Neurology And Neuroscience Flashcards
(172 cards)
1
Q
What is the most abundant cell type in the mammalian brain
A
Astrocytes
2
Q
What are the branches of axons called
A
Collaterals
3
Q
Name 5 cell types other than neurons found in the CNS/PNS
A
- Schwann cells
- oligodendrocytes
- Ependyma
- microglia
- astrocytes
4
Q
Functions of the cerebellum
A
Posture, balance, motor coordination
5
Q
Name 3 types of multipolar neurones
A
Pyramidal cells (pyramid shaped cell body) Purkinje cells (GABA neurons found in cerebellum) Golgi cells (GABA neurons found in cerebellum)
6
Q
Describe a multipolar neuron
A
Multiple projections from cell body - one is an axon, the rest are dendrites
7
Q
Describe a pseudo unipolar neuron
A
One axon projection which divides into 2
8
Q
How can you distinguish axons from dendrites
A
Axons are myelinated
Dendrites are not myelinated
9
Q
Function of dendrites
A
Receive signals from other neurons
10
Q
Describe resting charge of neuronal cell
A
Negative charge inside compared to outside
Resting membrane potential of -70 mV
11
Q
Why do people with multiple sclerosis get movement and visual problems
A
Multiple sclerosis results in the loss of the myelin from the axons of neurons
Visual problems: neurons in eye can’t transmit signals to brain fast enough
Movement problems: neurons in brain can’t transmit signals to muscles fast enough
12
Q
What are the three types of synaptic organisation
A
Axodendritic synapse: between axon (presynaptic terminal) of one neuron and dendrites of another neuron
Axosomatic synapse: between axon (presynaptic terminal) of one neuron and soma (cell body) of another neuron
Axoaxonic synapse: between axon (presynaptic terminal) of one neuron and axon of another neuron
13
Q
What is the sarcoplasmic reticulum, what is its location function and effect
A
Location = surround myofibrils in sarcoplasm (inside of muscle membrane) Function= stores Ca2+ and releases them when sarcolemma is depolarised Effect = myofibril and muscle contraction
14
Q
What are T tubules
A
Continuous with the sarcoplasm and closely connected to sarcoplasmic reticulum and myofibrils.
When action potential depolarises sarcoplasm, it goes through T tubules to depolarise the myofibrils- causes muscle contraction
15
Q
Describe sequence of events from action potential in pre synaptic terminal to muscle contraction
A
AP is propagated along membrane by Na+ and K+ voltage gated channels
When AP reaches the pre synaptic membrane, it causes Ca2+ channels to open and Ca2+ influx into the axon. This causes the vesicles contains Ach to fuse with the membrane and release the Ach into synapse
Ach diffuses across synapse and binds to nicotinic Ach receptors on skeletal muscle, causing influx of Na+ which depolarises the sarcolemma - called the End Plate Potential (EPP)
The AP then travels down T tubules which are continuous with the sarcolemma to the myofibrils which are covered by the sarcoplasmic reticulum.
This causes Ca2+ ions to enter the cell thriugh L type calcium channels. They then bind to Ryanodine receotors on the sarcoplasmic reticulum
This causes release of Ca2+ by the sarcoplasmic reticulum which causes the muscle to contract - bind to Troponin C on actin filament, causing Tropomyosin to move and expose actin binding sites. Mysoin binds to actin, muscke fibres can shorten —> muscle contraction
16
Q
What happens when only a small amount of Ach is released into neuromuscular junction
A
Get a miniature EPP and muscle movement instead of full contraction
17
Q
What is Botulism
A
Botulinum toxin irreversibly disrupts stimulation-induced release from presynaptic terminal Ach - prevents vesicles fusing with presynaptic membrane
18
Q
Name two autoimmune disorders of the neuromuscular junction
A
Myasthenia Gravis
Antibodies directed against nicotinic acetyl choline receptors causing them to degrade
Get fatigable muscle weakness (ie becomes worse with repetitive use) facial muscle weakness and droopy eyelids
Lambert-Eaton Myastenic syndrome (LEMS)
Antibodies directed against voltage gated calcium channels causing them to degrade
Get muscle weakness but not so much on the face
19
Q
Which condition is described below
A 58 year old male presents with generalised fatigue and weakness. He has had
weight loss and difficulty raising his arms above his head. He has pelvic and
shoulder weakness and mild facial muscle weakness.
A
Lambert-Eaton myasthenia syndrome
Similar presentation to myasthenia graves but mild facial muscle weakness suggests it’s LEMS
20
Q
Main functions of parietal frontal temporal and occipital lobes
A
Frontal: executive actions - personality
Occipital: processing visual information
Temporal: contains important structures such as hippocampus (short term memory), amygdala (behaviour), Wernicke’s area (auditory perception and speech)
Parietal: somatic sensory cortex - processing tactile (touch) information
21
Q
3 structures that make up brain stem in order going down
A
Midbrain Pons Medulla
22
Q
Function of Astrocytes
A
Most common cells in mammalian brain
Structural role
Cell repair, neuronal maturation, neuronal plasticity, synapse formation
23
Q
Function of oligodendrocytes and Schwann cells
A
Oligodendrocytes
- myelinate neurons of CNS
- one can myelinate many axons, there many projections from the cell body which can myelinate internodes of many neurons
Schwann cells
- myelinate neurons of PNS
- one can only myelinate one axon segment
24
Q
Function of Microglia
A
Immune cells of CNS
similar to macrophages
25
Ependyma cells
Endothelial cells
| Line fluid filled ventricles which regulate production and movement of cerebrospinal fluid
26
Flux meaning
Flux = The number of molecules
that cross a unit area per unit
of time (number of particles).
i.e. molecules.m-2.s-1
27
What is overshoot
Membrane potential becomes positive
28
Describe how the changes in membrane potential affect the ion channels
Depolarisation: ion channel opens and allows flow of ions through
Sustained depolarisation: ion channel is inactivated - no more ions can flow through
Hyper-polarisation/re polarisation: ion channel is closed
29
What is the refractory period
The period after the peak of the action potential is reached when the Na+ channels are inactivated and closed. During this period they cannot be reactivated and opened so the cell cannot be re stimulated
30
What is the relative refractory period
Some Na+ channels have recovered from activation and reopened
But a stronger than normal stimulus is required to trigger an action potential
31
Does the decay of an AP happen quicker in smaller or larger neurone and why
Happens more quickly in a smaller neurone as the smaller diameter means that it has more resistance
Happens even quicker if the neurone is uninsulated as it would have no insulation
32
What are the three main factors that influence the
| movement of ions across the membrane?
Concentration of the ion on both sides of the membrane,
the charge on the ion and the voltage across the
membrane.
The membrane potential
33
Why is the K+ equilibrium potential negative (e.g. -70mV)
and the Na* equilibrium potential positive(e.g. +40mV)
when both are positive ions?
More K* inside the cell than outside so tend to flow out of
the cell, while more Na* outside the cell than in, therefore
tend to flow into the cell. A potential of -70mV is needed
to attract K* and stop net outward flow, while a positive
charge of +40mV is needed to repel Na* from entering the
cell.
34
What factors influence the speed of propagation of an action potential
along an axon?
Larger diameter axons have lower resistance, so ions move faster
conduction velocity is proportional to the square root of the axon
diameter.
There is a linear relationship between conduction velocity and myelin
thickness
35
What is passive propagation
There is a stimulus and further and further down the axon the voltage measured decreases - voltage decays away exponentially down the axon
(The speed of the decay depends on myelination and axon diameter)
36
Which types of compounds can opioid receptors respond to
```
Exogenous compounds eg heroin/morphine
Endogenous compounds (produced by body) eg endorphins
```
37
What are 3 reasons people take heroine. For each effect name the part of the brain contains the opioid receptors that the heroine acts on
Analgesia (pain relief) - Peri-aqueductal region
Euphoria - Ventral tegmental region
Cough suppression - solitary nucleus
38
4 main protein targets for drugs
Enzymes
Ion channels
Transport proteins
Receptors
39
2 types of actions of drugs on a target
Enhance activation - stimulate an effect
| Prevent activation - block an effect from being produced
40
Atorvastatin: what is its target type and what type of effect does it have in the target?
Target = enzyme
Action = prevents activation
(inhibits hmg coA reductase)
Lowers cholesterol
41
Amlodipine: what is its target type and what type of effect does it have in the target?
Target = ion channel
Action: prevents activation
(Blocks Ca2+ channels)
Treats high blood pressure and coronary heart disease
42
Salbutamol: what is its target type and what type of effect does it have in the target?
Target = receptor
Action = enhances activation
(Activates/Stimulates beta 2 receptors)
Is a short acting beta 2 adrenergic receptor agonist which causes relaxation of airway smooth muscle: treatment for asthma
43
Citalopram: what is its target type and what type of effect does it have in the target?
Target = transporter protein
Action = prevents activation
(Blocks serotonin re uptake protein)
Treats low mood and panic attacks
44
Noradrenaline, serotonin and dopamine all have similar structures so their receptors also have similar structures. However, why might selectivity be more important for drugs than for endogenous compounds?
Endogenous compounds like neurotransmitters (domaine, serotonin, noradrenaline) are released from pre synaptic terminal and travel across v short distance of the synapse to post synaptic terminal
So they are very specifically delivered to their drug target, making the selectivity and fact that they are similarly structured (so could theoretically bind to wrong target) less relevant or important.
Drugs are usually taken orally and travel in the blood I order to be distributed to the tissue where they produce the desired effect
But due to their method of administration and transmission they will come into contact with all tissue types
45
What is an adverse effect
Side effect with negative health consequences
46
How is drug safety linked to dose
-The safest drugs are the ones where there is a large difference in the dose required to produce a therapeutic effect and the dose required to produce an adverse effect
- as you start to increase the dose, the side effects usually increase as you lose selectivity.
Eg Pramipexole (dopamine agonist - mimics effects of dopamine)
As you increase the dose you can start to see noradrenaline and serotonin side effects too (as dopamine and therefore Pramipexole have similar structure to serotonin and noradrenaline) so bind to their receptors - if there’s enough Pramipexole, enough will bind to generate these side effects
47
2 types of side effects
```
Off target side effects
Eg Pramipexole (dopamine agonist) activating serotonin and noradrenaline receptors
```
Unwanted effects on the same target
Eg might want only the domaine effects in a certain part of the brain by taking Pramipexole, but will get effects in all parts of the body and brain that have the dopamine target as the Pramipexole will act in them all
Eg may only want the cough suppression from heroin but will get euphoria and analgesia too as heroin acts all the opioid receptors in all parts of the brain
48
What are the main 3 steps of signal transmission
Information reception
Information integration (cell body integrates all the different signals it receives from different neurons)
Information transmission - rapid transfer
49
3 main types of molecules which can be neurotransmitters
1) Amino acids
Eg glutamate, GABA, glycine
2) amines
Eg Noradrenaline
Dopamine
3) neuroproteins
Eg opioid peptides - endorphins, enkephalins
50
What is the main inhibitory and excitatory neurotransmitter in the brain
```
Excitatory = glutamate
Inhibitory = GABA
```
51
Is glycine an excitatory or inhibitor amino acid
Inhibitory
52
2 ways of inactivating transmitter after signal has been transmitted across synapse
1) enzymatic degradation within the synaptic cleft
| 2) re uptake of neurotransmitters back 8 to pre synaptic terminal and packaging into vesicles - reuse
53
Describe the process of neurotransmitter release
Membrane depolarisation
Ca2+ influx
Causes the docking (mediated by vesicular proteins) of vesicles
Followed by priming of vesicles
Followed by fusion of vesicles with membrane
Vesicles release neurotransmitters into synapse by exocytosis
(Process of fusion an exocytosis is mediated by vesicular proteins, proteins in cytoplasm, proteins on membrane)
(Electrochemical transduction is the process up to here from Ca2+ influx and lasts 200 us)
The vesicles are then budded (pinched off) and recycled/reused
54
What are SNARE proteins, give examples, and what is their role
They are vesicular proteins eg Synapsin, Synaptobrevin, SNAP 25
They are important in mediating process of exocytosis release of neurotransmitter
55
How does rapid release of neurotransmitters in response to Ca2+ influx happen
Vesicle docking, priming, fusion and neurotransmitter exocytosis are mediated by vesicular proteins, cytoplasm proteins and proteins on membrane
56
What are neurotoxins and give some examples of how they work
Toxins which interfere with synaptic vesicles and neurotransmitter release
Eg can break down vesicles whilst they’re still in presynaptic terminal
Eg can can cause excessive neurotransmitter release and subsequent depletion of neurotransmitters in pre synaptic nerve terminal
Eg can inhibit neurotransmitter release
57
Describe the actions of botulinum toxin as a neurotoxin
Made of 2 chains (bi-chained) and acts on cholinergic nerves
One chain binds to presynaptic membrane and one chain penetrates the membrane and cleaves the peptide bonds in the vesicular proteins which inactivates the vesicles - preventing docking, fusion and release of Ach
This causes flaccid paralysis (paralysis due to complete muscle relaxation)
In high conc, it can inhibit all cholinergic transmission and cause respiratory arrest
58
Describe the effects of Alpha Latrotoxin as a neurotoxin
From black widow spiders
Acts in cholinergic nerves
Stimulates massive release of Acetylcholine until the nerve is completely depleted of Ach
Causes muscular paralysis
59
Describe effects of Zn2+ endopeptidases
Inhibit neurotransmitter release
Eg Tetanus toxin produced by C tetani
Inhibits releases of 2 main inhibitory neurotransmitters in CNS: glycine and GABA
Causes spasms and paralysis
60
2 things that release of neurotransmitters is dependent on
ATP
| Ca2+
61
What are Convulsions
When muscles contract and relax quickly causing uncontrollable shaking of the body - seizure activity
62
What is the telencephalon also known as
Cerebral hemisphere
63
Fucntion of the parietal lobe
Somatic sensory cortex responsible for processing tactile info
64
3 main structures of the brainstem in descending order
Midbrain
Pons
Medulla
65
Where is the brainstem and what is its overall function
Dorsal region of CNS
| roles in motor coordination, balance and posture
66
What are the functions of oligodendrocytes and schwann cells and whats the difference between them
Bith are myelin producing cells
Oligodendrocytes work in CNS and each one is capable of myelinating a number of axons
Schwann cells work in PNS and each on meylinates only one axon segment
67
What is a microglial cell
Performs immune function in CNS
68
What is ependymal cell
Epithelial cells that line the fluid filled ventricles regulating the production and movement of csf
69
What are the relative conc of sodium potassium chloride and calcium ions extra cellular vs intracellular
Higher Na+/Cl-/Ca2+ extracellulary
| Higher K+ intracellularly
70
What is function of the sarcoplasmic reticulum and what effect does it have
Ca2+ storage › Ca2+ release following sarcolemma depolarisation
Ca2+ > myofibril contraction & muscle contraction
71
What is Myasthenia Gravis and what does it cause?
Autoimmune disorder: antibodies directed against ACh receptor
Causes fatigable weakness (becomes more pronounced with repetitive use)
72
What does the Goldman Hodgkin Katz equation calculate
The membrane potential of the cell if the following is known
- concentration of ion in cell
- concentration of ion outside of cell
- permeability of membrane to that ion at any one point, to those concentrations
73
What is an absolute refractory period
Period where inactivation gate of VGSC is closed and so a new action potential cannot be triggered
74
What is the relative refractory period
Period of time where you need a stronger than normal stimulus to trigger another action potential
Due to hyperpolarisation, more of a depolarisation is required to reach threshold and then cause another action potential
75
How is an action potential an example of positive feedback
Once the depolarisation occurs so that it is above the threshold potential, VGSC open
Increasing permeability which causes an influx of Na+
This causes more depolarisation repeating the cycle of opening VGSC to increase Na+
76
What does the propagation distnace and velocity of the AP along the axon depend on
Myelin thickness - Linear relationship between conduction velocity and myelin thickness
Diameter of axon - Larger diameter, faster travelling of action potential due to less resistance (conduction velocity proportional to square root of axon diameter)
77
What are the four main classes if proteins that drugs usually target
Receptors
Enzymes
Ion channels
Transport proteins
78
How can you determine the most safe drug based on the dosage of the drug
The safest drugs are those where there is a large difference between the dose required to induce the desired effct and teh dise required to induce side effcts/adverse effects
79
Which kind of effect increases as dosage of a drug increases
Off target effects
80
As the dose increases , what is the effect on the selectivity of that drug
Decreases
81
What class of protein does atorvostatin act on
Enzyme - HMG CoA reductase
82
What class of protein does citalopram act on
Transport protein - serotonin re uptake protein
83
What class of protein does salbutamol act on
Receptor - beta 2 adrenergic receptor in lung
84
What class of protein does Amlodipine act on
Ion channel - calcium channel
85
What is an adverse effect
A side effect has negative health consequences
86
What is the best defintion of pharmacology
A chemical substance that interacts with a specific target within a biological system to produce a physiological effect
87
List the 4 characteristics of synaptic transmission
Rapid timescale
Diversity
Plasticity
Learning and memory
88
What are the 3 steps that occur when a dendrite of one neurone receives an electrical impulse from another neurone
Information RECEPTION at dendrites
Information INTEGRATION at the soma
Information’s RAPID TRANSFER (action potential) - impulse is passed along the axon towards the synaptic terminals
89
Where is glycine most active and is it excitatory or inhibitory
Spinal chord and brainstem
| Inhibitory
90
What 2 things does neurotransmitter release require
Calcium influx
| Rapid transdcution
91
What type of proteins on the vesicle and presynaptic membrane enable fusion and exocytosis
Snare proteins (vesicular proteins)
92
What are vesicular proteins targets for
Neurotoxins
93
What do Zn2+ dependent endopeptidases do
Inhibits transmitter release
94
What does tetanus toxin cause and what bacteria produces it
Causes spasms and paralysis as it inhibits GABA and glycine (both inhibitory in CNS)
Made by clostridium tetani
95
What type of responses do ion channel linked receptors mediate
All fast excitatory and inhibitory transmission
96
What type of responses do G protein coupled receptors mediate
Slower transmissions than ion channel linked receptors
97
Give examples of responses where ion channel linked receptors are used
CNS - glutamate and gaba
| NMJ - Ach at nicotinic receptors
98
Give examples of responses where G protein coupled receptors are used
CNS
PNS
- Ach at muscarinic receptors, dopamine, noradrenaline, serotonin and neuropeptidez
99
What does an EEG (electroencephalography) measure
Elcetrical activity in the brain
100
What happpens when glutamate is in glial cells
Glutamate is enzymatically modified by glutamine synthetase to glutamine, which can then be pumped back to the pre synaptic terminal
101
What can abnormal cell firing associated with excess glutamate lead to
Seizures
| Spikes on EEG
102
Which drugs facilitate GABA transmission
```
Barbiturates
Benzodiazepines
Steroids
Convulsants
Zn 2+
Ethanol
```
Acronym (BBC SEZn)
103
What properties do drugs facilitating GABA transmission have
Antiepileptic
Anxiolytic
Sedative
Muscle relaxant
104
What effect does the PNS and SNS have on the liver
PNS - increased bile release
| SNS - increased glucose release
105
Which of the PNS and SNS controls the majority of the blood vessels
SNS
106
Where is the autonomic sensory (afferent) information relayed to
Hypothalamus
107
If there is high blood pressure, how is this information relayed to the relevant visceral motors and which of the PNS and SNS are switched on
Visceral sensory ~ baroreceptors detect increase in pressure
Signal sent to the PNS to be sent to CNS
Signal sent from CNS to PNS to visceral motors
Parasympathetic nervous system switched on to reduce blood flow
Sympathetic nervous system switched off to prevent further increase in blood flow
108
Where do the visceral motor nuclei originate
Hypothalamus
109
What do autonomic neurons generally consist of
Two neurons - pre ganglionic and post ganglionic fibres
| Ganglion - nerve cell cluster or group of nerve cell bodies
110
In PNS/SNS is pre ganglionic nerve fibre shorter or longer than the post ganglionic fibres
PNS - longer
| SNS - shorter
111
What is the difference between somatic and visceral nerves
Somatic nerves - innvervate skeletal muscles
| Visceral nerves - innervate trunk organs, vessels and glands
112
What is disinhibition
Tissues are innovated by both arms of the autonomic nervous system (parasympathetic and sympathetic) but at any given time one arm is dominant
113
What is the micturition reflex
1. PRESSURE BUILDS UP IN THE BLADDER
2. AS THE BLADDER FILLS > MORE IMPULSES
RECEIVED
3. THRESHOLD RECEIVE AND THE BODY MUST NOW
DO SOMETHING
4. PARASYMPATHETIC SWITCHES ON
SYMPATHETIC RELAXES
5. DETRUSOR CONTRACTS
6. INTERNAL SPHINCTER RELAXES
114
What structures does the limbic lobe include
Amygdala
Hippocampus
Mamillary body
Cingulate gyrus
115
What is the main function of the mamillary body
Recollective memory
116
What is the main function of the cingulate gyrus
Processing emotions and behaviour regulation
117
What functions is the limbic lobe concerned with
Learning, memory, motivation, emotions, reward
118
Where can you find the insular cortex
Deep inside the lateral fissure
119
What function is the insular cortex concerned with
```
Visceral sensation
Autonomic control
Interoception
Auditory processing
Visual-vestibular integration
```
120
Difference between dura mater in brain and dura mater in soinal chord
In spinal chord, it only has meningeal layer
121
Where is CSF produced
The choroid plexus of the lateral, 3rd and 4th ventricles
122
Where does CSF occupy
The ventricular system and the subarachnoid space
123
Where is CSF reabsored
Via Arachnoid villi into the superior sagittal sinus
124
What are the functions of CSF
Protection of CNS/brain
Mechanical support for CNS/brain
Transport of nutrients and biochemical products
125
Differences between plasma and CSF
CSF has lower pH, lower conc of glucose/protein/potassium than plasma
But same conc of sodium
126
In the spinal chord which of the dorsal and ventral rootlets are sensory and motor
Dorsal rootlets: afferent (towards CNS), sensory
| Ventral rootlets: efferent, motor
127
What are the 12 spinal nerves
```
Cervical - 8 (8 letters in cervical)
Thoracic - 12
Lumbar - 5
Sacral - 5
(5 letters in lumbar and sacral)
Coccygeal -1
```
128
What is the penumonic for afferent and efferent spinal neve
```
SAME DAVE
sensory afferent
motor efferent
dorsal afferent
ventral efferent
```
129
What donspinal nerves emerge through
Intervertebral formamina
130
What is cauda equina
Space at bottom of spinal chord where nerves are clumped together
Due to discrepancy in length between spinal chord and spinal column
Aneasthetics/analgesics can be inserted with a needle here, or a needle can be inserted to remove CSF from the area
131
What separates the frontal and parietal lobes
The central sulcus
132
Where is the primary motor cortex found
In the pre central gyrus
133
Where are the upper and lower moror neurons of the corticospinal tract found
Upper: primary motor cotex (in pre central gurus)
Lower: brainstem and spinal chord
- upper motor neurons synapse onto lower motor neurons in the brain stem if giung to muscles of head and neck, and onto lower motor neurons in the spinal chord if going to muscles below the neck
134
Which part of the spinothalamic tract take info about crude touch and which part about pain and temperature
Ventral spinothalamic tract: crude touch
| Lateral spinothalamic tract: temp and pain
135
Describe spinal chord internal anatomy
Descending pathways (motor)
Dorsal corticospinal tract - motor
Ventral corticospinal tract - motor
Ascending pathways (sensory)
Dorsal column - vibration, fine touch, proprioception
Lateral spinothalamic tract - pain and temp
Ventral spinothalamic tract - crude touch
136
Where do the third order neurones of the spinothalamic and dorsal tracts project to and from
Project from thalamus to somatosensory cortex in the post central gyrus
137
What is a hemisection of the spinal cord
Injury leading to incomplete spinal cord lesion
138
What are strange sensations and jerking movments of arm after a stroke a sign of?
And what is likely to happen if the consition is left untreated?
Active epileptic focus formed as a result of tissue damage from the stroke
Jerks are caused by propagation of discharge to arm area in primary motor cortex in frontal lobe
If left untreated, Seizures may spread across whole motor cortex or even propagate to otehr hemispheres and produce generalised seizures
Recurring seizures may also contribute to neuronal injury
139
What is a dermatome
An area of skin supplied by a single spinal nerve
140
What is a myotome
A group of muscles that is innervated by a single spinal nerve
141
What do the sympathetic and parasympathetic innervate
Sympathetic innervates the viscera and the periphery (vasculature and sweat glands)
Parasympathetic innervates the viscera only
142
What is the difference between a ganglion and nucleus
Ganglion is a collection of cell bodies outside the CNS
| Nucleus is a collection of cell bodies in the CNS
143
What is a plexus
A network of interconnecting nerves
144
Where do the visceral efferent nerves synapse
In peripheral ganglion
145
Where do somatic and visceral afferent fibres have their cell bodies
Both have their cell bodies in spinal ganglia - (dorsal root ganglion)
146
How are peripheral nerves arranged and covered
The peripheral nerves are arranged into bundles called fasciculi
1) Endoneurium (contains myelin sheath) covers the individual axons
2) Perineurium covers each of the fasciculs
3) Epineurium is the external vascular layer whihc covers the bundle of fasciculus
147
What are the two classification systems of peripheral nerves
1) using conduction velocity: A, B, C —> A is the fastest
2) using axonal diameter: roman numerals, I, II, III, IV….. —> I is the largest
(AXONAL DIAMETER CLASSIFICATION IS ONLY USED FOR SENSORY NEURONES)
148
How can the different sensory receptors be classified
1) source of stimulus
External: Exteroceptors
Internal: Enteroceptors, Proprioceptors
2) method of detection
- Chemoreceptors, Photoreceptors, Thermoreceptors, Mechanoreceptors, Nocicoreceptors
149
Describe what Exterorecptors detect
Pain
Touch
Temperature
Pressure
150
What do enteroceptors detect
Movement through gut
| Blood pH
151
What do proprioceptors detect
Movement
| Joint position
152
What do Nocicoreceptors detect
Pain due to tissue damage
153
What are the 3 main types of proprioceptors
1) muscle spindles - detect changes in length of muscles
2) Golgi tendon organs - detect changes in the tension of tendos
3) Joint receptors - found in joint capsules, detect start and wnd of movement
154
What is a motor unit
A simgle motor neurone along with all the muscle fibres it innervates
155
What does stimulation of one motor unit cause
Contraction of all the muscle fibres in the motor unit
156
Can 2 motor neurones innervate the same muscle fibre
No
157
What neurotransmitters are released at the pre and post ganglionic neurones in the autonomic nervous system
Pre ganglionic : Ach
Post ganglionic : Ach (parasympathetic), Noradrenaline (sympathetic) —> except for in sweat glands and blood vessels where Ach is released for sympathetic
158
What is a monosynaptic reflex
Reflex involving only one synapse between the sensory and motor neurone
159
Describe sympathetic and parasympatheic outflow from the CNS
Sympathetic: thoracolumbar outflow - from T1 to L2
Parasympathetic: craniosacral outflow - brainstem cranial nerves 3,7,9,10 and spinal sacral segments S2 to S4
160
What information does the visceral sensory neurone relay to the CNS
Pain, fullness, blood pressure
161
Which cranioa nerves do the vosceral sensory neurones run to
9: glossopharyngeal
10: vagus
162
Sympathetic effect on kidneys
Stimulates epinephrin and norepinephrin release
163
Sympathetic effect on liver
Stimulates glucose release
164
Parasympathetic effect on liver
Stimulates bile
165
What do the sympathetic nerves do when they leave the spinal column
They enter the sympathetic trunk and synapse at ganglia there
166
What are white and grey ramus communicans
White ramus communicans: myelinated pre ganglionic neurones
| Grey ramus communicans: unmeylinated post ganglionic neurones
167
How is sympathetic outflow to the heart different from sympathetic outflow to other viscera
To heart: sympathetic nerves emerge from spinal cord T1-T4 and synapse in ganglia of the sympathetic trunk. They then enter cardiac plexus and innnervate heart
To rest of viscera: sympathetic nerves do not sympase in the sympathetic trunk. Instead they travel straight through it and synapse on ganglia which lie on the aorta “pre aortic ganglia”
168
Describe the anatomy of the parasympathetic outflow to the viscera
Craniosacral outflow
```
Cranial ouflow:
CN3: lacrimal ducts
CN7: pupil constriction, salivary glands
CN9: parotid gland
CN10: heart, gut
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Sacral outflow:
S2-S4: gut, erectile tissue of pelvic region/penis
169
What are the 2 main arterial blood supplies to the brain
Anterior blood supply: intervertebral - supplies most of cerebral hemispheres
Posterior blood supply: vertebrobasilar: supplies brainstem
170
What do SSA nerves do
Special somatic afferent
| Carry sensation of hearing and balance
171
What do SVA nerves do
Special visceral afferent
| Carry taste sensations
172
What do SVE nerves do
Special visceral efferent
| Innervate skeletal msuxles of the jaw, face, larynx and pharynx
