Chapter 12: Neurophysiology
Synapses: - Synapses are the sites where nerve impulses are transmitted from a presynaptic cell (neuron) to a post synaptic cell (includes: __________). Synapses thus permit neurons to communicate with each other and effector cells. - Impulse transmission at synapse can occur _________ or _________. - Although electrical synapses are uncommon in mammals, they are present in the _________, _________, and ___________. Impulse transmission is much _______ across electrical synapses than across chemical synapses. - Chemical synapses are the most common mode of communication between two nerve cells. The presynaptic membrane releases one or more ________ into the synaptic cleft, located between the presynaptic membrane of the first cell and the postsynaptic membrane of the second cell. - The NT diffuses across the synaptic cleft to ___________ channel receptors on the postsynaptic membrane.
- (another neuron, muscle cells or cell of a gland) - electrically or chemically - brain stem, retina, and cerebral cortex/ faster - NTs - gated-ion
- ________: are large scale depolarizations of the inner surface of the nerve cell membrane in which there is a charge reversal from -70mV to +30mV (a total change of 100 mV). These act as ______ distance signals, the strength of which does NOT _______ with distance. Once initiated, they will affect the entire membrane. - In a motor neuron, such long distance signals are generated at the ________, and are propagated towards the axon terminals. At the axonal terminals, the APs cause the discharge of _____ molecules from the synaptic vesicles. - More channels = _______ stimulus.
- APs/ long/ decrease - axon hillock/ NT - stronger
- _____________: is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. Voluntary muscle action affected = paralysis. - Amyotrophic means __________. - Early symptoms of ALS often include increasing muscle weakness = lead to atrophy because the muscles are not receiving the messages from motor neurons. - ALS is _____% more common in males than females.
- Amyotrophic Lateral Sclerosis (ALS) or Low Gehrig's disease - no muscle nourishment - 20
Synaptic Delay: - A short delay occurs for _________ and _______ release, not in the diffusion across the synaptic cleft. Normally an AP can travel 7 cm in .5 seconds. - Where there are many synapses to cross, it will require increased time. - This is why ________, which only have a few synapses, are important for survival. - This is one of the factors responsible for _________. - Reducing the reaction time by constant use of chemical synapses is called _______.
- Ca+ influx and NT release - reflexes - reaction time - synaptic potentiation
Presynaptic Inhibition: - ______ release = inactivation of _______ channels - Less calcium enters = less ______ released - Reduced effect on postsynaptic membrane
- GABA = calcium - NT
Summarize the Electrical Polarity: - At rest; due to 3 factors: - 1. The unequal concentration of potassium ion and sodium ions at the cell's interior and exterior; interior has a higher concentration of ______, and exterior has a higher concentration of ______ (_______ charge inside and ______ charge outside). - 2. Differential permeability of the nerve cell membrane to K+ and Na+; the membrane is highly permeable to ______ and is only partially permeable to _____. Therefore, _____ tends to leak out of the nerve cell, causing a net _______ charge at the interior of the nerve cell membrane. - 3. Presence of _________ (protein channels: active transport) in the nerve cell membrane. When activated, these protein channels pump out ________ ions to every _______ ions pumped in, maintaining the resting potential.
- K+/ Na+/ (negative/ positive) - K+/ Na+/ K+/ negative - sodium-potassium pump/ 3 sodium/ 2 potassium
Other NTs: - __________: in brain and ANS = excitatory. - __________: in CNS; excitatory or inhibitory - usually controls movements by preventing over-stimulation - _________ or speed stimulate dopamine - overabundance can lead to __________ and pronounced disturbances in mood and behavior. - _______ inhibits the removal of dopamine resulting in concentration of dopamine and creating a high. - if neurons making dopamine are damaged, the body is characterized by stiffness and rigidity.... called _________. - ________: emotions - effects ______ and depression; not enough can cause depression. - ______ activates serotonin (increased serotonin levels can stimulate hallucinations) - Serotonin eventually finds its way out of tissues into the blood. There, it is actively taken up by blood _______, which store it. When the platelets bind to a clot, they disgorge serotonin, which serves as a _______ and helps to regulate hemostasis and ___________. Serotonin also is a ___________ for some types of cells, which may give it a role in wound healing. - _______: general inhibitory effect; reduces anxiety - ___________ difficulty in controlling movements and intellectual abilities decrease.
- NE - dopamine - amphetamines - schizophrenia - cocaine - Parkinson's disease - serotonin - attention - LSD - platelets/ vasoconstrictor/ blood clotting/ growth factors - GABA - Huntington's disease
Sleep: - _________: first 90 minutes; relaxation with a decrease in heart rate, BP and energy utilization; decline is up to 30%. - _________: occurs in active dreaming with a change in BP and respiratory rate; less responsive to outside stimulation. There is an increase inhibition of sensory motor neurons except eye muscles ..... tremendous use of _____ and ________ are actively inhibited ...... this temporary _______ prevents us from acting out our dreams.
- NREM deep sleep - REM sleep/ O2/ skeletal muscles/ paralysis
Memory Consolidation Cellular Level: - Involves anatomical and physiological changes in neurons and synapse - Increased _______ release (active synapses increase amount of NT stored) - Increased _________ (repeated activation causes continuous release of NT in small amounts producing graded potential that then brings the membrane closer to threshold) - Formation of additional synaptic connection in axon tip branches - These processes create _________ changes that facilitate communication along a specific neural circuit and is thought to be the basis of __________. - __________ = a single circuit that corresponds to a single memory; forms from experience and repetition. - Repeated, exceedingly _______ or _________ events increase conversion to LTM. - Drugs, like _______ and _______, may enhance memory consolidation.
- NT - synaptic facilitation - anatomical/ memory storage - memory engram - pleasant or unpleasant - caffeine and nicotine
How Neurons Communicate: - _____________ - chemical messengers; adrenergic synapse; transmit message over synapse. - _________ and ________: associated will depression - _________: simulated by the ANS; used in learning, ________ , increase HR) - ___________: inhibitory in the brain but has a peptide that acts as a major NT for learning. - ___________ (muscle action, memory, emotion) = cholinergic synapse = stimulates almost exclusively the ______. - __________: excitatory in the brain.
- NTs - serotonin and dopamine - norepinephrine (noradrenaline)/ memory - GABA - ACh/ PNS - glutamate
- When sodium enters a nerve cell during an AP, there is a time period that the nerve cell membrane cannot respond to a second stimulus: called _____________. This prevents the overlapping of APs. - This allows the AP to be propagated as a separate wave along the nerve cell membrane. - Though the strength of APs remains the same irrespective of stimulus intensity, the __________ of APs increases with increasing stimulus intensity (strength).
- absolute refractory period - frequency
The Sequence of Events of Cholinergic Synapse: - EXACTLY THE SAME SEQUENCE WE HAD TO MEMORIZE FOR THE "SHORT ANSWER" LAST EXAM! - An enzyme, ____________, in synaptic cleft removes about 50% of ACh before it reaches receptors on postsynaptic membrane. ____________ is needed for this reaction which is derived from vitamins. ________ is reabsorbed from the synaptic cleft and is used to synthesize more ACh.
- acetylcholinesterase/ Coenzyme A/ choline
- _______: loss of memory resulting from disease or trauma. - Two kinds: - ____________: loss of memories of past events (head injury from fall or car wrecks) - ____________: cannot store additional memories but earlier memories are intact ..... common in _______ * Drugs such as ______ have been known to cause anterograde amnesia.
- amnesia - retrograde amnesia - anterograde amnesia/ senility * valium
Multiple Sclerosis: - _________ disease affects mostly young people. - ___________ disease affecting the CNS, reducing tissue to non-functional hardened lesions called ________, results in shunting and short-circuiting of the current, exciting tissue more slowly = leads to the eventual ________ of impulse conduction. - Symptoms include visual disturbances, problems controlling muscles (weakness, clumsiness, and ultimate paralysis), speech disturbances, and urinary incontinence. - ______ attack the myelin sheath.
- autoimmune - demyelinating/ scleroses/ cessation - T-cells
Huntington's Disease: - Genetic __________ disorder because only one copy of the defective gene, inherited from either parent, is necessary to produce the disease; symptoms appear later in life. - The protein expressed by the Huntington's gene (__________) interacts with another protein to disturb the way that ________ accumulates in the brain. - Cholesterol is essential for healthy brain cells and the network along those brain cells - but the cholesterol needs to be in proper levels and in the proper locations. When the network of brain cells is disrupted, ______ skills, _______ skills, and ______ can be affected.
- autosomal dominant - mutant huntingtin/ cholesterol - motor/ cognitive/ speech
- Each AP is propagated along the axon membrane, from its proximal end (_________) to the distal axonal terminals; the strength of depolarization remains the same from start to finish. - __________: is the minimum depolarization required to generate an AP, and it is a change reversal from -70mV to -50mV. This is the critical point at which the second set of _______ channels (voltage sensitive) open up to allow the entry of greater numbers of this ion. Once the threshold potential is reached, the _______ will stop only when the charge reversal reaches +30 mV. - This is known as the _________ phenomenon of AP. - If the charge reversal does not reach the threshold potential, only sub-threshold signals are generated. These are called ______ = short distance. - The _______ only have sodium channels that respond to chemical stimuli, and so they only generate ___________ = do not spread far. They usually trigger specific cell functions like secretion from _______.
- axon hillock - threshold potential/ sodium/ depolarization - all or none - graded potentials - dendrites/ graded potentials/ glands
Speed of Propagation of APs: - Depends on: - Thickness of ________: the thicker, the faster the speed of propagation of APs, as the thicker fibers offer less __________ to the waves of APs. - Presence of _____________: as this is mainly made of fats and protein, it acts as insulation for the axons, allowing rapid propagation of APs. * A ____________ fiber propagates APs about 150 times faster than a ____________ fiber. Myelin sheath formed by Schwann cells, is discontinuous, and has spaces called _____________, where the ____________ channels are concentrated. These sodium channels cause the APs to jump from one node to the other, this rapid mode of propagation of APs by myelinated fibers is called ______________.
- axon/ resistance - myelin sheath * myelinated/ non-myelinated/ nodes of Ranvier/ voltage-sensitive sodium/ saltatory propagation
Chemical Synapse: - 1. The AP arrives and depolarizes the synaptic knob, simulating and opening the voltage-gated ________ channels which - 2. Triggers exocytosis of ______ that diffuses across synaptic cleft. - 3. Receptors on postsynaptic membrane are chemically gated ion channels that open; ______ flow into cell and _________ creates graded potential. - 4. The greater amount of ACh released by the presynaptic membrane, the more cation channels open on the postsynaptic membrane increasing the depolarization, bringing _______ to establish an AP.
- calcium - ACh - Na+/ depolarization - threshold
States of Consciousness: - _________: alert, attentive or aware; state of wakefulness; an indication of on-going CNS activity. - _________: ranges from deep unresponsiveness condition to light nod; can become an abnormal or depressed state of wakefulness = ______. - ________ are used for diagnosing ______ and sleep disorders, for brain function and to determine brain death.
- consciousness - unconsciousness/ coma - EEG/ epilepsy
- General degenerative changes include: - Neural processing is less efficient - Memory _______ becomes increasingly more difficult - Sensory systems (hearing ....) are less sensitive - reaction rates are lowered - precision motor control decreases - These can all lead to memory loss = _______
- consolidation - senile dementia = senility
Propagation of AP: - Two kinds: - ___________: in unmeymlinated axons ..... chain reactions of depolarization of adjacent portions of membrane .... can only move forward because previous membrane segments are still in ___________ so APs always proceed away from site of generation and cannot reverse (1 meter/second = like the wave in football). - __________: impulse moves more rapidly because myelin sheath is poor conductor (increases _________ to flow of ions so ions can only cross at nodes); therefore, only nodes can respond to stimulus so current skips internodes and jumps from node to node. __________ is used because less surface area is involved and fewer Na+ need to be pumped out (active transport).
- continuous propagation/ absolute refractory period - saltatory propagation/ (resistance)/ less energy
Graded Potentials: - The transmembrane potential is most affected at the site of stimulation, and the effect _______ with distance. - The effect spreads passively, owing to local currents. - The graded change in membrane potential may involve either depolarization or hyper polarization. The nature of the change is determined by the properties of the membrane ______ involved. For example, in a resting membrane, the opening of sodium channels will cause __________, whereas the opening of potassium channels will cause __________. That is, the change in membrane potential reflects whether positive changes enter or leave the cell. - The stronger the stimulus, the greater the change in the transmembrane potential and the larger is the area affected.
- decreases - channels/ depolarization/ hyper polarization
- The opening of stimulus-gated Na= channels in response to a stimulus permits more Na+ to enter the cell. As the excess of positive ions outside the plasma membrane decreases, the magnitude of membrane potential toward zero is called ___________. - During ________, a stimulus triggers the opening of stimulus-gated K+ channels ..... as more K+ diffuses out of the cell, the excess positive ions outside the plasma membrane increases, increasing the magnitude of the membrane potential. Movement of the membrane potential away from zero is called _________.
- depolarization - inhibition/ hyper-polarization
- ____________: when a nerve cell membrane is stimulated, sodium channels open up allowing rapid ______ of Na+, causing the charge reversal (the inner surface of the membrane begins to become ___________ charged). - Maximum change in transmembrane potential is proportional to size of the stimulus (# of _________); therefore, the more channels opened, the more Na+ enters the cell and the greater the membrane affected, thereby increasing the degree of depolarization. - An action potential is an _____________ event.
- depolarization/ influx (entry)/ positively - open channels - all or none event
- Nerve impulses are electrical signals that are generated in the trigger zone of a neuron as the result of membrane _______ and are conducted along the axon to the axon terminal, where they continue to another ______ or a ______ or _______. - In mammalian cells, the concentration of _____ is much higher inside the cell than outside while the concentration of _____ and _____ is much higher outside the cells than inside the cell. - Because the membrane has leak channels, it allows for relatively free flow of _____ to leak out of a cell, down its concentration gradient. However, the K+ leak channels allow ____ to enter the cell at a ratio of 100:1 so that many more potassium leave the cell than sodium entering, creating a small ________ charge accumulating on the outside of the membrane. - The maintenance of the resting potential depends primarily on the ________ in the membrane, actively pumping Na+ out of the cell and K+ into the cell. For every ________ pumped out, ________ enter the cell. - In most cells, the potential across the membrane is generally constant, however, in neurons and muscle cells the membrane potential can undergo changed making these cells capable of conducting an electrical signal called ___________.
- depolarization/ neuron, muscle cell or gland - K+/ Na+ and Cl- - K+/ Na+/ postive - Na+K+ pump/ 3 Na+/ 2K+ - excitable tissue
Parkinson's Disease: - In the normal brain, some nerve cells produce the chemical ________, which transmits signals within the brain to produce ________ movement of muscles. In Parkinson's patients, 80% or more of these _________ producing cells are damaged, dead, or otherwise degenerated. This causes the nerve cells to fire widely, leaving patients ____________ their movements. - Symptoms: tremor, or trembling in hands, arms, legs, jaw, and face (jerking movements) - Treated with ______ that passes BBB to make dopamine and more recently now using deep brain stimulation.
- dopamine/ smooth/ dopamine/ unable to control - L-dopa (precursor to dopamine)
Properties of Synapses: - A synapse may be _______ = direct physical contact between the cells, or ________ = involves a NT. - Electrical synapses = where the presynaptic and postsynaptic membranes are linked together at __________ which permit the passage of _______ between cells as in ________ cells. This allows changes in transmembrane potential of one cell to produce a local current that will affect the other cell. Thereby producing an AP that will propagate _______ and efficiently from one cell to the next ........ it will always be propagated to the next cell if there are __________. - Chemical synapses: more dynamic and complex because cells are not directly coupled. At a chemical synapse, an arriving AP may or may not release enough _______ to bring the postsynaptic neuron to threshold. Most abundant type of synapse communication can only occur in one direction ...... from pre to post. - NT Classification: - __________ cause depolarization and promote generation of APs - __________ cause hyper polarization and suppresses the generation of APs
- electrical/ chemical - gap junctions/ ions/ cardiac/ quickly/ gap junctions - NT - excitatory NT - inhibitory NT
- _________ of a neuron occurs when a stimulus triggers the opening of stimulated Na+ channels. - Stimulus-gated channels are ion channels that open in response to a ________ or a __________ from another neuron. - Many stimulus-gated channels are located in the membrane of the neuron's ________ zone; the ______ and _______.
- excitation - sensory stimulus or chemical stimulus - input/ dendrites and soma
Neurotransmitters: - Chemical synapses are the most abundant type of synapse. - A common NT for chemical synapses is ACh (acetylcholine) which is an ________ NT that causes depolarization. - The effect of a NT on postsynaptic membrane depends on the properties of the ____________ , not on the nature of the NT. - Synapses releasing ACh are called _________ synapses and include: - All __________ junctions - All neuron to neuron synapses in PNS - All ______ to _______ within parasympathetic division of ANS.
- excitatory - receptors - cholinergic - NMJ - NMJ to NGJ
Axon Cell Membranes have Two Types of Sodium Channels: - One set responds to chemical stimulus (NT molecules) - One set responds to changes in voltage - When the first set is activated by a NT, only relatively _____ sodium ions enter the nerve cell; the second set of sodium channels open up only when the charge reversal reaches a critical point at which the increased voltage inside the cell causes a ___________, resulting in a rapid entry of more sodium ions into the cell. - ________ and ________ only have the first set of sodium channels that respond only to chemical stimuli.
- few/ positive feedback - dendrites and cell body
- Neurons bring about internal coordination by means of nerve signals. - ____________: short distance signals - ____________: long distance signals - accomplished with _______ - At rest, the cell membrane of a neuron exhibits ____________: - its inner surface has a net ________ charge, while its outer surface has a ______ charge. - The charge difference across the membrane at rest is called the _____________, and the average value of RMP is ______. Neurons and skeletal muscle fibers use this RMP to generate APs and graded potentials.
- graded potential - action potential - NTs - electrical polarity - negative/ positive - Resting Membrane Potential (RMP)/ -70mV
- Local potentials are called _______ because the magnitude of deviation from the RMP is proportional to the magnitude of the stimulus; meaning they can be large or small ....... they are not ________ events. - Local potentials are called local nerve signals because they are more or less ________ to a particular region of the plasma membrane; therefore, they do not spread all the way to the end of a neuron's axon.
- graded potentials/ not all or none events - isolated
- Our ________ can influence our state of mind, including our mood and behavior. - __________ contributes to neurodegenerative diseases such as Parkinson's disease.
- gut microbiota - mitochondrial dysfunction
- ___________: when the charge difference across the nerve cell membrane is greater than at resting membrane potential (RMP); i.e. the charge difference between the inner and outer surface of the membrane becomes -90 or -100 mV. - This hyper polarization is caused by the exit of ________ from the cell's interior while the sodium channels are closed. - A hyper polarized membrane will take _______ to depolarize slowing down or preventing the process of generating an electrical signal by the nerve cell. - ______ will leak out through channels easier than ____ will enter through channels.
- hyper polarization - K+ - longer - K+/ Na+
RAS: Reticular Activating System: - Important brain stem component making it ______ with sensory and motor neurons. - Headquarters for _______ or ________, providing watchdog services. - Extends from medulla oblongata to mesencephalon, projecting into ______. - When RAS is inactive ...... so is __________ - increase in stimulation ..... increases states of _______, ______, and ______ - after many hours of stimulation --> less responsiveness because of ________. The RAS extends the length of the _______
- integrated - arousal and awakening - thalamus - cerebral cortex - arousal, alertness, and attentiveness - neural fatigue - brainstem
Neurophysiology: - Transmembrane Potential: - found in all cells - is the difference in _______ makeup on both sides of cell membrane. - As rest = _______________: intracellular fluid (cytosol) is high in ______ and negatively charged _________ / extracellular fluid (ECF) is high in concentrations of _______ and ______. - All neural activity begins with a change in the resting potential of a neuron; a typical stimulus produces a temporary, localized change in resting potential called a ___________ which decreases with distance from the stimulus. - If a graded potential is sufficiently large --> triggers an ___________ of the axon membrane --> propagated as an electrical impulse --> towards synapse. It does not diminish as it moves away from stimulus. - __________ are released at the synapse by presynaptic cells which bind to postsynaptic plasma membrane, changing its permeability --> impulse moves on.
- ionic - resting potential: K+ and proteins/ Na+ and Cl- - graded potential - action potential - NTs
- Ion distribution is kept uneven due to selective permeability of membrane channels. - As rest (resting potential), ion movement occurs through ________ (channels that are always open; passive transport). - Negatively charged _______ inside cannot cross membrane, _____ will leak out through potassium channels easier than _______ entering through sodium channels; therefore, inner membrane surface has excess _______ charge than outer surface = ________________. - Movement of ions is driven by concentration gradient also called ___________. - The difference of positive and negative charges in either side of membrane = ____________. The size of this is measured in volts or millivolts. - Potential difference varies among cells but average is -70mV which is typical for neurons **** inner membrane is __________ with respect to exterior. (negative inside and positive outside). - Positive and negative charges attract one another and will move together to eliminate the potential difference between them. A movement of charge to eliminate a potential difference is called a _________.
- leak channels - proteins/ K+/ Na+/ negative/ transmembrane potential - chemical gradient - potential difference - negatively charged - current
Membrane Channels Review: - Control of ion movement across membrane occurs by specialized channels: - Passive channels or __________ always open; therefore, important in stabilizing normal _________. - Active channels or __________ - open and close in response to specific stimuli. - closed but capable of opening - open = activated - closed and incapable of opening - Kinds: - _____________: located on excitable membrane like axons; open and close in response to change in transmembrane potential (example: _____, _____, and _____ channels). - ____________: open and close when bound with specific chemicals (_______) like ________; abundant at dendrites and neuron cell body. - ____________: open and close in response to distortion of membrane surface like touch, pressure, or vibration ...... like in the ________. - At resting potential, most gated channels are closed - Opening gated channels _________ ion movement and changes transmembrane potential.
- leak channels/ resting potential - gates channels - voltage gated/ Na+, K+, and Ca++ - chemically gated/ (ligand)/ NT like ACh - mechanically gated/ senses - increases
Higher Order Functioning: Cerebrum: - ________: stored bits of information gathered through experience. - ______ memories; specific bits of info (color of stop sign) - _______ memories: learned motor behavior (riding a bike) - Two Classes: - ________: primary memories that do not last long, but while they last, can be recalled immediately (peoples' names) - ________: last longer and stored in cerebral cortex - Two kinds: * _________ fade with time and may require considerable effort to recall. * ____________ are with you for a lifetime (your name)
- memory - fact - skill -STM -LTM - secondary memories - tertiary memories
- A sub threshold stimulus does not generate an AP, but once threshold voltage is reached, the stronger the stimulus, the _______ frequently APs are generated.
- more
- ________: lapse abruptly into REM sleep from the awake state, lasting 15 minutes. - _______: chronic inability to obtain the amount or quality of sleep needed to function adequately during the day. - _______: repeated, temporary cessation of breathing during sleep, victim awakes abruptly due to hypoxia. - _________: loss of consciousness often falling to the floor, body wracked by uncontrollable jerking, cause by electrical discharges of groups of brain neurons.
- narcolepsy - insomnia - sleep apnea - epileptic seizures
Neuromodulators: - Synaptic knobs release a mixture of compounds either by diffusion or exocytosis which: - can alter the rate of NT release - ____________ bind to receptors either on pre or postsynaptic membranes. * Some are called _______; effects are similar to opium and morphine because they bind to the same group of postsynaptic receptors; function is relief of pain by releasing NT ________ = pain inhibiting substances that delay pain sensations. * Endorphins, endomorphins, dynorphins, and enkephalins area all stronger than morphine and have long term effects - NT and neuromodulators act as _______ messengers in that they bind directly to receptors on membrane. However, these are secondary messengers usually a _______ that binds GTP to cAMP = important in turning on enzymes. - Many drugs affect NS by stimulating or binding ______ that normally respond to NT or neuromodulators.
- neuropeptides * opioids/ substance P - primary/ G protein - receptors
Aging: - Anatomical changes: - _______ in brain size and weight & the number of neurons - decrease in blood flow to brain --> increases fatty deposits and accumulation --> __________ = increases chances of having a ________ - Reduced NT production - Reduced synaptic connections
- reduction - atherosclerosis/ CVA (cerebra-vascular accident) = stroke
Memory Consolidation: - The conversion of STM to LTM: requires ________ - Repetition of short-term bits of info are necessary to become long term memories - Repetition allows for ______ of STM into LTM - _______ and __________ are required for conversion (learning is dependent on these). - dependent on AA __________; NT that opens Ca+ channels. - Blocking receptors of ________ in hippocampus prevents long term memory formation. - Info stored in different cerebral cortex areas.
- repetition - conversion - amygdaloid and hippocampus - glutamate - NMDA (N-methyl D-aspartate)
Relative Refractory Period: - This is the time of _________ of the nerve cell membrane (time of K+ exit). - During this period the nerve cell membrane is capable of responding to a second _________ stimulus; an exceptionally strong stimulus can reopen the Na+ channels. - Stronger stimuli trigger more frequent _____ by intruding into the relative refractory period. - By reducing the relative refractory period, the nerve cell membrane ________ the frequency of APs under increased stimulus strength; i.e. a weak stimulus causes _____ frequency APs and a strong stimulus causes ______ frequency APs.
- repolarization - stronger - APs - increases/ low/ high
- In a resting neuron, some of the K+ channels are open, but some of the Na+ channels are closed, meaning that K+ ions pumped into the neuron can diffuse back out of the cell in an attempt to equalize its concentration gradient, but very little of the Na+ pumped out of the cell can diffuse back into the neuron. This each of the membrane's ___________ permeability characteristics create and maintain a slight excess of ________ ions on the outer surface of the membrane.
- selective/ positive
Alzheimer's Disease: - Most common cause of ______ - Microscopic examination reveals ______ and ________ in regions involved with memory, emotion and intellectual function. - Late onset linked to genes for ________ transport on chromosome # ____ - Early onset linked to chromosomes #s ________ - Victims exhibit memory loss (particularly of recent events), shortened attention span, disorientation, hallucinations and eventual language loss. - NO CURE - Abnormal intracellular deposits: - ________: granular pigments of fat - ________: masses of neurofibrils forming dense mats inside the cell body and axon. - Abnormal extracellular deposits: - ________: accumulations of fibrillar proteins (abnormal amounts of ________ - peptides associated with memory processing) surrounded by abnormal dendrites and axons. - Healthy nerve cells in the brain support structures called _______, which guide nutrients in the cell. A special kind of protein makes these structures stable... what is it?
- senility - plaques and neurofibrillary tangles - cholesterol/ 19 - 1, 14, 19, 21 - lipofuscin - neurofibrillary tangles - plaques/ amyloids - microtubules/ Tau proteins
- _______ is defined as a state if partial consciousness from which a person can be aroused by stimulation = cortical activity is depressed but not brain stem functions. - The _______ is responsible for the timing of sleep cycle. - Short or infrequent REM is one cause of _______. - _________ increases during sleep. - Periods without sleep (deprivation) lead to various disturbances in mental functioning = _________ behavior. - ______% of US population have some form of sleep disorder - sleep walking, slowed reaction time, irritability, and mood swings - _______ waves are regular and rhythmic, low amplitude waves; they indicate a brain that is idling .... a calm, relaxed state of wakefulness. - ______ waves are also rhythmic but less regular and with a higher frequency indicating we are mentally alert as when concentrating on some problem or visual stimulus. - _______ waves are still more irregular; more common in children but less so in awake adults, but may appear when concentrating and frustrated. - ______ waves have a high amplitude indicating deep sleep and the ______ is suppressed such as when under anesthesia. In an awake adult, they indicate brain damage. - Brain waves whose frequency is too high or too low suggests problems with the cerebral cortical functions; brain waves are always present during sleep and comas so an absence indicates ________
- sleep - hypothalamus - tiredness - protein synthesis - aggressive - 25 - alpha - beta - theta - delta/ RAS - brain death (flat EEG)
- When a barrier (membrane) separates the oppositely charged ions, it creates a resistance to ionic movement; therefore, - If resistance is high = current is ______ (b/c few ions can cross) - If resistance is low = current is _______ - The resistance can change by opening and closing ion channels resulting in ________. - The electrochemical gradient (the sum of _______ and ________ forces acting on an ion, to include # of ions and # of channels) is a form of ________ energy. The membrane is a physical barrier ..... like a dam; any opening of channels will cause ions to flow under tremendous pressure; therefore, a stimulus that opens sodium channels will trigger a rush of Na+ ______ the cell. - At resting potential, a cell must bail out _______ that leaks in and recapture ______ that leaks out. This is accomplished by the __________; the pump has a carrier protein called sodium-potassium _______. It exchanges ___________ for _________ which maintains the resting potential.
- small - high - currents - (chemical and electric)/ potential/ into - Na+/ K+/ sodium-potassium pump/ ATPase/ 3 intracellular Na+ for 2 extracellular K+
- Another mechanism also operates to maintain the RMP ..... the ________ is an active transport mechanism in the plasma membrane that pumps these ions in opposite directions (_____ ions for _____ ions) at different rates, allowing for maintaining a difference in electrical charge across the membrane. IT IS ________.
- sodium-potassium pump/ (3 Na+ out and 2 K+ in)/ PRIMED
Action Potentials: - ________ opens sodium channels allowing entry of sodium ions into the nerve cell causing ___________ at the inner surface of the membrane. When the charge reversal (depolarization) reaches a critical point (________), the second set of sodium channels (__________ channels) open up causing rapid entry of more Na+, which will take the depolarization up to +30 mV. The whole event last for 1 ms. - Closure of sodium channels stops Na+ entry. - Opening of potassium channels, and the exit of K+ from the nerve cell causes _______ of the nerve cell membrane as the positive charge at the inner surface begins to change to negative again. - Potassium ions continue to exit for a short time even after the RMP is restored, resulting in _________. This activated the _________ in the nerve cell membrane which will restore original ion concentration of the cell's interior and exterior (RMP).
- stimulation/ depolarization/ (threshold)/ (voltage-sensitive) - repolarization - hyperpolarization/ sodium-potassium pump
Nervous System Disorders: - Infections like rabies (_____), meningitis (_____), polio (_____), and herpes (______) - Transmissible spongiform encephalopathy diseases are caused by _______; human prion disease is called ______ or _________. Bovine spongiform encephalopathy = cattle/ chronic wasting disease = deer/ and scrapies = sheep. - Toxins: ______ metals (Pb, Hg). ________ prevent opening on Na voltage gated channels = found in ______ and _____. - ______: initiated by abnormal synchronous, uncontrolled electrical discharges.
- virus/ bacteria/ virus/ virus - prions/ kuru or Creutzfeldt-Jakob disease (CJD) - heavy/ neurotoxins = mushroom or seafood - epilepsy