Micturition Disorders and Neurogenic Bladder

Micturition:

The process of voiding urine is called micturition. The urine is formed in the kidneys and collected into the urinary bladder. The urinary bladder is connected to kidneys through a pair of ureters. When a pressure of accumulated urine develops in the urinary bladder, we have a desire to urinate. An accumulation of 150 ml to 200 ml of urine activates the nerve endings in the muscular wall of the urinary bladder. The micturition is a reflex act controlled and inhibited by the higher centers in our brain. The act leads to the contraction of the muscular coat of the urinary bladder and relaxation of sphincter muscles. The urinary bladder is controlled by the pelvic nerves and the synaptic fibers from the hypogastric plexus. It may be voluntarily assisted by the contraction of abdominal muscles by increasing pressure in the abdominal cavity. The voluntary contraction of abdominal muscles exerts pressure on the visceral organs and in turn on the urinary bladder and helps in emptying of the bladder.

Neurogenic Bladder:

As stated above, the urinary bladder activity is controlled by the pelvic nerves and the sympathetic nerve fibers from the hypogastric plexus. A condition may arise due to a variety of causes leading to an interruption of the nerve messages between the brain and the urinary bladder. Due to lack of dynamic control over the muscles of the urinary bladder, the bladder fails to store or release the urine properly. Spinal cord injury due to some fatal accident, brain tumor, stroke, diseases such as multiple sclerosis or diabetes mellitus and congenital disorders could be the cause of neurogenic bladder.

There may be varied symptoms of neurogenic bladder depending on the lesion and the site of the injury and severity of injury. The patient may express inability to store the urine, excessive frequency of micturition and incontinence. All this is caused by overactive urinary bladder or a weak sphincter (outlet controlling muscles). On the other hand a weak urinary bladder or an over tight sphincter may lead to retention of urine and difficulty in urinating. Though the problem is associated with the urinary system but the cause is neurological and only a neurologist could help the patient in the right perspective. Renal function tests and ultrasound examination is must to evaluate the status of kidneys. A thorough evaluation is needed to ascertain the cause of neurogenic bladder disorder. Urodynamic testing with video x-rays and uroflometry should be carried out to evaluate the extent of emptying of the urinary bladder.

Altered Physiology and Diseases of the Muscles

The skeletal muscles or flesh are essential for the motor functions as well as the shape and features of our body. The muscular atrophy (shrinkage of muscle mass) may lead to a variety of diseases of the muscles. These diseases are distinguished with respect o the site of origin of a disorder as mentioned below:

1. Origin in motor neurons: Polymyelitis, progressive muscular atrophy

2. Origin in the nerve fibers: Polyneuritis

3. Origin in the myoneural junction: Myasthenia gravis, myotonia congenital, and

4. Origin in the muscle only: Primary muscular dystrophy.

All voluntary muscle have innervation by motor neurons. The muscle fibers are composed of myofibrils and these fibrils appear to be the ultimate functional units of the muscle and have alternate light and dark bands. The contractile protein of the muscle is called actomycin (AM) and is composed of actin and myosin. The actomycin is considered to be the structural protein of the resting myofibrils and contain many enzymes necessary the muscle metabolism. The organic phosphate compound called adenosine triphosphate (ATP) is an energy rich compound and is attached to actomycin of myofibrils. The neuronal spark of the motor neurons fires the adenosine triphosphate-actomycin linkage and breaks it. The adenosine triphosphate (ATP) is liberated and its breakdown provides energy for the muscle contraction. During contraction of the muscle, the actin threads could be shortened to 40% of its original relaxed phase size. The physiology of muscle contraction involves a series of molecular interactions and rearrangements within the complex structure of actin, myosin, and adenosine triphosphate.

The change in the functions of any part of the above cited metabolic pathway may lead muscle weakness. The microscopic examination of muscle biopsy may help to achieve a proper diagnosis. There muscle biopsy could reveal an involvement of a whole bundle of muscle fibers in the cases with neurogenic origin. I cases affected by primary muscular dystrophy only some the fibrils may be involved. The ultrastructural study of the muscle biopsy by a transmission electron microscope is always helpful in achieving an accurate diagnosis of the diseases of the muscles.

Physiology of Muscle Contraction

The essential function of the skeletal muscle is contraction and relaxation in response to a command from a motor neuron. The muscle is very unique organ and is capable converting stored chemical energy into mechanical energy through metabolic processes. The skeletal muscles constitute from 40 to 45 percent of the body weight in an adult. There are 434 voluntary muscles in our body and about 250 million muscle fibers constitute these muscles. The muscle cells or sarcomeres are very complex in structure, metabolism and functions.

All voluntary muscle have innervation by motor neurons. The muscle fibers are composed of myofibrils within the sarcoplasm. The myofibrils appear to be the ultimate functional units of the muscle and have alternate light and dark bands. The contractile protein of the muscle is called actomycin (AM) and is composed of two components: (1) actin and (2) myosin. The actomycin is considered to be the structural protein of the resting myofibrils and contain many enzymes necessary the muscle metabolism. The organic phosphate compound called adenosine triphosphate (ATP) is an energy rich compound and is attached to actomycin of myofibrils. The neuronal spark of the motor neurons fires the ATP-AM linkage and breaks it. The ATP is liberated and its breakdown provides energy for the muscle contraction. During contraction of the muscle, the actin threads could be shortened to 40% of its original relaxed phase size. Physiology of muscle contraction involves a series of molecular interactions and rearrangements within the system composed of actin, myosin, and adenosine triphosphate.

Role of Grey Matter and White Matter in Our Nervous System

Our nervous system could be studied under two main headings for quick understanding: (1) The Central Nervous System (CNS) or Cerebrospinal Nervous System and (2) The Autonomic Nervous System. The autonomic nervous system includes the sympathetic nervous system and parasympathetic nervous system.

The central nervous system includes the brain and the spinal cord, and the nerves arising out from these. The nerves arising from the brain and the spinal cord are called peripheral nerves. The nervous tissue is one of the four elementary tissues of our body and commands the sensory and motor functions of our body in addition to intellect, emotions and memory functions. The nervous tissue is composed of nerve cells, dendrites, nerve fibres and nerve endings. The composite mass of nerve cells is called grey matter. The grey matter is found in the cortex of the brain, inner part of the spinal cord and cerebral ganglia. The role of the grey matter is the processing of the sensory and motor information, control of emotions, memory and intellect. The control of emotions, memory and intellect is associated with the growth and development of the brain. The nerve fibres and or axons constitute the white matter. The white color of the sheath of fatty matter called the myelin sheath covering the axons or nerve fibres is the reason behind the nomenclature as white matter. The white matter is the major component of the central portion of cerebral part of brain. The myelin sheath serves to protect, nourish and insulate the nerve fibres from each other. A nerve cell along with its dendrites, nerve fibre or axon and nerve endings is called a neuron as depicted in the figure-1 below:

Figure-1: Components of a Neuron

There are two types of neurons in our body. The neurons which carry impulses out from the brain to the tissues are called efferent neurons and the neurons which carry impulses to the brain from the tissues are called afferent neurons. Efferent neurons which supply impulses to the muscles and produce movement are called motor neurons and which supply impulses to the glands and produce secretion are called secretory neurons. Afferent neurons are also known as sensory neurons since these help us to assess a feeling of touch, pain and heat or cold.

Quick Tips on the Surface Anatomy of Our Body

Our own body is a live specimen for understanding the surface anatomy of human body. Knowledge of surface anatomy may help us to understand the diagnostic terms used by a physician or surgeon. The physical examination parameters of a patient are recorded with reference to certain landmark points which are universally understood. By inspection, palpitation, percussion and auscultations a physician or surgeon studies condition of his/her patient to arrive at a diagnosis. The position of many internal structures and organs is described in relation to various bony points termed as landmark points.

There are some land mark points of surface anatomy of the head; like longitudinal fissure, superior longitudinal sinus, central sucus or fissure of Ronaldo, mastoid processes ete. There are anterior and posterior triangles of neck formed by sternomastoid muscle. In the trunk many of the organs are being described in relation to their surface anatomy. The apex beat of the heart can be heard in the fifth intercostal space, 3¹/₂ inches from the midline. The abdomen is divided into 9 parts by four imaginary lines (two vertical and two horizontal). These 9 parts have been depicted in the figure-1 below:

Figure-1: Abdominal Regions (1: Right Hypochondriac Region, 2: Epigastric Region, 3: Left Hypochondriac Region, 4: Right Lumbar Region, 5: Umbilical Region, 6: Left Lumbar Region, 7: Right Iliac Region, 8: Hypogastric, 9: Left Iliac Region.

The liver occupies parts of the right hypochondriac and epigastric areas, and extends transversely into the left hypochondriac region and also occupies a part of the right lumbar region. The lungs and the heart occupy the thoracic cavity and are well secured there in the protective bony cage. The spleen lies on the left side beneath the ninth, tenth and eleventh ribs. The left kidney lies between the eleventh thoracic to the third lumbar vertebra. The right kidney is slightly lower as its upper pole touches the lower part of the liver.

The rectus abdominus could be felt along each side of the middle line of the abdomen. The umbilicus lies on level with the disc between the third and fourth lumbar vertebrae. The stomach lies in the upper and left aspect of the abdomen, partly behind the lower ribs and cartilages. The fundus of the stomach reaches as high as the fifth left intercostal space. The gall bladder projects slightly from the costal margins at the level of the ninth right costal cartilage. The pancreas lies at the back of the abdominal cavity across the first lumbar vertebra. The aorta passes through the common iliac arteries in front of the fourth lumbar vertebra. The caecum is present on the right side and the commencement of the sigmoid fissure of the colon lie respectively in the right and left iliac fossae.