Autonomic Nervous System: Structure, Function, and Regulation

What part of the nervous system does the Autonomic Nervous System (ANS) belong to?

Peripheral Nervous System (PNS)

What are the primary effectors of the ANS?

Cardiac muscle, smooth muscle, and glands

Is the Autonomic Nervous System under voluntary control?

No, it is not under voluntary control.

What are the two main divisions of the Autonomic Nervous System?

Sympathetic and Parasympathetic

What is the primary function of the sympathetic division?

Fight or flight response

What is the primary function of the parasympathetic division?

Rest and digest

How many neurons are involved in the Autonomic Nervous System pathway?

Two neurons: preganglionic and postganglionic

What neurotransmitter is released by somatic motor neurons?

Acetylcholine (Ach)

What neurotransmitters can autonomic neurons release?

Acetylcholine (Ach) and Norepinephrine (NE), among others

What is denervation hypersensitivity?

Increased sensitivity of target cells after nerve damage

What type of muscle can contract rhythmically without nerve stimulation?

Cardiac muscle and some smooth muscle

Where do sympathetic preganglionic neurons originate?

Thoracic and lumbar regions of the spinal cord

What is the sympathetic chain?

A series of interconnected sympathetic ganglia running parallel to the spinal cord

What are collateral ganglia?

Ganglia where some sympathetic neurons synapse, located below the diaphragm

What hormones does the adrenal medulla secrete?

Epinephrine and Norepinephrine

What is the effect of sympathetic activation on heart rate?

It increases heart rate

What type of receptors do all autonomic ganglia have?

Nicotinic acetylcholine receptors

What is the primary effect of adrenergic synapses?

They can be either excitatory or inhibitory depending on the receptor type

What is the difference in the number of neurons from CNS to effector between the somatic and autonomic systems?

Somatic has one neuron; autonomic has two neurons

What is the type of neuromuscular junction in the somatic motor system?

Specialized motor end plate

What is the effect of nerve impulse on muscle in the somatic motor system?

Always excitatory

What are the types of nerve fibers in the somatic motor system?

Fast-conducting, thick, and myelinated

What happens to muscle tone and function in the autonomic system after denervation?

Muscle tone and function persist; target cells show denervation hypersensitivity

What is the origin of the sympathetic division?

Thoracolumbar origin

What is the craniosacral origin associated with?

Parasympathetic division

What is the role of preganglionic neurons in the sympathetic division?

They synapse in sympathetic ganglia and are myelinated

What is the role of postganglionic neurons in the sympathetic division?

They are unmyelinated and travel to effectors

What are the two types of β receptors?

β1 and β2

What second messenger do β receptors primarily use?

cAMP

What second messenger do α receptors primarily use?

Ca2+

What is the effect of activating phospholipase C in smooth muscle?

Increased IP3 and DAG leading to increased Ca2+ and smooth muscle contraction

Where are α2 receptors located?

On presynaptic axons

What is the effect of α2 receptor activation on norepinephrine release?

It inhibits norepinephrine release, resulting in vasodilation

What is clonidine and its primary effect?

An α2 agonist that lowers blood pressure

What adrenergic receptor is responsible for pupil dilation?

α1 receptors

Which adrenergic receptor increases heart rate and contraction strength?

β1 receptors

What effect do β2 adrenergic receptors have on bronchioles?

They cause bronchioles to dilate due to smooth muscle relaxation

What is the role of α1 receptors in the skin and visceral vessels?

They cause arterioles to constrict due to smooth muscle contraction

What is the function of the vagus nerve in the parasympathetic division?

It innervates several organs including the heart, lungs, and gastrointestinal tract

What neurotransmitter is released by all preganglionic neurons?

Acetylcholine (ACh)

What are the two types of cholinergic receptors?

Nicotinic and Muscarinic

What is the effect of nicotinic ACh receptors?

They are always excitatory and present in all autonomic ganglia

What is the primary function of muscarinic ACh receptors?

They can be excitatory or inhibitory and are involved in various autonomic functions

What are varicosities in the context of the autonomic nervous system?

Swellings on postganglionic axons that release neurotransmitters along the axon

What is the origin of preganglionic neurons in the parasympathetic division?

The brain stem and sacral region of the spinal cord

What is the typical length of preganglionic and postganglionic axons in the parasympathetic division?

Very long preganglionic axon and very short postganglionic axon

What is the primary effect of the parasympathetic division on the body?

It allows the body to 'rest and digest', slowing heart rate and increasing gastrointestinal activities

What is the role of the oculomotor nerve in the parasympathetic division?

It controls the ciliary muscle and sphincter muscle of the iris

What is the effect of atropine in cholinergic transmission?

It blocks muscarinic receptors, reducing secretions and treating overactive bladder

What adrenergic drug is used as a vasoconstrictor and nasal decongestant?

Phenylephrine

What is the effect of terbutaline and albuterol?

They dilate bronchioles to treat asthma

What are the two main types of cholinergic receptors?

Nicotinic and Muscarinic receptors

What is the response of nicotinic receptors in skeletal muscle to acetylcholine (ACh)?

Depolarization, producing action potentials and muscle contraction

What type of receptors are activated by ACh in smooth muscle and glands?

Muscarinic receptors (M3, M5)

What is the effect of ACh on the heart via muscarinic receptors?

Hyperpolarization, slowing the rate of spontaneous depolarization

What neurotransmitters are released by nonadrenergic, noncholinergic fibers?

ATP, Vasoactive intestinal peptide (VIP), Nitric oxide (NO)

Where are sympathetic ganglia located?

Near the central nervous system (CNS)

What is the length of preganglionic and postganglionic neurons in the sympathetic system?

Very short preganglionic neuron and long postganglionic neuron

Where are parasympathetic ganglia located?

Near or inside the target organ

What is the effect of the sympathetic nervous system on the heart?

Increases heart rate and contractility

What is the antagonistic effect in autonomic regulation?

When both sympathetic and parasympathetic divisions oppose each other's effects

What is an example of a cooperative effect between sympathetic and parasympathetic systems?

Erection (parasympathetic) and ejaculation (sympathetic)

What is the role of the medulla oblongata in autonomic regulation?

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

What are the effects of stretch receptors in the lungs?

Inhibit further inhalation; stimulate increase in heart rate and vasodilation

What is autonomic dysreflexia?

A serious condition causing stroke, pulmonary edema, and myocardial infarction in individuals with spinal cord injuries at or above T6

What happens immediately after a spinal cord injury?

Loss of spinal reflexes below the level of the injury

What is the effect of aging on the sympathetic nervous system?

Increased levels of sympathetic activity and sympathetic tone, raising the risk for hypertension and cardiovascular diseases

What is the response of the gastrointestinal tract to sympathetic stimulation?

Relaxes smooth muscle walls and constricts sphincters

What is the effect of parasympathetic stimulation on salivary secretion?

Stimulates secretion of watery saliva

What happens to the urethral sphincter during parasympathetic stimulation?

Relaxes

What is the role of the hypothalamus in autonomic function?

Regulates body temperature, hunger, thirst, and the pituitary gland

What is the effect of sympathetic stimulation on blood vessels in the skin?

Contracts (vasoconstriction)

What is the effect of parasympathetic stimulation on the bladder wall?

Contracts slightly

What neurotransmitter is involved in the erection process?

Acetylcholine (ACh) via parasympathetic stimulation

What is the effect of nitric oxide (NO) in the body?

Produces smooth muscle relaxation in various organs

What is the effect of ACh on bronchial smooth muscle?

Contracts (bronchoconstriction) via muscarinic receptors

What is the effect of sympathetic stimulation on the heart's sinoatrial node?

Increases heart rate via beta-1 receptors

What is the effect of parasympathetic stimulation on the heart's contractility?

Decreases contractility via muscarinic receptors