Week 13 - ANS Flashcards
What does ANS control
Internal organs, blood flow, smooth muscles of the eye, vescera, etc
2 subsystems of the ANS
sympathetic and parasympathetic
sympathetic
fight or flight
parasympathetic
rest and digest
What does ANS work with
Works with endocrine and behavioural state sytems to maintain homeostasis
What all does ANS deal with
more than just fight or flight emergencies
exercise, emotion, effect if gravity, eating, etc
what can ANS be divided into
preganglionic and post ganglionis components
where are preganglionic neuron cell bodies located
CNA, either in brainstem or spincal cord
where do preganglionic axons project
ganglia (postganglionic neurons) located between the CNS and the target tissue
where do post ganglionic neurons project
target tissue
what do the general features of ANS help with
allows for divergence
what do both sympathetic and parasympathetic neurons release
Ach onto nicotinic receptors
what do most postganglionic sympathetic neurons secrete
Norepinephrine on adrnergic receptors
what do most postganglionic parasympathetic neurons secrete
Acetylcholine onto muscarinic receptors
where do sympathetic preganglionic neurons originate
thoracolumbar spinal cord
how are sympathetic ganglia linked together
sympathetic chain
which sympathetic neurons are short and which are long
short preganglionic neurons to sympathetic chain
long post ganglionic neurons from chain to effector organs
where do parasympathetic preganglionic neurons originate from
brainstem or sacral spinal cord
which parasympathetic neurons are short and which are long
long preganglionic neurons to ganglia near effector organ
short post ganglionic neurons from ganglia to effector oragsn
where do preganglionic sympathetic efferents come from
intermedio-lateral horn of thoracic cord
they synapse in chain of ganglia parallel to cord
what is the transmitter for symapthetic preganaglionic efferents
acetylcholine
what is postganglionic sypathetic efferents project to and what is their transmitter. exception???
postganglionic sympathetic efferent project to taget tissue, the transmitter is noradrenaline
exception: ACh is tramsitter at skin sweat glands
8 sympathetic activities
- fight or flight response
- prepare for emergency, stress, exercise
- increase heart rate, blood pressure
- mobilize energy stores
- pupillary dilation
- diffuse effect due to its widespread and interconnected innervations
- decreased gastrointestinal and urinal function
- releases epinephrine/adrenaline
adrenal medulla
specialized neuroendocrine tissue acting with the sympathetic nervous system
sometimes described as modified sympathetic ganglion
how is epinephrine released from adrenal medulla
preganglionic sympathetic neuron synapses onto chromaffin cells of adrenal medulla and epinephrine is released
where do parasympathetic efferents originate
originate in several cranial motor nuclei (III, VII, IX, X) and intermediolateral part of sacral cord
what do parasympathetic efferents project to
ganglia embedded in target organ eg. sacral node of heart, enteric nervous system of gut
what is the transmitter of parasympathetic efferents ? exception?
Acetylcholine
exception is NO (penile erection)
parasympathetic activities
- quiet, relaxed states
- active in rest and digest
- increase gastrointestinal activities
- decrease heart rate and blood pressure
duel innervation
tonic acitivty at rest, both branches active , both systems complementary rather than antagonistic
what dominated in duel innervations
parasympathetic nervous system
targets of autonomic neurons
smooth muscle, cardiac muscle, glands
neuroeffector junction
the synpase between the post ganglionic automic neurons with its target cells
varicosities
axon swelling, contains vesicles filed with neurotransmitters
what metaboluzes norepinephrine
monoamine oxidase
how is exocytosis at synpatic besicles triggered
Ap arrives at varicosity. depolarisation open the voltage gated Ca2+ channels, its entry triggers exocytosis of synpatic vesicles
what happens after synaptic vesicle exocytosis is triggered
Norepinephrine binds to adrenergic receptor on target. Receptor activation ceases when NE diffuses away from the synapse. NE is removed from the synapse, it cna be taken back into synaptic vesicles for re-release.
whats used to produce functional reflexes
autonomic efferent networks
autonomic reflex - feedback loop
good examples of negative feedback loops
overall goal is to maintain homeostatsis
where is pupillary light relfex organized
pretectal area of midbrian
what does pupillary light reflex use
On and OFF afferents to luminance and darkness detectors
what happens when its too bright
parasympathetic reflec via cranial nerve 3 to ciliary ganglion and circular iris muscles
what happens when its too dakr
sympathetic reflex via thoracic cors, sympathetic chain to radial muscles
what can fool the eye
brightness illusion
pupils rapidly contrict when glancing at a brighter image and then rapidly readjust to true light intensity
where does barorelflex happen
cardiovascular centre
ventrolaterla medulla, beside respiratory centre
what does the baroreflex include
NTS- nucleus of the solitary traact
what revieves information from baroreceptors and where does it send informations
NTS recieves information from baroreceptors and sends informations to ventrolateral medulla
when does blood pressure drop
claudal half inhibits rostral half
when does blood pressure and heart rate increase
when rostral half excited sypathetic efferents
what is the major influence for muscle sympathetic effects
noradrenergic vasoconstrictiion, tonically active to maintain. blood pressure.
what parts of autonomic control centre are fed by sensory information
hypothalamuc, pons and medulla
what does brainstem contain
control centers: cardiovascular center, and repiratory pattern generator in lateral medulla/pons
It receives sesory input and relays output to muscles, glands, etc
PAG - Periaqueductal Gray
midbrain premotor centre for automic behaviour programs
where is peraqueductal gray found
midbrain
heavy interaciton w hypothalamus
what does PAG act through
reticular formation and hypothalamuc
how does reticular activating system result in a global shift in CNS acitivty (metabotropic mech)
via diffuse modulatory system
how is PAG organized
longitudinal columns according to behaviour pattern
eg. fight rage column projects to cardiovascular centre in medulla, and raphe which releases serotonin in the spinal cord>depolarizes all motor neurons, inhibits transmissions in dorsal horn
modulatory systems
cholinergenic, serotonergic, adrenergic, dopaminergic, histaminergic
cholinergic
determines level of attention, sleep-wake cycle, arousal, learning, memory through thalamuc, mainly ascending
serotonergic
lower nuclei: pain, locomotion
upper nuclei: sleep-wake cycle, mood and meotional behaiours (agression and depression)
noradrenergic
attention, arousal, leanring, memory, anxiety, pin, mood
where do serotonergic neurons originate
raphe nuclei along brainstem midline
dopaminergic
reward centre
where do noadrenergic nerons originate
locus coreoulus of pons
where dopaminergic neurons originate
- substantia nigra in midbrain
- ventral tegmentum in midbrain
histaminergic
sleep wake control, support waking state
where do histaminergic neurons originate and project
originate in posterior thalamus
project throughout forebrain and others
