Physiology Flashcards
1
Q
What are the two phases of the gait cycle?
A
Stance phase (60% of cycle) Swing phase (40% of cycle)
2
Q
What are the different sections of the stance phase in the gait cycle?
A
1- Heel strike (heel hits ground)
2- Mid stance (tibia parallel to ground)
3- Toe-off (knee flexion has begun, toe leaves ground)
(Stance phase is 60% of gait cycle)
3
Q
What are the different sections of the swing phase in the gait cycle?
A
1- Early swing (hip flexion begins, knee stays in flexion)
2- Late swing (max hip flexion, full knee extension)
4
Q
Connective tissue is mainly made up of what?
A
Collagen
5
Q
What is the function of Cap Z and tropomodulin?
A
Cap Z- Caps +ve end of actin filament at z-disc
Tropomodulin- Caps -ve end of actin filament
6
Q
What is the function of nebulin?
A
Binds actin monomers (around 200) so therefore regulates then length of actin
7
Q
What is the role of A-Actinin?
A
Cross linkings actin filaments at z-disks
8
Q
a) A typical muscle is controlled by how many motor neurons?
b) Each motor neuron controls how many fibres?
A
a) Around 100
b) Around 100-1000
9
Q
What is a muscle unit?
A
Muscle fibres innervated by a single motor neuron
10
Q
What is a motor unit?
A
Muscle unit + motor neuron
11
Q
What is a motor neuron pool?
A
Collection of neurons innervating a single muscle (found in ventral horn of spinal cord)
12
Q
What is a positive allosteric modulator (PAM), aka allosteric enhancer?
A
Amplifies an agonist effect at a receptor
13
Q
What is the definition of awareness?
A
Continuous awareness of the external and internal environment, both past and present, together with the emotions arising from it
14
Q
What are the results of higher than normal or lower than normal CO2 on the blood vessels of the brain?
A
High CO2: Vasodilator
Low CO2: Vasoconstrictor (Reduces blood flow to brain, hence hyperventilating- lowering of CO2 in patients with cerebral oedema)
15
Q
How is arousal (waking from sleep) regulated?
A
By the reticular activating system (in reticular system running from the brain stem to the thalamus and then out to the whole cortex). Simulation of RAS stimulates activation of the cortex
16
Q
How can you be awakened from sleep?
A
Any stimulation of the RAS strong enough to activate it (light, sound, touch), after this +ve feedback from area’s of the cortex (motor/ sensory) keeps the RAS activated
17
Q
What happens when the RAS becomes less responsive to stimulation?
A
RAS becomes less responsive after being activated for many hours, this leads to lethargy and decreased alertness
18
Q
Which neurotransmitters are involved with sleep/ wake cycles?
A
Noradrenaline (stimulates RAS)
Serotonin (inhibits RAS)
19
Q
Amphetamines stimulate the release of which neurotransmitter?
A
Dopamine
20
Q
Drugs which increase serotonin levels well beyond normal would do what?
A
Heighten perception of sensory information and cause possible hallucinations
21
Q
What are the three stages of memory?
A
Perception, storage and retrieval
22
Q
What is normal intercranial pressure for a supine adult?
A
7-15 mmHg
23
Q
How could seizures raise intercranial pressure?
A
Increased oxygen/ blood demands to the brain (raising BP and causing vasodilation)
24
Q
Which neurotransmitters act at each synapse in the autonomic system?
A
All preganglionic: ACh
Parasympathetic postganglionic: ACh
Sympathetic postganglionic: Noradrenaline
25
What is the pathophysiolgy of post traumatic epilepsy?
Of a few days glial and macrophage reactions result in scarring (hemosiderin stained depressions) on the cortex, often leading to PTE (More severe or penetrating injuries most like to lead to PTE)
26
What is the effect of light on melatonin levels?
Melatonin increases as light decreases (so raised melatonin makes you sleepy)
27
What is the raphe nuclei and what is its role in sleep?
In pons and medulla
| Secretes serotonin and has been shown to induce sleep
28
Discharge of noradrenergic neurons in which two brain areas stimulates wakefulness?
Locus ceruleus and serotonergic neurones
| Found in midbrain raphe nucleus
29
What are the functions of sleep spindles and k-complexes? In what sleep phase are they found?
Found in deep sleep phase N2
Sleep spindles: Inhibit thalamus activity to maintain sleep
K-Complex's: Block cortical arousal due to non harmful stimuli (eg light touch) and aids memory consolidation
30
What are the frequency's of alpha, theta and delta waves?
Alpha (N1): 8-13Hz
Theta (N2): 4-7Hz
Delta (N3): 0.5-2Hz
(1Hz is one oscillation per second)
31
Where is and what is the role of the pre-optic area?
In hypothalamus
| Controls thermoregulation and initiates N3 sleep
32
In what order do the stages of sleep happen in a normal sleep cycle?
N1 - N2 - N3 - N2 - REM(20%)
(N3 longest in early night, REM longer at end of night)
The older you are the less time you spend in REM sleep
33
What is the role of adenosine in the CNS?
It is an inhibitory NT (caffeine stimulates by blocking adenosine receptors). Also a vasodilator
- High levels at night lead to sleepiness, low levels in morning lead to wakefulness
34
Where is melatonin produced and how is it's production regulated?
PINEAL GLAND: Lack of light is processed by the SCN (Subchiasmatic nucleus), which stimulates release of melatonin (highest levels 12am-8am), it regulates day-night cycles
35
What is an orthosis?
An externally applied device used to restrict movement or stabilise (e.g. leg callipers)
36
What often causes unconsciousness with a head injury?
Rotational forces causes the grey and white matter to move at different speeds (white is denser) causing shearing injuries to axons or blood vessels
37
What property of general anaesthetics such as propofol make them very useful but also cause the 'hangover effect'?
High lipid solubility (so crosses BBB to act quickly in CNS)
| Hangover due to poor blood flow in adipose tissue so takes time to remove accumulated GA from fat
38
When a ligament is repaired what cell is involved in relaying collagen and which type of collagen is involved?
Fibroblasts
| Type III collagen transformed to type 1
39
The female athlete triad, associated with endurance sports consists of what?
```
Disordered eating (deficient in calories/ calcium)
Amenorrhoea (Shortened luteal phase = low progesterone= an-ovulatory cycles = low oestrogen)
Osteoporosis
```
40
How does training improve muscle performance?
More proteins and therefore more muscle fibres made
41
What types of channel are nicotinic ACh receptors and muscarinic ACh receptors?
Nicotine are ion channels (Na/K/Ca)
| Muscarinic are G-Protein Coupled (work via second messengers, usually cAMP or phospholipase C)
42
Where would LMN cell bodies be found?
Grey matter, ventral horn of spinal cord (flexors in dorsal part, extensors in ventral)
43
What is the difference in connections between skeletal muscle cells and cardiac muscle cells?
Skeletal have no side to side connections whereas cardiac do (allows force to be graduated by activating fewer/ more parts)
44
How does the innervation of muscles with make fine movements differ to those which don't?
More fine movements needed = More nerve fibres per muscle fibre (so less fibres innervated by a single nerve)
45
What is the size principle, and what controls whether it is T1 or T2 muscle fibres which fire?
Small motor neurons activated before LMN
| Therefore more signal will be needed to activate T2 (larger neurons) than T1
46
What is reciprocal inhibition?`
Where spinal inter-neurons inhibit the alpha MN's in antagonist muscles (e.g. when biceps contract, triceps inhibited). Also stops myotatic reflex in antagonist
47
What is the myotatic reflex?
Tendon tap- stretch muscle- stim muscle spindles- excite motor neurons- muscle contraction
(So tap a tendon and get muscle contraction)
AKA LIDDELL- SHERRINGTON REFLEX
48
What are sherrington's first and second law's?
1st: Every post spinal nerve root supplies a dermatome (with some small overlap)
2nd: Law of reciprocal inhibition
49
What is the plantar reflex and the Babinski sign?
Stroke from heel to toe on lateral sole of the foot, normally plantar flexion (toes curl down) observed, the babinski sign is where dorsiflexion is observed and this indicates an UMN lesion
50
What is the normal withdrawal (flexor) reflex?
Pain makes flexors contract (to move limb away)
51
What is the difference between area's controlled by lateral spinal cord pathways and ventromedial spinal cord pathways?
Lateral: Voluntary muscle movement from cortex
Ventromedial: Posture and locomotion from brainstem
52
What is the role of the ryanodine receptor?
Mediates release of calcium ions from the sarcoplasmic reticulum (RyR1 on skeletal muscle, RyR2 on cardiac)
53
What substance present in skeletal muscle can be used for a quick burst of energy?
Creatine phosphate
54
What is oxidative phosphorylation?
Where mitochondria use the energy from going hydrogen + oxygen = water to fuse ADP + phosphate to make ATP. Done through a series of enzyme reactions
55
What is glycolysis?
Uses the conversion of glucose into pyruvate to release energy for ATP creation (from ADP and phosphate)
(Done through a series of 10 enzyme reactions)
(AKA substrate phosphorylation)
56
Where does the Krebs (aka citric acid) cycle take place and what is it's function?
Inside mitochondria, it produces energy, uses oxygen and produces CO2, it converts ADP to ATP.
57
How does the nerve cell ensure exocytosis only happens at the synapse?
Using the V-SNARE protein on the vesicle which has complimentary amino acids to the T-SNARE protein on the membrane of the synapse, they couple together
(Disrupted by botulinum (botox) toxin)
58
What decides the type of muscle fibre any given fibre will be?
The nerve that innervates it
59
How do axons join the NMJ during development?
MUSK protein makes ACh cluster at the motor end plate, the growth cone of the axon releases ACh and these signals cause the joining of the synapse
60
What is excitation-contraction coupling?
Converting of electrical signal into mechanical movement
61
What is the role of desmin, dystrophin and titin?
Desmin: Connects myofibrils laterally at z-discs
Dystrophin: Connects actin to sarcolemma at z-disc
Titin: Binds myosin to z-line (acts as spring)
62
What are the A and I bands? What is the H-zone?
A: Dark bands containing myosin (and ends of actin)
I: Light bands containing actin only
H- zone: Contains myosin only
63
What is actin and what is it made of?
4 kDA Globular protein which makes up thin filament, made up of G-Actin subunits (monomer) to make F-Actin (polymer). Wrapped in tropomyosin and joined to it by troponin
64
What is myosin?
200 kDA globular protein, has two light chains and a head. It is a subclass of ATPase enzymes
65
What are the different forms of troponin and their functions?
Troponin C: Binds with calcium to allow conformation changes in TnI
Troponin I: Binds to actin and troponin T
Troponin T: Binds to tropomyosin and TnI
66
What is tropomyosin?
Double stranded helical coil around actin in the cytoskeleton of all cells. In relaxed state it blocks myosin binding
67
What type of receptor does ACh bind to on the motor end plate?
Nicotinic
68
What trigger causes exocytosis of NT's in a neuron?
An incoming AP first opening Na channels then with further depolarisation opening Ca channels. Ca binds to the vesicles and causes exocytosis
69
What are the characteristics of alpha and gamma motor neurons?
Alpha: Supply extafusal (normal) muscle fibres, they are large and fast (control force)
Gamma: Supply intrafusal (muscle spindle) fibres, they are smaller and slower (spindle responsiveness)
70
What are muscle spindles?
They are mechanosensative ion channels which, in parallel with the muscle, wrapped in group 1a sensory axons which increase firing when the muscle is stretched
71
What are golgi tendon organs?
Detect force of contraction in tendons (run in series), surrounded by sensory 1b neurons, send signals via inhibitory interneurons to inhibit further contraction
72
Name two differences between muscle spindles and golgi tendon organs.
MS: Run in parallel. Use type 1a sensory axons
GTO: Run in series. Use type 1b sensory axons
73
Why can glycolitic ATP generation only be used for a very short period?
Because of build up of lactate and pyruvate in the muscle
74
What are the anatomical differences (size, speed, colour, blood supply) between type 1 and type 2b muscle fibres?
Type I: Small, slow, red (lots of myoglobin/ mitochondria), better blood supply
Type IIb: Larger, faster, white, worse blood supply
75
What are the physiological differences between type I and type IIb muscle fibres?
(Twitch speed/ respiration type/ method/ fatigue resistance)
Type I: Slow twitch, aerobic, oxidative phosphorylation, fatigue resistant
Type II: Fast twitch, anaerobic, glycolytic, fast to fatigue
76
What method do Type IIamuscles use for ATP generation?
Both oxidative phosphorylation and glycolytic (anaerobic and aerobic).
77
What is the gamma loop?
Where gamma motor neurons act on alpha motor neurons to control contraction force
78
Briefly describe the process of transmitting an AP in a synapse?
AP in, VG Na channels open, leads to opening of VG Ca channels, Ca binds to snare proteins on vesicles causing exocytosis in synaptic cleft, NT's bind to receptors on post synaptic membrane which opens ion channels (depolarises next neuron)
79
Name 8 common excitatiory (depolarising) NT's:
Glutamate (Amino acid), serotonin (MA), histamine (MA), dopamine (CA), adrenaline (CA), noradrenalne (CA), endorphin (peptide), acetylcholine
80
Name the two inhibitory (hyperpolarisation) amino acids, what type of molecule are they?
GABA (amino acid)
| Glycine (amino acid)
81
Which three neurotransmitters are classed as catecholamines?
Dopamine, adrenaline and noradrenaline
82
Which three neurotransmitters are amino acids?
GABA, glycine, glutamate
83
Name two monoamine neurotransmitters?
Serotonin and histamine
84
The ventral horn of the spinal cord is made of what type of matter and contains what type of neurons?
Grey matter (cell bodies). Contains the cell bodies of motor neurons (alpha and gamma)
85
What is the contents of the central canal in the spinal cord?
CSF, it is continuous with the ventricular system and is a remnant of the embryological neural tube
86
What is a funiculus?
A bunch of nerve fasicles (which are bunches of nerve fibres, enclosed by a perineurium)
87
What are nociceptors?
Receptors of sensory neurons which respond to potentially damaging stimuli (PAIN)
88
Sensory pain inputs would travel to which parts of the rexed lamina?
I, II and V
89
What are the three types of sensory pain fibres?
Aalpha/beta: Large, myelinated, very fast- Proprioception
Adelta: Medium, thin myelinated, fast: Fast/ localised/ sharp pain
C-Fibres: Small, unmyelinated, slow- Burning/ throbbing and not localised pain
90
Which type of sensory fibres would be responsible for:
a) Pain caused by a pin prick (Sharp, localised)
b) Dull throbbing pain
a) A delta fibres
| b) C- Fibres
91
How many neurons are involved in the spinothalamic pathways and where do each of them travel?
1st order: From source to dorsal horn of spinal cord
2nd order: DH of spinal cord (within 1/2 levels) to thalamus (DECUSSATES IN SPINAL CORD)
3rd order: Thalamus to ipsilateral cortex
92
Where does a sensory 1st order neuron synapse and where are it's cell bodies? Which neurotransmitted does it use to synapse to the 2nd order neuron?
Synapses in dorsal horn of spinal cord
Cell bodies in DRG
NT used is Substance P
93
What are the two parts of the spinothalamic tract and what information does each part carry?
Lateral: Pain and temprature
Ventral: Non- discriminative touch and pressure
94
Where does 1st order neuron information running in the dorsal columns synapse for:
a) Lower limb and medial
b) Upper limb and lateral
a) Nucleus gracilis (in medulla)- THINK G FOR GROUND
| b) Nucleus cuneatus (in medulla)
95
What is the arrangement of neurons in the coricospinal tract?
Decending motor tract
UMN: From cortex to spinal cord (ventral horn)
LMN: From ventral horn to muscle
75% decussate in medulla, other 25% at level needed
96
What information is carried by the dorsal columns?
Discriminative touch, vibration and proprioception
97
What is the name for the nerve which leaves the paravertebral ganglion, heading to an organ? Where does it synapse?
Splanchnic nerve
| Synapses in prevertebral ganglion (don't confused with paravertebral)
98
Where does the sympathetic chain originate and what structure does it travel through just before it reaches the paravertebral ganglion?
Originates: Lateral horn of grey matter
Structure is the white ramus communicantes
99
What is nociception?
The encoding and processing of harmful stimuli
100
What is pain, what % of UK pop have chronic pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage. It is a subjective experience
7% UK pop have chronic pain
101
What is peripheral sensitisation?
Where you have a decreased threshold and and increased responsiveness to pain due to nerve increased responsiveness (due to ATP or PGE2). Normally 75% of C-fibres inactive but PS can activate them (EG SUNBURN)
102
What is central sensitisation?
Increased excitability of CNS neurons as bursts of extreme activity (acute pain) can strengthen synaptic connections permanently (so normally innocuous stimulus causes pain)
103
What are the three types of chronic pain?
Neuropathic: Disease/ injury to nerve
Nociceptive: Due to chronic inflammation
Generalised: Problem with central pain processing
104
What are Schwann cells?
Principle glia in PNS. Provide myelin to PNS nerves.They keep the axons alive (even in unmyelinated). They can stimulate mast cells to degranulate which can result in further/ chronic inflammation
105
What are microglia and how to they changed their morphology?
Macrophage like cells in CNS
Go from Ramified (non activated) to amoeboid (activated), then can then go into either neuroprotective or neurotoxic morphologies (changes cytokine production therefore pain)
106
How can you body dampen the pain pathway?
Pain = increased C fibre firing = increased substance p and glutamate = increased activity post synaptic NMDAR
GABA/ noradrenaline try to inhibit last step
107
What is the structure of neurons in the autonomic NS?
Autonomic NS starts in hypothalamus, then has one UMN and two LMN (one pre and one post ganglionic)
108
Where do sympathetic LMN's have their cell bodies?
Pre ganglionic = Lateral horn of grey mater (spinal cord)
| Post ganglionic= Either para/prevertebral ganglion
109
Where do parasympathetic LMN's have their cell bodies?
Pre-ganglionic: In brainstem or sacral spinal cord
| Post-ganglionic: On isolated ganglion near wall of target organ
110
What neuron transmitters and receptors are involved in the autonomic NS?
ALL preganglionic neurons are nicotinic (ACh)
Sympathetic postganglionic: Adrenoreceptor
Parasympathetic postganglionic: Muscarinic (ACh)
(only exception sweat glands- symp PG release ACh)
111
The mesolimbic reward pathway involves which NT and which part of the brain?
```
Dopamine
Nucleus accumbens (stimulated by medial forebrain bundle)
```
112
Where is the nucelus accumbens found?
In the ventral striatum (part of basal ganglia) at the base of the forebrain
113
What is the gate control theory?
| Melzack and Wall
Small nerve fibres- pain (SNF's) and large- mechanoreceptors (LNF's) have inhibitory interneurons which all synapse to projection neurons. SNF input opens the gate but LNF input closes it (So give LNF input drowns SNF input and closes gate= less pain)
114
What are the main principles behind MR imaging?
Uses NMR spectroscopy, from observing spin of hydrogen atoms (63% of human body). In MRI spin aligns with the field and jumps between energy levels, constantly changing spin
115
Embryologically vertebrae form from the X portions of the Y. What are X and Y and how does this process happen?
X= Sclerotome
Y= Somites
Resegmentation where caudal half of one somite fuses with cephalic half of next somite (so vertebrae formed from two somites)
116
What are the main principles behind PET imaging?
Radiotracer (flurodeoxyglucose) used, which releases gamma waves detected by scanner. Tests how well each scanned area breaks down the tracer. So tests function. Combine with PET-CT for structure and function
117
How are IVD's formed in the embryo?
Mesenchymal cells between the caudal and cephalic parts of each somite do not proliferae but become the IVD's (annulus fibrosus)
118
Embryologically how is the nucleus pulposus formed in the IVD's?
Notochord (which completely regresses in vertebral bodies) but not in IVD's becomes nucleus pulposus. This is later surrounded by circular fibres of annulus fibrosus
119
What are the two key differences between schwann cells and oligodendrocytes?
Schwann cells act in PNS and surround one axon
| OD's act in CNS and one cell surrounds many axons
120
Which cells control myelination in the CNS and PNS and how does this process happen? What is myelin made of?
Schwann (PNS) and oligodendrocytes (CNS)
Myelin wraps around both sides of the sheath then extracellular portions of Protein Zero link on each side
Myelin is 80% lipid and 20% protein
121
What is saltatory conduction?
Where current in myelinated axons jump from one node of ranvier to the next?
122
What are the three types of macroglia?
Oligodendrocytes, schwann cells and astrocytes
123
What are astrocytes and what is their function?
Star shaped macroglia which link synapses and BV'sm they supply nutrients to nerves and can release gliotransmitters to affect signalling.
Most abundant cells in the CNS
124
What are the precursor cells for astrocytes, what are the two types of astrocytes and where would they be found?
```
Precursor: Radial glial cells Become either:
Fibrous astrocytes (in white matter) or
Protoplasmic astrocytes (in grey matter)
```
125
What is an electrotonic potential?
A depolarisation which does not lead the firing of an AP as it does not reach threshold
126
Which T-cells are implicated in the pathophysiology of MS?
T helper 1 cells (Release interferon gamma to activate macrophages)
T helper 17 cells (recruit leukocytes)
127
`At rest an axon has a higher permeability to? (Na or K)
K as more K channels open (Na open when depolarised)
128
Where an how is GABA formed?
From glutamate, in the terminals of gabaergic neurons, by the enzyme GAD (glutamic acid dexarboxylase) which requires vitamin B6
129
What is the difference between GABA A and B receptors?
A: is ionotropic (Cl in to hyperpolarise)
B: is methabotropic (Acts via second messenger)- (Opens K and closes Ca to hyperpolarise)
130
What is serotonin synthesised from and where does this mainly happen?
From tryptophan (large amino acid), mainly in the raphe nuclei of the brainstem
131
What is the synthesis pathway of the catecholamines?
TYROSINE > L-DOPA > DOPAMINE > NORADRENALINE > ADRENALINE
132
What do alpha 1 and 2 adrenoreceptors stimulate and what is the difference between them?
Both stimulate smooth muscle contraction
Alpha 1: By excitation
Alpha 2: By inhibition
133
What is the difference between spatial and temporal summation, which is quicker?
Spatial: Lots of inputs from several neurons simultaneously (QUICKER)
Temporal: Lots of inputs in short succession from 1 neuron
134
What do beta (1-3) adrenoreceptors stimulate?
Heart muscle contraction, smooth muscle relaxation, glycogenolysis
135
Beta adrenoreceptors and alpha 2 receptors all work by which mechanism?
2nd messengers (cAMP)
136
What effect would NA have on alpha 2 receptors on NA or 5-HT neurons?
Decreased cell firing (negative feedback)
137
What effect would NA have on alpha 1 receptors on 5-HT neurons?
Increased cell firing (Just think adrenaline makes you happy via number 1)
138
Which receptors are seen upregulated in chronic depression?
Serotonin (indicating chronically reduced serotonin)
139
Synaptic concentration of which three molecules are increased by antidepressants?
Serotonin, Noradrenaline and BDNF
140
What link has been made between MDD and the amygdala/ hippocampus?
Amygdala over-reactive when see's -ve stimuli
| HIppocampus looses volume
141
What causes low synaptic concentrations of 5-HT and NA in MDD?
High MOA-A activity
142
What is broken down by the enzymes:
MOA-A and MOA-B
Where does this occur?
MOA-A: Serotonin, adrenaline, noradrenaline
MOA-B: Dopamine
(All in pre-synaptic terminal)
143
What is the suggested pathophysiology of depression?
Low levels of serotonin and noradrenaline coupled with a negative cognitive bias (amygdala over-activity).Over-active ventral system (emotional inputs) and under-active dorsal system (emotional significance)
144
What is BDNF?
Brain derived neutrotropic factor: Stimulates survival of neurons and growth of new neurons (so low BDNF causes loss of volume, i.e hippocampus in MDD)
145
An elevated level of what in the CSF could indicate MS?
IgG
146
How does the eye react to bright light? What fibres/ muscles are involved?
PNS impulse= circular muscles (pupillary sphincter) contract = pupil contracts
147
How does the eye react to low light? What fibres/ muscles are involved?
SNS impulse= radial muscles (pupillary dilator) contract = pupil dilates
148
How does the eye react to accomodate for near vision?
PNS fires, ACh at M3 receptors causes cillary muscle contraction = suspensory ligaments relaxtion = lens 'relaxes' and becomes flatter/ more convex/ more circular, (Uses afferent limb of CNII and efferent of CNIII)
149
What is pyramidal patten weakness (often seen in which disease)?
ARMS: Flexors strong, extensors weak
LEGS: Extensors strong, flexors weak
(Often seen in MS)
150
What is a nerve cell approx resting membrane potential, what factors/ equation decide this?
-60mV
By both concentration and electrical gradients
NERST equation
151
What is threshold and how the cell make sure AP's have a limited time span?
Potential needed to open m gate (normally closed) on extracellular side of VGNa channels. A fraction of a millisecond after opening the h gate on the intracellular side (normally open), then closes to stop further influx of Na
152
What are absolute and relative refractory periods?
Absolute: Another AP can't be fired
Relative: Another AP needs a greater than normal threshold to be fired
153
What are oligodendrocytes and what is their fuction?
Provide myelin and support to multiple nerve axons in the CNS
154
What are microglia and what is their function?
They are the macrophages (1st responders) of the CNS
155
What are polydendrocytes and what is their function?
They are progenitor cells to oligodendrocytes, they continue to proliferate into adulthood
156
What are satellite glial cells?
Cover the ganglia of the PNS to create a microenvironment
157
What is the structure of multipolar neurons and where would they be found?
Many dendrites to one axon. Found in hippocampus etc (most common type)
158
What is the structure of bipolar neurons and where would they be found?
1 dendrite to one axon- Found in special senses
159
What is the structure of unipolar neurons and where would they be found?
Tend to be sensory with long axons and quick speeds
160
What are the two types of glutamate receptor?
AMPA: Weak stimulus, most common in CNS does fast, excitatory transmission, 4 binding sites, 2 needed
NMDA: Needs strong stimulus as normally blocked by Mg, ionotropic for Ca which activates 2nd messengers so biggest response
161
What is the cause of low serotonin and NA in patients with MDD?
High MOA-A activity
162
How can stress trigger depression?
HPA dysfunction = increased cortisol = lowered BDNF = decreased serotonin and NA
163
What does MAO-B break down?
Dopamine and Phenylethylamine
164
The striatum is made up of which component nuclei and what type of neurons?
Caudate and putamen
Recieves excitatory glutamate input from the cortex
Has medium spiny neurons (96%) which are inhibitory (GABAergic)
165
Define Dystonia
Abnormal or sustained muscle contractions, often task or position specific, usually resulting in abnormal posture
(Primary dystonia is often genetic with young onset)
166
What is a choreiform disorder?
Characterised by random dancing movements
| E.g. Huntingtons disease or levodopa induced dyskinesia
167
Describe the composition of the BBB?
Endothelial cells allow diffusion of small, lipid soluble molecules (water/ gasses etc) via passive diffusion. Tight junctions between endothelial cells are made up of basement membrane and astrocyte end feet (they control selectivity)
168
How do glutamate and amino acids cross the BBB?
Via transporters
169
What is a circumventricular organ?
E.g. pineal gland which is not surrounded by a BBB
170
What is the normal function (when excited) of the Globus Pallidus internus?
Inhibits the ventrolateral thalamus
171
What is the normal function (when excited) of the globus pallidus externus?
Inhibits the sub thalamic nucleus and therefore the GPi
172
In the direct pathway how is the thalamus excited?
Straitum inhibits GPi so the GPi therefore stops inhibiting the thalamus
173
In the indirect pathway how is the thalamus inhibited?
Striatum inhibits GPe which stops inhibiting the STN which is the allowed to excite the GPi whose normal function is to inhibit the thalamus
174
What is the function of the limbic system?
Preservation of species (safety and reproduction)
| Memory, behaviour, emotion and olfaction
175
What is the function of the amygdaloid body and where would it be found?
F: Fear conditioning plus formation and storage of memory
| Found in the temporal lobe
176
In the brainstem in which regions do afferent and efferent fibres travel?
Efferent travel medially
| Afferent travel laterally
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What fibres are found in the medullary pyramids and what happens at the caudal end of the pyramids?
Corticospinal
| At the caudal ends the fibres decussate
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What are the two lemniscus pathways?
Both Afferent
Medial lemniscus- touch, vibration, proprioception(has cuneate and gracile nuclei)
Lateral lemniscus- Auditory (From cochlear nucleus to inf colliculus)
179
What are the three efferent tracts in the brainstem?
Corticospinal
Corticobulbar (goes from cortex to cranial nerve nuclei with motor function)
Rubrospinal (from red nucleus to spine)
180
The thalamus forms part of the wall of which ventricle? What joins the L/R thalamus across the ventricle?
It forms the lateral wall of the 3rd ventricle
| L and R thalamus is joined by the massa intermedia
181
What is the main role of the hypothalamus?
To join the nervous system to the endocrine system
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What is the function of the internal capsule?
White matter which connects cortex to subcortical areas
183
What is connected by the anterior limb of the internal capsule?
Thalmus to frontal lobe
184
What is connected by the posterior limb of the internal capsule?
Corticospinal and corticobulbar fibres
| Thalamus to somatosensory cortex
185
What is connected by the genu of the internal capsule?
Motor cortex to cranial nerve nuclei
186
What is connected by the retroenticular fibres of the internal capsule?
Medial and lateral geninculate nuclei to audio/ visual systems
187
Briefly describe the plantar reflex
Stroke instrument from heel to toe on lat sole of foot
Plantar flexion normal in adults (toes curl down)
Dorsiflexion (aka babinski response) indicates UMN lesion due to damage of corticospinal tract
188
What is a lacunar stroke?
Make up 25% of ischemic strokes, caused by occlusion of one of the penetrating arteries which supply deep structures (so from circle of willis, basilar art, cerebellar arteries etc)
189
What are the two different pathophysiologies of ischemic strokes?
Atheroma (in large vessels)
| Lipohyalinosis (in small vessels)- Vessel wall thickening due to inflammation, build up of fatty hyaline matter
190
What is a TIA?
A 'mini stroke' where the clot breaks up spontaneously, usually within 30mins so results in no permanent damage. 10% lead onto full stroke
191
What is a soft carotid bruit?
The sound made my a stenosed carotid artery when listened to with a stethoscope. Ultrasound can confirm % stenosis, carotid endartectomy performed if needed
192
Why must tongue swelling be checked for in a patient who has received thrombolytic stroke treatment?
Possible allergic reaction to t-pa
193
What are the definitions (and names) for the area's of perfusion around a stroke?
Core: <20% normal perfusion (die in mins)
Penumbra: 20-50% normal perfusion. Potential for rescue
194
What are the risks of giving thrombolytic (alteplase) treatment?
Haemorrhage (4%)
Cleave NMDA receptor
Degrade BBB
Reperfusion injury
195
By what cellular mechanisms does ischemia cause cell death?
No oxygen or glucose = no ATP
= Ion imbalance (toxic), glutamate release (toxic) and free radical release (toxic)
DNA damage = apoptosis
196
What is the mechanism of reperfusion injury?
Damaged mitochondria can't handle O2 so release free radicals = damage = inflammation = microglia/ astrocyte activation = BBB leakage
197
Concentric centre cells show what firing patterns in response to different stimuli?
No stimulus: Spontaneous firing
Centre stimulus: Fire/ inhbit pattern
Surround stimulus: Inhibit/ fire pattern
198
What is the role of the ventral stream in vision?
Ventral stream = down pathway= WHAT pathway
V1 - V2 - V4 - Inferior temporal cortex
Recognises objects without regard for location
199
What is the role of the dorsal stream in vision?
Dorsal stream = up pathway = WHERE pathway
V1 - V2 - V5 - posterior parietal cortex
Cells send different AP rate based on their angle of gaze (gain field) even though they have the same receptive field
200
What are the two subzones of the V5 cortex area in vision?
MT (Middle temporal) - Simple motion
MST (Medial superior temporal)- Complex motion
Calculate direction of motion from optic flow patterns (predict objects landing)
201
Which two symptoms are most frequently associated with optic neuritis?
Pain
| Loss of colour vision
202
What are osteoclasts?
Large multi-nucleated cells which break down bone matrix
203
What are the principle energy storage molecules used by type IIb muscle fibres?
Creatinine phosphate
| Glycogen
204
What is isometric contraction?
If a muscle contraction is equal to the external force applied, the length of the muscle fibres will remain constant
205
What is the endogenous agonist of the CB1 receptor?
Anandamide
206
What is the role of CB1 receptors and where are they located?
They modulate the release of neurotransmitters
| Found on presynaptic nerve terminals (usually glutamate or GABA)
207
In major depressive disorder, reduced hippocampal volume is most strongly associated with?
Longer duration of untreated depression
208
What % of D2 receptors must be blocked for antipyschotics to have efficacy?
65%
At 72% hyperprolactinaemia
At 75% extra-pyramidal symptoms occur
209
What is the difference between the GABA-A and the GABA-B receptors?
GABA-A: Ligand gated ion channel (Cl- in)
(Needs 2x GABA molecules to bind)
GABA-B: G-Protein coupled receptor (K+ out)
210
What is neuronal tuning?
Neuronal tuning refers to the property of brain cells by which they selectively represent a particular type of sensory, associaction, motor, or cognitive information. Neuronal responses are optimally tuned to specific patterns through experience.
211
What is the locus coeruleus?
Nucleus in the pons associated with stress/ panic response
Principle brain secreting site of noradrenalne
Important in sleep/ wake, memory and emotion
212
What receptor does substance P bind to?
NK-1 receptor
213
How do glucocorticoids reduce inflammation?
Bind to intercellular receptors
Increases transcription of anti-inflam proteins (transactivation)
Decreases transcription of inflammatory proteins i.e leukotrienes/ prostaglandins (transrepression)
214
What are interneurons?
Connect neuron to neuron only, make up 90% of neurons
215
What type of receptors are D1 and D2 receptors?
G- Protein coupled
216
What is the function of D1/D2 receptors in the medium spiny neurons of the basal ganglia?
D1 Activates MSN (Stim adenyl cyclase to convert ATP to cAMP)
D2 Inhibits MSN (inhibits adenyl cyclase)- This pathway not normally very active hence usually GABA fires to GPe in normal indirect pathway, only relevant in PD
217
What is the result of a loss of dopamine on the direct BG pathway?
Less dopamine = less dynorphin = less active MSN's = straitum does less inhibition of GPi which therefore does more inhibition of thalamus which does more inhibition of the cortex
218
What is the result of a loss of dopamine on the indirect BG pathway?
Less dopamine = more enkephalin = less inhibition of MSN = less inhibition of GPe = more inhibition of STN = less excition of GPi = less inhibition of thalamus = more active thalamus to cortex (involuntary)
219
What precursor molecules are associated with the direct and indirect pathway?
Direct: Dynorphin (D1 receptor)
Indirect: Enkephalin (D2 receptor)
