Autonomic Nervous System (Neurophysiology IV) Flashcards
What is the function of the ANS?
- controls body functions without conscious thought
- key in maintenance of homeostasis
- autonomic reflexes
What does the ANS control?
- smooth muscle, cardiac muscles + glands
What is the ANS mainly controlled by?
negative feedback
What are the parts of the ANS?
- sensory cells
- sensory nerve fibres
- control centers
- motor nerve fibers
- target organs
What are the control centers in the ANS?
- hypothalamus = master command
- brains stem –> controls respiratory + cardiovascular center
- spinal cord –> local integration in thoracic + sacral segments (doesn’t involve consciousness)
- receives continuous information from sensory nerves (frequency of impulses)
True or False: Motor nerve fibers in the ANS are the same as the somatic motor system.
False: Motor nerve fibers in the ANS are different than the somatic motor system.
What are the target organs in the ANS?
- smooth muscle, cardiac muscle + glands
How many peripheral nerves are in the ANS? How many peripheral nerves does the somatic system have?
- 2 peripheral nerves - pre + post ganglionic
- Somatic = 1 peripheral nerve
What is the preganglionic neuron?
- cell body in the CNS with axon that innervates the postganglionic neuron
What are the 2 major divisions of the ANS?
- sympathetic (thoraco-lumbar)
- parasympathetic (cranio-sacral)
Explain the sympathetic NS.
- fight or flight
- activated during stress
- preganglionic neurons in thoracic or lumbar spinal area –> send axons to sympathetic ganglia forming chain (interconnected ganglion) parallel to spinal cord
- post-ganglionic fiber is long in order to reach target
Explain the parasympathetic NS.
-rest + digest
- most active during rest
- preganglionic neurons originate in the brain or sacral part of spinal cord –> send axons to ganglia near effector organs
What is the enteric NS associated with?
- parasympathetic
- connected to digestive system
Where do preganglionic axons enter in the sympathetic NS?
- enter the paravertebral sympathetic ganglion chain
Where do some preganglion fibers extend into in the sympathetic NS? What is their function in this area?
- extend to adrenal medulla (adrenal glands)
- stimulate the secretion of epinephrine + norepinephrine into blood circulation
What cranial nerves supply parasympathetic fibers to the body’s gland + organs?
III (3), VII (7), IX (9) + X (10 = vagus nerve)
Explain the ganglia in the parasympathetic NS.
- located in wall or adjacent to target organs
- no interconnection between ganglia (no chain)
True or False: Postganglionic fibers in the parasympathetic NS are short axons.
True
Explain the postganglionic fibers in the parasympathetic NS.
- direct connection with specific organs (no branching off) with no enhancement by hormones = selective action
What is the post-ganglionic neurotransmitter in the parasympathetic NS?
acetylcholine (ACh)
What are the 2 types of receptors for ACh?
- nicotinic
- muscarinic
Explain nicotinic receptors.
- preganglionic synapses
- neuromuscular junctions = skeletal muscles (not ANS)
- ionotropic = part of ion channel
Where are muscarinic receptors located?
- in target organs of parasympathetic NS
Explain muscarinic receptors.
- separate from ion channel –> requires intracellular second messengers to activate target cell
- active series of events in cell using enzymes
- depend on messenger –> effect can be stimulatory or inhibitory
- slower + more prolonged effect
