Vertebrate Nervous System: Anatomy and Functions Explained
The Vertebrate Nervous System
Vertebrates possess a tubular nervous system. The cephalic part of the tube is wide and forms the brain, while the subsequent, narrow, and long section is the spinal cord. It is divided into:
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Ganglia and nerves.
Central Nervous System
The CNS is protected by two types of coverings: bone and membranes. The bony coverings include the skull (protecting the brain) and the vertebrae (protecting the spinal cord). The protective membranes, called meninges, consist of three layers: the dura mater, arachnoid, and pia mater. Between these layers lies the cerebrospinal fluid.
Brain Structure
In the brain, gray matter is located in the periphery, while white matter is found in the interior. It is formed by the cerebrum, cerebellum, and medulla oblongata.
Cerebrum
The most voluminous portion, consisting of:
- Telencephalon: Divided into two hemispheres; the surface presents numerous grooves called circunvoluciones. This is where sensations become conscious and responses to stimuli are prepared.
- Diencephalon: Contains the hypothalamus and the pituitary gland. It controls sensations such as thirst and sleep, and regulates other endocrine glands.
- Midbrain: Responsible for monitoring visual and auditory reflexes and maintaining muscle tone.
Cerebellum
Located behind the cerebrum and divided into two cerebellar hemispheres. Its mission is to control and coordinate movements and balance.
Medulla Oblongata
Controls automatic body functions such as heartbeat and reflexes.
Spinal Cord
A tubular structure flattened dorsoventrally, extending from the base of the brain to the second lumbar vertebra. In the spinal cord, white matter (formed by axons) is located in the outer zone, while gray matter (formed by cell bodies) is located internally. It performs vital functions, such as controlling reflex actions and transmitting nerve impulses.
Peripheral Nervous System
Consisting of ganglia and nerves, it is categorized by origin:
- Cranial Nerves: Originating in the encephalon. There are 12 pairs that innervate the head, sensory organs, and facial muscles.
- Spinal Nerves: Originating from the spinal cord, each has two branches: sensory and motor. In humans, there are 31 pairs that innervate the arms, legs, and trunk.
Autonomic Nervous System
This physiological division controls involuntary visceral activities, such as heart rate and body temperature. It is divided into:
- Sympathetic: Prepares the body for active situations.
- Parasympathetic: Prepares the body for rest.