Related Concept Videos

Huntington Disease l: Introduction01:21

Huntington Disease l: Introduction

Huntington disease or HD is a progressive, fatal neurodegenerative disorder inherited in an autosomal dominant pattern.PathophysiologyIt is caused by expansion of the CAG trinucleotide repeat in the HTT gene on chromosome 4 (4p16.3), producing an abnormal huntingtin protein with an expanded polyglutamine tract. This misfolded protein disrupts cellular function, leading to neuronal death. Normal alleles have ≤26 repeats, 27–35 are intermediate (risk of expansion), 36–39 show reduced penetrance,...
Cushing Syndrome II: Pathophysiology01:19

Cushing Syndrome II: Pathophysiology

Cortisol production is normally governed by the hypothalamic–pituitary–adrenal (HPA) axis, which maintains hormonal balance through tightly regulated feedback mechanisms. Disruption of this regulatory system is central to the development of Cushing syndrome, whether the excess cortisol originates from external medications or internal pathology. Persistent cortisol elevation alters metabolism, immune function, and endocrine signaling, producing the characteristic clinical features of the...
Sleep-Wake Cycles01:24

Sleep-Wake Cycles

Sleep is an essential physiological process vital to maintaining overall well-being. The reticular activating system (RAS), a network of neurons in the brainstem, regulates wakefulness and sleep. While it may seem passive, sleep consists of distinct cycles, each with its unique characteristics and functions. Two key sleep phases are non-rapid eye movement (NREM) and  rapid eye movement (REM).
NREM Sleep
NREM sleep comprises four progressive stages that seamlessly merge:
Regulation of Hematopoietic Stem Cells01:01

Regulation of Hematopoietic Stem Cells

All blood and immune cells are produced from the multipotent hematopoietic stem cells (HSCs) by the process of hematopoiesis. However, they all have a limited life span. In addition, many are depleted in immune surveillance or combatting an injury or infection. This makes blood one of the most regenerative tissues. Hematopoiesis helps replenish these blood and immune cells, restoring the body's normal functioning. However, overproduction of blood and immune cells can make them cancerous or...