Central and Peripheral Nervous System, Bones, Muscles, and Heart
Central Nervous System
The central nervous system and encephalopathy (brain) is divided into two hemispheres. On its central surface, protrusions are called gyri and indentations are called sulci. The outermost part is gray matter. The cerebral cortex receives information from the organs, develops orders, stores and processes the information. In the inner zone is the white matter.
- Cerebellum: Below the brain, it is divided into two hemispheres and shows a series of cerebellar circumvolutions. It coordinates walking, picking things up, and balance.
- Spinal Bulb (Medulla Oblongata): Links the brain with the top of the spinal cord. It controls blood flow and movements of the respiratory and digestive tract.
- Spinal Cord: Inside the vertebral column. The external part consists of white matter and the innermost part of gray matter. A nerve pathway ascends to the brain and descends to the organs. It has 31 pairs of spinal nerves responsible for governing some movements.
Peripheral Nervous System
Formed by nerves: a set of axons that send nerve impulses from receptor organs to nerve centers and from these to effector organs.
Types of Nerves
According to their origin:
- Cranial Nerves: 12 pairs, emerging from the base of the skull. They are directed to the head and neck. There are motor, sensory, and mixed nerves.
- Spinal Nerves: 31 pairs that leave the spinal cord, departing between the vertebrae. They are addressed to all the muscles of the trunk and extremities.
According to their function:
- Sensory Nerves: Transport information from the sense organs and internal organs to the central nervous system.
- Motor Nerves: Transport responses.
- Mixed Nerves: Formed by sensory and motor fibers.
- Parasympathetic Nerves: Regulate digestion and excretion.
- Sympathetic Nerves: Prepare our bodies for situations of tension and stress. Information is sent to all effector organs to meet these conditions (accelerated heart rate, sweating, etc.).
Neuron
- Soma: Contains the nucleus and most of the cytoplasm. It has prolongations:
- Dendrites: Short and branched.
- Axon: Long and unbranched except at one end, covered by white matter.
Bones
Face
Nose, vomer, malar (cheekbone), maxilla, zygomatic arch, frontal.
Skull
2 parietal, 2 temporal, occipital.
Trunk
- Rib Cage: Ribs (12 true, 8 false, 4 floating), sternum.
- Shoulders: Scapula, clavicle.
- Vertebral Column: Dorsal, cervical, lumbar, coccyx.
- Hip: Sacrum, innominate (ilium, pubis, and ischium).
- Arm: Humerus, radius, ulna, carpals, metacarpals, phalanges.
- Leg: Femur, patella (meniscus), tibia, fibula, tarsus, metatarsals.
Muscles
Face
Frontal, nasal, temporal, masseter, orbicularis oris, orbicularis oculi, buccinator, risorius.
Neck
Sternocleidomastoid, digastric.
Arm
Biceps brachii, triceps brachii, flexors, extensors, supinator.
Leg
Iliopsoas, sartorius, rectus femoris, biceps femoris, tibialis, gastrocnemius, flexor and extensor tendons (Achilles tendon).
Trunk
Pectoralis major, serratus major, rectus abdominis, external oblique.
Blood Vessels
- Arteries: Carry blood from the heart to the cells of the organs. Blood circulates inside the arteries under pressure.
- Veins: Carry blood from the organs to the heart. They have thin walls and low pressure. The blood returns to the heart due to the presence of valves that prevent backflow. Muscular contractions help filter blood. Veins are thicker closer to the heart.
- Capillaries: A denser network in the organs. They connect the two circulatory routes, allowing exchanges between the blood and the internal environment.
Heart
- 2 Atria: Thin-walled, extensible superior chambers. Blood enters the heart through these chambers.
- 2 Ventricles: Lower chambers with thick, powerful walls. Blood leaves the heart from the left ventricle through arteries.
- Right Side: Tricuspid valve (communicates right atrium and right ventricle).
- Left Side: Mitral valve (communicates left atrium and left ventricle).
- Vena Cava: Delivers blood to the right atrium.
- Aorta: Carries blood from the left ventricle. It has an aortic valve.
- Pulmonary Vein: Delivers blood to the heart.