Lecture 2 Flashcards
1
Q
What are the main ions responsible for a membrane potential?
A
ECF: Sodium, Ca, Cl (high)
ICF: Potassium (high)
2
Q
What generates our resting membrane potential?
A
Mainly potassium. Potassium is high in our cells and low outside, so it wants to go out, giving it a diffusion potential that is highly negative.
3
Q
What prevents potassium from reaching its equilibrium point?
A
There is charge repulsion outside of the membrane, such as phosphate ions and negatively charged side chains, as well as potassium constantly being pumped back in.
4
Q
What voltage are we measuring with an electrode?
A
Always intracellular.
5
Q
What is the nernst equation used to calculate?
A
The diffusion potential level across a membrane that opposes the diffusion of that particular ion, which is the resting membrane potential.
6
Q
Key points of the Nernst equation
A
+/- 61* log [conc INSIDE/conc OUTSIDE]
It calculates electromotive force in mV.
It will be positive if the ion inside that is going out is negative.
It will be negative if the ion inside that is going out is positive. (EX: potassium)
7
Q
What proteins are responsible for maintaining our resting membrane potential?
A
A voltage gated Na+ channel
A sodium-potassium ATP pump (3 Na+ out, 2 K+ in)
A leaky K+ channel
8
Q
What is the Goldman’s equation and what is it for?
A
Combined Nernst equations for all ions that contribute to a membrane potential.
9
Q
How fast is depolarization?
A
Around 0.1 ms
10
Q
What occurs during depolarization?
A
Voltage-gated Na+ channels open and leaky potassium channel closes.
11
Q
What occurs during repolarization?
A
Voltage-gated Na+ channels reclose and leaky potassium channel opens partially.
12
Q
What condition must be met for an AP to be elicited?
A
Surpassing the threshold voltage. Once it is passed, a positive feedback cycle occurs to open all Na+ channels.
13
Q
What is the all or none principle?
A
If an AP is elicited on any point on the membrane, depolarization will travel and occur over the entire membrane or it will not happen at all.
14
Q
Nerve trunk myelination
A
The average nerve trunk contains about twice as many unmyelinated fibers than myelinated.
15
Q
Explain the basic anatomy of a myelinated axon
A
The center is the axon, with the myelin sheath surrounding it. The sheath is typically much thicker than the axon itself. Every 1-3mm is a Node of Ranvier.
16
Q
Explain Saltatory Conduction and its benefits
A
The electrical current can flow in the ECF outside of the sheath. APs only are elicited at the nodes, saving energy and allowing them to jump forward. It can increase transmission speeds from 5-50x.
17
Q
What are the 3 factors that can cause an AP?
A
Anything that can cause the diffusion of sodium into the membrane such as mechanical disturbances, chemical effects, or electricity.
18
Q
What is a refractory period and what happens to the channels?
A
A new stimulus cannot be elicited even if an AP is received. Na+ channels stay inactivated and immune to electrical signals.
19
Q
What two anesthetics act on sodium channel gates and what do they do?
A
Procaine and tetracaine, which make it difficult for Na+ channels to open.
20
Q
What does increased Ca++ in the ECF do to excitability?
A
It reduces it.
21
Q
What part of a neuron receives electrical signals?
A
Dendrites, which contain synapses.
22
Q
What part of a neuron transmits electrical signals?
A
Axon
23
Q
Afferent vs Efferent
A
Afferent is for input coming from a receptor to a neuron. Efferent is for output coming from a neuron to an effector (such as muscle contraction)
24
Q
What are the 3 roles of motor neurons?
A
Contraction of skeletal muscle
Contraction of smooth muscle
Secretion of active chemical substances from glands
25
What parallels our motor axis?
ANS
26
What kind of synapses are seen in the CNS for signal transmission?
Chemical only. They secrete neurotransmitters which act on receptor proteins in the membrane of the next neuron.
27
Where are most of the presynaptic terminals found on a neuron?
85% dendrites, 15% soma (cell body)
28
In what part of the neuron does summation of EPSP and IPSPs occur?
Axon hillock
29
What kind of channels does a presynaptic membrane contain?
voltage-gated calcium channels
30
What occurs during depolarization of a presynaptic terminal?
Ca channels open, cause an influx of calcium and the release of neurotransmitters.
31
What are the two components of a postsynaptic receptor?
Binding component: The part protruding out into the synaptic cleft.
Ionophore component: The part that passes through the postsynaptic membrane into the interior of the neuron.
32
What is an example of a secondary messenger system?
GPCR
33
Explain a GPCR mechanism
The transmitter substance binds to the receptor, which has an alpha, beta, and gamma subunit. The Alpha subunit is separated off to provide a variety of functions, such as opening channels, activating a cAMP cascade system, or activating gene transcription.
34
List a few ways to excite a membrane chemically.
Decreasing chloride ions to the inside
Decreasing diffusion of potassium outside
Increasing the number of excitatory receptors (up-regulation of excitatory receptors)
Decreasing the number of inhibitory receptors (down-regulation of inhibitory receptors)
35
List a few ways to inhibit a membrane chemically.
Opening chloride ion channels
Increasing potassium diffusion outside
Increasing the number of inhibitory receptors
Decreasing the number of excitatory receptors
36
Where are neurotransmitter synthesized?
In the cytosol of the presynaptic terminal.
37
What are the excitatory neurotransmitters?
Acetylcholine, Norepinephrine, epinephrine, glutamate.
38
What are the inhibitory neurotransmitters?
Dopamine, Glycine, Serotonin, and Nitric Oxide
39
What is the difference between a neurotransmitter and a neuropeptide?
Neuropeptides are protein molecules and are typically 1000x more potent with prolonged actions.
40
What is the decrement of electrical conduction?
The tips of dendrites are typically more excitable sine they have less negative membranes. As you get closer to the cell body, they continue to leak potassium, lowering the membrane potential and making it harder to depolarize.
41
Where do I find the most inhibition in a neuron?
As the axon hillock is approached. Inhibitory synapses typically occur near the soma.
42
What is the difference between spatial and temporal summation?
Spatial summation combines all EPSPs from multiple neurons in a set interval into one AP.
Temporal summation combines all EPSPs fired from a single neuron into one AP.
43
Explain the effect of pH on excitability
Alkalosis (increased pH) increases excitability, making you more prone to seizures. Hyperventilation can predispose one to having epileptic seizures.
Acidosis (decreased pH) decreases excitability, depressing neuronal activity.
44
Explain the clinical application of a ketogenic diet on epilepsy
Ketogenic diets will cause an increased in ketones, which is acidic and will lower the blood pH slightly, making seizures less likely to occur.
45
What happens as a synapse becomes fatigued?
Firing rate slows progressively.
Also explains why seizures usually can't last long (synapses become exhausted)
46
What natural substances affect synaptic transmission?
Caffeine, theophylline, and theobromine. They can increase neuronal excitability and reduce the threshold need to excite a neuron.
47
What drug affects synaptic transmission? (From lecture)
Strychnine.
Increases the excitability of neurons by inhibiting other inhibitory transmitters. (competes with glycine)
48
How do anesthetics affect synaptic transmission?
They increase the neuronal membrane threshold for excitation.
49
What kind of neurons make up the grey matter of the CNS?
Interneurons
50
What are the conscious sensory receptors of the body?
Proprioceptive, kinesthetic, temperature, light, sound, smell, taste, touch, and pain
51
What are the subconscious sensory receptors of the body?
Internal chemoreceptors, baroreceptors
52
What does the pyramidal tract of the spinal cord govern and what part of the spinal cord is it?
Skeletal muscle, controlling all purposeful movements.
It is the lateral tract of the spinal cord.
53
What are general signs of a pyramidal tract disorder/upper motor neuron syndrome?
Consistent motor signs, such as Hyperflexia, loss of ability to perform fine movements, or muscle wasting. Caused by damage typically to the descending motor pathways.
54
What are general signs of an extrapyramidal tract disorder?
Twitching/rolling motions. Incapable of standing still.
55
What are the two types of extrapyramidal tract disorders?
Akinetic rigid syndrome (Parkinsonism) and dyskinesias
56
Describe the process of a reflex arc.
Peripheral receptors send sensory input which go to interneurons in the spinal cord and relay information. The impulses then go to the efferent pathways (motor) to the effector organ.
57
Describe a motor unit
A motor unit is made up of a single alpha motor neuron that innervates multiple muscle fibers. The number of fibers depends on the muscle; eyes have 10 fibers/neuron while the gastrocnemius has 1800 fibers/neuron.
58
What is a motor pool?
All alpha motor neurons that project to a given muscle collectively.
59
Characteristics of a cross-sectional area of a motor unit
numbers of muscle fibers
size of muscle fibers
<10% of the variance in the maximum force generated among motor units in a motor pool
60
What is the size principle?
Within a single motor pool, the motor neurons will be recruited in order of ASCENDING size. Small first.
The larger the motor neuron, the more branches it has, the more it innervates, and the more force it generates.
61
What is the basis of the size principle?
Activation threshold of a motor neuron is inversely related to total surface area of the membrane of the motor neuron.
62
Compare and contrast slow twitch vs fast twitch fibers
Slow twitch fibers (Type 1) are red and have a lot of capillaries and mitochondria. They have a lot of endurance but low force. They are typically recruited first.
Fast twitch fibers (Type 2) are white and have minimal vascularization/mitochondria. However, they can generate a lot of force with low endurance. They are typically recruited last.
63
What are the mechanoreceptors of muscles?
Muscle spindle fibers and golgi tendon organs.
64
What is the goal of muscular mechanoreceptors?
Group sensory information to control and modulate the kinematics of movements in a predictable pattern, minimizing the need for conscious control of routine movements.
65
What are the two types of intrafusal fibers?
Nuclear bag fibers, located in the center of the fiber
Nuclear chain fibers, located across the whole length of a fiber
66
What motor neurons innervate muscle fibers and spindle fibers?
Alpha motor neurons innervate muscle fibers.
Gamma motor neurons innervate spindle fibers.
67
Compare and contrast primary spindle afferents with secondary spindle afferents.
Primary spindle afferents, also known as annulospiral endings, are used for dynamic changes in length and use Ia fibers to send information.
Secondary spindle afferents, also known as flower-spray endings, are used for static changes in length (Posture) and use group II fibers to send information.
68
What two events can cause stretch of intrafusal fibers?
Activation of the gamma motor neurons, which will shorten the distal ends of the fibers and stretch the center of the fibers.
Passively shortening/lengthening the fibers .
69
What is the purpose of a golgi tendon organ?
To detect small changes in force and to inhibit/contract muscles to prevent damage.
70
What 3 things can generate APs on the free nerve endings found in muscle?
Mechanical, biochemical, and metabolic stimuli.
71
What kind of sensations do free nerve endings detect?
Pain, it is a nocireceptor.
72
What kind of sensations does an expanded tip receptor detect?
It is a mechanoreceptor that detects tactile information such as touch.
73
What kind of sensations does a pacinian corpuscle detect?
It is a mechanoreceptor that detects deep pressure and vibration.
74
What kind of sensations does a meissner's corpuscle detect?
It is a mechanoreceptor that detects fine touch and vibration.
75
What kind of sensations does a krause corpuscle detect?
It is a thermoreceptor that detects cold.
76
What kind of sensations does ruffini's endings detect?
Sustained pressure
Found in the fingertips
Slow adaptation
77
What are the 3 layers of muscles?
Epimysium, perimysium, and endomysium
78
Define the structure of a muscle from superficial to deep.
Epimysium > Muscle > Perimysium > Fascicle > Endomysium > Muscle Fiber > Sarcolemma > Myofibril
79
What are the fundamental principles of ultrastructure?
Homeostasis, linkage between gene expression and physiology, and structure-function relationships.
80
Explain the process of muscle contraction.
1. An alpha motor neuron sends an AP down its axons to its muscle fibers.
2. The fiber receives the signal via acetylcholine and the sarcoplasmic reticulum is depolarized.
3. The sarcoplasmic reticulum propagates the signal and releases Ca2+
4. The influx of Ca2+ allows Ca to bind to the actin filament, exposing the tropomyosin binding site for the head of the myosin filament.
5. The myosin head, which has a cleave ADP and P group on it, now binds to the actin filament.
6. The release of the ADP and P causes the power stroke.
7. The addition of a new ATP and its cleavage allows the head to reset and reattach.
8. Contraction is possible as long as there is calcium still in the sarcoplasm.
81
What happens to the Z lines of the sarcomere as a muscle contracts?
The Z lines are drawn together towards the M band. Myosin filaments do not move during muscle contraction.
82
What factors influence muscle strength?
Pennation, cross-sectional area, fiber type, length of muscle, speed of contraction, and type of contraction.
83
What can cause muscle soreness?
Minute tears in muscle tissue or damage.
Osmotic pressure changes cause fluid retention in surrounding tissues
Muscle spasms
Overstretching and tearing of muscle's connective tissue harness.
Acute inflammation
Alteration in cell's mechanism for calcium regulation.
84
How long does soreness from lactic acid last?
1 hour usually.
85
What kind of receptors detect light and where are they found?
Electromagnetic receptors are found in the retina as rods and cones
86
What is the labeled line principle?
Nerve fibers only transmit impulses to their specific area, which is how senses are differentiated.
87
What does a higher receptor potential translate to as action potentials?
A higher receptor potential causes an increased FREQUENCY of action potentials.
88
What does the graph of stimulus intensity to receptor potential look like usually?
Like a logarithmic graph, where the receptor potential eventually plateaus and increases little. This allows the receptor to be sensitive but prevents it from hitting the maximum unless the stimulus is extreme.
89
What kind of receptor ending adapts instantly to a continuous stimulus?
Pacinian corpuscle
90
What is a tonic receptor?
Continually transmits impulses to the brain as long as a stimulus is present. Allows the brain to stay aware.
91
What are examples of tonic receptors?
Muscle spindles, GTOs, pain receptors, chemoreceptors, and baroreceptors.
92
What are rate/phasic receptors?
Stimulated when a stimulus changes. They react very strongly when a change occurs.
93
What is an example of a phasic receptor?
Pacinian corpuscles. It transmits the impulse when it is pressed, and will not transmit a new one until the pressure is increased or released.
94
What is the nerve fiber classification for aching pain?
C
95
What is the nerve fiber classification for a secondary muscle spindle fiber?
A beta
96
What is the nerve fiber classification for pricking pain?
A gamma
97
What is the nerve fiber classification for vibration and high discrimination touch?
A beta
98
What is the nerve fiber classification for a GTO and primary muscle spindle?
A alpha
99
Group 1a fibers
Annulospiral endings, or A alpha
100
Group 1b fibers
GTO fibers, or A alpha
101
Group 2 fibers
discrete cutaneous tactile and flower-spray endings, or beta and delta fibers
102
Group 3 fibers
Temperature, crude touch, and pricking pain, or gamma fibers
103
Group 4 fibers
unmyelinated fibers carrying pain, itch, temperature, and crude touch, type C fibers
104
How do free nerve endings work in regards to their receptor fields?
Free nerve endings generate a receptor field, which includes many fibers.
Increasing signal strength is seen based on the number of fibers stimulated and their proximity to the center of that field.
105
What is a stimulatory field?
The neuronal area stimulated by an incoming nerve fiber. The farther away a nerve fiber is, the fewer terminals it stimulates.
106
What is a suprathreshold stimulus?
A stimulus that is above the threshold required for excitation.
107
What is divergence and why is it important?
A signal can be split up and multiplied, or it can diverge into multiple different tracts. This allows for a single signal to affect many tracts.
108
What is convergence and why is it important?
Multiple inputs coming together to excite a single neuron, either from a single source repeating or from multiple. This makes it so a single signal does not cause a stimulus.
109
What is a reciprocal inhibition circuit and why is it important?
A single fiber can go to an excitatory synapse and inhibitory synapse simultaneously. This occurs in muscles, such as the quads contracting while the hammies relax.
110
What are the three ways a signal can be prolonged?
Afterdischarge, reverberatory circuit, or rhythmical outputs
111
Why is inhibition important for the nervous system?
Prevents overexcitation.
Signal dampening
Preventing fatigue
Occurs through up/down regulation of synaptic receptors.
112
What are the five skin tactile receptors?
Free nerve endings: touch and pressure
Expanded tip endings such as Merkel's disc: sensitive touch and texture
Ruffini's endings: multi-branched, encapsulated endings that adapt very slowly.
Meissner's corpuscles: encapsulated endings that are found on spatial locations of touch, like lips or fingertips.
Hair-end organs: any hair on the body, sensing the movement of objects near the body.
113
What are the five deep tissue receptors?
Free nerve endings
Expanded tip endings
Ruffini's endings
Encapsulated endings: pacinian corpuscles
Muscle endings: Spindles and GTOs
114
How do sympathetic nerve fibers go to their respective organs?
They come from the vertebrae levels and go to the sympathetic chain, where they either go up/down on the chain, go to a ganglion, or go straight to a organ.
115
What are the two prevertebral sympathetic ganglia?
Celiac and Superior/Inferior Mesenteric (hypogastric?)
116
What is the pathway of preganglionic sympathetic neuron?
Lateral horn to anterior root to spinal nerve to sympathetic chain.
117
What are the two cholinergic sympathetic postganglions?
Sweat, pilo erectors, and some blood vessels.
118
What is the primary cranial nerve for parasympathetic innervation?
Vagus Nerve (75%)
119
What CNs have parasympathetic innervation?
3, 7, 9, and 10, going from the head or from the sacrum.
120
Where are ganglions found in the parasympathetic?
Only at the head level. All other fibers go direct.
121
Compare and contrast preganglionic and postganglionic fibers in the sympathetic vs parasympathetic
Parasympathetic preganglionic neurons are much longer. Their postganglionic neurons are in the walls of the organs. All parasympathetic neurons are cholinergic.
Sympathetic preganglionic neurons are short. Their postganglionic neurons are much longer. All sympathetic have preganglionic cholinergic, but most are postganglionic adrenergic.
122
What are the 5 types of adrenergic receptors?
Alpha 1, Alpha 2, Beta 1, Beta 2, Beta 3
123
What is the difference between norepi and epi stimulation of adrenergic receptors?
Epinephrine stimulates beta receptors more than norepinephrine.
124
What are the two types of cholinergic receptors?
Muscarinic and Nicotinic Receptors
125
Where are muscarinic receptors found?
Found on all effector cells that are stimulated by postganglionic cholinergic neurons on both systems.
DUMBBELS (effect of muscarinic agonist)
126
Where are nicotinic receptors found?
Found in the autonomic ganglia at the synapse between pre and post of both systems.
Ganglions and skeletal muscle.
127
Where are adrenergic receptors found?
Alpha 1 is found in peripheral vascular smooth muscle
Alpha 2 is found in the spinal cord, acts on regulate sympathetic input from CNS to PNS
Beta 1 is cardiac and smooth muscle
Beta 2 is bronchial tree and visceral organs.
128
What are the effects of alpha agonists?
vasoconstriction, iris dilation, intestinal relaxation, intestinal sphincter contraction, pilomotor contraction, bladder sphincter contraction, and inhibits neurotransmitter release (alpha 2)
129
What are the effects of beta agonists?
Beta 1: cardioacceleration, increased myocardial strength, and lipolysis.
Beta 2: Vasodilation, intestinal relaxation, uterus relaxation, bronchodilation, calorigenesis, glycogenolysis, bladder wall relaxation
Beta 3: thermogenesis
130
Compare and contrast fast pain vs slow pain
.1s after stimulus vs 1s
Fast is generally not felt in deep tissues.
131
Double pain sensation
Fast pain occurs instantly, glutamate is the neurotransmitter.
Slow pain occurs slowly and substance P is the neurotransmitter.
132
In what internal tissues do I find free nerve endings?
Periosteum, Arterial walls, joint surfaces, and the cranial vault.
133
What stimuli is part of slow pain?
Mechanical, thermal and chemical, such as bradykinin or acids.
134
What is hyperalgesia?
Increased sensitivity of pain receptors.
135
What receptors are usually non-adapting?
Pain receptors generally do not adapt because the body wants you to remove yourself from the stimulus.
136
At what temperature do we begin to perceive pain?
45C or 113F. Rate of damage is correlated to the intensity of pain.
137
How does ischemia cause pain?
Accumulation of lactic acid in tissue.
Bradykinin + Proteolytic enzymes
These directly attack the nerve endings and excite pain by making the nerve membranes more permeable to ions.
138
What is the basis of clinical pain syndromes?
Mechanosensitive pain receptors or ischemia due to muscle spasms compressing blood vessels.
139
What is the analgesia system of the brain?
It is the capability of the brain itself to suppress input of pain signals.
140
What is enkephalin?
Causes the pre and post inhibition of incoming C fibers and A delta fibers.
141
What does morphine do?
Blocks pain without causing drowsiness. Enkephalins and endorphons all act on morphine receptors.
142
What is referred pain and the cause?
On the spinal cord, second order neurons can receive pain signals from skin receptors, but visceral fibers can be conducted via the same neurons.
143
What kinds of stimulus can cause visceral pain?
Ischemia of tissue
Chemical damage to the surfaces
Spasms of the smooth muscle
Excess distention of hollow viscus
Stretching of surrounding connective tissue
144
What visceral pain is always chronic/aching?
Thoracic and abdominal cavities only contain type C fibers, so only aching pain can be transmitted.
145
What viscera are insensitive to pain?
Parenchyma of the liver and alveoli.
146
What is the difference between primary and secondary hypersensitivity to pain?
Primary is excessive sensitivity of the pain receptors themselves.
Secondary is increased facilitation of sensory transmission.
147
What usually causes headaches?
Sinus agitation, meningeal stretching, or connective tissue stretching. Brain tissue is insensitive to pain.
148
What are the types of intracranial headaches?
Headache due to meningitis
Headache due to low CSF
Migraine due to abnormal vascular phenomenon. Usually includes a prodromal phase 30 minutes prior, with symptoms of nausea, loss of vision, or visual aura.
149
What are the causes of extracranial headaches?
Muscle spasms
Irritation of nasal structures
Eye disorders involving eye muscles.
150
What stimuli is part of fast pain?
Mechanical and thermal
