bio module 8

Partial seizures

(in cortical area of brain) - No loss of consciousness; unilateral; may progress as "Jacksonian March" along one side of body - May be sensory - sees lights, colors, tastes, smells, sensations - May be psychomotor - definite purposeful motor action (chewing, swallowing, blinking) OR purposeless (nonsense actions, may be violent antisocial) - No memory of activities

Encephalitis (p. 395-396)

- Brain inflammation; usually viral, but like meningitis, also may be bacterial, rickettsia, parasitic, or fungi origin - Fever, headache, intracranial pressure, may have signs of mumps; ataxia, coma, stupor, convulsions - May be carried my an arthropod (mosquito = ARBO virus; =ARthropod BOrne); St. Louis (SLE), Eastern Equine (EEE), West Nile (WNE)

Grand Mal seizures

- Convulsive; some genetic predisposition - Begins with an "aura" which may be sensory or emotional (dizzy, smell, taste, sensations, feelings) - Collapse & loss of consciousness follows; back arches, muscles tense, jaw clenches, loss of voluntary control (salivation, urination, defecation); 5-30 minute duration - Watch for hypoxia, do not restrain except to protect from injury - No memory of event; counseling & education important - Usually well controlled with medication; medication and treatments may change triggers with age or health status

Multiple Sclerosis (p. 397 - 398)

- Due to demyelination of central nervous system; autoimmune etiology - Without myelin, nervous transmissions are interrupted or "scrambled" due to loss of "insulation" between axons; 'crosstalking' among axons - Usually onset 20 - 50 years; more females afflicted; course of disease is intermittent and unpredictable - Episodes vary in area of body effected, intensity, duration; different nerves effected at different episodes - Initial attacks recede so no treatment sought; symptoms may mimic other diseases - Each episode leaves more scarring and damage which is irreparable - Long-term effects; constipation, urinary problems, spastic muscles; cumulative; incurable - Treat with corticosteroids, immunosuppressant, laxatives, and prevention of urinary infections

Epilepsy (p. 354-356)

- Electrochemical abnormality; very complex & unpredictable; abnormal EEG activity indicative - Seizures often triggered by an event (lights, sounds, emotions, hypoglycemia) - Seizures originate from epileptogenic focus in brain (area of brain sensitive to stimulation) - Types of Seizures Partial (in cortical area of brain) - No loss of consciousness; unilateral; may progress as "Jacksonian March" along one side of body - May be sensory - sees lights, colors, tastes, smells, sensations - May be psychomotor - definite purposeful motor action (chewing, swallowing, blinking) OR purposeless (nonsense actions, may be violent antisocial) - No memory of activities General Seizures (in subcortical areas of brain) - Loss of consciousness; bilateral Two types of General seizures: Petit Mal - momentary disturbance of cognitive function; staring episodes, blinking, nodding of head, dropping things, rolling eyes - Seizures very short; no falling - If have petit mal as child perhaps Grand Mal later Grand Mal - Convulsive; some genetic predisposition - Begins with an "aura" which may be sensory or emotional (dizzy, smell, taste, sensations, feelings) - Collapse & loss of consciousness follows; back arches, muscles tense, jaw clenches, loss of voluntary control (salivation, urination, defecation); 5-30 minute duration - Watch for hypoxia, do not restrain except to protect from injury - No memory of event; counseling & education important - Usually well controlled with medication; medication and treatments may change triggers with age or health status

General Seizures (in subcortical areas of brain)

- Loss of consciousness; bilateral Two types of General seizures: Petit Mal - momentary disturbance of cognitive function; staring episodes, blinking, nodding of head, dropping things, rolling eyes - Seizures very short; no falling - If have petit mal as child perhaps Grand Mal later Grand Mal - Convulsive; some genetic predisposition - Begins with an "aura" which may be sensory or emotional (dizzy, smell, taste, sensations, feelings) - Collapse & loss of consciousness follows; back arches, muscles tense, jaw clenches, loss of voluntary control (salivation, urination, defecation); 5-30 minute duration - Watch for hypoxia, do not restrain except to protect from injury - No memory of event; counseling & education important - Usually well controlled with medication; medication and treatments may change triggers with age or health status

Parkinson Disease (p. 371 - 372)

- More common in elderly, but may be seen with influenza - Disorder of basal ganglia of brain; Loss of neurons in nigrostriatal pathways; = loss of dopaminergic (dopamine secreting) neurons - Dopaminergic synapses are inhibitory; Acetylcholine (Ach) are excitatory therefore loss of inhibition of motor activation - Problems with start/ stopping movements; tremors at rest; overall decrease in muscle use; peculiar gait; rigid muscles; cannot flex a limb; mask-like face with wide-eyed stare - Treat with levo - dopa ("left-handed" molecule; only one which passes blood-brain barrier)

Understand how a Resting Potential is established and maintained (pp. 21 - 22)

- Three factors contribute to the establishment and maintenance of a Resting Potential; 1) Differential concentrations of cations (+) across the nerve membrane (K+, Na+, Ca++) 2) Differential permeability of nerve membrane to certain ions (open to K+ & practically impermeable to Na+) 3) Active transport of cations in-and-out of nerve cell (3 Na+ out & 2 K+ in; aka Na+/ K+ 'pump'); is an electrogenic process to maintain gradients - More K+ inside cell than outside therefore K+ moves out of cell (down conc. gradient) removing (+) charges from inside of cell - Removal of (+) from the inside of the cell creates a (-) charge inside cell - More Na+ outside than inside, but Na+ cannot enter cell (membrane impermeable); cannot compensate for K+ loss - Anions ((-), mostly proteins) remain inside (too big to move through membrane); help maintain osmotic stability - Thus, K+ exits cell (carrying their (+) charge) until osmotic pressure equals (-) electric charge resisting K+ exiting (=outside +; inside -) - As a result, inside the membrane becomes more (-) compared to outside = Resting Potential (RP) (K+ most responsible for creating RP) - Since membrane is "leaky" to Na+ (some 'sneaky sodiums' enter cell), the Na+/ K+ "pump" (p. 18-19) helps to maintain RP (not establish RP) - If K+ concentration gradient across membrane is lost, RP no longer exists, therefore no Action Potential is possible - If there is no resting Potential there can be no Action Potential (and thus no nerve signals for senses or motor)

Meningitis (p. 394)

- Usually bacterial or viral infection of meninges (covering of CNS), but may be from any inflammatory stimulus - Usually follows upper respiratory infection in infants & children - Infection spreads while laying-down along eustachian tube to middle ear or nasal to meninges along cerebrospinal fluid routes - May have sudden onset; high fever, stiff neck, pain with eye movement; signs of intracranial pressure (vomiting, bulging or tense fontanelles in infants, sudden increase in head circumference)

Spinal Poliomyelitis

- affects skeletal system - causes limb paralysis and deformation - Muscles are not stimulated so muscles atrophy and may become fibrotic - Remember, nerves generally do not regenerate easily, if at all

Herpes Zoster

- aka Shingles - Viral infection of root ganglia (p. 1054) - Causes paresthesia & pain and vesicular eruptions of specific areas innervated by infected spinal nerves

Petit Mal seizures

- momentary disturbance of cognitive function; staring episodes, blinking, nodding of head, dropping things, rolling eyes - Seizures very short; no falling - If have petit mal as child perhaps Grand Mal later

Neural Syphilis

- occurs when primary infection is not treated and bacterial infection moves into nervous system (Treponema pallidum)

Rabies

- viral infection of central nervous system - fatal; vaccination series used to treat

Three factors contribute to the establishment and maintenance of a Resting Potential;

1) Differential concentrations of cations (+) across the nerve membrane (K+, Na+, Ca++) 2) Differential permeability of nerve membrane to certain ions (open to K+ & practically impermeable to Na+) 3) Active transport of cations in-and-out of nerve cell (3 Na+ out & 2 K+ in; aka Na+/ K+ 'pump'); is an electrogenic process to maintain gradients

Three types of Poliomyelitis:

1) Non - paralytic - may appear like a cold 2) Bulbar - affects the brainstem and respiratory centers; difficulty in swallowing, difficult to breathe (must be assisted = "iron lung") 3) Spinal - affects skeletal system - causes limb paralysis and deformation - Muscles are not stimulated so muscles atrophy and may become fibrotic - Remember, nerves generally do not regenerate easily, if at all

Describe three ways an action potential may be stimulated in an excitable tissue. How do neurotransmitters work to stimulate an action potential?

1) mechanical - pinch, prick, crush; 2) electrical - (-) charge evokes an action potential (See above); 3) chemical - neurotransmitters bind to membrane receptors and change membrane polarity to either evoke or inhibit action potentials

Define action potential.

A brief, local, transient reversal of membrane potential

What is thought to be the cause of epilepsy?

A giant post-synaptic discharge from the central nervous system from the epileptogenic focus

What electrical polarity charge applied to the outside surface of a nerve membrane would operate to evoke (= produce; stimulate) an action potential? (Remember what happens with the membrane to bring an axon to threshold voltage.)

A negative (-) polarity applied to the outside of the axon would depolarize the membrane enough to reach threshold. This works because the (-) charge would make the outer membrane more similar in charge to the inner membrane, which actually is depolarizing the membrane.

Understand the basics of an Action Potential (AP)

A rapid, local reversal of membrane surface polarity - Nerve membrane depolarizes slightly as AP approaches (depolarization = move towards zero); (point 2 on Fig. 1) - Reaches threshold voltage (threshold must be reached to start AP, then AP goes "all-the-way" = total depolarization aka 'all-or-nothing'); (point 3 on Fig. 1) - When threshold is reached, Na+ channels open ('activation' gates on Fig. 2; they are "voltage-gated" = sensitive to voltage changes to open & close) - When Na+ channels open, Na+ ions are allowed to move into nerve cell; this reverses polarity at that spot on membrane (point 4 on Fig. 1) - When membrane potential reaches + 30 mV, Na+ inactivation gates (on Fig. 2) close, halting polarity change (point 5 on Fig. 1) - K+ channels then open so K+ rapidly exits cell causing rapid repolarization (= movement away from 0) thus preparing membrane for another AP (point 6 on Fig. 1) - Na+ channels 'reset' during repolarization by activation gates closing and inactivation gates opening (see Fig. 2) - K+ channels close slowly so membrane may hyperpolarize (=move lower than RP) until RP is re-established (point 7 Fig. 1) - The Action Potential "signal" is the local depolarization of the membrane that moves along the axon - The diagrams illustrate the relationship between AP course over time and actions of Na+ and K+ channels - Calcium ions reduce nerve membrane permeability to Na+; therefore if there is low Ca++ in the extracellular fluid, Na+ may cross nerve the membrane more easily - Therefore with hypocalcemia threshold is now closer to Resting Potential, and an AP is more easily stimulated - This allows spontaneous AP leading to tetany & laryngeal spasms leading to possible suffocation (which is inconsistent with the continuation of life processes...) - Some local anesthetics will move nerve threshold away from resting (towards zero), making it more difficult to generate an AP (nerve must depolarize more to reach threshold thus blocking AP); cocaine, Novocain, tetracaine - Cold also will slow-down nerve activity thus providing some anesthesia - AP may be stimulated by mechanical stimulation of the nerve; crush, pinch, prick; also by electrical, chemical - Neurotransmitters carry AP across synapses by increasing synaptic membrane permeability to Na+ - There are many kinds of neurotransmitters; acetylcholine, dopamine, epinephrine, norepinephrine, tryptophan, serotonin - Many hormones or cytokines (immune chemicals) may act as neurotransmitters

Calcium ions A)Help control the membrane threshold voltage. B)Reduce axon permeability to Na+. C)Increase axon permeability to Na+. D)Are responsible for axon repolarization.

A,B Calcium ions: Help control the membrane threshold voltage, Reduce axon permeability to Na+.

Parkinson Disease A)Causes the loss of inhibition of excitatory motor signals. B)Causes the loss of stimulation of excitatory motor signals. C)May be treated by levo-dopa. D)Results from the loss of dopaminergic neurons in the brain.

A,C,D Parkinson Disease: Causes the loss of inhibition of excitatory motor signals, May be treated by levo-dopa, Results from the loss of dopaminergic neurons in the brain.

Nerve membrane hyperpolarization after an action potential A)Is mostly due to the slow-closing of K+ channels. B)Is mostly due to the slow-closing of Na+ channels. C)Makes it more difficult to evoke another action potential. D)Is the movement of membrane potential voltage below normal resting potential voltage.

A,C,D Nerve membrane hyperpolarization after an action potential: Is mostly due to the slow-closing of K+ channels, Makes it more difficult to evoke another action potential, Is the movement of membrane potential voltage below normal resting potential voltage.

Define absolute neural refractory period in terms of membrane channel activity. Explain why (in terms of membrane channels) another action potential cannot be evoked while the nerve is repolarizing immediately after the peak of an action potential.

Absolute refractory period is the time when no other action potentials may be carried in the membrane. This is because the inactivation gates of Na+ channels are closed, so there can be no Na+ ion movement into the cell. If Na+ cannot enter the cell, there can be no action potential.

A sodium channel in a nerve membrane A)Opens and closes quickly. B)Activation gate opens when the membrane reaches threshold voltage. C)'Resets' when the membrane reaches resting potential . D)Inactivation gate closes when the membrane reaches ~+30 mV.

All of the above A sodium channel in a nerve membrane: Opens and closes quickly, Activation gate opens when the membrane reaches threshold voltage, 'Resets' when the membrane reaches resting potential, Inactivation gate closes when the membrane reaches ~+30 mV.

____ remain inside; help maintain ____

Anions ((-), mostly proteins) remain inside (too big to move through membrane); help maintain osmotic stability

How may nerve threshold be manipulated (=changed relative to resting potential) to produce anesthesia?

Anything that will move threshold away from resting potential (towards zero) will make it harder to depolarize the membrane enough to reach threshold =no action potential = no signal = no pain sensation.

As a result, inside the membrane becomes more ___ compared to outside

As a result, inside the membrane becomes more (-) compared to outside = Resting Potential (RP) (K+ most responsible for creating RP)

Encephalitis A)Is an inflammation of the meninges. B)May be spread by arthropods. C)May show the signs of mumps. D)Usually follows an upper respiratory infection.

B,C Encephalitis: May be spread by arthropods, May show the signs of mumps.

General epileptic seizures A)Originate in the brain cortex. B)May be very brief. C)May be 10 minutes in duration. D)Produce a loss of consciousness.

B,C,D General epileptic seizures: May be very brief, May be 10 minutes in duration, Produce a loss of consciousness.

Rabies A)Is caused by a bacterium. B)Infects the neuromuscular junction. C) Infects the central nervous system. D)Is caused by a virus.

B,C,D Rabies: Infects the neuromuscular junction, Infects the central nervous system, Is caused by a virus.

What does calcium do to an axon to influence sodium movement across the membrane? B)

Ca++ reduce nerve permeability to Na+

Calcium ions reduce nerve membrane permeability to ___; therefore if there is low ___ in the extracellular fluid, ___ may cross nerve the membrane more easily

Calcium ions reduce nerve membrane permeability to Na+; therefore if there is low Ca++ in the extracellular fluid, Na+ may cross nerve the membrane more easily

Cold also will slow-down nerve activity thus providing some _____

Cold also will slow-down nerve activity thus providing some anesthesia

There are 3 basics for the establishment of a resting potential (RP) in an axon. Name each one and describe what is happening in the axon to establish and maintain RP.

Differential concentrations of cations (+) across the nerve membrane (K+, Na+, Ca++) 2) Differential permeability of nerve membrane to certain ions (open to K+ & practically impermeable to Na+) K+ moves out of cell down concentration gradient; Na+ cannot move into the cell down its conc. gradient because the membrane is 'impermeable' to Na+; thus the inside of membrane becomes (-) relative to outside (+) 3) Active transport of cations in-and-out of nerve cell (3 Na+ out & 2 K+ in; aka Na+/K+ 'pump'); Some Na+ 'sneaks' in across the membrane so the 'pump' removes those Na+; also, the pump is an electrogenic process (more (+) moving out of cell than into the cell creates an electrical gradient) thus the Na+/K+ pump maintains K+ and Na+ gradients and the resting potential.

Explain why is it so difficult to diagnose MS?

It is difficult to diagnose because the symptoms mimic other neuromuscular disorders, they are intermittent, and may occur in various parts of the body for each attack.

K+ channels close ____ so membrane may ____ until ___ is re-established

K+ channels close slowly so membrane may hyperpolarize (=move lower than RP) until RP is re-established (point 7 Fig. 1)

K+ channels then open so ___ rapidly exits cell causing rapid ___

K+ channels then open so K+ rapidly exits cell causing rapid repolarization (= movement away from 0) thus preparing membrane for another AP (point 6 on Fig. 1)

____exits cell (carrying their ___ charge) until _____ equals ___ electric charge resisting ___ exiting

K+ exits cell (carrying their (+) charge) until osmotic pressure equals (-) electric charge resisting K+ exiting (=outside +; inside -)

Explain how the treatment for Parkinson Disease operates.

Levo dopa helps replace the missing dopamine because it is the isomer of dopamine that is able to cross the Blood Brain Barrier.

Explain why (in terms of neurophysiology and anatomy) MS produces its typical signs and symptoms.

Loss of the myelin insulation allows nervous signals to move across between axons or to be interrupted or scrambled. This causes the intermittent and diverse signs and symptoms because different nerves are involved with each attack.

How could low calcium be a problem (relative to nerve function)?

Low Ca++ would move threshold closer to resting potential making it easier to reach threshold, which is when Na+ channel activation gates open, thus invoking an action potential. Thus, low Ca++ allows spontaneous action potentials, stimulating uncontrolled and possibly constant muscle contractions.

Define hyperpolarization.

Membrane potential below normal resting potential

Differentiate between meningitis and encephalitis by first describing their etiology, pathogenesis, and signs & symptoms, and then explicitly stating differences between them.

Meningitis - Caused by bacterial or viral infection of meninges (membranes covering the brain & spinal cord), usually after upper respiratory infection in children with the infection migrating from oropharynx or middle/inner ear into meninges. Symptoms are sudden onset with high fever, pain when moving eyes, stiff neck, signs of intracranial pressure. Encephalitis - Is an inflammation of brain itself most often from virus but may be other pathogen that may be carried by a blood-sucking arthropod vector to transmit the virus (ARBO = ARthropodBOrne). There may be signs of mumps, with associated motor and cognitive impairment (ataxia, convulsions, coma, stupor), with the speed of onset variable.

More ___ inside cell than outside therefore ___ moves out of cell (down conc. gradient) removing ____ charges from inside of cell

More K+ inside cell than outside therefore K+ moves out of cell (down conc. gradient) removing (+) charges from inside of cell

More ___ outside than inside, but ___ cannot enter cell (membrane impermeable); cannot compensate for ___ loss

More Na+ outside than inside, but Na+ cannot enter cell (membrane impermeable); cannot compensate for K+ loss

What is underlying cause of multiple sclerosis?

Multiple sclerosis is an autoimmune attack on myelin surrounding axons in the CNS.

Describe 2 main physical manifestations of multiple sclerosis.

Muscle spasticity, urinary & bowel problems, pain, loss of limb function.

Na+ channels 'reset' during ____ by activation gates ____ and inactivation gates ____

Na+ channels 'reset' during repolarization by activation gates closing and inactivation gates opening (see Fig. 2)

Nerve membrane ____ slightly as ___ approaches

Nerve membrane depolarizes slightly as AP approaches (depolarization = move towards zero);

Neurotransmitters carry ____ across synapses by increasing synaptic membrane permeability to ___

Neurotransmitters carry AP across synapses by increasing synaptic membrane permeability to Na+

Explain the anatomical & neurophysiological basis for the signs and symptoms of Parkinson Disease. Explain (in terms of neurotransmitters) why the main signs of Parkinson Disease are produced.

Parkinson results from a loss of dopaminergic neurons (inhibitory) in the motor control areas of brain which removes the inhibition of excitatory motor stimulation (from acetylcholine); This impairs control of start/stop movements creating tremors in the extremities and eventually muscle rigidity in limbs, back, and face because mainly signals to contract muscles are being transmitted with little or no inhibition from dopamine.

Types of Seizures

Partial (in cortical area of brain) - No loss of consciousness; unilateral; may progress as "Jacksonian March" along one side of body - May be sensory - sees lights, colors, tastes, smells, sensations - May be psychomotor - definite purposeful motor action (chewing, swallowing, blinking) OR purposeless (nonsense actions, may be violent antisocial) - No memory of activities General Seizures (in subcortical areas of brain) - Loss of consciousness; bilateral Two types of General seizures: Petit Mal - momentary disturbance of cognitive function; staring episodes, blinking, nodding of head, dropping things, rolling eyes - Seizures very short; no falling - If have petit mal as child perhaps Grand Mal later Grand Mal - Convulsive; some genetic predisposition - Begins with an "aura" which may be sensory or emotional (dizzy, smell, taste, sensations, feelings) - Collapse & loss of consciousness follows; back arches, muscles tense, jaw clenches, loss of voluntary control (salivation, urination, defecation); 5-30 minute duration - Watch for hypoxia, do not restrain except to protect from injury - No memory of event; counseling & education important - Usually well controlled with medication; medication and treatments may change triggers with age or health status

Differentiate between a) partial and b) general seizures by describing at least three (show as 1), 2), 3) ) characteristics of each (partial and general)

Partial - a1) Cortical origin; a2) no loss of consciousness; a3) unilateral General - b1) Subcortical origin; b2) loss of consciousness; b3) bilateral

Differentiate between Petit and Grand Mal seizures.

Petit appears as just a slight momentary disturbance of cognitive function such as dropping an item, where grand mal is convulsive

Briefly outline the sequence of events (in terms of ion movements) involved with the propagation and course of an action potential in an axon.

Please see notes for details: - Depolarization of the membrane to threshold level; - Activation gate on Na+ channels open; - Na+ ions enter cell rapidly thereby depolarizing the membrane to +30 mV which is when inactivation gates on Na+ channels close and K+ channels open; - Na+ stops moving in and K+ moves out rapidly thereby repolarizing membrane; - As membrane potential approaches threshold, some of the Na+ channels 'reset' (activation gate closes and inactivation gate opens) and Na+ channels are again available to conduct another action potential; - K+ channels close slowly so membrane slightly hyperpolarizes before returning to resting potential

What are the three kinds of poliomyelitis and what physical problems do each type of polio cause? What is the etiological agent for polio?

Polio is a viral infection of the CNS of three types: spinal (limb paralysis), Bulbar (respiratory and swallowing impairment), and non-paralytic (appears as a normal viral infection).

What ion is most responsible for establishing a resting potential?

Potassium

Name the ion most responsible for repolarization after an action potential, and why that is so.

Potassium ions moving out of the cell through their voltage-gated channels (which open ~+30 mV) repolarize the membrane because each K+ carried a (+) charge out of the cell, making the inside negative relative to the outside.

If K+ concentration gradient across membrane is lost

RP no longer exists, therefore no Action Potential is possible

Removal of ___ from the inside of the cell creates a ___ charge inside cell

Removal of (+) from the inside of the cell creates a (-) charge inside cell

Since membrane is "leaky" to ___, the Na+/ K+ "pump" (p. 18-19) helps to maintain ____

Since membrane is "leaky" to Na+ (some 'sneaky sodiums' enter cell), the Na+/ K+ "pump" (p. 18-19) helps to maintain RP (not establish RP)

Name the ion most involved with depolarization during an action potential.

Sodium

The number of ___ ions moved out of the cell by the sodium/potassium 'pump' is ___, while the number of ___ ions moved into the cell by the sodium/potassium 'pump' is ___

Sodium/Na+, 3, potassium/K+, 2 The number of Na+ ions moved out of the cell by the sodium/potassium 'pump' is 3, while the number of K+ ions moved into the cell by the sodium/potassium 'pump' is 2

Some local anesthetics will move nerve threshold ____ resting, making it more difficult to generate an ___

Some local anesthetics will move nerve threshold away from resting (towards zero), making it more difficult to generate an AP (nerve must depolarize more to reach threshold thus blocking AP); cocaine, Novocain, tetracaine

The Action Potential "signal" is the local ____ of the membrane that moves along the axon

The Action Potential "signal" is the local depolarization of the membrane that moves along the axon

What process helps maintain a resting potential? Explain how that mechanism helps to maintain the resting potential.

The Na+/K+ pump moves these ions against their gradients to help maintain gradients of these ions across the membrane. The Na+/K+ pump also helps maintain resting potential by generating an electrical gradient (potential) across the membrane (moving more (+) out than pulling (+) in makes the inside more (-) compared to the outside).

Explain why this happens in terms of membrane channels and ion movement.

The activation gates on Na+ channels open when the membrane polarity moves closer to zero (=depolarizes) and reaches threshold. Na+ then moves into the cell thereby evoking an action potential.

Explain why (in terms of ion movements) that ion is most responsible to establishing a resting potential.

The exit of positively-charged K+ ions out of the cell down the K+ gradient removes (+) charges because each K+ carries a (+) charge. Removing (+) charges from the inside of the cell makes the inner membrane (-) charged compared to the outside of the membrane.

Define nerve threshold.

The membrane potential where activation gates on Na+ channels open

What does the Na+ /K+ pump do regarding action potential?

The pump moves Na+ out of the cell and K+ into the cell against their respective gradients. This removes Na+ that have been accumulating on the inner membrane as a result of action potentials. This helps to maintain concentration gradients of Na+ 7 K+ across the membrane.

Threshold must be reached to start ___

Threshold must be reached to start AP, then AP goes "all-the-way" = total depolarization aka 'all-or-nothing'); (point 3 on Fig. 1)

When Na+ channels open, ___ ions are allowed to move into nerve cell; this reverses polarity at that spot on ____

When Na+ channels open, Na+ ions are allowed to move into nerve cell; this reverses polarity at that spot on membrane (point 4 on Fig. 1)

When membrane potential reaches ___, ___ inactivation gates ____

When membrane potential reaches + 30 mV, Na+ inactivation gates (on Fig. 2) close, halting polarity change (point 5 on Fig. 1)

When threshold is reached, ___ channels open

When threshold is reached, Na+ channels open ('activation' gates on Fig. 2; they are "voltage-gated" = sensitive to voltage changes to open & close)

With hypocalcemia threshold is now closer to ____, and an ___ is more easily stimulated

With hypocalcemia threshold is now closer to Resting Potential, and an AP is more easily stimulated

kinds of neurotransmitters

acetylcholine, dopamine, epinephrine, norepinephrine, tryptophan, serotonin

Bulbar Poliomyelitis

affects the brainstem and respiratory centers; difficulty in swallowing, difficult to breathe (must be assisted = "iron lung")

Poliomyelitis

aka Infantile Paralysis - Viral; used to be major neurological problem but now mostly stopped by vaccination programs: Salk - 1955 killed virus; Sabin - 1958 attenuated oral vaccination Three types: 1) Non - paralytic - may appear like a cold 2) Bulbar - affects the brainstem and respiratory centers; difficulty in swallowing, difficult to breathe (must be assisted = "iron lung") 3) Spinal - affects skeletal system - causes limb paralysis and deformation - Muscles are not stimulated so muscles atrophy and may become fibrotic - Remember, nerves generally do not regenerate easily, if at all - Polio that has been in remission for decades may return when elderly - Weakening of immune system allows virus that had been 'hiding' in nervous system to re-emerge

A rapid, local reversal of membrane surface polarity

basics of an Action Potential (AP)

Resting potential is a balance across the axon membrane between ___ forces moving ions out of the cell and ____ forces operating to keep ions in the cell.

ionic/diffusion/osmotic, electric/electrical/electromotive Resting potential is a balance across the axon membrane between ionic forces moving ions out of the cell and electric forces operating to keep ions in the cell.

Non - paralytic Poliomyelitis

may appear like a cold

AP may be stimulated by

mechanical stimulation of the nerve; crush, pinch, prick; also by electrical, chemical

Many hormones or cytokines (immune chemicals) may act as

neurotransmitters

The ___ ion is most responsible for producing an action potential while the ___ ion is most responsible for establishing the resting potential.

sodium/Na+, potassium/k+ The sodium ion is most responsible for producing an action potential while the potassium ion is most responsible for establishing the resting potential.

This allows spontaneous AP leading to

tetany & laryngeal spasms leading to possible suffocation (which is inconsistent with the continuation of life processes...)

If there is no resting Potential

there can be no Action Potential (and thus no nerve signals for senses or motor)