Autonomic Nervous System Flashcards
What consists of the central nervous system?
- brain and spinal cord
- everything else is the peripheral nervous system
What two divisions is the peripheral nervous system split into?
- afferent
- efferent
What is afferent?
- action potentials that transmit information from the sensory receptors and visceral stimuli, INTO the CNS from the periphery
What is efferent?
- action potentials heading away from the CNS to the periphery
What 2 divisions is efferent split into?
- somatic nervous system
- autonomic nervous system (ANS)
What makes the autonomic nervous system (ANS) special?
- it does not require conscious regulation
How does the autonomic nervous system (ANS) function?
- It is part of the peripheral nervous system (PNS).
- It regulates the activity of the internal organs (smooth muscle, cardiac muscle, and glands).
- It is not directly affected by voluntary control but operates automatically (autonomic reflexes and central control).
- A major function is homeostasis (maintenance of the internal environment under optimal conditions).
- It is divided into sympathetic (‘fight or flight’)and parasympathetic (‘rest and digest’).
What does the sympathetic nervous system do?
- dilates pupil
- inhibits salivation
- accelerates heart
- facilitates breathing
- inhibits digestion
- stimulates release of glucose
- secretes epinephrine and norepinephrine
- relaxes bladder
- inhibits sex organs
What does the parasympathetic nervous system do?
- constricts pupil
- stimulates salivation
- slows heart
- constricts breathing
- stimulates digestion
- stimulates gallbladder
- contracts bladder
- stimulates sex organs
How does the ANS connect the CNS to the organs?
- there are autonomic ganglion between them
- the neurons from the CNS to the ganglion are preganglion and those distal are postganglion.
Where are the sympathetic ganglia found?
- usually located close to the CNS
Where are the parasympathetic ganglia found?
- usually located close to the target organ, if not embedded
Are preganglionic fibres myelinated?
yes
Are postganglionic fibres myelinated
no
How many cell bodies do sympathetic preganglion axons innervate?
- more than 20 cell bodies in the ganglia which affects many post ganglionic fibres
How many cell bodies do parasympathetic preganglion axons innervate?
- a much smaller extent than sympathetic preganglion axons, less than 4 cell bodies
Where are the paravertebral ganglia located?
- They are sympathetic ganglia that are aligned in a row on each side of the spinal cord
Where are the prevertebral ganglia located?
- There are other sympathetic ganglia that are located further away
What are the ANS neurotransmitters and where are they used?
- In the sympathetic nervous system, acetylcholine is used in the preganglionic neurones
- In the sympathetic nervous system, norepinephrine is used in the postganglionic neurones
- in the parasympathetic nervous system, acetylcholine is used in the preganglionic and postganglionic neurones
Where is the acetylcholine secreted?
- ACh is secreted in the preganglionic neurons and recycled from its breakdown products in the synaptic bulb.
What are the 2 types of receptors for ACh?
- nicotinic
- muscarinic
what are nicotinic receptors?
When ACh (or nicotine) binds, they open to allow ions to flow (usually Na+ in and K+ out with a net influx).
What effect does nicotinic receptors have?
Ionotropic, which means that binding of the ligand to the channel directly alters the permeability of the channel.
often causes fast synaptic transmission and
often stimulatory.
What are muscarinic ACh receptors?
When ACh (or muscarine) binds, they release G proteins, which begin a cascade of information.
what effect does muscarinic ACh have?
Metabotropic, which means that binding of the ligand to the channel indirectly alters the permeability of ion channels.
There are several types
May be stimulatory or inhibitory
What are the ACh steps?
- Acetylcholine is made from choline and acetyl CoA
- In the synaptic cleft ACh is rapidly broken down by the enzyme acetylcholinesterase
- Choline is transported back into the axon terminal and is used to make more ACh
What are adrenoreceptors?
when epinephrine or norepinephrine binds, they release G proteins, which begin a cascade of information
What are adrenoreceptors
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What are the subtypes of adrenoreceptors?
- alpha and beta, both are metabotropic
