Neural control and coordination

Introduction

Control and coordination are the essential components of locomotion. Locomotion is a unique feature of many living organisms which occurs as a result of unintended and intended actions produced by our body systems. However, the underlying mechanisms of movement between the plants and animals differ. Animals can produce 2 major types of movements. They can either transfer their complete body from one place to the other or they can produce movement of individual parts of the body. On the other hand, plants are stationary while a slight movement can be observed despite they are intact. Plants growing tall and their developing branches is also a type of natural movement but animals do not grow as tall as trees. 

 

 

Intended and unintended movement 

Many types of movements in the animal`s body occur as a result of the bodily activities, for example, cows chewing the cud is a natural process rather than deliberate.  However, some are intentional movements, for instance,  animals migrating from one place to another, running, jumping, walking and playing. In order for the movement to be purposeful, systematic and coordinated, the nervous system is very important. Nevertheless,  control and coordination are the consolidated efforts of the nervous system, muscular system and the endocrinal system. In the human body, coordination and control are classified into  2 major types, Endocrinal coordination and control and the  Neural coordination and control. 

 

 

The nervous system 

The human nervous system is highly complex as it is well connected with each and every corner of our body. Some of our body systems working in coordination with the nervous system includes the muscular system, sense organs, and skeletal system. Our nervous system composed of millions of neurons capable to detect the sensory feelings such as  heat, cold, pressure and the sharpness of an object. To sense these feelings, we have a specialized cellular system in our body called the sensory-motor system ( a part of the nervous system). Our sensory nerves contain sensitive nerve tips that receive the stimuli from each and every part of the body. When a peripheral stimulus reaches the brain in the form of a signal, the brain responds by sending a message to the parts in action. This will help in initiating a movement such as lifting,  moving, hitting, kicking, standing or running.  Let us understand in detail how the nervous system functions and how it can produce movement and coordination necessary for our lives. 

 

 

Components of the nervous system

The nervous system is divided into the central nervous system and peripheral nervous system. The central nervous system is again subdivided into the brain and spinal cord. The brain has 12 pairs of cranial nerves coming out of the different parts of the brain. The spinal cord has 31 pairs of spinal nerves connected to the different levels of our backbone and limbs. On the other hand, the peripheral nerves are spread across the periphery ( all over the skin). Peripheral nerves have sensitive nerve endings spread very close to the layers of skin. Two types of peripheral nerves are sympathetic and parasympathetic nerves. These nerve endings will receive and convey signals from in and out of the body parts like hands, face and legs.

 

Components of nervous system

 

 

Human Brain

Covering layers of the brain( meninges)

The brain is a curd-like material, very soft and delicate. The protective layers surrounding the brain and spinal cord are called meninges. There are 3 layers of meninges, namely, dura mater, arachnoid mater, and pia mater. The cerebrospinal fluid found in the arachnoid space protects the brain from injury, shock and pressure.

 

The cerebrum

The human brain is the most amazing creation by the god. We have the largest brain of all vertebrates ( in proportion to their relative body size and weight). The human brain weighs about 1.5 kilograms which are about 2% of the total body weight. The brain is broadly divided into cerebrum or forebrain, midbrain, and the cerebellum or hindbrain.  The cerebrum is the major portion which makes up about  85% of the brain's weight. The brain has approximately 86 billion nerve cells (neurons) form the grey matter and the white matter.  Individual areas of the cerebrum perform specialized sensory functions like hearing, smell, taste, sight and so on. These are involuntary in nature as we cannot control them by personal efforts.  For example, we can’t control hunger, breathing and heart rate but we can very well control writing, walking, reading etc.

 

 

The Cerebellum

The cerebellum is mainly responsible for coordination, bodily balance, and control. It assists in bodily actions such as walking in a straight line, picking up a pencil, riding a bicycle, drawing a picture and sitting straight. 

 

Spinal cord

The spinal cord or spinal column is made up of many sub-divisions along its length. It contains as many as  31 segments including  8 cervicals (C),  12 thoracics (T), 5 lumbar (L), 5 sacral (S) , and 1 coccygeal (Co) segments. The spinal cord is mainly responsible for the movement of the body without the help of spinal impulses. An injury to spinal nerves causes paralysis (Permanent disability by losing complete control.)

 

 

Neurons

Neurons are the structural and functional units of the nervous system responsible for the proper functioning of the nervous system. They receive and send signals from in and out of the brain. They seem like long fibres, slender and branched at their axonal ends. As seen in the picture below, dendrite is the head or the cell body which is connected down to the axon.  At the terminal part of the axon, there are hair-like projections which receive electrical impulses from the axonal ends of another neuron with the help of neurotransmitters. Axons are covered by a protective sheath;myelin sheath which protects the axon from shock and external threats. Damage to the sheath can interfere with the passage of nerve impulse

 

 

Transmission of nerve impulses

An impulse is information transferred through axons in the form of electrical charges. Electrical conduction is aided by the neurotransmitters and the neurochemicals produced at the synaptic junctions. A synaptic junction is formed when the axonal end of one neuron joins with the dendrites of the succeeding neurons.  In order to pass a signal, neurotransmitters must cross the synaptic junctions. Many neurons join together to form a nerve and the whole nervous system is made up of an organized network of many cerebral and spinal nerves or neurons which are specialized in conducting information in the form of electrical impulses.

 

Neuron and synaptic junction- image from wiki commons and freepik

 

 

Mechanism of Reflex Actions

Reflex is an instant and natural action in response to a surprise provocation from the outside environment.  What if a dog suddenly starts running ( stimulus) behind you, naturally you will display a fight or flight response as your brain senses the threat in the form of a running dog. To react to the apparent threat, you will start running which is nothing but the reflexive action.  Pulling your hand off the lamp, feeling like a watery mouth when you see a delicious dish, etc. are some of the examples of reflexive actions. These actions are instant and automated rather than systematic and prolonged. 

 

Control and coordination through Reflex Arc

Our coordination and control occur through a path called the reflex arc. A reflex arc process through a sequence of flow of information or signals. Our nervous system quickly responds to the harmful stimulus from an external source in a sudden and unexpected manner. The process begins with the identification of sensory stimuli from our sense organs, and then the stimulus is passed to the brain via spinal nerves. The brain quickly responds to the incoming stimuli from the spinal column in the form of response. A response travels to the peripheral muscles and bones through nerves to prompt necessary action. For example, if our finger comes in contact with a heated lamp, the nerves in the affected area send a signal to the brain and the brain generates a message to quickly withdraw the hand.

 

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