Neurology 101 – Flashcards
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describe the basic anatomy of the human nervous system
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explain the basic physiology of the human nervous system
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define the types of neurons
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describe the basic anatomy of a neuron
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explain the basic physiology of each identified neuron component
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explain the cellular physiology of an action potential
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explain synaptic neurotransmission
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describe a neural circuit
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the human nervous system consists of 2 systems
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central NS and peripheral NS
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what is the CNS comprised of?
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brain and spinal cord
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what is the main function of the CNS?
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body's "control center", integrates information and coordinates activities
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what are the two divisions of the peripheral nervous system?
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somatic and autonomic
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what is the main function of the PNS?
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connects the body (eg organs, extremities) to the CNS
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what is the main function of the somatic nervous system?
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voluntary control of skeletal muscles
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what is the main function of the autonomic nervous system?
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regulates involuntary and visceral function (eg heart rate, respiration, digestion)
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what NS is divided into sympathetic and parasympathetic pathways?
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autonomic NS
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the ANS is divided into what two pathways?
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sympathetic and parasympathetic
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how do the sympathetic and parasympathetic nervous systems function?
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compliment each other, and work in conjunction to maintain homeostasis
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what functions are generally mediated by the sympathetic nervous system?
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sympatho-adrenal response (fight-or-flight)
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what functions are generally mediated by the parasympathetic nervous system?
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"rest and digest" or "feed and breed" i.e. salivation, lacrimation, urination, digestion, defecation
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where do sympathetic neurons begin?
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thoracic or lumbar spine
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where do parasympathetic neurons begin?
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brainstem or sacral spine
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what is the basic component of the NS
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neurons
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what do neurons do?
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process and transmit nerve impulses via electrical and chemical signals
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what are the three main types of neurons (based upon function)?
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sensory, motor, interneurons
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what is the function of sensory neurons?
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relay information to the brain concerning both internal and external environment
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what is the function of motor neurons? 3 main causes
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carries nerve impulses away from the CNS to effectors. This causes muscle contraction, behavior mediation, and stimulation of glands and organs
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what is the function of interneurons?
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transmits signals from one area of the brain to another
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what are the 3 parts of a typical neuron?
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soma, dendrites, axon
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what is the soma?
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central "cell body" part of the neuron, contains the nucleus
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what are dendrites?
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branched projections of the soma that function to receive inputs from other cells
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what is the axon?
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carries nerve impulses away from the soma (ie transports info from the soma to the target cells)
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how many axons per soma?
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one, but axons can branch extensively
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what is the axon hillock?
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where the axon emerges from the soma
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where in the neuron has the highest density of voltage-dependent sodium channels?
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at the axon hillock
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what is the most excitable part of the neuron? why?
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the axon hillock; because it has the highest density of voltage-dependent sodium channels
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what is the axon terminal?
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point at which the axon makes synaptic contact with target cells
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what is the function of myelin?
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increases nerve impulse conduction velocity (electrical impulse/action potential)
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conduction velocity is faster in which kind of neurons: myelinated or unmyelinated?
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myelinated is faster
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what is myelin?
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insulating sheath composed of glial cells
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what are glial cells in the CNS?
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oligodendrocytes
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what are glial cells in the PNS?
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schwann cells
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what are the gaps in myelin sheath called?
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Nodes of Ranvier
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what is the purpose of nodes of ranvier?
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allows for salutatory conduction (ie electrical impulse/ AP "jumps" from node to node
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true or false: all neurons are polarized
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true
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why are all neurons polarized?
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to maintain a voltage difference across the cell membrane
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what is the membrane potential?
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the voltage difference across the cell membrane
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how is membrane potential maintained?
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sodium-potassium ATPase pumps and ion channels
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what is the ion exchange that occurs with the Na/K ATPase pump? net charge?
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3 Na out/2 K in Net: negative intracellular charge
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what is resting membrane potential?
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- 70 mV
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what are the 6 stages of an action potential within a single neuron?
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1. resting 2. stimulus 3. depolarization 4. repolarization 5. hyperpolarization 6. refractory period
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what are the neuron membrane channels doing when the neuron is resting?
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ion channels closed; Na/K-ATPase actively maintains resting potential of -70 mV
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what are the neuron membrane channels doing when the neuron is depolarizing?
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1. voltage-dependent Na channels open 2. rapid influx of Na (via [ ] gradient) 3. membrane potential increases
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what is the approx. membrane potential during depolarization?
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30 - 40 mV (net positive intracellular)
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why is there an influx of Na when the voltage-dependent Na channels open during depolarization?
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Na moves down its concentration gradient, INTO the neuron
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during resting phase, is there a positive or negative net charge intracellularly?
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negative (around - 70 mV)
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during depolarization phase, is there a positive or negative net charge intracellularly?
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positive (around 30-40 mV)
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during repolarization phase, is there a positive or negative net charge intracellularly?
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positive
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during hyperpolarization phase, is there a positive or negative net charge intracellularly?
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negative
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during refractory phase, is there a positive or negative net charge intracellularly?
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negative
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what are the neuron membrane channels doing when the neuron is repolarizing?
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1. when membrane potential reaches 30-40 mV, K channels open 2. K diffuses out of the neuron (efflux) 3. Na channels close, trapping Na inside
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what are the neuron membrane channels doing when the neuron is hyperpolarizing?
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1. K channels close slowly, allowing excess K to leave the neuron 2. membrane potential falls below resting
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what are the neuron membrane channels doing when the neuron is in refractory period?
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1. Na/K ATPase pump works to re-establish resting potential by pumping K in and Na out 2. until resting potential is achieved, neuron cannot generate another AP
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why can't another AP be generated when the neuron is in the refractory period?
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because the potential is below resting potential; assures that an AP only travels in one direction
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what happens when the AP reaches the axon terminal?
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synaptic neurotransmission
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what is the primary means by which neurons communicate with target cells?
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synaptic neurotransmission
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which NTs are synthesized in the presynaptic region of the axon terminal?
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classical: serotonin, dopamine, glutamate
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what is the "classic" process of synaptic transmission?
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1. NTs synthesized in the presynaptic region of the axon terminal 2. NTs are stored in vesicles 3. NTs released into the synaptic cleft secondary to an AP reaching the axon terminal 4. NTs bind to receptors on the post synaptic cell 5. NT-modulated function in post synaptic cells
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what are the two major subtypes of NT receptors?
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ionotrophic and metabotrophic
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what occurs when a NT binds to an ionotrophic receptor?
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NT engagement results in the direct opening of ion channels
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what occurs when a NT binds to a metabotrophic receptor?
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NT interacts with G proteins, stimulating production of secondary messengers; activate protein kinases to indirectly result in opening and closing of ion channels
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which pathway is faster: ionotrophic or metabotrophic?
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ionotrophic is MUCH faster < 1 mSec
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what is the speed at which metabotrophic pathway of neurotransmission occurs?
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seconds to minutes
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what is the speed at which ionotrophic pathway of neurotransmission occurs?
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< 1 mSec
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what are 4 diseases that results secondary to NT dysfunction?
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epilepsy, Parkinson's, myasthenia gravis, mood disorders
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what is the neuronal circuit's function?
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entity of interconnected neurons that utilizes feedback mechanisms to regulate its own activity
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what two types of neurons are involved in the neural circuit?
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excitatory and inhibitory neurons
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what steps occur with neuronal excitation?
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1. AP reaches presynaptic axon terminal 2. excitatory NT released into the synapse 3. excitatory NT binds to ionotrophic and metabotrophic postsynaptic receptors 4. Ionotrophic receptor activation allows the influx of sodium and calcium cations into the postsynaptic cell 5. post synaptic neuron membrane potential increases to threshold and generates an excitatory postsynaptic potential
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what is the most prominent excitatory NT?
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glutamate
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What occurs when excitatory ionotrophic receptor activation occurs?
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influx of sodium and calcium cations into the postsynaptic cell
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what steps occur with neuronal inhibition?
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1. AP reaches presynaptic axon terminal 2. inhibitory NT released into the synapse 3. inhibitory NT binds to ionotrophic and metabotrophic postsynaptic receptors 4. Postsynaptic receptor activation allows for chloride influx and/or potassium efflux 5.post synaptic neuron membrane potential decreases, decreasing the probability of the postsynaptic neuron to complete an AP
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what is the most prominent inhibitory NT?
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GABA (glycine is another)
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What occurs when inhibitory ionotrophic and metabotrophic receptor activation occurs?
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chloride influx; potassium efflux; hyperpolarization
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How many cranial nerves are there?
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12
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what CN deficit causes facial asymmetry?
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7
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what CN deficit causes hearing loss?
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8
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what CN deficits cause difficulty speaking?
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9, 10, 12
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what CNs are grouped together to assess eye function?
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3, 4, 6
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what is the diagnostic test that is useful in evaluating (but not required for diagnosis) or epilepsy? This procedure records the electrical activity of the brain
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EEG
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what diagnostic procedure is used to assess muscle dysfunction secondary to nerve injury?
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EMG
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This expensive imaging procedure is used to radio-label glucose to assess brain function
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PET or SPECT
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what are the 6 risk factors for contrast-induced nephropathy?
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age > 80; SCr >2; DM; dehydration; nephrotoxic agents; high-doses of contrast media
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what are 3 differences between CT and MRI
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MRI is more expensive; no radiation exposure with MRI; improved anatomic detail with MRI
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what is the primary means by which a neuron maintains resting membrane potential?
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Na/K ATPase pump
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what is the AP stage with closed Na channels, opening K channels, and marked K efflux?
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repolarization
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what is the AP stage characterized by rapid influx of sodium?
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depolarization
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what is the AP stage characterized by a membrane potential lower than resting potential, secondary to slow closing K channels?
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hyperpolarization
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what is the primary means of nerve impulse propagation at the axon terminal?
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synaptic transmission
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which type of neuron transports nerve impulses away from the CNS to effectors (e.g. organs, muscles)
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motor efferent
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which type of neuron transports information to the brain concerning internal and external stimuli?
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sensory afferent
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what is the insulation that functions to increase nerve impulse conduction velocity?
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myelin sheath
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what are the gaps in myelin sheath that allows for salutatory conduction?
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nodes of ranvier
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what are the 3 main parts of a neuron?
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soma, dendrites, axon
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what are 3 ways that NTs are removed from the synaptic cleft?
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re-uptake; enzymatic break-down; diffusion away
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what is the physiology of excitatory post-synaptic potential?
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Na and Ca influx
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what is the physiology of inhibitory post-synaptic potential?
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Cl influx and K efflux
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what portion of a neuro eval is specifically designed to access higher cortical function?
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MMSE, mini-mental status exam
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what MMSE score represents cognitive impairment?
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< 23
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what are the 6 components of s neurologic evaluation?
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MMSE; sensory; gait; reflexes; CN; motor function
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what part of a neuro eval would one note ataxia?
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gait
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what exam is used to assess sensory function and proprioception?
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romberg maneuver
