BIOL 2020 Test 3 Study set 4

Autoregulation

Self-regulation of arterioles and capillary beds.

Four mechanisms for control of blood pressure and blood flow

Cardiovascular center; neural; hormonal; autoregulation

Mechanisms which exert systemic control and which is local

autoregulation is local, all others systemic

Part of the brain which contains the cardiovascular center

Medulla oblongata

Parts of the brain the medulla oblongata receive signals from

Cerebral cortex, limbic system, hypothalamus

Parts of the peripheral nervous system the medulla oblongata receives signals from

Proprioceptors, baroreceptors, chemoreceptors

Two forms of output the cardiovascular system uses

Sympathetic and parasympathetic

Effectors activated by sympathetic output

Heart and blood vessels

Effects sympathetic output has on effectors

Heart: increases rate and contractility; vessels: causes vasoconstriction in some, vasodilation in others

Determines whether blood vessels constrict or dilate in response to sympathetic signals

Type of receptors that are present in their smooth muscle.

Baseline vasomotor tone and what it is a result of

Degree of contraction of the tunica media, and is a result of the level of sympathetic input.

Parts of the body which have more vasomotor nerves

Digestive system and skin

Effectors which are activated by parasympathetic output

Heart only

Effects parasympathetic output has on effectors

Heart: decreases rate

Function of baroreceptors

Send signals in response to being stretched under pressure

Where baroreceptors are primarily located

Aorta, internal carotid arteries, other large arteries in the neck and thorax

Aortic reflex

Baroreceptors in the aorta and aortic arch send signals to the cardiovascular center indicating higher pressure

Nerve used by the aortic reflex

Vagus nerve

Carotid reflex

Baroreceptors in the carotid sinuses send signals to the cardiovascular center indicating higher pressure

Nerve used by the carotid reflex

Glossopharyngeal nerve

Happens to baroreceptors under higher blood pressure

They are stretched

Response of baroreceptors to higher blood pressure

They send more frequent action potentials (signals) to the cardiovascular center

How the cardiovascular center responds to more frequent signals from baroreceptors

Increases parasympathetic output, which decreases heart rate. Also decreases sympathetic output, resulting in less heart contractility and less vasoconstriction

Happens to blood pressure and cardiac output under these circumstances

Cardiac output decreases, which decreases blood pressure

Happens to baroreceptors under lower blood pressure

They are less stretched

Response of baroreceptors to lower blood pressure

They send fewer action potentials to the cardiovascular center

How the cardiovascular center responds to less frequent signals from baroreceptors

Increases sympathetic output, which increases heart rate, heart contractility, and vasoconstriction

Orthostatic hypotension

Sudden drop in blood pressure from a change in posture

Demographic(s) most commonly affected by orthostatic hypotension

Elderly; also younger people who are ill

Consequence of orthostatic hypotension

Syncope (fainting) can result from sudden hypotension

Carotid massage

Rubbing the carotid sinus with the fingers

Intent of carotid massage, and a potential side effect

simulate high blood pressure, side effects include dizziness and syncope.

Chemoreceptors

Receptors that detect chemical changes in the blood

Three important chemical levels detected by chemoreceptors

Oxygen, carbon dioxide, hydrogen ions

When chemoreceptors increase signals to the cardiovascular center

hypoxia, hypercapnia, acidosis

Where chemoreceptors are primarily found

Carotid and aortic bodies, close to baroreceptors

Response of the cardiovascular center to increased chemoreceptor signals

Increased sympathetic output

Result of increased breathing rate

Increased venous return, increased oxygen intake

Cells responsible for detecting blood flow decrease, and their location

Juxtaglomerular cells in the kidney

Response of juxtaglomerular cells to blood flow decrease

release renin

Renin function

converts angiotensinogen to angiotensin I

ACE location and function

in the lungs, converts angiotensin I to angiotensin II

What angiotensin II does to the circulatory system

Causes peripheral vasoconstriction, raising resistance and raising blood pressure

What angiotensin II does to the adrenal medulla

Causes increased secretion of aldosterone

Aldosterone function

Causes increased reabsorption of sodium in kidneys and increased excretion of potassium into urine

Overall effect of aldosterone

Increased reabsorption of sodium causes water retention, raises blood volume, results in higher blood pressure.

What triggers antidiuretic hormone production

Decreased blood volume; also angiotensin II

Effect of antidiuretic hormone

increased water reabsorption.

Effect of atrial natriuretic peptide

increases salt loss by the kidneys, resulting in water loss

How is blood flow to a capillary bed increased

Precapillary sphincters are relaxed

How is blood flow to a capillary bed decreased

Precapillary sphincters are constricted

How is temperature homeostasis affected by autoregulation

Vasodilation causes increased blood flow to an area, warming it. Vasoconstriction causes decreased blood flow to an area, cooling it.

How arteriole stretching affects autoregulation

Arterioles will respond to stretching by contracting their smooth muscle

Effects of potassium on blood vessels

Vasodilation

Effects of hydrogen ions on blood vessels

Vasodilation

Effects of nitric oxide on blood vessels

Vasodilation

Effects of histamine on blood vessels

Vasodilation

Effects of thromboxane a2 on blood vessels

Vasoconstriction

Effects of decreased ph on blood vessels

Vasodilation

Effects of decreased oxygen on blood vessels

Vasodilation

Effects of increased CO2 on blood vessels

Vasodilation

Effects of increased stretch on blood vessels

Vasoconstriction

Effects of epinephrine on blood vessels with alpha receptors

Vasoconstriction

Effects of epinephrine on blood vessels with beta receptors

Vasodilation

Effects of angiotensin on blood vessels

Vasoconstriction

Effects of ADH on blood vessels

Vasoconstriction

Effects of ANP on blood vessels

Vasodilation

Effects of artery or arteriole stretching on blood vessels

Vasoconstriction

Effects of sympathetic nervous signals on blood vessels

Vasoconstriction