Nervous System, Dermatomes, Myotomes

Question 1

Nervous System

Answer 1

Complex system responsible for information processing in the body; consists of two subdivisions: central (CNS) and peripheral (PNS)

Question 2

Central nervous system

Answer 2

Brain + spinal cord; integrating, processing, coordinating sensory input and motor output; seat of higher functions

Question 3

Peripheral nervous system

Answer 3

All neural tissue outside CNS; includes spinal/cranial nerves; provides sensory information to CNS (afferent) and carries motor commands from CNS to peripheral tissues and systems (efferent)

Question 4

Somatic nervous system

Answer 4

Branch of PNS; “relating to the body”; innervate skeletal muscles; carry both motor and sensory information (voluntary or involuntary)

Question 5

Autonomic nervous system

Answer 5

Branch of PNS; AKA visceral “guts”; regulates smooth muscle, cardiac muscle, and glandular activity; mostly involuntary

Question 6

3 Branches of the autonomic nervous system

Answer 6

sympathetic (fight/flight), parasympathetic (rest/digest), and enteric nervous system (gastrointestinal, quasi-autonomic)

Question 7

Dermatome

Answer 7

Area of skin innervated by a specific spinal nerve

Question 8

Purpose of sensory testing using dermatomes

Answer 8

Suggestive of function of central and peripheral components of the nervous system; NOT diagnostic, but localize neurological injury

Question 9

pyramidal tracts

Answer 9

major pathways of VOLUNTARY MOTOR signals

consists of the corticospinal and corticobulbar tract

Question 10

Somatotopical organization of neurons within primary motor cortex

Answer 10

neurons related to similar regions are grouped together; demonstrated by motor homunculus

Question 11

motor homunculus

Answer 11

conceptual topographical map across the top of your brain; demonstrates somatotopical organization

Question 12

Somatotopical organization: large hands and small feet on the homunculus

Answer 12

hands have a greater portion of the motor cortex dedicated to them as they require or are capable of greater motor control than the feet

Question 13

Motor cortex

Answer 13

controls the movement of the voluntary muscles

housed within the frontal lobe towards the middle of the brain

Question 14

spinal cord

Answer 14

relays information between the brain and the rest of the body

Question 15

anterior (ventral) root of spinal nerve

Answer 15

axons control movement and automatic functions of the body like sweating and heart rate (descending)

Question 16

posterior (dorsal) root of the spinal nerve

Answer 16

axons transmit sensory information like temperature, pain and pressure back to the brain (ascending)

Question 17

corticospinal tract

Answer 17

motor pathway from the brain’s primary motor cortex to the the spinal cord, where they synapse with motor neurons

responsible for voluntary movement of the muscles of the limbs and trunk

Question 18

anterior corticospinal tract

Answer 18

provide motor innervation to back as well as the axial muscles of the trunk; important role in maintaining posture

Question 19

lateral corticospinal tract

Answer 19

supply motor innervation to the distal parts of the extremities like the hand; important for performing skilled voluntary movements

Question 20

corticobulbar tract

Answer 20

motor pathway from the primary motor cortex of the brainstem, where they synapse with motor cranial neurons

responsible for control of muscles in the face, head, and neck

AKA corticonuclear tract

Question 21

two main parts to the journey of a motor signal

Answer 21

1 CNS = motor cortex of the brain to the spinal cord, includes the pyramidal tract
2 PNS = spinal cord to the muscle

Question 22

upper motor neurons

Answer 22

Motor neurons found within CNS

Question 23

lower motor neurons

Answer 23

motor axons found in PNS

Question 24

damage to upper motor neurons

Answer 24

CENTRAL PARALYSIS
SPASTICITY (increased muscle tone)
muscle weakness
decreased motor control (esp. fine or skilled movements)
hyperreflexia (exaggerated tendon reflexes)
clonus (repeating deep tendon reflexes)
Babinski sign

Question 25

damage to lower motor neurons

Answer 25

``` PERIPHERAL PARALYSIS FLACCIDITY (decreased muscle tone) depressed or areflexic deep tendon reflexes muscle atrophy Fasciculation (random muscle twitches) ```

Question 26

efferent

Answer 26

conducting information away from CNS

Question 27

afferent

Answer 27

conducting information towards CNS

Question 28

pyramidal cells

Answer 28

neurons of the primary motor cortex

Question 29

Betz cells

Answer 29

giant pyramidal cells

Question 30

5 Step summary of Corticospinal Tract

Answer 30

1 Superior brain (pyramidal cells in motor cortex) 2 Inferior brain (internal capsule, midbrain, pons) 3 Brainstem (Medulla); pyramid decussation; crossed fibers = lateral tract; uncrossed fibers = anterior tract 4 Spinal cord; lower motor neurons leave spinal cord via ventral root and form peripheral nerves 5 Muscles

Question 31

Difference in decussation between corticospinal tract and corticobulbar tract

Answer 31

corticospinal tract = occurs at the junction of the medulla oblongata and spinal cord corticobulbar tracts = occurs above each relevant cranial nerve nuclei (do not enter the spinal cord since they do not travel further than the neck)

Question 32

Decussation: difference in input received by lower motor nuclei of cranial nerves and lower motor neurons of the rest of the body

Answer 32

cranial nerves = receive input through bilateral innervation | rest of the body = receive motor input mostly from the contralateral hemisphere

Question 33

corticospinal tract: injury above pyramidal decussation vs injury below

Answer 33

``` above = contralateral (opposite side) motor deficits below = ipsilateral (same side) motor deficits ```