(D) Elevated levels of $Na^+$ (sodium ions) in the blood interfere with the influx of $Ca^{2+}$ ions into the cardiac muscle cells.Since $Ca^{2+}$ is

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Both Assertion and Reason are incorrect.

(D) Elevated levels of $Na^+$ (sodium ions) in the blood interfere with the influx of $Ca^{2+}$ ions into the cardiac muscle cells.Since $Ca^{2+}$ is essential for the contraction of cardiac muscles,an excess of $Na^+$ inhibits this process,leading to a decrease in heart rate and contractility.Therefore,the Assertion is incorrect.Furthermore,elevated $Na^+$ levels do not increase the excitability of the $SA$ node; in fact,they tend to depress cardiac function.Thus,the Reason is also incorrect.

Class 11 Biology Body Fluids and Circulations Mix Examples- Body Fluids and Circulations

Medium

$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.
$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.

A
Assertion and Reason both are correct and Reason is the correct explanation of Assertion.
B
Assertion and Reason both are correct but Reason is not the correct explanation of Assertion.
C
Assertion is correct,but Reason is incorrect.
D
Both Assertion and Reason are incorrect.

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Body Fluids and Circulations

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Mix Examples- Body Fluids and Circulations

The blood bank of the body or the reservoir where blood is stored and can be mobilized is:

Easy

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In normal humans,the time taken for normal blood clotting is:

Easy

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Cardiac output is determined by which of the following?

Medium

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Match the following columns:
Column-$I$ Column-$II$
$(a)$ Lymphocytes $(I)$ Responsible for the immune responses of the body
$(b)$ Monocytes $(II)$ Are the agranulocytes
$(c)$ Neutrophils $(III)$ Most abundant cells of the total WBCs
$(d)$ Basophils $(IV)$ Inflammatory reactions

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Which of the following statements are wrong?
$(i)$ Leucocytes disintegrate in the spleen and liver.
$(ii)$ $RBC$,$WBC$ and blood platelets are produced by bone marrow.
$(iii)$ Neutrophils bring about destruction and detoxification of toxins of protein origin.
$(iv)$ The important function of lymphocytes is to produce antibodies.

MediumAIIMS 2013

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Column-$I$	Column-$II$
$(a)$ Lymphocytes	$(I)$ Responsible for the immune responses of the body
$(b)$ Monocytes	$(II)$ Are the agranulocytes
$(c)$ Neutrophils	$(III)$ Most abundant cells of the total WBCs
$(d)$ Basophils	$(IV)$ Inflammatory reactions

$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.

Similar Questions

The blood bank of the body or the reservoir where blood is stored and can be mobilized is:

In normal humans,the time taken for normal blood clotting is:

Cardiac output is determined by which of the following?

Match the following columns:Column-$I$Column-$II$$(a)$ Lymphocytes$(I)$ Responsible for the immune responses of the body$(b)$ Monocytes$(II)$ Are the agranulocytes$(c)$ Neutrophils$(III)$ Most abundant cells of the total WBCs$(d)$ Basophils$(IV)$ Inflammatory reactions

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$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.
$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.

Match the following columns:
Column-$I$ Column-$II$
$(a)$ Lymphocytes $(I)$ Responsible for the immune responses of the body
$(b)$ Monocytes $(II)$ Are the agranulocytes
$(c)$ Neutrophils $(III)$ Most abundant cells of the total WBCs
$(d)$ Basophils $(IV)$ Inflammatory reactions