Exam 4, Chapter 13a - Somatic Motor (Part 1) Flashcards
All neural structures outside the brain and spinal cord
Peripheral Nervous System
Includes sensory receptors, peripheral nerves, associated ganglia, and motor endings
Peripheral Nervous System
Provides links to and from the external environment
Peripheral Nervous System
- cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
- Connective tissue coverings include???
Structure of a Nerve
-loose connective tissue that surrounds each individual axons
Structure of a Nerve
Endoneurium
-coarse connective tissue that bundles fibers into fascicles (a bunch of axons)
Structure of a Nerve
Perineurium
-tough fibrous sheath around an entire nerve (bunch of bunches of axons)
Structure of a Nerve
Epineurium
Classification of Nerves
-carry impulse to the CNS
Classification of Nerves
sensory (afferent)
Classification of Nerves
-carry impulses from CNS
Classification of Nerves
Motor (efferent)
Classification of Nerves
-sensory & motor fibers carry impulses to & from CNS; most common type of nerve
Classification of Nerves
Mixed
Classification of Nerves
- are mixed nerves
- carry somatic and autonomic (visceral) impulses
Classification of Nerves
Peripheral Nerves
Classification of Nerves
- Somatic afferent
- Somatic efferent
- Visceral afferent
- Visceral efferent
Classification of Nerves
Peripheral Nerves
Four types of mixed nerves
-nerves originate from the brain (cranial nerves) or spinal column (spinal nerves)
Peripheral nerves
-Collections of neuron cell bodies with similar function associated with nerves in the PNS
Ganglion
plural=ganglia
-Ganglia associated with afferent nerve fibers contain cell bodies of sensory neurons
Ganglion
plural=ganglia
- lead into the spinal cord
Ganglion
(plural=ganglia)
Dorsal root ganglia
- are associated with efferent nerve fiber;
- these are cell bodies of autonomic motor neurons involved with visceral innervation (names & details later in unit)
Ganglion
(plural=ganglia)
Autonomic ganglia
- Damage to the neuron cell body is serious because mature neurons are amitotic.
- However, if the __ of a damaged nerve remains intact, damage can be repaired.
Regeneration of Nerve Fibers
soma
-(occurs where an axon is damaged)
Regeneration of Nerve Fibers
Wallerian Degeneration
- Axon becomes fragmented at injury site
- Macrophages – remove debris
Regeneration of Nerve Fibers
Wallerian Degeneration
-follows degeneration and involves coordinated activity among:
Regeneration of Nerve Fibers
Regeneration
- form regeneration tube;
- secrete growth factors
Regeneration of Nerve Fibers
Schwann cells
-regenerate via filaments at a rate of 1.5 mm per day
Regeneration of Nerve Fibers
Axons
- New myelin sheath forms
Regeneration of Nerve Fibers
Scwann cells
-Twelve pairs of c____ arise from the brain
Cranial Nerves
Arises from the olfactory epithelium (pseudostratified ciliated columnar)
Cranial Nerves
I. Olfactory (S)
Passes through the cribriform plate of the ethmoid bone
Cranial Nerves
I. Olfactory (S)
Fibers run through the olfactory bulb and terminate in the primary olfactory cortex (located in the deep temporal lobe, in the uncus);
Cranial Nerves
I. Olfactory (S)
ipsilateral; do NOT synapse in the thalamus
Cranial Nerves
I. Olfactory (S)
In order to correlate a smell with a memory, however, axons will pass through the thalamus
Cranial Nerves
I. Olfactory (S)
Sensory: Functions solely by carrying afferent impulses for the sense of smell
Cranial Nerves
I. Olfactory (S)
- Arises from the retina of the eye
Cranial Nerves
II. Optic (S)
-Optic nerves pass through the optic canals (sphenoid bone) and converge at the optic chiasma (“X” cross-over) which sits just anterior to the pituitary gland
Cranial Nerves
II. Optic (S)
-They continue to the thalamus where they synapse
Cranial Nerves
II. Optic (S)
-From there, the optic radiation fibers run to the primary visual cortex (calcarine sulcus)
Cranial Nerves
II. Optic (S)
-Sensory: Functions solely by carrying afferent impulses for vision
Cranial Nerves
II. Optic (S)
-Somatic Motor: Fibers extend from the ventral midbrain (base of the cerebral peduncle), pass
through the superior orbital fissure (sphenoid), and go to the extrinsic eye muscles
Cranial Nerves
III. Oculomotor (M)
Functions in raising the eyelid, directing the eyeball (4 of 6 muscles controlling eye movement:
-superior, inferior & medial rectus plus inferior oblique)
Cranial Nerves
III. Oculomotor (M)
Autonomic Motor (Parasympathetic): cell bodies are in the ciliary ganglia - Functions in constricting the iris, and controlling lens shape for focusing
Cranial Nerves
III. Oculomotor (M)
-Fibers emerge from the dorsal midbrain (corpora quadrigemina) and enter the orbits via the superior orbital fissures;
Cranial Nerves
IV. Trochlear (M)
-innervate the superior oblique muscle (1 of 6 muscles controlling eye
movement)
Cranial Nerves
IV. Trochlear (M)
-Somatic Motor: Functions primarily as a motor nerve that directs the eyeball
Cranial Nerves
IV. Trochlear (M)
Largest cranial nerve; mixed nerve
Cranial Nerves
V. Trigeminal (B)
Three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3)
Cranial Nerves
V. Trigeminal (B)
Sensory: Afferent fibers run from the face, lips, gums, teeth & tongue [not taste buds] to the
pons via the superior orbital fissure (V1), the foramen rotundum (V2), and the foramen ovale (V3) [all in sphenoid]
Cranial Nerves
V. Trigeminal (B)
Cell bodies converge at the large trigeminal ganglion
Cranial Nerves
V. Trigeminal (B)
Somatic motor: Mandibular division (V3) supplies motor fibers for mastication (chewing)
Cranial Nerves
V. Trigeminal (B)
-Fibers leave the inferior pons and enter the orbit via the superior orbital fissure
Cranial Nerves
VI. Abducens (M)
- innervate the lateral rectus muscle (1 of 6 muscles controlling eye movement)
Cranial Nerves
VI. Abducens (M)
- Somatic Motor: Functions primarily as a motor nerve that directs the eyeball
Cranial Nerves
VI. Abducens (M)
Fibers leave the pons, travel through the internal acoustic meatus, and emerge through the stylomastoid foramen (in temporal bone) to the lateral aspect of the face
Cranial Nerves
VII. Facial (B)
Mixed nerve with five major branches: temporal, zygomatic, buccal, mandibular, cervical)
Cranial Nerves
VII. Facial (B)
Somatic motor: Functions as a motor nerve for muscles of facial expression
Cranial Nerves
VII. Facial (B)
Autonomic motor (Parasympathetic): Functions in transmittal of motor impulses to lacrimal, nasal and salivary glands
Cranial Nerves
VII. Facial (B)
Sensory: Afferent fibers from the taste buds in the anterior two-thirds of the tongue
Cranial Nerves
VII. Facial (B)
Sometimes referred to as Auditory Vestibular Nerve
Cranial Nerves
VIII. Vestibulocochloear (S)
Fibers arise from the hearing and equilibrium apparatus of the inner ear, pass through the
internal acoustic meatus, and enter the brainstem at the pons-medulla border
Cranial Nerves
VIII. Vestibulocochloear (S)
Two divisions – cochlear (hearing) and vestibular (balance)
Cranial Nerves
VIII. Vestibulocochlear (S)
Sensory: Primarily functions in hearing and balance
Cranial Nerves
VIII. Vestibulocochloear (S)
Fibers emerge from the medulla, leave the skull via the jugular foramen, and run to the throat
Cranial Nerves
IX. Glossopharyngeal (B)
Somatic Motor – Motor nerve for the posterior tongue and pharynx (lifts during swallowing)
Cranial Nerves
IX. Glossopharyngeal (B)
Autonomic Motor (Parasympathetic) - Provides motor fibers to the parotid salivary gland,
Cranial Nerves
IX. Glossopharyngeal (B)
Sensory – Afferent fibers conduct taste and general sensory impulses from the posterior tongue and pharynx (swallow & gag reflex),
carotid body chemoreceptors (monitors O2 & CO2,
ultimately affects
breathing rate/depth),
carotid sinus baroreceptors (monitors blood pressure)
Cranial Nerves
IX. Glossopharyngeal (B)
The only cranial nerve that extends beyond the head and neck
Cranial Nerves
X. Vagus (B)
Fibers emerge from the medulla via the jugular foramen & descends into the thorax and
abdomen
-mixed nerve that serves as a major parasympathetic pathway for the body
Cranial Nerves
X. Vagus (B)
Autonomic motor (Parasympathetic) - Provides motor fibers to the heart, lungs & visceral organs and functions in regulation of heart rate, breathing and digestive system activity
Cranial Nerves
X. Vagus (B)
Somatic motor – Functions as a motor nerve for pharynx & larynx skeletal muscle (swallowing)
Cranial Nerves
X. Vagus (B)
Sensory: Afferent fibers from the pharynx and taste buds of posterior tongue; afferent fibers from the thoracic and abdominal viscera; carotid & aortic body chemoreceptors (monitors O2 & CO2);
aortic arch baroreceptors (monitors blood pressure)
Cranial Nerves
X. Vagus (B)
-Formed from C1 – C5 ventral rootlets (no cranial origin); this root passes upward into the cranium via the foramen magnum and then leaves the cranium via the jugular foramen
Cranial Nerves
XI. Accessory (M)
Primarily a somatic motor nerve
Cranial Nerves
XI. Accessory (M)
Supplies fibers to the larynx, pharynx, and soft palate
Cranial Nerves
XI. Accessory (M)
Innervates the trapezius and sternocleidomastoid, which move the head and neck
Cranial Nerves
XI. Accessory (M)
Fibers arise from the medulla and exit the skull via the hypoglossal canal (occipital bone, just
lateral to the foramen magnum) to the tongue
Cranial Nerves
XII: Hypoglossal (M)
Somatic motor: Innervates both extrinsic and intrinsic muscles of the tongue, which contribute to swallowing and speech
Cranial Nerves
XII: Hypoglossal (M)
named according to their point of exit from the intervertebral foramen
Spinal Nerves
C1-C7 nerves are named as they exit SUPERIOR to the vertebrae for which they are named
Spinal Nerves
nerve exits below C7 vertebra (so, C8 nerve exits at the C7-T1 intervertebral foramen)
Spinal Nerves
C8
All others leave the intervertebral foramen ___ the named vertebra
Spinal Nerves
below
Thoracic?
Lumbar?
Sacral?
Coccygeal?
Spinal Nerves 12 thoracic (T1-T12); 5 Lumbar (L1-L5); 5 Sacral (S1-S5); 1 Coccygeal (C0)
Each spinal nerve connects to the spinal cord via a
Spinal Nerves
ventral and a dorsal root
Each root forms from a series of ___ that attach to the spinal cord
Spinal Nerves
rootlets
arise from the ventral horn and contain motor (efferent) fibers
Spinal Nerves
Ventral roots
Composed of somatic motor & autonomic motor
Spinal Nerves
Ventral roots
contain sensory afferent fibers that arise from sensory neurons in the dorsal root ganglia and conduct impulses from peripheral receptors
Spinal Nerves
Dorsal roots
Roots join together to form the ____ just distal to the dorsal root ganglion & just
before exiting from the vertebral column
Spinal Nerves
Each ___ is very short (only 1-2 cm)
Spinal Nerves
Nerve carries both
Spinal Nerves
Afferent and Efferent Fibers
The length of the spinal roots in the ___ and ___ region is significant, as they extend inferiorly as the cauda equina before joining together as a nerve
Spinal Nerves
Lumbar and Sacral
the spinal roots are ___ to the nerve & are either sensory or motor
Spinal Nerve
medial
Immediately upon exiting the intervertebral foramen, the short spinal nerves branch into three or four distal rami (all with mixed fibers);
Spinal Rami
Point: the mixed fiber spinal rami are ___ to the nerve
Spinal Rami
Lateral
Innervates the posterior trunk via several branches in a simple segmental pattern
Spinal Rami
Small Dorsal Ramus
T1-T12 innervate the thorax as intercostal nerves (simple segmental pattern)
Spinal Rami
Larger ventral ramus
Intercostal nerves supply muscles of the ribs, anterolateral thorax & abdominal wall
Spinal Rami
Larger ventral ramus
A portion of T1 and all other ventral rami form complex plexus networks (additional detail
below) which primarily innervate the limbs
Spinal Rami
Larger ventral ramus
Re-enters the vertebral canal to innervate the spinal cord meninges and blood vessels
Spinal Rami
Tiny Meningeal branch
are at the base of the ventral rami in the thoracic region
Spinal Rami
Rami communicantes
These branches form the sympathetic trunk ganglia and carry autonomic motor fibers
Spinal Rami
Rami communicantes
LOOK AT RAMI DIAGRAM
Spinal Rami
Ok.
All ventral rami (motor) except T2-T12 branch and form interlacing nerve networks called
Nerve Plexuses
located lateral to the vertebral column in the cervical, brachial, lumbar & sacral regions
Nerve Plexuses
Each resulting branch of a ___ contains fibers from several spinal nerves
Nerve Plexuses
Fibers travel to the periphery via
Nerve Plexuses
several different routes
Each muscle receives a nerve supply from
Nerve Plexuses
more than one spinal nerve
Damage to one spinal segment (can/not?) t completely paralyze a muscle
Nerve Plexuses
cannot
Innervation of a Joint
any nerve serving a muscle that produces movement at a joint also innervates the joint itself and the skin over the joint
Nerve Plexuses
Hilton’s law
Innervates
M/S fibers for diaphragm (respiration)
Cervical Plexus
Phrenic Nerve
Innervates
Sternocleidomastoir muscle & Trapezius
Cervical Plexus Accessory Nerve (XI)
Formed by ventral rami of C1-C4
Cervical Plexus
Formed by ventral rami of: C5-C8 and T1
Brachial Plexus
Roots
Trunks
Divisions
Cords
Brachial Plexus
Innervates deltoid muscle (shoulder abduction)
Brachial Plexus
Axillary Nerve
Innervates
elbow flexors
Brachial Plexus
Musculocutaneous Nerve
Innervates
- most anterior forearm muscles (wrist flexion & abduction)
- carpal tunnel syndrome
Brachial Plexus
Median Nerve
Innervates
-few anterior forearm muscles (wrist flexion and adduction)
Brachial Plexus
Ulnar nerve
-Largest branch of the brachial plexus
Innervates
-all extensor muscles of the upper limb
Brachial Plexus
Radial nerve
Formed by ventral rami of: L1-L4
Lumbar Plexus
-Largest nerve of LUMBAR Plexus
Innervates
-anterior thigh muscles
Lumbar Plexus
Femoral Nerve
Innervates
-adductor muscles in the thigh
Lumbar Plexus
Obturator Nerve
Formed by ventral rami of: L4-S4
Sacral Plexus
Actually two nerves wrapped in sheath
-Thickest/longest nerve in body
Sacral Plexus
Sciatic nerve
Innervates
muscles of the back of thigh, leg and foot
Sacral Plexus
Tibial Nerve
Innervates
anterior & lateral muscles in the lower leg
Sacral Plexus
Common Peroneal nerve
the area of skin innervated by the cutaneous branches of a single spinal nerve
Dermatomes
All spinal nerves except C1 participate in
Dermatomes
mapping is used clinically to determine specific nerve deficit: typical testing includes light touch and pin prick.
Dermatomes
Takes place at a neuromuscular junction
Motor Endings / Innervations of Skeletal Muscle
This junction is the synapse that is formed by the somatic motor efferent axon terminals
and the muscle fibers
Motor Endings / Innervations of Skeletal Muscle
Neuromuscular Junction
is the neurotransmitter that diffuses across the neuromuscular junction
synaptic cleft
Motor Endings / Innervations of Skeletal Muscle
Acetylcholine
___ binds to receptors resulting in:
- Movement of Na+ and K+ across the membrane
- Depolarization of the interior of the muscle cell
- An end-plate potential that triggers an action potential
Motor Endings / Innervations of Skeletal Muscle
Acetylcholine (Ach)