Unit 7 autonomic nervous system Flashcards
Peripheral nervous system subdivision
Somatic ns (voluntary actions) and autonomic ns ( involuntary)
Autonomic 2 subdivision
Parasympathetic psns (rest and digest): relaxing
Sympathetic sns (flight/fight): exercise, stress/scared
Homeostasis between psns and sns
When sns activity high, psns activity low vice versa
Autonomic nervous system pathway (preganglionic and postganglionic)
From cns to effectors
Composed of 2 multipolar neurons
Preganglionic= first in pathway, myelinated (from brain/spinal, to ganglion)
Post= 2nd in path, unmyelinated, from ganglion to smooth muscle
A toxin that destroys varicosities in nervous system will
Prevent stimulation of sweat glands
Decrease release of neurotransmitters from postganglionic neurons
Similarity between somatic and autonomic pathways
Acetycohaline is secreted from the neuoron that originates in the cns
Ending signalling by the neurotransmitter at the majority of sympathetic neuroeffector junctions:
Diffusion of norepinephrine away from the target cell
Breakdown of norepinephrine by MAO in the varicosity
neuroeffector junction
synapse between postganglionic neurons and effectors facilitated by varicosities (expanding axon terminals like beads on a string)
sympathetic nervous system (flight/fight):
1. location of cell bodies of preganglionic neurons,
2. location of autonomic ganglia
3. lengths of fibers
4. neurotransmitters released
- lateral horn in spinal cord of thoracic and spinal regions
- sympathetic chain ganglia and collateral ganglia
- pre fibers= short and axon terminal release acetylcholine
post fibers=long, and its axon terminal release NE
parasympathetic nervous system (rest and digest):
1. location of cell bodies of preganglionic neurons,
2. location of autonomic ganglia
3. lengths of fibers
- brainstem nuclei and lateral horn of spinal cord in sacral region
- terminal ganglia (outside or inside wall of organ/effector)
- pre fibers= long post fibers= very short
sns vs psns: neurotransmitter, receptor, synthesized from, varicosity membrane transfer for:
NE, Ach
alpha and beta adregernic, nicotinic and mosaninic
tyrosine, acetyl coA and choline
NE, choline
neurotransmitters (Ach)
released by preganglionic neurons, targets nicotinic receptors (NN) on postganglionic cells and chromatin cellsin the adrenal medulla
neurotransmitters (NE)
released by postganglionic neurons, interacts with alpha,beta adregernic receptors of the effector membrane
Sweat glands
Postganglionic neurons release Ach which activates M3 muscarinic receptors
pathway
- arrival of AP at the varicosity
- depolarization leading to opening 3 at the voltage ca channels
- Ca into cell
- exocytosis of NE facilitated by ca++
- NE crossing synaptic cleft to bind with adrenergic receptors (GPCR’s) on effector cells
- signal transduction occurs within the effector cell
SNS= longer lasting effects than psns because:
- Ach released by postganglionic PSNS neurons quickly degraded by Ach
- mechanisms to. remove/degrade NE from synapse are slower (NE is there longer)
Ach released by preganglionic neurons acts on…
Ach released by postganglionic neurons acts on…
Nn (N2) nicotinic receptors on the membrane of the postganglionic cell
muscarinic receptors in the effector membrane
Antagonist (opposite) effects
Common
Ex: heart
SNS heart rate up and force contraction via B adrenergic receptos
PSNS down heart rate and force of contraction via M2 Musurinic receptors
Synergistic effects (- sns and psns similar effects)
rare
Ex: salivary glands- both sns and psns stimulate secretions from salivary glands but:
Sns stimulates alpha and beta receptors for secretion of thick mucus
Psns stimulates muscarinic receptors that cause secretion of watery enzyme rich saliva
Complementary effects (opposite effects)
Rare
Ex: male reproduction response
Exampes of single innervation by ans
Adrenal medulla and sweat glands (sns only)
Give example of how hypothalamus dont need input for its ans functions but emotions cause autonomic effects
Blushing when embarrassed, sweat when nervous
