Autonomic Nervous System 01.03.23 Flashcards
How does the autonomic nervous system function?
Functions without conscious awareness (involuntary)
Do fibres synapse in the autonomic NS?
Yes unlike the somatic they synapse once at a ganglion after they leave the CNS (two-neuron chain)
Then again at the effector organ
What is the para and sympathetic output controlling?
Para - rest and digest
symp - fight or flight
What muscle does the ANS and SNS innervate?
ANS - smooth muscle, cardiac muscle and glands either stimulates or inhibits at synapse
SNS - Innervates skeletal muscle fibres, always stimulatory
What is the main para output?
Cranial nerves - supplying head, thorax and abdomen
Where does the sacral outflow go? (Para)
To the pelvic organs
What is the pathway of the somatic motor neuron?
Spinal cord to somatic motor neuron (myelinated). ACh (excitatory neurotransmitter) released which contracts skeletal muscle
What is the pathway of the autonomic motor neuron?
- Start in spinal cord
- Then to preganglionic neuron (most are myelinated)
- Then to the autonomic ganglion (where neurotransmitter released etc)
- Then to postganglionic neuron (unmyelinated)
- Then to the effector which might contract cardiac muscle or inhibition of glandular secretion etc…
What are some functions of the ANS?
All functions we don’t think about: thermoregulation, Exercise, Digestion, Competition, Sexual function
What are the sympathetic and parasympathetic outputs of the ANS?
Para - cranial and sacral outflow
Sympathetic - adrenal amplification
Enteric Nervous system (gut) operates separately to para and sympathetic system
How does parasympathetic output travel to effector organs?
Via Cranial nerves 3,7,9,10 (1973)
Apart from Sacral outflow is S1 and 2
How does sympathetic output travel?
- White and grey Rami communicates to the sympathetic chain
- Splanchnic nerves to large thoraco-abdominal plexi (secondary synaptic place) via unmyelinated fibres
What is the sympathetic chain?
- 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
What does the adrenal medulla do?
- Some nerves synapse in adrenal medulla
- Releasing adrenaline
- vital for the fight or flight
- Sympathetic NS
What is the neurotransmitter in Para?
Ach
- Has an autonomic ganglion as a secondary synapse
What kind of system is the parasympathetic?
Cranio-Sacral system
(cranium - sacral: down body so motor)
How does the enteric NS work?
Neurotransmitters circulating in portal system causing gut to secrete and works separately to the ANS
In Sympathetic and parasympathetic NS what is the receptor on post synapse of ganglion?
Nicotinic receptor
What is the difference in neurotransmitters at the effector cell for para and symp?
Para - NE (Norepinephrine) and receptor on effector post synaptic is adrenergic receptor
Symp- Ach again and receptor on effector is the muscarinic receptors
What are the circulatory inputs to the ANS?
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
What is an important pressure receptor?
Carotid receptors, situated at branch of bifurcation of common carotid
(similar in aorta and LV)
What happens at the nucleus tractus solitarius?
- 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
How do we test the ANS? (cardio vascularly)
Heart rate and blood pressure
- Head up Tilt Test (big fall in blood pressure when on a turn table)
How can we measure ANS Non Cardiovascular?
- Sweat
- Skin blood flow
- Gastric acid secretion
- Sexual function
