Module 3_Organ System

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A general overview of the whole body systems.


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Organ Systems:

Organ Systems Collation of Different Organs as Single System

The Digestive System:

The Digestive System


Liver The liver performs several roles in carbohydrate metabolism: Gluconeogenesis (the synthesis of glucose from certain amino acids, lactate or glycerol) Glycogenolysis (the breakdown of glycogen into glucose) (muscle tissues can also do this) Glycogenesis (the formation of glycogen from glucose)


Gluconeogenesis Gluconeogenesis is the generation of glucose from non-sugar carbon substrates like pyruvate, lactate, glycerol, and glucogenic amino acids (primarily alanine and glutamine). The vast majority of gluconeogenesis takes place in the liver and, to a smaller extent, in the cortex of kidneys. This process occurs during periods of fasting, starvation, or intense exercise and is highly endergonic. Gluconeogenesis is often associated with ketosis.




Regulation Gluconeogenesis cannot be considered to be simply a reverse process of glycolysis, as the three irreversible steps in glycolysis are bypassed in gluconeogenesis. This is done to ensure that glycolysis and gluconeogenesis are not operating at the same time in the cell, making it a futile cycle. Therefore, glycolysis and gluconeogenesis follow reciprocal regulation , that is, cellular conditions, which inhibit glycolysis, may in turn activate gluconeogenesis.


Glycogenolysis Glycogenolysis is the catabolism of glycogen by removal of a glucose monomer and addition of phosphate to produce glucose-1-phosphate. This derivative of glucose is then converted to glucose-6-phosphate, an intermediate in glycolysis. The hormones glucagon and epinephrine stimulate glycogenolysis




Regulation The key regulatory enzyme of the process of glycogenolysis is Glycogen phosphorylase: Phosphorylation --> activation Dephosphorylation --> inhibition


Glycogenesis Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen. This process is activated by insulin in response to high glucose levels, for example after a carbohydrate containing meal.



Cardiovascular System:

Cardiovascular System The main components of the human circulatory system are the heart, the blood, and the blood vessels

Systemic circulation:

Systemic circulation Systemic circulation is the portion of the cardiovascular system which carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart.

Pulmonary circulation:

Pulmonary circulation Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart.


Heart In the heart there is one atrium and one ventricle for each circulation, and with both a systemic and a pulmonary circulation there are four chambers in total: left atrium, left ventricle, right atrium and right ventricle

Blood Vessels:

Blood Vessels The Artery Arteries are muscular blood vessels that carry blood away from the heart.All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood. The Vein Veins function to return deoxygenated blood to the heart, and are essentially tubes that collapse when their lumens are not filled with blood




Capillaries Capillary The walls of capillaries are composed of only a single layer of cells, the endothelium. This layer is so thin that molecules such as oxygen, water and lipids can pass through them by diffusion and enter the tissues. Capillary Bed The "capillary bed" is the network of capillaries supplying an organ. The more metabolically active the cells, the more capillaries it will require to supply nutrients

Nervous System:

Nervous System The nervous system coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. Prominent parts of a nervous system include neurons and nerves, which are used in coordination. All parts of the nervous system are made of nervous tissue.

Nervous System:

Nervous System

Nervous System:

Nervous System Central nervous system The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Peripheral nervous system The PNS consists of all other nerves and neurons that do not lie within the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS.


Neuron Dendrites Soma (Cell Body) Axon Hillock Mylin Sheath Axon Schwann Cells Axon Terminals

Comparison between Nervous and Endocrine:

Comparison between Nervous and Endocrine Hormones are transported around (to their target organs) the body by the blood. Therefore hormonal responses are relatively slow compared with nervous responses. Many hormonal responses (e.g. growth) occur over relatively long periods of time. The main purpose of the Endocrine System is to maintain Homeostasis within the body (that is, to keep the internal environment constant/within balance), whereas the key function of the Nervous System is to receive and respond to stimuli . Generally, the endocrine system is controlled by the Nervous System (through the Hypothalamus, mediated by the Pituitary Gland).

End of Module 3:

End of Module 3

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