Understanding the Central Nervous System: Structure and Function
Understanding the Central Nervous System
The central nervous system (CNS) is responsible for analyzing sensory information, storing it, and initiating specific actions.
Spinal Cord
The spinal cord processes spinal reflexes. It conducts sensory nerve impulses to the brain and motor nerve impulses from the brain to effectors.
Brain Stem
Medulla Oblongata
The medulla oblongata contains the cardiovascular center (which monitors heart rate, force, and blood vessel diameter) and the respiratory center.
Pons
The pons contains pneumotaxic areas (regulating the length of inspiration and facilitating expiration) and apneustic areas (prolonging inspiration and inhibiting expiration).
Midbrain
The midbrain contains reflex centers for eye movement, head, and neck movement.
Diencephalon
The diencephalon contains the thalamus and hypothalamus and is a key focal point in the brain.
Thalamus
The thalamus processes sensory information, allowing us to perceive sensations like pain, temperature, and pressure before the information reaches the cerebral cortex.
Hypothalamus
The hypothalamus regulates homeostasis, including smooth muscle contraction, heart function, and the secretion of many glands. It also regulates body temperature and is responsible for sensations of hunger and thirst.
Cerebellum
The cerebellum controls skeletal muscle contractions necessary for coordination, maintaining posture, balance, and precise execution of movements.
Brain Functions
The brain has areas that interpret sensory impulses. Motor areas control voluntary muscular movement, and association areas are involved in complex processing such as memory, emotions, reasoning, and intellectual abilities.
Primary Sensory Areas
These areas receive information from sensory receptors and conduct impulses to association areas where this information is interpreted.
Memory, Learning, and Language
Learning and memory are complex processes developed by the brain. Learning is a dynamic process through which knowledge is acquired, allowing adaptation to a real context. Memory is the retention of that knowledge and its retrieval for use in specific contexts.
Neurons
A neuron consists of:
- Cell Body (Soma): Contains the nucleus, cytoplasm, and organelles such as lysosomes, mitochondria, and the Golgi apparatus. It also contains Nissl bodies, which are an orderly arrangement of rough endoplasmic reticulum, and neurofilaments forming the cytoskeleton.
- Dendrites: Short, branching extensions that extend from the soma.
- Axon: A long, cylindrical projection from the soma containing cytoplasm (axoplasm) with mitochondria but lacking rough endoplasmic reticulum. The surrounding membrane is the axolemma. Axons of neurons outside the CNS are coated with a myelin sheath formed from lipids and proteins produced by Schwann cells.
- Presynaptic or Synaptic Terminals (Buttons): The axon divides into terminal branches, each ending in synaptic buttons.
Neuron Function
Neurons can communicate precisely and quickly with other cells through electrochemical signals called nerve impulses. They form and interconnect the three components of the nervous system: sensory, integrative, and motor.
Neuron Classification
- Sensory or Afferent Neurons: Conduct nerve impulses to the central nervous system (spinal cord or brain stem).
- Association Neurons (Interneurons): Located within the CNS, they integrate and connect sensory and motor neurons.
- Motor or Efferent Neurons: Conduct nerve impulses to an effector (muscle or gland).
Neuron Types
- Unipolar Neurons: Have a single cell process (axon), generally with many ramifications. They are the simplest type of neuron and are predominant in invertebrate nervous systems.
- Bipolar Neurons: Have two separate processes that emerge from opposite poles of the neuron.
- Multipolar Neurons: Have a single axon and one or more dendrites emerging from different parts of the soma. This type of neuron is predominant in the nervous system of vertebrates.