Brain and Spinal Control of Movement

Question 1

Describe the anatomy of the Neuron. Which structures are involved ?

Answer 1

Neuron Anatomy;
-Dendrites
-Cell body
-initial segment (axon)/Axon hillock (generate AP’s that propagate along axon)
-Myelin
Oligodendrocytes- myelin in CNS
Multiple Sclerosis: caused by issue with amount of myelin (inflammatory reaction with oligodendrocytes)
Schwann Cells: myelin in PNS
-Guillain-Barre: cause by reduction/loss of Schwann cells (inflammatory reaction)
-Synapse/motor endplate (on periphery of muscles)

Question 2

Which neural structures are part of Central nervous system vs Peripheral Nervous system?

Answer 2

CNS: dendrites, Neuron cell body, axon hillock, myelin sheet, axon, node of ranvier, synapse, oligodendrocytes, initial segment of axon, nissil substance

PNS; collateral branch, motor endplates in skeletal muscle, Schwann cells

Question 3

Describe how information is carried from axon to synapses.

Answer 3

Axons carry information from cell body to the axon terminals
-Axon terminals communicate with their target cells at synapses

(synapses integrate for among neurons and help drive movement)

(individual neuron has about 10,000 connections)

Question 4

Explain how graded potential can help cause action potential to be triggered.

Answer 4

Integration of information
Within the Dendrite,
-graded potentials travel through the dendrite until they reach the trigger zone (initial segment)
- if they depolarize the membrane ABOVE threshold voltage about 55 mV in mammals), an action potential is triggered and travels down an axon

Question 5

Differentiate between what happens to action potential when their is an EPSP input vs Mixed Input

Answer 5

EPSP Input= Action Potential occurs
Mixed Input (IPSP + EPSP) = NO Action potential
-When you add IPSP (INHIBITORY) to EPSP, you will negate the excitatory part and not be able to reach higher zone, hence NO AP occurs.

Question 6

aExplain what must occur for action potential to be triggered and why?

Answer 6

Postsynaptic potentials (PSPs) are small
-An individual EPSP will NOT produce enough depolarization to trigger an action potential
-IPSPs will counteract the effect of EPSPs at the same neuron
SUMMATION: means the effect of many coincident IPSPs and EPSPs at one neuron (combined effect)
-if there is SUFFICIENT Depolarization at AXON HILLOCK, an action potential will be triggered.
(summation will determine whether AP is generated or not)

Question 7

What are the main stages of Action potential?

Answer 7

Action potential
1-2) EPSPs and IPSPS
-integrate voltage
3) Voltage reaches threshold
-AP (action potential) is generated
3-4) NA+ enters cell
-Depolarization (more positive)
5-6) K+ exits cell
-Repolarization (negative)
7-8) Overshoot and recovery

Question 8

What factors influence AP conduct speed? What are the roles of myelin sheath and Nodes of Ranvier?

Answer 8

The RESISTANCE of the membrane to current leak out of cell and the DIAMETER of axon determines the speed of AP conduction
-Large diameter axons provide a LOW resistance to current flow within the axon, and this in rerun, speeds up conducing

Myelin sheath: Which wraps around vertebrate axons PREVENTS current leak out of the cells. Acts like an Insulator; for example, plastic coating surrounding electric wires
Nodes of Ranvier: Portions of axons that lack the myelin sheath
High concentration of Na+ channels are found at these nodes.

Question 9

What occurs in Multiple Sclerosis? What are the symptoms of this condition?

Answer 9

Multiple Sclerosis - Demyelinating disease (losing myelin; oligodendrocytes)
-The loss of myelin in the nervous system SLOWS down the conduction of APs, MS patients complain of muscle weakness, fatigue, difficulty walking and loss of vision
(lose strength in muscles, movement)

Question 10

Describe what causes Multiple Sclerosis and clinical features that are present in the disease. How does it affects other areas of the brain? Which nerves are affected by MS? What occurs with one’s Cerebral spinal fluid (CSF)?

Answer 10

Multiple sclerosis (MS):
Myelin formed by Oligodendrocytes undergoes an inflammatory reaction that IMPAIRS or blocks impulse transmission in the CNS.
- MS is marked by the Presence of PLAQUES which are sharply demarcated areas of demyelination. MS plaques tend form in axons that course near surfaces of the lateral ventricles , in the floor of 4th ventricle, or near the pial surfaces of the brainstem or spinal cord.
-Multiple lesions appear over time, but the signs and symptoms may undergo exacerbation and remission; commonly two or more CNS sensory or motor neural systems are affected in separate attacks

Question 11

Which nerves are affected by MS? What occurs with one’s Cerebral spinal fluid (CSF)?

Answer 11

The only Cranial Nerve (CN) or spinal nerve affected by MS is the OPTIC nerve (CN II) because all of the myelin sheath of its axons are formed by oligodendrocytes. MS is the most common cause of Optic neuritis
-In patients with MS, CSF (cerebral spinal fluid) contains elevated gamma globulin, and T-lymphocytes

Question 12

What occurs in Guillan-Barre syndrome?
What are clinical features of this disorder?

Answer 12

Guillan-Barre syndrome: describes myelin formed by Schwann cells in the PNS that undergoes an acute inflammatory reaction following a respiratory or gastrointestinal illness. This reaction Imparis or blocks impulse transmission of axons in the PNS and results in polyneuropathy (malfunction of peripheral nerves)
-Motor axons are always affected, producing weakness in the limbs. Weakness of the cranial nerve innervated muscles, or respiratory muscles may be seen. Sensory deficits are mild or absent
Guillan-Barre syndrome is Immune-related

Question 13

Compare an contrast normal motor nerve vs nerves with Guillan-Barre syndrome

Answer 13

Normal motor nerve: normal structure, normal function
Guillan-barre Syndrome subtypes:
Acute inflammatory demyelinating polyneuropathy
-Antibody injures myelin membrane
Acute motor axonal neuropathy or actor motor and sensory axonal nueropathy
-antibody injures Axonal membranes

Question 14

How does the immune system play a role in Guillain-Barré syndrome (GBS)> What are the six subtypes of GBS?

Answer 14

GBS is as serous disorder that occurs when the body’s defense (immune) system mistakenly attacks part of the nerves system. This leads to nerve inflammation that causes nerve weakness
There are 6 different subtypes of GBS and they are:
1. Acute inflammatory demyelinating polyneuropathy
2. Miller Fischer Syndrome(visual ocular/motor)
3. Acute motor axonal neuropathy
4. Acute motor sensory axonal neuropathy
5. Acute panautomatic neuropathy
6. Bickerstaff’s brainstem encephalitis

Question 15

What are the main parts of the Human Nervous System? What structures are composed of them?

Answer 15

Central Nervous system (CNS)
-Brain
-Spinal cord
Peripheral Nervous System (PNS)
-Cranial Nerves and ganglia
-Spinal nerves and dorsal root ganglia
-Sympathetic and parasympathetic nerves and ganglia
-Enteric nervous system

Question 16

How many pairs of Cranial and Spinal nerves are there? Where is the Enteric Nervous System located?

Answer 16

12 pairs of Cranial nerves
31 pairs of Spinal nerves
Enteric nervous system is in walls of viscera
(more neurons in system than brain)

Question 17

What are the names of the Cranial Nerves

Answer 17

Names of the Cranial nerves (12)
I. Olfactory nerve
II. Optic Nerve
III. Oculomotor nerve
IV Trochlear nerve
V Trigeminal nerve
VI Abducent nerve
VII Facial nerve
VIII Vestibulocochelar nerve
IX Glossopharyngeal nerve
X Vagus nerve
XI Accessory nerve
XII Hypoglossal nerve

Question 18

How are the cranial nerves classified?

Answer 18

Classification of cranial nerves
Sensory cranial nerves: contain only Afferent (sensory) fibers
I. Olfactory nerve
II. Optic nerve
III. Vestibulocochlear nerve
Motor cranial nerves: contain only Efferent (motor) fibers
III. Oculomotor nerve
IV Trochlear nerve
VI Abducent nerve
XI Accessory nerve
XII Hypoglossal nerve
Mixed Nerves: Contain BOTH Sensory and Motor fibers.
V Trigeminal nerves
VII Facial nerve
IX Glossopharyngeal nerve
X Vagus nerve

Question 19

What is the spinal cord segment composed of?

Answer 19

Spinal cord segment:
-Pseudo-unipolar sensory neuron: that send info from sensory receptors to spinal(posterior root0 sensory ganglion
-Somatic multipolar motor neuron; will send info and stimulate effector organs and skeletal striated muscle
-Autonomic multipolar motor neurons will get info from presynaptic neuron and synapse within autonomic ganglion and regulate function of Glands, smooth (involuntary) muscle and modified cardiac muscle

Question 20

Describe the development of the brain and spinal cord as you age.

Answer 20

-Brain and Spine grow 3 times its size in the first year
-As an adult, you have the SAME Spinal cord as a newborn
-Spinal Nerves EXTEND as the spine grows

Question 21

What are the 5 regions that the spinal cord can be divided into. which one of the groins have only ONE pair of nerves? What are the components of the sacrum?
REVIEW

Answer 21

The spinal cord can be subvidivded into five regions:
cervial region, thoracic region, lumbar region, sacral region and coccygeal region
Coccygeal region (only has ONE pair of nerves)
Components of the sacrum:
-Sacral plexus, filum terminale
(sacrum has 5 segments, that include base and apex)

Question 22

What type of neurons are in the cervical enlargement? Lumbar enlargement?

Answer 22

Cervical enlargement: contains the neurons that Innervates the UPPER limbs

Lumbar enlargement: contains neurons that innervate LOWER limbs

Question 23

What is the Conus medullaris? What surrounds this structure in adults vs children

Answer 23

Conus medullaris: the Tapering end of the spinal cord
The conus medullaris is surrounded by L1 in Adults and L2 in children

Question 24

Where does the Adult spinal cord terminate? How does this differ for spinal cord in child?

Answer 24

The Adult spinal cord terminates at the level the First lumbar vertebra (L1)
In a developing child, the spinal cord can extend to the level of the Second lumbar vertebra (L2)

Question 25

Where is the epidural space located?

Answer 25

The epidural space is between the vertebra and the dura mater

Question 26

What happens in Epidural Anesthesia

Answer 26

Epidural Anesthesia: process of injecting anesthesia (or catheter) in the epidural space around spinal cord (provides pain relief; sometimes used during labor)

Question 27

What are all the structures of spinal cord?

Answer 27

Spinal Cord Dorsal (posterior) horn Intermediate zone Dorsal column Dorsal root Central canal Dorsal root ganglion ventral root ventral (anterior) horn Ventral column Ventral white commissure)

Question 28

What systems determine motor control?

Answer 28

Motor Control 1)Skeletal motor Pyramidal -Glutamate Extrapyramidal -Glutamate 2) Autonomic nervous system Sympathetic -Norepinephrine Parasympathetic Acetylcholine (unconscious homeostatic actions)

Question 29

What does the descending tracts compose of and what systems are part of those structures?

Answer 29

Descending Tracts: -Upper motor tracts Pyramidal system Extrapyramidal tracts -Lower motor tracts

Question 30

What is the role of the autonomic nerve system? What are the two main parts of the system and their functions ?

Answer 30

The autonomic nervous system directs All activities of the body that occur without a person's conscious control, such as breathing and food digestion. It has two parts 1) Sympathetic division: most active in times of stress - (Dilates the pupil, inhibits salivation, relaxes bronchi, accelerates heart, inhibits digestive activity, stimulates glucose release by liver, secretion of Epinephrine and Norepinephrein from kidney, relaxes bladder, contracts rectum) 2) Paraysympathetic division: controls maintenance activities and helps conserve the body's energy (Constricts pupil, stimulates salivation, inhibits heart, constricts bronchi, stimulate digestive activity and gallbladder, contracts the bladder, and relaxes rectum)

Question 31

Distinguish between the neurotransmitters involves in sympathetic pathway vs parasympathetic pathway.

Answer 31

Sympathetic pathway -Ach from the cholinergic preganglion neuron will bind to Nioctinic receptor one choligenric post ganglion neuron. This will cause NE (norepinephrine) to bind to Adrenergic receptor (alpha or beta) on target tissue Parasympathetic pathway: The AcH from cholinergic preganglionic neuron will bind to Nicotinic receptor of Cholinergic post-ganglionic neuro. AcH will ALSO bind to choligernic receptor (MUSCARINIC) on target tissue.

Question 32

What are the differences between the Pyramidal system and Extrapyramidal system. Compare the different features of phylogeny, function. pathways, effects of lesion, cortical fibers. subcritical centers/basal ganglia

Answer 32

Pyramidal system phylogeny: RECENT in acquisition, present ONLY in mammals and achieving its greatest development in man Function: Responsible for Non-postural, precise movements of SMALL muscles involved in SKILLFUL activity Pathways: connected DIRECTLY tot he lower motor neurons. Therefore impulses reach the LMNS, through a direct route Effects of lesion; NO increased muscle tone Cortical fibers; Arise predominantly in PRIMARY motor area (brodman'a area 4) Subcortical centers/basal ganglia: play NO role in pyramidal system Extrapyramidal system: Phylogeny: OLDER than pyramidal system (reptile brain type) -function: responsible for Gross postural (stereotyped) movements involving LARGE muscle groups Pathways: Connected INDIRECTLY (polysynaptic pathway) to Lower motor neurons. Therefore impulses reach the LMNS through a circuitous route Effects of lesion: Muscle tone INCREASED Cortical fibers: arise preodminantly in PREMOTOR area (brodmann's area 6) -Subcortical centers and basal ganglia: plays a KEY role in extrapyramidal system

Question 33

What tracts are in the Motor and Descending (Efferent) pathways compared to the sensory and Ascnding pathways.

Answer 33

Motor and Descending (Efferrent) pathways (red) -Pyramidal tracts -Anterior Corticopsinal tracts and Lateral corticopsinal tract Extrapyramidal tracts -Rubrospinal tract Reticulospinal tracts Olivospinal tract Vestiublospinal tract Sensory and Ascending (Afferent) pathways (blue) -Dorsal Column Medial Lamniscus System -Gracile fasiculus Cuneate fasiculus Spinocerebellar Tracts Posterior and anterior spinocerebeallar tracts Amterolateral system Lateral and Anterior spinothalamic tract Spino-olivary fibers

Question 34

Describe how sensory and motor tracts are named

Answer 34

Naming tracts -if the tract name beings with "spino" (as in spinocerebellar), the tract is a SENSORY tract delivering information from the spinal cord to the cerebellum -if the tract name ENDS with "Spinal (as in vestibulospinal), the tract is a MOTOR tract that delivers information from the vestibular apparatus (in this case) to the spinal cord

Question 35

Discuss the sensation, first-order, second-order, third order, final destination and site of cross over for all the Asending (sensory tracts)

Answer 35

Principle Ascending (Sensory) tracts: 1) Fasiculus gracilis Sensations; proprioreception, fine touch, pressure and vibration from levels inferior to T4 First Order: Dorsal root ganglia of lower body; axons enter CNS in dorsal roots and ascend within fasiciulus gracilis Second Order: Nucleus gracilis of Medulla oblongata; axons cross over before entering medial lemniscus Third-Order: Ventral posterolateral nucleus of thalamus Final Destination: Primary sensory cortex on side opposite stimulus Site of cross over: axons of second-order neurons before joining medial lemniscus 2) Fasiculus Cuneatus: Senstaions; proprioception, fine touch, pressure and virabiton from levels at or superior to T5; First-order: Dorsal root ganglia of Upper body; Second order: Nucleus cuneatus of medulla oblongata axons cross over before entering medial meniscus; Final destination; primary sensory cortex on opposite side of stimulus Site of cross over: axons of second-order neurons cross over before joining medial lemniscus. Third order: ventral postlateroal nucleus of thalamus Final destination and site of cross over: same as fasiculus gracious Spinothalmaic tract 3) Lateral spinothalmaic tract Sensations: Pain and temperature sensations First Order: Dorsal root ganglia; axons enter CNS in dorsal roots and enter posterior gray horn Second-Order: in posterior gray horn; axons enter lateral spinothalmaic tract Third-Order: ventral posltateral nucleus of thalamus Final Destination: primary sensory cortex on opposite Side stimulus Site of Crossover: Axons of second-order neurons at level of entry 4) Anterior spinothlamic tracts sensation: Crude touch and pressure sensations First Order: Dorsal root ganglia, axons enter CNS in dorsal roots, enter posterior gray horn Second Order: in posterior gray horn, axons enter Anterior spinothlamic tract on opposite side Third-Order: ventral psoteriolateral nucleus of thalamus Final Destination:Primary sensory cortex on side opposite of stimulus Site of Crossover: axons of second order neurons. a level of entry Spinocerebellar tracts 5) Posterior spinocerebellar tracts Sensation: proprioreception First Order: Dorsal root ganglia; axons enter CNS in dorsal roots Second Order:* In posterior gray horn; axons enter posterior spinocerebellar tract on SAME SIDE Third Order; NOT present Final Destination : Cerebellar cortex on side of stimulus site of crossover: NONE 6) Anterior spinocerebellar tracts Sensation: proprioreception First Order: Dorsal root ganglia; axons enter CNS in dorsal roots Second Order: In SAME spinal segment: axons enter anterior spinocererebellar tract on same or opposite side Third order; NOT present Final destination: cerebellar cortex, primarily on side of nucleus Site of cross over: axons of most-second-order neurons cross before entering tract and then cross again within cerebellum

Question 36

PIMARRY DESCENDING (MOTOR) PATHWAYS

Answer 36

REVIEW

Question 37

What is the Corticospinal tract composed of?

Answer 37

Corticospinal tracts -Large pyramidal cells of the lamina pyramidal internal (layer 5) of the cerebral cortex, are the first order neurons of the corticospinal tract Precentral gyrus (Brodmann's area 4 and 6) -Primay motor cortex -premotor cortex Postcentral gyrus (Brodmann's areas 3, 1, 2, 5 & 7) -Somatosensory Cortex Fibers arising from the postcentral gyrus do NOT contribute to motor regulation (gives sense of body position)

Question 38

Describe the pathway of corticalspinal tracts

Answer 38

Corticalspinal tracts -Axons descend via the corona RADIATA, then descend to the INTERNAL Capsule. the internal capsule: white matter structure, located between the thalamus and the basal ganglia Then from the internal capsule, it goes to CEREBRAL PEDUNCLE of the midbrain, the pons, and then into medulla (where it decussates; CROSS OVER)

Question 39

What is the function of the internal capsule?

Answer 39

internal capsule separates the caudate nucleus, thalamus, and lenticular nucleus ( putamen and globes pallidus) All the fibers (from ascending and descending tracts) converge here

Question 40

Describe the clinical findings in Internal Capsular Stroke. What were they signs and symptoms? QWhat occurred in mixed sensorimotor stroke?

Answer 40

Signs and symptoms (of Internal Capsular Stroke) : -Weakness of the face, arm and or leg (pure motor stroke) -Known as one of the classic types of lacunar infarcts, a pure motor stroke is the result of an infarct in internal capsule -Pure motor stroke caused by infarct in internal capsule is the most common Lacunar syndrome. Upper motor neuron signs: -Hyperreflexia, Babinksi sign, Hoffman present (involuntary flex movement of thumb) , clonus, spasticity babinksi sign (test whether foot is stimulated, causing big toe to extend upward) Mixed sensorimotor stroke: Since both motor and sensory fibers are carried in the internal capsule, a stroke to the posterior limb of the internal capsule (where motor fibers for the arm, trunk and legs, and sensory fibers are located) can lead to contralateral weakness and contralateral sensory loss

Question 41

What makes up the lateral corticospinal tract vs the anterior corticospinal tract?

Answer 41

At the medulla, -75 to 90% of the fibers will decussate to the contralateral side via the Pyramidal decussation and make up the LATERAL Corticospinal Tract -5 to 15% of fibers that do NOT decussate within pyramidal decussation make up the ANTERIOR corticospinal tract

Question 42

When does the Anterior corticalspinal tract decussate?

Answer 42

Anterior corticospinal tract will decussate in the Spinal Cord just BEFORE they synapse with lower motor neurons.

Question 43

Explain how the different regions of the brain and spinal cord relate to pathway of cortical spinal tract REVIEW

Answer 43

Primary motor cortex wil make connection to pre central gyrus (motor cortex) which will then descend to posterior limb of internal capsule. Cervical part of spinal cord relates to pyramidal decussation that occurs in medulla -Thoracic relates to lateral corticospinal tract (where there is a upper motor neuron) -lumbar and sacral relate to anterior horn and lower motor neuron that innervates skeletal muscle pathway of corticospinal tract: pre central gyrus (motor cortex) descends to posterior limb of internal capsule, and then pyramidal decussation occurs in medulla, which goes to lateral corticospinal tract into upper motor neuron and then Lower motor neuron that wil innervate skeletal muscle.

Question 44

What are the functions of Corticospinal Tracts?

Answer 44

Functions of the Corticospinal Tracts 1) Initiation of fine, discrete, skilled voluntary movements 2) Lateral Corticospinal tract--> Control distal limbs (ex: fingers for skilled movement) 3) Anterior Corticospnial tract --> Control Posture and axial & proximal muscles for walking 4) Effect on stretch reflex: facilitate muscle tone through gamma motor neuron 5) Fibers that originate from parietal lobe are for sensory-motor integration

Question 45

What are the main Extrapyramidal tracts in the Medial pathway ?

Answer 45

Extrapyramidal Tracts: Medial Pathway -Vestiublospinal tract -Rubrospinal tract -Reticulospinal tract -Tectospinal tract

Question 46

Describe the origin, function and path of the Vestibulospinal tract

Answer 46

Vestibulospinal tract: Origin: Vestibular nuclei -level of the pons -processing afferent signals from the semicircular canal system of the inner ear. Vestibulochochelar nerve (VIII) Function: Upright Posture Maintenance -INHIBIT flexor and promote Extensor, muscle activity to maintain balance Path: Form the vestibulospinal tract (ipsilateral side) enter the anterior funiculus Synapse on the ventral grey horn cells

Question 47

Describe the origin, function and path of the Rubrospinal tract

Answer 47

Rubrospinal tract: Origin: The red nucleus -Level of the Superior colliculus -Continuous regulation by corticorubral and cerebellorubral pathway Function: Modulation of flexor muscle tone -indirectly carries regulatory signals form the cerebrum and cerebellum to INHBIT Extensor and PROMOTE FLEXOR , muscle activity Path: -Decussate at the level of the red nucleus (also descend through medial lemniscus ) -Form the rubrospinal tract (contralateral side) -Enter the lateral funiculus -Integrate with the reflex cells of the anterior grey horn

Question 48

wwwwWhat is the origin , function and path for Reticulospinal tracts?

Answer 48

Reticulospinal tracts Origin: The reticular formation -set of interconnected nuclei dispersed throughout the brainstem -Pontine reticular formation -Medullary reticular formation Function: One of the most important extrapyramidal tracts for controlling activity of the LOWER motor neurons -Locomotion and postural control -Muscle tone and relax activity - Analgesic (pain Modulation) pathways -Respiration and other autonomic pathways Path: -Medial Reticulospinal Tract (pontine) -descends ipsilaterally in the anterior funiculus -Alpha and gamma motor neurons of the Extensor muscles - Lateral Reticulospinal tracts (medullary) -Descends bilaterally in the lateral funiculus -Motor neurons anterior grey horn

Question 49

What is the origin, function and Path for Tectospnial tract?

Answer 49

Tectospinal tract Origin: The superior colliculus (midbrain tectum) -level of the midbrain -Processing visual information from the retina and cortical visual association areas Functions: Reflex responses to visual stimuli -Jumping away from an object that unexpectedly moves or is perceived as hazardous at the same time -Postural movements of the head in response to visual and auditory stimuli (ex: BOO! HA! remarks) Path: -Decussate at the level of the TECTUM -Form the Tectospinal tract (contralateral side) -Medial Longitudinal Fasiculus into the Ventral funiculus of the spinal cord -Integrate with the reflex cells of the anterior grey horn

Question 50

What are the three major sensory tracts?

Answer 50

There are three major sensory tracts : - The posterior/Dorsal column tract -The Spinothalamic tract -The spinocerebellar tract

Question 51

What functions are associated with Dorsal column, spinothalmaic and Spinocerebellar tract?

Answer 51

Dorsal column tract -Deep touch pressure -Proprioception Vibration sensation Spionthalmaic tract Lateral tracts Pain Temperature Spinocerebrellar -Dorsolateral tracts Posture Coordination

Question 52

What are components of Ascending pathways? differentiate between the Fine touch and Fast pain fibers?

Answer 52

Ascending pathways Fine touch -primary sensory neurons from receptor to MEDULLA -Secondary sensory neurons always cross over medulla--> thalamus -Tertiary sensory neurons --> somatosensory cortex (post central gyrus) Fast Pain (Alpha delta) -Primary sensory neurons from receptor to SPINAL Cord (Laminae II and V of the Dorsal Horn) -Secondary Sensory neurons always CROSS OVER in spinal cord--THALAMUS (ascend on contralateral side) -Tertiary sensory neurons--> Somatosensory cortex (post central gyrus)

Question 53

Explain the path of the 1st order neuron in Dorsal column tract. Where does it start, ascend and end?

Answer 53

Dorsal Column Tract 1st Order Neuron: -**Arise from Sensory receptors of the body - **Fibers enter the IPSILATERAL/Posterior column **(SAME SIDE) -Ascends to the medulla oblongata (does NOT synapse and end here like Spinothalmaic tract) -Enter medulla oblongata -**ENDS in the Gracile and Cuneate Nucleus***

Question 54

What is the path of the second order neuron of dorsal column tract? Where does it start, ascend and end?

Answer 54

2nd Order Neuron: **Origin: Gracile and cuneate nucleus of the medulla oblongata** -Fibers DECUSSATE (Cross) to the CONTRALATERAL (OPPOSITE) side -Ascend through the brain stem -as a flattened bundle - **Medial Lemniscus ** - **Termination: the Ventral Posteroloateral Nucleus of the thalamus (VPN) ***

Question 55

Describe the path of the 3rd order neuron in the Dorsal Column Tract

Answer 55

3rd Order Neuron **Origin: THALAMUS -Thalamocortical fibers pass through the internal capsule -Medial part of the posterior limb of internal capsule -Termination: Layer IV of the Post Central Gyrus -Sensory cortex of the cerebrum -Posterior (behind) central sulcus -Same homunculus arrangement -More sensitive areas in body have a greater representation

Question 56

Describe the clinical anatomy of what occurs in Brown-sequard syndrome> What parts are effected on contralateral vs isplatreral side. What happens if there is a lesion above or below sensory decussation? What are effects of cortical and internal capsule legions?

Answer 56

Clinical Anatomy Brown-Sequard syndrome: rare neurological condition characterized by lesion in spinal cord resulting in weakness (hemiparaplegia) or paralysis in one side of the body and loss of sensation (hemianesthesis) on opposite side of body - **Hemisection lesion (lose 1/2 of the spinal cord) -Contralateral side: Loss of pain, temperature, light touch, pressure Ipsilateral side: loss of other sensations (Deep touch, vibration, motor function) -Lesion above sensory decussation: all sensations OPPOSITE side of the body are lost -Lesion below sensory decussation; sensations of SAME side of body are lost -Cortical Lesions: Sensory cortex of the cerebral hemispheres controls the opposite side of body -Contralateral: Affected area are usually limited; paralysis/parathesis is localized -Internal capsule lesions: All Ascending and Descending tracts are affected (Hemiplegia/hemiparathesis)

Question 57

Summarize the descending and tracts of the spinal cord

Answer 57

Descending tracts of the spinal cord: - lateral and ventral (anterior) Corticospinal tracts that deal with Voluntary, discrete, skilled motor activities -Lateral and Ventral (anterior)Reticulospinal tracts that provide Excitatory or Inhibitory Regulation of voluntary movements and reflexes. -Rubrospinal Tract promotes Flexor and Inhibit extensor muscle activity -Vestibulospinal tract Promotes Extensor and INHIBITS Flexor muscle activity. it also supports Balance and Posture -Tectospinal tracts facilitate Postural Movements arising from Visual stimuli -Although the Corticalspinal tract is a Descending pathway, it **TERMINATES on the** Cranial Nerve nuclei** (which are located in the midbrain and brain stem)

Question 58

Summarize the spinal Ascending tracts

Answer 58

Ascending the Ascending spinal tracts: -Lateral Spinothalmaic carries Pain and THERMAL stimuli -Ventral Spinothalamic is responsible for PRESSURE and CRUDE TOUCH sensations -Dorsal Column is the area of VIBRATION, sensation, PROPRIOCEPTION, and two point DISCRIMINATION (fine touch) -Spinocerebellar tracts (anterior and posterior divisions) conduct Unconscious stimuli for PROPRIOCEPTION in joints and muscles -Cuneocerebellar Carries the SAME information of Spinocerebellar tracts -other ascending tracts in the spinal cord that are discussed in more detail in other articles include -Spinotectal serves as an accessory pathway for Tactile, painful and thermal stimuli to reach the midbrain -Spinoreticular integrates stimuli from muscles and joints into the reticular formation -Spino-olivary- is an accessary pathway that carries additional information to the cerebellum.

Question 59

What is required for the voluntary contraction of skeletal muscle? REVIEW

Answer 59

Voluntary contraction of skeletal muscle requires an interaction of 2 neurons; An Upper Motor neuron (UMN) and a lower motor neuron (LMN) (if there is lesion in Upper motor neuron; ALS disorder; lesion in lower (alpha) motor neuron--> stroke)

Question 60

Where are Lower motor neurons distributed? Where are motor neurons that control flexors vs motor neurons controlling axial muscles

Answer 60

Distribution of Lower motor neurons in Ventral Horn -Motor neurons controlling the Flexors lie DORSAL to extensors -Motor neurons controlling Axial Muscles lie MEDIAL to distal muscles

Question 61

What are the inputs that go to Alpha Motor neurons?

Answer 61

Inputs to Alpha Motor neurons -Input from Spinal internerouns -Sensory input from muscle spindles (stretch receptors?) -Input from upper motor neurons in brain

Question 62

Where is the lower motor neuron located?

Answer 62

Lower motor neuron: located in the Ventral horn of spinal cord

Question 63

Differentiate between Motor unit and motor Neuron pool?

Answer 63

Motor Unit: Motor neuron and all the muscle fibers it innervates (alpha motor neurons create motor unit) -Motor neuron pool: ALL the Motor neurons that innervate a single muscle (allow for graded force , muscles to be activated, contract)

Question 64

Further explain and provide an example of a motor Unit?

Answer 64

Motor Unit Single motor neuron and muscle fibers it innervates eye muscles- 1:1 muscle/nerve ratio Hamstrings- 300:1 muscle/nerve ratio

Question 65

which neurons are response for graded control of contractions? How do they do so? REVIEW

Answer 65

Graded control of Muscle Contraction by Alpha Motor Neurons -varying the firing rate of motor neurons -Recruit additional synergistic motor units The Alpha motor neuron will record motor neuron activity and measure muscle contraction If actin potentials are increased, see a force generated if faster motor neurons are fired, see max amount of force generated

Question 66

What are the types of Muscles in a motor system?

Answer 66

Somatic Motor System Types of Muscles: -Smooth: digestive tract, arteries, related structures -Striated: Cardiac (heart) and Skeletal (bulk of body muscle mass)

Question 67

What is proprioception? Explain the different motor controls systems

Answer 67

Motor Control Systems Proprioreception: sense of self-movement, force, and body position -Muscle spindles detect changes in muscle length -Golgi tendon organs relay information abut the force of contraction -Joint angle receptors -Ruffini endings and Pacinian corpuscles -Respond to angle, direction and velocity of movement in a joint Skin receptors

Question 68

Describe the muscle fiber anatomy? what kind of fibers are muscle fibers made of? What is fascicle, endoymysium, epimysium, myofibril, perimysium,etc

Answer 68

muscle fiber: composed of extramural and intrafusal fibers -Epimysium surrounds whole muscle fiber -Perimysium surrounds a fascicle (bundles of fibers) -Endomysium: surrounds a myofibril

Question 69

What are the two types of muscle spindle fibers and how do you distinguish between them?

Answer 69

Two types of Muscle Spindle fibers: 1. Extrafusal fibers: -Force generating -Type of SLOW twitch fibers -Innervated by ALPHA and Beta Motor neurons 2. Intrafusal fibers: -Stretch and Speed detectors (of muscle contraction) -innervated by GAMMA and beta motor neurons -Proprioreception -group Ia annulospiral endings -group II flower spray ending

Question 70

Explain how the muscle spindle functions including the sensory feedback from muscle spindles REVIEW

Answer 70

Muscle spindle function -Sensory feedback from muscle spindles -Stretch receptor -When muscle is stretched, 1a, 2 Fires faster axons (this activates alpha motor neuron) . -causes muscle to contract (extrafusal fiber) and pool is released from spindle (la/2a stops firing) -Then activate gamma motor neurons an allow intrafusal fiber to contract

Question 71

Explain what occurs in the Myotatic Reflex and what drives it? Provide an example

Answer 71

The Myotatic Reflex -Stretch Reflex: Muscle pulled-->tendency to pull back . Feedback loop driven by Discharge rate of sensory axons: related to muscle length Monosynaptic circuit ex: Knee-jerk reflex

Question 72

What is the Reflex that is seen in a Knee jerk reflex? Describe the path

Answer 72

Reflex Arcs -In a Knee-jerk reflex arc, the sensory neuron directly connects the motor neuron in Spinal cord. -This is called a simple reflex arc Follow the sensory neuron from the spindle (receptor) to where it connects with the motor neuron in the spinal cord Follow the motor neuron to the muscle (effector)

Question 73

What are the steps that occur in the Myotatic Reflex? REVIEW

Answer 73

Myotatic reflex: describes the contraction of a muscle in response to its passive stretching (when muscle stretches, stretch reflex regulates length of muscle automatically by increasing contractility ) **Process: 1. Hit the elbow with Hammer causing stretch receptors to be activated and the tendon at the back of arm to stretch (Tendon stretch) This increase in muscle stretch activates muscle fiber 2 . La Afferent fiber will be activated and send information about stimulus to cell body in the spinal cord 3. The interneuron will carry inhibitory impulse to flexor neuron in Biceps. This INHIBITS the Biceps (Flexor) (antagonist will be inhibited) 4.The alpha motor neuron (excitatory impulses) will be carried to extensor neuron. 5. Triceps (extensor) will contract.

Question 74

Explain the roles of Golgi Tendon Organs

Answer 74

Golgi Tendon Organs -Provide information about the Force of contraction -Muscle tension receptor -Regulates muscle tension within optimal range -Reverse myotatic reflex function Causing the Stretched muscle to relax (lb axon on Golgi tendon organ synapsing to inhibitory inteneruon. Interneuron also synapse to AMN that will inhibit Alpha motor neuron ? )

Question 75

Differentiate between myotatic reflex and Inverse Myotatic reflex

Answer 75

Myotatic Reflex : Muscle spindle is activated by increase in muscle stretch Uses la fibers that stem from dorsal root ganglion in spinal cord. muscle stretch flex (causes stretched muscles (quadriceps) to CONTRACT) leg extensors (quads) will be activated and will contract while inhibitory interneuron will synapse with leg flexor muscles and inhibit the flexor muscles (hamstrings) Inverse Myotatic Reflex; Golgi tendon organ will be activated by increase in muscle force lb fibers (sensory) stem from dorsal root ganglion in spinal cord and will synapse with inhibitory interneuron inverse muscle stretch reflex (causes activated muscle to relax) leg extensor muscles are activated and stretched from tap of hammer -inhibitory interneuron wil synapse with LMN and lb fiber This causes leg extensor muscles (quadriceps) that were initially stretched to relax. (inverse myotatic reflex: aka inverse strtech reflex or Golgi tendon reflex).

Question 76

What is considered the Correct Pathway? How does it work?

Answer 76

The Correct pathway -The "Hot Stove" Reflex -The correct connection between the sensory neuron carrying the message from the receptor and the motor neuron carrying the message to effector is the work of interneurons of central nervous system. -Making the right connection is mediated by INTEGRATION -INTERNEURONS provide integration of sensation into appropriate motor action

Question 77

Explain what occurs in the Hot Stove Reflex

Answer 77

Hot Stove Reflex: 1. Touch a hot object, activating the pain receptors in the skin. The pain stimulus will be carried along the dendrite of Afferent neuron in spinal cord, to reach the cell body of afferent neuron, all the way to axon of afferent neuron. The axon of afferent neuron will synapse with cell body of interneuron. The interneuron will also synapse with cell body of interneuron to integrate sensory information with motor neuron. The cell body of efferent neuron will send signal along axon of efferent neuron, causing muscle to contract and withdraw part being stimulated (remove hand from hot stove)

Question 78

What occurs in Conscious-Stimulus Response? REVIEW

Answer 78

Conscious Stimulus-Response -We react to stimuli in basically the same way as a reflex. The integration just gets more complex -Complex behavior involves integration in the brain (Stimuli hits sensory receptor causing sensory input (afferent sensory neurons) to integrate through interneurons with motor (effernt )neurons to activate effector muscle. (brain and spinal cord--CNS (involves interneurons) PNS involves motor (efferent neurons) (reflex arc is building blocks of conscious stimulus response? )

Question 79

Explain how myelination influences development disorders.

Answer 79

Normal development of the infant and young child: 2 months after birth: child can lift its head 4 months: child can sits with support 9 months: stand with support 10 months; child crawls 14 months: stand without support 15 months: child will walk *** without any or too little myelination, children will experience development disorders later on as they age. For example if infant does not raise head by 4 months: that is a sign that a child will have an issue myelin production

Question 80

Explain how Gaits can be used to diagnose disorders. Provide examples

Answer 80

Gaits: pattern of walking Examples: -Sensory Ataxic ; slappage tabetic associated with posterior column disease -Hemiplegic; circumduction (affected side Is rigid and is swung around) associated with stroke -Scissors; eggs cross alternately . spastic paralysis is associated with cerebral palsy -Cerebellar gait: staggering, drunken motor taxis (wide based reeling gait) associated with acute alcoholism, drug poisoning, general paresis or multiple sclerosis -Waddling gait: clumsy, weakness of lower extremities, associated with muscular dystrophy Steppage gait: foot drop (usually unilateral) is associated with LMNL (lower motor neuron), Deep personal nerve damage, L-4/L-5 nerve damage -Festination (propulsion) when you shuffling steps while leaning forward is associated with Parkinson's disease Limping is when have short step on bad side

Question 81

Describe the hierarchy of Movement and brain structures involved

Answer 81

Hierarchy of Movement -Simple reflexes Spinal cord -Sterotypical, repetitive movement (walking, swimming) -Basal ganglia/cerebellum -Specific goal-directed movement Cerebral cortex

Question 82

What is the most important UMN (upper motor Neuron ) system?

Answer 82

The Corticopsinal and Corticobulbar axons (that control motor movement)

Question 83

Different between what happens when there is a lesion above vs below red nucleus and how it affects movement of muscles

Answer 83

Lesion ABOVE red nucleus : results in DECORTICATE rigidity and UMN signs - **your arms are pulled in (knuckle to knuckle) on top of chest** *flexion of elbow and adduction of arm, and flexion of hands Lesion BELOW red nucleus: results in DECEREBATE rigidity and UMN signs - **your arms are flexed to side (knuckles apart) -protonation of forearm, *Extension of elbow and adduction of arm

Question 84

How does a muscle contract voluntarily? what is the orientation of UMN to LMN and LMN to the innervated muscle?

Answer 84

Voluntary contraction of skeletal muscle: 2 neurons: UMN + LMN Upper motor neuron and lower motor neuron -UMN cell body is CONTRALATERAL (on OPPOSITE side) to LMN; axons cross midline (axons cross at caudal medulla spinal cord junction ingrain stem) -LMN is IPSILATERAL (on SAME side) to innervated muscle

Question 85

What are clinical symptoms that occur in UMN lesions vs LMN lesions?

Answer 85

UMN have a net inhibitory effect on reflexes (act like brakes) -UMN lesion: Paresis (weakening of muscles) and Hyperactive reflexes -LMN lesion: paralysis and suppressed reflexes

Question 86

What kind of muscle rigidity occurs with Corticospinal lesion vs Lesion of midbrain or Lower ?

Answer 86

Lesion of the Extensor Biased UMN (Corticospinal Lesion) -causes Decorticated rigidity (arms pulled in on chest) Flex of arms (this can be caused from serious trauma, stroke, or alzheimer' s disease) Lesion of the Flexor Biased UMN (Lesion of the midbrain or lower) -Causes Decerebate Rigidity leading to arms extend to sides, extension of arm

Question 87

Explain what occurs in the Clinical grading of muscle strength and Muscle stretch reflexes

Answer 87

Clinical Grading of Muscle Strength: The grading of muscle strength varies from 0/5; where the patient is unable to generate contractions that produce movement) to 5/5; NORMAL strength; patient generates movement against full resistance) Clinical Grading of Muscle Stretch Reflexes: Muscle stretch reflexes are graded in patients from 0 (absence of muscle stretch reflexes) to 4 (hyperactive stretch reflexes with clonus) A grade of 2+ indicates normal, moderately brisk reflexes

Question 88

Differentiate between a normal plantar response vs Extensor planter respond (Babinski's sign)

Answer 88

A plantar reflex: reflex elicited when sole of the foot is stimulate with blunt tool **Normal Plantar respnose: Toes DOWN (Flexion) ** Extensor plantar response** (Babinski's sing) -Toes point UP, Fanning of other toes (dorsiflexion of big toe; point up)

Question 89

What are characteristics of Upper Motor Neuron Lesion vs Lower Motor Neuron Lesion?

Answer 89

Upper Motor Neuron Lesion: Spastic paralysis Hyperreflexia Babinski Sign present (toes point up, fan) -Increased muscle tone -muscle weakness -Paresis- weakness -Disuse atrophy of muscles -Decreased speed of voluntary movement -Large area of the body involved Lower Motor Neuron -Flaccid paralysis -Areflexia -NO Babinski - *Fasiculations -Decreased muscle tone -Atrophy of muscles -Loss of voluntary movments -Small area of body affected

Question 90

Discuss whether Spastic weakness and Flaccid paralysis is ispsilateral or contralateral and which motor neuron its located in

Answer 90

Upper Motor Neuron: **Spastic Weakness: is ether Contrlateral OR Ipsilateral and always BELOW the lesion Lower Motor neuron; ***Flaccid Paralysis is IPSILATERAL and At the Level of the lesion

Question 91

Distingusih between the signs of upper motor neuron vs Lower Motor Neuron lesions

Answer 91

signs of Upper Motor Neuron Lesions: -Weakness -NO atrophy (but mild atrophy may develop due to disuse) -NO Fasiculations -Increased Reflexes -Increased Tone (however with Acute upper motor neuron lesions; tone may be decreased) Lower Motor Neuron Lesions -Weakness -ATROPHY -Fasiculations -Decreased reflexes Decreased Tone

Question 91

Distingusih between the signs of upper motor neuron vs Lower Motor Neuron lesions

Answer 91

signs of Upper Motor Neuron Lesions: -Weakness -NO atrophy (but mild atrophy may develop due to disuse) -NO Fasiculations -Increased Reflexes -Increased Tone (however with Acute upper motor neuron lesions; tone may be decreased) Lower Motor Neuron Lesions -Weakness -ATROPHY -Fasiculations (muscle twitching) -Decreased reflexes Decreased Tone

Question 92

What are the main lesion motor pathways and how can you distinguish between the two?

Answer 92

Motor Pathway Lesions ; UMNL and LMNL Upper motor Neuron lesion -lesion of the brain and spinal cord (NOT including anterior horn) -Spastic paralysis -hyperactive DTR -Pathological Reflexes Clonus -Hypertonic Tone (increased) -NO reaction of Degeneration No atrophy or Fasciculations -NO superficial reflexes Lower Motor Neuron Lesion; -Flaccid paralyiss -Hypoactive/absent DTR -No pathological reflexes -NO clonus -Hypotonic Tone (decreased) -Reaction of Degeneration Atrophy Fasciculations -NO Superficial reflexes

Question 93

What are the conditions that occur from UMNL vs LMNL?

Answer 93

UMNL (upper motor neuron lesion); -Encephalitis -Multiple sclerosis -Cerebral Palsy -CVA (stroke) -Brain Tumor -ALS (Amyotrophic Lateral Sclerosis) Conditions from LMNL (lower motor neuron lesion) - Subluxation -Myasthenia Gravis -Disc protrusion -Polio Bells's palsy -ALS Amyotrophic Lateral Sclerosis )