Exam 1 Flashcards
1
Q
where are the cell bodies of motor neurons located?
A
grey matter of the spinal cord
2
Q
where are cell bodies of sensory neurons located?
A
dorsal root ganglia
3
Q
where are axons/ sensors of sensory neurons?
A
out in the limb (ex. hand)
4
Q
what are the type of cell bodies in the grey matter ?
A
inner neurons (form reflex circuits) and motor neurons
5
Q
why is grey & white matter so small in sacral area of spinal cord
A
grey matter: only requires very gross motor muscle movements (opening and closing sphincters) nothing related to fine motor control.
white matter: we need to feel sensations here, but doesn’t need to be fine control where we can distinguish fine things. also end of the spinal cord so we don’t have a lot that needs a ascend to the brain. descending track doesn’t need a lot of neurons because minimal tasks required
6
Q
function of corpus collosum
A
connects right and left hemisphere of the brain
7
Q
where in the spinal cord to axons of sensory neurons enter?
A
dorsal horn through the dorsal root
8
Q
where do cell bodies of motor neurons reside in the grey matter
A
ventral horn
9
Q
where do the axons of motor neurons exit the ventral horn of spinal cord
A
ventral root
10
Q
what do nerve rootlets merge to become
A
roots
11
Q
what do nerve roots merge to become
A
nerves
12
Q
a motor nucleus can extend over how many spinal segments?
A
1-4
13
Q
what are the two types of cells in the nervous system
A
nerve cells (neurons - excitable) and glial cells (support neurons)
14
Q
what are the four types of glial cells
A
- oligodendrocytes
- schwann cells
- astrocytes
- microglia
15
Q
what are the function of astrocytes
A
help to form blood brain barrier by connecting end feet to envelope capillaries. this separates them from neurons. capillary walls in brain are make from epithelial cells that make tight junctions
16
Q
what is the schwann cell ?
A
wraps itself around the neuron in the PNS (using phosolipid bilayers - hydrophoic) to protect the electrical conduction through cell
17
Q
where are oligodendrocytes located?
A
myelinate the neurons in the Central Nervous system
18
Q
where is information gathered on a neuron?
A
synapses at dendrites (excitatory or inhibitory)
19
Q
where are inputs from dendrites summed and determine to make and AP or not?
A
axon hillock (maintains charge till told to generate AP)
20
Q
what is saltatory conduction
A
when the AP jumps from nod of ranvier to the next making the a quick reponse
21
Q
define membrane potential
A
potential exists when there is an imbalance in net charge across a membrane
22
Q
how does the Na+ K+ pump work
A
actively maintains membrane potential by pumping K IN and Na OUT
23
Q
what is the resting membrane potential
A
-65 mV (more negative on the inside than outside)
24
Q
how AP works
A
- membrane potential changes rapidly due to opening of ion channels (Na)
25
what is threshold at?
-55 mV where ion channels opening
26
whats happening at synapse between pre- and post synapse ?
when AP arrives causes vesicle to open and spill neurotransmitters and binds to post- synapse that causes ion channels to open
27
what is EPSP and IPSP
* excitatory post-synpatic potential
* inhibitory post-synpatic potential
28
what determines whether it is going to be an EPSP or IPSP
- what type of neurotransmitter binds to post synpase
29
is GABA a excitatory or inhibitory neurotransmitter?
inhibitory
30
is Glutamate excitatory or inhibitory?
excitatory
31
can a cell hold Glutamate and GABA in its vessicles?
No - one or the other
32
what effect does one action potential as it travels along post synaptic neuron to axon hillock
decreases in amplitude
33
what happens if you have multiple EPSP action potentials from pre-synpase?
causes summation (temporal)
34
what is temporal summation
rapid occurrence of EPSP or IPSP at one synapse
35
what is compound EPSP
all together (all APs)
36
what is the functional model of afferent and efferent signals
1. external stimulus
2. external sense organ detects stimulus OR internal stimulus
3. travels to nerve ending -> axon terminal -> to spinal cord and/or brain
4. efferent signal from brain or spinal cord travels to dendrites -> axon terminals connected to muscular fiber
37
what ion channel is in high density at axon hillock
voltage gated
38
what opens a ligated ion channel
neurotransmitter
39
why is it unique to have so many voltage gated ion channels at axon hillock
at certain threshold if met - they will ALL open at once to allow a sudden rush of Na IN and K+ out
40
what is the process of inhibitory pre-synaptic neuron
1. fires a whole bunch of AP
2. compound (temporal) summation of IPSP
3. extremely local, brief, and small
4. drives membrane potential further from membrane potential
41
what is the difference between repolarizing and depolarizing
depolarizing - membrane potential goes up
hyper-polarizing - membrane potential goes down (away from threshold)
42
temporal summation
repeated firing at one location to excite or inhibit
43
spatial summation
have thousands of neurons with synapses (sum total) with either excitatory or inhibitory response
44
ionotropic input
voluntary ( I am going to lift this, etc)
44
metabotropic input
automatic (from deep in spinal cord)
45
can cells have both ionoptropic and metabotropic input
yes
46
what signals are release from dorsal raphae (autonomic NS)
pre-synaptic cells serotonin
47
what signals are released from locus ceruleus (autonomic NS)
pre-synaptic cells norepinephrine
48
How do we describe the autonomic influence on somatic Voluntary - spinal cord excitation
Excitatory - diffuse (branches all over spinal cord), extensive ( tons of axons from LC and DR)
- function of system is to provide neuromodulator influence on motor neurons
49
what is metabotropic input
need biochemical signaling to open ion channels usually Calcium (sometimes sodium) with positive charges more on outside then inside causes Persistant inward current
- drive membrane potential up to put post-synaptic cell (motor neuron) on a hair trigger closer to threshold
- faster firing = more electrical stimulation of muscle
50
what are the three attributes all reflexes have
1. modifiable & adaptable to control movement in purposeful manner
2. graded in intensity (depending on stimulus strength)
3. location of reflex is locally specific and appropriate to the stimulus (ex. withdrawal only appropriate limb)
51
what are the modifications we can exert on a reflex circuit?
usually 3 places where this can occur
1. can increase excitation (puts it on hair trigger)
2. can inhibit reflex
52
what is tonic vs. dynamic modification of reflexes
Tonic: want a steady excitation which is useful for walking along uneven surfaces, ice, or grass (visually cant see) this causes a faster lengthening of the muscle detection so you can react quicker and not have an injury (roll your ankle)
Dynamic: causes your cell to oscillate in excitation for locomotion movement. want increased excitation during stance phase of soleus and not during swing phase
53
what are the types of movement
1. reflexes
2. rhythmic
3. voluntary
54
what is rhythmic movement?
involves circuits of neurons that produce automatic behavior upon receiving initial excitatory stimulus
(walking, running, swallowing etc.
55
where are CPGs?
brain stem & spinal cord
56
what are the mechanisms for control of voluntary movement?
feed-forward and feed-back control
57
what is feed-forward control
Before some event occurs- use sensory info to anticipate an incoming event
- use prior experience to predict outcome (knowledge of gravity, etc.)
- will stiffen joints which is the co-activation of agonist and antagonist ( preparing for resistance of item)
58
what is feed-back control
an event has occurred which changes some body position that you want to change to meet desired state
- use servo control (compares two signals and issues and output)
- compares desired state vs actual state (sensory info) continuously and then issue command to change position to get to desired state ( actuator)
59
what is the representation of muscles in motor cortex
area in motor cortex is dependent on fineness & precision of motor control required for that body part
60
what is actual vs. desired state
actual (sensory info about body in space) desired (setpoint)
61
what command is generated in the primary motor cortex
generate commands to go out of the brain to muscle
62
where does the most high level thinking of movements occur?
more frontal areas of brain "reach for coffee cup"
- have goal of movement
63
where is brain does motor planning occur (thinking of completing an action
prefrontal and premotor cortex
64
what are motor programs
memories of movement
65
where do we hold motor programs in the brain
in prefrontal cortex that is then mapped to primary motor cortex
66
stimulation of the primary and pre-motor cortex results in what
movement in the periphery
67
what are upper neurons
corticospinal neurons (start in motor cortex and through brain stem and synapse to alpha motor neuron in the ventral horn of spinal cord)
- lower neurons are alpha motor neurons
68
where do corticospinal neurons decussate
medulla
69
what was the conclusion from targeted reinnervation
- in amputee take damaged nerves and reroute to other muscle still intact
- can still generate signal from brain -> spinal cord -> out motor neuron
- makes movements more refined because own thoughts are controlling prosthetic
70
what is the organization for indirect pathway (more old brain)
indirect (neuron from motor cortex synapses in brain stem before going to spinal cord)
more medial in spinal cord
controls more proximal muscles which are responsible for more gross movements
71
what is the organization for direct pathway
direct
- more lateral
-distal motor control (hands, fingers)
- fine motor controlw
72
what is the function of the purkinje cells
process massive information coming into cerebellum
73
how does the cerebellum complete comparison of actual vs. desired state
actual state is based on afferent sensory info of body position which is compared to the copy of the motor command sent to body.
74
How do muscle spindles maintain sensitivity along all muscle length changes
Gamma motor neuron innervation directly changes sensitivity
75
Why do we want the muscle spindle to be so sensitive ?
The constant tonic firing produces very low muscle force = muscle tone
- helps to keep body upright and rigid
76
How does muscle force relate to golgi tendon organ firing
Golgi tendon organs are in the tendon of the muscle and have aferente axons weaved through the collagen fibers - with increased muscle force -> squish aferente axons -> fire more A.P to brain
77
How does muscle force relate to golgi tendon organ firing
Golgi tendon organs are in the tendon of the muscle and have aferente axons weaved through the collagen fibers - with increased muscle force -> squish aferente axons -> fire more A.P to brain
78
How does muscle force relate to golgi tendon organ firing
Golgi tendon organs are in the tendon of the muscle and have aferente axons weaved through the collagen fibers - with increased muscle force -> squish aferente axons -> fire more A.P to brain
79
What is ensamble activity
Collection of firing from neurons
80
how does the cerebellum get the intended movement?
motor command from motor cortex -> pons which patches over command to cerebellar cortex
81
how is the actual movement of your body sent to your cerebellum
afferent neurons innervate into the cerebellar cortex which is the sensory info of what is actually the position of body
82
once cerebellum has actual and desired movement - what does it do?
the output of the cerebellum is the correction (how to get desired and actual state to meet) -> thalamus -> motor cortex
THIS is a continual flow of information
83
what is the function of the basal ganglia
puts "blanket" on motor commands
- helps initiate movement
- planning and execution of higher order, complex motor tasks
84
what is the loop of how basal ganglia gets its information
process motor command and smooth out this command
motor command from motor cortex -> basal ganglia -> thalamus then back to motor cortex
85
what is convergence
very large number of cells involved in process which converges onto small amount of neurons
ex. moving finger
86
what actually is a motor command ?
group of thousands of cells engaging in common behavior
ensemble activity starting low and increasing or decreasing firing
87
what is ensemble activity of neurons
a bunch of neurons firing together that have similar function
88
what is motor learning
using memories and experience to modify movement
89
where in the brain does motor learning occur
cerebellum
90
what is the circuit of communication between the GTO and brain - what is the function of the GTO
protection
afferent neuron between the collagen fibers gets squished with muscle force -> AP travels along axon -> innervates dorsal horn -> one pathway goes up into brain to tell the current muscle force -> ANOTHER path goes to an inhibitory INterneuron which synapses on an alpha motor neuron -> synapses on muscle and inhibits muscle force
91
what is the major attributes of sensations
1. modality (what is it sensing)
2. intensity ( dependent on stimulus strength)
3. duration (has beginning, middle, and end)
4. location (sensory signals go to sensory cortex in perfect mapped out way)
92
what type of receptor/sensor has mechano-sensitive ion channels ?
1. muscle spindle
2. GTO
3. Pacinian Corpuscles
4. merkel disk receptors
(pressure receptors)
93
what is the function of Meissner's corpuscles
fight light touch, rapidly adapting, numerous in amount
94
what is the function of Merkel Disc cells
pressure, slowly adapting, and numerous
95
what is the function of Pacinian Corpuscles
Vibration, pressure, rapidly adapting, less numerous
96
what is the function of Ruffini endings
skin stretch, slowly adapting, less numerous (more intense stimulus so don't need many receptors)
97
what are the slowly adapting receptors
Ruffini endings and Merkle discs
98
what are the rapidly adapting receptors
Pacinian corpuscles and Meissner's corpuscle
99
what is the signal for intensity of a sensory stimulus?
A.p are the code the CNS receives
- frequency is dependent on stimulus strength
- AP frequency correlates with perceived sensation
100
where is the neural coding of stimulus intensity faithfully sent?
sensory cortex
101
location of sensory receptors?
depends on what the function of the receptor is (deep vs. superficial in skin)
102
duration of stimulus - what receptors are responsible
- slowly adapting receptors inform CNS about continual stimulus
- rapidly adapting receptors inform CNS about changing in stimulus intensity (on/off)
103
what receptors are firing when muscle is stretched
1. muscle spindle afferent excited most, while GTO less excited
104
what receptors are firing when muscle is shortened (unload response in muscle spindles)
1. muscle spindle afferent decrease in firing, while GTO increase afferent firing
105
where are the visual receptors located and where do they go ?
start in retina -> axons project to thalamus -> routed to appropriate part of cortex
106
what cells are responsible for interpreting form (edges of image)
slowly adapting sensor
107
what cells are responsible for interpreting moving objects (moving edges of image)
rapidly adapting sensor
108
what is the vestibular apparatus and how is it helpful
3 canals with triaxial rotation sensors so you know your head position in space. The canals have little hair cells that project off into fluid in the canal (honey consistency)
109
what happens when the little hairs in the ear are deflected
causes depolarization -> generate A.P in afferent neuron -> sends this to brain and interprets the position of the head
If you move your head the opposite way you will decrease firing and hyper polarize the cell so thats how your brain knows position of head because one way causes A.P and the other does not
110
what type of information does vestibular afferent provide info to CNS
- linear (front to back neck movement/ side to side)
- angular acceleration
111
what is the vestibulo-spinal reflex
direct connection between vestibular apparatus in motor neurons through brain stem (that activate muscles that keep your head upright)
- if head were to rotate forward -> your body will follow -> causes contracting of spinal muscles
- if back head rotation -> activates muscles in front (abs) to bring head back up
This is a subtle movements and dont want to have to think about controlling this (want automatic)
112
113
How does the vestíbulo-ocular reflex work
Eyes can look straight ahead while head rotates
- vestibular apparatus is the sensor
- when head rotates it deflects the hair cells in one of the canals
- 7 extrinsic muscles control eye
- 3 neurons involved
- bilateral so both eyes to stabilize while head moves
114
How does the vestíbulo-ocular reflex work
Eyes can look straight ahead while head rotates
- vestibular apparatus is the sensor
- when head rotates it deflects the hair cells in one of the canals
- 7 extrinsic muscles control eye
- 3 neurons involved
- bilateral so both eyes to stabilize while head moves
