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drug that acts like Ach, producing a response like Ach
Competitive inhibitor at muscarinic receptors
A drug that stimulates a receptor that's stimulated by NE.
- Enzyme: Tyrosine hydroxylase
- rate limiting step in the synthesis of Norepinephrine
destroys NE that's not pumped back into storage at a nerve ending. This is right after reuptake step of NE.
dopa decarboxylase. Dopamine then turns into Norepinephrine!
Transmitter released from parasympathetic nerves to cholinergic receptors on cardiac and smooth muscle cells and gland cells
an endocrine gland which releases a mixture of Epinephrine (80%) and norepinephrine (20%) into the blood. The release of this mixture is brought about by stimulation of nicotinic receptors
receptors stimulated by NE and similar agonists (alpha, beta1 and beta2)
antagonist at adrenergic receptors
Heart block aka AV block
An abnormal condition in which some atrial action potentials are unable to reach the ventricles. In mild cases there is delayed conduction to the ventricles, in more severe cases fewer action potentials reach the ventricles, and in most severe cases no action potentials reach the ventricles.
receptors stimulated by acetylcholine. Can be either muscarinic or nicotinic receptors.
receptors stimulated by acetylcholine and located on adrenal medullary cells, skeletal muscles and ganglia
Transmitter released from sympathetic nerves into synapses on cardiac and smooth muscle cells and glands
Parasympathetic nervous system
- division of ANS
- postglanglionic nerves of this system release acetylcholine
Sympathetic nervous system
- division of ANS
- postganglionic nerves release norepinephrine
Which adrenergic receptor is found on the SA node on the heart?
Beta 1 but beta 2 also (beta 2 not as important)
What is going to happen to the blood vessels on the skin of someone given an alpha agonist?
What's going to happen to the SA node of the heart if somebody gives you an alpha agonist?
nothing--no receptor no response
What's going to happen to bronchial smooth muscle if someone gives you a beta 1 agonist?
What's going to happen if someone gives you a beta 2 agonist?
What's going to happen to the sphincter of the urinary bladder if someone gives you an alpha 1 agonist?
constriction...impeding urine flow.
What's going to happen to the SA node if someone gives you a muscarinic agonist?
SAnod, muscarinic receptor-->reduced heart rate
What's going to happen to the force of contraction in the ventricles if someone gives you a muscarinic agonist?
not much.. There aren't too many parasympathetic nerves going to the ventricles so there isn't much of a response
What if someone gives you an anticholinergic drug?
Muscarinic receptors are going to be blocked. heartrate will increase.
What's going to happen to bronchial smooth muscle if someonegives you a drug that blocks beta1 and beta2 receptors?
contraction of bronchial smooth muscle, interference with ventilation.
What's going to happen to the adrenal medulla if somebody takes an antimuscarinic drug?
nothing. Because that's a nicotinic receptors.
If you're making less norepinephrine, blood vessels of the skin will...
tyrosinehydroxylase inhibitors are sometimes used in HTN individuals
it turns off the whole sympathetic nervous system. It can bring down blood pressure.
what happens to blood vessels of skin of people taking reuptake inhibitors
- Reuptake terminates the action of norepinephrine with a pump. If you block that pump, you'll accumulate NE in the synapes.
- Bv's will constrict. Blood pressure goes up.
- i.e. reuptake inhibitor is cocaine.
what's going to happen to heart rate if someone is taking cocaine?
- cocaine is reuptake inhibitor
- heart rate is controlled by SA node
- sympathetic nervous system on SA node can't terminate action of NE.
- NE accumulates and heart rate is going to go up.
Positive ionotropic effect
increase in heart rate
Positive chronotropic effect
An increase in force of contraction
Stimulation of beta 1 and beta 2 will open up:
- sodium channels, calcium channels, and potassium channels in cardiac muscle
- time between action potentials. Longer time between beats=longer diastole
- coronary blood flow occurs here
- Longer diastole means you have more time for ventricular filling. Most of the blood enters the ventricle by just plopping down. You have more time for that plopping
More cardiac work means...
- you are stimulating beta 1 and beta 2 on the SA node
- and on the cardiac muscle cells, you have a longer diastole, which results in more effective coronary blood flow.
- the more metabolites are producd. Metabolites result from cardiac contraction--very powerful vasodilators!
- The more work th eheart does, the more vasodilators are sent out, dilating coronary blood vessels.
If person had complete heart block,,,
- and if there were no action potentials reaching the ventricle, the purkinje fiber (since most have phase 4 diastolic depolarization) would by itself reach threshold. It would reach it very slowly. About 30 beats per minute.
- In an emergency, if all else fails, the occassional heart beat would be enough to keep you alive. If you give epinephrine, stimulating beta 1 and 2 increases slope of phase 4, so that it's more likely to reach threshold.