Test 1 (Lectures 1-7, 8a) Flashcards
1
Q
The five questions of neural science?
A
- How does the brain develop?
- How do nerve cells in the brain communicate with each other?
- How do different patterns of interconnections give rise to different perceptions and motor acts?
- How is communication between neurons modified by experience?
- How is that communication altered by disease?
2
Q
How many individual nerve cells are in the human brain?
A
Over 100 billion
3
Q
Reducing the elements of a system to a basic level of functioning elements?
A
Reductionism
4
Q
Knowledge of the elements essential to understanding the system but greater emphasis is placed on investigating and understanding the system as a whole
A
Complex System Approach
5
Q
This approach allows for a more succinct description of behavior and the interpretation
A
The Complex System Approach
6
Q
Why are membranes partially permeable?
A
Helps them regulate the influx and efflux of ions
7
Q
Three major types of substances that can cross membranes
A
Solvents
Electrolytes
Non electrolytes
8
Q
Example of a solvent
A
Water
9
Q
Example of an electrolyte
A
Ions
10
Q
Example of a nonelectrolyte
A
Non-charged molecules
11
Q
High pressure to low pressure
A
Convection
12
Q
High concentration to low concentration
A
Diffusion
13
Q
Movement of a solute based on a pressure
A
Convection
14
Q
Movement of the concentration of particles within a solution.
A
Diffusion
15
Q
Movement of a solvent (water) and solutes from an area of high pressure to an area of low pressure.
A
Convection
16
Q
The movement of particles dissolved in a solvent from an area of high concentration to an area of low concentration
A
Diffusion
17
Q
This creates a difference of potentials that induces a flow of charged particles
A
An electric field
18
Q
Movement of a solvent (water) and solutes from an area of high pressure to an area of low pressure.
A
Convection
19
Q
The movement of particles dissolved in a solvent from an area of high concentration to an area of low concentration
A
Diffusion
20
Q
This creates a difference of potentials that induces a flow of charged particles
A
An electric field
21
Q
The 2 forces that ion movement is influenced by
A
Concentration
Difference of potentials
22
Q
Movement of charged particles (ions) under the action of a difference of potentials
A
Electric current
23
Q
Movement of water (solvent) from an area of low solute concentration to an area of high solute concentration; the total concentration of particles matter
A
Osmosis
24
Q
Low concentration to high concentration
A
Osmosis
25
Allow certain substances across, but not others
Membrane channels
26
Movements of all particles are counterbalanced in this state
Equilibrium
27
3 properties of ion channels
1. They conduct ions
2. They recognize specific ions
3. They open and close in response to specific electrical, mechanical, or chemical signals
28
How many ions can pass through a channel per second
Up to 100 million ions
29
What is the difference in electrical potential across the membrane known as?
Resting membrane potential
30
Resting membrane potential of neurons are around
-60 mV to -70 mV
31
Regenerative electrical signal in which the amplitude does not attenuate as it moves up or down the axon
Action potential
32
This allows for a much more rapid pace than convection or diffusion
Action potential
33
Communication based on this is far greater than that of diffusion or convection
Membrane potential
34
Maintains ion concentration gradients across the membrane
Sodium-potassium pump
35
The three ions that play an active role in the electric capabilities of a system and influence neural communication
Sodium (Na+)
Potassium (K+)
Chloride (Cl-)
36
How can an electric potential emerge by itself?
If a membrane separates two areas with and without Na+ and Cl- ions, diffusion of the ions will occur from the area of high concentration to low concentration
37
Do different ions diffuse at the same rate?
No
38
These store electrical charges and electrical potentials
Capacitors
39
The membrane can be considered a
Capacitor
40
The dispersion of an electrical signal
Action potential
41
Small stimulus leads to
A small response
42
Medium stimulus leads to a
Medium response
43
Large stimulus leads to
A large response
44
An action potential can only occur when
The stimulus is strong enough to depolarize the membrane beyond the membrane potential
45
When the stimulus leads to depolarization of the membrane potential to the point of generating an action potential, an action potential will be generated. Increasing stimulus intensity will not lead to an increase in the generation of the action potential.
All or none principle
46
Negative movement away from the threshold
Hyperpolarization
47
Positive movement towards the threshold
Depolarization
48
The size and shape of every action potential is always
The same
49
Either the membrane doesn't generate an action potential or it generates an action potential with a standard shape and magnitude.
All or none principle
50
A membrane's resting potential will change somewhat in response to a small stimulus before
Returning to its resting level
51
The period after an action potential where the possibility of generating another action potential is reduced or not possible
Refractory period
52
The period following an action potential in which it is possible to generate another action potential
Relative refractory period
53
The period following an action potential in which it is not possible to generate another action potential
Absolute refractory period
54
This leads to a rapid amplification of the effect
Positive feedback
55
The leads to a restoration of the original state
Negative feedback
56
Depolarization
Positive feedback
57
Hyperpolarization
Negative feedback
58
This does not allow an action potential to "backfire"
Inactivation of sodium channels
59
In nerve fibers, larger diameters
result in signals traveling faster
60
An enclosed sheath of non-neural (glial) cells covering neurons
Myelinated fiber
61
Breaks in myelin sheath
Ranvier nodes
62
Where action potentials are generated in neurons
Ranvier nodes
63
5 steps of action potential conduction
1. Membrane depolarization to the threshold.
2. Generation of an action potential.
3. Local currents spread passively.
4. They depolarize adjacent areas of the membrane.
5. A new action potential is generated.
64
This increases the effective distance of local currents in neurons
Myelin
65
Velocity of conduction in myelinated fibers in m/s
6 x d(m)
66
These two things prevent action potentials from backfiring
Absolute refractory period
| Inactivation of sodium channels
67
The biggest and fastest neurons in the body
Sensory types IA and IB
68
This type of neuron is not far behind the biggest and fastest neurons in the body
Motor type Aa.
69
Conduction from the soma to terminal branches
Orthrodromic conduction
70
Conduction from the end of the axon to the soma
Antidromic conduction
71
These neurons are orthrodromic
Motor neurons
72
These neurons are antidromic
Sensory neurons
73
Body of the cell; the site of input signals
Soma
74
Short branches originating from the soma; sites of inputs
Dendrites
75
A long branch; transmits output signals
Axon
76
The site where the axon exits the soma; typically, the site of generation of action potentials
Axon hillock
77
A "brush" at the end of the axon
Terminal branches
78
A fatlike substance covering the axon; it increases the speed of conduction of action potentials
Myelin
79
Breaks in the myelin sheath; places where action potentials are generated
Ranvier nodes
80
Many axons running together
Nerve (peripheral) or neural tract (central)
81
Are there ion channels under the myelin sheath?
No
82
Are there ion channels in the Ranvier nodes?
Yes, there are many ion channels
83
Each action potential transmits
1 bit of information
84
How can a neuron encode significant amounts of information?
By generating sequences of action potentials.
- By changing the frequency of firing
- Neuron take into account the timing and number of action potentials
85
What does a synapse consist of?
A presynaptic membrane, a synaptic cleft, and a postsynaptic membrane
86
These change the potential of the postsynaptic membrane
Neurotransmitters
87
An action potential in a presynaptic fiber makes synaptic vesicles move to the membrane, fuse with it, and release molecules of neurotransmitters into the cleft.
Conduction of a signal across the synapse
88
Types of synapses
Obligatory synapse
| Non-obligatory synapse
89
1/1 ratio
Obligatory synapse
90
Not 1/1 ratio
Non-obligatory synapse
91
Action potential on the presynaptic membrane always give rise to an action potential on the postsynaptic membrane
Obligatory synapse
92
A single action potential on the presynaptic membrane is typically unable to induce an action potential on the postsynaptic membrane
Non-obligatory synapse
93
Excitatory Post Synaptic Potential (EPSP)
Depolarization
94
Inhibitory Post Synaptic Potential (IPSP)
Hyperpolarization
95
Synaptic transmission
1. A presynaptic action potential arrives.
2. The presynaptic membrane lets vesicles with molecules of neurotransmitters pass through.
3. The vesicles release the neurotransmitters into the synaptic cleft.
4. The molecules diffuse across the cleft to the postsynaptic membrane and act at special sites (receptors).
5. The postsynaptic membrane is either depolarized or hyperpolarized.
6. The whole process takes 0.5 ms.
96
Several action potentials arrive at a presynaptic membrane at intervals that do not allow individual EPSPs to disappear.
Their effects can sum up and induce an action potential.
Temporal summation
97
Several action potentials arrive simultaneously at different synapes on the same presynaptic membrane so that their EPSPs sum up and can induce an action potential.
Spatial summation
98
Temporal and spatial summation can occur for both
EPSPs and IPSPs
99
Components of skeletal muscle
Sarcolemma
Sarcoplasm
Myofilaments
Sarcoplasmic reticulum
100
Contains myofilaments and sarcoplasmic reticulum
Sarcoplasm
101
Contains the sarcoplasm
Sarcolemma
102
The two filaments that bind two form cross-bridges
Actin and myosin
103
Smallest functioning unit of skeletal muscle
Sarcomere
104
How is movement created?
A signal from the CNS is sent to the muscle to cause movement
105
How does the neuromuscular synapse work?
A presynaptic nerve action potential induces movement of vesicles with acetylcholine (ACh) to the presynaptic membrane, their fusion, and release of ACh into the cleft
ACh diffuses to the postsynaptic muscle membrane, depolarizers it, and induces an action potential.
106
The specialized region of muscle membrane that received the neurotransmitters
Motor end plate
107
The neurotransmitter of the neuromuscular synapse
Acetylcholine (ACh)
108
A synaptic potential is produced in the neuromuscular synapse of around
70 mV
109
Always excitatory
Neuromuscular synapse
110
Obligatory
Neuromuscular synapse
111
Does not have multiple innervations
Neuromuscular synapse
112
ACh in the synaptic cleft is destroyed by
AChesterase
113
Miniature excitatory postsynaptic potentials that spontaneously occur in the postsynaptic muscle membrane
Motor End Plate Potentials (MEPP's)
114
Are around - 1 mV
Motor End Plate Potentials
115
Functional meaning is unclear
MEPP's
116
This always reaches depolarization threshold and induces a muscle action potential
A presynaptic nerve action potential
117
How are Ca++ ions released
Muscle action potential travels along the sarcolemma, enters T-tubules, and leads to a release of Ca++ ions from the sarcoplasmic reticulum
118
Ca++ ions remove tropomyosin and frees a site for myosin to bind to troponin (this process uses energy from ATP). A ratchet motion occurs, moving the filaments with respect to each other.
Sliding Filament Theory
119
Muscle can only
Contract.
120
Muscle cannot
Flex or extend
121
The delay between the electrical signal and the production of force
Latent period
122
A single muscular contraction in response to a single stimulus
Muscle twitch
123
Time sensitive
Temporal
124
Two action potentials come at a short interval and induce two twitch contractions. Their mechanical effects are superimposed, leading to a higher level of muscle force
Temporal summation
125
A sequence of action potentials may lead to a smooth contraction.
Tetanus
126
Encapsulates a single fascia
Endomysium
127
Encapsulates the endomysiums
Perimysium
128
Encapsulates the perimysiums
Epimysium
129
The Y axis of the force-velocity curve
Represents the velocity of muscle shortening
130
The muscle produces higher forces when it is
Lengthening
131
Negative velocity
The muscle is lengthening
132
Positive velocity
The muscle is shortening
133
A muscle always works against
A load
134
Three types of loads
Isometric
Isotonic
Elastic
135
Prevents changes in "muscle plus tendon"
An isometric load
136
Load does not change
Isotonic
137
Load acts like a spring
Elastic
138
Muscle develops force while shortening
Concentric
139
A muscle develops force while lengthening
Eccentric
140
The "muscle plus tendon" length does not change
Isometric
141
The apparent external load does not change
Isotonic
142
The load is a spring
Elastic
143
External loads
Isometric
Isotonic
Elastic
144
These allow dendrites to start generating action potentials and continue to do so without any external stimuli as long as the membrane potential stays above threshold
Persistent Inward Currents
145
A depolarizing inward current that activates as long as the membrane potential is depolarized
Persistent inward currents
146
Allows for an increase in the number of action potentials that are generated
Persistent inward currents
147
Very sensitive to postsynaptic inhibition
Persistent inward currents
148
Likely strong enough to play a major role in defining the patterns of recruitment and derecruitment of motor units
Persistent inward currents
149
Not all synapses are chemical
Some electrical
150
Provide a low resistance pathway for the electrical current to flow between cells
Gap junction cells
151
Current flows from presynaptic cell into the postsynaptic cell, depositing a positive or negative charge
Electrical synapse
152
If deplorization in the postsynaptic cell exceeds threshold,
The postsynaptic cell will generate an action potential
153
Very little synaptic delay
Electrical synapse
154
Can transmit both depolarizing and hyperpolarizing currents
Electrical synapse
155
Located between glial and Schwann cells in the brain
Electrical synapse
156
Likely involved in brain signaling and myelin formation
Electrical synapse
157
The three types of perception
Exteroception
Interoception
Proprioception
158
Perception involving vision, hearing, smell, touch
Exteroception
159
Perception involving internal objects and organs
Interoception
160
Perception of the position of body parts
Proprioception
161
The body of a sensory neuron is located in a
Ganglion near the spinal cord
162
In a sensory neuron, one branch of the T-shaped axon goes to the _____ ______ ______, and another branch goes through the _______ ______ into the spinal cord
Peripheral sensory ending, dorsal roots
163
Perceived sensation is _______ as it relates to stimulus intensity.
Logarithmic
164
Logarithmic
The size of the stimulus = the size of the sensation
165
Body is a long T-shaped axon, and sensory ending
Proprioceptor Neuron
166
Body is in spinal ganglia or dorsal side
Proprioceptor Neuron
167
Proprioceptor neurons conduct things primarily in this manner
Antidromic conduction
168
No dendrites, no synapses on the body
Proprioceptor neurons
169
How are muscle spindles oriented?
Parallel to extrafusal muscle fibers
170
Where are primary endings of muscle fibers seen?
In virtually all intrafusal fibers
171
Secondary endings of muscle spindle are not seen in
Dynamic bag fibers
172
Efferent motor fibers are also called
Gamma motor neurons
173
Three components if muscle spindles
Intrafusal muscle fibers
Efferent sensory fiber endings
Efferent motor fiber endings
174
Th central region of these muscle fibers are non contractile
Intrafusal fibers
175
These fibers spiral around the central region of the intrafusal fibers, and respond to stretching of the intrafusal fibers
Efferent sensory fibers
176
These motor neurons are much smaller than alpha motor neurons
Gamma motor neurons
177
These innervate the contractile polar region of the intrafusal fibers
Gamma motor neurons
178
When a gamma motor neuron activates an intrafusal fiber, it will contract. What does this do?
It increases the intrafusal fiber's sensitivity to stretch
179
The three types of intrafusal fibers
Dynamic bag fibers
Static bag fibers
Chain fibers
180
Innervated by a single primary (Ia) sensory ending. Also innervated by a dynamic gamma motor neuron
Dynamic bag fiber
181
Innervated by a single primary (Ia) sensory ending and a secondary (II) ending. Also innervated by a static gamma motor neuron.
Static bag fibers and Chain fibers
182
The primary ending of a muscle spindle response to stretching increases with
Muscle length and stretch velocity
183
The spindle response to stretch concerning the secondary ending
The response increases with muscle length, but does not depend velocity
184
The two types of small motor neurons that innervate intrafusal fibers in muscle spindles
Dynamic motor neurons
| Static motor neurons
185
These motor neurons innervate dynamic bag fibers and change the sensitivity of primary endings
Dynamic motor neurons
186
These motor neurons innervate static bag fibers and chain fibers. They change the sensitivity of primary and secondary endings.
Static motor neurons
187
Primary endings of muscle spindle are
Sensitive to length and velocity of muscle fibers
188
Secondary endings of muscle fibers are
Sensitive only to length of muscle fibers
189
These innervate intrafusal muscle fibers
Gamma motor neurons
190
A system to modify sensitivity of the spindle endings
Gamma motor neurons
191
Located in a series of extrafusal muscle fibers at their junction with the tendon
Golgi tendon organs
192
Innervated with fast conducting Ib axons of sensory neurons in spinal ganglia
Golgi tendon organs
193
Located in the junction between muscle fibers and the tendon
Golgi tendon organs
194
Are considered to be in a series with a group of muscle fibers
Golgi tendon organs
195
Sensitive to changes in muscle tension
Golgi tendon organs
196
Are not sensitive to changes in length, only tension
Golgi tendon organs
197
Not innervated by gamma motor neurons
Golgi tendon organs
198
Provide feedback about joint position
Articular receptors
199
Most fire in rather narrow ranges of joint angle, mostly close to the anatomical limits
Articular receptors
200
Articular receptors increase their response when
An increase in muscle force leads to an increase in joint capsule tension
201
A passive sensory ending sensitive only to tendon force
Golgi tendon organ
202
Sensitive to joint angle close to the anatomical limits of joint rotation
Articular receptors
203
Sensitive to joint capsule tension
Articular receptors
204
Cutaneous and subcutaneous receptors
Merkel disks
Meissner corpuscles
Ruffini endings
Pacinian corpuscles
205
This receptor measures vertical pressure
Merkel disks
206
This receptor measures quickly changing pressure
Meissner corpuscles
207
This receptor measures deformation of large skin areas
Ruffini endings
208
This receptor measures rapidly changing mechanical deformation
Pacinian corpuscles
209
Afferent nerves from the peripheral receptors go into
The spinal cord through the dorsal roots
210
Once in the dorsal roots of the spine, synapses occur on
The interneurons and motor neurons (only primary spindle endings)
211
After synapsing with the interneurons and motor neurons,
Signals are sent to the brain
212
These induce changes in muscle activity that bypass consciousness
Proprioceptors
213
Tell us where our arms and legs are and how heavy or light, or rough or soft the objects we handle are
Proprioceptors
214
Help create an internal reference system the brain uses to plan and execute movements
Proprioceptors
215
These motor neurons send their axons from the ventral roots of the spinal cord.
Alpha motor neurons
216
The axons branch in a target muscle, and each axon innervates several muscle fibers
Alpha motor neuron
217
What is a motor unit?
An alpha motor neuron and the muscle fibers it innervates
218
The three main types of motor units
1. Slow twitch, fatigue resistant (small)
2. Fast twitch, fatigue resistant (larger)
3. Fast twitch, fatigable (large)
219
Fiber diameter of fast twitch, fatigable
Large
220
Fiber diameter of fast twitch, fatigue resistant
Medium
221
Fiber diameter of slow twitch
Small
222
Size principle (Henneman Principle)
Small motor units are recruited first at low muscular forces. An increase in muscle force leads to recruitment of larger motor units
223
How can the CNS increase muscle force?
By recruiting new motor units and/or increasing the firing frequency of already recruited motor units.
224
Measures the electrical activity (action potentials) associated with muscle contraction
Eletromyography (EMG)
225
Has uses both clinically and in research
EMG
226
Beneficial for reflex testing
EMG
227
Very useful for measuring reaction time or muscle latency, when muscles turn on and off
EMG
228
Uses thin needle electrodes.
Intramuscular EMG
229
The difference of potentials between the tip of the wire and the tip of the needle is amplified and recorded
Intramuscular EMG
230
This form of EMG records the activity of individual motor units
Intramuscular EMG
231
This form of EMG is uncomfortable
Intramuscular EMG
232
Provides information about excitation of a small volume within a muscle
Intramuscular EMG
233
Uses a pair of electrodes placed on a muscle belly with a third electrode (ground) to reduce noise.
Surface EMG
234
How are action potentials recorded with surface EMG?
An action potential runs under a pair of electrodes. The difference of potentials recorded by the electrodes will change is sign (the upper record).
235
Making all the values of the difference of potentials positive
Rectification
236
Averages the activity of many (all) motor units
Surface EMG
237
Causes no discomfort
Surface EMG
238
Is not selective
Surface EMG
239
Has a laminar structure
Spinal cord
240
Forms a characteristic butterfly picture at each level of the spinal cord
Gray matter
241
Toward the head
Rostral
242
Toward the tail
Caudal
243
Toward the back
Dorsal
244
Toward the front
Ventral
245
Toward the center of the body or point of attachment
Proximal
246
Away from the center of the body or point of attachment
Distal
247
Has a body and a spinous process
Vertebra
248
Is sent through the dorsal roots of the spinal cord
Peripheral information
249
Is sent through the ventral roots of the spinal cord
Efferent signals
250
The numbering of the vertebrae
C1 to C7
T1 to T12
L1 to L5
251
The numbering of spinal segments
C1 to C8
T1 to T12
L1 to L5
S1 to S5
252
This spinal segment ends above the vertebrae
C1
253
This spinal segment ends below vertebrae C7
C8
254
From this spinal segment on, all spinal segments are lined up with the corresponding vertebra.
T1 on
255
What does a synapse consist of?
A presynaptic membrane
A synaptic cleft
A postsynaptic membrane
256
A decrease in the efficacy of the synapse
Inhibition
257
May occur as a result of events on the presynaptic or postsynaptic membrane
Inhibition
258
Leads to a depolarization of the postsynaptic membrane
An excitatory synapse
259
Leads to a hyperpolarizatoin of the postsynaptic membrane
An inhibitory synapse
260
When one neuron hyperpolarizes the cell body (or dendrites) of another cell body
Postsynaptic inhibition
261
Will hyperpolarize the entire membrane, essentially shutting down that cell for a period of time to all incoming stimuli
Postsynaptic inhibition
262
A more general type of inhibition
Postsynaptic inhibition
263
This synapse hyperpolarizes the postsynaptic membrane and decreases it responsiveness to excitatory synapses
A postsynaptic inhibitory synapse
264
Branch very close to the cell body and make excitatory synapses on Renshaw cells
Axons of alpha motorneurons
265
Make inhibitory synapses on alpha motornuerons of the same pool and on gamma motorneurons
Renshaw cells
266
Are inhibitory in nature
Renshaw cells
267
Alpha motorneurons excite Renshaw cells that inhibit the same alpha motorneurons
Recurrent Inhibition
268
Benefits of recurrent inhibition
Helps regulate the amount of force produced by the muscle
269
Helps to stabilize the firing rate of motor neurons
Renshaw cells
270
Renshaw cells are also innervated by
Descending signals
271
These neurons are in the spinal cord
Interneurons
272
Ia interneurons receive excitatory inputs from
Ia afferent neurons
273
Make inhibitory synapses on motorneurons innvervating the antagonist muscle.
Ia interneurons
274
Are inhibited by Renshaw cells and also receive descending inputs
Ia interneurons
275
Inhibits motorneurons of the same pool
Recurrent inhibition
276
Inhibits motorneurons of the antagonist muscle
Reciprocal inhibition
277
The steps of recurrent inhibition
1. Alpha-motorneurons of a pool fire.
2. They send axon branches to Renshaw cells in the ventral horns of the spinal cord.
3. Renshaw cells inhibit all motorneurons of the same pool.
278
The steps of reciprocal inhibition
1. Small (Ia) interneurons are activated by primary spindle (Ia) afferent fibers.
2. The Ia interneurons inhibit motorneurons of the antagonist muscle.
279
Ia interneurons can be inhibited by ______ _____ to stop reciprocal inhibition.
Renshaw cells
280
When a neruon contacts the axon terminal, rather than the cell body, of another neuron.
Presynaptic inhibition
281
This will reduce the amount of neurotransmitter released by the second neuron onto the third cell
Presynaptic inhibition
282
This is a more specific or selective form of inhibition
Presynaptic inhibition
283
Acts selectively on certain synapses
Presynaptic inhibition
284
How does presynaptic inhibition work?
An excitatory synapse acts on the presynaptic membrane and induces a steady subthreshold depolarization. This decreases the amount of neurotransmitter released in response to one presynaptic action potential.
285
Definition of a reflex
A muscle contraction induced by an external stimulus that cannot be changed by pure thinking
286
Are highly adaptable to changes in behavior goals, mainly because several different circuits exist to connect sensory and motor neurons
Reflexes
287
Cannot be directly controlled voluntarily
Reflexes
288
Stereotyped responses to specific stimuli that are generated by simple neural circuits in the spinal cord or brain stem
Reflexes
289
One central synapse
Monosynaptic
290
A few central synapses, usually 2 to 3
Oligosynaptic
291
Many central synapses
Polysynaptic
292
Slow, steady-state, maintained
Tonic
293
Fast, transient, in response to a change in stimulus
Phasic
294
Have no higher brain involvement
Reflexes
295
Value of studying reflexes
Can assist in diagnosis of certain conditions
| Help localize injury or disease in CNS
296
Often indicate a disorder in one or more of the components of the reflex arc
Absent or hypoactive reflexes
297
Can cause both hyperactive and hypoactive reflexes
Lesions in the CNS
298
Most common form of hyperactive reflexes
Spasticity
299
results in increased muscle tone
Spasticity
300
5 components of a reflex arc
1. Sensory element (receptor)
2. Afferent (sensory) nerve
3. Central processing unit
4. Efferent (command) nerve
5. Effector (muscle)
301
3 components of the reflex latency
1. Afferent conduction delay
2. Central processing delay
3. Efferent conduction delay
302
Involves one central synapse
Monosynaptic reflex
303
Originates from Ia spindle afferents and induces a response in the same muscle or in muscles in the vincinity
Monosynaptic reflex
304
Technique for examining monosynaptic reflexes developed in the 1950s by P. Hoffman
H-reflex
305
Involves electrical stimulation of Ia afferents in a peripheral nerve and recording the motor (reflex) response in the same muscle
H-reflex
306
Commonly assessed by stimulating the tibial nerve and measuring the response of the soleus
H-reflex
307
In H-reflexes, the stimulation is applied to
both afferent and efferent fibers
308
A further increase in the strength of the stimulation leads to
An increase in the M-response and suppression of the H-relfex
309
How a H-reflex works
Afferent fibers are the first to react to a slowly increasing electrical stimulus. They induce a reflex muscle contraction (H-reflex). Later, efferent fibers become excited and induce a direct muscle contraction (M-response).
310
The peak-to-peak amplitude of the H-reflex and the M-response depends on
The strength of the stimulation applied to a muscle nerve
