12 - ANS

Question 1

Describe general effects of SNS and PNS

Answer 1

SNS
- Increase HR,
- Reduce blood flow to gut, skin, etc, reduce digestion system.
- Increase blood flow to skeletal muscles
- Pupil dilate (mydriasis)
PNS
- Decrease HR
- Increase digestive system
- Pupil constrict (miosis)

Question 2

Describe synapses and neurotransmitters of SNS and PNS

Answer 2

PNS = Nic ACh -> Mus ACh
SNS = Nic ACh -> alpha/beta NA
(exception of sweat glands ending w/ Mus ACh and adrenal medulla directly using Nic ACh first synapse

Question 3

Describe Dale’s Prinicple

Answer 3

The idea that only each receptor only affected by one synapse. This is false. Other transmitters can affect same receptor. Reasons may be because:
- One transmitter decays faster so other transmitter can give longer lasting effects
- Proportion of transmitters released can vary and be controlled.

Question 4

Describe pre-synaptic modulation in the ANS

Answer 4

PNS and SNS can inhibit each other’s release of NA by ACh or vice versa

Question 5

Describe co-transmission and neuro-modulation

Answer 5

• Presynaptic inhibition (e.g. Alpha 2 sits on presynaptic to inhibit NA release from reaching alpha 1 on BVs)
• Heterotropic presynaptic inhibition (e.g. NA inhibiting ACh)
• Postsynaptic synergism (two synapses co-transmit to have extra effect)