Unit 2: Chapter 3: Receptors Of Effector Organs

Question 1

Receptors of the effector organs

Answer 1

Neurotransmitters bind with receptors on effector organs to produce their effects.

Question 2

Cholinergic receptors are divided into:

Answer 2

1. Nicotinic receptors.
2. Muscaranic receptors.

Question 3

What do Nicotinic receptors activate?

Answer 3

It only activates Nicotinic receptors.

Question 4

What are the sites of Nicotinic receptors?

Answer 4

1. Autonomic ganglia (membranes of postganglionic neurons).
2. Adrenal medulla.

Question 5

What do Muscarinic receptors activate?

Answer 5

Only muscarinic receptors.

Question 6

Sites of Muscarinic receptors

Answer 6

1. All effector cells stimulated by the post ganglionic neurons of the parasympathetic nervous system.
2. Those stimulated by the postganglionic cholinergic neurons of the sympathetic system.

Question 7

What are the two types of adrenergic receptors?

Answer 7

1. 2 Alpha: a1, a2.
2. 3 Beta: B1, B2, B3.

Question 8

Adrenergic receptors are present on:

Answer 8

1. Surface of effector organs= postsynaptic receptors.
2. Membrane of postganglionic nerve endings = presynaptic receptors.

Question 9

Adrenergic receptors

Answer 9

1. Presynaptic receptors.
2. Postsynaptic receptors.

Question 10

Presynaptic receptors

Answer 10

Autoreceptors present in membrane of postganglionic adrenergic endings.

Question 11

Presynaptic receptors function

Answer 11

Auto regulators that regulates the release of chemical transmitters from nerve endings.

Question 12

What happens when alpha presynaptic receptors are stimulated?

Answer 12

Stimulation of alpha presynaptic receptors decreases the releases of noradrenaline.

Question 13

What happens when beta presynaptic receptors are stimulated?

Answer 13

Stimulation of beta presynaptic receptors increases the release of noradrenaline.

Question 14

Postsynaptic adrenergic receptors: how does a1 produce its effects?

Answer 14

Through increasing intracellular Ca++.

Question 15

Postsynaptic adrenergic receptors: how does a2 produce its effects?

Answer 15

By inhibiting adenyl cyclase = decrease in c-AMP.

Question 16

Postsynaptic adrenergic receptors: how do B1 and B2 produce their effects?

Answer 16

Stimulating adenyl cyclase = increasing c-AMP.

Question 17

Distribution and actions of adrenergic receptors

Answer 17

The adrenergic receptors are distributed on the membrane of different organs and have different functions.

Question 18

Functions of alpha receptors

Answer 18

Contraction of plain muscles of: BISSSD
1. Blood vessels: vasoconstriction (skin, viscera, male genitalia).
2. Dilator pupillae muscle: mydriases.
3. Spleenic capsule.
4. Sphincters of GIT (retention of feces).
5. Internal uretheral sphincter (retention of urine).
6. Seminal vesicles and vas deference (ejaculation).
Relaxation of plain muscles of the intestine.

Question 19

Functions of beta receptors

Answer 19

Relaxation of plain muscles of: BBUUG
1. Blood vessels: vasodilation of coronaries and skeletal blood vessels.
2. Bronchioles: bronchodilation.
3. GIT.
4. Urinary bladder.
5. Uterus.
Cardiac acceleration and increased forced contraction of the heart.
Lipolysis.

Question 20

Noradrenaline and adrenaline are secreted by?

Answer 20

Adrenal medulla.

Question 21

What are different effects made on adrenergic receptors by noradrenaline and adrenaline?

Answer 21

1. Noradrenaline: excites mainly alpha receptors, but excites beta receptors to a slight extent.
2. Adrenaline: excites both types (a and B) receptors approximately.

Question 22

Functions of adrenal medulla

Answer 22

Stimulation of symptoms nerves to the adrenal medulla causes the release of:
1. Large quantities of adrenaline (80%).
2. Noradrenaline (20%) into the circulating blood of all tissues of the body.
These hormones have the same effects on different organs as those caused by direct sympathetic stimulation, except that the effects last 5 to 10 times as long, because these hormones are removed from the blood slowly.

Question 23

The relative effects ,adrenaline and noradrenaline, on different effector organs are determined by?

Answer 23

The type of adrenergic receptor in the organs.

Question 24

The effects of noradrenaline and adrenaline differ in?

Answer 24

1. Adrenaline has a greater effect in stimulating beta receptors which gives it a greater effect on cardiac activity than noradrenaline.
2. Adrenaline has several times as great a metabolic effect as noradrenaline.
3. Noradrenaline elevates the arterial blood pressure more than adrenaline as it produces strong vasoconstriction of blood vessels leading to increase in total peripheral resistance.

Question 25

What happens to the sympathetic nervous system during emergency situations?

Answer 25

It discharges as one unit to prepare the individual to cope with emergency Eg. Preparation for flight, fear, or fight.

Question 26

How does the sympathetic nervous system prepare for flight, fight, or fear?

Answer 26

1. Dilates the pupils: letting more light into the eyes.
2. Accelerates the heart beats and raises the blood pressure: provide better perfusion of vital organs and muscles.
3. Constricts the blood vessels of the skin: limits bleeding from wounds.
4. Lowers threshold in the reticular formation in the brain: Eg. Reinforcing the alert and aroused state.
5. Stimulates lipolysis and glycogenolysis: supplying more energy (glucose and free fatty acids).