Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between white adipocyte and brown adipocyte

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Difference between white adipocyte and brown adipocyte


White adipocyte
Brown adipocyte

This type of adipocytes are predominantly found in adult
Brown adipose tissue is present in humans during fetal life but diminishes during the first decade after birth.
Distribution: subcutaneous tissue, breast, greater omentum, mesenteries, visceral pericardium, orbital cavity , retroperitoneal space, bone marrow 
It is located on the back, along the upper half of the spine, and toward the shoulders. In adult it is gradually decreases. At  first decade of life it is situated in the cervical, axillary, paravertebral, mediastinal, sternal,and abdominal regions of the body. It then disappears from most sites except for regions around the kidney, adrenal glands, large vessels (i.e., aorta), and regions of the neck (deep cervical and supraclavicular), regions of the back (interscapular and paravertebral), and thorax (mediastinum).
Functions of white adipose tissue include metabolic energy storage, insulation, cushioning of vital organs, and secretion of hormones, source of metabolic water.
Brown adipose tissue is present in large amounts in the newborn, which  prevent  the extensive heat loss by heat production (thermogenesis) that results from the newborn’s high surface-to-mass ratio and avoid lethal hypothermia (a major risk of death for premature babies).
It contains unilocular fat
multilocular adipose tissue contain numerous fat droplets.
Early lipoblasts look like fibroblasts also known as preadipocyte but develop small lipid inclusions and a thin external lamina.
Early lipoblasts which develop brown adipocyte is not look like fibroblasts
Unilocular adipocytes are large cells, sometimes 100 µm or more in diameter.
brown (multilocular) adipose tissue are
Smaller diameter (10–25 µm) than those of white adipose tissue.
white adipocytes are spherical, but they may
appear polyhedral or oval when crowded together, Unilocular, spherical, flatten nucleus, rim of cytoplasm
Multilocular, spherical, round eccentric nucleus
It is white to yellowish white in colour
It is brown in colour due to large number of mitochondria
It thin cytoplasmic rim contain a Golgi complex, few poorly developed mitochondria, poorly developed cisternae of the rough endoplasmic reticulum, and free polyribosomes,  the lipid droplet contains cisternae of smooth endoplasmic reticulum and numerous pinocytotic vesicles. Each adipose cell is surrounded by a basal lamina.
The multilocular adipocyte cytoplasm contains numerous mitochondria, a small Golgi apparatus, and only small amounts of rER and sER. The mitochondria contain large amounts of cytochrome oxidase, which imparts the brown color to the cells.
White adipose tissue make up about 15-20% of the body mass in men of normal weight, it represents 20-25% of body mass in women of normal weight
brown adipose tissue makes up about 5% of the
total body mass
Mitochondria: Few, poorly developed
Mitochondria:Many, well developed
Innervation: Few sympathetic nerve fibers
Innervation: High density of sympathetic nerve fibers
Vascularization : Few blood vessels
Highly vascularized tissue
Response to environmental stress (cold exposure) :
Decreased lipogenesis
Increased lipoprotein lipase activity

Increased lipogenesis
Decreased lipoprotein lipase activity
Growth and differentiation
Throughout entire life from stromal-vascular cells
Only during fetal period
Decreases in adult life (exception: individuals
with pheochromocytoma and hibernoma)
UCP-1 genes expression:  No
Yes (unique to brown fat)

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