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Lesions of Upper Motor Neurons and Lower Motor Neurons

Lesions of Upper Motor Neurons and Lower Motor Neurons

Upper Motor Neurones (UMN), Lower Motor Neurone (LMN) and their Lesions
All the neurons contributing to the pyramidal and extrapyramidal systems should be called upper motor neurons (UMN).
The anterior horn cells and the related neurons in the motor nuclei of some cranial nerves are called lower motor neurons (LMN). Axons of these cells give rise to the peripheral motor nerves. These …

Resting Membrane Potential, Action Potential and Ionic Basis

Resting Membrane Potential, Action Potential and Ionic Basis

Resting Membrane Potential (RMP)
There exists a potential difference across the cell membrane in all the living cells in resting conditions which is known as resting membrane potential. The value of RMP normally varies from 5 millivolts(mV) to -100 millivolts(mV). The value mainly depends upon the type of the cell. The value of RMP in nerve fibres and  skeletal muscles is …

Renal Counter Current Mechanism Made Simple

Renal Counter Current Mechanism Made Simple

Introduction:
Countercurrents exist when fluids flow in opposite directions in parallel and adjacent tubes. There are 2 countercurrent systems and an osmotic equilibrating device:

Countercurrent multiplier (Loop of Henle): Establishes gradient of osmolarity from cortex (300mOsm/L) to the papilla (1200mOsm/L) aided by Urea recycling
Countercurrent exchanger (Vasa recta): Maintains the corticopapillary osmotic gradient established by Countercurrent multiplier
Osmotic equilibrating device (Collecting duct): Depending on …

Cardiac Cycle

Cardiac Cycle

Definition: Cardiac cycle refers to the cardiac events that occur from the beginning of one heart beat by spontaneous generation of action potential in SA node to the beginning of the next. When the heart rate is 75/min, the period of one cardiac cycle is 0.8 sec.
Important terms:

Diastole: a period of relaxation during which heart fills with blood
Systole: a period …

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