Biology Reference
In-Depth Information
DMN
PHA
PVN
AHA
Hypothalamus
VMN
POA
SO
SCN
MN
ARC
OC
ME
Pars
tuberalis
Infundibulum
Anterior
pituitary
Posterior
pituitary
Pars
distalis
Figure 9.4 Hypothalamic and pituitary anatomy. Sagittal view of mammalian hypotha-
lamic and pituitary anatomy. The mediobasal hypothalamus is encompassed by red
dashed lines. The pars tuberalis, part of the anterior pituitary, is shaded in gray. AHA,
anterior hypothalamic area; ARC, arcuate nucleus; DMN, dorsomedial nucleus; ME,
median eminence; MN, mammillary nuclei; OC, optic chiasm; POA, preoptic area;
PHA, posterior hypothalamic area; PVN, paraventricular nucleus; SCN, suprachiasmatic
nucleus; SO, supraoptic nucleus; VMN, ventromedial nucleus.
undergo a controlled reduction in body temperature, heart rate, and meta-
bolic rate to conserve energy (
Fig. 9.5
A;
Carey et al., 2003; Geiser, 2004
).
Hibernation is widespread in Class Mammalia suggesting that the ability to
hibernate is an ancestral mammalian trait (
Carey et al., 2003
). The hiberna-
tion phenotype is variable across species, with the Arctic ground squirrel
(
Urocitellus parryii
) on the extreme end of the spectrum with body temper-
atures recorded below 0
C(
Barnes, 1989
).
During obligate hibernation, mammals go through periods of torpor,
ranging from days to weeks, where body temperature is only a few degrees
above the ambient temperature and metabolic rate is 2-4% of normal
