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Medicine phase 1 > week 8 - nervous system > Flashcards

week 8 - nervous system Flashcards

1
Q

functions of frontal lobe

A

responsible for motor control and is involved with retention of long term memories
involved in determining mood and emotions

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2
Q

functions of parietal lobe

A

The parietal lobes can be divided into two functional regions. One involves sensation and perception and the other is concerned with integrating sensory input, primarily with the visual system. The first function integrates sensory information to form a single perception (cognition)

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3
Q

what separates the frontal and parietal lobes

A

central sulcus

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4
Q

functions of occipital lobe

A

it is the main visual cortex and is where dreams are developed and processed

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5
Q

functions of temporal lobe

A

responsible for hearing and interpretation of speech and hearing

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6
Q

functions of cerebellum

A

controls movement specifically coordinating movements

involved with maintenance of posture in space and maintenance of muscle tone

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7
Q

components of the brainstem

A

midbrain
pons
medulla oblongara

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8
Q

functions of brainstem

A

relay tract for motor and sensory systems
also where cranial nerves arise to supply motor and sensory innervation to face and neck
involved in controlling the cardio-respiratory systems

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9
Q

how many of each vertebrae do we have

A 
cervical - 7
thoracic - 12
lumbar - 5
sacral - 5 fused 
coccyx - 3 to 5
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10
Q

what information passes through the dorsal root

A

sensory afferent fibres of spinal nerves

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11
Q

what information passes through the ventral root

A

motor efferent fibres leaving from the ventral gray horn

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12
Q

what is white matter primarily composed of

A

myelinated axons

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13
Q

what is grey matter primarily composed of

A

neurons (cell body, axons, dendrites) and supporting cells (glia)

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14
Q

what does the dorsal root ganglion contain

A

composed of the cell bodies of afferent neurons

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15
Q

what is a nerve plexus

A

a collection of nerves that supply specific body regions

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16
Q

what does the brachial plexus supply

A

goes on to provide motor and sensory innervation to the upper limb

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17
Q

spinal origin of brachial plexus

A

comes from C5 through to T1

sometimes there is a contribution from C4 and T2

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18
Q

what is a dermatome

A

area of skin innervated by the sensory fibres of a single spinal nerve

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19
Q

how many spinal nerves

A

31 pairs

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20
Q

clinical significance of dermatomes

A

can give an indication of the level of the spinal cord where damage may be
a lesion of just a single spinal nerve however would rarely give numbness over that area due to overlap of innervation

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21
Q

how many cranial nerves

A

12 pairs

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22
Q

name the cranial nerves and their functions

A
  1. Olfactory - smell
  2. Optic - vision
  3. Oculomotor – eye movements
  4. Trochlear – eye movements
  5. Trigeminal – motor to muscles of mastication and general sensory to the face
  6. Abducens – eye movements
  7. Facial – muscles of facial expression
  8. Vestibulocochlear – hearing and balance
  9. Glossopharyngeal – swallowing, taste
  10. Vagus – wandering nerve supplying heart, lungs, gut – reduces heart rate, reduces breathing, increases gut motility – nerve of rest and digest
  11. Spinal accessory – neck muscles
  12. Hypoglossal– muscles of the tongue
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23
Q

what do the cranial nerves supply

A

head and neck structures as well as the gut, heart and respiratory system

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24
Q

three meninges in order of deep to superficial

A

pia mater
arachnoid mater
dura mater

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25
Q

function of meninges

A

They provide a supportive and structural framework for the vasculature, and also protect the CNS from mechanical damage, aided by the cerebrospinal fluid

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26
Q

what is contained in the lateral ventricles

A

cerebrospinal fluid

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27
Q

where does venous blood from the brain drain to

A

dural venous sinuses and ultimately to the internal jugular veins

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28
Q

from what vertebral levels does the sympathetic nervous system arise

A

T1-L2

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29
Q

origins of the parasympathetic nervous system

A

cranial nerves III, VII, IX and X and S2-4

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30
Q

where does the spinal cord terminate in an adult

A

L2 approximately

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31
Q

what is the clinical relevance of the termination of the spinal cord at a higher
vertebral level

A

A sample of cerebrospinal fluid can be taken (to examine for infection eg meningitis) after the spinal cord terminates. Generally, this is taken from the space between L3/4 or L4/5 to ensure no damage is done to the spinal cord

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32
Q

function of corpus callosum

A

responsible for communication between the two cerebral hemispheres

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33
Q

hypothalamus function

A

responsible for homeostasis

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34
Q

thalamus function

A

primarily functions as a relay centre for fibres passing up to the brain and down to the rest of the body
regulation of consciousness and alertness

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35
Q

components of the peripheral NS

A

spinal and cranial nerves

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36
Q

what separates the 2 brain hemispheres

A

groove called the longitudinal fissure

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37
Q

what are the wrinkles on the brain

A

Brain is folded into gyri (ridges) and sulci (grooves in between) – helps increase surface area in the space limiting skull

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38
Q

what is the telencephalon

A

cerebrum

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39
Q

diencephalon components

A

thalamus and hypothalamus

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40
Q

mesencephalon

A

midbrain

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41
Q

what do the telencephalon and diencephalon make up

A

the forebrain

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42
Q

glial cells and their functions

A

astrocytes - involved in nutrient supply to neurons in CNS
microglia - defence role; phagocytic
ependymal cells - involved in production of CSF
oligodendrocytes - neuronal support and myelin formation in the CNS
schwann cells - neuronal support and myelin formation in the PNS

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43
Q

dendrite function

A

specialised to receive chemical signals from the axon termini of other neurons
Dendrites convert these signals into small electric impulses and transmit them inward, in the direction of the cell body

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44
Q

describe myelin

A

the layers of fatty tissue around an axon

protects, insulates and allows faster propagation of nerve impulse

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45
Q

describe the nodes of ranvier

A

gaps found within myelinated axons- they speed up propagation of action potentials along the axon

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46
Q

describe the central canal of the spinal cord

A

it is a hole in the middle of spinal cord and is surrounded by ependymal cells

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47
Q

what are denticulate ligaments

A

paired ribbon-like extensions of pia mater that attach to dura mater

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48
Q

what is the filum terminale

A

pia mater extensions that stabilise spinal cord

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49
Q

describe the point where the spinal cord ends

A

Conus medullaris is where the spinal cord ends – surrounded by lumbosacral roots collectively referred to as cauda equina – L1-L2

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50
Q

describe the cauda equina

A

Nerve rootlets comprised of L2-5
cauda equina sits in a space called the lumbar cistern which is a space formed by the subarachnoid space. It extends from the conus medullaris to S2

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51
Q

two layers of dura mater

A

periosteal and meningeal

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52
Q

which spinal nerve does not have a dermatome and why

A

C1 does not have a dorsal sensory root and so has no dermatome associated with it
it has a motor root which supplies neck and muscles

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53
Q

3 classifications of PNS nerves

A

pseudounipolar neuron
multipolar neuron
autonomic multi-polar neuron

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54
Q

describe a pseudounipolar neuron

A

has one extension from its cell body and it splits into 2 branches - one goes peripherally and the other centrally

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55
Q

describe a multipolar neuron

A

single axon and has many dendrites - typically motor neurons

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56
Q

describe an autonomic multi-polar neuron

A

there is a synapse between the presynaptic and postsynaptic neuron
comes from the lateral horn

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57
Q

variations of neuron

A

unipolar, bipolar and multipolar

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58
Q

what kind if neuron is a sensory neuron

A

unipolar

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59
Q

difference between grey and white matter

A

grey has more cell bodies, dendrites, axon termini, astrocytes and blood vessels
white has more axons (myelinated), glial cells (oligodendrocytes), blood vessels

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60
Q

name of a group of neurons

A

called a nucleus in the CNS and a ganglion in the PNS

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61
Q

what is a cortex

A

neurons that are organised into layers and are usually found on the surface of the CNS

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62
Q

functions of the dorsal and ventral horn

A

Within the gray matter the dorsal horn receives and processes sensory information from the dorsal roots, whereas the ventral horn is primarily a motor structure and contains the motor neurons whose axons project out via the ventral roots

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63
Q

location of CSF

A

it fills the ventricular system, a series of interconnected spaces within the brain, and the subarachnoid space directly surrounding the brain

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64
Q

what are subarachnoid cisterns

A

CSF circulates through the subarachnoid space surrounding brain and spinal cord. Regions where these spaces are expanded are called subarachnoid cisterns.

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65
Q

describe spinal cord tracts

A

bundles of nerve fibres that run up/down and can contain autonomic, sensory and motor fibres

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66
Q

types of spinal cord tracts

A 
spinothalamic = ascending and sensory
corticospinal = descending and motor
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67
Q

what are dural venous sinuses

A

spaces between the endosteal and meningeal layers of the dura
they contain venous blood that originates for the most part from the brain or cranial cavity
the sinuses contain an endothelial lining that is continuous into the veins that are connected to them

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68
Q

function of CSF

A

cushions brain against impact/movement and against its own weight
provides a stale chemical environment for the brain
allows nutrient and waste exchange between nervous tissue and blood

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69
Q

production of CSF

A

Most produced by choroid plexus in lateral and fourth ventricles
Resorbed into venous system via arachnoid granulations

70
Q

structural features of the blood-brain barrier

A

restriction is at least partly due to the barrier action of the capillary endothelial cells of the CNS and the tight junctions between them
Astrocytes may also help limit the movement of certain substances

71
Q

two parts of the human nervous system

A

somatic (we have active control over) and autonomic (we do not control)

72
Q

which cortex’s does the frontal lobe contain

A

motor cortex - involved in planning and coordinating movement
prefrontal cortex - responsible for higher-level cognitive functioning

73
Q

describe brocas area

A

region in the frontal lobe of the dominant hemisphere, usually the left, of the brain with functions linked to speech production

74
Q

two parts of the ANS

A

central and peripheral

75
Q

two parts to the peripheral NS

A

sympathetic and parasympathetic

76
Q

function of the parasympathetic NS

A

responsible for the body’s rest and digestion response when the body is relaxed, resting, or feeding
it decreases respiration and heart rate and increases digestion

77
Q

function of the sympathetic NS

A

it directs the body’s rapid involuntary response to dangerous or stressful situations

78
Q

where do preganglionic neurons arise from (SNS)

A

lumbar and thoracic regions of spinal cord

79
Q

describe the SNS process

A

preganglionic fibres go to sympathetic ganglia chain - some fibres synapse immediately, some travel up or down ganglia first and some pass through the chain without synapsing (synapse at collateral ganglia instead)
from ganglia, the postganglionic fibres run to target organs

80
Q

where do preganglionic neurons arise from (parasympathetic NS)

A

brainstem and sacral region of spinal cord

81
Q

describe the process of the PSNS

A

preganglionic neurons exit from cranial nerves and spinal cord

82
Q

neurotransmitters in SNS

A

preganglionic neurons use acetylcholine

postganglionic neurons use noradrenaline except in sweat glands and deep muscle veins when it uses acetylcholine

83
Q

types of receptors in the SNS and their functions

A

alpha 1 - causes arteriole constriction
alpha 2 - causes venous and coronary vasoconstriction
beta 1 - increases heart rate and increases contractility
beta 2 - causes smooth muscle relaxation

84
Q

agonist

A

mimics the action of a recptor

85
Q

antagonist

A

these oppose the action of a receptor

86
Q

examples of alpha 1 agonist drugs

A

metaraminol
pseudoephedrine
phenylephrine

87
Q

alpha 1 antagonist drug

A

doxazosin

88
Q

alpha 2 agonist drugs

A

anti-erectile dysfunction drugs

89
Q

b1 agonist drug

A

isoprenaline

90
Q

b2 agonist drug

A

salbutamol

91
Q

when are b2 antagonist drugs used

A

only in lab - no clinical use

92
Q

actions of the PSNS

A

Pupillary constriction – improves near vision
Nasal engorgement – maximises sensory absorption
Excess salvation – aids digestion
Increased gastric secretions and blood flow
Slow heart rate down
Bronchoconstriction
Micturate, defecate and ejaculate

93
Q

origin of SNS

A

thoracolumbar except for cervical ganglia

94
Q

origin of PSNS

A

origin has two parts - cranial and sacral
Cranial is made of the 3rd, 7th, 9th and 10th nerves
Sacral is 2, 3, 4

95
Q

neurotransmitter for PSNS

A

acetylcholine

96
Q

3 ganglia associated with the vagus nerve

A

cervical, thoracic and coeliac ganglia

97
Q

muscarinic receptors

A

G-coupled protein receptors involved in the parasympathetic nervous system

98
Q

functions of the muscarinic receptors

A

M1 - affects arousal attention and emotional response
M2 - cardiac inhibition
M3 - lacrimal, salivary
M4 - direct regulatory action on K and Ca ion channels
M5 - may regulate dopamine release at terminals within the straitum

99
Q

M1 agonist drug

A

xanomeline - potential treatment of alzheimers and schizophrenia

100
Q

receptors of the PSNS

A

muscarinic and nicotinic receptors

101
Q

describe nicotinic receptors

A

receptors that respond to acetylcholine

also respond to nicotine

102
Q

B1 antagonist drugs

A

these bind to receptors and block it (beta blockers)

atenolol - lowers bp and heart rate

103
Q

what does brainstem death lead to

A

paralysis and unconsciousness
apnoea
loss of cranial nerve function

104
Q

coning of the brain process

A

pressure build up and causes a decrease in the blood flow
swelling of brain forces the brain through small opening at the base of skull where it meets the spinal cord
restricted blood supply to brainstem

105
Q

brainstem blood supply

A

single blood vessel called basal artery

106
Q

what condition is a result of damage to the basal artery

A

locked-in syndrome - can think and move eyes but cannot speak or move

107
Q

brainstem death example tests

A

9th – spatula at back of throat and patient should gag
for 5th nerve – brush cotton wool against cornea – should cause blinking
test for oculomotor cranial nerve – opening eyes, shining light and looking for consensual reflexes

108
Q

guided therapy

A

used in mild infections when you can wait a few days before treatment
allows best antibiotic to be selected

109
Q

empirical therapy

A

used when a delay in therapy results in worsening of condition

110
Q

prophylactic therapy

A

used when healthy people are exposed to surgery, injury or infected material
used in immunocompromised patients
preventing infection before it begins

111
Q

types of antibiotic

A

bactericidal - directly kills bacteria and sterilises area

bacteriostatic - bacteria remain in medium but are dormant

112
Q

example of bactericidal and bacteriostatic antibiotics

A

bactericidal - penicillin

bacteriostatic - clarithromycin

113
Q

which classes of antibiotics target cell walls

A

penicillins and glycopeptides

114
Q

classes of antibiotics that target ribosomes

A

macrolides

aminoglycosides

115
Q

classes of antibiotics that target DNA

A

quinolones

116
Q

classes of antibiotics that target metabolism

A

trimethoprim

117
Q

what group of antibiotics do penicillins belong to

A

beta-lactum group

these drugs are chemically produced derivatives of naturally occurring beta-lactums

118
Q

how do penicillins work

A

they target penicillin binding proteins which are present in or around peptidoglycan cell wall - penicillin inserts into binding site of penicillin binding proteins and prevents peptidoglycan synthesis

119
Q

3 principal mechanisms of antibiotic resistance

A

mutation/modification of target site
inactivating enzymes
limit access eg. reduced permeability

120
Q

how is resistance passed on in bacteria

A

genes mediating resistance can often easily be transferred – often found on plasmids which bacteria pass onto each other

121
Q

what is adrenaline

A

a hormone produced by the adrenal glands in situations of acute stress

122
Q

when is adrenaline produced

A

stimulation of SNS causes adrenal medulla to produce adrenaline

123
Q

effects of adrenaline

A

increases heart rate and respiration

mobilises blood glucose stores

124
Q

where is adrenal medulla derived from

A

embryonic neural crest cells

rest of adrenal gland is derived from mesoderm

125
Q

adrenaline signalling process

A

adrenaline binds to and activates a g-protein coupled receptor

126
Q

how do g-proteins work

A

g-proteins only active when bound to GTP
g-protein-coupled receptors use large heterotrimeric g-proteins
an activated g-protein activates downstream effector proteins
GTPase activating protein and regulators of g-protein signalling cause hydrolysis of GTP to GDP

127
Q

effects of g-protein coupled receptor (GPCR) activation

A

alpha subunits in particular (but also beta and gamma) can target multiple different effector proteins when activated - can activate or inhibit targets directly or indirectly
some GPCRs work through producing second messenger molecules

128
Q

describe adrenaline signalling and glucose release in muscle and liver cells

A

adrenaline binds to GPCR triggering activation of g-protein alpha subunit which activates adenylyl cyclase which produces cAMP
cAMP activates protein kinase A
this leads to glucose production and inhibition of glycogen synthesis

129
Q

what 2 things does activated protein kinase A do

A

PKA phosphorylates and activates phosphorylase kinase which phosphorylates and activates the enzyme glycogen phosphorylase which catalyses breakdown of storage molecule glycogen, to produce glucose
PKA also phosphorylates and inhibits the enzyme glycogen synthase so glycogen synthesis cannot occur

130
Q

switching the signal off (adrenaline signalling)

A

when adrenaline is no longer present, signalling process must be switched off
g-protein alpha subunit hydrolyses GTP to inactive GDP (cannot activate adenylyl cyclase so no new cAMP produced)
cAMP removed by phosphodiesterases
calcium ions acting as second messengers can be actively removed by using ion channel pumps

131
Q

what is a nerve impulse

A

wave of altered charge across nerve cell membrane that sweeps along axon aka. Depolarisation or action potential

132
Q

direction of travel for Na and K ions in a cell

A

sodium is the main EXTRAcellular ion - can diffuse into cell
potassium is the main INTRAcellular ion - can diffuse out of cell
sodium potassium pump actively pumps out 3 Na ions and takes in 2 K ions

133
Q

refractory period

A

time following action potential when no new AP can be initiated in same area of the membrane - blocks action potential travelling backwards

134
Q

two segments of the refractory period

A

absolute RF - sodium channels that caused initial depolarisation are closed and cannot be activated
relative RF - sodium channels can work but because it would be starting from a hyperpolarised -90mV, it is hard to reach the threshold voltage for an AP

135
Q

when do the different channels open

A

voltage-gated – changes in membrane potential
ligand-gated – specific ligand binding to receptor
mechanically-gated – tension in membrane
leakage – opens randomly – only channels open at rest

136
Q

why is the resting potential of a neuron negative (less positive)

A

more Na+ ions outside the cell than K+ ions in cell
sodium/potassium pump uses energy from hydrolysis of ATP to pump 3 Na+ out and 2 K+ into cell
ions can pass through membrane through leakage channels - membrane is more permeable to K+ than Na+

137
Q

describe myelin (on a neuron)

A

fatty substance that insulates a neuron, blocking depolarisation
current travels through the myelinated stretches of a neuron and depolarises the membrane only at the nodes of ranvier – myelin increases the speed of transmission

138
Q

how can an action potential be triggered in a neuron

A

some stimuli can directly activate the nerve cell
or
a neurotransmitter from a nearby neuron can bind to a receptor on the nerve cell - receptor activation causes ion movement that triggers an AP in first neuron

139
Q

excitatory pre-synaptic potenitals

A

inputs that increase plasma membrane potential making it more likely that the threshold voltage will be met and an action potential generated

140
Q

inhibitory pre-synaptic potentials

A

decrease plasma membrane potential making it less likely that the threshold voltage will be met and an action potential generated

141
Q

describe the two types of summation

A

spatial - summation of inputs from different areas such as from different dendrites
temporal - same input occurs multiple times within a short time period - not enough time for the change in potential that was caused by first wave to fall/rise bacl to resting potential before second wave of input hits - with an excitory input, threshold voltage for AP can be reached quicker

142
Q

what are synapses made of

A

a presyntaptic nerve axon terminus and a postsynaptic nerve dendrite with a gap (synaptic cleft) between

143
Q

neurotransmitters

A

(bio)chemical signals that neurons use to cross the synaptic cleft

144
Q

describe signalling across the synapse with a neurotransmitter

A

released when AP reaches presynaptic neuron termini, then it diffuses across the synaptic gap
binds to receptors on dendrites of postsynaptic neuron
different NTs associated with different nervous system functions
NT can be excitatory or inhibitory

145
Q

chemical classifications of NTs

A

amino-acids and derivatives - e.g. glutamate and GABA
catecholamine (monoamines) - derived from Tyr eg. dopamine, serotonin
acetylcholine - derived from choline
peptides eg. substance P, endorphins

146
Q

where is glutamate found

A

main excitatory NT in CNS

147
Q

where is GABA found

A

main inhibitory NT in CNS

148
Q

GABA signalling process

A

GABA binds to GABA-A receptor which is an ion channel - binding causes conformational change that opens chloride ion channel
ions move through channel along conc. gradient
GABA released from presynaptic neuron into synapse - diffuses across cleft and binds to GABA-A receptor in post-synaptic neuron membrane
Neurotransmitters can be removed from synapse:
Reuptake of neurotransmitter through specific reuptake transporters
Presence of specific enzymes which chemically degrade the NTs

149
Q

signalling pathway for acetylcholine at NMJ

A

AP travels down axon, Ach released from axon termini and diffuses across gap, binds to the nicotinic Ach receptor (sodium ion channel receptor) on postsynaptic muscle cell membrane (motor end plate)

150
Q

difference between introns and exons

A

exons – kept when coding for proteins

introns – do not take part in translation

151
Q

why is the protein coding region smaller than the RNA coding regio

A

some of the RNA is not translated and instead can be either a cap addition site (adds a protective nucleotide on the end of mRNA) or a polyA addition site which adds lots of nucleotides to protect the end of the mRNA

152
Q

describe the 3 steps of transcription

A

Initiation: RNA polymerase II comes to the start of gene, DNA strands pulled apart
Elongation: RNA gets longer and it forms a transcription bubble
Termination: RNA synthesis stops

153
Q

processing of primary mRNA

A

Primary RNA transcript includes introns
Processing occurs in nucleus
RNA splicing is the removal of introns by spliceosome
mRNA has a cap and polyA tail – exported to cytoplasm for translation

154
Q

what are transcription factors and what do they do

A

proteins that bind very tightly to short and very specific sequences of DNA to affect the rate of transcription (positively or negatively)
determine how much protein is made from each gene

155
Q

examples of transcription factors

A

p53 and E2F in cell cycle
nuclear hormone receptors (ligand dependant transcription factors) -
glucocorticoid receptor, oestrogen receptor, testosterone receptor, retinoic acid receptors

156
Q

how is transcription initiated

A

a transcription initiation complex (TIC) needed
RNA II polymerase cannot bind directly to DNA so general or basal transcription factors act as bridge - these TFs bind to sequences of DNA called the TATA box and are usually found slightly before the start sites for transcription
promoters are sequences of DNA that proteins initiating transcription bind to
TFs on upstream enhancer elements further stabilise TIC

157
Q

disease from mutation CCR5 promoter

A

affects rate that HIV progresses to AIDS

158
Q

mutations in factor IX promoter lead to

A

haemophilia B

159
Q

what regulates transcription

A

enhancers and silencers
these are DNA sequences where transcription factors bind to affect rate of transcription
enhancers make it more likely that promoter will be activated, silencers make it less likely

160
Q

example of activators in gene expression

A

p53 - activator of transcription of p21 causing cell cycle arrest and DNA repair
E2F - activator of transcription of genes needed for S phase

161
Q

examples of repressors in gene expression

A

p53 - repressor of transcription of survivin causing apoptosis
Oct-1 - repressor of transcription of thyroid stimulating hormone in all cells apart from thyrotrophs in the pituitary

162
Q

how does DNA being closed regulate gene expression

A

nucleosomes keep DNA closed meaning the DNA is not accessible to TFs
super enhancers called locus regions can open chromatin spanning several genes

163
Q

examples of constitutive genes

A

beta-actin (microfilaments)
ribosomal proteins
general/basal TFs

164
Q

what are constitutive genes

A

Constitutive genes = housekeeping genes

have a constitutive promoter

165
Q

what are inducible genes

A

genes which are only expressed in certain tissues or cells and are only expressed at certain times

166
Q

examples of inducible genes

A

cell specific -CD4, CD8, collagen 1 and 2, globin, myelin

time specific - cyclins, melatonin, inflammatory cytokines

167
Q

describe alternative splicing

A

Exons stay in the same order but different exons are used to make different mRNAs and proteins from same gene

168
Q

clinical relevance of the genome

A

can look at genome and check whether they are expressing a normal protein or a mutated version

169
Q

clinical relevance of the transcriptome

A

can identify signalling pathways acting in the cell/tissue

can differentiate between different diseases

170
Q

clinical relevance of the proteome

A

can be profiled and used for diagnosis, prognosis and treatment selection

Medicine phase 1 (14 decks)

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