1. Blood pressure 1

2. Regulation of blood flow
Local regulation
Adjustment of blood flow by the tissue
Nervous system
Global implication
Redistribution of blood flow
Increase/decrease in heart activity (pumping)
Rapid control of arterial pressure

3. Autonomic system Sympathetic system More important Components
Vasomotor fibers
Thoracic spinal nerves
Lumbar spinal nerves
Sympathetic nerves
Innervation of internal viscera and the heart
Peripheral vessels

4. Innervation of blood vessels
Most tissues
Not capillaries, precapillary sphincters, or metarterioles
Increased resistance for blood flow
Decreased blood flow through the tissue
Decreased volume of vessels
Veins
Increased heart pumping

5. Innervation of heart Sympathetic Parasympathetic (vagus)
Increased heart rate
Increased strength
Increased volume of pumping
Parasympathetic (vagus)
Decreased heart rate

6. Vasoconstriction Sympathetic nerve fibers Vasoconstrictor nerve fibers
Very small number of vasodilators
Wide distribution
Tissue-dependent
More powerful in some organs
Kidney, GI tract, spleen, and skin

7. Vasomotor center
Reticular substance of medulla and lower third of pons
Transmission of parasympathetic impulses
Vagus nerves
Transmission of sympathetic impulses
Spinal cord
Peripheral sympathetic nerves

8. Area of vasomotor center
Vasoconstrictor area
Signals to all levels of spinal cord
Excitation of preganglionic vasoconstrictive neurons
Vasodilator area
Inhibition of vasoconstrictor area
Sensory area
Receives sensory inputs from vagus and glossopharyngeal nerves
Reflex control of many circulatory functions
Activity of both vasoconstrictor and vasodilator

9. Continuous signals from vasoconstrictor area
Sympathetic vasoconstrictor nerve fibers
Continuous firing at 1.5 – 2 impulses per second
Sympathetic vasoconstrictor tone
Maintenance of partial constriction of blood vessels
Vasomotor tone

10. Control of heart rate by vasomotor center
Excitatory impulses (sympathetic)
Lateral portion
Increased heart contraction and heart rate
Parasympathetic impulses
Medial portion
Sent via dorsal motor nuclei of the vagus nerves
Decreased heart rate

11. Control of vasomotor center
The CNS
Reticular substances of the pons, mesencephalon, and diencephalon
Hypothalamus
Posteriolateral – excitation
Anterior – mild excitation/inhibition
Cerebral cortex
Motor cortex
Basal areas of brain

12. Role of neurotransmitter
Norepinephrine
Sympathetic neurotransmitter
Vasoconstriction
Alpha receptors
Adrenal medulla
Secretion of epinephrine and norepinephrine in response to sympathetic impulses
Vasodilation via beta receptors (epinephrine)

13. Role of the nervous system in rapid control of arterial blood pressure
Stimulation of sympathetic nervous system and cardioaccelerator
Rapid increase in arterial pressure
2 X within 5-10 sec
During exercise or stress
Reciprocal inhibition of parasympathetic vagal inhibitory signals

14. Arterial Pressure = Cardiac Output x Total Peripheral Resistance
Arterial Pressure can be increased by:
Constricting almost all arterioles of the body which increases total peripheral resistance.
Constricting large vessels of the circulation thereby increasing venous return and cardiac output.
Directly increasing cardiac output by increasing heart rate and contractility.
Figure 14-1; Guyton and Hall

15. Maintenance of normal arterial pressure
Negative feedback reflex mechanism
Majority
Baroreceptor reflexes
Reflex initiated by stretching of arterial walls
Increased flow of blood and pressure
Detected by baroreceptors/pressoreceptors
Generation of inhibitory signals

16. Baroreceptor Spray-type nerve endings Stretch receptor
Carotid sinus
Hering’s nerve to glossopharyngeal nerves
Aortic arch
Vagus nerve
Signals enter medulla
Tractus solitarius

17. Response to pressure Net effect Very rapid
Respond more rapidly to changing pressure compared to stationary pressure
Inhibition of vasoconstrictor center
Vasodilation
Excitation of vagus nerves
Decreased heart rate
Net effect
Decreased arterial pressure

18. Constrict Common Carotids Pressure at Carotid Sinuses
Arterial Pressure
Constrictors
Figure 18-5; Guyton and Hall
Figure 18-7; Guyton and Hall

19. Functions of the Baroreceptors
Maintains relatively constant pressure despite changes in body posture.
Decrease
Central
Blood Volume
Supine
Standing
Sympathetic
Nervous Activity
Decrease
Cardiac Output
Vasomotor
Center
Sensed By
Baroreceptors
Decrease
Arterial Pressure

20. Pressure buffer system
Maintenance of constant pressure
Reduction of variability in blood pressure
Maintenance of pressure within the narrow range
Baroreceptors may not be important in long-term maintenance of blood pressure
Adaptation of receptors

21. Other mechanisms Chemoreceptors Calotid arteries and aorta
Detection of oxygen concentrations
Detection of carbon dioxide concentrations
Detection of pH
Detect changes in chemical concentrations
Decreased blood pressure
Excitation of vasomotor center

22. Activation of low-pressure receptors
Atria and pulmonary arteries
Detection of increase in pressure caused by increased blood flow
Volume reflex
Increase in glomerular pressure
Increased fluid loss
Decrease blood volume
Secretion of atrial natriaretic peptide
Maintenance of blood volume

23. Bainbridge reflex Increased atrial pressure Increased heart rate
Caused by increased volume and stretching of sinus node
Triggers increased heart rate
Prevents damming of blood

24. CNS inschemic response
Loss of blood flow to brain
Cerebral ischemia
Loss of nutrient
Accumulation of carbon dioxide
Activation of vasomotor center
Excitation of vasoconstrictor and cardioaccelerator
Increase in arterial blood pressure

25. Cerebral ischemia CNS ischemia response Cushing reaction
Occlusion of blood flow to the peripheral tissues if severe
CNS ischemia response
Emergency pressure control system
Maintenance of blood flow to the brain
Cushing reaction
Special type of CNS ischemia response
Increased CSF pressure around the brain