Download Thalamus, Hypothalamus, Prethalamus, and Epithalamus

Thalamus, Hypothalamus, Prethalamus, and E
Epithalamus
pithalamus
Epithalamus
diencephalon. It is located superior and
The epithalamus is a small region of the dien
posterior to the thalamus. The epithalamus consists of the habenula,, the stria
medullaris, and the pineal body
body. The habenula nuclei
lei respond to olfactory stimulation
and are involved in emotional and visceral responses to odors. The pineal body
secretes melatonin, which affects the wake/sleep pattern and is involved in circadian
rhythms.
Hypothalamus
The hypothalamus communicates with both the anterior and posterior pituitary gland to
change secretion of hormones by the pituitary gland. The hypothalamus communicates
with posterior pituitary through synaptic transmission and communicates with anterior
pituitary through soluble humoral
oral factors (hormones).
Below is a list of hormones the hypothalamus secretes, their effect on the pituitary
gland, and brief descriptions of physiological effects of the pituitary hormones.
1. Anti-diuretic
diuretic hormone: The hypothalamus senses the blood osmolality
(concentrations
ns of electrolytes and sodium) and blood pressure, and it signals the
posterior pituitary to release anti
anti-diuretic hormone, which decreases urine output,
thus increasing the volume of water in the blood.
2. Oxytocin: The hypothalamus senses stimuli
stimuli, such as the stretch of the uterus or
mechanical stimulation of the nipples, and signals the posterior pituitary to
release oxytocin, which stimulates uterine contraction and milk ejection.
For a list of hormones that affect the anterior pituitary, please refer to Table 1 in addition
to the items listed below.
enses stress or low blood sugar and
3. Growth hormone: The hypothalamus ssenses
releases growth hormone releasing hormone (GHRH). GHRH stimulates the
anterior
ior pituitary to release growth hormone
hormone, which affects
ffects uptake of amino
ami acids,
protein synthesis, as well as promotes bone and cartilage growth.
4. Thyroid-stimulating
stimulating hormone: The hypothalamus releases thyroid releasing
hormone, which stimulates the thyroid to produce thyroid-stimulating
stimulating hormone.
Thyroid-stimulating
stimulating hormone causes an increase in triiodothyronine (T3) and
tetraiodothyronine (T4).
The Saylor Foundation 1
5. Adrenocorticotropic
enocorticotropic hormone (ACTH): Stress and low blood glucose signals
the hypothalamus to release corticotrop
corticotrophin
hin releasing hormone (CRH). CRH
stimulates the anterior pituitary to release ACTCH
ACTCH, which target the adrenal
cortex and stimulates cortisol secretion. Cortisol
ol results in increases in fat,
protein degradation, and blood glucose. It also has anti-inflammatory
matory effects.
es secreted by the hypothalamus include gonadotropin-releasing
gonadotropin
6. Other hormones
hormone, which stimulates tthe anterior pituitary to secret: luteinizing hormone
and follicle-stimulating
stimulating hormone; prolactin-releasing hormone, which
whi
stimulates the anterior pituitary to secrete prolactin; and prolactin--inhibiting
hormone, which results in decreased release of prolactin from the anterior
pituitary.
Table 1: Neurohormones of the Hypothalamus that Affect the Anterior
Pituitary
Hormone
Target Tissue
Response
Growth hormone
releasing hormone
(GHRH)
Anterior pituitary cells that
secrete GH
Increased secretion of GH
Growth hormone
inhibiting hormone
(GHIH)
Anterior pituitary cells that
secrete GH
Decreased secretion of GH
Thyroid-releasing
hormone (TRH)
Anterior pituitary cells that
secrete thyroid
thyroid-stimulating
hormone
Increased secretion of
thyroid stimulating hormone
Corticotropinreleasing hormone
(CRH)
Anterior pituitary cells that
secrete adrenocorticotropic
hormone
Increased secretion
adrenocorticotropic
tropic hormone
(ACTH)
Gonadotropinreleasing hormone
(GnRH)
Anterior pitui
pituitary cells that
secrete lutein
luteinizing hormone
and follicle
follicle-stimulating
hormone
Increased secretion of
luteinizing hormone and
follicle-stimulating
stimulating hormone
Prolactin-releasing
hormone (PRH)
Anterior pituitary cells that
secrete prolactin
Increased
ncreased secretion of
prolactin
Prolactin-inhibiting
hormone (PH)
Anterior pituitary cells that
secrete prolactin
Decreased secretion of
prolactin.
The Saylor Foundation 2