While neurons are the building blocks of the body’s communication system, it is the networks of neurons that allow signals to move between the brain and body. These organized networks, composed of up to one trillion neurons, make up what is known as the nervous system. There are two parts to the nervous system. The central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which is composed of nerves and nerve networks throughout the body. One of the many functions of the nervous system is transmission of nerve impulses. A nerve impulse is essentially an electrical stimulus that travels over the cell’s membrane. It passes through the axons and dendrites of the neurons. It travels via the dendrites from the skin and then reaches the cell body, axon, axon terminals and the synapse of the neuron. So you can see that there is a lot going on in the nervous system. The brain is made up of several parts. Each part has a function as well. There are also neurotransmitters in the nervous system that are essentially chemicals that transmit signals across a synapse from one neuron to another neuron. They are very important for sending signals throughout the body. The peripheral system can further be divided into two different systems, the somatic nervous system and the autonomic nervous system. For the somatic nervous system, the things that it is responsible for are transmitting sensory communications and is responsible for voluntary movement and action. The autonomic nervous system is responsible for controlling involuntary functions such as certain aspects of heartbeat, respiration, digestion and blood pressure. It is also related to emotional responses such as sweating and crying. The autonomic system can then be further subdivided into two subsystems known as the sympathetic and parasympathetic systems. The sympathetic nervous system control’s the body’s response to emergencies. This is known as the fight or flight response. The parasympathetic nervous system comes in after a crisis or danger has passed and helps to calm and relax the body.
The regulatory behavior that I chose to write about is hunger, so let’s take a closer look at what is involved with the very simple feeling of hunger. “Different species use different eating strategies.” (Kalat, 2013). The size of the animal can have a very distinct impression as to the amount and function that hunger will have on them. An example from our text is that of a snake. A snake may have a very large meal and then not eat for months. A bird has to be careful not to eat too much or it may interfere with its ability to fly. The digestive system is a complex system that basically breaks down what we eat into smaller more manageable pieces so that the body can absorb the cells better. Food actually doesn’t stay in the stomach for very long. It is then moved from the stomach to the small intestine. Where enzymes digest fats, carbohydrates and proteins. “It is also the site for absorbing digested materials into the bloodstream. The blood carries those chemicals to body cells that either use them or store them for later use. The large intestine absorbs water and minerals and lubricates the remaining materials to pass as feces.” (Kalat, 2013). “How does your brain decide when you should eat and how much? Hunger depends on the contents of your stomach and intestines, the availability of glucose to the cells and your body’s fat supplies, as well as your health and body temperature.” (Kalat, 2013). The Hypothalamus is considered to be the master area for control of appetite. The arcuate nucleus of the hypothalamus has one set of neurons sensitive to hunger signals and another set of neurons sensitive to satiety signals. One of the hormones that is also called the “hunger hormone” is called Ghrelin. It lives in the gastrointestinal tract and functions as a