The Nervous System: A Comprehensive Analysis
The Nervous System
The nervous system is responsible for analyzing stimuli, both external and internal, and developing the necessary responses for the functioning of the body.
It can be distinguished into:
The Central Nervous System (CNS)
The CNS is in charge of body control and its activities.
The Peripheral Nervous System (PNS)
The PNS transmits nerve impulses from receptors to the CNS, and from the CNS to the effectors.
Central Nervous System
The central nervous system consists of the brain and spinal cord, which are protected by the skull and spine, respectively.
The CNS is surrounded by three membranous envelopes with protective function, called meninges, and cerebrospinal fluid, whose function is to cushion blows.
The Brain
The brain is located in the cranial cavity and consists of:
- Brain: It is divided by a groove into two zones or hemispheres: the left hemisphere and right hemisphere. The surface of both hemispheres is folded, resulting in convolutions. The outer zone, or cortex, is composed of gray matter, composed of cell bodies and dendrites of neurons. The innermost zone is called the white matter and consists mainly of axons coated with myelin. In the brain, we become aware of information that is received from the receivers, and analyze and process the orders that direct our volunteer activities. It is also responsible for thinking, memory, language, learning, etc., and many vital functions such as body movement, sleep, hunger, thirst, and so on.
- Cerebellum: It is located below the brain and is also divided into two hemispheres. It coordinates voluntary movements such as walking, maintaining balance in the body.
- Medulla: It is located at the base of the brain, in contact with the spinal cord. It controls involuntary body functions such as heartbeat, ventilation, sneezing, hiccups, vomiting, and peristalsis.
The Spinal Cord
The spinal cord is a tiny structure that has the thickness of a pinkie. It runs from the base of the skull to the end of the back. In cross-section, there are two regions: the inner, butterfly-shaped, consisting of gray matter, and the outer part, formed by white matter. The spinal cord controls numerous reflex actions that are performed automatically, such as withdrawing the hand when we get a puncture.
Peripheral Nervous System
In this part of the nervous system, extensions of neurons are associated to form nerve fibers which in turn are grouped in bundles and form nerves.
The peripheral nervous system consists of nerves, which leave the brain (cranial) and spinal cord (spinal), which branch and distribute throughout the body.
In its role, there are two types of nerves:
- Sensory nerves: Transmit information from receptors to the central nervous system.
- Motor nerves: They lead the information from the central nervous system to the effectors.
The most nerves are mixed, i.e., doing both sensory and motor functions.
From a functional standpoint, the peripheral nervous system is divided into two systems:
- Somatic nervous system: Intervenes in body movement (skeletal muscles are under voluntary control).
- Vegetative or autonomic nervous system: It works on the basic body functions that are performed unintentionally, unconsciously, and automatically, so the brain has no control over it, for example, heartbeat, movement of the lungs, or glandular secretions. Despite having involuntary control, some of these functions can be influenced by a voluntary and conscious action.
According to that function, it can be divided into two major subsystems: the sympathetic and parasympathetic with antagonistic effects. Each body is controlled by two distinct nerves of the autonomic nervous system, a branch of the sympathetic and another parasympathetic. In general, the sympathetic system prepares the body for activity, whereas the parasympathetic system prepares you for situations of rest. Both subsystems meet opposite but complementary functions.