The hypothalamus connects to the pituitary gland and brainstem and controls many functions important for homeostasis like appetite, body temperature, fluid balance, and hormone production. It regulates these functions through releasing/inhibiting hormones that control the pituitary as well as hormones like ADH and oxytocin. The thalamus is a relay station that integrates sensory information and distributes it to other brain areas like the cortex and hypothalamus. It contains nuclei that process specific senses and is involved in voluntary movement and personality.

1. HYPOTHALAMUS

2. Objectives
• Describe the anatomic connections between the hypothalamus and
the pituitary gland and the functional significance of each connection.
• Functions of hypothalamus to be memorized.

4. Hypothalamus, Connections
1) Backward and downward to the brain stem, mainly into
the reticular areas of the mesencephalon, pons, and
medulla and from these areas into the peripheral nerves
of the autonomic nervous system;
(2) upward toward many higher areas of the diencephalon
and cerebrum, especially to the anterior thalamus and
limbic portions of the cerebral cortex;
(3) into the hypothalamic infundibulum to control or
partially control most of the secretory functions of both
the posterior and the anterior pituitary glands.

8. FUNCTIONS
• The portion of the brain that maintains the body’s internal balance
(homeostasis).
• The hypothalamus is the link between the endocrine and nervous
systems.
• The hypothalamus produces releasing and inhibiting hormones,
which stop and start the production of other hormones throughout
the body.

9. The hypothalamus plays a significant role in the
endocrine system & homeostasis*:
• Heart rate and blood pressure
• Body temperature
• Fluid and electrolyte balance, including thirst
• Appetite and body weight
• Glandular secretions of the stomach and intestines
• Production of substances that influence the pituitary
gland to release hormones
• Sleep cycles

10. Functions of Hypothalamus
Vegetative Functions and
Endocrine Functions

11. Endocrine function
1) Hypothalamic Control of Endocrine Hormone
Secretion by the Anterior Pituitary Gland
(Specific releasing and inhibitory hormones are
secreted into the blood by various hypothalamic
nuclei.)
2) ADH and Oxytocin

14. Vegetative Functions of the Hypothalamus
Cardiovascular Regulation
Stimulation in the posterior and lateral hypothalamus increases the
arterial pressure and heart rate,
Stimulation in the preoptic area often has opposite effects, causing a
decrease in both heart rate and arterial pressure.
These effects are transmitted mainly through specific cardiovascular
control centers in the reticular regions of the pons and medulla.

15. Regulation of Body Temperature
The anterior portion of the hypothalamus, especially
the preoptic area, is concerned with regulation of
body temperature.
An increase in the temperature of the blood flowing
through this area increases the activity of
temperature-sensitive neurons, whereas a decrease
in temperature decreases their activity.
In turn, these neurons control mechanisms for
increasing or decreasing body temperature.

16. Gastrointestinal and Feeding Regulation
lateral hypothalamic area
Stimulation leads to hunger and search for food, damage to this area
on both sides of the hypothalamus causes loss desire for food,
sometimes causing lethal starvation &extreme passivity.

17. In the ventromedial nuclei is satiety centre.
When this center is stimulated electrically, an animal that is eating food
suddenly stops eating and shows complete indifference to food.
Bilateral lesions of the ventromedial areas of the hypothalamus cause excessive
drinking and eating, as well as hyperactivity and sometimes rage

18. Regulation of Body Water
The hypothalamus regulates body water in two ways:
1) by creating the sensation of thirst, which drives the
animal or person to drink water, and
2) by controlling the excretion of water into the urine.

19. An area called the thirst center is located in the lateral
hypothalamus.
When the fluid electrolytes in either this center or closely
allied areas become too concentrated intense desire to
drink water develops.

20. Control of renal excretion of water is vested mainly in
the supraoptic nuclei.
When the body fluids become too concentrated, the
neurons of these areas become stimulated.
Nerve fibers from these neurons project downward
through the infundibulum of the hypothalamus into
the posterior pituitary gland, where the nerve
endings secrete the hormone ADH(also called
vasopressin).*

21. Strong stimulation of the punishment centers of
the brain, especially in the periventricular zone
of the hypothalamus and in the lateral
hypothalamus, causes the animal to
(1) develop a defense posture,
(2) extend its claws,
(3) lift its tail,
(4) hiss,
(5) spit,
(6) growl, and (7) develop piloerection, wide-open
eyes, and dilated pupils.
Furthermore, even the slightest provocation
causes an immediate savage attack. This is
approximately the behavior that one would
expect from an animal being severely punished,
and it is a pattern of behavior that is called Rage.

22. Regulation of Uterine Contractility and of Milk
Ejection
Stimulation of the paraventricular nuclei causes their
neuronal cells to secrete the hormone oxytocin.
This in turn causes increased contractility of the
uterus,
as well as contraction of the myoepithelial cells
surrounding the alveoli of the breasts, which then
causes the alveoli to empty their milk.

23. Another area of the hypothalamus that enters into overall control of
gastrointestinal activity is the mamillary bodies; these control at least
partially the patterns of many feeding reflexes, such as licking the lips
and swallowing.

24. Specific Functions of Other Parts of the Limbic System
• Functions of the Hippocampus*
• Functions of the Amygdala

26. Because of these multiple connections, the amygdala has
been called the "window" through which the limbic system
sees the place of the person in the world.

27. Effects initiated from the amygdala and then sent
through the hypothalamus include
(1) increases or decreases in arterial pressure;
(2) increases or decreases in heart rate;
(3) increases or decreases in gastrointestinal motility
and secretion;
(4) defecation or micturition;
(5) pupillary dilation or, rarely, constriction;
(6) piloerection
(7) secretion of various anterior pituitary hormones,
especially the gonadotropins and adrenocorticotropic
hormone.

28. In addition to the effects similar to hypothalamic
stimulation
(1) tonic movements, such as raising the head or
bending the body;
(2) circling movements;
(3) occasionally clonic, rhythmical movements;
(4) different types of movements associated
with olfaction and eating, such as licking,
chewing, and swallowing.
In addition, stimulation of certain amygdaloid
nuclei can cause a pattern of rage, escape,
punishment, severe pain, and fear similar to the
rage pattern elicited from the hypothalamus.
Stimulation of other amygdaloid nuclei can give
reactions of reward and pleasure.

29. The Klüver-Bucy Syndrome
When the anterior parts of both temporal lobes are destroyed in a
monkey, this removes not only portions of temporal cortex but also of
the amygdalas that lie inside these parts of the temporal lobes. This
causes changes in behavior called the Klüver-Bucy syndrome.

30. 1) is not afraid of anything,
(2) has extreme curiosity about everything,
(3) forgets rapidly,
(4) has a tendency to place everything in its mouth
and sometimes even tries to eat solid objects, and
(5) often has a sex drive so strong that it attempts to
copulate with immature animals, animals of the
wrong sex, or even animals of a different species.

31. Overall Function of the Amygdalas
The Amygdalas seem to be behavioral awareness areas that operate
at a semiconscious level.
They also seem to project into the limbic system one's current status
in relation to both surroundings and thoughts.
On the basis of this information, the amygdala is believed to make the
person's behavioral response appropriate for each occasion.

32. THALAMUS

33. Objectives
To review a very complex area of the nervous system and
To emphasize that the thalamus lies at the center of many afferent
and efferent neuronal loops to other parts of the nervous system

34. The thalamus is situated at the rostral end of the
brainstem and functions as an important relay and
integrative station for information passing to all areas
of the cerebral cortex, the basal ganglia, the
hypothalamus, and the brainstem.
Its a large, egg-shaped mass of gray matter that forms
the major part of the diencephalon. There are two
thalami, and one is situated on each side of the third
ventricle.

39. Nuclei of thalamus
• Ventral anterior nucleus
• Ventral lateral nucleus
• Ventral posterior nucleus
Other Nuclei of the Thalamus
• These nuclei include the intralaminar nuclei, the
midline nuclei, the reticular nucleus, and the medial
and lateral geniculate bodies.

40. Functions of Thalamus
The thalamus is made up of complicated collections of nerve cells
that are centrally placed in the brain and are interconnected.
A vast amount of sensory information of all types (except smell)
converges on the thalamus and is integrated.
The resulting information pattern is distributed to other parts of the
central nervous system.

41. Following removal of the cortex, the thalamus
can appreciate crude sensations.
However, the cerebral cortex is required for the
interpretation of sensations based on past
experiences. For example, if the sensory cortex is
destroyed, one can still appreciate the presence of a
hot object in the hand; however, appreciation of the
shape, weight, and exact temperature of the object
would be impaired.

42. The thalamus possesses certain very important nuclei
whose connections have been clearly established.
These include
1)The ventral posteromedial nucleus receives the
ascending trigeminal and gustatory pathways,
2)while the ventral posterolateral nucleus receives the
important ascending sensory tracts, the medial and
spinal lemnisci.

43. 3) The ventroanterior and the ventrolateral nuclei of
the thalamus form part of the basal nuclei circuit and
thus are involved in the performance of voluntary
movements.
These nuclei receive input from the globus pallidus
and send fibers to the prefrontal, supplemental, and
premotor areas of the cerebral cortex.

44. 4) The large dorsomedial nucleus has extensive
connections with the frontal lobe cortex and
hypothalamus.
This nucleus lies on the pathway that is concerned
with subjective feeling states and the personality of
the individual.

45. 5) The intralaminar nuclei are closely connected with
the activities of the reticular formation, and they
receive much of their information from this source.
Their strategic position enables them to control the
level of overall activity of the cerebral cortex.
The intralaminar nuclei are thus able to influence the
levels of consciousness and alertness in an individual.

46. • The thalamus is centrally located among other
important nervous structures. Usually, a thalamic
lesion results in dysfunction of neighboring
structures, producing symptoms and signs that
overshadow those produced by the thalamic disease.
• For example, a vascular lesion of the thalamus may
also involve the midbrain, with resulting coma, or a
lateral extension of thalamic disease may involve the
internal capsule and produce extensive motor and
sensory deficits.

47. • Surgical Relief of Pain by Thalamic Cauterization
The intralaminar nuclei of the thalamus are known to
take part in the relay of pain to the cerebral cortex.
Cauterization of these nuclei has been shown to
relieve severe and intractable pain associated with
terminal cancer.
• Thalamic Pain
Thalamic pain may occur as the patient is recovering
from a thalamic infarct. Spontaneous pain, which is
often excessive (thalamic overreaction), occurs on the
opposite side of the body. The painful sensation may
be aroused by light touch or by cold and may fail to
respond to powerful analgesic drugs.

48. • Abnormal Involuntary Movements
Choreoathetosis with ataxia may follow vascular
lesions of the thalamus. It is not certain whether
these signs in all cases are due to the loss of function
of the thalamus or to involvement of the neighboring
caudate and lentiform nuclei. The ataxia may arise as
the result of the loss of appreciation of muscle and
joint movement caused by a thalamic lesion.

49. Lesions of the Thalamus
• Sensory Loss
These lesions usually result from thrombosis or
hemorrhage of one of the arteries supplying the
thalamus.
Damage to the ventral posteromedial nucleus and the
ventral posterolateral nucleus will result in the loss of
all forms of sensation, including light touch, tactile
localization and discrimination, and muscle joint
sense from the opposite side of the body.

50. • Thalamic Hand
The contralateral hand is held in an abnormal posture
in some patients with thalamic lesions. The wrist is
pronated and flexed, the metacarpophalangeal joints
are flexed, and the interphalangeal joints are
extended. The fingers can be moved actively, but the
movements are slow. The condition is due to altered
muscle tone in the different muscle groups.