Sistema nervioso: Generalidades, partes y funciones - Anatomía Humana | Kenhub

What is the Nervous System?

Introduction to the Nervous System

• The speaker expresses a sense of wonder about stargazing and mentions an interesting fact about nerve cells, stating there are more nerve cells in the human body than stars in the Milky Way.

• The video aims to explain the nervous system, its functions, and its divisions, including central and peripheral systems.

Structure and Function of the Nervous System

• The nervous system is defined as a network of neurons that transmit information through electrical impulses. Its primary function is to gather environmental information and generate responses.

• Without the nervous system, humans would be unable to move, perceive surroundings, or even think; it also regulates vital organ functions.

Neurons: The Building Blocks

• A neuron consists of a cell body (soma) and processes called neurites that carry impulses. Neurites include axons (which send signals away from the soma) and dendrites (which receive signals).

• Different types of neurons have varying locations for their cell bodies and numbers of neurites.

Components of the Central Nervous System

Overview of CNS Components

• The central nervous system (CNS) comprises the brain and spinal cord. It serves as the main processing center for bodily functions.

Brain Regions

• The brain coordinates movement, controls vital functions like breathing and heart rate, and interprets sensory information. It has three main regions: cerebrum, cerebellum, and brainstem.

Cerebrum Functions

• The cerebrum is divided into left and right hemispheres that control opposite sides of the body. It handles various processes such as movement coordination, sensory interpretation, thinking, memory, language skills, emotions, etc.

Cerebellum Role

• Known as "little brain," it manages balance and coordination; damage can lead to unsteady movements similar to intoxication.

Brainstem Functions

• Connects brain with spinal cord; responsible for essential bodily functions like respiration regulation and reflexes. It includes midbrain, pons, and medulla oblongata.

Spinal Cord: Continuation of CNS

Spinal Cord Overview

Understanding the Nervous System

Overview of the Central and Peripheral Nervous Systems

• The bulbo raquídeo (medulla oblongata) descends through the spine, serving as a primary messaging system that transmits signals between the brain and peripheral nervous system.

• The spinal cord emits 31 pairs of spinal nerves, which are essential for forming the peripheral nervous system; without it, nerve impulses would not reach their intended destinations.

Components of the Peripheral Nervous System

• The Peripheral Nervous System (PNS) consists of all components outside the central nervous system, including spinal and cranial nerves, facilitating communication with organs and tissues.

• Nerves are cord-like structures that carry electrical impulses throughout the body; they consist of bundles of axons transmitting signals from one neuron to another.

Divisions of the Peripheral Nervous System

Autonomic vs. Somatic Nervous Systems

• The PNS is divided into two main parts: Autonomic Nervous System (ANS) (involuntary control) and Somatic Nervous System (voluntary control).

Functions of the Autonomic Nervous System

• The ANS regulates involuntary functions such as digestion, sweating, breathing, and heart rate through its two divisions: sympathetic and parasympathetic systems.

• The parasympathetic system promotes rest by lowering heart rate and stimulating digestion while relaxing digestive tract sphincters.

• In contrast, the sympathetic system triggers fight-or-flight responses by increasing heart rate, dilating pupils, and slowing digestion during stress.

Functions of the Somatic Nervous System

• The somatic nervous system manages voluntary motor functions by sending motor commands from CNS to skeletal muscles via efferent nerve impulses.

• Sensory information travels back to CNS through afferent nerve impulses in response to stimuli like touch or pressure.

Cranial Nerves Overview

• There are 12 pairs of cranial nerves, primarily providing sensory and motor innervation to head and neck regions; exceptions include vagus nerve affecting thoracic/abdominal organs.

Examples of Cranial Nerve Functions

• Saliva production is regulated by parasympathetic innervation from glossopharyngeal nerve (9th cranial), while sensation in facial areas is managed by trigeminal nerve (5th cranial).

Spinal Nerves Structure

• Spinal nerves provide both autonomic and somatic innervation across limbs/trunk; there are 31 pairs that transmit various types of signals from spinal cord to body.

Anatomy of Spinal Nerves

• Each spinal nerve has anterior roots carrying motor fibers and posterior roots carrying sensory fibers; they branch into four main rami for further distribution.

Rami Functionality

Understanding the Components of the Nervous System

Overview of Spinal Nerves

• Each spinal nerve is named according to the vertebral level from which it emerges, specifically from L1 to L5.

Relay Systems in the Peripheral Nervous System

• The relay systems in the peripheral nervous system are known as ganglia, which consist of collections of neuronal cell bodies found in both somatic and autonomic branches.

Types of Ganglia

• There are two main types of ganglia: sensory and autonomic. Sensory ganglia transmit information from the peripheral nervous system to the spinal cord.

• The spinal ganglion (or dorsal root ganglion) is associated with the posterior root of a spinal nerve, while cranial sensory ganglia relate to cranial nerves.

Autonomic Ganglia Functions

• Autonomic ganglia relay motor impulses from the central nervous system to target organs via autonomic nerves, divided into sympathetic and parasympathetic categories.

Plexus Formation and Function

• The innervation of limbs is complex due to contributions from multiple spinal levels; this complexity is managed by nerve plexuses.

• Five major nerve plexuses exist: cervical, brachial, lumbar, sacral, and coccygeal. These plexuses form networks that give rise to many familiar nerves.

Detailed Examination of Major Plexuses

Cervical Plexus

• Located in the neck (C1-C4), it innervates regions including the neck, back, and chest.

Brachial Plexus

• Originating from C5-T1 at the lower neck area, it supplies nerves to the upper limb. Key nerves include:

• Ulnar nerve: runs along medial arm/forearm.

• Radial nerve: located posteriorly/laterally.

• Median nerve: travels through anterior midline arm.

Lumbar Plexus

• Formed by contributions from lower thoracic/lumbar regions (L1-L4), it primarily innervates parts of the lower limb. Notably includes:

• Femoral nerve: provides motor/sensory innervation to thigh muscles.

Sacral Plexus

• Found distal to lumbar plexus (L4-S4), it serves posterior thigh/leg/pelvis areas. Includes:

• Sciatic nerve: innervates posterior thigh/leg; bifurcates into common fibular/tibial nerves.

Coccygeal Plexus

• Located within pelvis (S4-S5), this plexus provides innervation for pelvic regions.

Clinical Correlations Related to Motor Neurons

• Motor neurons transmit impulses from CNS to muscles; diseases affecting them can lead to significant muscle weakness or atrophy.

Motor Neuron Disease Insights

• This degenerative disorder impacts both central/peripheral motor neurons leading to reduced muscle innervation. Symptoms vary based on neuron type affected:

• Upper motor neuron degeneration results in spasticity/hypertonia.

• Lower motor neuron degeneration leads to muscle atrophy/weakness.

Treatment Approaches

• Currently no cure exists for motor neuron disease; symptom management focuses on physical therapy/respiratory support alongside medical interventions with medications.

Understanding the Nervous System

Overview of the Nervous System

• The central nervous system (CNS) consists of the brain and spinal cord, with the brain serving as the main processing center divided into three regions: cerebrum, cerebellum, and brainstem.

• The peripheral nervous system (PNS) includes spinal nerves and cranial nerves that transmit messages between the spinal cord and peripheral areas of the body.

Components of Peripheral Nervous System

• The PNS is categorized into somatic (voluntary control) and autonomic (involuntary control), which transmits motor impulses unconsciously to target organs like the heart and lungs.

• There are 12 pairs of cranial nerves originating from the brain primarily innervating structures in the head and neck, alongside 31 pairs of spinal nerves emerging from the spinal cord.

Functionality of Nerves

• Spinal nerves contain motor, sensory, and autonomic components; ganglia assist in relaying nerve impulses to/from the CNS.

• Anterior branches of spinal nerves mix to form plexuses that provide innervation to limbs and trunk; key nerves for each body region were identified.

Neurological Disorders