L22-heart Rate Regulation Flashcards
Normal heart rate
Higher where and lower where
50-100 bmp
Higher: children, females, exercise
Lower:adult males, athletes,rest and sleep
Where does nervous control occur in higher brain centers
Cerebral cortex
Limbic system
Hypothalamus
What are the sensory receptors
Proprioreceptors:movement
Chemoreceptors: blood chemistry
Baroreceptors:monitor blood pressure
What is the intrinsic rate of the SAN and how does it become lower
110-120 bmp
Becomes 70 by parasympathetic inhibition
How does heart rate inc during exercise
Inhibition of parasympathetic tone until it reaches 110 bmp then stimulation of sympathetic activity incs it more
Sympathetic innervation to heart locations
Cervical and stellate ganglia
Right side: heart rate regulation
Left side: cardiac contractility
How does sympathetic innervation affect hr
NE released at nerve endings acts on B1 receptors in the SAN and activates cAMP formation which activates populations of Na channels and L type calcium ion channels enhancing the rate of depolarization
Which is done through inc in Ca current in phase 4 of the SAN ap
Where does the parasympathetic innervation take place
Dorsal motor nucleus of the vagus or nucleus ambiguus
What is the parasympathetic effect on HR
▪️Acts on M2 receptors on the SAN via an inhibitory G protein mechanism which reduces the production of cAMP in cell
Reducing rate of depolarization
▪️hyper polarizing effect followed by binding of Ach to m2 receptors mediated by activation of K+ channels
What are the 3 types of reflexes
1-baroreceptor reflex
2-atrial stretch reflex
3-chemoreceptors reflex
Describe the baroreceptor reflex
In response to high or low bp In cases of high: When bp inc baroreceptors in carotid arteries and aorta send signals through sensory neurons to the medullary control center Sympathetic effect: Less NE:a1=vasodilation B1=dec force of contraction Parasympathetic effect: More ach: b1= dec force of contraction SAN=dec hr
Describe the atrial stretch reflex
When there is distention of atrial stretch receptors:
Inc heart rate: due to inc sympathetic effect on SAN only
Inc urine output: inhibition of ADH release(dec blood vol)
Release of ANP: generalized vasodilation
Potent diuretic and natruetic effects(dec blood volume and dec peripheral resistance)
Describe the chemoreceptors reflex
In response to: Dec O2 tension Inc H+ conc Inc Co2 tension Disruption is detected by chemoreceptors which send signals to respiratory centers in medulla oblongata which inc resp rate
What are the effects of the chemoreceptors on the CVS
Cardioaccelatory centers are stimulated
Cardioinhibitory centers are inhibited
Vasomotor centers are stimulated which causes vasoconstriction to occur
This causes an inc in cardiac output and bp
