c3.1.14-16 feedback mechanisms in regulating body functions

CONTROL OF HEART RATE

cardiovascular centre of the medulla oblongata plays an important role in regulating heart rate, cardiac output & respiratory rate

Baroreceptors & chemoreceptors are located in the carotid sinus & the arch of the aorta

• baroreceptors - are mechanoreceptors & detect changes in blood pressure as it flows through the arteries

• chemoreceptors - detect changes in blood’s pH & levels of oxygen & CO2

• they both respond to stimuli by sending signals to cardiovascular centre of medulla oblongata

BAROCEPTORS

when blood pressure decreases

• baroreceptors detect the decreased stretch of arteries

• this info is sent to cardiovascular centre of the medulla oblongata

• the medulla oblongata will then activate the sympathetic nervous system and inhibits the parasympathetic nervous system

  • causes increase in heart rate & stroke volume (volume of blood pumped by left ventricle in each beat). the blood vessels also constrict, increasing blood pressure

when blood pressure increases

• baroreceptors detect the increased stretch of arteries

• information is sent to cardiovascular centre of the medulla oblongata

• medulla oblongata then activates the parasympathetic nervous system (and limits the sympathetic nervous system )

  • results in vasodilation, decreasing heart rate & stroke volume

  • this causes blood pressure to decrease

CHEMORECEPTORS

• when chemoreceptors detect a change in blood’s pH, or changes in CO2 & O2 concentration, they send a message to the medulla oblongata

  • this stimulates the sympathetic nervous system, which sends signals to the heart, increasing the heart’s rate

    • increase in heart rate = increase in blood flow to tissues bringing in O2 & removing CO2

CONTOL OF VENTILATION RATE

• the central chemoreceptors will detect the changes in blood’s pH & will result in the increased contraction & relaxation of respiratory muscles

  • ventilation rate increases, and excess CO2 is released

ROLE OF THE ENTERIC NERVOUS SYSTEM

• is a part of the automatic nervous system, & extends from oesophagus to rectum

• when food is swallowed, ENS controls the process of digestion

  • starts with peristalsis (movement of food down the tract due to rhythmic contractions of muscles)

  • then release of digestive enzymes

  • digestive enzymes are then mixed with the food

  • blood flow is controlled to allow these nutrients to be absorbed

• ejection of faeces is typically voluntary & under control of the CNS