Central and Peripheral Nervous System: Functions and Structures
**Central Nervous System**
The central nervous system is formed by the encephalon and the spinal cord. They are protected by the skull and the spinal column, respectively.
**Brain**
- Bulb রাকideo: Controls involuntary vital activities, such as the heartbeat.
- Cerebral Trunk: Controls sleep and wakefulness states, the operation of the hormonal system, and it must be connected to the hypothalamus.
- Cerebellum: Controls everything related to balance.
- Brain: The gray part is the cerebral cortex, which allows for language learning. The cortex folds to fit inside the skull, forming circumvolutions.
**Spinal Cord**
It is a thin, elongated structure that runs inside the vertebral column, from the base of the skull to the end of the back. It controls numerous reflex acts performed automatically.
**Peripheral Nervous System**
It is formed by the nerves that start from the encephalon and the spinal cord, and are distributed throughout the body.
**Two Types**
- Sensory Nerves: Transmit information from the receptors to the central nervous system.
- Motor Nerves: Conduct information from the central nervous system to the effectors.
**From a Functional Point of View, There Are Two Types**
- Somatic: Involved in body movement.
- Vegetative or Autonomous: Acts on basic functions of the body that are performed involuntarily, since the brain has control over them. Despite being involuntary, these functions can be influenced by voluntary activity.
To perform their work, they are divided into two major subsystems: sympathetic and parasympathetic, with antagonistic effects. The sympathetic system prepares the organism for activity, while the parasympathetic system prepares it for rest.
**Hypothalamus**
Located at the base of the encephalon and attached to the pituitary gland, it produces hormones – liberating or inhibiting factors that act on the pituitary gland, activating or inhibiting hormone production.
**Pituitary Gland**
A small gland at the base of the brain. It has two parts: the posterior, or neurohypophysis, and the anterior, or adenohypophysis.
**Endocrine System**
It is formed by a set of glands called endocrine glands, distributed throughout the body, and which directly release their secretions into the blood. These glands are formed by specialized secretory cells that synthesize chemical substances called hormones. Once produced, they are transported through the blood to all parts of the body via blood vessels.
**Neurons and Signal Transmission**
The transmission of these signals occurs through the nerve impulse, which is generated as a consequence of a change in the neuron’s plasma membrane. The nerve impulse is generated in a dendrite, travels through the neuron as electrical waves, and exits through the axon. Neurons are not in contact with each other; between them, there is a separation zone called a synapse. The transmission of the nerve impulse is carried out through the synapse by means of chemical substances called neurotransmitters. When the impulse reaches the end of the axon, neurotransmitters are released into the synaptic space. They then bind to the membrane of the dendrites or the cell body of the next neuron, triggering a new nerve impulse.
**Three Types**
- Sensitive: Carry information captured by the receptors to the central nervous system.
- Motor: Send information from the central nervous system to the effectors, causing the contraction of muscles or the secretion of glands.
- Interneurons: They are part of the central nervous system and connect sensory and motor neurons.
**Glial Cells**
They are interspersed between neurons, which they protect, isolate, or feed. Astrocytes are glial cells that nourish neurons, and Schwann cells are glial cells that wrap around certain axons of neurons, forming an insulating myelin sheath.
In a voluntary act, the response is conscious and voluntary. The elaboration of the response is made in the brain.
In a reflex act, the response to a stimulus is involuntary, and the center of elaboration of the response is in the spinal cord.
**Feedback**
Excess or defect in the amount of certain hormones in the blood can cause diseases. Due to this, endocrine glands do not secrete hormones constantly.