Together, the brain, spinal cord and all the nerves in the body constitute the nervous system. The nervous system is vital for all biological processes, since it allows different parts of the body to communicate with the brain and vice versa. This means that nerves and the brain are responsible for touching a hot surface with a finger, sensing that it is painfully hot, recognizing that it is too hot, recoiling the finger away from the hot surface, and forming a memory associating hot surfaces with pain, not to mention controlling processes over which you have no control (such as your heart pumping). In this article, we’ll discuss the basic concept of nerves and the human brain, including the major nerves in the body and the main areas of the brain.
What are nerves and what are they made of?
Nerves are a special type of cell (actually, several types) called neurons. The contain all of the things that cells need to do their jobs, like a nucleus, mitochondria, ribosomes, and cell membrane, but their shape is quite different from other cells. In general, a nerve cell has three parts: a roundish or pyramid-shaped soma, where the nucleus is found, several small branches coming off of the soma called dendrites, and one long, thin branch called the axon. Nerve cells use these different parts to communicate with the brain, muscles and other nerve cells through electrical impulses.
Sensory nerves receive information from stimuli and send that information to the brain. This could include information about temperature, pressure, balance, pain, etc. Motor nerves send impulses from the brain to muscles to cause them to move. Finally, Relay nerves are “intermediaries” which send information from one nerve to another.
Not all parts of your body have the same makeup for these types of nerves. For example, the areas of your body which contain the most sensory nerves are your fingertips and face, especially your lips. Other areas, like the legs, have a lower density of sensory neurons and more motor neurons.
What are the major nerves in the human body?
All nerves in the body either originate in the brain (cranial nerves) or from the spinal nerves in the spinal cord. There are twelve pairs of cranial nerves: olfactory (sense of smell), optic (sight), oculomotor (eye movements), trochlear (eye movement), abducens (eye movement), trigeminal (facial sensation, jaw movement), facial (facial movements and taste), vestibulocochlear (sound and balance), glossopharyngeal (throat muscles, sound, and taste), vagus (heart and digestive tract), accessory (neck movement), and hypoglossal (tongue movements).
The spinal nerves are denoted according to the vertebra from which they branch out of the spine. For example, nerves originating in the cervical vertebrae (C1-C8) control sensory and motor impulses in the shoulder, diaphragm, arms and fingers. The thoracic nerves (T1-T12) control hands and fingers, chest muscles, and abdominal muscles. The lumbar nerves (L1-L5) control the hip, leg, knee, ankle and toes. Finally, the sacral nerves (S1-S5) controls leg and toe muscles, as well as muscles of the bladder and anus.
How do neurons communicate in the brain?
While all nerves can carry electrical impulses, some nerve cells can also communicate with other neighboring neurons with special chemicals called neurotransmitters. There are many types of neurotransmitters with many different functions, but each neuron generally only releases one type (on some occasions, two or three). Any neuron sending information is “efferent”, while any neuron receiving information is “afferent”. Both electrical and chemical (neurotransmitter) signals are sent from the axon of the efferent cell to the dendrites or soma of the afferent cell, a process which is called a synapse.
What are the main areas of the brain?
The brain can be roughly divided into the brainstem, cerebellum and cerebrum. The brainstem attaches the brain to the spinal cord, and the cerebellum, which is predominantly responsible for controlling coordinated muscle movements. The cerebrum is the largest part of the brain and is divided into lobes based on its region and functions. In the anterior and superior areas we have the frontal lobe (attention, reward, planning, short term memory), in the medial superior area is the parietal lobe (spatial awareness, touch, language), in the lateral areas are the temporal lobes (long term memory, language, emotion, hearing), and in the posterior area is the occipital lobe (vision).
