Spinal Nerves and Reflex Activity Flashcards Preview

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Flashcards in Spinal Nerves and Reflex Activity Deck (34)
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1
Q

Structure of Nerve

A
  • Endoneurium - loose connective tissue that encloses axons and their myelin sheaths
  • Perineurium - coarse connective tissue that bundles fibers into fascicles
  • Epineurium - tough fibrous sheath around a nerve
2
Q

Spinal Nerves

A

31 Pairs of mixed nerves according to their point of issue from the spinal cord

  • 8 cervical (C1-C8)
  • 12 Thoracic (T1-T12) - intercostal nerves
  • 5 Lumbar (L1-L5)
  • 5 Sacral (S1-S5)
  • 1 Coccygeal (C0)
3
Q

Spinal Nerves: Roots

A
  • Ventral Roots - contain motor (efferent) fibers
    • fibers innervate skeletal muscles
  • Dorsal Roots - contains sensory (afferent) fibers
    • conduct impulses from peripheral receptors
4
Q

Spinal Nerves: Rami

A

Each spinal nerve divides into 3 branches or rami

  • ​​​Dorsal Ramus - the back is innervated by dorsal rami posterior side
  • Larger ventral ramus
  • Rami Communicans - autonomic pathways join to the ventral rami in the thoracic region
5
Q

Spinal Nerves: Plexuses

A
  • Cervical Plexus
  • Brachial Plexus
  • Lumber Plexus
  • Sacral Plexus
  • Advantage: damage to one spinal segment does not completely paralyze any limb segment
6
Q

All ventral rami except __-__ form interlacing nerve networks called _______

A
  • T2-T12
  • Plexuses
7
Q

Ventral rami of T2-T12 as _______ ____ supply muscles of the rib, anterolateral thorax, and abdominal wall

A

intercostal nerves

8
Q

Cervical Plexus

A

formed by ventral rami of C1-C4

  • innervates skin and muscles of the neck, ear, back of head, and shoulders
9
Q

Phrenic Nerve

A
  • Major motor and sensory nerve of the diaphragm irritation - hiccups
  • Damage - paralysis of diaphragm
10
Q

Brachial Plexus

A
  • Formed by ventral rami of C5-C8 and T1
  • Innervates the upper limb
  • Major Branches:
    • Axillary
    • Musculocutaneous
    • Radial - largest branch
    • Median
    • Ulnar
11
Q

Injury to the brachial plexus

A

paralysis of entire upper limb

12
Q

Median Nerve compression

A

carpel tunnel syndrome

Pincer grasp affected

13
Q

Injury to the ulnar

A

striking the “funny bone”

14
Q

Radial Nerve Trauma

A

Improper use of crutch, wrist drop or “Saturday night paralysis”

15
Q

Lumbar Plexus

A
  • L1-L4
  • Femoral nerve - largest nerve of this plexus
    • prime mover of hip flexion and knee extension
  • Obturator nerve- passes through obturator foramen to innervate adductor muscles (inner thigh muscles)
16
Q

Sacral Plexus

A
  • L4-S4
  • serves the buttock, lower limb, pelvic structures, and perineum
  • Sciatic Nerve
    • longest and thickest nerve in body
    • 2 nerves: tibial and common fibular
    • Innervates the hamstring muscles, and most muscles in the leg and foot
  • Pudendal Nerve - supplies perineum
    • stimulates erection and controls urination
17
Q

Injury to the proximal portion of the sciatic nerve

A

Sciatica

stabbing pain radiates over the course of the sciatic nerve

18
Q

Injury to the common fibular

A

Foot Drop

Dorsiflexion is lost and foot dangles in planter flexion

19
Q

Calf muscles affected

A

Injury to tibial nerve

20
Q

Anesthetics -

A

Pudenal nerve - episiotomy

21
Q

The area of skin innervated by the cutaneous branches of a single spinal nerve

A

Dermatome

most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness

22
Q

__ dermatomes for 31 spinal nerves

A

30

23
Q

All spinal nerves except __ participate in dermatomes

A

C1

24
Q

*Dermatome Map*

A
25
Q

A reactivation of the chickenpox virus in the body, causing a painful rash

A

Shingles

26
Q

A rapid, involuntary, predictable motor response to a stimulus

A

inborn (intrinsic) reflex

27
Q

Result from practice or repetition

A

Learned (acquired) reflexes

28
Q

By Complexity…

A
  • Monosynaptic vs. Polysynaptic
  • ipsilateral vs. contralateral
29
Q

Reflex Arc

A
  1. Receptor - site of stimulus action
  2. Sensory Neuron - transmits afferent impulses to the CNS
  3. Integration Center - either monosynaptic (1 synapse) or polysynaptic (2 or more) within the CNS
  4. Motor Neuron - conducts efferent impulses from the integration center to an effector organ
  5. Effector - muscle fiber or gland cell that responds to the efferent impulses by contracting or secreting
30
Q

Stretch/Extension/Patellar Reflexes

A
  • maintain muscle tone in large postural muscles
  • all stretch reflexes are monosynaptic and ipsilateral
  • 2 neurons
31
Q

Flexor/Withdrawal Reflexes (typical reflex arc)

A
  • initiated by painful stimulus
  • 3 neurons
  • Polysynaptic
  • Ipsilateral
32
Q

Crossed-Extensor Reflexes (step on a tac)

Intersegmental reflex

A
  • Contralateral
  • 3 or more neurons
  • Polysynaptic
33
Q

Same side

vs.

Opp. side

A

Sensory and motor neurons - ipsilateral

vs.

Association (Grey commissure) - Contralateral

34
Q

Superficial Reflexes

A
  • Plantar Reflex
    • downward flexion of toes
    • tests for function of corticospinal tracts
  • Babinski’s sign
    • Dorsiflexion of hallux and fanning of toes
    • present in infants due to incomplete myelination
    • in adults, indicates corticospinal or motor cortex damage