compare divisions of the autonomic nervous system effect on heart rate and stroke volume?

The 2 divisions of the ANS are sympathetic and parasympathetic. Sympathetic division elicits the fight-or-flight response, which increases both the rate and force of heartbeat. Norepinephrine is released during sympathetic stimulation at cardiac synapses, which increases the speed of contractions, as well as their strength. In the case of cardiac muscle, acetylcholine does the opposite (parasympathetic). The release of this neurotransmitter slows the heart down, that is when a person is not in stress and everything is working well. ACh increases the permeability of the membrane in cardiac muscle cells to potassium. As those channels open, potassium diffuses out of the cell making the interior more negative, which effectively hyperpolarizes the membrane. This reduces the ability of the pacemaker system to fire and slows the rate at which the action potentials are generated, thereby slowing the rate at which the SA node drives the beat.

Sympathetic and parasympathetic control basically only change the rate of firing at the sinus node. Therefore, sympathetics (fight or flight) cause an increase in HR, and parasympathetics (rest & digest) cause a decrease in HR. Therefore, there is not much change in stroke volume itself. However, there are 2 considerations. 1) sympathetics actually increase contractility some. This will increase the stroke volume decreasing the ESV. 2) A significant enough increase in HR can actually decrease SV, because the increase is primarily in diastole. If you cut diastole too short, you prevent the time in which the ventricle can fill, and therefore, the stroke volume will be smaller.

La ansiedad es un sentimiento con el que todas las personas de este mundo tenemos que lidiar en algún punto de nuestras vidas, e ir a psicoterapia, golpear una almohada o platicar con una amiga no siempre es posible.

Estas técnicas te ayudarán a liberar estrés rápido y fácil. http://solucionansiedad.info/?curar-ansiedad-66