Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SGUL - Physiology 1 > Reflex Control of CVS > Flashcards

Reflex Control of CVS Flashcards

1
Q

What receptors do excitatory inputs activate?

A

Arterial chemoreceptors and muscle metaboreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What type of response do excitatory inputs cause?

A
  • Stimulation of reflexes- increased cardiac output , increased total peripheral resistance (TPR) and blood pressure
  • PRESSOR response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What receptors do inhibitory inputs activate?

A

Arterial baroreceptors and cardiopulmonary receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of response do inhibitory inputs cause?

A
  • Stimulation of reflexes- decreased cardiac output, decreased total peripheral resistance and blood pressure
  • DEPRESSOR response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe arterial baroreceptors

A
  • Vital to maintaining blood flow to brain and myocardium
  • Detects arterial wall stretch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the importance of carotid arteries?

A
  • There are no ‘blood flow’ sensors, so the body monitors blood pressure in carotid and coronary arteries
  • Blood pressure sensors in walls of the carotid arteries inform brain of pressure changes
  • These sensors are baroreceptors
  • Decrease in pressure reflects a decrease in either CO or TPR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe how baroreceptors respond to an increase in pressure

A

Not much firing at rest then as pressure increases fast firing which eventually slows down and becomes constant, but at a higher level than before. ADAPTATION to a new normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe how baroreceptors respond to an decrease in pressure

A

For a decrease in pressure the firing slows down proportionately

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do long-term pressure changes affect baroreceptor activation?

A

Threshold for baroreceptor activation can change (eg. long term hypertension - baroreceptors become normalised at the new pressure and less activated)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the effects of increased blood pressure on baroreflex

A
  • Pulse pressure falls (decreased stroke volume)
  • Vasodilation - decreases TPR & BP
  • Decreased sympathetic nerve activity
  • Increased Vagus nerve activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the effect of decreased blood flow on baroreflex PART 1

A
  • Increased sympathetic activity & decreased Vagus activity
  • Increased HR and force of contraction so increased cardiac output
  • Arteriole constriction gives increased TPR
  • Venous constriction increases central venous pressure and so by Starlings law increases stroke volume & cardiac output
  • Maintains blood pressure therefore blood flow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the effect of decreased blood flow on baroreflex PART 2

A
  • Adrenaline secretion, vasopressin (ADH) secretion & stimulation of RAAS
  • Vasoconstriction decreases capillary pressure which increases absorption of interstitial fluid which also increases blood volume
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe where venoatrial mechanoreceptors are found

A
  • Present on the superior and inferior vena cava and right atrium - connected to vagus afferents from the heart to the nucleus tractus solitarius in the medulla
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How are venoatrial mechanoreceptors activated?

A

By an increase in cardiac filling / central venous pressure when cardiac output is increasing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does venoatrial mechanoreceptor activation result in?

A
  • Increased diuresis switches off ADH and RAAS which reduces sympathetic activity to the kidney to increase glomerular filtration - secretes atrial natriuretic peptide
  • Reflex tachycardia due to the rapid infusion of volume into the venous system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe where the ventricular mechanoreceptors can be found

A

Present on the right and left ventricles - connected to vagus afferents that connect the nucleus tractus solitarius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are ventricular mechanoreceptors activated?

A

Stimulated by over distension of ventricles

18
Q

What does ventricular mechanoreceptor activation result in?

A

Mild vasodilation , lower blood pressure and preload

19
Q

Describe where nociceptive sympathetic afferents are found.

A

Present on the ventricles towards the apex

20
Q

How are nociceptive sympathetic afferents activated?

A

Stimulated by K+, H+

21
Q

What does nociceptive sympathetic afferent activation result in?

A
  • Send signals to neurons in the spinal cord
  • Mediate the pain of angina and myocardial infarction
  • Increased sympathetic activity- causes someone to be pale and increased sweating
22
Q

Explain why the baroreflex is so important

A

Involved in maintenance of arterial pressure

23
Q

Describe where the arterial chemoreceptors are found

A

Located in carotid and aortic bodies

24
Q

What can stimulate arterial chemoreceptors?

A

Stimulated by low O2 (hypoxia) and high CO2 (hypercapnia)

25
Q

What is the purpose of arterial chemoreceptors?

A

Regulate ventilation and also drive cardiac reflexes during asphyxia (low O2/high CO2) shock (systemic hypotension) & haemorrhage
- Can compensate when blood pressure below baroreflex

26
Q

Describe the pressor response produced by arterial chemoreceptors

A
  • Increased sympathetic activity
  • Tachycardia
  • Increased selective arterial/venous constriction
  • Increased cardiac output & blood pressure - especially preservation of cerebral blood flow
27
Q

Describe what muscle metaboreceptors are

A

Sensory fibres in group IV motor fibres located in the skeletal muscle

28
Q

What are muscle metaboreceptors activated by?

A

Metabolites such as K+, lactate, and adenosine

29
Q

What is the pressor response caused by muscle metaboreceptor activation?

A
  • Increased sympathetic activity
  • Tachycardia
  • Increase arterial/venous constriction
  • Increase cardiac output/blood pressure
30
Q

Explain why muscle metaboreceptors are important during isometric exercise

A
  • Higher blood pressure drives blood into the contracted muscle to maintain perfusion
  • Muscles undergo metabolic hyperaemia allowing blood flow to the contracted tissue
31
Q

Describe the central role of the nucleus tractus solitarius (NTS). PART 1

A
  • Signal from stretched baroreceptor sent via afferent fibres enter Nucleus Tractus Solitarius (NTS)
  • This sends information out to the Caudal Ventrolateral Medulla (CVLM)
  • CVLM sends information to the rostral ventolateral medulla (RVLM)
32
Q

Describe the central role of the nucleus tractus solitarius (NTS). PART 2

A
  • Causes inhibition of sympathetic efferent nerves to heart and vessels
  • Less sympathetic efferent signals result in reduction in HR, less vasoconstriction, lower BP etc.
33
Q

State what happens when baroreceptors are stimulated in the heart

A
  • Stimulates the vagus nerve which activates the NTS
  • The signal from the NTS stimulates the nucleus ambiguous (vagal nuclei)
  • Vagal parasympathetic impulses are sent to the heart and these have a depressor effect
34
Q

Describe what happens in vagal parasympathetic outflow - sinus tachycardia

A
  • Inhibitory input from inspiratory centre
  • Each inhalation switches off the nucleus ambiguous
  • The inhibitory parasympathetic signal to the vagus decreases and the heart rate increases slightly
35
Q

Describe what happens in vagal parasympathetic outflow - vasovagal syncope

A
  • Cortex higher centres stimulate the hypothalamus limbic system (emotional centre)
  • Stimulates the NTS which in turn stimulates the nucleus ambiguous causing increased activity of the vagal nerve and depressor effect on the AV and SA nodes
  • Can lead to fainting (syncope)- causes by decreased cerebral blood flow due to sudden drop in arterial cardiac output and blood pressure
36
Q

What is syncope?

A

Fainting

37
Q

In terms of the link between the CVLM and RVLM, describe the effects of intravenous phenylephrine on the body.

A
  • Intravenous phenylephrine (α1 agonist) increases the TPR and BP
  • With the BP rising, the baroreceptors are loaded
  • There is a signal from the baroreceptors to the NTS, then to the CVLM
  • The CVLM signal inhibits the RVLM signals
  • Sympathetic activity to the heart and vessels decreases
  • The lower sympathetic signal gives vasodilation and increased BP
38
Q

What is the effect on arterial blood pressure when afferent fibres from baroreceptors are removed?

A

Large variation in arterial pressure

39
Q

What is the effect on arterial blood pressure when afferent fibres from cardiac receptors are removed?

A

Slight variation in arterial pressure

40
Q

What part of the brain deals with reflexes?

A

Medulla

41
Q

What do the following detect?

BARORECEPTORS
CHEMORECEPTORS
METABORECEPTORS

A

BARORECEPTORS - Pressure changes
CHEMORECEPTORS - CO2 and oxygen
METABORECEPTORS - products of metabolism

42
Q

What is the importance of having baroreceptors in the aortic arch?

A
  • EXAMPLE: if there is low pressure in the aortic arch, diastolic pressure is low
  • May indicate poor perfusion of coronary circulation

SGUL - Physiology 1 (68 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions