day 13 Autonomic Nervous System

autonomic nervous system

is concerned with maintaining homeostasis within the body by increasing or decreasing the activity of various organs in response to changing physiological conditions

-        Regulates homeostasis

Sympathetic

• prepares body for physical activity (arousal, competition, stress, danger, anger or fear)

• “Fight or Flight” or Thoracolumbar

what happens to your body with sympathetic

-        Increased heart rate

-        Increased blood pressure

-        Increased respiratory rate

-        Increased blood sugar glucose

-        Mental awareness increases

-        Pain signals decrease

-        Pupils dilate, increasing visual acuity

-        Decreased digestion and urinary

lateral horns are only found in which sections

T1-L2

motor neurons only come out of which sections

T1-L2

are motor neurons found in the sympathetic nervous system

no

it doesn’t come out of anywhere else in the spinal cord besides T1-L2

Parasympathetic

• calming of body

• ”Rest and Digest” or Craniosacral

what happens to your body with parasympathetic

-        Lower heart rate

-        Lower blood pressure

-        Lower respiratory rate

-        Increased digestion, nutrient absorption, storage of nutrients

-        Increasing gland secretion

-        Increase urination and defecation

-        Pupils are constricted

where do motor neurons come out of for parasympathetic

either cranial nerves or the sacral region

motor neurons that come out of the cranial area/nerves are

parasympathetic

motor neurons that come out of the cervical are

neither sympathetic or parasympathetic

motor neurons that come out of the thoracic and T1-L2 of the lumbar are

sympathetic

motor neurons that come out of sections L3-I4-I5 are

neither sympathetic or parasympathetic

motor neurons that come out of the sacral region are

parasympathetic

ganglion

area where two neurons synapse

preganglionic neuron

• cell bodies in the lateral gray horns of spinal segments T1-T12 and L1, L2; axons are myelinated

•   enters into the ganglion through a white ramus (myelinated)

autonomic ganglia

• sympathetic chain ganglia (paired (meaning both sides) – 3 cervical, 11 thoracic, 5 lumbar, 5 sacral, 1 coccyx)

• preganglionic nerve fibers enter the chain ganglia via white rami (ramus)

collateral ganglia - celiac, superior mesenteric, inferior mesenteric

-        They are not paired

-        They are found anterior to the spinal cord

-        they go to organs and tissues that are in the abdominal cavity

-        they come out of the spinal cord between T1-L2, coming out of the lateral column

-        travels through without stopping through a sympathetic chain ganglia

-        synapses inside of a collateral ganglia

adrenal medullae

-        travels through a sympathetic chain ganglia and through collateral ganglia and synapses directly on the adrenal medulla with multiple different neurons

-        releases both epinephrine and norepinephrine (neurotransmitters)

postganglionic neurons

• Axons unmyelinated; fibers long

• Leaving the ganglion through a gray ramus (unmyelinated) and going to the effector

pathways of ANS nerve fibers

• Chain ganglia

• Collateral ganglia   (celiac, superior mesenteric and inferior mesenteric)

• Adrenal medullae

§  A single sympathetic preganglionic fiber has many axon collaterals and may synapse with 20 or more postganglionic fibers; then postganglionic fibers may innervate several visceral effectors (Widespread response)

what does this mean?

-        This allows one neuron to have a widespread effect on multiple effector cells

-        One message goes to multiple post ganglions neurons which goes to multiple effector cells

-        Widespread effect

-        This also activates the adrenal medullae since this is releasing epinephrine or norepinephrine into the bloodstream

preganglionic neuron

cell bodies in the nuclei of the four cranial nerves that initiate in the brain stem (III, VII, IX, X) and segments S2-S4

cranial nerve III

oculomotor – pupil diameter - For parasympathetic, it will decrease the size of pupils

cranial nerve VII

facial – controls submandibular salivary glands

cranial nerve IX

glossopharyngeal – controls parotid salivary gland

cranial nerve X

vagus – controls cardiovascular, respiratory, and digestive

S2-S4

goes to reproductive, bladder, and colon

types of ganglionic neurons

terminal ganglia

intramural ganglia

terminal ganglia

§  they go near target organs but they’re not on it (ciliary (III), pterygopalatine (III), submandibular (VII), and otic (IX))

intramural ganglia

embedded in the wall of the target organ (they go to the target organ)

postganglionic neurons

• Postganglionic fibers are short passing between the terminal and intramural ganglia and the target organ; - synapses with only 4 to 5 postsynaptic neurons from one effector (Localized response)

-        Example being: it can increase your digestive system without having to lower your heart rate at the same time

neurotransmitters

what sends signals from the neuron to whatever the next cell (chemical signal)

all preganglionic sympathetic neurons release

ACh (cholinergic)

postganglionic neurons have what receptors for ACh

nicotinic receptors for ACh

varicosities

adrenergic neurons can release what

norepinephrine (NE): released by sympathetic postganglionic

adrenergic receptors can bind ____

either NE released by adrenergic neurons or epinephrine released by adrenal gland

a1 - excitatory

• open up sodium channels (muscle = contraction)

• smooth muscle and blood vessels

a2 - inhibitory

• inhibiting the parasympathetic response

• if we want to ramp up sympathetic, we’d need to turn down the parasympathetic

b1 - excitatory

-        Heart and liver

-        Liver – increase metabolic activity (increased blood sugar

-        Heart – increase heart rate and contractility

b2 - inhibitory

-        Inhibits airway smooth muscle – causes bronchodilation (bronchi of the airway gets bigger, meaning airway gets bigger)

b3 - excitatory

-        Adipose tissue – cause lipolysis (breakdown of lipids for an energy source)

norepinephrine activity ends when

it is taken up by the presynaptic cell and broken down by MAO or diffuses out of the cleft and is broken down catechol-O-methyltransferase (COMT)

norepinephrine

released by adrenergic neurons and the adrenal medulla, only a1 and a2

epinephrine

released by adrenal glands, only b1, b2, b3

which is used for emergencies: epinephrine or norepinephrine

epinephrine

cholinergic neurons release

acetylcholine (ACh)

where does ACh diffuse

across the synaptic cleft and binds with specific cholinergic receptors

nicotinic receptors are excitatory or inhibitory

excitatory

muscarinic receptors are excitatory or inhibitory

both excitatory or inhibitory

ex. heart rate can decrease but digestion can increase

dual innervation

when the viscera receives nerve fibers from both the sympathetic and parasympathetic divisions

• they both innervate the heart and based on who had the most binding will determine if the heart rate is decreasing or increasing

vasomotor control

only sympathetic

autonomic tone

balance in the activities of sympathetic and parasympathetic

• always releasing neurotransmitters but just different amounts

• -        meaning if you need to activate your sympathetic system, you can do so quickly because you already have sympathetic neurotransmitters being released and get a faster response

ANS receives input from what

CNS, but it doesn’t work in a vaccum

cerebral cortex

emotions and thoughts

hypothalamas

control center for the autonomic nervous system and regulates thirst and hunger and thermoregulation

midbrain, pons, medulla oblongata

contains your cardiac, vasomotor, respiratory center, salivation, swallowing, sweating

spinal cord

gives you reflexes for urination and defecation

visceral reflexes

unconscious, automatic responses to stimuli

reflex arc

receptor —> sensory neuron —> interneurons (1 or more) —> 2 visceral motor neurons

all visceral reflexes are (polysynaptic or monosynpatic)

polysynaptic