nervous (PNS) Flashcards
Peripheral Nervous System contains:
- Cranial Nerves
- Spinal Nerves
- Autonomic Nervous system
There are 12 pairs of _____________, arranged symmetrically and attached to the brain, with the following origins:
- Midbrain
- Pons
- Medulla Oblongata
Cranial Nerves
III (Oculomotor), IV (Trochlear)
Midbrain
V (Trigeminal), VI (Abducens), VII (Facial), VIII
(Vestibulocochlear)
Pons
IX (Glossopharyngeal), X (Vagus), XI (Accessory), XII (Hypoglossal)
Medulla Oblongata
Each nerve may be classified as?
sensory (S)
motor (M)
mixed (Mx)
parasympathetic (PS).
Types of Cranial Nerves
Olfactory (I)
Optic (II)
Oculomotor (III)
Trochlear (IV)
Trigeminal (V)
Abducens (VI)
Facial (VII)
Vestibulocochlear (VIII)
Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)
➢ Smell; passes through the cribriform plate to the olfactory bulb.
➢ Disorder: Anosmia (loss of smell).
Olfactory (I) - (S):
➢ Vision; crosses at the optic chiasm.
➢ Disorder: Anopsia (blindness).
Optic (II) - (S):
➢ Controls most eye movements, except for the lateral rectus and superior oblique muscles.
➢ Parasympathetic to the iris.
Oculomotor (III) - (M, PS):
➢ Thinnest nerve, innervates the superior oblique muscle.
Trochlear (IV) - (M):
➢ Three branches (ophthalmic, maxillary, mandibular); sensory to face, motor to mastication muscles.
➢ Sensory (anterior 2/3 of the tongue) and motor functions.
Trigeminal (V) - (Mx):
➢ Controls the lateral rectus muscle (LR6) for eye movement.
Abducens (VI) – (M):
➢ Taste (anterior 2/3 of tongue), facial expression muscles, parasympathetic to lacrimal and salivary glands (except parotid).
Facial (VII) - (Mx, PS):
➢ Hearing and balance.
Vestibulocochlear (VIII) - (S):
➢ Taste (posterior 1/3 of tongue), motor to pharynx muscles, parasympathetic to the parotid gland.
Glossopharyngeal (IX) - (Mx, PS):
➢ Longest nerve; sensory to internal organs, motor to laryngeal and pharyngeal muscles, parasympathetic to smooth muscles in organs.
Vagus (X) - (Mx, PS):
➢ Innervates the sternocleidomastoid and trapezius muscles.
Accessory (XI) - (M):
➢ Controls tongue muscles, excluding the palatoglossus.
Hypoglossal (XII) - (M):
Classification of Cranial Nerves
- Sensory Nerves (Afferent): I, II, VIII
- Motor Nerves (Efferent): III, IV, VI, XI, XII
- Mixed Nerves (Sensory & Motor): V, VII, IX, X
- The spinal cord gives rise to 31 pairs of spinal nerves that emerge from the vertebral canal through intervertebral foramina. These mixed nerves (sensory and motor) are formed by the union of:
o Dorsal Root:
o Ventral Root:
Spinal Nerves
Contains sensory neuron fibers.
Dorsal Root:
Contains motor neuron fibers.
Ventral Root
Spinal Nerve Distribution:
cervical pairs = ?
thoracic pairs =?
lumbar pairs = ?
sacral pairs = ?
coccygeal pair =?
- 8
- 12
- 5
- 5
- 1
____________ are networks of nerve fibers from the ventral rami of certain spinal nerves (cervical, lumbar, and sacral). The posterior rami do not form ____________.
Plexuses
- Supplies the back and sides of the head and front of the neck.
- Includes the phrenic nerve, which innervates the diaphragm.
Cervical Plexus (C1-C4):
➢ Supplies the skin and muscles of the upper limbs.
➢ Major nerves: circumflex, radial, median, ulnar and musculocutaneous.
Brachial Plexus (C5-T1):
From L2-L4, supplies medial thigh muscles and
skin.
Obturator Nerve:
➢ Divides into anterior (obturator nerve) and posterior (femoral nerve) divisions.
Lumbar Plexus (L1-L4):
From L2-L4, supplies anterior thigh muscles and skin.
Femoral Nerve:
➢ Supplies the posterior lower extremities.
➢ Includes the sciatic nerve (largest nerve), which divides into:
o Tibial Nerve
o Common Peroneal Nerve
Sacral Plexus (L4-S3):
- Do not form plexuses; function independently.
- T1-T11:
- T12:
Thoracic Spinal Nerves
Forms the subcostal nerve.
T12
Form the intercostal nerves.
T1-T11
The ANS controls involuntary bodily functions and has two main divisions:
o Sympathetic Division (Thoracolumbar):
o Parasympathetic Division (Craniosacral):
Autonomic Nervous System (ANS)
➢ Originates from the thoracic and first three lumbar segments of the spinal cord.
➢ Activates the “fight or flight” response during stressful or dangerous situations, increasing heart rate, blood flow to muscles, and pupil dilation.
Sympathetic Division (Thoracolumbar):
➢ Originates from the third, seventh, ninth, and tenth cranial nerves, and the second to fourth sacral spinal segments.
➢ Controls “rest and digest” functions, promoting relaxation, digestion, slower heart rate, and regulated breathing for recovery and repair.
Parasympathetic Division (Craniosacral):
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