M06 test 03

Peripheral Nervous System

All neural structures outside brain/spinal cord: sensory receptors, peripheral nerves, ganglia, efferent motor endings

Endoneurium

Connective tissue layer around each axon

Perineurium

Connective tissue layer around fascicles

Epineurium

Connective tissue layer around entire nerve

Endo

Prefix meaning inside

Peri

Prefix meaning around

Epi

Prefix meaning upon/outside

Mechanoreceptors

Receptors classified by stimulus type that respond to mechanical pressure or distortion

Thermoreceptors

Receptors classified by stimulus type that respond to temperature changes

Photoreceptors

Receptors classified by stimulus type that respond to light

Chemoreceptors

Receptors classified by stimulus type that respond to chemical stimuli

Nociceptors

Receptors classified by stimulus type that respond to pain

Exteroceptors

Receptors classified by location that respond to external stimuli

Interoceptors

Receptors classified by location (visceroceptors) that respond to internal stimuli

Proprioceptors

Receptors classified by location that provide information about body position

Nonencapsulated receptors

Receptors classified by structure that include free nerve endings

Encapsulated receptors

Receptors classified by structure that include Meissner's, Pacinian, Ruffini, muscle spindle, tendon organ

Somatic afferent nerves

Type of mixed nerve that carries sensory input from the body wall

Somatic efferent nerves

Type of mixed nerve that carries motor output to skeletal muscles

Visceral afferent nerves

Type of mixed nerve that carries sensory input from internal organs

Visceral efferent nerves

Type of mixed nerve that carries motor output to internal organs

Afferent

Carries sensory input toward the CNS

Efferent

Carries motor output away from the CNS

Phasic receptors

Adapt quickly and signal stimulus changes

Tonic receptors

Adapt slowly and maintain response

Aδ fibers

Fibers that carry sharp, fast pain sensations

C fibers

Fibers that carry slow, burning pain sensations

Referred pain

Occurs when visceral and somatic afferents share tracts, leading to misinterpretation of pain origin

Schwann cells

Cells that form regeneration tubes guiding regrowth of neurons in the PNS if soma is intact

Oligodendrocytes

Cells in the CNS that inhibit regeneration of neurons

Cranial Nerve I (Olfactory)

Function: Smell (sensory only)

Olfactory receptors

Located in the nasal mucosa of the upper nasal cavity

Olfaction perception

Perceived in the olfactory cortex of the temporal lobe

Cranial Nerve II (Optic)

Function: Vision (sensory only)

Optic receptors

Located in the retina of the eye

Optic chiasm

Area where optic nerves partially cross before continuing to the occipital cortex

Cranial Nerve III (Oculomotor)

Function: Moves most eye muscles, constricts pupil, raises eyelid (motor)

Cranial Nerve IV (Trochlear)

Function: Moves the superior oblique muscle (motor)

Cranial Nerve V (Trigeminal)

Function: Facial sensation and chewing (both sensory and motor)

Branches of the Trigeminal nerve

Ophthalmic (V1), Maxillary (V2), Mandibular (V3)

Cranial Nerve VI (Abducens) function

Lateral eye movement via lateral rectus muscle (motor)

How is CN VI tested?

Move eyes laterally

Cranial Nerve VII (Facial) function

Facial expression, taste (anterior 2/3 tongue), tears, saliva (both)

How is CN VII tested?

Smile, close eyes, show teeth

What disorder is associated with the Facial nerve?

Bell's palsy

Cranial Nerve VIII (Vestibulocochlear) function

Hearing and balance (sensory)

Vestibular part refers to

Balance

Cochlear part refers to

Hearing

How is CN VIII tested?

Tuning fork or balance tests

Cranial Nerve IX (Glossopharyngeal) function

Taste (posterior 1/3 tongue), swallowing, salivation (both)

What does "glosso" refer to?

Tongue

What does "pharyngeal" refer to?

Throat

How is CN IX tested?

Gag reflex, taste on posterior tongue

Cranial Nerve X (Vagus) function

Parasympathetic control of heart, lungs, digestion (both)

What is unusual about the Vagus nerve?

Extends beyond head and neck to thorax and abdomen

How is CN X tested?

Gag reflex, voice quality

Cranial Nerve XI (Accessory) function

Moves sternocleidomastoid and trapezius (motor)

What is unusual about the Accessory nerve?

Originates partly from spinal cord roots

How is CN XI tested?

Shrug shoulders, turn head

Cranial Nerve XII (Hypoglossal) function

Tongue movement (motor)

How is CN XII tested?

Stick out tongue; deviation indicates lesion

What is the function of the ventral root?

Carries motor (efferent) fibers

What is the function of the dorsal root?

Carries sensory (afferent) fibers

What are dorsal root ganglia?

Contain sensory neuron cell bodies

What is a spinal nerve?

Mixed nerve formed by dorsal and ventral roots

What is the dorsal ramus?

Serves posterior trunk muscles and skin

What is the ventral ramus?

Serves anterior trunk and limbs; forms plexuses

What are rami communicantes?

Connect spinal nerves to sympathetic trunk ganglia

What is a plexus?

Interlacing network of spinal nerve rami

Which major nerve arises from the cervical plexus?

Phrenic nerve (C3-C5) to the diaphragm

Which major nerves arise from the brachial plexus?

Axillary, Musculocutaneous, Median, Ulnar, Radial

Which major nerves arise from the lumbar plexus?

Femoral and Obturator nerves

Which major nerves arise from the sacral plexus?

Sciatic, Tibial, and Common fibular nerves

What are the five components of a reflex arc?

Receptor, Sensory neuron, Integration center, Motor neuron, Effector

What is the function of the muscle spindle?

Detects muscle stretch; initiates contraction to resist stretch

What is the function of the Golgi tendon organ?

Detects tension; inhibits muscle to prevent damage

What are the steps of the patellar reflex?

Tap tendon → stretch quadriceps → activate spindle → sensory neuron → motor neuron → quadriceps contract → leg kicks

What are the steps of the withdrawal reflex?

Pain stimulus → sensory neuron → interneuron → activate flexors, inhibit extensors → withdraw limb

How does a stretch reflex differ from a withdrawal reflex?

Stretch is monosynaptic and maintains posture; withdrawal is polysynaptic and protective

What are the superficial reflexes?

Plantar (Babinski), Abdominal, Cremasteric

Effectors of the autonomic nervous system

Smooth muscle, cardiac muscle, and glands

Comparison of autonomic and somatic nervous systems

The ANS controls involuntary effectors (smooth/cardiac muscle, glands), while the somatic NS controls voluntary skeletal muscles.

Location difference between somatic and autonomic nervous systems

Somatic motor neurons originate in the CNS and project directly to skeletal muscles; autonomic neurons involve a two-neuron chain (preganglionic in CNS, postganglionic in PNS ganglia).

Ganglia difference between somatic and autonomic nervous systems

Somatic NS has no ganglia; ANS uses autonomic ganglia to connect preganglionic and postganglionic neurons.

Effector difference between somatic and autonomic nervous systems

Somatic effectors are skeletal muscles; autonomic effectors are cardiac muscle, smooth muscle, and glands.

Functional difference between somatic and autonomic nervous systems

Somatic controls voluntary movement; autonomic controls involuntary functions such as heart rate, digestion, and respiration.

Origin of the sympathetic nervous system

Thoracolumbar region of the spinal cord (T1-L2).

Origin of the parasympathetic nervous system

Craniosacral region (brainstem and sacral spinal cord S2-S4).

Location of ganglia in the sympathetic nervous system

Close to the spinal cord (in paravertebral or prevertebral ganglia).

Location of ganglia in the parasympathetic nervous system

Near or within target organs (terminal ganglia).

Fiber types of the sympathetic nervous system

Short preganglionic fibers and long postganglionic fibers.

Fiber types of the parasympathetic nervous system

Long preganglionic fibers and short postganglionic fibers.

Neurotransmitters used in the sympathetic nervous system

Preganglionic: acetylcholine (ACh); Postganglionic: norepinephrine (NE), sometimes ACh (for sweat glands).

Neurotransmitters used in the parasympathetic nervous system

Both preganglionic and postganglionic fibers release acetylcholine (ACh).

Functions of the sympathetic nervous system

"Fight or flight" — increases heart rate, dilates pupils, dilates bronchioles, inhibits digestion, stimulates glucose release.

Functions of the parasympathetic nervous system

"Rest and digest" — decreases heart rate, constricts pupils, stimulates digestion, promotes energy storage.

Oculomotor (III)

A cranial nerve responsible for eye movement.

Facial (VII)

A cranial nerve involved in facial expressions and taste.

Glossopharyngeal (IX)

A cranial nerve that contributes to taste and swallowing.

Vagus (X)

A cranial nerve that controls functions of the heart, lungs, and digestive tract.