Module 3: Nerve and Muscle Flashcards
(233 cards)
1
Q
Two parts of nervous system
A
Central nervous system
Peripheral nervous system
2
Q
What makes up the CNS? (2)
A
Brain and spinal cord
3
Q
What makes up the PNS? (2)
A
Peripheral nerves
Ganglia
4
Q
Which cells make up the CNS and PNS? (2)
A
Neurons and glia
5
Q
What are neurons specialised for?
A
Transmission of information
6
Q
Main function of glial cells
A
Provide support for neurons
7
Q
Dendrite functions (2)
A
Receive input
Send information to cell body
8
Q
Where are the organelles in an axon?
A
In the cell body
9
Q
Cell body function
A
Sums inputs
10
Q
Axon function
A
Carries action potentials
11
Q
Axon hillock location and function
A
Where head meets axon
Initiates action potential
12
Q
Axon terminal function
A
Release neurotransmitters
13
Q
Nucleus (CNS)
A
Group of cell bodies in the CNS
14
Q
Tract (CNS)
A
Bundle of axons in the CNS
15
Q
Grey matter
A
Group of cell bodies in spinal cord or cerebral cortex
16
Q
White matter
A
Bundle of axons in spinal cord or cerebral fluid
17
Q
Ganglion
A
Group of cell bodies in the PNS
18
Q
Nerve
A
Bundle of axons in the PNS
19
Q
What are the four neuron components/ zones?
A
Input zone
Summation zone
Conduction zone
Output zone
20
Q
Input zone
A
Dendrites and cell body
Receives chemical signals from other neurons
21
Q
Summation zone
A
Axon hillock
Summation of inputs
22
Q
Conduction zone
A
Axon
Carries action potentials
23
Q
Where does the axon carry action potentials between? (4)
A
Between brain areas
To and form spinal cord
From peripheral sensory receptors
To effector cells
24
Q
Output zones
A
Axon terminals
In contact with input zone of effectors or other neurons. Releases neurotransmitters
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What is a neurotransmitter a type of?
Chemical signal
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Name the four neuron types
Multipolar
Bipolar
Unipolar
Anaxonic
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Multipolar neuron
Neuron with multiple processes emanating from cell body
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Bipolar neuron
Neuron with two processes emanating from cell body
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Unipolar neuron
Neuron with one process emanating from cell body.
This process branches into a dendrite and an axon
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Anaxonic neuron
A neuron with no distinct axon. All processes look alike
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Five types of glial cells
Astrocytes
Microglia
Ependymal cells
Oligodendrocytes
Schwann cells (PNS)
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Astrocyte functions (3)
Supply nutrients to neurons
Ensheath blood capillaries
Respond to injury
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Microglia function
Engulf microorganisms and debris
| Immune cells of the CNS
34
Ependymal cell function
| What special component do they contain?
Line fluid-filled spaces of the brain and spinal cord
Cilia
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Oligodendrocyte function
Support axons by ensheathing them with myelin sheath
36
Schwann cell function
Support peripheral nerve fibres by ensheathing them with myelin
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How do Schwann cells ensheath the axon? What tissue is used?
Wrap their plasma membrane around the axon.
Fat (phospholipid)
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Which two glial cells are similar in function?
Oligodendrocytes and Schwann cells
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What are the gaps between myelin called? What effect do these have?
Nodes of Ranvier
Help to increase conduction
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Synapse
A junction where communication between neurons occurs
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Where does the axon potential travel to/from?
From axon hillock to axon terminal
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What happens after action potential reached axon terminal?
Synaptic vesicles containing neurotransmitter fuse with the membrane and release it into the synaptic cleft
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At what point is the neurotransmitter transmitted to the post-synaptic neuron?
At the input zone receptors
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How does the signal change during communication between neurons?
Electrical to chemical to electrical
Action potential to neurotransmitter to action potential
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Synaptic cleft
Small space between axon terminal of pre-synaptic cell and dendrites of post-synaptic cell
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Synaptic vesicle
Vesicle containing neurotransmitter which waits for a signal to release it
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What is the cell releasing neurotransmitter called?
Pre-synaptic neuron
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What is the cell receiving neurotransmitter called?
Post-synaptic neuron
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Afferent information
Information coming into the brain
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Efferent information
Response that comes out of the brain
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How do we remember the difference between afferent and efferent?
Afferent is information ascending up to the brain
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Somatic information
Information we are aware or/ have control over
E.g. voluntary muscle control
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Autonomic information
Information we have no awareness of/ body oversees automatically
E.g. blood pressure
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Effectors of somatic efferent division
Skeletal muscle fibres
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Somatic efferent diversion neurons
Upper motor neuron
| Lower motor neuron
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Position of upper motor neuron
Cell body in brain
| Axon in spinal cord
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Position of lower motor neuron
Cell body in spinal cord
| Axon in spinal nerve
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Similarity between upper and lower motor neurons
Both are myelinated
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Where is the first synapse located in somatic efferent division?
In spinal cord
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Where is the second synapse located in somatic efferent division?
Between lower motor neuron and skeletal muscle fibres
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Which neurotransmitter do somatic efferent division synapses release?
ACh acetylcholine
62
Two divisions of the autonomic efferent nervous system
Sympathetic and parasympathetic
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Effectors of autonomic efferent nervous system (4)
Smooth muscle
Cardiac muscle
Glands
Adipose tissue
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How many neurons are used in autonomic efferent pathway?
Three
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Positions of neurons in autonomic efferent pathway
1. Cell body in brain, axon in brain or spinal cord
2. Cell body in brain or spinal cord, axon in PNS
3. Cell body and axon in PNS
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Are autonomic efferent pathway neurons 2 and 3 myelinated?
2 is, 3 isn’t
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Where is the synapse between neurons 2 and 3 in the autonomic efferent pathway?
In an autonomic ganglion
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Where is the synapse between neuron 3 and effector in the autonomic efferent pathway?
On effector
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How can we refer to neurons about an autonomic ganglion? (2)
Pre-ganglionic neuron
| Post-ganglionic neuron
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Which neurotransmitter does the first synapse in autonomic efferent pathways release?
Acetylcholine ACh
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Which neurotransmitter does the second synapse in autonomic efferent pathways release?
Acetylcholine ACh in parasympathetic division
Norepinephrine NE/ nonadrenaline
72
Which system does the term ‘fight or flight’ refer to?
Sympathetic division
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Which division does the term ‘test and digest’ refer to?
Parasympathetic
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Which factors increase and decrease in the sympathetic division?
Increase: heart rate, pupil size, sweating
Decrease: gastric motility, salivation
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Which factors increase and decrease in the parasympathetic division?
Decrease: heart rate, pupil size, sweating
Increase: gastric motility, salivation
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In which levels of the spinal cord do cell bodies of sympathetic neurons (second) lie?
Thoracolumbar levels
| T1-L2
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In which spinal cord levels do the cell bodies of parasympathetic neurons (second) lie?
Cranial and sacral levels
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Where so sympathetic ganglia lie?
On either side of vertebral column
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Where do parasympathetic ganglia lie?
Synapse in or near effector
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Which division has a short second axon?
Sympathetic
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Which division has a long second axon?
Parasympathetic
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Membrane potential
Distribution of ions inside and outside the cell which creates a difference in charge across the membrane
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Resting membrane potential
-70mV
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Mechanisms maintaining resting potential (2)
Leak channels (potassium and sodium)
Voltage gated channels (potassium and sodium)
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What lies at the initial segment of the axon?
High concentration of sodium channels
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Where is it decided if AP propagation will go ahead or not?
Axon initial segment
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Gates of ion channels (2) and when they open and close
Activation gate: opens when action potential arrives (closer before)
Inactivation gate: closes after depolarisation (open before)
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Step one of action potential (at threshold)
A local change in membrane potential occurs sufficient to depolarise the cell
Na+ channels open
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Step two of AP
Na+ channels are open and slow Na+ into the cell
Depolarisation occurs
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Step three of AP
Na+ channels close
K+ channels open
Repolarisation occurs
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Step 4 of AP
K+ channels close
Membrane hyperpolarises because K+ channels are slower to close.
Potential returns to resting and both channels close
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Absolute refractory period
Interval of time in which a second action potential absolutely cannot be initiated
Occurs during depolarisation and repolarisation (steps 2 and 3)
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Relative refractory period
Interval of time in which a second AP can be generated, but it requires a much larger stimulus than the first AP.
Occurs during hyperpolarisation (step 4)
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Propagation of action potentials
A regeneration of action potentials along the axon
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How do AP propagation and conduction of electricity differ?
APs are regenerated, not conducted. New versions of the same signal are produced- the same one isn’t carried the whole way down the axon
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Describe AP propagation
Generated at initial segment and sodium channels open there.
Action potential develops in segment 2. Initial segment begins repolarisation by opening potassium channels.
A headed depolarisation brings segment 3 membrane to threshold.
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Why can APs only move forward?
Because the initial segment membrane goes into the absolute refractory period of repolarisation
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How does propagation of AP in unmyelinated axons differ from that in myelinated axons?
AP jumps from node to node in myelinated axons. The internodes (Schwann cells) act as excellent conductors.
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A stimulus at resting potential produces ____?
A graded potential
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A graded potential may generate ____?
An action potential
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An action potential triggers _____?
Synaptic activity
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Synaptic activity leads to _____?
Information processing
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Where does ACh bind to on the post-synaptic neuron?
Protein channels in membrane
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Event one of transmission at synapse
Action potential triggers opening of voltage-gated channels
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What occurs after action potential triggers opening of channels?
Calcium ions diffuse into the axon terminal and trigger synaptic vesicles to release ACh
106
What occurs after synaptic vesicles release ACh?
ACh diffuses across the synaptic cleft and bonds to voltage-gated channels
Producing a graded depolarisation (or EPSP)
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EPSP
Excitatory post synaptic potential
108
What ends depolarisation/ EPSP?
AChE breaking down ACh into acetate and choline
109
What happens to the choline that is produced from breaking down ACh?
The axon terminal reabsorbs it from the synaptic cleft and uses it to synthesise new ACh
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IPSP
Inhibitory post synaptic potential
111
Is there summation at an NMJ?
No- NMJ synaptic transmission is excitatory and absolute
112
Temporal summation
Summation over time
Secondary action potentials build on initial one
113
Spatial summation
Summation in space
Two simultaneous stimuli from two different neurons summate to give large action potential
114
Where does the spinal cord start?
Foremen magnum (opening at base of skull)
115
Where does the spinal cord end?
Inferior border of L1
116
Where does the spinal cord lie?
Within a meningeal sac that fits within the spinal cavity
117
CSF
Cerebrospinal fluid
118
Where is the CSF in the spinal cord?
Filling the meningeal sac
119
Purpose of CSF in spinal cord
Act as gel cushion for spinal cord
120
Conus medularis
Non-neural tissue which attached filium terminale
121
Filium terminale
Fibrous non-neural tissue which anchors the spinal cord to the coccygeal vertebrae
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How many segments of spinal nerves are there?
31
123
How many segments of spinal nerves in the cervical part are there?
8
124
Cauda equina
The group of spinal nerves which have to descend from L1 to their exit vertebrae
125
Dorsal/ posterior column
Region of white matter in the spinal cord which lies between the dorsa horn and the posterior median sulcus
126
Ventral column
Region of white matter in the spinal cord which lies between the ventral horn and the ventral median fissure
127
Lateral column
Region of white matter in the spinal cord which lies between the ventral and dorsal columns
128
Doral median sulcus
Central furrow in posterior region of spinal cord
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Ventral median fissure
Deep sulcus (furrow) in the anterior region of the spinal cord
130
Central canal
Canal in centre of spinal cord
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Three horns of grey matter in the spinal cord
Dorsal lateral and ventral horns
132
Which section of the spinal cord is associated with efferent division?
Ventral- information moves out
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Which section of the spinal cord is associated with the afferent division?
Dorsal- sensory, information moves into spinal cord
134
What does damage to the dorsal section of the spinal cord cause?
Paralysis of muscles- somatic motor neurons can’t function
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What does damage to the ventral section of the spinal cord cause?
Loss of sensation- sensory neurons affected
136
Where do somatic motor neurons lie in the spinal cord? Is it their axons or cell bodies?
Ventral horn
| Cell bodies
137
Where do autonomic motor neurons lie in the spinal cord? Is it their cell bodies or axons?
Lateral horn
| Cell bodies
138
Where do motor commands leave the spinal cord from?
Ventral nerve root
139
Where in the spinal cord do the cell bodies and axons of sensory neurons lie?
Cell bodies in dorsal root ganglion
Axons in dorsal nerve root
140
How does sensory information enter the spinal cord?
Through the dorsal nerve root
141
Dorsal nerves carry _____ information?
Afferent
142
Ventral nerves carry _____ information?
Efferent
143
Three branches from spinal nerve
Dorsal ramus
Anterior ramus
Rami communicantes
144
Dorsal ramus innervates ___?
The back
145
Ventral ramus innervates ___?
The front and limbs
146
Which spinal nerves are rami communicantes present in?
T1-L2
147
Which kind of axons do rami communicantes contain?
Autonomic sympathetic
148
Layer covering axon
Endoneurium
149
Axons bundle to form ____?
Fasicle
150
Fasicle is covered with _____? (Neural)
Perineurium
151
Fasicles are bundled with ____ to form a ____? (Neural)
Blood vessels
| Nerve
152
Layer covering a nerve
Epineurium
153
Three layers of the meninges
Dura mater
Arachnoid layer
Pia mater
154
Outermost layer of the meninges
Dura mater
155
Function of dura mater
Dense and fibrous- acts as first line of defence for the brain of cranium fractures
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How many layers does the dura mater have?
Two- outer and inner
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Space between two dura mater layers where they split
Venous sinuses
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What forms the dura folds?
Inner layer of dura mater
159
Three features of the dural folds
Formed from inner layer of dura mater
Separate major divisions of the brain
Provide stability of the brain within the cranium
160
Three dural folds
```
Falx cerebri (big sickle)
Falx cerebelli (smaller sickle)
Tentorium cerebelli (tent)
```
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Where does the falx cerebri sit?
Between cerebrum in median/ sagittal plane
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Where does the falx cerebelli sit?
Between cerebelli hemispheres in the sagittal/ median plane (below falx cerebri)
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Where does the tentorium cerebelli lie?
Separating the cerebrum from the cerebellum in the horizontal plane
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Three features of venous sinus
Located where the two layers of dura mater separate
Collecting veins
Collecting venous blood from the brain and old CSF from the ventricular system
165
Venous blood
Deoxygenated blood
166
Which is the ‘spider-like’ layer and why is it called this?
Arachnoid layer
| Sits up on ‘legs’ and has a webbed pattern
167
Five features of arachnoid
Beneath dura mater
Above Pia mater
Contains subarachnoid space and arachnoid granulation a
Contains blood vessels within subarachnoid space
Does not extend into sulci (like Pia)
168
Where is the subarachnoid space and what fills it?
Between arachnoid and Pia mater
| CSF
169
Function of arachnoid granulations
Perforate the inner layer of dura mater to transport old CSF from subarachnoid space into the venous sinus
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Four features of Pia mater
Inner layer of the meninges
Transparent and delicate
Provides cushion for blood vessels in arachnoid
Adheres to brain and follows gyri- extends into sulci
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Four features of the ventricular system
Network of interconnected ventricles within the brain
Filled with CSF (nourishes and protects brain)
Ependymal cells lining the ventricles, circulating CSF
CSF is produced by choroid plexus
172
Ventricles (5)
2 lateral ventricles (one in each cerebral hemisphere)
Third ventricle (in the diencephalon)
Central aqueduct (midbrain)
Fourth ventricle (level with cerebellum)
(Also central canal)
173
How does CSF circulate the ventricle system and what are its two main purposes?
```
Lateral ventricles to
third ventricle to
cerebral aqueduct to
fourth ventricle to
subarachnoid space
```
Then it flows around the brain and spinal cord in the subarachnoid space
Ends in venous sinuses (through arachnoid granulations)
174
Name the lobes of the brain (4)
Frontal
Parietal
Occipital
Temporal
175
Which sulcus separates the frontal and parietal lobes?
Central sulcus
176
Which sulcus separates the parietal and occipital lobes?
Parietal-occipital sulcus
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Which sulcus separates the temporal lobe from the frontal and parietal lobes?
Lateral sulcus
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Which fissure separates the cerebrum from the cerebellum? What structure fits in this fissure?
```
Transverse fissure
Tentorium cerebelli (a dural fold)
```
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Function of frontal lobe (2)
Motor control
Somatosensory in the anterior part
180
Function of parietal lobe
Somatosensory
181
Function of occipital lobe
Vision
182
Functions of temporal lobe (2)
Memory
| Hearing
183
Name the seven internal structures of the brain
```
Cerebral cortex
Corpus callosum
Diencephalon
Cerebellum
Midbrain
Pons
Medulla oblongata
```
184
Two parts of the diencephalon
Thalamus and hypothalamus
185
Three parts of the brain stem
Midbrain
Pons
Medulla oblongata
186
Most superior internal structure of the brain
Cerebral cortex
187
Most inferior structure of the brain
Brain stem (medulla oblongata)
188
Three types of white matter in the brain
Commissural tracts
Projection tracts
Association tracts
189
Commissural tracts
White matter in which axons cross sides of the brain
190
Projection tracts
Whyte matter in which axons extend from the cortex into other areas of the CNS
191
Association tracts
White matter in which axons extend to another area in the brain on the same side
Allows for communication between brain areas
192
Deep nuclei
Are they darker or lighter?
Structures in the brain containing cell bodies
Darker
193
Gyri next to central sulcus (2)
Precentral gyrus
| Postcentral gyrus
194
Pre-central gyrus
Gyrus of motor cortex next to the central sulcus
195
Post-central gyrus
Gyrus of the somatosensory cortex next to the central sulcus
196
Corticospinal pathway
Two neurons between brain and effector
197
Describe neurons of the corticospinal pathway
Upper motor neuron:
- cell body in precentral gyrus (primary motor cortex)
- axon extends to spinal cord on opposite side
- synapses on lower motor neuron
Lower motor neuron:
- cell body in ventral horn of spinal cord
- axon extends out of ventral root into PNS
- synapses on skeletal muscle
198
Dorsal/ posterior column pathway
Three neurons between sensory receptors and somatosensory neuron in postcentral gyrus
199
Describe the neurons in the dorsal/ posterior column pathway
Neuron 1: (unipolar)
- cell body in dorsal root ganglion
- peripheral fibre from sensory receptors in skin
- central fibre ascends in dorsal columns
- synapses on neuron 2 in medulla oblongata
Neuron 2:
- cell body in medulla oblongata
- axon crosses to opposite side of spinal cord and ascends
- synapses on neuron 3 in thalamus
Neuron 3:
- cell body in thalamus
- axon ascends to somatosensory cortex
- synapses on cell body of somatosensory cortex neuron
200
What will damage to the primary motor cortex cause?
Paralysis and muscle weakness for the corresponding area on the opposite side of the body
201
What will damage to the primary somatosensory cortex cause?
Loss of sensation/ no perception of touch in the corresponding area on opposite side of the body
Because information has nowhere to go
202
Describe five steps of the reflex arc
1. Stimulation of receptor
2. Activation of sensory neuron
3. Information processing in the CNS
4. Activation of motor neuron
5. Response of peripheral effector
203
Spinal reflex
Name two types
An automatic response to a particular stimulus
Stretch
Withdrawal
204
Stretch reflex
A spinal reflex that regulates muscle length through stimulation of the muscle spindle
205
What surrounds the muscle spindle?
Muscle fibres
206
How many synapses in the stretch reflex?
One- between sensory and motor neurons
207
Withdrawal reflex
Spinal reflex which protects the body from damaging stimuli
208
How many synapses in the withdrawal reflex?
Two: sensory neuron to inter neuron
Interneuron to motor neuron
209
What is the role of the interneuron in the withdrawal reflex?
Converts the excitatory input from the sensory neuron into inhibitory input into motor neuron on extensor muscles
While relaying excitatory input onto motor neuron on contracting muscle
210
Role of muscle spindle
Regulate length of muscle fibres
211
How is work distributed over a muscle?
Each motor unit relaxes while others are stimulated, before it is recruited again
212
Which three regions of the brain are involved in preparation for movement?
Frontal lobes
Premotor cortex
Cerebellum
213
Main function of cerebellum
Prepares and performs movement
214
How does the cerebellum assist movement? (4)
Coordinates muscles- guided by sensory feedback
Compares intended movement with actual result
Helps maintain posture and gaze
Helps learn and automate movements
215
What causes ‘drunken gait’?
Damage to the cerebellum
216
What shape are sensory neurons?
Unipolar
217
Where does sensory input enter the axon?
Dendrites
218
5 special senses
```
Vision
Hearing
Taste
Smell (pheromones)
Vestibular (balance)
```
219
4 somatic & visceral sensations
Touch
Pain
Warm and cold
Body position
220
Role of sensory receptor
Transduces information to neuron by converting physical energy into AP
221
How can we describe a sensory stimulus (4)
Modality
Intensity
Duration
Location
222
Modality
Type of sensory receptor activated
223
Intensity (sensory information)
Frequency of action potential firing in afferent neuron
224
Duration (sensory information)
Duration of action potential in firing afferent neuron
225
Location (sensory information)
Location of sensory receptor(s) activated, mapped in the brain
226
Is there a sensory receptor on a muscle spindle?
No. The axon of the sensory neuron wraps around the spindle
227
Receptive field
Region of space on the body surface in which a stimulus can lead to activity in a particular afferent neuron
228
What will activate more than one receptive field?
A stronger stimuli
229
What does a small receptive field provide?
Good discrimination between stimuli
230
‘labelled line’
Label on the sensory axon saying where the ap has come from
231
Function of somatic sensory association cortex
Generates conscious sensation from action potentials
232
Sensation vs perception
Sensation is conscious identification of what and where. Occurs in primary region of somatosensory cortex.
Perception is meaningful interpretation of the sensation. Occurs in the association region of the somatosensory cortex
233
Do densely innervated areas of the body occupy small or large regions of the somatosensory cortex?
Large regions
