lecture 2
What are the 4 classification of neurons?
1. unipolar= invertebrates
2. pseudounipolar= one projection that splits into 2 axons, no true dendrites (sensory neurons)
3. Bipolar = one axon one dendrite
4. multipolar= 1 axon and many dendrites
What are the classifications=
- sensory/ afferent
- motor/ efferent
- interneuronal
- convey information into the CNS
- transmit information from CNS to peripheral structures (muscles and glands)
- send information between neurons
What do local potentials do?
What do action potentials do?
action= transmit information over large distances (all or none)
What is neuroelectrophysiology
Where is the electrical signal generated
inside (intracellular) and outside (extracellular) the neuron there are charged ions
these ions move back and forth between the inside and outside of the neuron
it is generated at the axon hillock
multiple sclerosis
Etiology: autoimmune
Pathology: demyelination of CNS
Symptoms: variable bc the demyelination can occur in a variety of locations (sensory impaired/ atypical sensation, motor weakness, cranial nerves impaired vision, cognition infrequent or mild)
Prognosis: variable, no cure, avoid high temperature and excessive exertion
What are the stages of an action potential
1. resting membrane potential
2. threshold
3. depolarization
3. repolarization
4. hyperpolarization
5. returning to resting membrane potential
What happens at threshold and depolarization?
if threshold is reached, many voltage gated Na+ channels open and there is an influx of Na+ into the cell
- neuron becomes more positively charged inside the cell than outside the cell
What happens at repolarization?
the Na+ channels are closed, K+ Chanels open and K+ exits the cell
causes a reversal of the membrane potential
What happens at hyperpolarization?
continued efflux of K+ causes cell membrane to become even more negative than at rest. It is refractory.
-absolute refractory period= membrane unresponsive to stimuli
-relative refractory period= stimulus must be stronger than normal to elicit an AP
(this prevents backward propagation of action potential)
Guillain Barre
Etiology: autoimmune
Pathology: demyelination of PNS
Symptoms:
-motor= weakness, paresis/ paralysis
- sensory= atypical sensations, pain
- cranial nerves= motor CNs most affected
Prognosis: progressively worse 2-3 weeks then gradual improvement
What happens at returning to RMP?
membrane channels are all closed. Na+-K+ pump: actively moves Na+ out of the neuron and K+ back unto the neuron
What is saltatory conduction?
What is nodes of ranvier?
active opening of ion channels
nodes of ranview= small unmyelinated patches located on myelinated axons, new AP is generated at these nodes, makes AP faster
(AP appears to jump from node to node)
What does the central nervous system account for?
What does the peripheral nervous system account for?
CNS= Brain and spinal cord
PNS= Cranial nerves and spinal nerves
What is the sympathetic nervous system?
Sympathetic= fight or flight, activated during exercise, excitement, and emergencies
Myasthenia Gravis
Pathology: decreased number of functional muscle membrane
Symptoms:
- motor= weakness increases with muscle use
- sensory= not impacted
- cranian nerves= not impacted, but skeletal muscles innervated by Cns show fluctuating weakness
Prognosis: with medical treatment, >90% survival rate
Autonomic Dysreflexia
spinal cord injury above T6
- sympathetic neurons below the level of lesion are activated due to some noxious stimuli
- with lesions above T6 the SC is prevented from receiving signals from the brain that inhibit sympathetic activity
* sudden spike in blood pressure may be life threatening
What are the cranial nerves and what do they do?
I: olfactory= smell (sensory)
II: optic= vision
III: Oculomotor= eye movement
IV: Trochlear= eye movement
V: Trigeminal= chewing (motor and sensory)
VI: Abducens= eye movement
VII: Facial= facial expressions, move lips, tongue (sensory and motor)
VIII: Vestibulocochlear= hearing and head movement (sensory)
IX: Glossopharyngeal= tongue and pharynx and swallowing (sensory and motor)
X: Vagus= autonomic system (motor and sensory)
XI: Accessory= elevates shoulder and turns head
XII: Hypoglossal= innervates the intrinsic and extrinsic muscles of the tongue (motor)
Oculomotor nerve (CN 3) lesion
Diplopia double vision
Ptosis: drooping of the eyelids
Dysphagia
- difficulty swallowing
- can cause aspiration (food going down the wrong tube)
- continued aspiration can lead to pneumonia
trigeminal Neuralgia
Etiology: ?
Pathology: compression of the trigeminal nerve CN5
Symptoms:
- sensory= no loss, but severe, sharp, stabbing pain, begin and end abruptly
- motor = intact
Prognosis: variable
Dysarthria
- speech disorder resulting in poor articulation (slurred speech)
- no difficulty in understanding spoken language or ability to read and write
What is the parasympathetic?
Parasympathetic= rest and digest, energy conservation and storage
What is a neuromuscular junction?
It is where motor neurons synapse with muscle fibers. Voluntary and involuntary muscle movement, fast acting obligatory response
special
I hate this
Bell's palsy
Etiology: viral infection or immune disorder
Pathology: lesion to the facial nerve
Symptoms:
- sensory= unimpaired
- motor= unilateral paresis/ paralysis of the muscles supplied by the facial nerve
- autonomic= salivation and production of tears affected (severe cases)
Prognosis: the majority of people the muscles recover within 2 months depending on the severity of damage