Ch. 9: Autonomic Nervous System

What are do autonomic neurons do

Innervate organs not under voluntary control

What are the three effector organs of the autonomic neurons

cardiac muscle, Smooth muscle of visceral organs and blood vessels, and Glands

Neurons are motor, but there are sensory neurons from

the viscera for control

Somatic motor neurons have

cell bodies in the spinal cord and just one neuron traveling from spinal cord to effector.

The autonomic motor system has two sets of neurons in the PNS: The first has

cell bodies in the brain or spinal cord and synapses in an autonomic ganglion

The autonomic motor system has two sets of neurons in the PNS: The second has

cell bodies in the ganglion and synapses on the effector

Preganglionic neurons originate in the

midbrain or hindbrain or from the thoracic, lumbar, or sacral spinal cord (CNS)

Postganglionic neurons originate in the

ganglion (PNS)

Autonomic ganglia are located in the

head, neck, and abdomen as well as in chains along either side of the spinal cord

Somatic motor neurons release only

acetylcholine which is always excitatory.

Autonomic neurons release mainly

acetylcholine and norepinephrine but may be excitatory or inhibitory

Neurons in the somatic nervous system can be up to 10x larger than

autonomic nervous system neurons

What are the two divisions of the Autonomic Nervous System

the Sympathetic and Parasympathetic Divisions

What's another word for the sympathetic division of the ANS

The Thoracolumbar division

sympathetic Preganglionic neurons come from the

thoracic and lumbar regions of the spinal cord.

sympathetic Preganglionic neurons synapse in

sympathetic ganglia that run parallel to the spinal cord; These are called the paravertebral ganglia. These ganglia are connected, forming the sympathetic chain of ganglia

Splanchnic nerves continue through the paravertebral ganglia and make their first synapse at a

collateral ganglion.

Because preganglionic neurons can branch and synapse in ganglia at any level, there is

Divergence and Convergence

What is Divergence

One preganglionic neuron synapses on several postganglionic neurons at different levels.

What is Convergence

Several preganglionic neurons at different levels synapse on one postganglionic neuron.

Convergence Allows the sympathetic division to act as a

single unit through mass activation and to be tonically active

The adrenal medulla secretes epinephrine and norepinephrine when stimulated by the sympathetic nervous system as a part of

mass activation

Embryologically, the adrenal medulla is a modified ganglion and is innervated directly by

preganglionic sympathetic neurons.

What's another word for the parasympathetic division of the ANS

Craniosacral division

parasympathetic Preganglionic neurons come from the

brain or sacral region of the spinal cord.They synapse on ganglia located near or in effector organs; called terminal ganglia

parasympathetic Preganglionic neurons do not travel

with somatic neurons (as sympathetic postganglionic neurons do). Terminal ganglia supply very short postganglionic neurons to the effectors

What four cranial nerves have autonomic system functions

The oculomotor (III), facial (VII), glossopharyngeal (IX), and (X) vagus nerves

The oculomotor, facial, glossopharyngeal, and vagus nerves carry

parasympathetic preganglionic neurons.

The facial (VII) and glossopharyngeal (IX) nerves stimulate

flow of saliva

The Oculomotor Nerve (III) constricts the

pupils

The Vagus Nerve has effects on varying organs, it

constricts bronchi, slows heartbeat, stimulates peristalsis, stimulates bile release, and contracts bladder.

Preganglionic nerves from the sacral region of the spinal cord provide innervation to the lower part of the

large intestine, rectum, urinary and reproductive organs. Terminal ganglia are located within these organs.

The sympathetic division activates the body for "fight or flight" through the release of

norepinephrine from postganglionic neurons and the secretion of epinephrine from the adrenal medulla.

The flight or fight response Prepares the body for intense physical activity in emergencies by

Increasing heart rate and blood glucose levels and by diverting blood to skeletal muscles; Tonically regulates heart, blood vessels, and other organs

The parasympathetic division is antagonistic to the

sympathetic division.

The parasympathetic system allows the body to

"rest and digest" through the release of ACh from postganglionic neurons; Slows heart rate, and increases digestive activities

Acetylcholine (ACh) is the neurotransmitter used by all

preganglionic neurons (sympathetic and parasympathetic)

Acetylcholine is also It is also the neurotransmitter released from

parasympathetic postganglionic neurons.

Some sympathetic postganglionic neurons that innervate sweat glands and skeletal muscle blood vessels) release ACh. These synapses are called

cholinergic

Norepinephrine is the neurotransmitter released by most sympathetic postganglionic neurons. These are synapses are called

adrenergic

Axons of postganglionic neurons have various swellings called

varicosities that release neurotransmitter along the length of the axon.

Sympathetic and parasympathetic neurons innervate the same tissues but release different

neurotransmitters

Response to adrenergic stimulation can be

epinephrine in the blood or norepinephrine from sympathetic nerves; Can stimulate or inhibit, depending on receptor

What are the two types of α (alpha) Adrenergic receptors

α1 and α2

What are Three types of β (beta) Adrenergic receptors

β1 β2 and β3

α and β Adrenergic Receptors act using

G-proteins and second messenger systems

α receptors use a

Ca2+ second messenger system to constrict organs

What do α1 receptors do

they Constrict blood vessels

(vasoconstriction)

What do α2 receptors do

they inhibit the release of Norepinephrine

β receptors uses

cAMP to dilate organs

What do β1 receptors do

Increase contraction, contractility, HR

What do β2 receptors do

relax smooth muscle of bronchiole muscle

What do β3 receptors do

regulate metabolism (brown fats)

Alpha receptors are more sensitive to

norepinephrine

Beta receptors are more sensitive to

blood epinephrine

Agonists are drugs that

promote the process stimulated by the NT

Antagonists are drugs that

block the action of the NT

ACh released from preganglionic neurons of both the sympathetic and parasympathetic division is

stimulatory.

ACh from postganglionic neurons of the parasympathetic division is

usually stimulatory, but some are inhibitory, depending on receptors.

In general, sympathetic and parasympathetic effects

are antagonistic

Where are nicotinic receptors found

in autonomic ganglia

Nicotinic receptors Serve as

ligand-gated ion channels for Na+ & K+ = Ionotropic receptors; blocked by curare

Where are muscarinic receptors found in

visceral organs and stimulated by release of Ach from postganglionic neurons

Muscarinic receptors can be

stimulatory or inhibitory (opening K+ or Ca2+ channels); Use G-proteins and second messenger system = Metabotropic receptors; Blocked by atropine

Most visceral organs are innervated by both

sympathetic and parasympathetic neurons.

The parasympathetic system causes

heart rate to decrease, digestive functions to increase, and pupil diameter to decrease

What are complimentary effects

when both divisions produce similar effects on the same target (Ex: salivary gland secretion: Parasympathetic division stimulates secretion of watery saliva; sympathetic constricts blood vessels so the secretion is thicker.)

What are Cooperative effects

when both divisions produce different effects that work together to promote a single action. (Ex: Erection and ejaculation: Parasympathetic division causes vasodilation and erection; sympathetic causes ejaculation)

What organs are only intervated by the sympathetic division

Adrenal medulla, Arrector pili muscles in skin, Sweat glands in skin, Most blood vessels; Regulated by increase and decrease in sympathetic nerve activity; Important for body temperature regulation through blood vessels and sweat glands

Many visceral functions are regulated by

autonomic reflexes.

Sensory input is sent to brain centers (usually by the vagus nerve), which integrate the information and modify the activity of

preganglionic neurons.

The Medulla oblongata controls

many cardiovascular, pulmonary, urinary, reproductive, and digestive functions.

The Hypothalamus controls

major regulatory center of the ANS - body temperature, hunger, thirst, pituitary gland

The Limbic system is responsible for

autonomic responses during emotional states (blushing, pallor, fainting, cold sweating, racing heart rate)

The Cerebellum controls

motion sickness nausea, sweating, cardiovascular changes

The Frontal & temporal lobes control

emotion and personality

What two things is aging associated with

increased levels of sympathetic activity, and Increased sympathetic tone

in the lungs we have stretch receptors that

respond to lung inflation by sending signals via the vagus nerve to the brainstem.

In the aorta we have chemoreceptors and baroreceptors where

baroreceptors act as pressure sensors, detecting changes in blood pressure, while chemoreceptors monitor blood chemistry, sensing levels of oxygen, carbon dioxide, and pH

The heart has atrial and stretch receptors that

detect increased blood volume and pressure (atrial stretch) and trigger the Bainbridge reflex.

The gastrointestinal tract has stretch receptors that

detect distension (stretching) from food or feces

What is Autonomic Dysreflexia

a life-threatening medical emergency that can occur in people with spinal cord injuries (SCIs) above the sixth thoracic vertebra (T6).

as we get older there is an Increased risk for

hypertension and cardiovascular diseases

What is adrenaline

also known as epinephrine, is a hormone that plays a crucial role in the body's "fight or flight" response.

What is noradrenaline

also known as norepinephrine, is a neurotransmitter and hormone that plays crucial roles in various bodily functions.

What is dopamine

a chemical messenger in the brain . It plays a key role in movement, motivation, learning, reward, and mood

What is serotonin

mood NT that contributes to well being and happiness;

What is GABA

the calming NT that calms firing nerves in the CNS, high levels improve focus

What is Glutamate

the memory NT, being the most common NT involved in learning and memory

What are endorphins

the Euphoria NT, released during exercise, excitement & sex, producing well-being & euphoria, reducing pain

What is the Olfactory (I) nerve responsible for

Sense of smell

What is the Optic (II) nerve responsible for

Sense of vision

What is the Oculomotor (III) nerve responsible for

Moves the eye (most extraocular muscles), constricts the pupil, and controls the upper eyelid

What is the Trochlear (IV) nerve responsible for

Moves the eye down (superior oblique muscle)

What is the Trigeminal (V) nerve responsible for

Sensation (pain, temperature, touch) for the face, scalp, and teeth (three main branches: ophthalmic, maxillary, mandibular); controls muscles of mastication (chewing)

What is the Abducens (VI) nerve responsible for

Moves the eye horizontally (lateral rectus muscle)

What is the Facial (VII) nerve responsible for

Controls muscles of facial expression; provides the sense of taste for the anterior two-thirds of the tongue; controls salivary and lacrimal (tear) glands

What is the Vestibulocochlear (VIII) nerve responsible for

Sense of hearing and balance (equilibrium)

What is the Glossopharyngeal (IX) nerve responsible for

Sense of taste for the posterior one-third of the tongue; controls the pharynx (swallowing); monitors blood pressure and O2 /CO2 levels in the blood

What is the Vagus (X) nerve responsible for

It controls muscles for swallowing and speaking; provides parasympathetic control to the heart, lungs, and digestive tract