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Hypothalamus and
pituitary gland

11
...
It lies just
below the thalamus and above the pituitary gland, to which it is attached by a
stalk (k Fig
...
5)
...


neurohormones
source of
oxytocin

source of
releasing
hormones

source of
ADH

HYPOTHALAMUS

capillaries
superior
hypophyseal
artery

hypothalamo–
hypophyseal tract

infundibulum
(pituitary stalk)

nerve
fibres

secretory
cells
PITUITARY
GLAND

stored
hormones

anterior
lobe of
pituitary
gland
sinusoids

neurohormones
ADH (vasopressin)
oxytocin

inferior
hypophyseal
artery

Fig
...
5 Hypothalamus and pituitary gland
...
10 The hypothalamus influences
the activity and output of autonomic
centres in the brainstem (pons and
medulla) through its extensive neural
connections with the cerebral and
limbic cortex
(k 9
...
4)
...
7
...


Being part of the limbic system (k Fig
...
9), the hypothalamus receives information
from nearly all parts of the nervous system and is also sensitive to the composition of
the blood that flows through it
...
g
...
10)
• hunger and satiety (feeling of fullness)
• menstrual cycle
...
3
...
11 The term neuro endocrine
system refers to the complex ways in
which the nervous and endocrine
systems communicate and act
together, particularly through the
hypothalamus, to maintain
homeostasis in the body
...

Research in neuroendocrinology
is identifying remarkable ways
in which the levels of pituitary
hormones oscillate (rise and fall)
in response to the ever-changing
internal and external environments
...
12 Neurohormones are released
in spurts directly into the bloodstream
...


Box 11
...
The anterior
(front) pituitary, also called the
adenohypophysis, arises from the
buccal cavity and comprises glandular
tissue
...


Hormones produced by the hypothalamus come from two sets of nerve cells that communicate
in different ways with the pituitary gland
...
11)
...
These hormones are
secreted directly into the bloodstream and reach the anterior lobe of the pituitary gland via
a network of blood vessels that run down through the pituitary stalk
...

It stimulates the onset of puberty and sexual development in both males and females
• corticotrophin-releasing hormone (CRH) stimulates the release of adrenocorticotrophic
hormone (ACTH) and other melanocortins
• growth hormone-releasing hormone (GHRH; somatotrophin) stimulates the secretion of
growth hormone (GH)
• dopamine inhibits the release of prolactin from the pituitary gland
...
12)
...
This hormone is primarily known as ADH because of its
action on the kidneys (k 8
...
4)
...
g
...
It is also essential for
the milk ejection reflex which releases the flow of milk in the breasts of nursing mothers
(k 12
...
4)
...
3
...
It consists of two
distinct parts – the posterior pituitary and anterior pituitary (k Fig
...
6) (k Box 11
...


HYPOTHALAMUS
ADH
oxytocin

KIDNEY

POSTERIOR PITUITARY
GLAND
ADH

BODY
CELLS

ANTERIOR PITUITARY
GLAND

GH

oxytocin
FSH LH
uterus

TSH

ovary

FSH

LH

prolactin

THYROID
GLAND

ACTH

TESTES

ADRENAL
CORTEX

Fig
...
6 Hormones from the pituitary gland and their targets
...


Anterior pituitary
Most hormones from the anterior pituitary (adenohypophysis) are activated or
inhibited by releasing hormones from the hypothalamus (k Box 11
...

• Growth hormone (GH; somatotrophin) stimulates growth of bones and muscles
...

• TSH (thyroid-stimulating hormone) controls the secretion of thyroxine and plays a
key role in the regulation of metabolic rate
...

• FSH (follicle-stimulating hormone) controls the production of eggs in ovaries and
sperm in the testes
...

• Prolactin stimulates breast development and milk production in women
...


Box 11
...
Production
of each hypothalamic releasing
hormone and its secretion into the
bloodstream influences the release
of the appropriate anterior pituitary
hormone into the circulation

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