Clinical Anatomy of Motor Systems I

Question 1

What are descending tracts

Answer 1

Pathways by which motor signals are sent from the brain to LMN which innervate muscles to produce movement

Question 2

Two groups of Descending Tracts

Answer 2

Pyramidal Tracts

Extrapyramidal

Question 3

Where do pyramidal tracts originate

Answer 3

cerebral cortex

Question 4

Function of Pyramidal Tracts

Answer 4

responsible for the voluntary control of the musculature of the body and face

Question 5

What is the clinical division of pyramidal tracts

Answer 5

Corticospinal Tract (supplies musculature of body)

Corticobulbar Tract (supplies musculature of head and neck)

Question 6

Function of Corticospinal

Answer 6

supplies musculature of the body

Question 7

Pathway of Corticospinal Tract

Answer 7

Originates in the cerebral cortex (primary motor, premotor, supplementary motor)

Descends through internal Capsule

Passes through the CRUS CEREBRI of the midbrain, pons and into the medulla

Divides into two tracts
-Lateral Corticospinal
-Anterior Corticospinal

Question 8

Pathway of Corticobulbar Tract

Answer 8

Originates in the lateral aspect of the primary motor cortex

Descends through internal capsule to the brainstem

Terminate on motor nuclei of the cranial nerves (Hyposglossal)

Synapse with LMN to carry motor signals to the head and neck

Question 8

Clinical Relevance of Pyramidal Tracts

Answer 8

The internal capsule is susceptible to compression from hemorrhagic bleeds, could potentially cause lesion on pyramidal tracts

Loss in motor control

Question 9

Where do Extrapyramidal Tracts originate

Answer 9

originate in brainstem, carrying motor fibres to spinal cord

Question 10

Function of Extrapyramidal Tracts

Answer 10

Responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion

Question 11

Functional Division of Extrapyramidal Tracts

Answer 11

Vestibulospinal
Reticulospinal
Rubrospinal
Tectospinal

Question 12

Vestibulospinal Tract

Answer 12

Arise from vestibular nuclei, receive input from organs of balance

Tracts convey balance info to spinal cord, where it remains ipsilateral

Question 13

Function of Vestibulospinal Tract

Answer 13

Control balance and posture by innervating the “anti-gravity” muscles (flexors of arm and extensors of leg) using LMN

Question 14

Reticulospinal Tract

Answer 14

Medial Reticulospinal -arises from pons and facilitates voluntary movement and increases muscle tone

Lateral Reticulospinal- arises from medulla and inhibits voluntary movement and decreases muscle tone.

Question 15

Rubrospinal Tract

Answer 15

originates in the red nucleus in the midbrain

Decussate and descend to Spinal Cord

Question 16

Function of Rubrospinal Tract

Answer 16

Fine control of hand movement

Question 17

Tectospinal Tract

Answer 17

originates at the superior colliculus of midbrain

Terminate at the cervical level of the spinal cord

Question 18

Function of Tectospinal

Answer 18

Control of head and neck movement

Question 19

What are motor neurons

Answer 19

Cells of the central nervous system transmitting signals to muscle cells or glands

Question 20

What are the two main types of motor neurons

Answer 20

Lower Motor Neurons

Upper Motor Neurons

Question 20

Upper Motor Neurons

Answer 20

Originate in the cerebral cortex and travel down the brainstem or spinal cord

Use glutamate as a neurotransmitter

Question 21

Lower Motor Neurons

Answer 21

Begin in the spinal cord and their terminal extend all the way to the muscle fibers and tendons

Use acetylcholine as their neurotransmitter

Question 22

Classification of Lower Motor Neurons

Answer 22

Alpha Motor Neurons - innervate extrafusal muscle fibers of SKELETAL muscles (cause muscle contraction)

Gamma Motor Neurons - innervate intrafusal muscle fibers of a specialised sensory organ ( respond to stretch of the muscle spindle)

Question 23

Where do lower motor neurons such as Alpha receive input from

Answer 23

- muscle spindles (provide sensory info from muscles ) -cerebral cortex (initiate voluntary movement) -interneurons in the spinal cord (largest input, cause excitation or inhibition) -upper motor neurons (use corticobulbar, corticospinal, and rubrospinal tract to send input to Alpha LMN)

Question 24

Reflex

Answer 24

involuntary movement in response to stimulus. Automatic response, does not need conscious thought. Thought to occur in a reflex arc

Question 25

Reflex Arc

Answer 25

Act on impulse before it reaches the brain. When a muscle is unexpectedly stretches it contracts to keep its length Muscle Spindles send a sensory signal into the spinal cord, which synapses directly onto a motor neuron, without signaling the brain first

Question 26

What is a monosynaptic reflex

Answer 26

very quick corrective action

Question 27

Other types of reflexes

Answer 27

Visual Light Reflex Corneal Reflex Gag Reflex Biceps Reflex Triceps Reflex Quadriceps

Question 28

Motor Cortex

Answer 28

region of the frontal lobe involved in planning, control and execution of voluntary movements Can be divided into -primary motor cortex -premotor cortex -supplementary motor area

Question 29

Primary Motor Cortex

Answer 29

Initiating Motor Movements Neurons are arranged topographically Represented using homonculus (look at diagram)

Question 30

Pathway of Primary Motor Cortex

Answer 30

Contains large neurons known as Pyramidal Neurons, primary output cells of the motor cortex Axons of these cells leave the motor cortex carrying info about desired movement and enter one of the pyramidal tracts These neurons can also connect with ALPHA LMN to innervate skeletal muscles

Question 31

Premotor Cortex

Answer 31

Involved in planning and executing motor movements Contains mirror neurons for motor learning

Question 32

Supplementary Motor area

Answer 32

Execution of sequences of movement , motor skills and motor control

Question 33

Damage at the level of the Spinal Cord

Answer 33

Paraplegic Quadriplegic

Question 34

Damage at the level of the Motor Cortex

Answer 34

Hemiplegia Hemiparesis (paritial weakness)

Question 35

Damage to Association Motor Areas

Answer 35

Apraxia

Question 36

Apraxia

Answer 36

The loss of ability to execute or carry out skilled movement and gestures , despite having the physical ability and desire to do so Cause - stroke in premotor or parietal cortex

Question 37

Aphasia Vs Apraxia

Answer 37

Aphasia - difficulty to understand or use words in and of themselves (speak, read or write) Apraxia - difficulty initiating and performing the movements needed to make speech

Question 38

Upper Motor Neuron Syndrome

Answer 38

damage to the descending UPN pathways

Question 39

Symptoms of Upper Motor Neuron Syndrome

Answer 39

Weakness Decreased Motor Control Altered Muscle Tone Decreased endurance Spasticity and Clonus

Question 40

Causes of Upper Motor Neuron Syndrome

Answer 40

Motor areas in brain or spinal cord are damaged or failed to develop normally Spinal Cord injury Cerebral Palsy MS Stroke TBI

Question 41

Lower Motor Neuron Syndrome

Answer 41

symptoms that arise from damage to the lower motor neurons of the brainstem and spinal cord

Question 42

Symptoms of LMN Syndrome

Answer 42

paralysis paresis areflexia (loss of reflexes) loss of muscle tone atrophy muscles involved may exhibit fibrillations and fasciculationsC

Question 43

Causes of LMN Syndrome

Answer 43

trauma or compression of peripheral nerves carpal tunnel viruses selectively attack ventral horn

Question 44

Facial nerve Weakness

Answer 44

look at page in notes

Question 45

Extrapyramidal Symptoms

Answer 45

Movement Dysfunction - Dystonia ( involuntary muscle spasms) -Akathisia (motor restlessness) Parkinsons (rigidity, tremor, bradykinesia, tremor)

Question 46

Causes of Extrapyramidal Symptoms

Answer 46

Medication - antipsychotic drugs (dopamine blockade) Non Medication -brain damage -meningitis