L13: Baroreceptor And Volume Receptor Reflex Flashcards
What are the local factors that affect the heart
Intrinsic beating (from SAN) and starlings law (ventricles that respond to stress)
What are the local influences in the arterioles
Resistance by endothelial factors released
Myotonic stimuli
Metabolic factors that are released
What are the local influences for veins
Gravity
Respiratory pump
Muscle pump
What are the local factors for capillaries
Diffusion
Filtration
What are the 2 main roles of the CNS
Modulate reflex responses
Cause CVS and respiratory reflexes due to emotion
Which nerve supplies parasympathetic innervation to the heart
The vagus nerve
Which nerve supplies sympathetic innervation to the heart
Post ganglionic sympathetic fibres
What are the elements that make up a reflex
Receptor Afferent nerve CNS Efferent nerve Effector
Which part of the heart receives direct parasympathetic innervation only
SAN
Where does sympathetic NS act on in the heart
SAN
AVN
Ventricles
What other structures do post sympathetic fibres act on
Arterioles
Veins
What is the effect of sympathetic activity on vessel
Vasoconstriction
Which nucleus activates the vagus nerve for parasympathetic innervation to the heart
Nucleus ambiguus
Which nucleus acts on the pre-ganglionic sympathetic fibres
RVLM : rostral ventrolateral medulla
Which hormones are involved in the responces
Catecholamines
Vasopressin/ADH
Angiotensin 2
What is the role of the parasympathetic activity on the heart
Decrease heart rate
What is the role of the sympathetic activity on the heart
Increase hear rate
Name a simple reflex
Baroreceptor reflex
What is the role of the baroreceptor
Maintain/regulate arterial blood pressure (ABP)
What do baroreceptor detect
Stretch
What is stretch an indication of
Blood pressure
When does stretch increase
With increased blood pressure
Where are baroreceptors found in the body
Carotid sinus
Aortic arch
Where is the carotid sinus found
At the bifurcation of the common carotid artery into the internal carotid artery
How many carotid sinus do we have in the body
2 because there are 2 internal carotid arteries
Which nerve detects the changes from the baroreceptors in the carotid artery
Glossopharyngeal nerve (CN9)
Which afferent nerve detects the changes from the baroreceptors in the aortic arch
Vagus nerve (CN10)
Where does the afferent nerves of the baroreceptors feed into
NTS: nucleus tractus solitorious
What happens to the activity in the afferent nerves when the baroreceptors detect an increase in BP
Activity increases
What happens to the activity in the afferent nerves when the baroreceptors detect a decrease in BP
Activity decreases
What is the equation for the ABP
ABP=COXTPR
If abp falls how do we increase it back to normal
Increase CO
Increase TPR
What happens to the SNS activity when blood pressure falls
Increases
What happens to the PNS activity when blood pressure decreases
Decreases
What is the effect of the SNS when BP decreases
- SNS increases heart rate
- SNS increases contractility which increases stroke volume and increases
What is the combined effect of increasing SV and heart rate
It increases cardiac output
What is the effect of SNS on the arterioles when there is a decrease in BP
- SNS causes vasoconstriction and this increases the TPR
- SNS also causes the capillary hydrostatic pressure to fall to filtration from the interstitial space into the capillaries occur and this increases the EDV to increase pre-load
- increase in preload increases Stroke volume which increases cardiac output
What is the effect of SNS on the venous vessels
SNS causes venoconstriction
This squeezes the blood back to the heart and increases EDV
Increase in EDV increases SV by starlings law
Increase in SV increases CO
What is the effect of decreasing PNS activity to the heart
Causes an increase in HR as PNS activity decreases
Describe the baroreceptor reflex including its nucleus when the blood pressure INCREASES
1) afferent nerve fibres feed into the NTS
2) NTS feeds into the nucleus ambiguus to increase vagal activity to the heart and decrease heart rate
3) NTS feeds into the CVLM which causes an inhibitory input to the RVLM
So sympathetic activity decreases to the heart, arterioles and veins
4) NTS feeds into the SON PVN which inhibits the pituitary gland and therefore ADH (vasoconstrictor) release decreases
Describe the baroreceptor reflex including its nucleus when the BP decreases
The exact opposite of what i just described previously
What does the CVLM stand for
Caudal ventrolateral medulla
What is the role of the CVLM
To inhibit the RVLM
What does the SON PVN stand for
Supraoptic paraventricular nuclei
When SNS activity causes vasoconstriction in the arterioles, which arterioles are affected
Arterioles in the:
GIT
Skeletal muscle
Skin
Which arterioles in which organs are not affect
Kidney
Brain
Coronary
What happens to the kidney arterioles when there is an decrease in ABP
Myogenic dilatation
What happens to the cerebral arterioles when there is an decrease in ABP
Myogenic dilatation
What is the myogenic response
A response to stretch
What happens to the myogenic responce when ABP increases
Vasoconstrict
When there is an increase in ABP why does the arterioles vasoconstrict instead of dilating
The primary goal of these arterioles with autoregulation is to maintain a constant blood flow despite the increasing ABP with the myogenic responce
What happens when the abp falls below the range in autoregulation
Myogenic dilatation stops and instead it constricts to bring the BP back to normal
When do we get a decrease in ABP
When standing
Dehydration
Haemorrhage
Which reflex maintains the ABP in the longer term
Volume receptor reflex
What do volume receptor reflex detect
Stretch
Where are volume stretch reflexes located in the body
Right atrium
What are the afferent nerve fibres of the volume receptors
Vagus nerve (CN10)
What happens to the activity in the afferent nerve fibres when the receptors detect an increase in stretch
Activity increases
Describe the volume receptor reflex with the nucleus when there is a decrease in blood volume
1) decrease in blood volume decreases stretch so the afferent nerve fibres decrease in activity
2) this feeds into the NTS
3) NTS feeds into the paraventricular nucleus
4) this increases the SNS activity in the kidney
5) renal vasoconstriction occurs so less renal blood is filtered
6) ADH is released form pituitary so water is reabsorbed at the collecting duct
7) this reduces urine volume and increases blood volume
Describe what happens in the volume receptor reflex when there is an increase in volume
Exact opposite of what i have said
When does stretch in the volume receptor reflex decrease
Haemorrhage
Dehydration
When does the stretch in the volume receptor reflex increase
When lying down.
Which activity increases stretch to the baroreceptor
Cough
Sneeze
Excerise
Environmental and mental stressors
Which factors decrease the stretch in the baroreceptor i.e decrease ABP
Standing
Dehydration
Haemorrhage
Which reflex is faster
Baroreceptor reflex