Autonomic Nervous System 01.03.23

Question 1

How does the autonomic nervous system function?

Answer 1

Functions without conscious awareness (involuntary)

Question 2

Do fibres synapse in the autonomic NS?

Answer 2

Yes unlike the somatic they synapse once at a ganglion after they leave the CNS (two-neuron chain)
Then again at the effector organ

Question 3

What is the para and sympathetic output controlling?

Answer 3

Para - rest and digest
symp - fight or flight

Question 4

What muscle does the ANS and SNS innervate?

Answer 4

ANS - smooth muscle, cardiac muscle and glands either stimulates or inhibits at synapse
SNS - Innervates skeletal muscle fibres, always stimulatory

Question 5

What is the main para output?

Answer 5

Cranial nerves - supplying head, thorax and abdomen

Question 6

Where does the sacral outflow go? (Para)

Answer 6

To the pelvic organs

Question 7

What is the pathway of the somatic motor neuron?

Answer 7

Spinal cord to somatic motor neuron (myelinated). ACh (excitatory neurotransmitter) released which contracts skeletal muscle

Question 8

What is the pathway of the autonomic motor neuron?

Answer 8

1. Start in spinal cord
2. Then to preganglionic neuron (most are myelinated)
3. Then to the autonomic ganglion (where neurotransmitter released etc)
4. Then to postganglionic neuron (unmyelinated)
5. Then to the effector which might contract cardiac muscle or inhibition of glandular secretion etc…

Question 9

What are some functions of the ANS?

Answer 9

All functions we don’t think about: thermoregulation, Exercise, Digestion, Competition, Sexual function

Question 10

What are the sympathetic and parasympathetic outputs of the ANS?

Answer 10

Para - cranial and sacral outflow
Sympathetic - adrenal amplification

Enteric Nervous system (gut) operates separately to para and sympathetic system

Question 11

How does parasympathetic output travel to effector organs?

Answer 11

Via Cranial nerves 3,7,9,10 (1973)
Apart from Sacral outflow is S1 and 2

Question 12

How does sympathetic output travel?

Answer 12

1. White and grey Rami communicates to the sympathetic chain
2. Splanchnic nerves to large thoraco-abdominal plexi (secondary synaptic place) via unmyelinated fibres

Question 13

What is the sympathetic chain?

Answer 13

• Anatomically very close to spine
• Sympathetic ganglia deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response

Question 14

What does the adrenal medulla do?

Answer 14

• Some nerves synapse in adrenal medulla
• Releasing adrenaline
• vital for the fight or flight
• Sympathetic NS

Question 15

What is the neurotransmitter in Para?

Answer 15

Ach
- Has an autonomic ganglion as a secondary synapse

Question 16

What kind of system is the parasympathetic?

Answer 16

Cranio-Sacral system
(cranium - sacral: down body so motor)

Question 17

How does the enteric NS work?

Answer 17

Neurotransmitters circulating in portal system causing gut to secrete and works separately to the ANS

Question 18

In Sympathetic and parasympathetic NS what is the receptor on post synapse of ganglion?

Answer 18

Nicotinic receptor

Question 19

What is the difference in neurotransmitters at the effector cell for para and symp?

Answer 19

Para - NE (Norepinephrine) and receptor on effector post synaptic is adrenergic receptor
Symp- Ach again and receptor on effector is the muscarinic receptors

Question 20

What are the circulatory inputs to the ANS?

Answer 20

Series of inputs into brainstem nuclei to inform what level of pressure, stress etc.. body is at. Processed in brainstem and then sent down parasympathetic system to adjust our movement/contraction

Question 21

What is an important pressure receptor?

Answer 21

Carotid receptors, situated at branch of bifurcation of common carotid
(similar in aorta and LV)

Question 22

What happens at the nucleus tractus solitarius?

Answer 22

• Sensory nucleus receives inputs (normally about swallowing) and sends down pathway to effector
• Situated near hypothalamus
• Then signals travels to nucleus ambiguous (dorsal vagal nucleus)
• Then to ganglia and effector

Question 23

How do we test the ANS? (cardio vascularly)

Answer 23

Heart rate and blood pressure
- Head up Tilt Test (big fall in blood pressure when on a turn table)

Question 24

How can we measure ANS Non Cardiovascular?

Answer 24

• Sweat
• Skin blood flow
• Gastric acid secretion
• Sexual function