The Brain - This is in the central part of the nervous system. The brain helps control one's behavior. It will receive and send messages for the rest of the body through the spinal cord. These are the three parts of the brain.
1. Cerebrum- It is the biggest part of the brain that controls higher processes such as speaking, reasoning, and memorizing and the 5 senses - smell, touch, taste, sight, and hearing.
2. Cerebellum- This controls voluntary actions in the body such as talking, eating, singing, swimming, etc.
3. Medulla- This controls involuntary actions such as choking, breathing, heart rate, etc.
The Spinal Cord - The spinal cord is our body's main nerve. It is about 18 inches, or 45 cm long, and as thick as a finger. It extends from the base of the brain and runs down our spine. Our spinal cord acts as the link between the brain and the nerves that are spread throughout our body. From each side of the spinal cord are 31 pairs of spinal nerves that carry messages to and from the brain. The link of bones that protect the spinal cord are called the vertebrae.
The Nerves- This part of the system is called the peripheral nervous system. This is a pathway to the brain for the five senses. The nerves form messages to send to the brain through the spinal cord.
Action potentials- Rapid transmission of messages-The above example of the squid action potential was patterned after a measured action potential shown in West's Medical Physics. The approximate time intervals shown were scaled from time markers on the experimental trace. The times seem very short to me. I thought the recovery time to rest potential was more like 100 msec.
The action potential sequence is essential for neural communication. The simplest action in response to thought requires many such action potentials for its communication and performance. For modeling the action potential for a human nerve cell, a nominal rest potential of -70 mV will be used.
Reflex Arc (Simple sematic function) and autonomic function-
reflex arc is the neural pathway that mediates a reflex action. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs.
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These maintenance activites are primarily performed without conscious control or sensation. The ANS has far reaching effects, including: heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition - (the discharge of urine), and erection. Whereas most of its actions are involuntary, some ANS functions work in tandem with the conscious mind, such as breathing. Its main components are its sensory system, motor system and the enteric nervous system.
What can we sense?-
The human body is a beautifully engineered structure. The body has a general plan. We all have arms, legs, a head, ears, and eyes on the outside of our bodies. We also have similar parts on the inside of our bodies. We all have one heart, two lungs, one brain, two kidneys, and one stomach. Understanding and learning about the human body is a complicated subject. If you just take an organ or system and emphasize its function, you must tell students how the system fits into the rest of the body's functions.
You can introduce the parts of the body, both internal and external, by using the organs that allow humans to operate their senses. The nervous system controls the actions and sensations of all the parts of your body by using a complex network of nerves, which carry electrical signals to and from the brain. The brain and spinal cord compose the central nervous system, acting as the central clearing house. One part of your nervous system controls your body's relationship to the external environment and another part controls your body's internal organs. The human body has five major senses which operate to gather information from the world around us, sight, hearing, smell, taste, and touch. Any stimulus to one of the sense areas is detected by sensory nerves and is sent to the brain for interpretation.
The eye acts like a camera. Human vision is stereoscopic, which means seeing in three dimensions. When we look at objects two slightly different images are transmitted to the brain, and are merged so the brain can interpret the image that we see. This allows us to see objects which stand away from the background, not flat like you see in a photograph.
The ear is specially made to receive sound waves that are sent out by vibrating objects and converts them into sensations we call sound.
The nose contains the nostrils and organs of smell. The stimulus that excites smell is chemical, for example onion and garlic give off different chemical sensations.
The tongue is the organ that controls taste. Taste is also a chemical stimulus. Things to be tasted must touch the tongue, sometimes, taste become combined with smell because of the connection between the mouth and the back of the nose.
Touch is created by stimulating the skin through the sensations of touch, pressure, pain, heat and cold.
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