A&P Chapter 13 Flashcards
What is cranial nerve I?
Olfactory
What does cranial nerve I do?
Sense of smell
What is cranial nerve II?
Optic
What does cranial nerve II do?
Sense of vision
What is cranial nerve III?
Oculomotor
What does cranial nerve III do?
Controls muscles that move eye, lift eyelid, and change pupil diameter
What is cranial nerve IV?
Trochlear
What does cranial nerve IV do?
Controls superior oblique eye muscle
What is cranial nerve V?
Trigeminal
What does cranial nerve V do?
Somatic sensation from face, chewing movements
What is cranial nerve VI?
Abducens
What does cranial nerve VI do?
Controls lateral rectus muscle that abducts eye
What is cranial nerve VII?
Facial
What does cranial nerve VII do?
Controls muscles of facial expression and provides signals for taste from tongue
What is cranial nerve VIII?
Vestibulocochlear
What does cranial nerve VIII do?
Senses of hearing and equilibrium
What is cranial nerve IX?
Glossopharyngeal
What does cranial nerve IX do?
Taste and touch from tongue; control of a pharynx muscle
What is cranial nerve X?
Vagus
What does cranial nerve X do?
Visceral sensation; parasympathetic nerve to many organs of the body
What is cranial nerve XI?
Accessory
What does cranial nerve XI do?
Controls muscles of the neck and pharynx
What is cranial nerve XII?
Hypoglossal
What does cranial nerve XII do?
Controls tongue muscles
What is a nerve?
Cordlike organ of PNS
What makes up a nerve?
Bundle of myelinated and nonmyelinated peripheral axons enclosed by connective tissue
What are the two types of nerves?
Spinal or cranial
What dictates the two types of nerves?
Where they originate
Most nerves are mixtures of what?
Afferent/Efferent fibers and somatic/autonomic (visceral) fibers
How are nerves classified?
According to the direction they transmit impulses
What are mixed nerves
Sensory and motor fibers
Where does the impulse travel in mixed nerves?
To and from the CNS
Where does the impulse travel in sensory/afferent nerves?
Oly towards CNS
What is somatic afferent?
Sensory from muscle to brain
What is visceral afferent?
Sensory from organs to brain
Where does the impulse travel in motor/efferent nerves?
Only away from the CNS
What is somatic efferent?
Motor from brain to muscle
What is visceral efferent?
Motor from brain to organs
Mature neurons are _______
Amitotic
If the soma/cell body of the damaged nerve is intact, then the peripheral axon may regenerate in which nervous system
PNS
CNS axons do NOT _____
Regenerate
PNS axons can regenerate if damage is not ______
Severe
What is the process of PNS axons regenerating?
- Axon fragments and myelin sheaths distal to injury degenerate (Wallerian degeneration); degeneration spreads down axon
- Macrophages clean dead axon debris; Schwann cells are stimulated to divide
- Axon filaments grow through regeneration tube
- Axon regenerates, and new myelin sheath forms
What is visceral pain?
Stimulation of visceral organ receptors
How does visceral pain feel?
Vague aching, gnawing, and burning
What activates visceral pain?
Tissue stretching, ischemia, chemicals, muscle spasms
What is referred pain?
Pain from one body region perceived as coming from a different region
What causes referred pain?
Visceral and somatic pain fibers travel along the same nerves, so brain assumes stimulus comes from common (somatic) region
What is an example of referred pain?
Left arm pain during MI
Long -lasting or intense pain, such as a limb amputation can lead to what?
Hyperalgesia, chronic pain, and phantom limb pain
What is hyperalgesia?
Pain amplification
What is phantom limb pain?
Pain felt in limb that has been amputated
How is phantom limb pain prevented?
Epidural anesthesia is used during surgery to reduce phantom pain
How many pairs of spinal nerves are there?
31
How are mixed nerves named?
Point of issue from the spinal cord
Spinal nerves supply all body parts except what?
Head and part of the neck
How many pairs of cervical nerves are there?
8
How many pairs of thoracic nerves are there?
12
How many pairs of lumbar nerves are there?
5
How many pairs of sacral nerves are there?
5 pairs
How many pairs of the tiny coccygeal nerves are there?
1
What is the range of cervical nerves?
C1-C8
What is the range of thoracic nerves?
T1-T12
What is the range of lumbar nerves?
L1-L5
What is the range of sacral nerves?
S1-S5
What is the range of coccygeal nerves?
C0
Each spinal nerve has these two things:
Ventral roots and dorsal roots
What are the ventral roots associated with?
Motor
What are the dorsal roots associated with?
Sensory
The dorsal and ventral roots branch as rootlets, then join to form what?
Spinal nerve
What is ganglia?
Nerve cell bodies
How long are spinal nerves?
~1-2cm
Almost immediately after exiting the foramen, spinal nerves divide into what three branches?
- Posterior/Dorsal ramus
- Anterior/Ventral ramus
- Meningeal branch
What is the posterior/dorsal ramus?
Smaller branch
What is the anterior/ventral ramus?
Larger branch
What is the meningeal branch?
Tiny branch that reenters vertebral canal to innervate meninges and blood vessels
What do rami communicantes contain?
Autonomic nerve fibers that join ventral rami in the thoracic region
What are dermatomes?
Segment of skin supplied by a single spinal nerve
Some dermatomes overlap in what regions?
Innervated
What is an example of a dermatome overlapping?
T10 dermatome = horizontal ring of skin around the umbilicus
What do dermatomes help?
Can help localize damage to one or more spinal nerves
What is an example of dermatomes helping localize damage?
Loss of sensation on medial arm and forearm indicates C8 damage
What type of pain are dermatomes involved in?
Visceral pain
What is a nerve plexus?
Network of interweaving antterior rami of spinal nerves
How many plexuses occur bilaterally?
4
What are the four main plexuses that occur bilaterally?
- Cervical
- Brachial
- Lumbar
- Sacral
What does not form plexuses?
Most thoracic spinal nerves and nerves S5-Co1
Individual rami branch _____
Repeatedly
What does it mean for damage when individual rami branch repeatedly?
Damage to one nerve or spinal segment does not deprive a muscle or skin region of all innervation
The anterior rami of nerves C1-C4 innervate what?
Anterior neck muscles, skin of neck, and portions of the head and shoulders
The rami of C3-C5 gives rise to what?
The phrenic nerve
What does the phrenic nerve innervate?
Diaphragm
What nerves are in the cervical plexus?
C1-C4
Which cervical nerve is not considered part of the cervical plexus?
C5
Irritation of the phrenic nerve causes what?
Spasms of the diaphragm
What are spasms of the diaphragm called?
Hiccups
If both phrenic nerves are severed, or the C3-C5 region of the spinal cord is destroyed, what happens to the diaphragm?
Diaphragm becomes paralyzed
What happens when the diaphragm becomes paralyzed?
Respiratory arrest occurs, victim requires mechanical respirators to stay alive
C3, C4, and C5 keeps the diaphragm ______
Alive
What are the 5 major terminal branches of the brachial plexus?
- Axillary nerve
- Median nerve
- Musculocutaneous nerve
- Radial nerve
- Ulnar nerve
Where is the axillary nerve?
To deltoid and teres major muscles
What does the axillary nerve do?
Sensory input from superolateral arm
Where is the median nerve?
To most anterior forearm muscles and hand muscles
What does the median nerve do?
Sensory input from palmar side and dorsal tips of most fingers, except the pinkie
Where is the musculocutaneous nerve?
Anterior arm muscles (like the biceps brachii)
What does the musculocutaneous nerve do?
Sensory input from lateral forearm
Where is the radial nerve?
To posterior arm muscles (like the triceps brachii) and posterior forearm muscles
What does the radial nerve do?
Sensory input from posterior arm, forearm, and dorsolateral hand
Where is the ulnar nerve?
To anterior forearm muscles, most intrinsic hand muscles
What does the ulnar nerve do?
Sensory input from palmar and dorsal aspect of two medial fingers
Trauma to the radial nerve results in what?
Wrist drop
What is wrist drop?
Inability to extend the hand at the wrist
Improper use of a crutch can compress the ____ nerve and impairs it’s blood supply
Radial
What is “Saturday night paralysis”?
An intoxicated person falls asleep with arm draped over the back of a chair or sofa edge, cutting off blood supply to the radial nerve
The ulnar nerve is very _____ to injury
Vulnerable
Severe or chronic damage to the ulnar nerve can lead to what?
Sensory loss, paralysis, and muscle atrophy
Severe or chronic damage to the ulnar nerve causes the hand to contort into what?
A clawhand
What is a clawhand?
Trouble making a fist and gripping objects. Little and ring fingers become hyperextended at the knuckles and flexed at distal interphalangeal joints
What is striking the “funny bone”?
The spot where the ulnar nerve rests against the medial epicondyle, causes the pinkie finger to tingle
What is the lumbar plexus?
L1-L4
What does the lumbar plexus do?
Innervates thigh, abdominal wall, and psoas muscle
What does the femoral merve do?
Innervates quadriceps and skin of anterior thigh and medial surface of the leg
What does the obturator nerve do?
Passes through obturator foramen to innervate adductor muscles
What is the sacral plexus?
L4-S4
What does the sacral plexus serve?
Buttock, lower limb, pelvic structures, and perineum
What is the sciatc nerve?
Longest and thickest nerve of the body
What does the sciatic nerve do?
Innervates hamstring muscles, adductor magnus, and most muscles in the leg and foot
What two nerves compose the sciatic nerve?
Tibial and common fibular
What is sciatica characterized by?
Stabbing pain radiating over the course of the sciatic nerve
What can injure the sciatic nerve?
A fall, disc herniation, or a badly placed injection into the buttock
If the sciatic nerve is transected, what happens to the leg?
Leg is nearly useless and cannot be flexed because the hamstrings are paralyzed
If the sciatic nerve is transected, what happens to the foot and ankle?
Foot and ankle cannot move at all, so foot drops into plantar flexion
What is footdrop?
Foot drops into plantar flexion
Recovery from sciatic nerve injury is usually ____ and _____
Slow and incomplete
For sciatic nerve injury below the knee, thigh muscles are _____
Spared
If the tibial nerve is injured, the paralyzed calf muscles cannot do what action?
Plantar flex foot
What creates a shuffling gait?
When the calf muscles cannot plantar flex the foot
What is a reflex?
Involuntary responses
What is required to initiate a reflex?
Stimulus
The response of a reflex is _____
Rapid
Only a few neurons are involved in ____
Reflexes
The response in reflexes are ______
Preprogrammed; always the same
Reflexes are _______
Involuntary; no intent or awareness of the reflex before it happens
A reflex is a ______ mechanism
Survival
Why is a reflex a survival mechanism?
We respond to a potentially detrimental stimulus immediately and awareness comes later
What are the five basic components of all reflex arcs?
- Receptor
- Sensory neuron
- Integration center
- Motor neuron
- Effector
How can reflexes vary?
- Spinal or cranial
- Somatic or visceral
- Monosynaptic or polysynaptic
- Ipsilateral or contralateral
- Innate or acquired
What does spinal or cranial mean?
Is the spinal cord or brain the reflex integration center?
What does somatic or visceral mean?
Is the effector a skeletal msucle or is it cardiac muscle, smooth muscle, a gland?
What does monosynaptic or polysynaptic mean?
Do sensory neurons synapse directly with motor neurons or are there interneurons in the reflex arc?
What does ipsilateral or contralateral mean?
Are receptors and effectors on the same side of the body or on opposite sides?
What does innate or acquired mean?
Are you born with the reflex or do you develop it after birth
What is an inborn (intrinsic) reflex?
Rapid, involuntary, predictable motor response to a stimulus
What are examples of an inborn reflex?
Maintain posture, control visceral activites
Inborn reflexes can be modified by what?
Learning and concious effort
What are learned (acquired) reflexes?
Result from practive or repetition
What is an example of learned reflexes?
Driving skills
Reflexes are classified functionally as what two things?
Somatic and autonomic
What do somatic reflexes do?
Activate skeletal muscle
What do autonomic (visceral) reflexes do?
Activate visceral effectors (like smooth or cardiac muscle or glands)
What is a monosynaptic reflex?
Direct communication between the sensory and motor neuron
What is an example of a monosynaptic reflex?
Stretch reflex
What is a polysynaptic reflex?
Interneuron facilitates sensory-motor communication
What is an example of a polysynaptic reflex?
Withdrawal reflex
Reflexes are useful for what?
Diagnoses
What can reflexes test?
Function of specific muscles, nerves, and spinal segments
What is a hypoactive reflex?
Diminished or absent
What does a hypoactive reflex indicate?
Damage to the spinal cord, muscle disease, or damage to neuromuscular junction
What is a hyperactive reflex?
Abnormally strong response
What does a hyperactive reflex indicate?
Damage to brain or spinal cord, especially if accompanied by clonus
What is clonus?
Rhythmic oscillating movements with reflex testing
Stretch reflexes can be hypoactive or absent if what happens?
Peripheral nerve damage or ventral horn injury has occured
Stretch reflexes are absent in who?
People with chronic diabetes mellitus or neurosyphilis, and during coma
Stretch reflexes can be hyperactive if what occurs?
Lesions of corticospinal tract reduce inhibitory effect of brain on the spinal cord
If the primary motor cortex or corticospinal tract is damaged, what happens to the plantar reflex?
Replaced by an abnormal reflex called the Babinski’s sign
What is Babinski’s sign?
Great toe dorsiflexes and smaller toes fan laterally
Why do infants exhibit Babinski’s sign?
Their nervous systems are not completely myelinated
When do infants stop exhibiting Babinski’s sign?
Until they are about a year old
