Nerve and Muscle Flashcards
1
Q
What does the central nervous system consist of
A
The brain and spinal cord
2
Q
What does the peripheral nervous system consist of
A
Peripheral nerves and ganglia
3
Q
What are the two types of cells in the nervous system
A
Neurons and glia
4
Q
Neuron definition
A
Cells specialised for transmission of information
5
Q
How many types of neurons are there
A
4
6
Q
What is the function of glia
A
Support for neurons
7
Q
How many types of glia are there
A
5 (4 in CNS, 1 in PNS)
8
Q
Dendrites function
A
Receive input, send info to cell body
9
Q
Cell body of neuron function
A
Contains nucleus and organelles, sums input
10
Q
Axon function
A
Carries electrical impulses
11
Q
Axon terminals function
A
End of axon, releases neurotransmitter
12
Q
Groups of cell bodies in the CNS
A
Nuclei
13
Q
Bundle of axons in the CNS
A
Tract
14
Q
Group of cell bodies in the cerebral cortex or spinal cord
A
Grey matter
15
Q
Bundle of axons in cerebral cortex or spinal cord
A
White matter
16
Q
Group of cell bodies in the PNS
A
Ganglion
17
Q
Bundle of axons in the PNS
A
Nerve
18
Q
Input zone of neuron
A
Dendrites, cell body, receives chemical signals
19
Q
Summation zone of neuron
A
Axon hillock, sums inputs
20
Q
Conduction zone of neuron
A
Axon, carries electrical signals
21
Q
Output zone of neuron
A
Axon terminals, contact with input zone of other neurons or effectors, release of neurotransmitter
22
Q
4 types of neurons
A
Multipolar, bipolar, unipolar, anaxonic
23
Q
CNS glia types
A
Astrocytes, microglia, ependymal cells, oligodendrocytes
24
Q
Astrocytes function
A
Supply nutrients to neurons, ensheath blood capillaries, injury response
25
Microglia function
Immune cells of CNS, engulf microorganisms and debris
26
Ependymal cells function
Line fluid filled spaces of brain and spinal cord, have cilia to circulate CSF
27
Oligodendrocytes function
Support nerve fibres, ensheath with myelin
28
PNS glia name and function
Schwann cells: support peripheral nerve fibres, ensheath with myelin
29
What is a myelin sheath
Lipid (fat) wrapped around an axon (membrane wrapped around many times)
30
Gaps between schwann cells
Nodes of ranvier
31
Purpose of myelin sheath
Increase conduction velocity
32
Afferent
Information going into the brain
33
Efferent
Information leaving the brain
34
Effectors
Cells in the body that respond in some may to neural input (e.g muscle fibre)
35
Receptors
Where information about stimuli comes into the body
36
Somatic
Stuff we are aware of, voluntary (efferent), sensory information (afferent)
37
Autonomic
Stuff we are not aware of, have no control over, involuntary muscle control (efferent), sensory information we don't know about (afferent)
38
Somatic efferent neural organisation
Upper motor neuron (cell body in brain, axon in spinal cord), lower motor neuron (cell body in spinal cord, axon in spinal nerve) Both myelinated, both synapses use Ach
39
Two divisions of autonomic efferent nervous system
Sympathetic, parasympathetic
40
Autonomic efferent effectors
Smooth muscle, cardiac muscle, glands, adipose tissue
41
Autonomic efferent neural organisation
Neuron #1 (cell body in brain, axon in brain or spinal cord), neuron #2 (cell body in brain or spinal cord, axon in PNS) (myelinated, Ach), neuron #3 (cell body in PNS, axon in PNS) (unmyelinated, Ach or NE)
42
Autonomic ganglion
Collection of neuron #3 cell bodies in autonomic system
43
Sympathetic
Fight or flight
44
Parasympathetic
Rest and digest
45
Structural differences between sympathetic and parasympathetic nervous systems
Sympathetic: neuron 2 short (Ach), neuron 3 long (NE)
Parasympathetic: neuron 2 long (Ach), neuron 3 short (Ach)
46
Sympathetic ganglion location
Close to CNS
47
Para sympathetic ganglion location
Far from CNS
48
Sympathetic neuron #2 cell body location
Thoracolumbar region of spinal cord
49
Sympathetic chain ganglia location
Either side of vertebral column, 21-23 pairs
50
Parasympathetic neuron #2 cell body location
Cranial or sacral region
51
Synapse definition
Connection and communication point between a presynpatic and postsynaptic cell
52
Synaptic transmission
The process by which a presynpatic neuron releases a neurotransmitter which diffuses across cleft. Neurotransmitter binds to receptors/ion channels on post synaptic neuron
53
How does a chemical signal get converted into an electrical signal?
Chemically gated ion channels opened by neurotransmitter, local depolarisation to threshold (-60mV)
54
Chemically gated stimulus
Chemical (neurotransmitter)
55
Voltage gated stimulus
Voltage (depolarisation to -60mV)
56
Mechanically gated stimulus
Membrane deformation
57
Where are chemically gated channels on a neuron
Dendrites and cell body
58
Where are voltage gated channels on a neuron
Axon hillock, axon, axon terminals
59
What causes a voltage gated ion channel to open?
Membrane depolarisation to -60mV
60
Why is the RMP -70mV
Lots of negatively charged proteins, Na+/K+ exchange pumps, 3Na+ out for every 2K+ in
61
What is a local potential
A change in membrane potential voltage at a localised area of the dendrite or cell body membrane (also called graded potentials as they can vary in magnitude)
62
What is an excitatory local potential (EPSP)?
Depolarisation of the cell membrane due to a presynaptic neuron releasing an excitatory neurotransmitter (Ach or NE) which opens chemically gated Na+ channels
63
What is an inhibitory local potential (IPSP)?
Hyperpolarisation of the cell membrane due to a presynaptic neuron releasing an inhibitory neurotransmitter (GABA) which opens chemically gated K+ channels
64
What is spatial summation
Summed input from multiple presynaptic neurons
65
What is temporal summation
Summed input from repeated firing of one presynaptic neuron
66
Why are presynaptic neurons summed at the axon hillock
High density of voltage gated channels
67
Why does rapid depolarisation occur in an action potential
Voltage gated Na+ channels open when membrane depolarises to -60mV
68
At what voltage do voltage gated Na+ channels inactivate and K+ channels (finally) open in an action potential
+30mV
69
Why does repolarisation occur in an action potential
K+ channels open and Na+ channels close
70
Why does hyperpolarisation occur in an action potential
K+ channels close slowly resulting in excess K+ leaving the cell
71
At what voltage do voltage gated K+ channels finally close
About -90mV
72
Conduction zone of the neuron
Axon
73
Output zone of the neuron
Axon terminals (release neurotransmitter)
74
How does an electrical signal trigger a chemical signal
Na + diffuses from axon hillock to initiate AP in initial segment of axon, propagates to each neighbouring segment (unmyelinated) or node (myelinated) in one direction. AP arrives at axon terminals causing VG calcium channels to open. Calcium enters terminals causing release of neurotransmitter into synaptic cleft
75
Absolute refractory period
Rapid depolarisation and repolarisation of cell membrane
76
Relative refractory period
Hyperpolarisation of cell membrane
77
How long is each myelination
Perfectly spaced for amount of sodium needed to cause next node voltage gates to open
78
When can a second AP be generated during propagation
During relative refractory period, only if stimulus is much larger than normal (lots more sodium)
79
What state must voltage gated Na+ channels be in in order to open
Closed
80
What channels are on the post synaptic cell membrane
Chemically gated ion channels
81
What enzymes are present in the synaptic cleft
Enzymes that inactivate neurotransmitter
82
Ca2+ is always...
Excitatory: something is going to move
83
What does Ca2+ trigger in presynaptic axon terminal
Movement of synaptic vesicles, causing them to release neurotransmitter
84
Excitatory neurotransmitters
Ach, NE (noradrenaline)
85
Inhibitory neurotransmitter
GABA
86
Synaptic transmission ends when
Neurotransmitter unbinds from chemically gated channels, enzymes in synaptic cleft degrade neurotransmitter and recycled back into axon terminal
87
Cholinergic synapse
Ach is the neurotransmitter
88
Summation at neuromuscular junction
Not usually needed, one synaptic transmission generally results in muscle membrane brought to threshold
89
Electrical synapse downfall
No opportunity for signal modulation as gap junctions connect pre and post synaptic neurons
90
Where does the spinal cord end
Inferior border of 1st lumbar vertebra (L1)
91
Where does the spinal cord go in vertebrae
Through the spinal canal
92
Which side of the vertebrae have spinous processes
Dorsal
93
How far does the spinal cavity extend
All the way to coccygeal vertebrae
94
What is the spinal cord contained within
Meningeal sac filled with CSF
95
What is the end of the spinal cord tapered into
Conus medularis (non neural tissue)
96
What anchors the spinal cord in place
Filum terminale (fibrous, non-neural tissue)
97
How many segments does the spinal cord have
31
98
How many pairs of spinal nerves does each region of the spinal cord have
Cervical: 8, thoracic: 12, lumbar: 5, sacral: 5, coccygeal (1)
99
Where do spinal nerves exit (with one exception)
Below the vertebrae they're named after. EXCEPT for first cervical spinal nerve which exits between the skull and first cervical vertebra
100
Name for large collection of nerves inferior to end of spinal cord
Cauda equina
101
Posterior feature of spinal cord
Median sulcus
102
Anterior feature of spinal cord
Median fissure
103
What is in the centre of the spinal cord
Central canal
104
What is the dorsal horn made up of
Cell bodies
105
What is the dorsal column made up of
Sensory nerve axons
106
What is the ventral horn made up of
Motor nerve cell bodies (specifically somatic motor neurons)
107
What is the ventral column made up of
Motor nerve axons
108
What is the lateral horn made up of
Cell bodies
109
What is the lateral column made up of
Axons
110
What is the dorsal nerve root made up of
Sensory nerve axons
111
What is the dorsal root ganglion made of
Sensory nerve cell bodies
112
What is the ventral nerve root made up of
Motor nerve axons
113
What are spinal nerves made up of
Combination of dorsal and ventral nerve roots (sensory and motor, efferent and afferent)
114
What would happen if there was damage to the ventral horn?
Paralysis of muscles supplied by somatic motor neurons from this segment, same side only
115
What type of neurons are in the dorsal root ganglion
Unipolar (sensory neurons)
116
What would happen if there was damage to the dorsal horn?
Loss of sensation from regions of the body supplied by sensory neurons from this spinal cord segment, same side only
117
What does the spinal nerve branch into
Dorsal and ventral rami (to corresponding regions of the body), and rami communicans and sympathetic ganglion
118
Where are rami communicans
Only at T1-L2
119
What connective tissue are axons covered in
Endoneurium
120
What connective tissue are fascicles covered in
Perineurium
121
What connective tissue are nerves covered in
Epineurium
122
Bundles of axons in the CNS are called a
Tract
123
What are the three layers of the meninges
Dura mater, arachnoid and pia mater
124
What are the features of the dura mater
Outermost layer, dense and fibrous, two layers (inner and outer), space between forms venous sinuses, inner layer forms dural folds
125
Name the three dural folds
Falx cerebri, falx cerebelli, tentorium cerebelli
126
Purpose of the dural folds
Separate major divisions of the brain, provide stability within cranium
127
Falx cerebri
Dural fold that separates hemispheres of the cerebrum (median plane)
128
Falx cerebelli
Dural fold that separates hemispheres of the cerebellum (median plane)
129
Tentorium cerebelli
Dural fold that separates the cerebrum from the cerebellum (horizontal plane)
130
Purpose of venous sinuses
Collect venous (deoxygenated) blood from the brain (guide into jugular vein and out) and old CSF after it has cycled through the ventricular system
131
Arachnoid features
Layer beneath dura mater, named for its spider like appearance, does not extend into sulci, contains subarachnoid space and arachnoid granulations, contains blood vessels which lie in the subarachnoid space
132
What are venous sinuses
Gap between inner and outer layers of dura mater
133
Subarachnoid space
Between arachnoid and pia mater, filled with cerebrospinal fluid, contain blood vessels
134
Arachnoid granulations
One way valves which perforate inner layer of dura mater and transport old CSF from subarachnoid space into venous sinus
135
Pia mater features
Innermost layer of meninges, transparent and delicate, blood vessels sit on top, adheres to brain, follows gyri and extends into sulci
136
What does the dura mater ensheath
Brain, spinal cord and spinal nerves
137
Purpose of CSF
Nourishment (transports nutrients and waste) and protection (support and cushion)
138
What does the choroid plexus do
Produces CSF
139
Where is the choroid plexus
Within the ventricles (underneath lateral ventricles)
140
What are the spaces of ventricles lined with
Ependymal cells
141
What is the purpose of ependymal cells
Circulate CSF by waving cilia
142
What ventricles make up the ventricular system
2 lateral ventricles, 1 third ventricle, cerebral aqueduct and fourth ventricle, and central canal of the spinal cord
143
Where are the lateral ventricles located
One in each cerebral hemisphere
144
Where is the third ventricle located
The diencephalon
145
Where is the cerebral aqueduct located
Midbrain
146
What does the cerebral aqueduct do
Connects 3rd to 4th ventricle
147
Where is the fourth ventricle located
The level of the cerebellum
148
How is old CSF removed
Recycled out in blood
149
What is the order of circulation of CSF
Lateral ventricle -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> subarachnoid space (around brain and spinal cord) -> exits through arachnoid granulations into venous sinus
150
Name the lobes of the brain
Frontal, parietal, occipital, temporal
151
Sulcus
Valley
152
Gyrus
Hill
153
What does the central sulcus separate
Frontal and parietal lobe
154
What separates the parietal and occipital lobes
Parieto-occipital sulcus
155
What separates the temporal lobe from the frontal and parietal lobes
Lateral sulcus
156
What separates the cerebrum from the cerebellum
Transverse fissure
157
What functions are the frontal lobe associated with
Motor control, language, personality
158
What functions are the parietal lobe associated with
Somatosensory
159
What functions are the temporal lobe associated with
Memory and hearing
160
What functions are the occipital lobe associated with
Vision
161
What is the cerebral cortex
Outer layer of the cerebrum (grey matter)
162
What is the diencephalon composed of
Thalamus and hypothalamus
163
What is the corpus callosum made of
White matter
164
What is the function of the corpus callosum
Connects the sides of the brain by commisural tracts
165
What is the brainstem composed of
Midbrain, pons and medulla oblongata
166
What are the central, deep structures of the brain called
Deep nuclei
167
3 types of white matter
Commissural tracts, projection tracts, association tracts
168
Function of commissural tracts
Cross from side to side of brain, both directions, connect
169
Function of projection tracts and example
Axons between cortex and CNS areas outside cerebrum, e.g corticospinal tract
170
Function of association tracts
Axons on same side within cerebral cortex, communication between brain areas, short or long distance
171
Primary motor cortex (major cortical area for motor control)
Pre central gyrus
172
Primary somatosensory cortex (major cortical area for somatosensory perception)
Post central gyrus
173
What neurons are in the somatic efferent (motor) division
Upper and lower motor neuron, both myelinated
174
What is the effector of the somatic efferent (motor) division
Skeletal muscle
175
What is the neurotransmitter of the somatic efferent (motor) division
Acetylcholine
176
Example pathway of the somatic efferent (motor) division
Corticospinal pathway
177
Where is the upper motor neuron
Part of the somatic efferent (motor) division, cell body in primary motor cortex, extends to spinal cord on opposite side (crosses through medulla oblongata), makes synapse on lower motor neuron
178
Where is the lower motor neuron
Part of the somatic efferent (motor) division, cell body in ventral horn of spinal cord, axon extends out of spinal cord (ventral root) into body, makes synapse on skeletal muscle
179
What happens if the primary motor cortex is damaged
Muscle weakness and paralysis in region of body corresponding to location of damage, opposite side
180
How many neurons are involved in the corticospinal pathway
2 (upper and lower motor neurons)
181
How many neurons are involved in the dorsal column pathway
3, neurons 1, 2 and 3 (not including neuron cell body in somatosensory cortex)
182
Where is neuron 1 of the dorsal column pathway (somatic afferent)
Dorsal root ganglion (unipolar), peripheral fibre extends to sensory recpetor, central fibre ascends in dorsal columns
183
Where is neuron 2 of the dorsal column pathway (somatic afferent)
Medulla oblongata, axon crosses to other side and extends
184
Where is neuron 3 of the dorsal column pathway (somatic afferent)
Thalamus, ascends to somatosensory cortex, synapses on cell body of somatosensory cortex neuron
185
What happens if there is damage to the primary somatosensory cortex?
No perception of touch in the corresponding region of cortex, on the opposite side
186
Where is the thalamus relative to the hypothalamus
Superior
187
What are somatic senses
Detected by receptors in the skin, muscle and joints
188
What are visceral senses
Detected by receptors in the internal organs
189
What is sensory transduction
Conversion of a sensory stimulus into an action potential
190
4 ways the brain interprets action potentials from sensory neurons
Modality, duration, intensity, location
191
4 types of sensory receptors
Thermoreceptor, chemoreceptor, mechanoreceptor, nociceptor
192
3 types of mechanoreceptors
Baroreceptor, proprioceptor, tactile receptors
193
What do tactile receptors detect
Skin touch (light touch, pressure, texture, vibration, stretch) Some tonic some phasic
194
What do proprioceptors detect
Proprioception (limb position related to torso), stretch or tension in skin, muscle and/or skin (tonic)
195
What do baroreceptors detect
Pressure (stretch of visceral tubes e.g blood vessels, airways, intestines)
196
Features of thermoreceptors
Nerve ending with temperature gated ion channels, respond to different temperatures and changes in temperature (phasic)
197
Features of chemoreceptors
Specialised receptor cells with chemically gated ion channels, respond to different chemical concentrations
198
Mechanoreceptor features
Nerve endings with mechanically gated ion channels
199
Mechanoreceptor example
Muscle spindle (proprioceptor)
200
Phasic meaning
Fast adapting
201
Tonic meaning
Slow adapting
202
Nociceptor features
Nerve endings that respond to noxious stimuli (excess temperature, chemical, mechanical stimuli) (Tonic)
203
Phasic receptors
Normally silent, send APs with change but stop quickly
204
Tonic receptors
Continually active to reflect background level of stimulation, AP frequency changes when stimulus intensity changes
205
What is intensity of stimulus communicated by
AP frequency plus number of neurons activated
206
What is a receptive field
The area of skin with receptive endings of a single sensory neuron
207
Small and densely packed receptive fields provide
More sensitivity (better two point discrimination), more accurate localisation
208
The pre and post central gyrus are mapped ______
Somatotopically
209
Areas with large receptive fields have ____ representation in the brain because ________
Less, fewer neurons involved
210
Which parts of the brain are involved in planning movement
Prefrontal cortex, premotor cortex
211
What does the prefrontal cortex do in voluntary movement
Plans movements
212
What does the premotor cortex do in voluntary movement
Sequences movements
213
Which part of the brain is involved in initiating movement
Primary motor cortex
214
What does the motor cortex do in voluntary movement
Produces specific movements
215
Which parts of the brain are involved in modifying movement
Basal nuclei and cerebellum
216
What is the function of the basal nuclei
Influences posture and automatic movements, regulates muscle tone, refines movements (selects which to allow and which to inhibit)
217
How do the basal nuclei undertake their function of modifying movement
By altering sensitivity of neurons projecting into the corticospinal or other pathways
218
What is the function of the cerebellum with relation to voluntary movement
Stores and facilitates learning, planning and execution of motor programs. Monitors and compares sensory input to compare actual movement to planned movement. Organises timing of muscle contractions and modifies ongoing activity
219
Where does the prefrontal cortex send signals to regarding voluntary movement
Premotor cortex
220
Where does the premotor cortex send signals to regarding voluntary movement
Primary motor cortex, basal nuclei and cerebellum
221
Where does the primary motor cortex send signals to regarding voluntary movement
Down corticospinal pathway
222
Where do the basal nuclei and cerebellum send signals to regarding voluntary movement
Back and forth to each other, to frontal cortex and down descending pathways
223
What is the corticospinal pathway
Pathway from primary motor cortex to effector muscle initiating voluntary movement
224
What does the corticospinal pathway consist of
An upper and lower motor neuron
225
What is a motor unit
A single lower motor neuron and all the skeletal muscle fibres it innervates
226
What is a small motor unit
Single lower motor neuron and few muscle fibres it innervates (more precise)
227
What is a large motor unit
Single lower motor neuron and many muscle fibres it innervates (more forceful)
228
What characterises a voluntary movement
Wide variety of speed, duration and complexity, complex patterns of sensory and motor processing, variable latency (~100+ms), can be trained
229
What characterises a reflex movement
Reproducible, automatic motor response to external stimulus, simple neural circuit within peripheral nerves and spinal cord, consistent latency (~40ms), can't be trained
230
Latency of variable movement
~100+ ms
231
What is a stretch reflex
Recognition of sudden unwanted stretch and reflex to protect from tearing
232
What is the structure of a muscle spindle
Dendritic endings (mechanically gated Na+ channels) of a sensory neuron wrap around specialised intrafusal muscle fibres
233
What neurons are involved in the stretch reflex
Sensory neuron, motor neuron (synapse in spinal cord), interneuron in spinal cord which inhibits activation of motor neuron that innervates opposing muscles
234
What is an interneuron
Neuron between motor and sensory in a reflex (can be excitatory or inhibitory). Any connector neuron that is neither sensory nor motor
235
What is a withdrawal reflex
Reflex response to painful stimuli
236
What neurons are involved in the withdrawal reflex
Sensory neuron, motor neuron (synapse in spinal cord), interneuron (excitation of motor neurons stimulating flexors, inhibition of motor neurons stimulating extensors)
237
Somatic efferent and afferent synapses at medulla
Controlateral (swap sides)
238
Generic function of thalamus
Gateway of sensation into the brain
239
Where are autonomic neuron cell bodies located
Lateral horn
