses
• weighs 4g

Question 3

Where is the hypothalamus located?

Answer 3

• lies below the level of the hypothalamic sulcus, found on the medial surface of the diencephalon
• it includes: chiasma opticum, tuber cinereum with inf. projection infundibulum and mammillary bodies
• surrounded by circle of willis

Question 4

Homeostatic control of Hypothalamus

Answer 4

• autonomous control
• thermoregulation
• water regulation
• liberins and statins

Question 5

What 3 systems does the Hypothalamus control?

Answer 5

• ANS
• endocrine system
• limbic system

Question 6

Connections of the hypothalamus

Answer 6

• limbic system
• pituitary gland
• somatic and visceral nuclei

Question 7

Main efferent pathways of Hypothalamus

Answer 7

• fasciculus mammillothalamicus
• hypothalamo-reticular pathway

Question 8

lateral zone of hypothalamus

Answer 8

contains two nuclei

• nucleus preopticus lateralis
• nucleus hypothalamicus lateralis
• when stimulated feeling of hunger

Question 9

mammillary bodies of hypothalamus

Answer 9

• two round pea-like structures, situated just behind the post. perforated substance
• each one consists of a white matter exterior and two grey matter nuclei inside - medial and lateral mammillary nuclei
• the mammillary bodies belong to the limbic system

Question 10

Main afferent pathways of hypothalamus

Answer 10

• Fasciculus prosencephalicus medialis
• Stria terminalis
• Fornix

Question 11

medial zone of hypothalamus

Answer 11

regio anterior

• regio tuberalis
• regio posterior

Question 12

Nuclei in regio tuberalis

Answer 12

• Nucleus dorsomedialis - center of hunger
• Nucleus ventromedialis - center of satiety
• Nucleus arcuatus - secretes releasing factors

Question 13

Nuclei in regio anterior

Answer 13

• nucleus preopticus - control paraympathetic function
• nucleus supraopticus - synthesis and secretion of vasopressin, damage causes diabetes
• nucleus suprachiasmaticus - controls circadian rhythm
• nucleus anterior - controls temperature and sexual behaviour
• nucleus paraventricularis - synthesis and secretion of oxytocin

Question 14

Nuclei in regio posterior

Answer 14

• Nucleu posterior - controls thermoregulation
• Nucleus mamillaris - impulses from hippocampal formation, tegmental nuclei and nucleus anterior thalami

Question 15

The supraoptic and paraventricular nuclei

Answer 15

• both nuclei are structurally similar, containing large bipolar neurons
• they synthesise the hormones vasopressin (antidieuretic) and oxytocin, which pass along the axons, attached to carrier proteins called neurophysins
• they are released at the axon terminals into the capillary blood-stream of the post. lobe of the hypophysis - neurohypophysis
• medial zone

Question 16

Dorsomedial and Ventromedial nuclei of hypothalamus

Answer 16

• contain neurosecretory cells which produce releasing and release-inhibitory hormones
• these hormones are transported along the axons of these neurons and are released into the bloodstream at the upper end of the hypophysial portal system
• they are carried to and regulate the function of the anterior lobe of the hypophysis
• the latter, in turn, produce hormones which regulate the function of all endocrine glands in the body

Question 17

What does vasopressin do?

Answer 17

• causes increased reabsorption of water in the distal convoluted tubules of the nephron
• it also carries arterial vasoconstriction and elevation of blood pressure

Question 18

What does oxytocin do?

Answer 18

• causes contraction of the uterine smooth muscle and the myoepithelial cells in the breast
• towards the end of the pregnancy, it is released in large amounts and stimulates labor contractions of the uterus

Question 19

What is the anterior nucleus of hypothalamus involved in?

Answer 19

thermoregulation

Question 20

What is the suprachiasmatic nucleus in hypothalamus involved in?

Answer 20

• circadian rhythm regulation - ensures proper function of biological clocks
• receives input bilaterally from the retina and sends output to other hypothalamic nuclei as well as to the pineal gland to regulate melatonin synthesis in it via the retino-hypothalamic pathway

Question 21

What does the arcuate (infundibular) nucleus do in hypothalamus?

Answer 21

• plays a role in maintaining energy homeostasis
• integrates signals from the brainstem and the periphery
• its neurons have leptin (satiety hormone) and ghrelin (hunger hormone) receptors
• they project to other hypothalamic nuclei, brainstem, cortical areas and reward pathways, all of which influence food intake

Question 22

Other hypothalamic nuclei role

Answer 22

• water intake, growth regulation, blood pressure and heart rate, metabolic rates

Question 23

Subthalamic region

Answer 23

• region situated inferolaterally to the hypothalamus and medial to the internal capsule
• contains two nuclei - subthalamic and zona incerta, and several white matter bundles - subthalamic fasciculus, ansa lenticularis and fasciculus lenticularis

Question 24

Nucleai of subthalamic region

Answer 24

• nucleus subthalamicus
• nuclei reticulares
• zona incerta

Question 25

Pathways of subthalamus

Answer 25

• Fasciculus thalamicus
• Fasciculus lenticularis
• Ansa lenticularis
• Fasciculus subthalamicus

Question 26

Third Ventricle

Answer 26

• narrow space between the two diencephalons
• anteriorly, communicates with the lateral ventricles, via interventricular foramen (of monro)
• inferiorly, with the fourth ventricle, via cerebral aqueduct

Question 27

Inferior wall of third ventricle

Answer 27

• formed by optic chiasma, the tuber cinereum and infundibulum
• two funnel shapes recesses are formed here - recessus opticus recess and recessus infundibuli

Question 28

Hypothalamus as a higher nervous center

Answer 28

• for the control of lower autonomic centers in the brainstem and spinal cord
• its role is to preserve the body homeostasis
• regulates body temp, food and water intake, circadian rhythms, hormonal balance, BP, HR, sexual function
• its reciprocal connections with the limbic system and with the thalamus suggest that the hypothalamus is the integrator of vast afferent information, and plays a role in higher brain functions, such as behavioural patterns

Question 29

Structure of anterior wall of third ventricle

Answer 29

• anterior wall is a thin narrow lamina - lamina terminalis
• anterior commissure is a round bundle of commissural nerve fibers, running across the lamina terminalis, anterior to the columns of the fornix
• contains fibers connecting the olfactory bulbs; the rest of its fibers connect the right and left amygalda
• ant. commissure and columns of fornix form the boundaries of the triangular recess, in the ant. part of the ventricle

Question 30

Lateral wall of third ventricle

Answer 30

• formed by the medial surface thalamus and the hypothalamus
• limited superiorly by the stria medullaris thalami
• two lateral walls are connected via the interthalamic adhesion

Question 31

Superior wall of third ventricle

Answer 31

• formed by the tela choroidea of third ventricle
• derives from pia mater, which during embryonic devel. folds and penetrates into the ventricular system through telodiencephalic fissure
• covered by a layer of ependymal cells
• inferiorly, along the two sagittal lines it gives rise to the choroid plexus of third ventricle
• sup. to the roof of the ventricle is the body of the fornix

Question 32

Posterior wall of third ventricle

Answer 32

• contains opening of the cerebral aqueduct, the pineal recess with a superior boundary - the habenular commissure, and an inferior boundary - the posterior commissure