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What is a neuron?
An electrically excitable cell that receives/processes/sends info based on changes in electrical difference across a membrane, and through chemical messages TERM 2
What two conditions are required to create
electrical activity?
DEFINITION 2 Selectively permeable membrane (uses facilitated diffusion)Differential distribution of ions across the membrane TERM 3
What are the concentrations of Na+ and K+
on the inside and outside of a neuron?
DEFINITION 3 Na+ inside: 15mMNa+ outside: 150mMK+ inside: 150mMK+ outside: 5mMtightly regulated! TERM 4
What does the sodium/potassium ATPase
do?
DEFINITION 4 Exchanges 3 Na+ out for 2 K+ in to the cellIs NOT a part of electrical signalling! Just sets up separate charge TERM 5
Where is the charge located in electrical
signalling?
DEFINITION 5 Right next to the membrane
Which side of the membrane is negative and
which is positive?
The inside of the membrane is negative relative to the outside.Voltage of a membrane is denoted as the inside voltage relative to the outside (ie. -70mV = the inside is 70mV less positive inside as it is outside) TERM 7
What is the K+ equilibrium potential? Na+?
Resting membrane potential?
DEFINITION 7 K+ = -90mVNa+ = 60mVResting membrane potential = - 70mV TERM 8
What is the equilibrium potential?
DEFINITION 8 The point at which the concentration gradient and electrical gradient of an ion are equal and opposite to each other. Is determined using Nernst equation. TERM 9
How does ion permeability affect resting
membrane potential?
DEFINITION 9 The more permeable ion will have a greater effect on the resting membrane potential (potential will be closer to that of the most permeable ion).Resting membrane potential determined by Goldman equation TERM 10
Define Depolarization
DEFINITION 10 A shift in membrane potential towards a more positive potential by changing membrane permeability
Define electronus
The process by which and electrical potential propagates. Is where the positive charge from a depolarization event is attracted to the negative charge in an adjacent area and travels to that area, causing depolarization of adjacent membrane. It is a passive event. TERM 17
Why can't a potential propogate very far by
electronus?
DEFINITION 17 Because of electrical decay caused by leaky channels, where positive charge crosses to the outside of the membrane. This causes less depolarization in adjacent areas and the signal fades away. TERM 18
Define graded potential
DEFINITION 18 Transient change in electrical environment of a membrane that can be variable in amplitude TERM 19
Define generator potential
DEFINITION 19 And transient change in electrical environment in response to a sensory input. Can be graded but not necessarily TERM 20
What is the length constant and how is it
calculated?
DEFINITION 20 Length constant (lambda) is how far a charge propogates each time it is transfered. Usually between 0.1-1mm.Lambda = (Rm/Ra)^0.5Ra = resistance to positive charge travel along an axon = axial resistanceRm = resistance. To pos charge travel across the membrane (out of the axon) = membrane resistance
What is the difference between electronus
and active propagation?
Active propagation uses multiple voltage gated channels along a membrane to propogate a membrane potential longer without letting it fade by creating multiple depolarization events. Electronus is just one initial depolarization and three propagation of charge thereafter. TERM 22
What changes the rate of action potential
propagation and why?
DEFINITION 22 Diameter of fiber: increasing diameter decreases Ra by letting more charge flow per unit time, which depolarizes neighboring membrane more quicklyThe amount of membrane capacitance: reduce effect of ions being attracted to one another across a membrane by making the membrane thicker (won't be as close to eachothers electrical fields) which will reduce the force needed to separate the charges and thud the time to depolarize a membrane to threshold. TERM 23
What is capacitance and what role does it
play in action potential propagation?
DEFINITION 23 And capacitor is two opposite charges separated by a non conductive plate. This causes ions to be attracted to one another and stick close to the membrane. In order to propogate the charge to threshold, the ions need to be removed from right next to the membrane so the membrane can be charged positively.Capacitance(stored charge across the membrane) is proportional to surface area and distance between charges and needs to be reduced to move an action potential quicker. Capacitance is reduced with myelin TERM 24
What is saltatory conduction?
DEFINITION 24 Conduction of an action potential using myelin. In myelinated areas, potential conduction is fast. In unmyelinared areas (nodes of ranvier), conduction is slow. TERM 25
What cells produce
myelin?
DEFINITION 25 Schwann cells in PNS and oligodendrites in CNS
Define IPSP and what is the most common
neurotransmitter?
IPSP: inhibitory post synaptic potential A neurotransmitter binds a ligand gated channel and causes membrane potential to get further away from threshold Most common NT is GABA TERM 32
What happens when GABA binds a ligand
gated channel at the synapse?
DEFINITION 32 Channel opens and Cl- can pass through. Had an equilibrium potential of -70mV, so will "clamp" membrane potential at - 70mV and stop EPSP. TERM 33
Define neuromuscular junction
DEFINITION 33 The connection between an alpha motor neuron and muscle cells TERM 34
What is a motor
unit?
DEFINITION 34 Where one motor neuron branches at the terminal end to connect to multiple muscle cells so each responds to the same electrical signal and fire all at once. TERM 35
What neurotransmitter does a neuromuscular
junction use and how is it stored?
DEFINITION 35 AcetylcholineStored in vesicles in active zones at the axon terminal
What are two features of the synaptic cleft of
a neuromuscular junction that allow the
junction to work again after a transmission?
Adhesion of neuron to muscle makes sure that neuron doesn't disconnect after a muscle twitchAcetylcholinesterase breaks down acetylcholine in the synapse so the muscle doesn't twitch again (or partially) after an event. TERM 37
Define EPP
DEFINITION 37 EPP (end plate potential) is a membrane potential that is always high and suprathreshold, which takes place on the post synaptic membrane of a neuromuscular junction. It is due to a high concentration of sodium and potassium channels (in the "perijunctional zone") surrounding the motor end plate where many acetylcholine receptors are situated in rows of ridges. TERM 38
Define nerve
DEFINITION 38 A bundle of axons bundled together with other axons. Not all are necessarily myelinated TERM 39
What does compression neuropathy do to a
nerve?
DEFINITION 39 When blood flow to a region is stopped, it compromises the axons ability to transmit an action potential, resulting in slow or no transmission TERM 40
Where do afferent and efferant nerves
go?
DEFINITION 40 Afferent = towards CNS (sensory are dorsal in spinal cord)Efferent = away from CNS (motor are ventral in spinal cord)
What are the six autonomic sensory
receptors?
Baroreceptor: monitor blood pressureOsmoreceptor: regulation of plasma ions/blood dilutionThermal receptors: in skin, regulate body temperatureCutaneous receptors: detect Sexual stimuliPain fibers: in visceraStretch receptors: monitor distenion in lungs, bladder, stomach, bowel TERM 47
What are the parasympathetic nerves called?
Which neurotransmitters are used and when?
DEFINITION 47 Craniosacral nerves: only uses acetylcholine (received with nicotinic receptors) TERM 48
What are the sympathetic nerves called?
What neurotransmitters do they use?
DEFINITION 48 Thoracolumbar nerves: use acetylcholine (nicotinic receptors) first (preganglionic NT) and norepinephrine after (postganglionic NT) TERM 49
Are the effects of the sympathetic system
catabolic or anabolic? What do they involve?
DEFINITION 49 Catabolic (break down components to provide energy)Involves increased heart rate/stroke volume/BP/blood flow to skeletal musclesDecreased blood flow to skinFight or flight - release of epinephrine and norepinephrine from adrenal medulla to begin muscle glycogenolysis TERM 50
Are the effects of the parasympathetic system
catabolic or anabolic? What do they involve?
DEFINITION 50 Anabolic (build components to store energy)Involves decreased heart rate/stroke volume/BPIncreased GI motility and secretionsRelaxation of sphincters in stomach, esophagus, bladder
What is paradoxical coactivation?
Parasympathetic and sympathetic systems activated at once during intense conflict situations. Ie. Peeing yourself because you're scared. TERM 52
What are the twelve cranial nerves?
DEFINITION 52
- Olfactory2. Optic3. Oculomotor4. Trochlear5. Trigeminal6. Abducens7. Facial8. Auditory (vestibulocochlear)9. Glossopharyngeal10. Vagus11. Accessory12. Hypoglossal TERM 53
Give the cranial nerve number and function:
olfactory
DEFINITION 53
- Sensory, smell TERM 54
Give the cranial nerve number and function:
optic
DEFINITION 54
- Sensory, vision TERM 55
Give the cranial nerve number and function:
Oculomotor
DEFINITION 55
- Motor: voluntary (move eye towards midline, medially); parasympathetic (constrict pupil and thicken lens)
Give the cranial nerve number and function:
Glossopharyngeal
- Motor: voluntary (pharynx swallowing); parasympathetic (salivary glands)Sensory: tastebuds of posterior third of tongue; carotid sinus baroreceptor (monitor arterial BP - important for controlling HR and BP); carotid body chemoreceptors (monitor CO2 and O2 in arterial blood - important in controlling respiration) TERM 62
Give the cranial nerve number and function:
vagus
DEFINITION 62
- Contains 90% of parasympathetic nervesMotor: voluntary (pharynx swallowing - most important for swallowing, larynx phonation); parasympathetic (slow heart rate, secretions and motility of abdominal organs)Sensory: aortic baroreceptors and chemoreceptors; GI tract TERM 63
Give the cranial nerve number and function:
accessory
DEFINITION 63
- Motor: voluntary (swallow, shrug shoulders) TERM 64
Give the cranial nerve number and function:
Hypoglossal
DEFINITION 64
- Motor: voluntary (swallow) TERM 65
What is the function of MLF in vision?
DEFINITION 65 Medial longitudinal fasciculus carries info to coordinate between Oculomotor and abducens (connects the two ganglia)
What is a nucleus and where are the cranial
nuclei generally located?
Nucleus: collection of cell bodies in the CNS that have a common functionMost of cranial nuclei are located in the brain stem TERM 67
How are spinal and cranial nerves similar?
DEFINITION 67 They are both mixed-modality TERM 68
How many pairs of spinal nerves are there?
How many per spine region?
DEFINITION 68 31 pairs8 cervical (C1-C8)12 thoracic (T1-T12)5 lumbar (L1- L5)5 sacral (S1-S5)1 coccygeal TERM 69
Which spinal nerve pair does not have
sensory fibers?
DEFINITION 69 C TERM 70
Which regions of the spinal nerves serve the
limbs?
DEFINITION 70 Cervical serves arms, thoracic serves legs
Must sensory stimuli that active action
potentials always be directly on the neuron?
No, can also have chemical stimuli TERM 77
Where does the sensory generator potential
stop and the action potential begin?
DEFINITION 77 At the first node of Ranvier TERM 78
Do sensory generator potentials have a
refractory period? Why?
DEFINITION 78 No because they are not actively propogated (don't use voltage gated channels) TERM 79
What is the difference between EPSP and
generator potentials? Similarities?
DEFINITION 79 EPSP generated though a synapse, not a sensory terminalSimilar:can be gradeddoesn't cause refractory periodnot actively propogated TERM 80
What are the special senses?
DEFINITION 80 Olfaction - Cr1Vision - Cr2Taste - Cr7 and 9Hearing - Cr
What are the general (somatic)
senses?
Senses that are detected from all parts of the body ie. touch, heat... TERM 82
What are the somatic sense
receptors?
DEFINITION 82 Photoreceptors: light; rods and cones in retinaThermoreceptors: changes in temperature (central = hypothalamus and peripheral = skin)Nociceptors - pain, incl. "hot"Mechanoceptors: mechanical stimuli (exteroceptors: stimuli outside of the body) (proprioceptors: position of body or its parts) TERM 83
What do all sensory receptors have in
common when generating GPs?
DEFINITION 83 They all cause the opening or closing of ion channels TERM 84
Which sensory receptor has a direct effect on
a neuron?
DEFINITION 84 Somatosensry mechanoreceptors:Non-selective channels allow Na+ and K+ to pass through; net result is depolarization due to greater driving force of Na+ TERM 85
Which sensory receptors do not have direct
effects on neurons?
DEFINITION 85 Nociceptors, photoreceptors, chemoreceptors: all G-protein- coupled mechanisms that are indirect
What does the Pacinian corpuscl measure?
How does it determine this?
Vibration and texture, as well as pressure; determined by the rate of firing (too fast to keep up = smooth). Pressure sensed by consistent pressure on receptor that moves the fluid in the receptor around (picked up by accessories) TERM 92
Meissner's corpuscles and PAcinian corpuscles
are part of which receptor group?
DEFINITION 92 Tactile receptors to distinguish texture; rapidly adapting TERM 93
Merkel's endings and Ruffini endings are part
of which receptor group?
DEFINITION 93 Tactile receptors to determine maintained pressure (non- changing stimuli); slow adapting TERM 94
What is proprioception and what are the
propriocetors?
DEFINITION 94 Proprioception is sensing how our bodies are positionedPropriocetors:Muscle spindlesGolgi Tendon OrgansJoint receptorsSkin receptors TERM 95
Why are children often clumsy during growth
spurts?
DEFINITION 95 Because the brain has been programmed to believe that the body is smaller/shorter than it actually is, and sensory information being relayed to the brain from the limbs ext is slightly off from where the brain thinks it is.
What is different between pain/temperature
nerve endings and other receptor nerve
endings?
Receptors generally have specialized nerve endings, but pain and temperature nerve endings are free (not specialized) TERM 97
What are the two classification schemes of
peripheral nerve fibers?
DEFINITION 97 Conduction velocity classification:A - fastest, largest diameter, myelinatedB - smaller than A but myeliniated stillC
- slowest, smallest, non-myelinatedDiameter classification: (exclusive for sensory)I - fastestIIIIIIV - slowest, only unmyelinated one TERM 98
What is the conduction velocity classification
of nerve fibers used for? Are there any
subdivisions?
DEFINITION 98 Usually used for motor neurons. A is divided into alpha, beta, delta and gamma TERM 99
What is the function of the stretch reflex? Why
is it an important model?
DEFINITION 99 To keep you in the position you want to be in and to correct for any involuntary movement out of positionIt is important because it is the simplest model, being monosynaptic TERM 100
Do reflexes change with response to a
stimuli?
DEFINITION 100 No, they are generally unchangeable (will produce the same response no matter the type of stimuli)
