Khirsten Ravensbergen

Introduction

The nervous system works to maintain a steady body state and it controls the internal environment of the body. When one part of the nervous system gets damaged, for example the brain, the rest of the body will be affected and homeostasis will be disrupted. When we experience stimuli, our senses immediately send information to the central nervous system which will then respond by sending information to our muscles in order to keep our internal body at a steady state. For example, when we are cold our blood vessels constrict to save our heart and we start to shiver and this generates heat. Likewise, when we are too hot, our blood vessels dilate and our sweat glands become moist, producing sweat in order to release heat and cool down our body.

The Central Nervous System

Our brains are amazingly complex things; they set us apart from all other animals and they allow us to communicate through language and they also allow us to set up cultures and society. The three parts of the brain are the fore brain (sense of smell), the mid brain (vision), and the hind brain (balance). The central nervous system manages body activities by integrating incoming sensory information that comes from the peripheral nervous system; it is the control centre of the body.

The Peripheral Nervous System

The peripheral nervous system is a subsystem that communicates with the central nervous system. There are two subsystems: the afferent system which receives input through receptors and transmits it to the central nervous system, and the efferent system which carries signals to the muscle and glands. The afferent system is made up of five receptors: mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, and pain receptors. The efferent system consists of the somatic system and the autonomic system. The somatic system communicates with muscles and controls voluntary actions and the autonomic system communicates with smooth muscles and glands and is in control of involuntary actions such as digestion and sweat.

The peripheral nervous system is also responsible for our perception of pain. When stimulated, the substantia gelatinosa in the spinal cord produces a neurotransmitter that finds an injured part of the body and sends a signal to the brain resulting in the perception of pain. After the brain ‘sends’ pain, it releases natural painkillers, such as endorphins and enkephalins which create a feeling of pleasure or excitement. Drugs can also cause opioids, such as heroin or morphine, to attach to substantia gelatinosa neurons which causes a feeling of calm and prevents pain from being transmitted.

The Senses

Our body has five senses: vision, hearing, taste, smell, and touch. The nervous system plays a huge role in how our senses work in communication with our body. Vision is the most complex of the senses. Our eyes have photoreceptors in the retina that detect light and convert the light stimuli into nerve impulses that move the information to the vision centres in our brain.

Inside of the auditory canal, or the ear, sound waves strike the eardrum, which causes it to vibrate. This then causes vibrations in auditory ossicles which causes more vibrations in the membrane window of the cochlea and the fluid in the cochlea moves which causes a response in the hearing nerve so that we can hear.

The sensory hairs of taste receptors pass through the exterior pore of a taste bud and becomes exposed to the inside of the mouth, creating taste. Signals from taste receptors travel to the thalamus and to taste centres in brain where they get interpreted as to what taste they are.

We experience touch through touch receptors that are in our skin and other surface tissue. Most of our touch receptors are in our fingertips, lips, and tip of tongue.

Some sensory disorders such as sensory processing disorder (SPD) can make it more difficult to interpret information from sensory receptors. Injuries can also cause transmissions of signals to the brain to be blocked.

Body and Stress

When our bodies are stressed, we have a reduced blood flow to the body and more blood flow to the brain causing us to become irritable, nervous, overworked etc. When we are stressed out we also experience muscle tension, tiredness, increase in heart rate as well as respiration rate and sweat. Stress happens when a certain situation or situations causes our bodies to move away from homeostasis. Stress can be both good and bad. Good stress comes when we are excited or in love but when we have too much bad stress in our bodies then it can have harmful affects both physically and mentally.