Nervous System: Role, Neurons, Brain, and Autonomic Functions
The Role of the Nervous System
The nervous system is a crucial system designed to achieve:
- The adaptation of the organism to changing environmental conditions, both external and internal.
- The relationship and coordination of the different parts of our body to act as a unified whole.
Sensory organs capture information in the form of environmental stimuli and transmit it to the nervous system. The nervous system receives, processes, and develops a response, which is then transferred to effector organs responsible for carrying it out. These effector organs include:
- The musculoskeletal system (muscles and bones)
- The endocrine system, which produces hormones regulating body functioning.
Neurons: The Building Blocks
Neural cells are typical of the nervous system. According to their function, they are classified as:
- Sensory neurons: Carry information from receptors to the central nervous system.
- Motor neurons: Transmit commands to effector organs.
Neurons generate and transmit nerve impulses. When a neuron is stimulated, changes occur in its membrane’s electrical potential, which is transmitted from dendrites to the axon.
Functional connections between neurons, called synapses, allow nerve impulses to pass from one neuron to another through areas located between the tail end of the axon of one neuron and the dendrite of a contiguous neuron. There is no physical contact between neurons at synapses; instead, there is a narrow space known as the synaptic gap or cleft.
At the end of the axon, tiny vesicles contain substances called neurotransmitters. When a nerve impulse reaches the end of the axon, these vesicles break open, releasing neurotransmitters into the synaptic gap. These neurotransmitters bind to the membrane of the dendrite of the adjacent neuron, potentially initiating a new nerve impulse.
Synapses are critical control points for the transmission of nerve signals.
Brain and Spinal Cord: The Central Nervous System
The central nervous system regulates and controls external stimuli. Due to its importance and fragility, it is protected from external injuries by:
- The skull and spine.
- Three membranes called meninges, located between the bone and the nervous tissue. The meninges are the pia mater, arachnoid, and dura mater.
- Cerebrospinal fluid between the meninges, which cushions against impacts.
The central nervous system is composed of:
Brain
- Cerebrum: Receives information from all sensory organs, processes it, and prepares orders for the effector organs. It controls voluntary responses and is responsible for intelligence, memory, consciousness, and will.
- Cerebellum: Controls balance and precision movements such as walking, drawing straight lines, and cycling.
- Brainstem: Controls states of sleep and wakefulness, as well as visual and auditory reflexes.
- Medulla Oblongata: Controls heartbeat and ventilation, alongside the autonomic nervous system.
Spinal Cord
- Performs reflex responses.
- Conducts nerve impulses to the brain and motor commands to the effector organs.
Peripheral Nervous System
The peripheral nervous system connects sensory organs with nerve centers and nerve centers with effector organs. It consists of nerves formed by bundles of associated axons and is made up of:
- Cranial nerves: Originating from the brain (12 pairs, sensory and motor).
- Spinal nerves: Originating from the spinal cord (31 pairs of mixed nerves).
Autonomic Nervous System
The autonomic nervous system coordinates the function of internal organs and acts involuntarily. There are two types:
- Sympathetic nervous system: Activates organs to work more intensely.
- Parasympathetic nervous system: Promotes relaxation and slower functioning of organs.