Neural control of the lungs RT 3005/6005

Study Notes

Neural Control of the Respiratory System

The autonomic nervous system (ANS) manages involuntary functions such as bronchial and arterial smooth muscle tone.
The system comprises two subdivisions: sympathetic and parasympathetic.
Sympathetic activation involves epinephrine and norepinephrine affecting beta (β2) and alpha (α) receptors.
Parasympathetic control is mediated through acetylcholine.

Anatomy of the Lungs

The apex is pointed and rises above the first rib; the base is broad and concave, extending to the 6th rib anteriorly and around the 11th rib posteriorly.
The mediastinal border of the lungs curves to accommodate the heart, constituting the hilum where bronchi, vessels, and nerves enter.

Lung Structure

The right lung is larger and heavier, divided into three lobes: upper, middle, and lower lobes; separated by horizontal and oblique fissures.
The left lung consists of two lobes: upper and lower, separated by the oblique fissure.

Mediastinum

The central cavity of the thoracic cage contains critical structures, including the trachea, heart, great vessels, nerves, portions of the esophagus, thymus gland, and lymph nodes.

Pleural Membranes

Composed of visceral and parietal pleura, holding together via serous fluid, maintaining negative pressure that keeps lung tissue adhered to the thorax.
The presence of air or fluid can equalize atmospheric pressure, causing separation.

Thoracic Structure

The thorax protects the cardiopulmonary system, bordered by 12 thoracic vertebrae posteriorly, the sternum anteriorly, and 12 pairs of ribs laterally.
Ribs are categorized: true ribs (1-7), false ribs (8-10), and floating ribs (11-12).
Contains 11 intercostal spaces that house vascular bundles and nerves along their inferior borders.

Diaphragm

The primary muscle of ventilation, shaped as a dome between the thorax and abdomen, merges into a central tendon.
Features three orifices accommodating the esophagus, aorta, and inferior vena cava.
Primarily innervated by the phrenic nerve; its downward movement during inspiration increases thoracic volume.

Inspiration Mechanics

Scalene, sternocleidomastoid, pectoralis major, trapezius, and external intercostal muscles are involved in the inspiratory process.
Scalene muscles elevate the first and second ribs, contributing to neck flexion.
The sternocleidomastoid rotates the head and elevates the sternum, enhancing the anteroposterior (AP) diameter of the chest.
Pectoralis major assists in the adduction of upper extremities and elevates the chest to increase lung volume.

Accessory Muscles of Expiration

Utilized during increased resistance, these muscles include rectus abdominis, external oblique, internal oblique, transversus abdominis, and internal intercostal muscles.
Their contraction raises intrathoracic pressure to counteract elevated airways resistance.

Internal Intercostal Muscles

Positioned beneath the external intercostals, they contract during expiration to pull ribs downward and inward, aiding in airflow reduction.

Description

This quiz explores the anatomy of the respiratory system with a focus on the neural control mechanisms. It covers the autonomic nervous system's regulation of bronchial and arterial smooth muscle, including a comparison of sympathetic and parasympathetic functions. Ideal for students in RT 3005/6005.