Nervous System Cranial and Sacral Outflow

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Questions and Answers

What is the primary function of the Vagus nerve (X) in the autonomic nervous system?

Constricts the pupils and causes tearing

Stimulates digestive glands and decreases heart rate (correct)

Stimulates muscle contraction in the limbs

Increases heart rate and blood pressure

Which autonomic plexus is responsible for supplying the kidneys and ureters?

Renal plexus (correct)

Celiac plexus

Hypogastric plexus

Superior mesenteric plexus

Which cranial nerve is associated with tear, nasal mucus, and saliva production?

Facial (VII) (correct)

Vagus (X)

Glossopharyngeal (IX)

Oculomotor (III)

Which of the following is primarily a function of the sympathetic nervous system?

Increasing heart rate and respiratory rate Signup and view all the answers

What is a main role of the amygdala in the autonomic nervous system?

Stimulating sympathetic activity during fear responses Signup and view all the answers

Where are the preganglionic neurons of the parasympathetic nervous system located?

Cranial nerve nuclei in the brainstem and sacral spinal cord Signup and view all the answers

Which of the following is NOT a function of the sacral outflow (S2-4)?

Stimulating digestive processes Signup and view all the answers

What is the function of the adrenal medulla in response to sympathetic stimulation?

Secrete norepinephrine and epinephrine directly into the bloodstream Signup and view all the answers

The sympathetic nervous system typically causes which of the following responses?

Dilation of the pupils Signup and view all the answers

What is the primary function of the autonomic nervous system?

To regulate involuntary functions of the body Signup and view all the answers

Which of the following statements about postganglionic neurons in the parasympathetic system is correct?

They are short and non-myelinated. Signup and view all the answers

The hypothalamus serves as which of the following in the autonomic nervous system?

Main integration center for autonomic functions Signup and view all the answers

In the autonomic nervous system, where is the cell body of the preganglionic neuron located?

In the central nervous system Signup and view all the answers

Which physiological response is typically associated with the sympathetic nervous system?

Pupil dilation Signup and view all the answers

Which system is primarily responsible for the body’s rest and digest functions?

Parasympathetic nervous system Signup and view all the answers

Which neurotransmitter is primarily associated with the effects of the sympathetic nervous system?

Norepinephrine Signup and view all the answers

What type of muscles does the autonomic nervous system primarily control?

Cardiac muscles and smooth muscles Signup and view all the answers

How is control exerted by the motor neurons in the autonomic nervous system?

Involuntary and either excitatory or inhibitory Signup and view all the answers

Which pathway correctly describes the autonomic nerve pathway?

Two motor neurons connected by an autonomic ganglion Signup and view all the answers

Which of the following is NOT true regarding the somatic nervous system?

It connects with smooth muscles Signup and view all the answers

What is the main distinction between the neurotransmitters used in the somatic and autonomic nervous systems?

The somatic system uses acetylcholine only while the autonomic can use either acetylcholine or norepinephrine Signup and view all the answers

Study Notes

Cranial Outflow

Oculomotor (III): Controls pupil constriction.
Facial (VII): Responsible for tear production, nasal mucus, and saliva secretion.
Glossopharyngeal (IX): Stimulates the parotid salivary gland.
Vagus (X): Plays a crucial role in regulating visceral organs within the thorax and abdomen by:
- Stimulating digestive glands.
- Increasing smooth muscle motility in the digestive tract.
- Reducing heart rate.
- Causing bronchial constriction.

Sacral Outflow

S2-S4: Forms pelvic splanchnic nerves that innervate the following:
- The latter half of the large intestine.
- The bladder, contracting it and relaxing the sphincter, contributing to urination.
- All pelvic (genitourinary) organs, leading to erection.

Autonomic Plexuses

A network of sympathetic and parasympathetic axons:
- Cardiac Plexus: Innervates the heart.
- Pulmonary Plexus: Supplies the bronchial tree.
- Celiac Plexus (Largest): Innervates the stomach, spleen, pancreas, liver, gallbladder, and adrenal medulla.
- Superior Mesenteric Plexus: Supplies the small intestine and proximal colon.
- Inferior Mesenteric Plexus: Innervates the distal colon and rectum.
- Hypogastric Plexus: Controls the urinary bladder and genital organs.
- Renal Plexus: Innervates the kidneys and ureters.

Central Control of the Autonomic Nervous System

Amygdala: The primary limbic region involved in emotional processing.
- Stimulates sympathetic activity, particularly in response to learned fear-related behaviors.
- Can be voluntarily activated when recalling frightening experiences.
- Some individuals can regulate specific autonomic activities by gaining extraordinary control over their emotions.
Hypothalamus: The main integration center for autonomic function.
Reticular Formation: Exerts the most direct influence over autonomic function.

Structural Differences Between Sympathetic and Parasympathetic Systems:

Sympathetic System:
- Preganglionic neurons: Short and myelinated.
- Postganglionic neurons: Long and unmyelinated.
- Neurotransmitters: Acetylcholine (preganglionic) and norepinephrine (postganglionic).
Parasympathetic System:
- Preganglionic neurons: Long and myelinated.
- Postganglionic neurons: Short and unmyelinated.
- Neurotransmitters: Acetylcholine (both preganglionic and postganglionic).

Autonomic Nerve Pathway

Consists of two nerve cells (neurons):
- Preganglionic neuron: Cell body located in the brain stem or spinal cord.
- Postganglionic neuron: Cell body located in an autonomic ganglion.

Characteristics of the Somatic and Autonomic Nervous Systems

Somatic Nervous System:
- Sensory Neurons (Afferent Pathway): Carry somatic and special senses.
- Effector: Skeletal muscle.
- Control: Voluntary and excitatory.
- Motor Neuron (Efferent Pathway): One motor axon from the CNS to the effector, using acetylcholine as the neurotransmitter.
Autonomic Nervous System:
- Sensory Neurons (Afferent Pathway): Primarily located in blood vessels and visceral organs.
- Effector: Smooth muscle, cardiac muscle, and glands.
- Control: Involuntary, with both excitatory and inhibitory effects.
- Motor Neuron (Efferent Pathway): Two motor axons:
  - Preganglionic Nerve: From the CNS to the autonomic ganglion.
  - Postganglionic Nerve: From the autonomic ganglion to the effector.
  - Neurotransmitters: Acetylcholine (preganglionic) and either acetylcholine or norepinephrine (postganglionic).

Adrenal Medulla

Acts as modified postganglionic neurons that release epinephrine/norepinephrine directly into the bloodstream.
This produces a widespread sympathetic response (often referred to as the "adrenaline surge" during emergencies).

Sympathetic Nervous System (Continued)

Postsynaptic sympathetic fibers, traveling via spinal nerves and periarterial plexuses, reach virtually all body parts, including sweat glands, arrector pili muscles, and viscera. They do not innervate avascular tissues, such as nails and cartilage.

Example Sympathetic Effects:

Sweating when nervous.
Hair standing on end when afraid.
Increased blood pressure (vasoconstriction) during excitement.
Dry mouth.
Dilated pupils.
Elevated heart and respiratory rates, supplying O2 to skeletal muscles.
Release of glucose by the liver.

Parasympathetic Nervous System (Craniosacral System)

Location of Preganglionic Neurons:
- Cranial Site: Cranial nerve nuclei in the brainstem, exiting the CNS via cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus).
- Sacral Site: Gray matter of the spinal cord (S2-S4), exiting through anterior roots of spinal nerves to form pelvic splanchnic nerves.

Parasympathetic System (Continued)

Location of Postganglionic Neurons:
- Cranial Site: Four parasympathetic ganglia (ciliary, pterygopalatine, submandibular, and otic).
- Other Body Regions: Individually located in or on the walls of target organs.
Fiber Characteristics: Preganglionic fibers are long and myelinated, while postganglionic fibers are short and non-myelinated.

Parasympathetic System Distribution and Function

Exhibit a localized distribution, in contrast to the widespread sympathetic system.

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Description

Explore the vital functions of cranial and sacral outflows in the autonomic nervous system. This quiz covers the roles of specific cranial nerves and sacral nerves in regulating various bodily functions, including heart rate, gland stimulation, and pelvic organ innervation. Test your knowledge on these essential components of the nervous system.