Chapter 18 ( nervous regulation of the circulation and rapid control of arterial pressure)

Question 1

How is the sympathetic nervous system distributed?

Answer 1

thoracic nerves and first one or two lumbar nerves

Question 2

how does the sympathetic nervous system enter circulatoin?

Answer 2

1. via specific nerves that innervate vasculature of internal viscera and heart
2. via peripheral portions of spinal nerves in peripheral areas

Question 3

what is the only vessel that is not innervated by sympathetic NS?

Answer 3

capillaries

Question 4

what does sympathetic stimulation do to small arteries and arterioles?

Answer 4

increase resistance which decreases blood flow to tissues.

Question 5

what does sympathetic stimulation to large vessels like veins do?

Answer 5

these vessels decrease in volume which pumps more blood to the heart

Question 6

parasympathetic innervation of heart

Answer 6

Vagus nerve which decreases heart rate and contractility

Question 7

Where is the vasomotor center?

Answer 7

reticular substance in brain and lower 1/3 of pons

Question 8

where is the vasodilator area ?

Answer 8

anterolateral part of lower medula. These project upward and inhibit the vasoconstrictor area

Question 9

Where is the vasoconstricor area?

Answer 9

anterolateral part of upper medula

Question 10

sympathetic vasoconstrictor tone

Answer 10

continuous firing of vasoconstrictors. ~1-2 per second. They maintain a partial state of contraction

Question 11

vasomotor center affect on heart

Answer 11

lateral portion of vasomotor center on heart transmits excitatory impulses through sympathetic fibers to the heart and increases heart rate and contractility. Medial portion of vasomotor area sends signals to adjacent dorsal motor nuclei of vagus nerves which transmit parasympathetic impulses to slow the heart.

Question 12

control of vasomotor center by higher nervous centers

Answer 12

reticular substance of pons, mesencephalon, and diencephalon can excite or inhibit vasomotor area. In general the neurons in the lateral and superior portions of the reticular substance cause excitation. The more medial and inferior cause inhibition.

Question 13

hypothalamus role on vasomotor center

Answer 13

Causes both powerful excitatory or inhibitory effects on vasomotor center. The posterolateral portions cause excitation and the anterior portion causes mild excitation or inhibition

Question 14

cerebral cortex role on vasomotor center

Answer 14

many parts can either excite or inhibit vasomotor center

Question 15

Norepinephrine

Answer 15

secreted out of vasoconstrictor nerves which acts on alpha adrenergic receptors of vascular smooth muscle( in some tissues it causes vasodilation)
adrenal medullae- these secrete the epinephrine and norepinephrine into the blood.

Question 16

emotional fainting( vasovagal syncope)

Answer 16

vagus nerve slows heart and vasodilation occurs which causes the fainting.

Question 17

3 ways to increase arterial pressure

Answer 17

arterioles are constricted, large vessels like veins constrict which causes the heart to pump harder, direct stimulation by autonomic nervous system

Question 18

rapidity of arterial pressure

Answer 18

can increase pressure 2 times in 5- 10 seconds and decrease pressure by ½ in 10-40 seconds. It is the fastest way of controlling arterial pressure

Question 19

Baroreceptor arterial pressure control system-

Answer 19

s initiated by stretch receptors called either baroreceptors or pressoreceptors which are located at specific points in walls of several large systemic arteries. A rise in arterial pressure causes them to stretch and send feedback signals through the ANS to reduce arterial pressure.

Question 20

carotid baroreceptors pathway

Answer 20

via herings nerve, glossopharyngeal nerve, tractus solitarius in medulla

Question 21

aortic baroreceptors pathway

Answer 21

via vagus nerve, tractus solitarius of medulla.

Question 22

carotid sinus baroreceptors stimulation

Answer 22

get stimulated at 60 mm Hg and maximize at 180 mm Hg

Question 23

what causes baroreceptors to respond quicker

Answer 23

a rising pressure

Question 24

control of arterial pressure by carotid and aortic chemoreceptors

Answer 24

sensative to Oxygen lack, Co2 excess, and hydrogen excess. They excite nerve fibers along the baroreceptor fibers which pass through herings nerves and vagus nerves to vasomotor nerve. They decrease parasympathetic stimulation and increase sympathetic stimulation which increases heart rate and constricts the vessels. ( probably to try and get blood to the tissue thats lacking O2)

Question 25

when are chemoreceptors most powerfull?

Answer 25

below 80 mm Hg

Question 26

atrial and pulmonary reflexes

Answer 26

contain low pressure receptors that act like baroreceptors(if 300 ml was inserted into a dogs atria, the atria pressure rises only 15 mmHg. With the arterial baroreceptors removed it rises to 40 mm Hg and with the low pressure receptors removed in rises to 100 mm Hg)

Question 27

atrial reflex that activates the kidney (volume reflex)

Answer 27

an increase in atrial pressure increases the heart rate as much as 75%. ( 15% from increase in atrial volume and 40-60 % from bainbridge reflex)

Question 28

what is the bainbridge reflex?

Answer 28

when the atrial stretch receptors stretch and send a signal via vagus nerves to the medulla. Signals are sent back via vagus and sympathetic nerves to increase heart rate and strength of heart contraction

Question 29

CNS ischemic response

Answer 29

most powerful of all activators of sympathetic vasoconstrictor response. It is only activated when arterial pressure is below 60 mmHg and works its best at 15-20 mm Hg. Its an emergency pressure control system that acts rapidly and very powerfully to prevent further decrease in arterial pressure whenever blood flow to the brain decreases dangerously close to lethal level. Often called the last ditch stand

Question 30

cushing reaction

Answer 30

CNS ischemic response is initiated when CSF fluid is higher that arterial pressure in the brain. High CSF pressure can squish the brain and its arteries so the response acts as a cushion.

Question 31

abdominal compression reflex

Answer 31

baroreceptors and chemoreceptors send signals to skeletal nerves to skeletal muscles which compresses all venous reservoirs of the abdomen which provides more blood for the heart to pump

Question 32

skeletal muscle contraction

Answer 32

when exercising your muscles push blood back to the heart. IT can increase from a normal mean of 100 to 130-160 mm Hg

Question 33

respiratory wave

Answer 33

with each cycle of respiration the arterial pressure rises and falls from 4-6 mm Hg.