Sympathomimetics Flashcards
On what five groups of tissue can we find alpha 1 receptors?
- Most vascular smooth muscle
- Iris
- Pilomotor smooth muscle
- Prostate and Uterus
- Heart.
What actions do the alpha 1 receptors have on the tissues they are located on?
- Contraction of the vascular smooth muscle beds (blood vessels, sphincters and bronchi).
- Contraction of the radial muscle of the iris (which dilates the pupil = mydriasis).
- Erects hair via the pilomotor smooth muscle
- Contraction of the prostate and uterus
- Increases force of contraction of the heart.
Which five tissues do we see a response from alpha 2 receptors?
- Platelets
- Adrenergic & cholinergic nerve terminals (presynaptic)
- Vascular smooth muscle
- GI tract
- CNS
What actions do the alpha 2 receptors have on the tissues they are located on?
Cause:
- Aggregation of platelets
- Inhibit transmitter release from adrenergic and cholinergic nerve terminals
- Contraction of vascular smooth muscle post-synaptically or dilation presynaptically in the CNS.
- Relaxation of the GI tract presynaptically
- Sedation and analgesia in the CNS via decreased SNS outflow from the brain stem.
Why does blood vessel contraction not end up being a big deal with alpha 2 receptor activation?
Because the presynaptic postganglionic neuron alpha 2 receptors at the blood vessel act as ultra-short loop negative feedback as then release NE that NE feeds back to the receptor changing the potassium conductance and hyperpolarizing the cell inhibiting further release of NE.
Which tissue is more sensitive to lower levels of alpha 2 activation?
The brain.
What is the problem with antagonizing the alpha 2 receptor?
We lose our negative feedback and would end up with a shit ton of circulating NE.
What two main places are Beta 1 receptors found?
- Heart
2. Kidneys
What actions do the Beta 1 receptors have at their tissue sites?
- Increase the force and rate of contraction of the heart
2. Stimulation of renin release.
What six places do we find Beta 2 receptors?
- Visceral smooth muscle (respiratory, uterine, vascular GI, GU)
- Mast cells
- Skeletal muscle
- Liver
- Pancreas
- Adrenergic nerve terminals.
What actions does the Beta 2 receptor have at the tissue level?
- Promotes smooth muscle relaxation
- Decreases histamine release
- Potassium uptake, dilation of vascular beds, tremor and increased speed of contraction
- Glycogenolysis
- Increased insulin secretion
- Increased release of NE
Beta 3 targets? causing?
- Fat cells
2. Activates lipolysis and thermogenesis.
Which Dopamine receptor is found on smooth muscle?
D1
What kind of action does the D1 receptor cause to happen in the smooth muscle?
Post-synaptic location; dilates renal, mesenteric, coronary and cerebral blood vessels.
Which Dopamine receptor is found on nerve endings?
D2 receptor