What is Neurology?

Neurology is the subspecialty of medicine that deals with the scientific study of the structure & functioning of the nervous system including the diagnosis and management of its maladies. A Neurologist is the physician specialized in this field.

Nervous System

Nervous system encompasses a group of several highly advanced and interconnected structures in the body that organize myriad body functions and include;

  • Brain
  • Spinal cord
  • Muscles
  • Nerves
  • Nerve roots etc.

Anatomical (structural) organization of the Nervous system

The different neurological structures are lumped under two categories;

  • Central Nervous System (CNS) &
  • Peripheral Nervous System (PNS)
The brain & spinal cord are part of the CNS, and all the remaining structures belonging to the nervous system are grouped under PNS. Strictly speaking Muscles are not neurological structures (in the sense they do not contain nerve cells, nerve fibers etc) but are generally considered as part of the nervous system because of their close association in functioning.

CNS (central nervous system)

Brain:

Brain possesses the ultimate control of your body. It is a vital organ, means its proper functioning is necessary for our survival and/or quality of life. It directly or indirectly controls other vital and non-vital organs of the body like heart, lungs, liver, kidney, bowel/bladder etc and maintains the well being of an individual. Adult human brain weighs about 1.3 kg to 1.5 kg, and it is housed in-side of a bony structure called as skull.

Brain is further divided in to regions called as;

  • Cerebral hemispheres
  • Diencephalon (including thalamus, hypothalamus etc)
  • Basal ganglia (caudate nucleus, putamen, globus pallidus etc)
  • Brain Stem
  • Cerebellum
Cerebral hemispheres:

These constitute the bulky upper portion of the brain and include frontal parietal, temporal and occipital lobes. They control our cognitive functions, awareness, voluntary body movements, general sensory perception, all special senses etc. The limbic system of temporal lobe controls the emotional aspects of our thinking. Neurology disorders like stroke, dementias etc affect this area of brain frequently.

Diencephalon (including thalamus, hypothalamus etc):

They mostly control the autonomic functions like hunger, thirst, body temperature etc. Stroke, tumors are some of the neurology conditions that may affect this area of the brain.

Basal ganglia:

These structures contribute to motor control of the body. A familiar neurological disorder Parkinsons disease results due to certain neurochemical imbalance in this region of the brain.

Brain Stem:

This is the lower portion of brain and consists of midbrain, pons & medulla from above downwards. In general the motor impulses descend and the sensory impulses ascend through the brainstem. Brainstem also boasts of the presence of vital centers like respiration (breathing) and cardiovascular system (controlling blood pressure, heart function etc). The reticular activating system that controls the sleep and wakefulness is also partly housed in the brainstem. All the twelve cranial nerves, but the first & second take exit from the brainstem (see later).

Neurology disorders like stroke, multiple sclerosis, tumors can involve this part of the brain.

Cerebellum:

Its main role is to coordinate the body movements and maintain balance. Various neurology conditions like stroke, multiple sclerosis etc can affect this region.

Spinal cord:

This is not part of the brain but is the continuation of brain at the lower end of skull where brainstem ends and transforms to the spinal cord. It is an elongated structure located in your back and extends from the upper neck to the lumbar region in the midline. Spinal cord is contained in spinal canal formed by vertebral bones. The length is about 45 cm (18 inches) in adults.

Spinal cord is connected with structures named as spinal nerves through which sensory input enters and motor out put exits the spinal cord. Spinal cord also contains certain autonomic centers connected with the bowel, bladder and sexual functioning.

Autonomic nervous system:

This is distributed both in the central & peripheral nervous systems. It controls your involuntary body structures & functions related with heart, lungs, gastrointestinal tract, urinary bladder, sexual function etc.

PNS (peripheral nervous system)

Cranial nerves:

There are twelve pairs of cranial nerves that control the sensory, motor and autonomic functions of head, face and neck region including special senses like vision, hearing, smell, taste and they all except the first & second take exit from the brainstem. The first cranial nerve is connected with the temporal lobe & second one with the occipital lobe. The 2nd cranial nerve (optic nerve or nerve of vision) is actually a continuation of the brain, so considered as a part of the CNS rather than PNS.

Peripheral nerves:

These are the structures that carry motor and sensory impulses from and towards spinal cord respectively e.g. ulnar nerve. Neurology diseases like carpal tunnel syndrome, peripherl neuropathy result from damage to these structures and frequently encountered by a neurologist.

Neuromuscular junction:

This is the microscopic region where the electrical impulses from the nerve fibers enter a muscle. Neurology condition like Myasthenia gravis can affect this region.

Muscles:

Skeletal (voluntary) muscles like triceps or biceps are under your control. Involuntary muscles like heart and muscles of gastrointestinal tract, urinary bladder are not under voluntary control.

Structures closely associated with CNS

CSF (Cerebrospinal fluid):

This is the fluid that circulates through and around the brain & spinal cord. It is the same liquid which is removed during a procedure called lumbar puncture or spinal tap. This fluid acts as a buffer to the brain & spinal cord during injuries and also provides some nourishment to adjacent nervous structures.

Meninges:

These structures cover and protect the brain & spinal cord. This three layered structure consists of dura, arachnoid & pia membranes from out side to inside. Neurology conditions like meningitis affect these structures.

How does the Brain Work? & How does the nervous system function as a unit?

Being top in the hierarchy of any system is not an easy job always. The organizational abilities at this level will be highly demanding, challenging, and daunting to say the least. Our nervous system, especially the central nervous system (brain & spinal cod) occupying such a position is expected to deliver in this line.

Good news! In fact they do deliver very well what is expected from them. We human beings are fortunate that our nervous system is gigantically advanced as compared to other animals on this planet. Multi-task abilities, executive level of thinking, very high-level organization etc are the norms of human brain. The spinal cord also ably supports the brain in many fronts.

The functional units of the nervous system are called as neurons (nerve cells). There is additional glial tissue (astrocytes, oligodendrocytes, microglia etc) that has supporting, nourishing and protecting roles.

The question is; how all these unfathomable depth of sophistication and preciseness is endowed to human nervous system?

The credit goes to billions of neurons, the most important functioning units of the nervous system. Human brain is estimated to possess nearly 100 billions of neurons!

The neurons dispatch nerve impulses (electric signals) through elongated fibrous structures called as axons and receive input signal via shorter fibrous structures called as dendrites. Certain highly organized ionic movements (sodium, potassium, calcium etc) taking place across the cell membrane of neurons and its fibers produce & propagate nerve impulses which are used for communication within the nervous system (brain & spinal cord) as well as between the nervous system and other parts of the body.

As mentioned above, the brain and the spinal cord possess all or most of the higher organizational properties of the nervous system. Various sensory inputs from the body & environment reach them, they process these inputs meticulously & methodically in a manner befitting to highly intelligent animals of the caliber of human beings, and then generate appropriate new nerve signals and dispatch these signals back to the body so that the body responds properly & promptly to the external stimulus. Some of these neural inputs and out puts are also stored in the brain as what we call ‘memory’ which will be used for future purposes.

The neurons within the central nervous system (brain and spinal cord) are also interconnected through a rich and monumentally sophisticated network of axons and dendrites and this catapults the organizational abilities of human brain to an altogether unbelievable level!

Summary

We human beings are lucky to be blessed with a nervous system that is so highly developed and advanced. Our awareness, cognitive abilities, sensory/motor perceptions, and countless other body functions are directly or indirectly controlled by this amazing system.

So it is crystal clear that the health & well being of our nervous system is of paramount significnce. As pointed above Neurology is the specialized field of medicine that handles the ill-health of the nervous system and a Neurologist is the medical specialist who will assist with the management of your neurological illness.

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