14-30 Flashcards
(103 cards)
1
Q
What characteristics do amino acid and amine neurotransmitters have?
A
Small molecules, stored and released from synaptic vesicles, act on both G coupled protein receptors and ligand-gated channels
2
Q
What characteristics do peptide neurotransmitters have?
A
Large molecules, stored in secretory granules, only activate G coupled receptors.
3
Q
What was Dale’s principle
A
That one neuron has only one neurotransmitter specific to it
4
Q
Where does the synthesis of non-peptide neurotransmitters occur?
A
Synthesis is localised to the axon terminal by specific enzymes and stored in secretory vesicles (ACh, GABA, amines) Glycine and Glutamate are abundantly found in all cells.
5
Q
What major role does glutamate have and what receptors does it bind to?
A
Most common excitatory neurotransmitter in the CNS and binds to NMDA and AMPA receptors.
6
Q
What does the binding of glutamate to AMPA receptors cause.
A
Fast transmission as potassium and sodium ion transfer is evoked causing an EPSP to form
7
Q
Why does the binding of glutamate to NMDA receptors on its own not cause a change in potential?
A
Because there is a voltage dependent magnesium block on the receptor so it must first be indirectly activated by another transmitter.
8
Q
What is the major role of GABA in the brain?
A
Major inhibitory neurotransmitter
9
Q
How does GABA produce an IPSP
A
Through the activation of GABA gated chloride ion channels
10
Q
Where does GABA inhibition occur mainly
A
Found throughout the brain but especially in the cortex and striatum
11
Q
How does GABA (or Gly) release onto an excitatory synapse undergoing an action potential cause inhibition?
A
Causes the closure of calcium ion channels so less neurotransmitter is released by the excitatory synapse so less of an effect is seen on the target cell.
12
Q
What does too much or too little GABA cause
A
Too much = coma
Too little = seizures
13
Q
How do opiates act and where are they synthesised?
A
Act via the endogenous opiate system and are synthesised in the rough ER and are packaged into secretory granules`
14
Q
What will action of opiates on the spinal, amygdala and medulla receptors cause
A
Spine: loss of pain sensation
Amygdala: loss of ability to regulate emotional responses
Medulla: Depresses respiration and cough reflexes (may induce vomiting
15
Q
What are opiates mode of action?
A
Receptors are G coupled - act as modulators leading to downstream enzyme activity
16
Q
Negatives of opiates?
A
Become dependent, relieves dull visceral pain better than sharp pain
17
Q
What NT’s take part in the diffuse modulatory systems of the brain?
A
ACh, Serotonin, Catecholamines (dopamine, adrenaline noradrenaline)
18
Q
What is an active zone?
A
The actual sites of neurotransmitter release
19
Q
What is meant by quantal release of neurotransmitter?
A
The amount of neurotransmitter released from a single vesicle
20
Q
Agonist of ACh on nicotinic receptor?
A
Nicotine
21
Q
Antagonist of ACh on nicotinic receptor?
A
Curare
22
Q
Agonist of ACh on muscarinic receptor
A
muscarine
23
Q
Antagonist of ACh on muscarinic receptor
A
Atropine
24
Q
Agonis of norepinephrin on alpha receptor
A
Phenylephrine
25
Antagonist of Norepinephrine on alpha receptor
Phenoxybenzamine
26
Agonist of Norepinephrine on beta receptor
Isoproterenol
27
Antagonist of Norepinephrine on beta receptor
Propanolol
28
Where is ACh synthesised most?
By all motor neurons as it is used at all neuromuscular junctions
29
What specific enzyme is required for ACh synthesis
Choline acetyltransferase
30
Why is ChAT a good marker for cells that use ACh as a neurotransmitter?
Because it is only produced in cholinergic neurons, ChAT specific antibodies can be used to identify cholinergic neurons
31
What does ChAT do?
Transfers the acyl group for acetyl CoA to choline
32
Where is the source of choline in the production of ACh?
The extracellular fluid where it exists in low micro molar concentrations
33
What two ares of the brain can ACh be found?
Basal forebrain and the hippocampus
34
What enzyme breaks down ACh?
acetylcholinesterase
35
What is the rate limiting step in ACh synthesis
The movement of choline into the neuron
36
How does choline enter the neuron from the extracellular fluid?
Coupled transport with sodium through a symport channel
37
Name three AChE inhibitors
Insecticides, Nerve gas, Alzheimers treatments
38
Name 4 things associated with ACh
Mood, Sleep pattern, Memory, Co-ordination
39
What behaviours of the brain are the catecholamine neurotransmitters associated with
Movement, Mood, Attention, visceral function
40
Outline the synthesis of catecholamines from tyrosine
Tyrosine, dopa, Dopamine, Norepinephrine, Epinephrine
41
What two things make up the striatum?
Caudate nucleus and the putamen
42
What does the striatum essentially act as?
A system that inhibits motor function through stimulation by ACh
43
What inhibits cells of the striatum
Dopamine via D2 receptors
44
What is lost in Parkinsons
The inhibition of the striatum due to either lack of dopamine or lack of D2 receptor response or receptors altogether resulting in increased inhibition of motor function from the striatum
45
What does L-Dopa treatment do
Increases amounts of dopamine causing greater inhibition of the striatum - however can become ineffective over time and cause L-dopa syndrome
46
What does Dopamine inhibit production of from the pituitary gland
Prolactin
47
What are catecholamines metabolised by
MAO A - Mainly Noradrenaline and serotonin
| MAO B - Mainly dopamine
48
What have MAO inhibitors been used for
Treatment of depression - increased levels of serotonin and Noradrenaline
Treatment of Parkinson's disease - Increased levels of Dopamine
49
Give three chemicals used for the treatment of depression
1 - Tricyclics, block uptake
2 - Specific serotonin repute inhibitors (SSRI's)
3 - MAO-A inhibitors
50
What is the fovea
The thinnest part of the retina and marks its centre
51
What is the structure called at the middle of the retina that is responsible for central vision?
The macula
52
What specialisation is there for blood vessels in the eye surrounding the macula
They arc around it as to not cast shadows onto it allowing clear central vision
53
How is the Cornea nourished
By the Aqueous humour that lies behind it
54
What structure suspends the lens in place
ligaments called Zonal fibres attached to the ciliary muscle
55
What differs between the vitreous humour and the aqueous humour?
The vitreous humour is more viscous and jelly like and is there to keep the eyeball spherical
56
What causes glaucoma
High fluid pressure in the eye - pressure in the aqueous humor plays a crucial role in maintaining the shape of the eye - As the pressure increases stress is put on the eye, leading to damage of the weak point where the optic nerve leaves the eye
57
How is vision lost in glaucoma
From the periphery inwards
58
How is cataracts caused and how is it characterised
Caused by low fluid pressure and characterised by a cloudy lens
59
How is accommodation by the lens characterised
Near objects require greater refraction provided by a more spherical lens - This is achieved by contraction of the ciliary muscle so there is less tension in the zonal fibres
60
What does describing the pupillary light reflex as consensual mean
Shining a light in one eye results in constriction of both pupils
61
Outline the steps in the photopupillary reflex
1.Ciliary nerve 3 enters the pons - interneuron in the pre tectal region decussates with the Edinger - Westphal nucleus and the CN3 occula motor sends a signal towards the ciliary ganglion - sends signal to the ciliary nerves and causes muscular contraction causing the pupil to contract - If lost (head collision) suggests problem with this pathway - very serious
62
What is visual acuity
The ability to distinguish two points that are near to each other
63
What is the most direct pathway for visual information to exit the eye?
From photoreceptors to bipolar cells to ganglion cells
64
What two additional cell types are present in the relaying of visual information
Horizontal cells - receive input from photoreceptors and project neurites laterally to influence bipolar cells and other photoreceptors. and amacrine cells - Receive input from bipolar cells and project laterally to influence other bipolar cells, ganglion cells and other amercing cells
65
What cell is the ONLY source of an output from the retina
The ganglion cells
66
Which cell type is the ONLY cell type to produce an action potential and why?
The ganglion cells which is essential for transmitting information outside the eye
67
What is strange about the laminar organisation of the retina
It is inside out - light must travel through the ganglion cells and bipolar cells before reaching the light sensitive photoreceptors
68
Why is having the photoreceptors at the back of the retina advantageous?
Because the pigment epithelium that the photoreceptors lie on plays a critical role in the photoreceptors maintenance and it also absorbs any light that travels all the way through the retina
69
How do rods and cones differ?
Rods contain more disks and make vision in low light more possible
70
How do rods and cones differ other than light sensitivity
Rods only contain one photopigment whereas there are three types of cone cell all with a different pigment - this means cones alone are responsible for our ability to see colour
71
Where are most cones found and why
In the fovea - needed because during daylight we have greater spacial sensitivity on our central retina. Also required because we are poor at distinguishing colours on our peripheral retina due to the lack of cones the further into the periphery you go
72
How are rods more sensitive than cones
More discs - more rods project to more bipolar and ganglion cells through horizontal and amacrine cells thereby aiding the detection of dim light
73
Give the five steps in light transduction in rod cells
1: Light activates rhodopsin
2: Transducin (a G protein) is activated
3: Phosphodiesterase (PDE) an effector enzyme is activated
4: PDE activity reduces the cGMP levels
5: Sodium channels close and the cell membrane hyper polarises
74
What process occurs in the dark in an ON bipolar cell
Sodium channels are open allowing it to diffuse in - it is then pumped out by the sodium potassium pump in a mitochondria filled area and the cell becomes depolarised -40mV - At this level glutamate is released and binds to metabotropic receptors - glutamate inhibits the bipolar cell inhibiting the formation of an action potential in the ganglion cells
75
In the dark are the Na channels in the rod cell open?
No
76
What difference is there between off and on bipolar cells
In an on bipolar cell glutamate inhibits the production of an action potential whereas in an off bipolar cell the production of glutamate is excitatory to the bipolar cell and binds to inotropic receptors
77
When is glutamate released in both off and on bipolar cells
When the rod cell is depolarised (not hyper polarised)
78
What are the four types of lingual papillae
Filiform - spiked, no taste buds, texture, most abundant
Foliate - Least abundant, gone by 2-3 years of age
Fungiform - 3 apical taste buds - especially at the tip and sides of the tongue
Vallate - large, at the back of the tongue, contain half of all tastebuds
79
What's special about sensory cells of the olfactory system
They are neurons and are the only exposed nerve cells in the body, so must be regenerated
80
How does the binding of an odorant protein cause sodium ion channels to open?
The binding causes adenylate cyclase action turning ATP into cAMP which in turn activates ion channel opening
81
What are the olfactory projections?
```
Conscious smell - olfactory cortex
Hypothalamus - sex and neuroendocrine responses
Hippocampus - olfactory memory
Amygdala - emotional response
Reticular formation - visceral responses
```
82
What is the entrance to the internal ear called
auditory canal
83
where does the auditory canal end
the tympanic membrane
84
What are the bones (smallest in the body) that are connected to the eardrum?
Ossicles
85
What do the ossicles produce?
Transfer movements of the eardrum into movements of a second membrane called the oval window
86
What lies behind the oval window
The fluid filled cochlea - which is able to turn the physical motion of the oval window into a neuronal response
87
Where is the visual cortex located?
The most posterior portion of the occipital lobe
88
Where is the auditory cortex located?
In the temporal lobe
89
What is the auditory pathway?
The signal is processed by a series of nuclei in the brainstem, output from these nuclei is relayed to the thalamus (the geniculate nucleus). the MGN projects this information to the auditory cortex
90
What are the three fluid filled chambers the cochlea splits into
scala visibili, scala media, scala tympani
91
What separates the scala tympani from the scala media and what sits on it
The basilar membrane, and the organ of Corti sits on it which contains auditory receptor hormones
92
What fluid fills the scala tympani and scala vestibuli
The perilymph - has an ionic content similar to that of the CSF - low potassium and high sodium
93
What fluid fills the scala media
The endolymph - Similar ionic content to that of intracellular fluid, high potassium and low sodium concentrations
94
How is the difference in ion content maintained
through active transport - absorbs sodium from the endolymph and secretes potassium into it
95
What is the potential difference across Reissner's membrane
80mV - endocochlear potential
96
How does the basilar membrane respond to sound?
Movement of the endolymph causes a movement in the basilar membrane, a bend near its base that propagates as a wave towards the apex. The frequency of the sound determine how far towards the apex the wave travels
97
Where are the auditory receptor cells located
the organ of Corti
98
How does signal transduction occur
The bending of the hair cells, bending in one direction causes depolarisation whereas the other causes hyper polarisation
99
How does a hair cell become depolarised
Bending of the cell causes channel proteins in the stereo cilia to open as the tips become stretched - as a result potassium floods in from the potassium rich endolymph causing depolarisation - calcium channels open in the hair cell leading to the release of the neurotransmitter which diffuses to the postsynaptic neurite of the spiral ganglion
100
Which of the hair cells innervates more than one spiral ganglion neurite
The inner hair cells
101
What is meant by the outer hair cells being the cochlea amplifier
outer hair cells act like tiny motors amplifying the movement of the basilar membrane during low intensity sound stimuli
102
What determines the frequency of sound (pitch)
The nerves activated by the location of stimulus along the basilar membrane
103
What determines the volume of sound
The number of nerves affected and the number of action potentials produced
