Nervous system (Intro) Flashcards
Neuron =
nerve cell
Neuron def:
Basic structural and functional component of the NS
Describe dendrites
- Cytoplasmic processes, reception of stimulus, impulses to cell body, multiple per neuron
Axon =
nerve fiber
Describe Axons
- Cytoplasmic process
- only one per neuron
- conduct impulses away from cell body
- may have several collateral branches
- have neurofibrils
Where is epineurium?
Around the whole nerve
Where is perineurium?
Around the fascicles
Where is endoneurium?
Around the nerve fibers (axons)
What are the qualities of a nerve (2)?
- Excitability (respond to stimuli and generate nerve impulses)
- Conductivity (transmit a state of excitation)
What is the “H” formation (nuclei) on the spinal cord?
Grey matter
What is grey commissure?
Zone that connects the 2 hemispheres (surrounds central canal of spinal cord)
What is the nuclei of grey matter?
mass of nerve cell bodies and dendrites inside the CNS
What surrounds grey commissures?
Areas of white matter
White matter =
Nerve fibers w/ myelin sheath coverings
Each white nerve bundle =
tract
What are the spinal cord regions?
- Cervical (thick grey matter)
- Thoracic
- Lumbar (thick grey matter)
- Sacral (thick grey matter: more activity)
What are the ascending tracts of the spinal cord (toward the brain)
Sensory or afferent
What are the descending tracts of the spinal cord (away from brain)
Motor or efferent
Where are white tracts found in comparison to the grey commissure?
Ant., post., and lat.
Dorsal roots:
- groups of nerve fibers entering dorsal horn
- contain sensory neurons
Ventral roots:
- groups of nerve fibers leaving ventral horns
- contain motor neurons
Dorsal root + ventral root =
spinal nerve
Spinal nerves =
mixed nerves (sensory +motor)
Number of spinal nerves:
31 pairs
When do spinal nerves divide?
After leaving intervertebral foramen
what do Dorsal rami innervate?
skin of back, paravertebral muscles
what do Ventral rami innervate?
all extremity muscles, lateral and ventral trunk
Nerve root distribution: Vertebrae
- Cervial - 7
- Thoracic - 12
- Lumbar - 5
- Sacral (Sacrum) - 5
- Coccygeal (Coccyx) - 4
Total: 33
Nerve root distribution: spinal nerves
- Cervical - 8
- Thoracic - 12
- Lumbar - 5
- Sacral - 5
- Coccygeal -1
Total: 31 pairs
Networks:
Ventral rami of spinal nerves from plexuses (plexi)
EXCEPT: T2-T12 and S5-Co1
What are the nerve plexuses:
- Cervical: C1-C4
- Brachial: C5-T1
- Lumbar: L1-L4
- Sacral: L4/L5-S4
- Lumbar + Sacral = Lumbosacral
Brachial Plexus: “Risk Takers Don’t Cautiously Behave”
Rami
Trunks
Divisions
Cords
Branches
Brachial plexus: cords named in relation to
axillary artery
Brachial plexus: covered by connective tissue
axillary sheath
Brachial plexus: location
- Descends and passes over 1st rib, behind clavicle into axilla
- accompanies axillary artery + vein
- Posterior to Pec Major
Brachial plexus trunks:
- Upper trunk: ventral rami of C5 and C6 join
- Middle trunk: ventral rami of C7 continues
- Lower trunk: ventral rami of C8 and T1 join
Brachial Plexus: Each trunk divides into an:
anterior and posterior division
Brachial Plexus: 3 posterior divisions form the:
posterior cord
Brachial Plexus: anterior division of the lower trunk forms the:
medial cord
Brachial Plexus: anterior divisions of the upper and middle trunks form the:
Lateral cord
Brachial plexus: the posterior cord becomes the:
radial n.
Brachial Plexus: the major branch of radial n. is the
axillary n.
Brachial Plexus: the 3 nerves in the “M”:
- musculocutaneous n.
- median n.
- ulnar n.
Brachial Plexus: the lateral and medial cords form the
median n.
Brachial Plexus: the medial cord becomes the
ulnar n.
Brachial Plexus: the lateral cord branches off to the
musculocutaneous n.
What are the ventral rami of the terminal nerve branches of the brachial plexus?
- Radial n: C5-C8, T1
- Axillary n: C5-C6
- Musculocutaneous n: C5-C7
- Median n: C5-C8, T1
- Ulnar n: (C7), C8, T1
Which nerve passes through the radial groove of the humerus?
radial n.
Describe the radial n.
- largest branch of brachial plexus
- behind axillary a.
- in front of subscapularis
- innervates post. upper extremity
- under triceps
- deep into antecubital fossa, behind brachialis and brachioradialis
- ends in lateroposterior forearm
- reflexes: brachioradialis (C6), triceps (C7)
Describe the axillary n.
- branch of post. cord
- lateral to radial n.
- medial to surgical neck of humerus b.
- into deltoid m. and teres minor m.
describe the musculocutaneous n.
- pierces coracobrachialis m.
- anterior arm muscles (biceps, brachialis, coracobrachialis)
- reflex: biceps (C5)
describe the median n.
- most forearm flexor m. (except brachioradialis and flexor carpi ulnaris)
- thumb side of hand and wrist
- superficial at anterior wrist
describe the ulnar n.
- passes behind medial epicondyle
- runs down medial forearm
- some flexor muscles and many intrinsic muscles of the hand
What is the definition of a dermatome?
The area of skin providing sensory input to the post. roots of 1 spinal segment
Describe dermatomes
- skin supplied by somatic sensory n.
- afferent n.
- all spinal n. have branches from the skin EXCEPT C1
- no exact boundaries
- considerable overlap
- lesion to 1 spinal n. may be little or no loss of sensation
- usually 3 adjacent lesion for complete anesthesia to a dermatome
Where does the spinal cord end?
Around L2
Injuries to nerves emerging from brachial plexus:
- Erb-Duchenne palsy (waiter’s tip)
- Wrist drop
- median nerve palsy
- ulnar nerver palsy
- winging of right scapula b. (could be due to serratus ant. and long thoracic n.)
