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HUBS191 > Nerve and Muscle > Flashcards

Nerve and Muscle Flashcards

1
Q

What does the central nervous system consist of

A

The brain and spinal cord

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2
Q

What does the peripheral nervous system consist of

A

Peripheral nerves and ganglia

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3
Q

What are the two types of cells in the nervous system

A

Neurons and glia

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4
Q

Neuron definition

A

Cells specialised for transmission of information

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5
Q

How many types of neurons are there

A

4

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6
Q

What is the function of glia

A

Support for neurons

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7
Q

How many types of glia are there

A

5 (4 in CNS, 1 in PNS)

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8
Q

Dendrites function

A

Receive input, send info to cell body

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9
Q

Cell body of neuron function

A

Contains nucleus and organelles, sums input

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10
Q

Axon function

A

Carries electrical impulses

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11
Q

Axon terminals function

A

End of axon, releases neurotransmitter

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12
Q

Groups of cell bodies in the CNS

A

Nuclei

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13
Q

Bundle of axons in the CNS

A

Tract

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14
Q

Group of cell bodies in the cerebral cortex or spinal cord

A

Grey matter

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15
Q

Bundle of axons in cerebral cortex or spinal cord

A

White matter

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16
Q

Group of cell bodies in the PNS

A

Ganglion

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17
Q

Bundle of axons in the PNS

A

Nerve

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18
Q

Input zone of neuron

A

Dendrites, cell body, receives chemical signals

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19
Q

Summation zone of neuron

A

Axon hillock, sums inputs

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20
Q

Conduction zone of neuron

A

Axon, carries electrical signals

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21
Q

Output zone of neuron

A

Axon terminals, contact with input zone of other neurons or effectors, release of neurotransmitter

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22
Q

4 types of neurons

A

Multipolar, bipolar, unipolar, anaxonic

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23
Q

CNS glia types

A

Astrocytes, microglia, ependymal cells, oligodendrocytes

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24
Q

Astrocytes function

A

Supply nutrients to neurons, ensheath blood capillaries, injury response

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25
Q

Microglia function

A

Immune cells of CNS, engulf microorganisms and debris

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26
Q

Ependymal cells function

A

Line fluid filled spaces of brain and spinal cord, have cilia to circulate CSF

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27
Q

Oligodendrocytes function

A

Support nerve fibres, ensheath with myelin

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28
Q

PNS glia name and function

A

Schwann cells: support peripheral nerve fibres, ensheath with myelin

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29
Q

What is a myelin sheath

A

Lipid (fat) wrapped around an axon (membrane wrapped around many times)

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30
Q

Gaps between schwann cells

A

Nodes of ranvier

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31
Q

Purpose of myelin sheath

A

Increase conduction velocity

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32
Q

Afferent

A

Information going into the brain

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33
Q

Efferent

A

Information leaving the brain

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34
Q

Effectors

A

Cells in the body that respond in some may to neural input (e.g muscle fibre)

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35
Q

Receptors

A

Where information about stimuli comes into the body

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36
Q

Somatic

A

Stuff we are aware of, voluntary (efferent), sensory information (afferent)

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37
Q

Autonomic

A

Stuff we are not aware of, have no control over, involuntary muscle control (efferent), sensory information we don’t know about (afferent)

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38
Q

Somatic efferent neural organisation

A

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

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39
Q

Two divisions of autonomic efferent nervous system

A

Sympathetic, parasympathetic

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40
Q

Autonomic efferent effectors

A

Smooth muscle, cardiac muscle, glands, adipose tissue

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41
Q

Autonomic efferent neural organisation

A

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)

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42
Q

Autonomic ganglion

A

Collection of neuron #3 cell bodies in autonomic system

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43
Q

Sympathetic

A

Fight or flight

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44
Q

Parasympathetic

A

Rest and digest

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45
Q

Structural differences between sympathetic and parasympathetic nervous systems

A

Sympathetic: neuron 2 short (Ach), neuron 3 long (NE)
Parasympathetic: neuron 2 long (Ach), neuron 3 short (Ach)

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46
Q

Sympathetic ganglion location

A

Close to CNS

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47
Q

Para sympathetic ganglion location

A

Far from CNS

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48
Q

Sympathetic neuron #2 cell body location

A

Thoracolumbar region of spinal cord

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49
Q

Sympathetic chain ganglia location

A

Either side of vertebral column, 21-23 pairs

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50
Q

Parasympathetic neuron #2 cell body location

A

Cranial or sacral region

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51
Q

Synapse definition

A

Connection and communication point between a presynpatic and postsynaptic cell

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52
Q

Synaptic transmission

A

The process by which a presynpatic neuron releases a neurotransmitter which diffuses across cleft. Neurotransmitter binds to receptors/ion channels on post synaptic neuron

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53
Q

How does a chemical signal get converted into an electrical signal?

A

Chemically gated ion channels opened by neurotransmitter, local depolarisation to threshold (-60mV)

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54
Q

Chemically gated stimulus

A

Chemical (neurotransmitter)

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55
Q

Voltage gated stimulus

A

Voltage (depolarisation to -60mV)

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56
Q

Mechanically gated stimulus

A

Membrane deformation

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57
Q

Where are chemically gated channels on a neuron

A

Dendrites and cell body

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58
Q

Where are voltage gated channels on a neuron

A

Axon hillock, axon, axon terminals

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59
Q

What causes a voltage gated ion channel to open?

A

Membrane depolarisation to -60mV

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60
Q

Why is the RMP -70mV

A

Lots of negatively charged proteins, Na+/K+ exchange pumps, 3Na+ out for every 2K+ in

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61
Q

What is a local potential

A

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)

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62
Q

What is an excitatory local potential (EPSP)?

A

Depolarisation of the cell membrane due to a presynaptic neuron releasing an excitatory neurotransmitter (Ach or NE) which opens chemically gated Na+ channels

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63
Q

What is an inhibitory local potential (IPSP)?

A

Hyperpolarisation of the cell membrane due to a presynaptic neuron releasing an inhibitory neurotransmitter (GABA) which opens chemically gated K+ channels

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64
Q

What is spatial summation

A

Summed input from multiple presynaptic neurons

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65
Q

What is temporal summation

A

Summed input from repeated firing of one presynaptic neuron

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66
Q

Why are presynaptic neurons summed at the axon hillock

A

High density of voltage gated channels

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67
Q

Why does rapid depolarisation occur in an action potential

A

Voltage gated Na+ channels open when membrane depolarises to -60mV

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68
Q

At what voltage do voltage gated Na+ channels inactivate and K+ channels (finally) open in an action potential

A

+30mV

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69
Q

Why does repolarisation occur in an action potential

A

K+ channels open and Na+ channels close

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70
Q

Why does hyperpolarisation occur in an action potential

A

K+ channels close slowly resulting in excess K+ leaving the cell

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71
Q

At what voltage do voltage gated K+ channels finally close

A

About -90mV

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72
Q

Conduction zone of the neuron

A

Axon

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73
Q

Output zone of the neuron

A

Axon terminals (release neurotransmitter)

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74
Q

How does an electrical signal trigger a chemical signal

A

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

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75
Q

Absolute refractory period

A

Rapid depolarisation and repolarisation of cell membrane

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76
Q

Relative refractory period

A

Hyperpolarisation of cell membrane

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77
Q

How long is each myelination

A

Perfectly spaced for amount of sodium needed to cause next node voltage gates to open

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78
Q

When can a second AP be generated during propagation

A

During relative refractory period, only if stimulus is much larger than normal (lots more sodium)

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79
Q

What state must voltage gated Na+ channels be in in order to open

A

Closed

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80
Q

What channels are on the post synaptic cell membrane

A

Chemically gated ion channels

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81
Q

What enzymes are present in the synaptic cleft

A

Enzymes that inactivate neurotransmitter

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82
Q

Ca2+ is always…

A

Excitatory: something is going to move

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83
Q

What does Ca2+ trigger in presynaptic axon terminal

A

Movement of synaptic vesicles, causing them to release neurotransmitter

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84
Q

Excitatory neurotransmitters

A

Ach, NE (noradrenaline)

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85
Q

Inhibitory neurotransmitter

A

GABA

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86
Q

Synaptic transmission ends when

A

Neurotransmitter unbinds from chemically gated channels, enzymes in synaptic cleft degrade neurotransmitter and recycled back into axon terminal

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87
Q

Cholinergic synapse

A

Ach is the neurotransmitter

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88
Q

Summation at neuromuscular junction

A

Not usually needed, one synaptic transmission generally results in muscle membrane brought to threshold

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89
Q

Electrical synapse downfall

A

No opportunity for signal modulation as gap junctions connect pre and post synaptic neurons

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90
Q

Where does the spinal cord end

A

Inferior border of 1st lumbar vertebra (L1)

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91
Q

Where does the spinal cord go in vertebrae

A

Through the spinal canal

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92
Q

Which side of the vertebrae have spinous processes

A

Dorsal

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93
Q

How far does the spinal cavity extend

A

All the way to coccygeal vertebrae

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94
Q

What is the spinal cord contained within

A

Meningeal sac filled with CSF

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95
Q

What is the end of the spinal cord tapered into

A

Conus medularis (non neural tissue)

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96
Q

What anchors the spinal cord in place

A

Filum terminale (fibrous, non-neural tissue)

97
Q

How many segments does the spinal cord have

A

31

98
Q

How many pairs of spinal nerves does each region of the spinal cord have

A

Cervical: 8, thoracic: 12, lumbar: 5, sacral: 5, coccygeal (1)

99
Q

Where do spinal nerves exit (with one exception)

A

Below the vertebrae they’re named after. EXCEPT for first cervical spinal nerve which exits between the skull and first cervical vertebra

100
Q

Name for large collection of nerves inferior to end of spinal cord

A

Cauda equina

101
Q

Posterior feature of spinal cord

A

Median sulcus

102
Q

Anterior feature of spinal cord

A

Median fissure

103
Q

What is in the centre of the spinal cord

A

Central canal

104
Q

What is the dorsal horn made up of

A

Cell bodies

105
Q

What is the dorsal column made up of

A

Sensory nerve axons

106
Q

What is the ventral horn made up of

A

Motor nerve cell bodies (specifically somatic motor neurons)

107
Q

What is the ventral column made up of

A

Motor nerve axons

108
Q

What is the lateral horn made up of

A

Cell bodies

109
Q

What is the lateral column made up of

A

Axons

110
Q

What is the dorsal nerve root made up of

A

Sensory nerve axons

111
Q

What is the dorsal root ganglion made of

A

Sensory nerve cell bodies

112
Q

What is the ventral nerve root made up of

A

Motor nerve axons

113
Q

What are spinal nerves made up of

A

Combination of dorsal and ventral nerve roots (sensory and motor, efferent and afferent)

114
Q

What would happen if there was damage to the ventral horn?

A

Paralysis of muscles supplied by somatic motor neurons from this segment, same side only

115
Q

What type of neurons are in the dorsal root ganglion

A

Unipolar (sensory neurons)

116
Q

What would happen if there was damage to the dorsal horn?

A

Loss of sensation from regions of the body supplied by sensory neurons from this spinal cord segment, same side only

117
Q

What does the spinal nerve branch into

A

Dorsal and ventral rami (to corresponding regions of the body), and rami communicans and sympathetic ganglion

118
Q

Where are rami communicans

A

Only at T1-L2

119
Q

What connective tissue are axons covered in

A

Endoneurium

120
Q

What connective tissue are fascicles covered in

A

Perineurium

121
Q

What connective tissue are nerves covered in

A

Epineurium

122
Q

Bundles of axons in the CNS are called a

A

Tract

123
Q

What are the three layers of the meninges

A

Dura mater, arachnoid and pia mater

124
Q

What are the features of the dura mater

A

Outermost layer, dense and fibrous, two layers (inner and outer), space between forms venous sinuses, inner layer forms dural folds

125
Q

Name the three dural folds

A

Falx cerebri, falx cerebelli, tentorium cerebelli

126
Q

Purpose of the dural folds

A

Separate major divisions of the brain, provide stability within cranium

127
Q

Falx cerebri

A

Dural fold that separates hemispheres of the cerebrum (median plane)

128
Q

Falx cerebelli

A

Dural fold that separates hemispheres of the cerebellum (median plane)

129
Q

Tentorium cerebelli

A

Dural fold that separates the cerebrum from the cerebellum (horizontal plane)

130
Q

Purpose of venous sinuses

A

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
Q

Arachnoid features

A

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
Q

What are venous sinuses

A

Gap between inner and outer layers of dura mater

133
Q

Subarachnoid space

A

Between arachnoid and pia mater, filled with cerebrospinal fluid, contain blood vessels

134
Q

Arachnoid granulations

A

One way valves which perforate inner layer of dura mater and transport old CSF from subarachnoid space into venous sinus

135
Q

Pia mater features

A

Innermost layer of meninges, transparent and delicate, blood vessels sit on top, adheres to brain, follows gyri and extends into sulci

136
Q

What does the dura mater ensheath

A

Brain, spinal cord and spinal nerves

137
Q

Purpose of CSF

A

Nourishment (transports nutrients and waste) and protection (support and cushion)

138
Q

What does the choroid plexus do

A

Produces CSF

139
Q

Where is the choroid plexus

A

Within the ventricles (underneath lateral ventricles)

140
Q

What are the spaces of ventricles lined with

A

Ependymal cells

141
Q

What is the purpose of ependymal cells

A

Circulate CSF by waving cilia

142
Q

What ventricles make up the ventricular system

A

2 lateral ventricles, 1 third ventricle, cerebral aqueduct and fourth ventricle, and central canal of the spinal cord

143
Q

Where are the lateral ventricles located

A

One in each cerebral hemisphere

144
Q

Where is the third ventricle located

A

The diencephalon

145
Q

Where is the cerebral aqueduct located

A

Midbrain

146
Q

What does the cerebral aqueduct do

A

Connects 3rd to 4th ventricle

147
Q

Where is the fourth ventricle located

A

The level of the cerebellum

148
Q

How is old CSF removed

A

Recycled out in blood

149
Q

What is the order of circulation of CSF

A

Lateral ventricle -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> subarachnoid space (around brain and spinal cord) -> exits through arachnoid granulations into venous sinus

150
Q

Name the lobes of the brain

A

Frontal, parietal, occipital, temporal

151
Q

Sulcus

A

Valley

152
Q

Gyrus

A

Hill

153
Q

What does the central sulcus separate

A

Frontal and parietal lobe

154
Q

What separates the parietal and occipital lobes

A

Parieto-occipital sulcus

155
Q

What separates the temporal lobe from the frontal and parietal lobes

A

Lateral sulcus

156
Q

What separates the cerebrum from the cerebellum

A

Transverse fissure

157
Q

What functions are the frontal lobe associated with

A

Motor control, language, personality

158
Q

What functions are the parietal lobe associated with

A

Somatosensory

159
Q

What functions are the temporal lobe associated with

A

Memory and hearing

160
Q

What functions are the occipital lobe associated with

A

Vision

161
Q

What is the cerebral cortex

A

Outer layer of the cerebrum (grey matter)

162
Q

What is the diencephalon composed of

A

Thalamus and hypothalamus

163
Q

What is the corpus callosum made of

A

White matter

164
Q

What is the function of the corpus callosum

A

Connects the sides of the brain by commisural tracts

165
Q

What is the brainstem composed of

A

Midbrain, pons and medulla oblongata

166
Q

What are the central, deep structures of the brain called

A

Deep nuclei

167
Q

3 types of white matter

A

Commissural tracts, projection tracts, association tracts

168
Q

Function of commissural tracts

A

Cross from side to side of brain, both directions, connect

169
Q

Function of projection tracts and example

A

Axons between cortex and CNS areas outside cerebrum, e.g corticospinal tract

170
Q

Function of association tracts

A

Axons on same side within cerebral cortex, communication between brain areas, short or long distance

171
Q

Primary motor cortex (major cortical area for motor control)

A

Pre central gyrus

172
Q

Primary somatosensory cortex (major cortical area for somatosensory perception)

A

Post central gyrus

173
Q

What neurons are in the somatic efferent (motor) division

A

Upper and lower motor neuron, both myelinated

174
Q

What is the effector of the somatic efferent (motor) division

A

Skeletal muscle

175
Q

What is the neurotransmitter of the somatic efferent (motor) division

A

Acetylcholine

176
Q

Example pathway of the somatic efferent (motor) division

A

Corticospinal pathway

177
Q

Where is the upper motor neuron

A

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
Q

Where is the lower motor neuron

A

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
Q

What happens if the primary motor cortex is damaged

A

Muscle weakness and paralysis in region of body corresponding to location of damage, opposite side

180
Q

How many neurons are involved in the corticospinal pathway

A

2 (upper and lower motor neurons)

181
Q

How many neurons are involved in the dorsal column pathway

A

3, neurons 1, 2 and 3 (not including neuron cell body in somatosensory cortex)

182
Q

Where is neuron 1 of the dorsal column pathway (somatic afferent)

A

Dorsal root ganglion (unipolar), peripheral fibre extends to sensory recpetor, central fibre ascends in dorsal columns

183
Q

Where is neuron 2 of the dorsal column pathway (somatic afferent)

A

Medulla oblongata, axon crosses to other side and extends

184
Q

Where is neuron 3 of the dorsal column pathway (somatic afferent)

A

Thalamus, ascends to somatosensory cortex, synapses on cell body of somatosensory cortex neuron

185
Q

What happens if there is damage to the primary somatosensory cortex?

A

No perception of touch in the corresponding region of cortex, on the opposite side

186
Q

Where is the thalamus relative to the hypothalamus

A

Superior

187
Q

What are somatic senses

A

Detected by receptors in the skin, muscle and joints

188
Q

What are visceral senses

A

Detected by receptors in the internal organs

189
Q

What is sensory transduction

A

Conversion of a sensory stimulus into an action potential

190
Q

4 ways the brain interprets action potentials from sensory neurons

A

Modality, duration, intensity, location

191
Q

4 types of sensory receptors

A

Thermoreceptor, chemoreceptor, mechanoreceptor, nociceptor

192
Q

3 types of mechanoreceptors

A

Baroreceptor, proprioceptor, tactile receptors

193
Q

What do tactile receptors detect

A

Skin touch (light touch, pressure, texture, vibration, stretch) Some tonic some phasic

194
Q

What do proprioceptors detect

A

Proprioception (limb position related to torso), stretch or tension in skin, muscle and/or skin (tonic)

195
Q

What do baroreceptors detect

A

Pressure (stretch of visceral tubes e.g blood vessels, airways, intestines)

196
Q

Features of thermoreceptors

A

Nerve ending with temperature gated ion channels, respond to different temperatures and changes in temperature (phasic)

197
Q

Features of chemoreceptors

A

Specialised receptor cells with chemically gated ion channels, respond to different chemical concentrations

198
Q

Mechanoreceptor features

A

Nerve endings with mechanically gated ion channels

199
Q

Mechanoreceptor example

A

Muscle spindle (proprioceptor)

200
Q

Phasic meaning

A

Fast adapting

201
Q

Tonic meaning

A

Slow adapting

202
Q

Nociceptor features

A

Nerve endings that respond to noxious stimuli (excess temperature, chemical, mechanical stimuli) (Tonic)

203
Q

Phasic receptors

A

Normally silent, send APs with change but stop quickly

204
Q

Tonic receptors

A

Continually active to reflect background level of stimulation, AP frequency changes when stimulus intensity changes

205
Q

What is intensity of stimulus communicated by

A

AP frequency plus number of neurons activated

206
Q

What is a receptive field

A

The area of skin with receptive endings of a single sensory neuron

207
Q

Small and densely packed receptive fields provide

A

More sensitivity (better two point discrimination), more accurate localisation

208
Q

The pre and post central gyrus are mapped ______

A

Somatotopically

209
Q

Areas with large receptive fields have ____ representation in the brain because ________

A

Less, fewer neurons involved

210
Q

Which parts of the brain are involved in planning movement

A

Prefrontal cortex, premotor cortex

211
Q

What does the prefrontal cortex do in voluntary movement

A

Plans movements

212
Q

What does the premotor cortex do in voluntary movement

A

Sequences movements

213
Q

Which part of the brain is involved in initiating movement

A

Primary motor cortex

214
Q

What does the motor cortex do in voluntary movement

A

Produces specific movements

215
Q

Which parts of the brain are involved in modifying movement

A

Basal nuclei and cerebellum

216
Q

What is the function of the basal nuclei

A

Influences posture and automatic movements, regulates muscle tone, refines movements (selects which to allow and which to inhibit)

217
Q

How do the basal nuclei undertake their function of modifying movement

A

By altering sensitivity of neurons projecting into the corticospinal or other pathways

218
Q

What is the function of the cerebellum with relation to voluntary movement

A

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
Q

Where does the prefrontal cortex send signals to regarding voluntary movement

A

Premotor cortex

220
Q

Where does the premotor cortex send signals to regarding voluntary movement

A

Primary motor cortex, basal nuclei and cerebellum

221
Q

Where does the primary motor cortex send signals to regarding voluntary movement

A

Down corticospinal pathway

222
Q

Where do the basal nuclei and cerebellum send signals to regarding voluntary movement

A

Back and forth to each other, to frontal cortex and down descending pathways

223
Q

What is the corticospinal pathway

A

Pathway from primary motor cortex to effector muscle initiating voluntary movement

224
Q

What does the corticospinal pathway consist of

A

An upper and lower motor neuron

225
Q

What is a motor unit

A

A single lower motor neuron and all the skeletal muscle fibres it innervates

226
Q

What is a small motor unit

A

Single lower motor neuron and few muscle fibres it innervates (more precise)

227
Q

What is a large motor unit

A

Single lower motor neuron and many muscle fibres it innervates (more forceful)

228
Q

What characterises a voluntary movement

A

Wide variety of speed, duration and complexity, complex patterns of sensory and motor processing, variable latency (~100+ms), can be trained

229
Q

What characterises a reflex movement

A

Reproducible, automatic motor response to external stimulus, simple neural circuit within peripheral nerves and spinal cord, consistent latency (~40ms), can’t be trained

230
Q

Latency of variable movement

A

~100+ ms

231
Q

What is a stretch reflex

A

Recognition of sudden unwanted stretch and reflex to protect from tearing

232
Q

What is the structure of a muscle spindle

A

Dendritic endings (mechanically gated Na+ channels) of a sensory neuron wrap around specialised intrafusal muscle fibres

233
Q

What neurons are involved in the stretch reflex

A

Sensory neuron, motor neuron (synapse in spinal cord), interneuron in spinal cord which inhibits activation of motor neuron that innervates opposing muscles

234
Q

What is an interneuron

A

Neuron between motor and sensory in a reflex (can be excitatory or inhibitory). Any connector neuron that is neither sensory nor motor

235
Q

What is a withdrawal reflex

A

Reflex response to painful stimuli

236
Q

What neurons are involved in the withdrawal reflex

A

Sensory neuron, motor neuron (synapse in spinal cord), interneuron (excitation of motor neurons stimulating flexors, inhibition of motor neurons stimulating extensors)

237
Q

Somatic efferent and afferent synapses at medulla

A

Controlateral (swap sides)

238
Q

Generic function of thalamus

A

Gateway of sensation into the brain

239
Q

Where are autonomic neuron cell bodies located

A

Lateral horn

HUBS191 (7 decks)

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