BIOL 251-FINAL EXAM
ACTUAL QUESTIONS AND
CORRECT ANSWERS
LATEST STUDY GUIDE
2025/2026 BEST FOR
REVISION .
, 11/10/2025
Chapter 14: The Autonomic Nervous System
Branches of the Peripheral Nervous System
◆ 1) The Somatic Nervous System (SNS): system responsible for voluntary
muscle movements and reflex arcs that involves skeletal muscle tissue
● A branch of the PNS
○ Mostly voluntary
◆ 2) The Autonomic Nervous System (ANS)
● A branch of the PNS = an efferent branch
○ Almost all effectors are visceral →involuntary
● General function: helps maintain a stable internal environment
○ Ex: regulation of heart rate, blood vessel diameter, pupil size,
body temperature, increases/decreases stomach secretions
The ANS vs The SNS
◆ Two systems have 3 distinct differences:
● 1) Effector organs
○ SNS →innervate skeletal muscle tissue
○ ANS →innervate visceral organs, cardiac muscle, smooth muscle
& glands
● 2) Efferent pathways and ganglia
○ SNS →single neuron extends from CNS to effector
◆ Motor neuron cell bodies in CNS, axons in PNS extend
to skeletal muscle
◆ Thick and heavily myelinated fibers
○ ANS →consists of two-neuron chain to reach effector; thinner
and less myelinated fibers
Preganglionic neuron: cell body in CNS, preganglionic
axon synapses with second motor neuron (postganglionic
neuron)
● Thin, lightly myelinated fibers
Postganglionic neuron: cell body is outside the CNS,
postganglionic axon extends to effector organ
● Thin, unmyelinated fibers
○ **Ganglia in the ANS are sites of synapse between the
preganglionic neuron and the postganglionic neuron
◆ Entirely motor ganglia
◆ No involvement with the dorsal root ganglia (entirely
sensory in nature)
, ● 3) Neurotransmitter effects
○ SNS →all release acetylcholine (ACl) at synapses
◆ Effect is excitatory on the muscle tissue
● Cause a depolarizing event to occur
○ ANS →release norepinephrine or acetylcholine
◆ Effect can be excitatory or inhibitory
● Can be depolarizing and hyperpolarizing
◆ Will largely depend on the effector organ and what
receptor types binds to the neurotransmitter
➔ Two Divisions of the ANS: The Parasympathetic Division
◆ “Rest and Digest” →keeps body energy use as low as possible when we are
relaxed
◆ Function: directs “housekeeping” activities →digestion, elimination of waste,
low blood pressure & heart rate, pupils constricted
◆ Origin of Fibers: the brain and the sacral spinal cord
● Preganglionic fibers are long, postganglionic fibers are short
○ If fiber is long = ganglia will be closer to the effector organ than to
the spinal cord
◆ Location of Ganglia: in or near the effector organ
Cranial Portion of Parasympathetic Division
● Function: supplies parasympathetic fibers to head, neck, thoracic &
abdominal regions
● Preganglionic fibers run in oculomotor, facial, glossopharyngeal, and
vagus (extends down to the body cavities) cranial nerves
○ Oculomotor nerve: innervates smooth muscle in eyes & muscle
associated with lens
◆ Effects?
○ Facial nerve: stimulates large glands of head (salivary
glands, nasal glands, lacrimal glands)
○ Glossopharyngeal nerve: activates parotid salivary gland
○ Vagus nerve: provide fibers to neck and almost every organ in
thoracic & abdominal cavities
◆ Makes up 90% of innervation
◆ Cardiac plexus: supplies fibers to heart
● When stimulated = slow heart rate
◆ Pulmonary plexus: supplies fibers to lung
● Maintain slow respiratory rate per minute when
activated
, ◆ Esophageal plexus: serves esophagus
● Fibers extend into abdominal cavity from
esophageal plexus →innervates liver, gallbladder,
stomach, small intestine, pancreas, proximal half of
large intestine
Sacral Portion of Parasympathetic Division
● Form pelvic splanchnic nerves
● Function: serves pelvic organs and distal portion half of large intestine
➔ Two Divisions of the ANS: The Sympathetic Division
◆ “Fight or flight”: activated when we are excited/scared/embarrassed
◆ Function: mobilizes the body →constriction of visceral blood vessels, dilates
bronchioles of lungs, increases glucose release to blood, pupils dilate, etc
◆ Origin of Fibers: thoracolumbar region of spinal (T1-L2)
● Preganglionic fibers are short, postganglionic fibers are long
● Cell bodies of this division form lateral horns of spinal cord
◆ Location of Ganglia: close to the spinal cord
◆ Sympathetic division is more complex than parasympathetic
● Innervates smooth muscle, cardiac muscle, and glands in body cavities
● Also innervates smooth muscle and glands in superficial regions
○ Sweat glands, arrector pili, smooth muscle in blood vessel walls
● Anatomy: sympathetic division forms the sympathetic trunk -
extends from the neck to the pelvis but the ganglia are only found
in the thoracic lumbar region of the spinal cord
○ Preganglionic fibers leave spinal cord via the ventral root
○ Fibers then pass through white ramus communicans (structure
that connects the spinal nerves to the sympathetic trunk), enter
sympathetic trunk ganglion
◆ White rami communicans: carry preganglionic fibers to
sympathetic trunk
○ Sympathetic trunk found on both sides of spinal cord
◆ At trunk ganglion, preganglionic and postganglionic fibers can form synapses 1 of
3 ways:
● 1) Preganglionic neuron and postganglionic neuron synapse at same
level
○ Synapse is found in the trunk ganglion at the same level as where
the preganglionic fiber exits the spinal cord
● 2) Preganglionic neuron and postganglionic neuron synapse at higher
or
lower level
ACTUAL QUESTIONS AND
CORRECT ANSWERS
LATEST STUDY GUIDE
2025/2026 BEST FOR
REVISION .
, 11/10/2025
Chapter 14: The Autonomic Nervous System
Branches of the Peripheral Nervous System
◆ 1) The Somatic Nervous System (SNS): system responsible for voluntary
muscle movements and reflex arcs that involves skeletal muscle tissue
● A branch of the PNS
○ Mostly voluntary
◆ 2) The Autonomic Nervous System (ANS)
● A branch of the PNS = an efferent branch
○ Almost all effectors are visceral →involuntary
● General function: helps maintain a stable internal environment
○ Ex: regulation of heart rate, blood vessel diameter, pupil size,
body temperature, increases/decreases stomach secretions
The ANS vs The SNS
◆ Two systems have 3 distinct differences:
● 1) Effector organs
○ SNS →innervate skeletal muscle tissue
○ ANS →innervate visceral organs, cardiac muscle, smooth muscle
& glands
● 2) Efferent pathways and ganglia
○ SNS →single neuron extends from CNS to effector
◆ Motor neuron cell bodies in CNS, axons in PNS extend
to skeletal muscle
◆ Thick and heavily myelinated fibers
○ ANS →consists of two-neuron chain to reach effector; thinner
and less myelinated fibers
Preganglionic neuron: cell body in CNS, preganglionic
axon synapses with second motor neuron (postganglionic
neuron)
● Thin, lightly myelinated fibers
Postganglionic neuron: cell body is outside the CNS,
postganglionic axon extends to effector organ
● Thin, unmyelinated fibers
○ **Ganglia in the ANS are sites of synapse between the
preganglionic neuron and the postganglionic neuron
◆ Entirely motor ganglia
◆ No involvement with the dorsal root ganglia (entirely
sensory in nature)
, ● 3) Neurotransmitter effects
○ SNS →all release acetylcholine (ACl) at synapses
◆ Effect is excitatory on the muscle tissue
● Cause a depolarizing event to occur
○ ANS →release norepinephrine or acetylcholine
◆ Effect can be excitatory or inhibitory
● Can be depolarizing and hyperpolarizing
◆ Will largely depend on the effector organ and what
receptor types binds to the neurotransmitter
➔ Two Divisions of the ANS: The Parasympathetic Division
◆ “Rest and Digest” →keeps body energy use as low as possible when we are
relaxed
◆ Function: directs “housekeeping” activities →digestion, elimination of waste,
low blood pressure & heart rate, pupils constricted
◆ Origin of Fibers: the brain and the sacral spinal cord
● Preganglionic fibers are long, postganglionic fibers are short
○ If fiber is long = ganglia will be closer to the effector organ than to
the spinal cord
◆ Location of Ganglia: in or near the effector organ
Cranial Portion of Parasympathetic Division
● Function: supplies parasympathetic fibers to head, neck, thoracic &
abdominal regions
● Preganglionic fibers run in oculomotor, facial, glossopharyngeal, and
vagus (extends down to the body cavities) cranial nerves
○ Oculomotor nerve: innervates smooth muscle in eyes & muscle
associated with lens
◆ Effects?
○ Facial nerve: stimulates large glands of head (salivary
glands, nasal glands, lacrimal glands)
○ Glossopharyngeal nerve: activates parotid salivary gland
○ Vagus nerve: provide fibers to neck and almost every organ in
thoracic & abdominal cavities
◆ Makes up 90% of innervation
◆ Cardiac plexus: supplies fibers to heart
● When stimulated = slow heart rate
◆ Pulmonary plexus: supplies fibers to lung
● Maintain slow respiratory rate per minute when
activated
, ◆ Esophageal plexus: serves esophagus
● Fibers extend into abdominal cavity from
esophageal plexus →innervates liver, gallbladder,
stomach, small intestine, pancreas, proximal half of
large intestine
Sacral Portion of Parasympathetic Division
● Form pelvic splanchnic nerves
● Function: serves pelvic organs and distal portion half of large intestine
➔ Two Divisions of the ANS: The Sympathetic Division
◆ “Fight or flight”: activated when we are excited/scared/embarrassed
◆ Function: mobilizes the body →constriction of visceral blood vessels, dilates
bronchioles of lungs, increases glucose release to blood, pupils dilate, etc
◆ Origin of Fibers: thoracolumbar region of spinal (T1-L2)
● Preganglionic fibers are short, postganglionic fibers are long
● Cell bodies of this division form lateral horns of spinal cord
◆ Location of Ganglia: close to the spinal cord
◆ Sympathetic division is more complex than parasympathetic
● Innervates smooth muscle, cardiac muscle, and glands in body cavities
● Also innervates smooth muscle and glands in superficial regions
○ Sweat glands, arrector pili, smooth muscle in blood vessel walls
● Anatomy: sympathetic division forms the sympathetic trunk -
extends from the neck to the pelvis but the ganglia are only found
in the thoracic lumbar region of the spinal cord
○ Preganglionic fibers leave spinal cord via the ventral root
○ Fibers then pass through white ramus communicans (structure
that connects the spinal nerves to the sympathetic trunk), enter
sympathetic trunk ganglion
◆ White rami communicans: carry preganglionic fibers to
sympathetic trunk
○ Sympathetic trunk found on both sides of spinal cord
◆ At trunk ganglion, preganglionic and postganglionic fibers can form synapses 1 of
3 ways:
● 1) Preganglionic neuron and postganglionic neuron synapse at same
level
○ Synapse is found in the trunk ganglion at the same level as where
the preganglionic fiber exits the spinal cord
● 2) Preganglionic neuron and postganglionic neuron synapse at higher
or
lower level
