Lecture 31 - Cardiovascular System: Regulation of Blood Pressure in the Short and Long Term Flashcards
What are 2 factors that blood pressure is affected by?
- Total blood volume (how much blood is present)
- Total resistance (what is the diameter of the vessels)
All across blood vessels
What regulates vasoconstriction?
The autonomic nervous system regulates vasoconstriction through (sympathetic) vasomotor fibres that make synapses on vascular smooth muscle. APs in vasomotor fibres lead to enhanced contraction in smooth muscle
What are the general sensors, integrator, and effector of mean arterial blood pressure?
Sensors - neurons in large elastic arteries
Integrator - neurons in hindbrain
Effectors - organs of the cardiovascular system
What are baroreceptors?
They are mechanosensory neurons that monitor mean arterial blood pressure found within the carotid sinus and aortic arch
These neurons send their axons (via CN IX and CN X) to the medulla oblongata
What are the 3 cardiovascular centres that baroreceptor info is integrated?
Integrated within cardiovascular monitoring centres in the brainstem within the medulla oblongata:
- Cardioinhibitory centres
- Cardioacceleratory centres
- Vasomotor
What is the function of the cardiac centres in the medulla oblangata?
They drive changes in cardiac output (CO) by altering activity in ANS inputs to the SA node of the heart and the myocardium
What is the function of the vasomotor in the medulla oblangata?
It drives changes to blood vessel diameter (in both arteries and veins) by altering activity in sympathetic vasomotor fibres
What can cause changes in overall chemical composition of blood in the systemic circuit?
Increased metabolic demands from peripheral tissues, where metabolic demands > current levels of CO:
- decreased PO2
- increased PCO2
- decreased pH (acidosis)
How does blood chemistry restore its levels?
Arterial chemoreceptors - drive homeostatic reflexes that alter blood flow throughout the circulatory system:
Sensors - neurons in large elastic arteries (and hindbrain)
Control center - integrator; neurons in hindbrain
Effectors - organs of the respiratory and cardiovascular system
This leads to blood chemistry being restored
What monitors blood gas composition?
Chemoreceptors - monitor mean arterial pH, P_O2, P_CO2. Found within the carotid bodies and aortic bodies
Where is chemoreceptor info integrated within?
It’s integrated within cardiovascular monitoring centres in the brainstem
Peripheral neurons send axons (via CN IX and CN X) to three cardiovascular centres and respiratory centre within the medulla oblongata
What are the effectors for short term alterations in blood gas composition?
Heart and blood vessel walls
Difference between homeostasis and allostasis in blood pressure regulation
Homeostasis - when BP is disrupted, BP is restored to the set point
Allostasis - when blood chemistry is disrupted, BP is moved to a new set point
T/F? Mechanisms of altering blood pressure over short terms are ideal for long term regulation
False - it is NOT ideal. Why?
- Energy intensive
- Maintain central pressure
What is needed for long-term regulation of BP?
Changes in blood volume - to maintain oxygen delivery at normal rates, blood volume changes must involve changes to both plasma and RBC levels
Adjustments to blood volume are slow, but they can maintain blood pressure throughout the circulatory system without constant energy input