Lecture 7 part two (SECOND MIDTERM) Flashcards
The lower motor neurons send their axons out through where?
the ventral root
2 very basic types of reflex arcs:
Monosynaptic: one synapse
Polysynaptic: more than one synapse
Example of monosynaptic reflex arc and of polysynaptic reflex arcs:
mono: stretch reflex
poly: withdrawal reflex (flexor reflex) and crossed extensor reflex
Stretch reflex:
stretches receptors inside of the muscle; signal is carried through by somatic afferent neuron and it goes directly to the motor nuclei; will contract the muscle in defense
Stretch reflex muscles and main nerves associated with them:
Biceps: C5, C6 Brachioradialis: C6 Triceps: C7 Patellar: L4 Calcaneal Tendon: S1
A patient has no patellar stretch reflex. Where is the damage?
L4
What do interneurons do? Where are they located?
- they distribute sensory information and coordinate motor activity
- located between sensory and motor nerves
- the more complex the response to a given stimulus, the more interneurons are involved!
The 2 different types of signals being sent in withdrawal reflex (flexor reflex) and cross extensor reflex:
inhibitory
excitatory
In a cross extensor reflex, a motor response to the stimulus also occurs where?
on a side opposite the stimulus
The protective coverings of the nerves are known as…
meninges
3 meninges from outer to inner:
dura mater (tough mother) arachnoid mater (spider mother) pia mater (soft mother)
The meninges only exist where?
around the CNS
The pia mater has little extensions coming off called…
What do they do?
denticulate ligaments
-prevents spinal cord by moving around and slamming against vertebral column
The nerve and nerve roots get “dragged” in what direction?
caudal (inferior)
Bones continue to grow, but what stops growing? What also keeps growing?
- the central nervous system stops growing
- the peripheral nervous system keeps growing
Where the spinal column and spinal cord taper off, it is called…
the conis medullaris
The conis medullaris has this little “piece” of connective tissue coming all the way down and anchoring it at the very end of the meninges; where the dura ends, what anchors the conis medullaris?
filum terminale (terminal thread) (prevents movement and damage to spinal cord)
The portion with all of the nerve roots that contributes to the spinal nerves emerging after is called what?
cauda equina
What is the specific bilateral region of the skin surface monitored by a single pair of spinal nerves?
dermatome
A complex interwoven network of nerves is called a…
nerve plexus
What are the only rami involved in the nerve plexus for our limbs?
ventral rami
Your limbs only develop from what region?
hypaxial
Because your limbs only develop from the hypaxial region, they get their nerve innervation from…
ventral rami
Usually how many segments combine to form a limb?
6
Dorsal divisions serve what muscles? Ventral divisions?
Dorsal: dorsal muscles (extensors, elevators)
Ventral: ventral muscles (flexors, depressors)
In the Lumbosacral plexus…
Cranial division:
L2, L3, L4
In the Lumbosacral plexus…
Caudal division:
L5, S1, S2
When you combine the peroneal (fibular) nerve and tibial nerve, it forms one single nerve called…
the sciatic nerve
Femoral nerve..
Roots and selected muscles
L2, L3, L4
Hip flexors, quadriceps
Obturator nerve…
Roots and selected muscles
L3, L4
Adductors
Peroneal nerve…
Roots and selected muscles
L4, L5
Tibialis anterior
Superior gluteal nerve…
Roots and selected muscles
L4, L5, S1
Gluteus medius and gluteus minimus
Tibial nerve…
Roots and selected muscles
S1, S2
Gastrocnemius
In the Brachial plexus... Segmental roots: Trunks: Divisions: Cords: Terminal nerves:
Segmental roots: C4, C5, C6, C7, C8, T1
Trunks: Superior, middle, inferior
Divisions: each of the 3 trunks divides into dorsal or ventral
Cords: posterior (dorsal divisions) and lateral & medial (ventral divisions)
Terminal nerves: posterior cord = axillary nerve, radial nerve. lateral & medial cords = musculocutaneous nerve, median nerve, ulnar nerve
In the Brachial plexus, a “root” can mean…
a spinal nerve which is contributing to the formation of a plexus
Axillary nerve…
Roots and selected muscles
C5, C6
Deltoid, long head of triceps brachii
Musculocutaneous nerve…
Roots and selected muscles
C5, C6
Biceps brachii, brachioradialis
Radial nerve…
Roots and selected muscles
C7, C8
Other triceps heads, extensors
Median nerve…
Roots and selected muscles
C8, T1
Most wrist flexors, radial side digital flexors
Ulnar nerve…
Roots and selected muscles
C8, T1
Ulnar side wrist and digital flexors
The lateral cord and medial cord combine into what?
the median nerve
Basic concept…
Paresis:
Plegia:
Paresis: weakness
Plegia: paralyzed
Quadriplegia:
Paraplegia:
Hemiplegia:
Monoplegia:
Quadriplegia: all 4 limbs are paralyzed
Paraplegia: lower limbs are paralyzed
Hemiplegia: one side is paralyzed
Monoplegia: one limb is paralyzed
Lower motor neuron lesion characteristics:
- Atrophy (because of the lack of nutrition; trophic factors)
- Hypotonia: lost of lower reflexes; flaccid
- Hyporeflexia: don’t show the reflex
- Tends to affect small groups of muscle
Damage to peroneal nerve could be from damage of what? or what nerve root?
What is a sign?
- Trauma to knee or fibula
- Nerve root L4, L5, S1 lesion
- Foot drop, toe drag (equine gait, stoppage gait, slapping gait
Damage to superior gluteal nerve could be from damage of what?
What is a sign?
- Trauma to buttocks (stabbing, intramuscular injection)
- Hip drop (waddling gait)
What is Saturday night palsy (crutch palsy) is a result from damage of what?
What is a sign?
- Damage to radial nerve
- Wrist drop, inability to extend arm
Upper motor neuron lesion characteristics:
- Atrophy is RARE
- Hypertonia: contant contraction; rigid & tight (spasticity = quick very strong stretch reflex. Clonus = stretches and locks in place)
- Hyperreflexia: reflexes are stronger
- Tends to affect large groups of muscle
- Muscles working against gravity are stronger (pointing toes, upper limb flexors, lower limb extensors)
What may be the cause of circumduction gait (hemiparesis)? Signs?
- May be due to stroke, or even lesion in cervical spinal cord that affects one side
- Leg extensors are hypertonic, difficult to flex knee and raise toes
What may be the cause of scissors gait (paraparesis)? Signs?
- May be due to trauma in thoracic region or cerebral palsy
- Leg extensors are hypertonic, difficult to flex knees and raise toes
