Human Nervous System: Brain, Cerebellum, and Spinal Cord Functions
The Human Brain: Structure and Function
The brain is the organ with the greatest mass in the nervous system. Its surface is composed of a layer of gray matter, 2 to 4 mm thick, known as the cerebral cortex. Below this layer lies the subcortical white matter. During embryonic development, the cortex folds upon itself, creating convolutions. Due to this appearance, the cerebral cortex is often described as having a rough texture in mammals.
Cerebellum
The cerebellum controls skeletal muscle contractions, which are necessary for:
- Coordination
- Posture
- Balance
- Execution of precise movements
Diencephalon
The diencephalon contains the thalamus and the hypothalamus, serving as the main coordinator of the brain.
- Thalamus: The relay station where sensory information arrives, associating sensations such as pain, temperature, and pressure.
- Hypothalamus: A primary regulator of homeostasis. It contributes to the regulation of smooth and cardiac muscle contraction, glandular secretion, body temperature, and appetite.
Brain Stem
The brain stem is composed of the following regions:
- Medulla Oblongata: Contains the cardiovascular center, which controls the frequency and strength of the heartbeat.
- Pons: Contains the pneumotaxic and apneustic areas. The former limits the duration of inspiration and facilitates expiration, while the latter extends inspiration by inhibiting expiration.
- Midbrain: Acts as a reflex center for head and neck movements in response to visual and auditory stimuli.
Spinal Cord
The spinal cord contains neural circuits involved in rapid, automatic responses to stimuli. It serves as the center for processing spinal reflexes and conducts sensory nerve impulses toward the brain, as well as motor impulses from the brain to effectors.
The Reflex Arc
The reflex arc is the simplest circuit through which nerve impulses are carried. Its components include:
- Receiver: Sensory neuron dendrites that detect stimuli and trigger nerve impulses.
- Afferent (Sensory) Neuron: Conducts the nerve impulse to the central nervous system.
- Integration Center: A region of the nervous system containing association neurons that analyze information and prepare a response.
- Association Neuron: Connects sensory and motor neurons.
- Efferent (Motor) Neuron: Conducts the nerve impulse to the effector.
- Effector: The structure that responds to the nerve impulse.