Human Anatomy: Sensory Pathways, Mediastinum, and More
Sensory Pathways
Sensory pathways are conduction channels that originate in the spinal cord and extend to the cerebral cortex, either at the cortical or subcortical level. These pathways transmit sensory information. There are two main types of sensitivity:
- Protopathic Sensitivity: Responsible for light or crude touch, temperature, and pain sensation.
- Epicritic Sensitivity: Mediates deep receptor discrimination between two points, location, and joint positions.
Neurons Involved in Sensory Pathways
- Protoneuron
- Neuron of the posterior horn and bulb at the spinal cord level
- Thalamic Neuron
- Neuron of the cortical sensory brain area
Mediastinum
The mediastinum is the space between the lungs, limited superiorly by the vertices of both lungs and the sternal notch, inferiorly by the diaphragmatic dome, and anteriorly by the posterior face of the sternum.
Pulmonary Innervation
The lungs are innervated by the autonomic nervous system, including both the sympathetic and parasympathetic branches. The sympathetic system causes bronchodilation and increases oxygen supply, while the parasympathetic system causes bronchoconstriction and increases respiratory secretions.
Cardiac Cycle Innervation
The heart is autonomous and has its own conduction system. It is also associated with the autonomic nervous system. The sympathetic system releases adrenaline in stressful situations, increasing heart rate. The parasympathetic system predominates during rest and digestion, decreasing heart rate.
Cardiac Conduction System
The cardiac conduction system is composed of transformed muscle cells capable of generating impulses. It consists of:
- Sinoatrial (SA) Node: Located in the right atrium near the superior vena cava, it generates the atrial contraction impulse.
- Atrioventricular (AV) Node: Triggers ventricular contraction.
- Bundle of His: Divides into two branches along the interventricular septum, leading to each ventricle.
- Purkinje Fibers: Network arising from the Bundle of His.
Male Genital System Parts
Testicle, epididymis, vas deferens, seminal gland, ejaculatory duct, prostate, urethra, and penis.
Female Genital System Parts
Internal organs: Fallopian tubes, uterus, and ovaries. External organs: Vagina and vulva.
Brain Function
- Motor function: Frontal lobe cortex.
- Touch: Parietal lobe.
- Hearing: Temporal lobe.
- Vision: Occipital lobe.
Nerve Fibers
Nerve fibers are formed by nerve bundles and protective proteins. Some are covered in myelin (myelinated), while others lack this covering (unmyelinated).
Hypothalamus and Pituitary Gland
These two structures are located in the diencephalon at the base of the brain. Hypothalamic neurons send projections to the posterior lobe of the pituitary gland (neurohypophysis). A network of blood vessels exists between both structures. The hypothalamus secretes releasing or inhibiting factors that act on the anterior pituitary gland (adenohypophysis). The connection between the hypothalamus and the anterior pituitary is vascular, while the connection with the posterior pituitary is neural. The hypothalamus secretes stimulating factors that trigger the release of hormones from the anterior pituitary.
Heart Innervation
The heart is innervated by the autonomic nervous system. Sympathetic activation, triggered by stimuli such as emotional or physical exercise, increases heart rate. Parasympathetic activity predominates during rest, slowing down the heart rate.