Nervous System Introduction, Brachial Plexus

Question 1

List the functions of the nervous system

Answer 1

• Sensory, Motor, Cognitive

Question 2

Name the major components of the nervous system

Answer 2

DIAGRAM - Anatomical organization of the nervous system

Question 3

Compare characteristics of the central and peripheral nervous system

Answer 3

Central Nervous System (CNS)
- Unpaired, bilaterally symmetrical structure extending along the longitudinal axis of the midsagittal plane of the body
- Structures arising directly from the neural tube.
- Includes: brain, spinal chord
Peripheral Nervous System (PNS)
- Made up of transmission pathways carrying information between the CNS and external/internal environments.
- Afferent (sensory) pathways: carry information to the CNS
- Efferent (motor) pathways: carry information form the CNS.
- Includes: Cranial nerves (12 pairs) , spinal nerves (31 pairs)
- Also includes sensory receptors in skin and wall of gut tube as well as in tendons and skeletal muscles
- Also includes motor end plates between motor neurons and skeletal muscle fibers.

Question 4

How many cranial nerve pairs and spinal nerve pairs are there?

Answer 4

• PNS includes cranial nerves (12 pairs), spinal nerves (31 pairs)

Question 5

Describe characteristics of the autonomic nervous system, compare its two subdivisions and explain why it might be considered a subdivision of the peripheral nervous system.

Answer 5

• considered a subdivision of the PSN. WHY???**
• Entirely motor
• Innervates smooth muscle and glands (viscera)
  ANS subdivisions
• Sympathetic system: fight or flight, also called thoracolumbar
• Parasympathetic system: feed and breed (rest and digest), also called craniosacral.

Question 6

Describe the general development pattern of the central nervous system and list the major derivatives from the cranial end of the neural tube.

Answer 6

Stages in neural tube development 
- Neural plate
- Neural folds
- Neural tube
Subdivision of cranial end of tube
- Tripartite brain
- Pentapartite brain. ** do we need to know slides 12-16?

Question 7

Describe the basic structural (anatomical) unit of the nervous system

Answer 7

• Cell body: tropic unit, perikaryon
• Dendrites: receptive unit
• Axon: conductive unit

Question 8

Describe the characteristics of the cell body

Answer 8

- part of a neuron that encloses the nucleus and other organelles necessary to maintain and repair neurons
Cell body organelles:
- Nucleus 
- Golgi apparatus
- RER: Ribosomes, =Nissan substance.

Question 9

Describe the characteristics of the dendrites

Answer 9

• branches off the cell body that carry information to the cell body
• usually several to many
• relatively short
• often branched
• have receptors for neurotransmitters
• conduct local potentials

Question 10

Describe the characteristics of the axon

Answer 10

• part of the neuron that carries information to another neuron or muscle cell
• relatively long
• single
• conducts action potential (nerve impulse)
• cell membrane is called axolemma
• cytoplasm is called axoplasm.
• ends in short branched processes called telodendria: give off endings Calle terminal boutons, terminal boutons contain synaptic vesicle of neurotransmitters.
• may ave collateral branches
• contain: mitochondria, neurofilaments, neurotubules
• covered by neurolemma: often myelinated
• Note: axon is only part of neuron that is ever myelinated

Question 11

Describe the myelin sheath and identify the cells that form the myelin sheath

Answer 11

• Myelin is formed by Schwann cells

- Describe myelin sheath???? **

Question 12

Name and describe the branches of the typical spinal nerve and distinguish between afferent and efferent paths

Answer 12

Spinal Nerve Branches
- Dorsal primary ramus
- Ventral primary ramus
- Ramus recurrens
- White ramus communicants 
- Gray ramus communicants
Reflex Arc
- Afferent (sensory) pathways: somatic, visceral (splanchnic)
- Efferent (motor) pathways: somatic, visceral  (splanchnic)

Question 13

Nucleus

Answer 13

• aggregation of dendrites and nerve cell bodies in the CNS

Question 14

Ganglion

Answer 14

• aggregation of dendrite and nerve cell bodies in the PNS

Question 15

Nerve

Answer 15

• bundle of fibers (axons) in the PNS

Question 16

Tract

Answer 16

• bundle of fibers (axons) in the CNS

Question 17

Commissure

Answer 17

• tract in the CNS that crosses from one side to the other

Question 18

White matter

Answer 18

• areas of myelinated axons

Question 19

Gray matter

Answer 19

• areas of unmyelinated axons, cell bodies, and dendrites

Question 20

Describe a reflex arc and distinguish between monosynaptic and polysynaptic reflex arcs

Answer 20

Reflex arc
- Afferent (sensory) pathways
- Efferent (motor) pathways
- Association neurons (interneurons)
Synapse
- Monosnaptic pathways: Fig. 1-29
- Polysynaptic pathways: Fig. 1-29

Question 21

List and describe the components of a synapse

Answer 21

• Presynaptic membrane: with synaptic vesicles filled with neurotransmitters
• Synaptic cleft:
• Postsynaptic membrane: with receptors for neurotransmitters

Question 22

Describe the general cross-sectional anatomy of the spinal cord and distinguish between columns and horns

Answer 22

• Fig 1-34 —- 1-43
  Cross-sectional anatomy of the spinal cord is organized into horns and columns
• Horns: arenas of gray matter, posterior (dorsal), anterior (ventral), lateral
• Columns: areas of white matter, posterior (dorsal), lateral, anterior (ventral)

Question 23

Describe the overall morphology of the spinal cord

Answer 23

• Cross-section through spinal cord showing locations of gray matter (blue) and white matter (yellow).
• Also note central canal and “H”-shape of gray matter
• Cross-section through human spinal cord showing locations of ascending and descending tracts.

Question 24

Explain how spinal nerves are numbered

Answer 24

** slide 38

Question 25

List the contents of the axillary sheath

Answer 25

- Axillary artery - Axillary vein - Brachial plexus

Question 26

Draw the components of the brachial plexus as related to the rami, trunks, cords and terminal nerves.

Answer 26

** slide 46?

Question 27

List the ventral rami that give rise to the brachial plexus and the direct branches from these rami

Answer 27

Ventral rami of C5-T1 - exits neck between scalenus anterior and scalenus mediums muscles Direct branches from rami - Dorsal scapular nerve: C5 to rhomboid muscles - Long thoracic nerve: C5-7 to serrated anterior muscle

Question 28

Identify the trunks of the brachial plexus, the rami that form the trunks and direct branches from the trunk(s)

Answer 28

Formed by ventral rami, located superior to clavicle above and behind subclavian artery - superior (upper): from C5 and C6 ventral rami - middle: from C7 ventral ramus - interior (lower): from C and T1 ventral rami Direct branches from trunk - from superior trunk - Suprascapular nerve: C5, C6, to supraspinatus and infraspinatus muscles - Nerveto subclavius

Question 29

Distinguish between the anterior and posterior divisions of the brachial plexus and identify the destinations of the fibers they carry.

Answer 29

Anterior divisions - carry fibers from trunks to anterior compartments of upper extremity - form lateral and medial cords Posterior divisions - carry fibers from trunks to posterior compartments of upper extremity - from posterior cord

Question 30

Identify the cords of the branches plexus, their relations to the axillary artery, and their origins

Answer 30

Accompany axillary artery: named for relationship to artery - Lateral: from anterior divisions of upper and middle trunks - Posterior: form posterior division of all trunks - Medial: from arterial division of lower trunk

Question 31

For the lateral cord of the bronchial plexus, identify direct and terminal branches, spinal cord levels, and specific muscles innervated

Answer 31

Direct branches - lateral pectoral nerve: C5-7, to clavicles head of pectoralis major muscle. Terminal nerves - musculocutaneous: C5-7 - lateral root of median nerve: C5-7

Question 32

For the medial cord of the bronchial plexus, identify direct and terminal branches, spinal cord levels, and specific muscles innervated

Answer 32

Direct branches - medial pectoral nerve: C8-T1, to eternal head of pectoralis major muscle and pectoralis minor muscle. - medial cutaneous nerve to arm (brachium) - medial cutaneous nerve to forearm (antebrachium) Terminal branches: - Ulnar: C8-T1 - Medial root of median nerve: C8-T1

Question 33

For the posterior cord of the bronchial plexus, identify direct and terminal branches, spinal cord levels, and specific muscles innervated

Answer 33

Direct branches - upper subscapular nerve: C5(6), to subscapularis muscle - Thoracodorsal nerve: C6-7, to latissimus dorsi muscle - Lower subscapular nerve: C(5)6, to subscapularis and there’s major muscles Terminal branches - Axillary nerve: C5-6 - Motor: to deltoid and there’s minor muscles - Sensory: skin on the arm over deltoid muscle, upper lateral cutaneous nerve - Radial nerve: C5-T1 - Motor: posterior compartments of arm and forearm, brachioradialis muscle - Sensory: back of arm, forearm, hand