• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Describe how the mechanism of ventilation is controlled. Describe the roles of the phrenic nerves and medulla in generating a basic breathing rhythm.

Extracts from this document...


Describe how the mechanism of ventilation is controlled.Describe the roles of the phrenic nerves and medulla in generating a basic breathing rhythm. Introduction The tidal flow of air into and out of the lungs is caused by differences in pressure between the thorax and the atmosphere.Air always moves from an area of higher pressure to an area of lower pressure.A ventilation mechanism ensures that a constant supply of fresh air is available to provide enough oxygen for gas exchange and to remove carbon dioxide. There are two processes of breathing- inhalation and exhalation Inhalation Air moves from high to low pressure.Hence the pressure in the lungs is low.The diaphragm muscle contracts and flattens.The external intercostals muscles contract and pull the rib cage out and up.The volume in the lung increases.This reduces the pressure in the lungs and air moves from the atmosphere(high pressure) to the lungs(low pressure) Process of breathing in Exhalation In this process the pressure in the lungs must be higher than the pressure in the atmosphere so that air move in an opposite direction to that in inspiration.The ...read more.


It receives inputs from various receptors around the body and sends output through two nerves to the muscles around the lungs.Impulses are sent along the phrenic nerve to the diaphragm and along intercostals nerves to the intercostal muscles.Unlike the heart, the muscles that cause breathing cannot contract on their own, but need nerve impulses from the brain for each breath Ventilation is controlled by impulses form- Chemoreceptors - in the medulla, aorta and carotid arteries. Stretch receptors -in the wall of the bronchi. Nervous control of breathing Biological Sciences 1 and 2 by D.J Taylor,N.P.O Green and G.W.Stout.) During inspiaration the lungs get inflated.The inflation causes the stretch receptors (or proprioceptors) located in the bronchial tree to get stimulated.More and more nerve impulses are sent via the vagus nerve to the expiratory centre.The vagus nerve connects the bronchial tree to the respiratory centre in the brain.Inspiration is temporarily inhibited.The external intercostals muscles therefore relax,elastic recoil of the lung tissues occurs and expiration takes place.After this has occurred the bronchial tree is no longer stimulated .Therefore the expiratory centre becomes inactive and inspiration can begin again.The whole cycle is repeated rhythmically throughout the life of the organism. ...read more.


Voluntary control is used during forced breathing,speech,singing,sneezing and coughing.When such control is being exerted,impulses originating in the cerebral hemispheres pass to the breathing centre which then carries out the appropriate action.Hyperventilation is forced deep breathing.Breathing in and out deeply reduces the carbon dioxide level in the blood.Increase in carbon dioxide concentration triggers breathing.A low level can suppress the stimulus to breathe.Divers hyperventilate before going underwater,so that the urge to breathe is reduced.This allows them to stay underwater for a longer period of time.Hyperventilation on the other hand could also be dangerous. Hyperventilation during panic or fear could reduce the urge to breathe which may result in fainting as the brain is deprived of oxygen.Once the conscious control is lost ,breathing resumes.In cases when a person has stopped breathing,it is essential to restart ventilation before permanent brain damage occurs due to lack of oxygen.Mouth to mouth resuscitation increases the carbon dioxide concentration in the patient's blood and hence stimulates their medulla to start the breathing process.Hospitals have resuscitators which also serve the same purpose. ?? ?? ?? ?? 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Humans as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Humans as Organisms essays

  1. To investigate how the heart rate and breathing rate increase with exercise.Scientific KnowledgeAerobic respiration ...

    Method I will measure my resting heart rate and my resting breathing rate. I will record this down in a table of results. I will then start the step ups at 6 steps every minute (1 step every 10 seconds)

  2. The Mechanism and Regulation of Breathing.

    One of the most important changes would be an alteration in the concentration of hydrogen ions in the blood this could be caused by a rise in blood carbon dioxide or an increase in tissue respiration in the muscles during exercise.

  1. Should the cloning of humans be allowed?

    Cloning 'Resurrects' Long Dead Mice. New Scientist. [Online], Available at: http://www.newscientist.com/article/dn15111-cloning-resurrects-longdead-mice.html [Accessed 3 February 2010] Cloning, 2009. [online]. National Human Genome Research Institute. Available at: http://www.genome.gov/25020028#al-1 [Accessed February 10 2010] Figure 1: [online]. Available at:http://www.ornl.gov/sci/techresources/Human_Genome/publicat/primer/fig11a.html [ Accessed February 9 2010] Figure 2: [online].

  2. The effect of exercise on gas exchange and breathing

    The binding of oxygen to haemoglobin can be represented by the haemoglobin dissociation curve: - A = arterial oxygen pressure (13.3 kPa); V = venous oxygen pressure (5.3 kPa) Like oxygen transport, carbon dioxide transport is passive. As carbon dioxide is a waste product from cellular respiration it is found in relatively concentration in tissues.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work