11. ANS Flashcards
Fiber connections of autonomic pathway involved in limbic system
- hypothalamus (centrally)
- via the fornix
- to temporal lobe
key functions of hypothalamus related to autonomic fibers
- via fornix to temporal lobe (limbic system)
- receive inputs from frontal lobe
- pituitary regulation (endocrine function)
- descending autonomics (via brainstem and spinal cord)
purpose of hypothalamus connecting descending pathway
Hypothalamus HAS to anatomically connect w/ the preganglionic neurons (sympathetic and parasympathetic system) in brainstem and spinal cord (via descending pathway (aka descending autonomics)
differences between somatic and autonomic efferents?
-
somatic efferent:
- CNS is lower (alpha) motor neuron
- single synapse
- voluntary muscle
-
autonomic efferent:
- CNS is preganglionic neuron
- two-synapse
- involuntary muscle and glands
autonomic nervous system: definition
network of neurons that regulates target organs in response to perturbation of homeostasis
ANS responses: key characteristics
- automatic
- involuntary
- unconscious
2 divisions of ANS, and the differences
-
sympathetic
- short-term mobilization during crisis
- short preganglionic, long postganglionic fiber
- ACh is key PREganglionic NT; Norepi is key POSTganglionic NT
-
parasympathetic
- long-term maintenance of body health
- long preganglionic, short postganlgionic fiber
- ACh is key pre- and post-ganglionics
although sympathetic division NT is usually ACh (preganglionic), and Norepi (postganglionic); what is a pathway that is an exception?
ACh can act on adrenal medulla, sending Epi (or NE, DA, peptides) via bloodstream –> to effector organ
IRIS:
Sympathetics/ parasympathetics?
- SNS: dilation of pupil
- Preganglionic: C8-T3
- Postganglionic: superior cervical ganglion
- PNS: constriction of pupil
- Preganglionic: Edinger-Westphal nucleus
- Postganglionic: ciliary ganglion (pupil constrictor)
Parotid gland:
Sympathetics/ parasympathetics?
- SNS: secretion is reduced and viscid
- preganglionic: T1-T3
- post-gang: superior cervical ganglion
- PNS: secretion increased and watery
- pre-gang: inferior salivatory nucleus
- post-gang: otic ganglion
heart & coronary vessels:
SNS & PNS
- SNS: increased HR; dilation or constriction of vessels
- pregang: T1-T5
- postgang: cervical and upper thoracic ganglia
- PNS: decreased HR; constriction of vessels
- pregang: dorsal vagal nucleus
- postgang: intracardiac ganglia
bronchi:
SNS and PNS
- SNS: dilation
- pregang: T2-T5
- postgang: upper thoracic ganglia
- PNS: constriction
- pregang: dorsal vagal nucleus
- postgang: pulmonary ganglia
stomach:
SNS and PNS
- SNS: inhibition of peristalisis & secretion
- pregang: T6-T10
- postgang: celiac ganglion
- PNS: inc. peristalsis & secretion
- pregang: dorsal vagal
- postgang: myenteric & submucosal ganglia
which sympathetic preganglionic fibers involve:
T1-T5?
heart and coronary vessels
which sympathetic POSTganglionic fibers involve:
superior cervical ganglion?
iris &
parotid gland
which sympathetic POSTganglionic fibers involve:
cervical and upper thoracic ganglia
heart and coronary vessels
which parasympathetic PREganglionic fibers involve:
dorsal vagal nucleus?
- heart
- coronary vessels
- bronchi
- stomach
portions of spinal cord associated wih parasympathetics?
cranial and sacral
portions of spinal cord associated wih SYMPATHETICS?
and pathway
- thoracic and lumbar (~T1-L2) –> preganglionics emerge
- pregang synapse in SYMPATHETIC TRUNK –>
- postganglionics travel –>
- to target organs & syanpse there
which ganglia/targets do the VAGUS nerve synapse with?
- cardiac ganglion –> heart
- bronchial ganglion –> lungs
- pulmonary ganglion –> lungs
- enteric ganglion –> stomach
sympathetic flow from CNS to target organ
- from lateral horn of spinal cord –>
- via visceral efferent fibers –>
- peripheral nerve –>
- white communicating ramus –>
- to sympathetic trunk –> a few possible paths
- @ spinal cord level: via gray communicating ramus to blood vessels/skin
- @ spinal cord level: to prevertebral ganglion –> viscera
- ascending thru sympathetic trunk
- descending thru sympathetic trunk
preganglionic spinal outflow to parasympathetic ganglia:
for ocular constrictor, glands, and vagus
- Edinger-westphal nucleus –> oculomotor nerve (CN III) –> pupil constrictor
- salivatory nuclei –> facial nerve (VII) and glossopharyngeal (IX) –> innervates glands
- doesal motor nucleus of vagus (X) & nucleus ambiguous –> vagus nerve –> outputs of vagus
sympathetic division effects, via descending autonomics
- ascends sympathetic chain –> stellate ganglion –> superior cervical ganglion –>
- eye –> dilates pupils
- lacrimal & salivary glands –> decreases salivation
- sympathetic chain –> heart & lungs –> inc respiratory & heart rate, & constricts BVs
- sympathetic chain –> celiac ganglion –> stomach –> inhibits digestive processes
parasympathetic division effects, via descending autonomics
from descending autonomics –>
- oculomotor nerve (CN 3) –> eye –> constricts pupil
- facial nerve (CN 7) & glossopharyngeal (9) –> parotid gland –> increases salivation
- vagus nerve (CN 10) –> lung –> decreases respiratory rate
- vagus nerve (CN 10) –> heart –> decreases HR
- vagus nerve (CN 10) –> stomach –> stimulates digestive processes
which parasympathetic nerve originates in :
MIDBRAIN
OCULOMOTOR (CN III) –> eye –> pupil constriction
which parasympathetic nerve(s) originates in :
PONS
- facial nerve (CN 7) –> parotid gland –> inc. salivation
- glossopharyngeal nerve (CN 9) –> parotid gland –> inc. salivation
which parasympathetic nerve originates in :
MEDULLA
vagus nerve --> dec. HR & resp rate, vasoDILATION, stimulates digestive processes
- cardiac g.
- bronchial g.
- pulmonary g.
- enteric g.
vasoDILATION / dilation of coronary vessels is a
(SNS or PNS) process
vasodilation is PARASYMPATHETIC; to decrease HR
(acts via vagus nerve)
hypothalamic input & output
- visceral sensory information from the body –> indicating perturbation in homeostasis
- issues a command (visceral motor command) thru descending autonomics to restore homeostasis
central and peripheral components of descending autonomics?
3 neurons in pathway from hypothalamus
- central = 1st order neuron of the descending autonomic pathway (hypothalamus, brainstem, spinal cord)
- peripheral = pre- and postganglionic autonomic neurons (2nd and 3rd order neurons)
CC: horner’s syndrome
cause and sxs
- lesion in descending SYMPATHETIC pathway –> dominance of parasympathetic
- sxs: loss of sympathetic tone to IPSILATERAL side
- pupil dilator: miosis (constricted pupil)
- tarsal: pstosis (drooping eyelid)
- sweat gland: anhidrois (lack of sweating)
CC: central horner’s VS preganglionic horner’s
- central horners: anhidrosis on ipsilateral body
- preganglionic horners: anhidrosis on ipsilateral face
visceral motor component(s) of the vagus nerve
- motor components - located in reticular formation; dorsal position in brainstem
- dorsal motor nucleus of vagus nerve
- nucleus ambiguous
actions of visceral motor component of vagus nerve
very important pathway – induces rest & digest in the following structures:
- innervate vessels to lung and heart
- cardiac muscle
- bronchial muscles
- smooth muscle of GI tract
- gastric secretions
autonomic reflex arcs:
define and key characteristics
- elicited by perturbations to fxn of ANS targets –>
- SNS and PNS are reciprocally engaged to restore homeostasis
- automatic and unconscious
list the autonomic reflex arcs
- ocular
- cardiovascular
- glandular
- GI system
- urogenital
pupillary light reflex pathway:
AFFerent limb
- afferent limb - sensory inputs
- retina, where light input is received
- optic nerve
- optic chiasm
- optic tract
- synapses in pretectal region of midbrain
pupillary light reflex pathway:
EFFERENT LIMB
efferent limb - motor inputs
- syanpse in pretectal nucleus of midbrain –> projects to
- Edinger-westphal component (PNS) of CN3/ oculomotor nuclear complex
- oculomotor nerve (CN 3)
- ciliary ganglion
- contriction of pupil
autonomic centers cardiac:
location, output, function
- medullary reticular formation –> sympathetic nucleus in spinal cord
- vasomotor cardioaccelerator and pressor
- medullary reticular formation –> neurons in dorsal vagal nucleus and reticular formation of medulla
- depressor and cardiodecelerator
principal autonomic centers: respiration
location, output, function
Autonomic centers in both medulla and pons:
-
medullary reticular formation –> phrenic, intercostal & abdominal motor neurons
- fxn: inspiration and expiration
-
pontine reticular formation –> medullary respiratory centers
- fxn: apneusis (prolonged inspiration) and pneumotaxis (control of expiration)
principal autonomic centers: emesis (vomiting)
location, output, fxn
- medullary centers –> emetic center, vagal & parasympathetic preganglionic neurons
- fxn: vomiting
possible triggers of the vomiting reflex
Reticular formation of medulla (vomiting center):
- blood borne toxins, etc –> acting on chemoreceptor trigger zone
- higher cerebral cortex (sensory input or memory/fear/anticipation) –> vomition center
- stomach and other viscera vagal and sympathetic afferents –> vomition center
principal autonomic centers: micturition
location, output, fxn
Controlled by pons –> fxn is micturition
- pontine reticular formation –> sacral parasympathetic neurons for detrusor contraction and inhibition of somatic motor efferent neurons and supplying sphincter
micturition reflex
- visceral afferents from stretch receptors (bladder) –> to spinal cord –>
- ascending tracts of spinal cord –> pontine micturition center (PMC)
- integration in PMC –> initiates micturition response –>
- descending pathways carry impulses to motor neurons of spinal cord
- MOTOR
- *PNS efferents stim contraction of detrusor muscle/ open urethral sphincter
- *sympathetic EFFERENTS to bladder are inhibited
- somatic motor efferents to external urethral sphincter are inhibited; sphincter muscle relaxes –>
- urine passes thru urethra adn bladder is emptied
