Neuroscience and Mental Health Flashcards
1
Q
What are the general features of neurones?
A
- Large nucleus
- Prominent nucleolus
- abundant rER
- well developed Gogli
- abundant mitochondria
- highly organised cytoskeleton
2
Q
What neuronal structure is used to receive information?
A
Dendrites (mainly spines that cover the dendrites)
3
Q
What is the most plastic part of the nervous system?
A
Dendritic spines
4
Q
What neuronal structure is used to output information?
A
Axon, which branch to form axon collaterals
5
Q
What structure does the axon emerge from?
A
Axon hillock
6
Q
What are the structural properties of axons, and why?
A
They can maintain high tensile strength. This is because they have prominent micro-tubules and neurofilaments to maintain axon diameter.
7
Q
How are the nodes of Ranvier specialised?
A
They have tight junctions and paranode areas
8
Q
What is formed by extensive branching of an axon close to a target?
A
Terminal arbor
9
Q
What are the two types of synapses?
A
Boutons and Varicosities
10
Q
Why is the brain highly sensitive to O2 deprivation?
A
A lot of energy is needed for ion pumping and synaptic transmission.
11
Q
What is the process by which neurones process inhibitory and excitatory inputs?
A
Neuronal integration
12
Q
What synapses are associated with excitatory, inhibitory and modulatory function?
A
Excitatory = Axon-Dendrite Inhibitory = Axon-somatic Modulatory = Axo-axonic
13
Q
How is protein movement in the axon ensured to move in just one direction?
A
The microtubules are polarised. Retrograde transport organelles are biochemically distinct.
14
Q
What are the morphological subtypes of neurones?
A
- Pseudounipolar
- Bipolar (majority)
- Golgi Type I multipolar (long axons)
- Golgi Type II multipolar (short axons)
15
Q
Give examples of Golgi T1 and T2 neurones
A
T1: Pyramidal cells of the cerebral cortex Purkinje cells of the cerebellum Anterior horn cells of the spinal chord T2: Stellate cells of the cerebral cerebellum
16
Q
What are the different types of neuroglia?
A
- Astroglia
- Microglia
- Oligodendroglia
- Schwann Cells
- Immature progenitors
- Ependymal cells
- Satellite glia
17
Q
What is the most abundant neuroglia?
A
Astroglia
18
Q
What are the functions of astroglia?
A
- scaffolding for neuronal migration and axon growth during development
- formation of blood-brain barrier
- synthesis of neurotrophic factors
- transport of substances from blood to neurones
- removal of neurotransmitters
- segregation of synopsis
- potassium ion buffering
- glial scar formation
19
Q
What are the properties of astroglia?
A
Most numerous cell type
Many processes
Numerous intermediate filament bundles in cytoplasm
20
Q
What is the structure and function if oligodendroglia?
A
Oligodendroglia are myelin forming cells of the CNS. They have a prominent ER and Gogli as they are metabolically active. Each cell produces multiple sheath.
21
Q
What diseases are caused by loss of myelin?
A
Multiple Sclerosis
Adrenoleukodystrophy
22
Q
What are the functions of microglia?
A
They present antigens to invading immune cells. They are the first cells to react to an infection or damage. They have a role in tissue modelling and synaptic stripping. If they detect enough damage, they turn into phagocytes.
23
Q
How are Schwann cells different to Oligodendrocytes?
A
Schwann cells are in the PNS. They only produce one myelin sheath segment. They can slo promote axon regeneration.
24
Q
How can the nervous system be decided structurally?
A
- Central Nervous System = Spinal chord and brain
- Peripheral Nervous System = Nerves and ganglia outside the CNS
25
How can the PNS be further functionally divided?
- Autonomic nervous system = regulates function of viscera
| - Somatic nervous system = controls motor and sensory functions
26
How can the Somatic nervous system be further divided?
Parasympathetic and Sympathetic nervous systems.
27
What are the different types of neurones in the spinal chord, based on their direction of transmission?
Afferent axons propagate action potentials towards the CNS
Efferent axons propagate action potential from the CNS
Interneurones are CNS neurones that synapse with other CNS neurones within the spinal chord.
28
What are the different lobes of the brain?
Frontal, Parietal, Temporal, Occipital, and ?Cerebellum?.
29
What is meant by the contralateral nature of the cerebral cortex?
The two hemispheres receive sensory information and control movement for the opposite sides.
30
What is the main function of the cerebellum?
Co-ordination of movement
31
What is the main function of the brain stem?
Regulates vital functions such as breathing
32
Are the dorsal and ventral roots part of the CNS or PNS?
PNS
33
Where are the dorsal and ventral roots located?
```
Dorsal = posterior
Ventral = anterior
```
Emerging from the spinal chord, by a collection of rootlets
34
How to sensory and motor neurones leave/enter the spinal chord?
Sensory nerves enter through the dorsal roots.
| Motor nerves exit through the ventral roots.
35
What does a spinal nerve consist of?
They contain axons wrapped around endoneurium. Multiple of these units are bundled with blood vessels, and surrounded with perineurium to form a fascicle.
36
What are the regeneration properties of the CNS and PNS?
PNS nerves can regenerate. CNS nerves are unable to regenerate over long enough distances to be useful.
37
What are the problems with PNS nerve regeneration?
- Non-specific target reinnervation
| - Abberant axon sprouting
38
Where are the cell bodies of the PNS neurones?
Sensory neurones have cell bodies in dorsal root ganglia.
Somatic motor neuroes have the cell bodies in the grey matter of the spinal chord.
Autonomic motor neurones have their cell bodies in the grey matter as well, but also have ganglia.
39
What is the white matter of the spinal chord?
Ascending and descending axon tracts to and from the brain.
40
How can a fast reflex response be carried out? How is this consciously registered?
Somatic sensory neurone inputs to an interneurone, which inputs to a motor neurone directly. Conscious registering happens where the sensory inputs activate further sensory neurones in the spinal chord grey matter, transmitting action potential to the sensorimotor cortex
41
Why do cells set an electric potential?
- Transmit information over long distances
| - Control the entry of calcium into cell
42
What is flux?
The number of molecules that cross a unit area per unit time
43
What is voltage?
Current X Resistance. 'Potential' producing a charge gradient.
44
What is current?
Movement of ions due to potential
45
What is resistance?
A barrier that prevents the movements of ions
46
Give examples of resting membrane potentials
Neurones have a resting membrane potential of -70mV. Hepatocytes have a resting membrane potential of -10mV.
47
What property of membranes allows resting membrane potentials to exist?
Selective permeability.
48
What are the two types of ion channels?
Voltage-dependent and Voltage-independent.
49
What does the Nerst Equation predict?
The equilibrium potential of an ion x
50
When measuring gradients across a membrane, what does a positive value show?
A tendency for the molecule to move towards the cell.
51
What equation takes into account the equilibrium potentials of all the ions?
The Goldman-Hodgkin-Katz voltage equation.
52
How does the amplitude of a action potential compare to a generator potential?
Action potential has uniform amplitude, generator potentials are relative to stimulus size, and can be bi-directional.
53
Where can graded potentials occur?
At synapses or sensory receptors
54
What type of ion channels facilitate resting and action potentials?
Resting potential is facilitated by voltage-independent ion channels. Action potentials by voltage-dependent.
55
How do voltage-dependent ion channels become opened, closed and inactivated?
Opened by depolarisation. Closed by hyperpolarisation. Inactivated by sustained depolarisation.
56
In an action potential, describe the resting state.
The resting membrane potential is at -70mV as Pk>Pna and so the membrane potential is closer to the equilibrium for K+. Voltage-gated ion channels are closed.
57
In an action potential, describe the depolarising stimulus.
The stimulus depolarises the membrane potential as sodium ions enter the neurones. This moves it in the positive direction towards the threshold (-55mV)
58
In an action potential, describe the upstroke.
Pna is greatly increased due to voltage-gated Na+ channels opening. Na+ enters the cell down the electrochemical gradient.
Pk is increased slightly, as K+ voltage-gated ion channels open. Some K+ leave the cell.
Membrane potential moves towards the Na+ equilibrium potential.
As the upstroke progresses, more and more voltage-gated K+ channels open/
59
In an action potential, describe repolarisation.
The permeability of Na is greatly reduced as Na+ channels inactivate. Pk continues to increase as voltage-gated K+ channels open and remain open, allowing more K+ to leave the cell.
This allows the membrane potential to return towards the K+ equilibrium potential.
As this refractory period continues, the voltage-gated Na+ channels close.
60
In an action potential, describe hyperpolarisation.
At rest, voltage K+ channels are still open, allowing K+ to leave for a few milliseconds before they close.
The Na+ channel is activated (but still closed) - a larger stimulus may start another AP.
61
What is a threshold potential?
A potential that once reached, an AP is triggered.
62
Compare the two types of refractory states.
Relative refractory period is where the Na+ channels are not inactivated, but closed, allowing a stronger stimulus to trigger an AP.
Absolute refractory period is where the Na+ channels are inactivated, nothing can trigger an AP.
63
Why does the AP only travel in one direction?
Because the other direction is still in a refractory period.
64
What is the speed difference in a myelinated versus non-myelinated neurone?
```
Myelinated = 120 m/s
Non-myelinated = 1 m/s
```
65
What factors affect conduction speed in an axon?
- Myelination
| - Diameter (wider = faster)
66
What are molecular motors?
Protein assemblies that convert chemical energy into mechanical energy
67
Where is energy for molecular motors derived?
ATP or ionic gradient
68
What are the types of molecular motors? Give examples for each
Linear motors - require protein rails e.g myosin.
Rotary motors - require stators e.g flagellar motor
Oscillary motors - require cross-linked microtubule bundles called axonemes e.g dynein in cilia.
69
What molecular motor runs on actin?
Mysoin
70
In what direction does myosin travel?
Positive (towards plasma membrane)
71
What molecular motors run on microtubules?
Kinesin and Dynein
72
In what direction do Kinesin and Dynein travel?
Kinesin in postive direction, Dynein in negative direction (towards nucleus)
73
How are microtubules assembled?
Polymerisation of alpha and beta tubular in the presence of microtubule-associated proteins and taxol. Assembled radially, originating from microtubule organising centers.
74
What is the diameter and lumen diameter of a microtubule?
```
Diameter = 25nm
Lumen = 14 nm
```
75
Why don't microtubules reach the plasma membrane?
Rich mesh of actin stops it.
76
How are actin filaments made?
Polymerisation of G-actin to make F-actin
77
Give examples of actin filaments
Thin filaments of the muscle
| Core of each microvillus
78
Describe the properties of F-actin
Dual stranded helix of actin monomers. Have a symmetry of 13/6. The filament is polar. The actin filaments on one side are oppositely charged to the other.
79
What is a thin filament composed of?
F-actin with tropomyosin and troponin
80
Describe the properties of Myosins
Made by two amino acid chains. Two light chains make the heads. A heavy chain forms the coiled coil caused by two long tails coiling.
They have a large globular head which binds and splits ATP to undergo conformational change.
81
What are the types of myosin?
17 classes.
| Myosin II is found in muscle. Myosin V found in brain involved in vesicular transport.
82
Describe the properties of Kinesin
Two amino acid chains, each terminating in a globular ATP finding head. The tails of the proteins from a coiled-coil with each other. It moves progressively (does not loose contact with microtubule)
83
How does dynein compare with kinesin and myosin?
Dynein is the largest of three motors and has evolved separately from myosin and kinesin
84
Describe the properties of Kinesin
Has a head from by an AAA ring. A stalk that binds to the microtubule and changes position. Has a stem that holds the cargo.
85
What is a muscle made of?
A muscle contains a few muscle fascicles. They contain many muscle fibres/myofibres/cells. The cells contain many myofibrils. The myofibrils contain many sarcomeres.
86
What are the properties of myofibres?
- Covered by the sarcolemma
- Contains sarcoplasm
- Contains many myofibrils
- Many mitochindira
- Has myoglobin
- Has sarcoplasmic reticulum
87
What is a thick filament made of?
Hundreds of myosin molecules.
88
What are the different zones/bands/lines of the sarcomere.
```
Z line encloses sarcomere
H Zone is thick filament only
A band is thin filament span
M line is middle
I band is thin filament only
```
89
What areas of the sarcomere shorten upon contraction?
I band and H zone
90
What neurotransmitter is used to initiate muscle contraction?
Acetylcholine
91
How is muscle contraction initiated by an AP?
1) AP propagates along T-tubule
2) DHP changes conformation and touches RyR.
3) RyR opens allowing Ca2+ to leave sarcoplasmic reticulum
4) Ca2+ binds to troponin causing tropomyosin to move
5) Cross-bridges form
6) Ca2+ actively transported into SR continuously while AP continues.
92
Describe the sliding filament theory
1) The binding of calcium ions causes troponin to change shape, and this tropomyosin to move, exposing the myosin binding site on actin
2) Charged myosin heads (with ADP) binds to exposed site on actin filament
3) This causes the discharge of ADP, and the myosin head to pivot (power stroke), pulling the actin filament towards the centre of the sarcomere
4) ATP binds to myosin, releasing the myosin head from the actin chain
6) ATP hydrolysis charges the myosin head to a cocked position.
93
How does muscle relaxation occur?
AP stops. Ca2+ is sequestered back into sarcoplasmic reticulum. For every 2 Ca2+ transported, one ATP is used.
94
How is muscle force varied?
1) Recruitment of motor units
2) Increasing frequency of AP will cause fused tetanus force
3) Optimum sarcomere length
4) Depends on velocity. The greater the velocity, the lower the force (related to number of crosslinks formed)
95
What is a motor unit?
One motor neurone and all the muscle fibres it innervates.
96
What are the types of muscle contraction?
Isometric: force without a change in muscle length
Isotonic: contant force with a change in length. Concentric = shortening. Eccentric = lengthening
Isovelocity: force with constant velocity of shortening of lengthening.
97
What is ATP in muscles needed for?
1) Changing myosin head
| 2) Active transport of Ca2+ into sarcoplasmic reticulum
98
How is ATP regenerated immediately, in the short term, and in the long term after muscle contraction?
- Immediately using creatine kinase and phosphocreatine.
- Short term using glycolysis
- Long term using oxidation
99
What are the properties of intercalated disks in cardiomyocytes?
Gap junctions allow ionic current to flow between fibres.
100
Why can't cardiomyocytes produce a tetanus force?
Their action potentials are very long and have a large refractory period.
101
How does the cardiac muscle differ from skeletal muscle in terms of contraction?
Cardiomyocytes use extracellular Ca2+ as well as intracellular stores.
102
How is the contractile mechanism of smooth muscle different to other muscle?
It does not involve troponin.
103
What is an EMG?
Electron Micrograph : the recording of the action potential occurring in skeletal muscle fibres
104
How is the EMG value recorded?
An extracellular recording that measures the emf potential between two extracellular locations.
105
Give two examples of EMG related measures
EKG or ECG (electrocardiogram) records action potentials from the heart
EEG (electroencephalogram) records the action potential from the brain
106
Why does an EMG work?
The body and skin are good conductors of electricity
107
What are the properties of neurotransmission?
- Rapid
- Diverse
- Adaptability
- Plasticity
- Learning and memory
108
How big is a synapse?
20-100nm
109
What are the different types of neurotransmitters?
- Amino acids (e.g glutamate, GABA, glycine)
- Amines (e.g noradrenaline, dopamine)
- Neuropeptides (e.g opioid peptides)
110
How much calcium is needed to cause neurotransmitter release?
200uM
111
Why does neurotransmission occur so rapidly?
The vesicles are primed and docked in the synaptic zone, read for release.
112
How does intracellular calcium cause vesicle release?
Ca2+ entry activates Ca2+ sensor in the protein complex where the vesicle is docked, prompting the vesicle to fuse with the membrane.
113
Give examples of neurotoxins
Tetanus toxin causes paralysis
Botulinum causes flacid paralysis
alpha-latrotoxin from the black widow spider stimulates neurotransmitter release to depletion
114
Give examples of excitatory and inhibitory neurotransmitters and how they work
Glutamate is an excitatory neurotransmitter. It works by causing an influx of Na+ into the cell.
GABA (Gamma amino butyric acid) receptors are inhibitory allowing Cl- into the cell, further polarising the cell.
115
Describe the two types of Glutamate receptors
- AMPA are fast excitatory receptors
- NMDA receptors mediate slow excitatory transmission. It needs previous depolarisation. It is the basis of associative memory
116
How do glial cells remove glutamate?
Glutamine synthetase converts glutamate into glutamine
117
What causes epilepsy?
A decrease in GABA-mediated inhibition, or increase in glutamate-mediated excitation.
118
Why does GABA have a stronger inhibitory effect?
GABA receptors are in the soma of the cell.
119
How do glial cells remove GABA?
Trans-aminase enzyme converts GABA into succinate semialdehyde, which can enter the TCA cycle.
120
Give examples of four anti-epileptic drugs, and how they work
- Valproate has a weak effect on GABA transaminase and Na+ channels
- Phenobarbital enhances GABA action and inhibits synaptic excitation
- Benzodiazepines enhance GABA action
- Vigabatrin inhibits GABA transaminase
121
What makes up the forebrain, midbrain and hindbrain?
Forebrain: Cerebral hemispheres and Diencephalon
Midbrain
Hindbrain: Pons, Medulla and Cerebellum
122
What makes up the brainstem in descending order?
Midbrain, Pons and Medulla
123
What are the folds and crevices of the cerebral cortex called?
Gyri and Sulci
124
What are the different types of cortical areas?
- Primary cortical areas (small, known functions)
| - Association cortical areas (higher functions, areas can be grouped)
125
List the known primary and association cortical areas
- Broca's area
- Primary motor cortex
- Somatosensory cortex
- Primary visual cortex
- Wernicle's area
- Primary auditory cortex
126
What are the different areas of the ventricular system in the brain?
- Lateral ventricles
- Third ventricle
- Aqueduct
- Fourth ventricle
- Central canal
127
Where are the structures of the ventricular system located?
Lateral ventricles are in the cerebral hemispheres. The third ventricle is in the diencephalon. The aqueduct passes through the midbrain.
128
What is the function of the ventricular system?
Mechanical and metabolic.
129
What is the main function of the diencephalon?
Thalamus: A relay section between the cerebellum and hypothalamus.
Hypothalamus: Important for homeostasis
130
Where are the basal ganglia, what are their functions?
Basal ganglia control pattern of movement in concert with the motor cortex. Found on the inside of the cerebral cortex.
131
What is the main function of the brain stem?
Control vital functions. Cranial nerves are also attached to the brainstem.
132
What is contained within the ventricular system?
Cerebrospinal fluid produced by choroid plexus cells in the ventricles.
133
How does CSF differ from blood?
Less cells, proteins, K+ and C+. Higher [Ca] and [Mg].
134
How does CSF circulate around the brain?
Holes in the ventricular system allow the fluid to surround the brain in the subarachnoid spaces. It is absorbed into the venous sinuses of the arachnoid villi.
135
What is the normal CSF volume and flow rate?
150ml and 500ml/day
136
What are the membranes/layers between bone and brain in descending order?
Bone > Dura mater > Arachnoid mater > Subarachnoid space > Pia mater
137
How can the spinal nerves be categorised?
Cervical, Thoracic, Lumbar and Sacral
138
Where can a lumbar puncture be performed?
Lumbar cistern between L3 and L4 vertebrae.
139
What is hydrocephalous?
A buildup of CSF around the brain.
140
What are the consequences of hydrocephalous?
Pressure of CSF causes compression of brain blood vessels leading to neuronal and cognitive damage.
141
What are the two types of hydrocephalous?
Communicating (CSF flow) and Non-communicating (blockage)
142
What are the different types of cerebral haemorrhage? How can they be distinguished?
Epidural (extradural) haemorrhage is caused by a damaged artery between the skull and dura mater.
Subdural haemorrhage is caused by a damaged vein between the dura and arachnid mater.
Epidural is caused by artery damage, and so hypoxia symptoms surface much faster.
143
What are the consequences of cerebral haemorrhage?
haemorrhage can cause space-pccuoying lesion and hence neurological deficits.
144
Where does myelination happen in the PNS?
Myelination happens in neurones above a certain diameter. Unmyelinated axons are also surrounded by the cell membrane of Schwann cells, but only have a single layer.
145
What spinal nerves carry somatic neurones?
All
146
What spinal nerves carry autonomic neurones (divide by parasympathetic and sympathetic)
Sympathetic: T1-L2
Parasympathetic: (cranial) + S2-S4
147
What type of nerves go through the ventral and dorsal roots?
Ventral: motor
Dorsal: sensory
148
What are the names of the innervation patterns formed by somatic nerved to muscle and skin?
Myotome and dermatome
149
Why are some dermatomes not innervated in a logical pattern? Give an example of one such area.
Some spinal nerves combine to form peripheral nerves in a plexus. An example is the C5-T1 spinal nerves contribute to the brachial plexus.
150
How can a clinician deduce the region of somatic sensory nerve damage?
Plotting the area of sensation to see if it conforms to an area responsible by a spinal or peripheral nerve.
151
How does a nerve regenerate after a pressure injury?
The distal part of the nerve degenerates and is cleared up by macrophages.
Axonal sprouts will compete to see which one can get to the target neurone quickest. The winner becomes the bigger axon, the other sprouts regress.
152
How can you tell a nerve that has regenerated?
The distance between node's of Ranvier are shorter.
153
How are peripheral neuropathies diagnosed?
Nerve biopsy or conduction velocity tests.
154
What are the sympathetic and parasympathetic actions on the: Eyes, Trachea and Bronchioles, Liver, and Kidneys?
Eyes: S - contract radial muscle. P - contract pupillary sphincter and cillary muscle.
Trachea and Bronchioles: S - dilate. P - constrict
Liver: S - increased glycogenolysis and gluconeogenesis
Kidneys: S - increased renin secretion
155
What are the sympathetic and parasympathetic actions on: Adipose tissue, Ureters and Bladder, Salivary glands, and Skin?
Adipose: S - lipolysis
Ureters and Bladder: S - relax detrusor, constrict trigone and sphincter. P - contracts detrusor, relaxes trigone and sphincter.
Salivary glands: S - thick, viscous secretion. P - copious, watery secretion.
Skin: S - piloerection and increased sweating.
156
What are the sympathetic and parasympathetic actions on the Heart, GI tract and Blood vessels?
Heart: S - increased heart rate and strength of contraction. P - lower heart rate and contractility.
GI : S - decreased motility and tone, sphincter contraction. P - increased motility and tone and secretion.
Blood vessels: S - dilation on skeletal muscle and constriction in general.
157
How does the sympathetic system affect the smooth muscles in the trachea and bronchioles?
The smooth muscles are not sympathetically innervated. They are activated by catecholamines.
158
What arm of the autonomic nervous system usually has dominance over the heart?
The parasympathetic nervous system.
159
What are the parasympathetic cranial nerves?
III - oculomotor
VII - facial
IX - glossopharyngeal
X - vagus
160
How long are the parasympathetic neurones?
Pre-ganglionic is very long. Post-ganglionic fibres are very short.
161
How long are the sympathetic neurones?
Pre-ganglionic is shorter than post-ganglionic
162
How is CO, MABP and TPR related?
CO is proportional to MABP/TPR
163
What determines Cardiac Output?
CO = HR x SV
164
How does the sympathetic nervous system increase MAPB?
1) Increasing CO by an ionotropic effect (increasing SV) and chronotropic effect (increasing HR)
2) Increasing TPR by constricting arteries, veins and arterioles.
165
How is vasodilation carried out?
- Decreased sympathetic tone
- Increased sympathetic activity in skeletal muscle
- local vasodilators
- Increased parasympathetic stimulation to some blood vessels such as pudendal in penis.
166
How is the bladder innervated?
- Parasympathetic control over detrussor muscle which surrounds bladder. Sympathetic control of internal sphincter. Somatic control over external sphincter.
167
What is the micturition reflex?
As pressure builds in the bladder, it relays information to the CNS via the parasympathetic pelvis nerve, which then contracts the detrusor muscle. Increased parasympathetic activity decreases sympathetic control over the internal sphincter, allowing urine to flow until the external sphincter.
168
What neurotransmitters are used by the autonomic nervous system?
Parasympathetic use acetylcholine
Pre-ganglionic sympathetic use acetylcholine. Post-ganglionic sympathetic is usually noradrenaline, but acetylcholine in the sweat glands.
169
What type of neurotransmitter receptors are found in the autonomic nervous system?
Parasympathetic: Nicotinic (ion channel, fast) and Muscarinic (G-protein, slower).
Sympathetic: Nicotinic, Adrenergic and Muscarinic.
170
How is acetylcholine synthesised?
Acteyl CoA + Choline -> ACh. By enzyme choline acetyl transferase.
171
How is acetylcholine metabolised?
ACh -> Choline + Acetate. By Acetylcholine esterase. Choline and acetate are reabsorbed by pre-synaptic neurone.
172
How is noradrenaline synthesised?
1) Tyrosine -> DOPA. By Tyrosine hydroxylase
2) DOPA -> Dopamine. By DOPA decarboxylase.
3) Dopamine -> Noradrenaline. By Dopamine (beta) hydroxylase.
173
How is noradrenaline metabolised?
1) Noradrenaline is removed by active transport, to the pre-synaptic neurone.
2) Noradrenaline is converted to metablotes in the mitochondria.
174
How is adrenaline synthesised?
It is produced in the adrenal medulla by Chromaffine cells, innervated by sympathetic pre-ganglionic fibres.
Noradrenaline -> Adrenaline by enzyme phenyl-N-methyl transferase. Cortisol increases production of this enzyme.
175
Where are the baroreceptors located?
In the carotid sinus and aortic arch.
176
How does the baroreceptor reflex respond to a drop in blood pressure?
Lower blood pressure decreases baroreceptor firing signals to the brain. This decreases inhibition of the sympathetic nervous system. This sees a rise in BP.
177
How does the light reflex work?
A large amount of light hits the back of the eye. The optic nerve takes this to the prelectal nucleus, which has a relay neurone to the Edinger-westphal nucleus, which has the terminal of the Occularmotor nerve. This signal eventually causes the pupil to constrict.
178
What is the consensual reflex?
If light shines on one eye, both pupils constrict.
179
How is the autonomic nervous system controlled centrally?
Higher brain centers + Homeostatic changes --> Hypothalamus --> Medulla --> Sympathetic and Parasympathetic
180
How doe the efferent nerves enter and leave the sympathetic trunk?
Enter the trunk stating at the spinal chord, traveling through the spinal nerve and entering the trunk through the white rams communicans.
Leaves through the grey ramus communicans.
181
What are the sympathetic plexi around the cervical level?
- around pharynx
- cardiac plexus
- thyroid plexus
- pulmonary plexus
182
What are the sympathetic plexi around the thoracic level?
- around the thoracic aorta
| - greater, lesser and least splanchnic neevrs.
183
Describe the carnival nerve III outflow
Occulamotor: cililary ganglion behind eye; post-ganglionic fibres to the sphincter pupillae and ciliary muscle.
184
Describe the carnival nerve VII outflow
Facial nerve:
- submandibular ganglion supplies post-ganglionic fibres to the submandibular and sublingual salivary glands
- pterygopalatine ganglion supplies postganglionic fibres to paranasal sinuses and lacrimal glands.
185
Describe the carnival nerve IX outflow
Glossopharyngeal nerve:
| Otic ganglion supplies ganglionic fibres to parotid gland.
186
Describe the carnival nerve X outflow
Vagus nerve:
| enters neck via carotid sheath, branches to lung, heart, oesophagus, stomach and intestines
187
What are the two plexi of the enteric system?
- Myenteric plexus supplies muscles of the gut
| - Submucous plexus supplies submucosal layer.
