ANS Flashcards
What does the ANS control?
Involuntary activities:
- Smooth muscle
- Cardiac muscle
- Various glands
What are the 2 divisions of the ANS?
- Sympathetic NS
- Parasympathetic NS
What nerves does the parasympathetic NS affect?
- Brainstem:
- CN 3,7,9 - head structures
- CN 10 (vagus) - thoracic and abdominal organs
- Sacral spinal cord:
- S 2,3,4 - pelvic organs
What nerves does the sympathetic NS affect?
- Thoracic and lumbar regions of the spinal cord T1-L2
Where is the ganglion in a parasympathetic neuron of the ANS?
Close or very near to the effector organ
Where is the ganglion in a sympathetic neuron if the ANS?
Midway
What are the 2 components of the SNS?
- Nervous component
- Endocrine component
What is the endocrine component of the SNS?
- Adrenal medulla - produces and releases adrenaline into the blood stream
What is the ganglion like in the PNS?
- Long pre-gang neuron
- Short post-gang neuron
- Ganglion near or in effector organ
What is the ganglion like in the SNS?
- Pre- and post-gang neurons similar in length
- Synapse in Sympathetic chain or one of the collateral (or pre-vertebral) ganglia or in the adrenal medulla
Where does the PNS generally have actions on?
- Generally had discrete actions on single organs in the body ‘core’:
- Salivary gland; heart
What are the conservative, anabolic effects of the PNS?
- Storing energy - digestion etc
- Slowing heart
Where does the SNS generally have actions on?
- More widespread actions, often affecting whole body
* distribution of sympathetic nerves; circulating adrenaline
What is the SNS associated with?
- Homeostasis
- blood pressure, thermoregulation
- Fight, flight or fright
- meeting demands of active muscle
What is the effect of the ANS on smooth muscle?
- Blood vessels in various parts of the body
- Bronchi, bronchioles
What is the effect of the ANS on the heart?
- GIT - change in circulation of GIT will have effect on heart
- Rate, force of contraction
What is the effect of the ANS on glands?
- Salivary glands
- Gastro-intestinal glands
- Sweat glands
Does the ANS have an effect on metabolism?
Yes, a major effect
Does the ANS control breathing?
NO, the breathing muscles are skeletal muscles, and are controlled by somatic nerves (e.g. phrenic nerve) - not conscious but not controlled by ANS
What are the PNS and SNS effects on the iris?
PNS - Contraction
SNS - Contraction
What are the PNS and SNS effects on the ciliary muscle?
PNS - Contraction
SNS - Relaxation
What are the PNS and SNS effects on salivary glands?
PNS - Secretion (copious, watery)
SNS - Secretion ( viscous, low volume)
What are the PNS and SNS effects on the lacrimal gland?
PNS - Secretion
SNS - Secretion
What are the PNS and SNS effects on nasal glands?
PNS - secretion
SNS - nothing
What are the PNS and SNS effects on blood vessels?
PNS - Indirect effect - GI receives more blood as producing more so changes in blood pressure - increase
SNS - Constriction, dilation
What neurotransmitter acts on the parasympathetic nervous system?
ACh
What neurotransmitter(s) act on the sympathetic nervous system?
ACh
NA
What does noradrenaline cause?
- Contraction of smooth muscle in blood vessels
- Relaxation of bronchial smooth muscle
What do alpha adrenergic neurotransmitters cause?
Contraction of smooth muscle
What do beta adrenergic neurotransmitters cause?
- Relaxation of smooth muscle (beta-2)
- Increase heart rate and force of heart contraction (beta-1)
- ‘beta-blockers’ block beta-1 receptors only, so their effects are restricted to the heart
What is adrenaline used as?
A vasoconstrictor - acts on alpha blockers to prevent the local anaesthetic from leaving the intended area as quickly - reduces clearance of anaesthetic so treatment can last longer
Which patients are susceptible to potential problems when being given a LA with adrenaline?
Patients with heart conditions
What are muscarinic receptors?
- Membrane bound proteins with an extracellular domain that contains a recognition site for ACh, combination of ACh with the receptor initiates a physiological change
What are muscarinic receptors blocked by?
Atropine
What nerve supply do blood vessels and glands in the periphery receive?
- Sympathetic supply only
