Physiology of animal and man

A reflex arc is a neural pathway that controls an action reflex. A reflex arc represents a mechanism by which a physiological function is automatically managed or regulated. Reflex arcs can be found throughout the body ranging from skeletal muscles to smooth muscles in glands.

Chronic pancreatitis occurs most commonly after an episode of acute pancreatitis, and is the result of ongoing inflammation of the pancreas. In about 45% of people, chronic pancreatitis is caused by prolonged alcohol use. Other causes include gallstones, hereditary disorders of the pancreas, cystic fibrosis, high triglycerides and certain medicines. Damage to the pancreas from excessive alcohol use may not cause symptoms for many years, but the person may suddenly develop severe pancreatitis symptoms including severe pain and loss of pancreatic function resulting in digestion and blood sugar abnormalities.

Cholecystokinin (CCK), formerly called pancreozymin, is a digestive hormone released with secretin when food from the stomach reaches the first part of the small intestine (duodenum). It is the major hormone responsible for gallbladder contraction and pancreatic enzyme secretion.

The free fatty acids and monoglycerides form micelles that migrate towards the brush border membrane. The micelle permits fat components to be soluble in water. Because bile salts have a hydrophobic or water repelling region and a hydrophilic or water attracting region, the micelle is formed with bile salts arranged around the outside with hydrophobic ends facing inside and hydrophobic fatty acids, monoglycerides, phospholipids and cholesterol as well as the fat soluble vitamins A, D, E and K in the centre.

Steatorrhoea is a condition characterized by an increase in fat content in stools leading to the production of pale, bulky, offensive and loose stools. The underlying cause is a defect or alteration in the functioning of the digestive system. The pancreas makes enzymes involved indigesting food, so its damage means fewer enzymes are produced. Since pancreatic enzymes are particularly responsible for digestion of fat, fewer enzymes means less fat is digested. Fat tends to remain in the stools making them paler, more foul smelling than usual and difficult to remove by flushing.

Lipofuscin is the name given to finely granular yellow-brown pigment granules composed of lipid containing residues of lysosomal digestion. Lipofuscin or lipochrome is a wear and tear pigment since the number of its granules within the neurons increases with age. These granules are end products of intracellular peroxidation and polymerisation of unsaturated fatty acids. The precise function of lipofuscin is unknown.

It is the inability to move a group of muscles in one side of the body. When hemiplegia is caused by a stroke, it often involves muscles in the face, arms, and legs. In elderly individuals, strokes are the most common cause of hemiplegia.

Fatigue is a state of awareness describing a range of afflictions usually associated with physical and/or mental weakness though varying from a general state of lethargy to a specific work induced burning sensation within one's muscles.

An axon is a long branching cell structure that is unique to nerve cells. Axons are responsible for carrying information from the nerve cells to all the other cells of the body. The axon carries nerve signals away from the soma and also carries some types of information back to it. Interference with signals as they travel through the axons has been identified as a cause of certain degenerative neurological disorders.

They contain many structures that are critical to stop bleeding. They contain proteins on their surface that allow them to stick to breaks in the blood vessel wall and also to stick to each other. They contain granules that can secrete other proteins required for creating a firm plug to seal blood vessel breaks. Also, platelets contain proteins similar to muscle proteins that allow them to change shape when they become sticky.

The golgi apparatus is a stack of flattened compartments where molecules are packaged for delivery to other cell components or for secretion from the cell. It is present only in the cell body or soma of neuron. It is present close to the nucleus and is absent in axon and dendrites.

Erythrocytes, also known as red blood cells (RBCs), function to transport oxygen in the blood. Mammalian erythrocytes are typically shaped as biconcave disks that are flattened and depressed in the center with a dumbbell shaped cross section and a torus shaped rim on the edge of the disk. Oxygen transport is efficient because the cells have a flattened disc shape to increase surface area allowing rapid diffusion of oxygen, and they contain haemoglobin which absorbs oxygen in the lungs and releases oxygen in the rest of the body.

The axon hillock is a specialized domain of the neuronal cell body from which the axon originates. A nissl body also known as nissl or tigroid substance is a large granular body found in neurons, but it cannot be seen in the axon or axon hillock.