Brain and Spinal Control of Movement Flashcards
Describe the anatomy of the Neuron. Which structures are involved ?
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)
Which neural structures are part of Central nervous system vs Peripheral Nervous system?
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
Describe how information is carried from axon to synapses.
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)
Explain how graded potential can help cause action potential to be triggered.
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
Differentiate between what happens to action potential when their is an EPSP input vs Mixed Input
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.
aExplain what must occur for action potential to be triggered and why?
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)
What are the main stages of Action potential?
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
What factors influence AP conduct speed? What are the roles of myelin sheath and Nodes of Ranvier?
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.
What occurs in Multiple Sclerosis? What are the symptoms of this condition?
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)
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)?
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
Which nerves are affected by MS? What occurs with one’s Cerebral spinal fluid (CSF)?
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
What occurs in Guillan-Barre syndrome?
What are clinical features of this disorder?
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
Compare an contrast normal motor nerve vs nerves with Guillan-Barre syndrome
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
How does the immune system play a role in Guillain-Barré syndrome (GBS)> What are the six subtypes of GBS?
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
What are the main parts of the Human Nervous System? What structures are composed of them?
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
How many pairs of Cranial and Spinal nerves are there? Where is the Enteric Nervous System located?
12 pairs of Cranial nerves
31 pairs of Spinal nerves
Enteric nervous system is in walls of viscera
(more neurons in system than brain)
What are the names of the Cranial Nerves
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
How are the cranial nerves classified?
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
What is the spinal cord segment composed of?
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
Describe the development of the brain and spinal cord as you age.
-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
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
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)
What type of neurons are in the cervical enlargement? Lumbar enlargement?
Cervical enlargement: contains the neurons that Innervates the UPPER limbs
Lumbar enlargement: contains neurons that innervate LOWER limbs
What is the Conus medullaris? What surrounds this structure in adults vs children
Conus medullaris: the Tapering end of the spinal cord
The conus medullaris is surrounded by L1 in Adults and L2 in children
Where does the Adult spinal cord terminate? How does this differ for spinal cord in child?
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)
Where is the epidural space located?
The epidural space is between the vertebra and the dura mater
What happens in Epidural Anesthesia
Epidural Anesthesia: process of injecting anesthesia (or catheter) in the epidural space around spinal cord
(provides pain relief; sometimes used during labor)
What are all the structures of spinal cord?
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)
What systems determine motor control?
Motor Control
1)Skeletal motor
Pyramidal
-Glutamate
Extrapyramidal
-Glutamate
2) Autonomic nervous system
Sympathetic
-Norepinephrine
Parasympathetic
Acetylcholine (unconscious homeostatic actions)
What does the descending tracts compose of and what systems are part of those structures?
Descending Tracts:
-Upper motor tracts
Pyramidal system
Extrapyramidal tracts
-Lower motor tracts
What is the role of the autonomic nerve system? What are the two main parts of the system and their functions ?
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)
Distinguish between the neurotransmitters involves in sympathetic pathway vs parasympathetic pathway.
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.
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
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
What tracts are in the Motor and Descending (Efferent) pathways compared to the sensory and Ascnding pathways.
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
Describe how sensory and motor tracts are named
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
Discuss the sensation, first-order, second-order, third order, final destination and site of cross over for all the Asending (sensory tracts)
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
PIMARRY DESCENDING (MOTOR) PATHWAYS
REVIEW
What is the Corticospinal tract composed of?
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)
