Question

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Which of the following statements about action potentials is true? Action potentials trigger a reversal of...

Which of the following statements about action potentials is true?

		Action potentials trigger a reversal of the membrane polarity, with the interior of the cell becoming positively charged.
		Action potentials trigger reversal of the membrane polarity, with the interior of the cell becoming negatively charged.
		Action potentials trigger depolarization of the membrane by opening potassium voltage-gated channels.
		Action potentials lead to a sudden impermeability of the membrane to the transport of ions.
		Action potentials lead to a sudden rush of potassium into the neuron.

Which of the following statements about innate (non-specific) defenses is false?

		Phagocytes are capable of cellular ingestion and digestion of foreign substances.
		Phagocytes may use chemotaxis to migrate towards a site of infection.
		Histamine release from mast cells leads to vasoconstriction, thereby restricting the spread of infection.
		Natural killer cells attack virus-infected cells by releasing proteins that penetrate and kill the cell.
		Skin provides a first-line of defense by being a physical barrier.

Which one of the following events is true concerning transmission across a chemical synapse, such as at a neuromuscular junction?

Neurotransmitter binding to a postsynaptic receptor always inhibits the opening of ion channels

The postsynaptic membrane potential is always kept at –70 mV, regardless of the neurotransmitter that binds to it

Neurotransmitter molecules cross a synapse by the process of active transport

Changing the permeability to ions in the postsynaptic membrane results in local changes in membrane potential (voltage)

Neurotransmitter is released by endocytosis
Which one of the following statements is FALSE?

A single pathogen may stimulate the immune system to make several distinct antibodies to it.

An individual B-cell produces antibodies that bind to a number of different epitopes.

Most antigenic determinants are portions of proteins or glycoproteins on the surfaces of foreign cells.

A pathogen (microbe) usually has several different antigenic determinants.

An antibody usually recognizes and binds to an epitope on an antigen.

Solutions

Expert Solution

1. Action potential: When the cell membrane potential change of a specific cell generally the phenomena of depolarization is called the action potential.

a. Action potentials trigger a reversal of the membrane polarity, with the interior of the cell becoming positively charged,when the Na+ enters in the cell,during the action potential development.So this is true.

b. The interior of the cell becoming negatively charged when the cell is in resting state.So this option is incorrect.

c. Opening potassium voltage-gated channels results the cell restore the resting membrane potential.So this option is incorrect.

d. Action potentials lead to a sudden influx of Na+ in huge quantity,which cause the cell to become positive.So this option is incorrecr.

e. A sudden rush of potassium into the neuron cause restorstion of resting membrane potential.So this option is incorrect.

The correct option is-(a)

2. Innate immunity: when the body primari immuno cells acts to prevent any pathogen,by the lymphocyes, macrophages, etc.It is also known as the non-specific immunity.

a. Phagocytes is known as the cellular ingestion and digestion of foreign substances by the macrophages.So this option is ture.

b. Chemotaxis is the process to migrate towards a site of infection by the action of cytokines produced by the primary immuno cells in the infected area.This option is true.

c. In immuno respose the histamine relased from the mast cell involves in the formation and relase of the IgE antibody to prevent infection.So this option is false.

d. Natural killer cells attacks infected or abnormal cells by releasing proteins or toxic granules that penetrate and causes in swelling of the cell results brusting out which kill the cell.This is true.

e. The skin is the first line of defence,it acts as a physical barrier.So this is true.

The correct optin is-(c)

3. Neuro mascular junction: It is the connection point between the post synaptic neurone and the muscle.A threshold level of stimulation causes relese of neurotransmitter(like-Acetylcholine) from the post synaptic membrane which bind with the muscle membrane receptors and produce action potential results physiological response.

a. Neurotransmitter binding to a postsynaptic receptor always causes opening of ion channels like the Na+ &,Ca+ ion channels. So this option is wrong.

b. The postsynaptic membrane potential is rapidly increases towards the positivity due to Na+ entry in the muscle cell after neurotransmitter binds to it.So this option wrong.

c. Neurotransmitter molecules cross a synapse and attached to the receptor by diffusion.So this option is wrong.

d. Changing the permeability to ions in the postsynaptic membrane results in local changes in membrane potential (voltage) take place when the voltage in the post-syneptic membrane increase to positive chage the voltage gated Ca++ channels open and helps in the release of neurotransmitters.So this option is correct.

e. The vesicles are release by exocytosis.So this option is wrong.

The correct option is- (c)

4. a. A single pathogen may stimulate the immune system to make several distinct antibodies to it happens when the pathogen is new or unknown to the immuno system then the immuno cells(like the B & T lymphocytes) poduces several type of antibodies to kill it.So this statement is correct.

b. An individual B-cell produces antibodies that contains a very unique antigen binding site.So this statement is false.

c. Most antigenic determinants are portions of proteins or glycoproteins on the surfaces of foreign cells,which is also known as the antigenicity of the aprticular antigen.This statement is correct.

d. A pathogen (microbe) usually has several different antigenic determinants which helps the antigen to interact with various types of receptor of cell.This statement is correct.

e. An antibody usually recognizes and binds to an epitope on an antigen with the particular receptor type this also known as the antigen-antibody binding specificity.This statement is correct.

The correct option is-(b)

gladiator answered 1 year ago

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