The autonomic Nervous System

What is the autonomic nervous system?

1. visceral motor system

   1. motor nervous system that controls glands, cardiac muscle, and smooth muscle

what are the primary target organs of the ANS?

1. viscera of the thoracic and abdominal cavities

2. some structures of the body wall: cutaneous blood vessels, sweat glands, and arrector pili muscles

Does the ANS carry out actions voluntarily or involuntarily?

Involuntarily

True or false: visceral effectors depend on the ANS to function.

False; ANS is only to adjust their activity to the bodys needs

what happens if you sever ANS nerves to an organ?

Denervation hypersensitivity=organ becomes extra sensitive because its no longer being regulated by the ANS

what is a visceral reflex?

unconscious, autonomic response to stimuli involving visceral receptors and effectors, controlled by ANS

what is an example of a visceral reflex?

Baroreflex; helps control blood pressure

what are the five steps of a visceral reflex?

1. Receptor-detects stimulus (e.g. baroreceptors sense blood pressure)

2. Afferent neuron- carries sensory signal to the brain

3. integrating center-processes info (e.g. medulla oblongata)

4. Efferent neuron- sends command from the brain

5. effector-carries out the response (e.g. glands, smooth muscle)

What are the two divisions of the ANS?

1. Sympathetic division

2. parasympathetic division

what does the sympathetic division do?

Prepares the body for physical activity=increases heart rate, breathing, and send blood to muscles

what does the parasympathetic division do?

Promotes digestion, rest, and waste elimination- slows the heart an helps the body recover

what is autonomic tone?

the normal background level of activity from both the sympathetic and parasympathetic systems that adjusts to the bodys needs

True or false: either sympathetic or parasympathetic, when one is working the other is not.

False; both are always active, just alternate their levels of activity based on bodies needs

what is parasympathetic tone responsible for?

Keeps intestinal muscles moving and mainitains resting heart rate

what is the sympathetic tone responsible for?

keeps blood vessels partially constricted to help maintain blood pressure

how many neurons are in a somatic motor pathway?

Just One- straight from the spinal cord to the muscle

what kind of fiber does the somatic pathway use?

myelinated fiber, sends signal very quickly

how many neurons are in an autonomic motor pathway?

Two — a preganglionic and a postganglionic neuron

what is a ganglion in the autonomic pathway?

The “layover” spot where the first neuron (preganglionic) synapses with the second (postganglionic)

what does the autonomic pathway control?

involuntary stuff — heart, smooth, glands, etc..

in parasympathetic motor innervation, what is the length of the preganglionic fiber?

Long

true or false; in autonomic output pathways, the preganglionic fiber is always myelinated?

True

True or false: the postganglionic fiber is always unmyelinated

True

where is the parasympathetic ganglion located?

Near or in the target organ

what is the postganglionic fiber like in the parasympathetic pathway

short anf unmyelinated

in the sympathetic motor innervation, what is the preganglionic fiber like?

short and myelinated

where is the sympathetic ganglion usually located

near the spinal cord

what are the postganglionic fibers like in the sympathetic pathway?

long and unmyelinated

what neurotransmitter is released by all preganglionic neurons? in both parasympathetic and sympathetic divisions

Acetylcholine

what neurotransmitter is released by parasympathetic postganglionic neurons?

Acetycholine

Neurons that secrete acetylcholine are called?

cholinergic neurons

receptor that binds acetylcholine are called?

cholinergic receptors

what neurotransmitter is released by most sympathetic postganglionic neurons?

norepinephrine

nerve fibers that secret norepinephrine are called?

adrenergic fibers

receptors that binds norepinephrine are called?

adrenergic receptors

what are the two types of cholinergic receptors?

Muscarinic and Nicotinic receptors

where are the muscarinic receptors found?

cardiac muscle, smooth muscle, an glands with parasympathetic input

Do muscarinic receptors always excite?

no, they can excite or inhibit

what kind of system do muscarinic receptors use?

Second messenger systems like cAMP

where are nicotinic receptors found?

postganglionic neurons, adrenal medulla, skeletal muscles

do nicotinic receptors always excite or inhibit?

always excite

How do nicotinic receptors work?

they open ligand-gated ion channels to create excitatory postsynaptic potentials

what are the two types of adrenergic receptors?

1. alpha

2. beta

do adrenergic receptors use second messenger systems?

Yes, both alpha and beta use sms

do alpha adrenergic receptors use cAMP?

No, they use other second messengers

are alpha adrenergic receptors usually excitatory or inhibitory?

usually excitatory

what are the alpha adrenergic receptor subtypes?

alpha 1 and alpha 2

do beta receptors use cAMP?

Yes

are beta adrenergic receptors usually excitatory or inhibitory?

usually inhibitory

what is dual innervation?

when both sympathetic and parasympathetic systems send nerve fibers to the same organ

what are antagonistic effects in dual innervation?

when the two systems have opposite effects (e.g. heart rate one increases and the other decreases)

Give an example of antagonistic effects.

heart rate— sympathetic speeds it up, parasympathetic slows it down

what are cooperative effect in dual innervation?

when both systems work together to produce a single unified effect

example of cooperative effects.

saliva: parasympathetic makes serous (watery) and sympathetic makes mucous (thick) together result in saliva production

what does control without dual innervation mean?

when only one ANS division controls an organ by changing firing rate. Usually sympathetic division

name effectors controlled by sympathetic system

adrenal medulla, sweat glands, erector pili, most blood vessels

what happens to blood vessels when sympathetic firing rate increases?

vasoconstriction-narrow

what happens to blood vessels when sympathetic firing rate decreases?

vasodilation-widen

do blood vessels receive parasympathetic innervation?

no, only sympathetic innervation