Overview
This lecture explains how the respiratory center in the brain integrates various inputs to control breathing rate and depth, and details the neural pathways and muscle groups involved in the process.
Respiratory Center & Brain Regions
- The respiratory center is located in specific brain regions responsible for controlling breathing rate and depth.
- Neurons within these regions communicate to coordinate breathing based on situational demands.
Chemoreceptors: Central & Peripheral
- Central chemoreceptors, located in the brain, detect changes in carbon dioxide and pH but not oxygen.
- Peripheral chemoreceptors (aortic body, carotid body) are outside the brain and detect oxygen, carbon dioxide, and pH, sending signals to the brain.
- Carotid body signals via the glossopharyngeal nerve (cranial nerve IX); aortic body signals via the vagus nerve (cranial nerve X).
Mechanoreceptors & Sensory Input
- Mechanoreceptors transmit information about pressure or stretch from the nose, lungs, and GI tract to the respiratory center.
- Baroreceptors are a type of mechanoreceptor found in blood vessels, but mechanoreceptors are more broadly distributed.
- Nose mechanoreceptors use the trigeminal nerve (cranial nerve V), while lungs and GI tract use the vagus nerve (cranial nerve X).
Emotional and Voluntary Control of Breathing
- The hypothalamus affects breathing in response to emotions like anxiety, fear, and pain.
- The cerebrum enables voluntary control of breathing for actions such as singing or yelling.
Motor Output: Muscles Involved in Breathing
- Diaphragm is controlled by nerves from spinal levels C3-C5.
- Intercostal muscles, helping expand ribs, are controlled by T1-T11.
- Abdominal muscles, aiding exhalation, are controlled by T6-L1.
- Accessory muscles in the neck are controlled by C1-C3.
Key Terms & Definitions
- Respiratory center — Brain area coordinating all activities related to breathing.
- Chemoreceptors — Sensors detecting chemical changes (CO₂, O₂, pH); divided into central (brain) and peripheral (outside brain).
- Mechanoreceptors — Receptors detecting physical stretch or pressure in tissues.
- Baroreceptors — Specific mechanoreceptors in blood vessels sensing pressure.
- Glossopharyngeal nerve (IX) — Cranial nerve transmitting signals from carotid body.
- Vagus nerve (X) — Cranial nerve transmitting signals from aortic body, lungs, GI tract.
- Trigeminal nerve (V) — Cranial nerve carrying sensory input from the nose.
- Accessory muscles — Neck muscles aiding breathing under increased demand.
Action Items / Next Steps
- Review cranial nerves (V, IX, X) and their functions in respiratory control.
- Study the pathways and roles of different muscle groups involved in breathing.