Question

1. The physical stress theory applies to all areas of physical therapy and is extremely important. Explain what you understand from mechanical factors and how they affect cell injury.

Answer 1

1. The physical stress theory applies to all areas of physical therapy and is extremely important. Explain what you understand from mechanical factors and how they affect cell injury.

Physical Stress Theory (PST) is "that changes in the relative level of physical stress that cause a predictable adaptive response in all biological tissues." Qualitatively, the 5 tissue responses to physical stress are:-

· decreased stress tolerance (atrophy),

· decreased maintenance

· increased stress tolerance (hypertrophy)

· increased injury

· Increased death.

Physical therapy is an important component of recovering from an injury, it helps to

· Fix faulty movement patterns

· Prevent build-up of scar tissue

· Stretch tight muscles and joints

· Strengthen

· improved mobility

· increased strength and flexibility

· proper alignment

Mechanical Factors

Cells can respond to stress in various ways ranging from the activation of survival pathways to the initiation of cell death that eventually eliminates damaged cells. The tissues of the body are continually subjected to mechanical stimulation by external forces, such as gravity, and internally generated forces, such as the pumping of blood or muscle contraction. Within a physiological range, the forces elicit adaptive responses acutely (to rapidly alter function) and chronically (to remodel tissue structure to optimize load-bearing capabilities). When the forces exceed certain thresholds, injury results. The most commonly seen factors are:-

· movement of alignment factors

- physical activity

- occupational leisure

- self-care activities

· Extrinsic factors

- Gravity

- Orthotic devices

- Ergonomic environment

· Physiological factors

- Medication

- Age

- Systemic pathology

- Obesity

Mechanism of cell death

Cells can respond to stress in various ways ranging from the activation of survival pathways to the initiation of cell death that eventually eliminates damaged cells. The mechanism by which a cell dies (i.e., apoptosis, necrosis, pyroptosis, or autophagic cell death) depends on various exogenous factors as well as the cell's ability to handle the stress to which it is exposed.

Stress induced cell death

Cells respond to stress in a variety of ways ranging from activation of pathways that promote survival to eliciting programmed cell death that eliminates damaged cells. The cell’s initial response to a stressful stimulus is geared towards helping the cell to defend against and recover from the insult. However, if the noxious stimulus is unresolved, then cells activate death signalling pathways.

The mechanism by which a cell dies, that is, apoptosis, necrosis, pyroptosis, or autophagic cell death, often depends on its ability to cope with the conditions to which it is exposed.

•     Apoptosis

This morphology includes shrinkage and blebbing of cells, rounding and fragmentation of nuclei with condensation, and margination of chromatin, shrinkage, and phagocytosis of cell fragments without accompanying inflammatory responses (in most cases). The morphology of cells undergoing apoptosis appeared dissimilar and distinct from the morphology associated with necrosis .

•     Autophagic Cell Death

Autophagy (self-eating) is a multistep process that is characterized by the vesicular sequestration and degradation of long-lived cytoplasmic proteins and organelles, for example, mitochondria. The resulting double-membrane vesicle is termed an autophagosome.

•     Necrosis

Necrosis, a term commonly used by pathologists, refers to any deaths associated with the loss of control of ionic balance, uptake of water, swelling, and cellular lysis . This lysis releases many intracellular constituents, attracting immune cells and provoking an inflammatory response.