Sympathetic and parasympathetic nervous system + pharmacology

α₁ adrenoceptor function

Smooth muscle contraction (mostly vasoconstriction)

α₂ adrenoceptor function

Control how much noradrenaline is in the body by blocking its release. Act almost as brakes to the sympathetic system

β₁ adrenoceptor function

Increases heart rate and contractility

β₂ adrenoceptor function

Relaxes smooth muscle (mainly in bronchi and blood vessels)

β₃ adrenoceptor function

Stimulates lipolysis and relaxing bladder smooth muscle

What effect will blocking the NET (norepinephrine transporter) have on the effect of noradrenaline (NA) on the body

It will increase the effect, as there is less reuptake of NA, so more remains in the extracellular space, allowing it to remain active for longer

What effect will inhibiting MAO (monoamine oxidase) have on the effect of noradrenaline?

It will increase the effect, as MAO breaks down noradrenalin, and so it will only be able to go back into the extracellular space.

What ion is required to release ACh

Ca²⁺ , can be inhibited by botulism toxin to prevent ACh release

Main way ACh is removed from synaptic cleft?

Acetylcholinesterase irreversibly hydrolyses ACh

A cholinesterase inhibitor can be used to reverse action of nicotinic receptor antagonists (which would’ve caused paralysis). Hast he side effect of severely amplifying parasympathetic system.

Function of interstitial cells of Cajal?

Act as pacemakers for the gut, send electrical signals to tell gut muscles when to contract to ensure gut motility and peristalsis

What is the descending inhibitory reflex and the ascending excitatory reflex

Ascending excitatory reflex refers to a stimulus causing contraction of smooth muscle just above the stimulus, propelling it forward. Descending inhibitory is the relaxation of smooth muscle just below

What cells are stimulated to produce gastric acid (HCl)

Parietal cells

Main functions of submucosal plexus

Secretion, absorption, blood flow and minor function in certain muscle control and sensory input

Main functions of mesenteric plexus

Mostly involved in the muscle contraction and motility of the gut.

5 Step chain from sensing food to producing HCl

1. ACh

2. Gastrin

3. Histamine

4. Parietal cell

5. HCl

3 main acid releasing chemicals

Gastrin

Histamine

ACh