Physiology: Autonomic Nervous System
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- What is the somatic nervous system?
- Voluntary motor system under conscious control.
- What is the autonomic nervous system?
- Involuntary system controlling and modulating the functions of visceral organs.
- All preganglionic ANS neurons release which neurotransmitter?
- ACh.
- Postganglionic ANS neurons release which neurotransmitter(s)?
- ACh or norepinephrine
- What are the two main divisions of the ANS?
- Sympathetic and parasympathetic divisions.
- What is the name of the nervous system in the GI tract?
- The enteric nervous system.
- Where do the sympathetic preganglionic neurons originate from?
- The thoracolumbar spinal cord.
- From where do the parasympathetic neurons originate?
- The brain stem and sacral spinal cord.
- All postganglionic parasympathetic neurons release which neurotransmiter?
- ACh
- What type of receptors are present in the parasympathetic division targets, the smooth muscle and glands?
- Muscarinic receptors.
- What type of receptors are in the first synapse throughout the autonomic nervous system?
- Nicotinic receptors.
- What type of receptors are present in the sympathetic division targets smooth muscle and glands?
- alpha 1,2 and beta 1,2
- Which neurotransmitter is released in the second synapse at smooth muscle and glands in the sympathetic division?
- Norepinephrine.
- Which neurotransmitter is released in the second synapse at the sweat glands in the sympathetic division?
- ACh
- What type of receptor is present at the sweat glands in the sympathetic division?
- Muscarinic receptors.
- What do adrenergic neurons release?
- Norepinephrine.
- What is the substrate for adrenoreceptors?
- Norepinephrine.
- Can adrenoreceptors be activated by epinephrine?
- Yes.
- What do cholinergic neurons release?:
- ACh.
- What is the substrate for cholinoreceptors?
- ACh.
- What are the spinal segments from which the sympathetic preganglionic neurons originate?
- T1 to L3.
- What is the adrenal medulla?
- A specialized sympathetic ganglion whose preganglionic neurons originate in the thoracic spinal cord (T5-T9).
- What type of receptors are located on the adrenal medulla?
- Nicotinic receptors.
- What type of neuron synapses on the adrenal medulla?
- Cholinergic neurons.
- What type of neurotransmitters are released by the adrenal medulla?
- 80% epinephrine and 20% norepinephrine.
- What are chromaffin cells?
- The target cells on the adrenal medulla which release catecholamines into the general circulation.
- What are catecholamines?
- Norepinephrine and epinephrine.
- What are the cranial nerves from which the parasympathetic division originates?
- Cranial nerves 3, 7, 9, 10.
- From which sacral cord segments does the parasympathetic division originate?
- S2 to S4.
- Where are the ganglia of the parasympathetic division located?
- Near, on or in the effector organs.
- What happens to the pupil when the radial muscle of the iris contracts?
- Dilation or mydriasis.
- What happens to the pupil when the circular muscle of the iris contracts?
- Constriction or miosis.
- What type of sympathetic receptors does the heart have?
- beta 1
- What type of parasympathetic receptors does the heart have?
- Muscarinic receptors.
- What is the effect of stimulating the beta1 receptors of the heart?
- Increased SA node (heart rate), AV nodal conduction, and contractility.
- What type of sympathetic receptors are located in the bronchioles?
- beta 2 - stimulation leads to dilation
- Where in the vasculature are alpha 1 receptors located?
- The skin, splanchnic circulation, and skeletal muscle.
- What 2 sympathetic receptor types are located in the skeletal muscle?
- alpha 1 and beta 2
- What is the mechanism of action of alpha1 adrenoreceptors?
- Increased Ca++ by coupling to DAG and IP3 - generally leads to contraction.
- Where are alpha1 adrenoreceptors located?
- 1. vascular smooth muscle (skin, renal, splanchnic); 2. GI tract (sphincters); 3. bladder (sphincter); 4. radial muscle of iris.
- Where are alpha2 receptors located?
- 1. GI tract (wall); 2. presynaptic adrenergic neurons.
- What is the mechanism of action of alpha2 adrenoreceptors?
- Inhibit adenylyl cyclase, decrease cAMP.
- Where are beta1 receptors located?
- 1. heart; 2. salivary glands; 3. adipose tissue; 4. kidney.
- Where are beta2 receptors located?
- 1. vascular smooth muscle of skeletal muscle; 2. GI tract (wall); 3. bladder (wall); 4. bronchioles.
- What is the mechanism of action of beta1 and beta2 receptors?
- stimulate adenylyl cyclase, increase cAMP.
- Where are muscarinic cholinergic receptors located?
- All PNS effector organs and the SNS sweat glands.
- Where are nicotinic cholinergic receptors located?
- Skeletal muscle (motor end plate); postganglionic neurons of the SNS and the PNS; adrenal medulla.
- What is the mechanism of action of muscarinic receptors?
- Increased Ca++ by coupling to DAG and IP3.
- What is the mechanism of action of nicotinic receptors?
- Opening of Na+ and K+ channels leading to depolarization.