Write a note on Spinal Cord?

 Spinal Cord

The spinal cord is in fact a tubular bundles of nerves. It starts from brain stem and extends to lower back. Like, brain, spinal cord is also covered by meninges. The vertebral column surrounds and protect spinal cord.

Spinal Cord

The outer region of spinal cord is made of white matter (containing myelinated axons). The central region is butterfly shaped that surrounds the central canal. Its made of grey matter (containing neuron cell bodies).

31 pairs of spinal nerves arise along spinal cord. These are " Mixed Nerves" because each contains axons of both sensory and motor neurons.

At the point where a spinal nerve arises from spinal cord, There are two roots of spinal nerve.

•  The dorsal root contains sensory axons and ganglion where cell bodies are located.
• The ventral root contains axons of motor neurons.

Functions:

• It serves as a link between body parts and brain. Spinal cord transmits nerve impulses from body parts to brain and from brain to body parts.
• Spinal cord also acts as coordinator, responsible for some simple reflexes.

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Who is the largest part of brain & write its part?

 Brain

Forebrain is the largest parts of brain. It is most highly developed in humans.

FOREBRAIN

Parts:

There three parts of forebrain.

• Thalamus
• Hypothalamus
• Cerebrum

Thalamus:

                    Lies just below the cerebrum. It serves as a relay center between various parts of brain and spinal cord. It also receives and modifies sensory impulses (except nose) before they travel to cerebrum. Thalamus is also involved in pain perception and consciousness (sleep and awakening).

Hypothalamus:

                                Lies  above midbrain and just below thalamus. In humans, it is roughly the size of  an almond. One of the most important functions of hypothalamus is to link nervous system and endocrine system. It control the secretions of pituitary gland. It also controls feelings such as rage, pain, pleasure and sorrow.

Cerebrum:

                      It is the largest parts of forebrain. It controls skeletal muscles, thinking, intelligence and emotions. It is divided into two cerebral hemisphere.

Cerebral hemisphere:

                                          The anterior parts of cerebral hemisphere are called Olfactory bulbs which receive impulses from olfactory nerves and create the sensation of smell. 

Upper layer: 

                        The upper layer of cerebral hemispheres i.e. cerebral cortex consists of grey matter. The grey matter of nervous system consists of cell bodies and non myelinated axons.

Lower layer:

                          This layer consists of white matter. The white matter of nervous system consists of myelinated axons.

Cerebral cortex has large surface area and is folded in order to fit in skull. It is divided into four lobes.

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Explain Neuron & Write three classification of nerve.

 Neuron

Nerve cell or neuron is the unit of the nervous system. The human nervous system consists of billions of neurons plus supporting cell. Neuron are the specialized cells that are able to conduct nerve impulses from receptors to coordinators and from coordinators to effectors. In this way the communicate with each other and with other types of body cell.

Location:

                   The nucleus and most of the cytoplasm of neurons is located in the cell body. 

Dendrites & Axons:

                                          Different processes extend out from the cell body. These are called dendrites and axons.

Dendrites conduct impulses towards cell body and axons conduct impulses away from the cell body.

Schwann cells:

                              Schwann cells are special neurological cells located at regular intervals along axons, In some neurons Schwann cell secrete fatty layer called myelin sheath.

Nodes of Ranvier:

                                   Between the areas of myelin on an axon,  there are no myelinated points called Nodes of Ranvier. 

Saltatory: 

                     Myelin sheath is an insulator so the membrane coated with this sheath does not conduct nerve impulse. In such impulses are called saltatory (jumping) impulses. This increases the speed of nerve impulse.

On the basis of the function, neuron are of three types.

• Sensory neurons
• Interneurons
• Motor neurons

Sensory Neuron:

                                  Conduct sensory information (nerve impulse) from receptors towards the CNS. Sensory neurons have on dendrite and one axon.

Interneuron:

                          From brain and spinal cord. They receive information, interpret them and stimulate motor neurons. They have many dendrites and axons.

Motoneuron:

                          Carry information from interneurons to muscle or glands (effectors). They have many dendrites but only one axon.

Nerve

 A nerve means the union of several axons that are enveloped  by covering made of lipid.

Classification:

• Sensory nerve
• Motor nerve
• Mixed nerve

Sensory nerve:

                              Contain the axons of sensory neurons only.

Motor nerve: 

                           Contain the axons of  motor neurons only.

Mixed neuron:

                              Contain the axons of both i.e. sensory and motor neurons.

Write down the steps of functionality of kidney.

 Functioning of kidney

The main function of kidney is urine formation, which takes place in three steps.

• Pressure Filtration
• Selective Reabsorption
• Tubular Secretion

Functioning of kidney 

Pressure Filtration:

                       When blood enters the kidney via the renal artery, it goes to many arterioles, and then to the glomerulus . The pressure of blood is very high and so most of the water, salt, glucose and urea of blood is forced out of glomerulus capillaries. This material passes into the Bowman's capsule and is now called Glomerulus Filtrate.

Selective Reabsorption:

                                               The second step is the selective reabsorption. In this step about 99% of the glomerulus filtrate is reabsorbed into the blood capillaries surrounding renal tubule. It occurs through osmosis, diffusion and active transport. Some water and most of the glucose is reabsorbed from the proximal convoluted tubule. Here, salts are reabsorbed by active transport and then follows by osmosis. The descending limb of loop of Henle allows the reabsorption of water while the ascending limb of loop of Henle allows the reabsorption of salts. The distal convoluted tubule again allows the reabsorption of water into the blood.

Tubular Secretion:

                                      The third step is tubular secretion . Different ions, creatinine, urea etc. are secreted from blood into the filtrate in renal tubule. This is done to maintain blood at normal pH (7.35 to7.45).

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Define urine & Explain osmoregulatory function of kidney.

 Urine

The filtrate present in renal tubules is known as urine. It moves into collecting ducts and then into pelvis.

Osmoregulatory function of kidney

Osmoregulation:

                                  Is defined as the regulation of the concentration of the water and salt in blood and other body fluids. Kidney plays important role in osmoregulation by regulating the water fluids whereas excess intake of water dilutes them.

Osmoregulation of kidney

Hypotonic:

                       When there is excess water in body fluids, kidney from dilutes (Hypotonic) urine. For this purpose, kidney filter more water from glomerulus capillaries into Bowman's capsule. Similarly less water is reabsorbed and abundant dilute urine is produced. It brings down the volume of the body fluids to normal.

Hypertonic:

                        When there is shortage of water in body fluids, kidney filter less water from glomerulus capillaries and the rate of reabsorption of water is increased. Less filtration and more reabsorption of water produce small amount of concentration (hypertonic) urine. It increases the volume of body fluids to normal. This whole process is under hormonal control.

Hypotonic & Hypertonic

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Why Kidney Stone happen & what is Renal Failure?

 Kidney Stone

When urine becomes concentrated, crystals of many salts eg calcium oxalate, calcium and ammonium phosphate, uric acid etc. are formed in it. Such large crystals cannot pass in urine and form hard deposits called Kidney Stone.

kidney stones

Most stones start in kidney. Some may travel to ureter or urinary bladder.

Causes:

               The major causes of kidney stones are age, diet (containing more green vegetables, salts, vitamins C,D), recurring urinary tract infection , less intake of water, and alcohol consumption.

Symptoms:

                      The symptoms of kidney stones include severe pain in kidney or in lower abdomen, vomiting, frequent urination and foul-smelling urine with blood and pus. 

About 90% of all kidney stones can pass through the urinary system by drinking plenty of water. In surgical treatment, the affected area is open and stones are removed.

Lithotripsy:

                       Lithotripsy is another method of removal of kidney stones. In this methods, non electrical shock waves from outside are bombarded  on the stone in the urinary system. Waves hit the dense stones and break them. Stones become sand-like and are passed through urine.

Kidney(Renal) Failure

Kidney failure means a complete or partial failure of kidneys to function.

Renal Failure

Causes:

               Diabetes mellitus and hypertension are the leading causes of kidney failure. In certain cases, sudden interruption in the blood supply to kidney and drug overdoses may also result in kidney failure.

Symptoms:

                       The symptoms of kidney failure is the high level of urea and other wastes in blood, which can result in vomiting, nausea, weight loss, frequent urination and blood in urine. Excess fluids in body may also cause swelling in legs, feet face and shortness of breath.

Treatment:

                       The kidney failure is treated with dialysis and kidney transplant.

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Write a note on Dialysis.

 Dialysis

Dialysis means cleaning of blood by artificial ways.

Methods:

                There are two methods of dialysis.

1. Peritoneal Dialysis
2. Haemo Dialysis

Peritoneal Dialysis:

                                        In this type of dialysis, the dialysis fluid is pumped for a time into the peritoneal cavity which is the space around gut. This cavity is lined by peritoneum. Peritoneum contains blood vessels. When we place dialysis fluid in peritoneal cavity, waste materials from peritoneal blood vessels diffuse into the dialysis fluid, which is then drained out. This type of dialysis can be performed at home, but must be done every day.

Haemodialysis:

                                In haemodialysis, patient's blood is pumped through an apparatus called Dialyzer. The dialyzer contains long tubes, the walls of which act as semi-permeable membranes. Blood flows through the tubes while dialysis fluid flows around the tubes. Extra water and wastes moves from blood into the dialysis fluid. The cleansed blood is then returned back to body. The haemodialysis treatments are typically given in the dialysis center.

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