A&P II- Ch. 16 Objectives

autonomic nervous systems and organizations

Explain the basic function of the autonomic nervous system (ANS)

responsible for the involuntary regulation of body functions, controlling smooth muscle, cardiac muscle, and glands to maintain homeostasis.

List the three major divisions of the ANS and their primary functions

Sympathetic (fight-or-flight during activity, exercise, stress) Parasympathetic (rest-and-digest during rest) Enteric (controls digestive functions).

Describe the sympathetic division of the ANS and its effects on the body

more active during physical activity or stress, increasing heart rate, dilating airways, increasing glucose production, and blood flow to skeletal/cardiac muscle while decreasing digestion and urine production.

Explain the role of the parasympathetic division of the ANS

more active during resting conditions, decreasing heart rate, stimulating digestion and urine production, and constricting airways and pupils.

Compare the somatic nervous system and the autonomic nervous system in terms of control and function

controls skeletal muscle and is voluntary WHILE THE OTHER controls smooth muscle, cardiac muscle, and glands and is primarily involuntary.

Describe the structural differences between the somatic nervous system and the ANS

one system has 1 motor neuron from the CNS to muscle with one synapse; the other system has 2 motor neurons in series with two synapses.

Explain the neurotransmitters involved in the somatic nervous system and the ANS

acetylcholine (ACh) is released at the neuromuscular junction, while in the ANS, ACh or norepinephrine may be released depending on the division.

Describe the receptors found in the autonomic nervous system

nicotinic, muscarinic, α-adrenergic, and β-adrenergic receptors.

Explain the significance of myelination in the motor axons of the somatic nervous system and the ANS

In the somatic nervous system, the motor axon is myelinated, while in the ANS, the preganglionic axon is myelinated and the postganglionic axon is unmyelinated.

Describe the relationship between preganglionic and postganglionic neurons in the ANS

Consists of two neurons in series: preganglionic neuron originates in the CNS and synapses with the postganglionic neuron, which then innervates the target tissue.

Describe the role of the preganglionic neuron in the autonomic nervous system (ANS)

has its cell body in the CNS, and its axon travels from the CNS to an autonomic ganglion, where it releases acetylcholine (ACh).

Explain the function of the postganglionic neuron in the ANS

has its cell body located in an autonomic ganglion, and its axon travels from the ganglion to the target tissue, releasing either acetylcholine (ACh) or norepinephrine (NE).

Define the three divisions of the autonomic nervous system (ANS)

sympathetic division, parasympathetic division, enteric nervous system (ENS).

Describe the sympathetic division of the ANS

also known as the thoracolumbar division, has preganglionic neurons with cell bodies located in the lateral horns of the spinal cord at spinal cord levels T1–L2.

Explain the arrangement of sympathetic ganglia

includes sympathetic chain ganglia located along the spinal cord and collateral ganglia associated with splanchnic nerves, located farther from the spinal cord.

How do sympathetic axons travel to target organs

Sympathetic axons travel to target organs through four major routes: spinal nerves, sympathetic nerves, splanchnic nerves, and the adrenal gland.

Describe the parasympathetic division of the ANS

this division, also known as the craniosacral division, has preganglionic neurons with cell bodies located in the brainstem and sacral spinal cord (S2–S4).

Explain the characteristics of parasympathetic ganglia

called terminal ganglia, are located near or within the target organ, and the postganglionic neurons are relatively short, traveling from the terminal ganglion to the target tissue.

What is the memory trick for the sympathetic division of the ANS

Sympathetic = Thoracolumbar = T1–L2.

What is the memory trick for the parasympathetic division of the ANS

Parasympathetic = Craniosacral = Brainstem + S2–S4.

Define an autonomic nerve plexus

a network of autonomic nerves that distributes autonomic fibers to organs.

List the major autonomic nerve plexuses in the thoracic region

cardiac plexus pulmonary plexus esophageal plexus.

Identify the major autonomic nerve plexuses in the abdominopelvic region

celiac plexus superior mesenteric plexus inferior mesenteric plexus hypogastric plexus.

Explain the organization of the enteric nervous system (ENS)

this system consists of nerve plexuses within the wall of the digestive tract, containing sensory neurons, interneurons, and motor neurons.

Describe the functions of the enteric nervous system (ENS)

can stimulate or inhibit smooth muscle contraction, stimulate or inhibit gland secretions, detect changes in the contents of the digestive tract, and connect sensory and motor activity through interneurons.

How does the enteric nervous system (ENS) operate in relation to the central nervous system (CNS)

this system can function independently of the CNS through local reflexes, although it can be influenced by sympathetic and parasympathetic divisions.

Explain the role of the sympathetic division during activity or stress

produces the fight-or-flight response, preparing the body to respond quickly during activity or stress.

List the major effects of the sympathetic division on the body during stress

increased heart rate, increased blood flow to skeletal muscles and heart, dilated airways, dilated pupils, increased glucose production, increased metabolism/body temperature, decreased digestion, and decreased urine production.

Describe the shortcut for remembering the sympathetic division's effects

SPEED + ENERGY.

Explain the role of the parasympathetic division during rest

dominant during resting conditions and supports rest-and-digest functions.

List the major effects of the parasympathetic division on the body during rest

include decreased heart rate, constricted airways, stimulated digestion, increased glandular secretions, stimulated urination, and constricted pupils.

Describe the shortcut for remembering the parasympathetic division's effects

REST + DIGEST.

cholinergic neurons functions

releases acetylcholine (ACh) and includes all preganglionic sympathetic neurons, all preganglionic parasympathetic neurons, and all postganglionic parasympathetic neurons.

adrenergic neurons functions

release norepinephrine (NE) and are almost all postganglionic sympathetic neurons.

Explain the neurotransmitters released by cholinergic and adrenergic neurons

Cholinergic neurons release acetylcholine (ACh), while adrenergic neurons release norepinephrine (NE).

Describe the types of cholinergic receptors

Nicotinic receptors, which are located on postganglionic neuron cell bodies in autonomic ganglia and also found on skeletal muscle Muscarinic receptors, which are located on parasympathetic effectors and some sympathetic effectors like sweat glands.

Contrast the effects of nicotinic and muscarinic receptors

Nicotinic receptors have an excitatory effect, while muscarinic receptors can have either excitatory or inhibitory effects depending on the effector.

List the main types of adrenergic receptors and their subtypes

Alpha (α) receptors, which include α₁ and α₂, Beta (β) receptors, which include β₁ and β₂.

Explain the general effects of adrenergic receptors

effects can be excitatory or inhibitory, depending on the receptor type and target tissue.

Describe the effects of α₁ adrenergic receptors

α₁ receptors typically cause blood vessel constriction, pupil dilation, and increased sphincter tone.

Describe the effects of β₁ adrenergic receptors

β₁ receptors increase heart rate and force of contraction.

What are the effects of α₂ and β₂ adrenergic receptors

α₂ receptors generally decrease gastric and insulin secretion and have other inhibitory effects, while β₂ receptors cause airway dilation and some blood vessel dilation.

Identify major effectors of the autonomic nervous system (ANS)

Major effectors include the heart, blood vessels, smooth muscle, lungs, digestive organs, urinary bladder, eye, glands, adrenal gland, liver, skeletal muscle blood vessels, sex organs, and adipose tissue.

List the types of receptors found in the heart

β₁, β₂, and muscarinic receptors.

What types of receptors are found in the airways/lungs

β₂ and muscarinic receptors.

Describe the receptors present in the eye

α₁, β₂, and muscarinic receptors.

Identify the types of receptors in the digestive tract

α₁, α₂, β₂, and muscarinic receptors.

What types of receptors are found in blood vessels

α₁, α₂, and β₂ receptors.

Describe the receptors present in sweat glands

muscarinic receptors.

Describe the role of autonomic reflexes in maintaining homeostasis

automatically regulate the activity of visceral organs, glands, blood vessels, heart, digestive system, and urinary system, helping to keep the body's internal environment stable without requiring conscious thought.

Explain the process that occurs when blood pressure increases

carotid baroreceptors detect it, and information travels to the medulla oblongata, leading to increased parasympathetic activity, a decrease in heart rate, and ultimately a decrease in blood pressure.

How does the body respond when blood pressure decreases

baroreceptors detects the bp drop, the medulla integrates the information, sympathetic activity increases, heart rate increases, and blood pressure rises.

Define the main divisions of the autonomic nervous system (ANS)

Sympathetic (stress response), Parasympathetic (rest and digest), Enteric (digestive tract).

Explain the difference in origin between sympathetic and parasympathetic nervous systems

SNS: originates from T1 to L2, PNS: originates from the brainstem and S2 to S4.

Describe the characteristics of preganglionic and postganglionic fibers in the sympathetic nervous system

preganglionic fibers are short, and postganglionic fibers are long.

What is the main neurotransmitter used by postganglionic fibers in the sympathetic nervous system

norepinephrine (NE).

Explain the effects of the sympathetic nervous system on airways and pupils

dilates airways and dilates pupils.

Describe the impact of the parasympathetic nervous system on digestion and urination

increases digestion and increases urination.

What is the overall control center of the autonomic nervous system

The hypothalamus.

Identify the key autonomic reflex centers located in the body

The brainstem and spinal cord.

Explain the significance of having different receptor types in the same organ

allows sympathetic and parasympathetic stimulation to produce different effects.

Define the primary function for the sympathetic nervous system

preparing the body to respond to stress.

What is the primary function for the parasympathetic nervous system

conserving energy and promoting digestion.