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NEUROLOGY > PHYSIOLOGY > Flashcards

PHYSIOLOGY Flashcards

1
Q

what are the function of neurons

A

they sense chnage and communicate with other neurons

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2
Q

what are the function of glial cells

A

support, nourish, insulate neurons and remove waste

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3
Q

what does the soma contain

A

nucleus, mitochondria, golgi apparatus and nissl substance

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4
Q

what is nissl substance

A

granules containing rough endoplasmic reticulum and ribosomes (site of protein synthesis)

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5
Q

what is the function of dendrites

A

transmit signals from other neurons to the soma

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6
Q

where do axons arise from

A

an area in the soma called the axon hillocks (where APs are initiated)

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7
Q

what do schwann cells do

A

they insulate the axon, aiding rapid transmission of AP (PNS) - lots of schwann cells insulate one axon

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8
Q

what do oligodendrocytes do

A

insulate axons by producing a myelin sheath, aiding rapid transmission of AP (CNS)- one oligodendrocyte can insulate lots of axons

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9
Q

what are astrocytes

A

starshaped glial cells (30-40% of glial cells)

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10
Q

what is the funtion of astrocytes

A
  • provide metabolic support by store glycogen which breaks down into glucose to provide fuel for neurons
  • store lactate, fuel for high energy consumption or ischeamia
  • regulates extracellular ionic environment, increases K+ ion–> depolarisation (so astrocytes remove k+ from extra cellular space)
  • contain specific transporters for NT such as glutamate: rapid removal of NT from the exxtracellular space is needed for the normal function of neurons
  • promotes myelination by oligodendrocytes
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11
Q

what is the function of microglia

A

phagocytic and immunocompetent cells of the nervous system. They are active in response to tissue damage and have the capacity to recognise foreign antigens and initiate phagocytosis (can also function as antigen presenting cells)

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12
Q

what are ependymal cells

A

the ependyma is the thin layer lining the ventricular system (made up of ependymal cells) Their basal membrane is attached to astrocytes and produce CSF as part of the choroid plexus

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13
Q

what does cilia and microvilli do in terms of CSF

A

Aids circulation and absorption

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14
Q

what are neurotransmitters

A

endogenous chemicals able to communicate with the nervous system and the rest of the body. They relay info between the neurons and regulate bodily functions

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15
Q

where do neurons transmit signals accross a synapse (3)

A
  • neuron –> neuron
  • neuron–> muscle at a NMJ
  • neuron –> gland
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16
Q

what are the 3 main componenets of a synapse

A
  1. axon terminal (where info is coming from)
  2. synaptic cleft
  3. dendrite (where info is received)
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17
Q

is there NT release without stimulation

A

there is a baseline NT release without stimulation, but when an AP comes along the number of NT released increases in response

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18
Q

what happens when the NT binds to the post synaptic neuron

A

either excitation or inhibition, depending on which NT is release and which receptor it binds to

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19
Q

what does it mean when a NT has neuromodulatory actoin

A

they can act on a large number of of neurons at once (this is a slower action)

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20
Q

Classes of NT (in terms of structure)

A
  • monoamines :dopamine, noradrenaline, adrenaline, histamine, serotonin
  • amino acids: glutamate, glycine, GABA, D-serine
  • peptides: opiods, endorphins, oxytocin
  • other: aCh, adenosine, nitric oxide
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21
Q

Classes of NT (in terms of function)

A
  • excitatoy (glutamate, facils the transmission of AP)
  • inhibitory (GABA/ glycine, prevents propagation of AP)
  • neuromodulatory (alters strength of transmission and affects the amount of NT produced)
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22
Q

What is glutamate

A

the most abundant NT in the brain, major excitatoty NT

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23
Q

what receptors does glutamate bind to (3)

A
  1. NMDA receptors, an inotropic receptor, permeable to Na, K and Ca (high permeability to Ca which can promote neurotoxicity- ketamine is a selective blocker of NMDA)
  2. AMPA (non-NMDA) receptors, inotropic, permeable to Na and K (fast excitability)
  3. metabotropic G-protein coupled receptors (this gives an inhibitory effect)
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24
Q

For what function is glutamate essential

A

memory and learning

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25
Q

where is acetylcholine used

A

in the CNS and PNS (in particular the NMJ)

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26
Q

where is Ach synthesised and from what

A

in the neurons from choine and acetyl-CoA (excitatory NT)

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27
Q

what receptors does Ach bind to

A
  • Nicotinic Ach receptors: inotropic, found in the NMJ in the CNS, parasympathetic and sympathetic nervous systems
  • Muscarinic Ach receptors: G- protein coupled receptors in the CNS and within the post ganglionic parasympathetic neurons
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28
Q

what function is Ach used for

A

NMJ, arousal, attention, digestion and salivation

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29
Q

how is GABA synthesised

A

from glutamate and is an inhibitory NT in the CNS

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30
Q

what receptors does GABA bind to

A

GABA A: inotropic, permeable to cl and bicarb ions

GABA B: g-coupled receptors

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31
Q

what effect does GABA have

A

rapid inhib effects when binding to post synaptic receptors and also slower inhib via neuromodulation at pre synaptic receptors

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32
Q

what kind of NT is glycine

A

an inhib NT in the spinal cord and brainstem

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33
Q

what kind of receptors does glycine bind to

A

inotropic receptor

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34
Q

what is the CNS and what are its functions

A

it is the central nervous system and it controls our body/s voluntary and involuntary functions. It is important for generating our thoughts and interpretating info from the PNS and responding appropriately

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35
Q

what is the function of the ascending tracts

A

to relay sensory info from the PNS to the brain

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36
Q

what is the functio of the descending tracts

A

send motor signals from the brain to lower motor neurons

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37
Q

What does the PNS consist of (2)

A
  1. the somatic nervous system

2. the autonomic nervous system (para/sympathetic)

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38
Q

what is an afferent

A

sensory neurons running from the receptors for stimuli–> CNS (somatic and autonomic NS)

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39
Q

what is an efferent

A

motor neurons running from the CNS to the effector organs (muscles or glands)

  • somatic= voluntary, conscious control of skeletal muscles
  • autonomic= (visceral) regulation of HR, digestion, salivation and urination
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40
Q

what does sympathetic mean?

A

fight or flight
originates from the thoracocolumnar segments
uses preganglionic and long post ganglionic neurons
pre ganglionic NT= Ach
post ganglionic NT= noradrenaline
used in stressful situations

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41
Q

what does parasympathetic mean?

A

rest and digest
originates from the craniosacral segments
long preganlionic and short postganglionic neurons
NT= ach

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42
Q

what is the enteric NS

A

it is embedded in the lining of the GI tract, the PNS stmulates the ENS to increase function

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43
Q

what is CSF

A

It surrounds the brain and spinal cord, it is an ultra filtrate of blood plasma and is contained within the sub arachnoid space

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44
Q

where is CSF produced

A

in the choroid plexus in the 2 lateral ventricles and the roof of the 3rd/4th ventricle

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45
Q

how much csf is produced everyday

A

500ml

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46
Q

how is the CSF made

A

the blood plasma is filtered through the fenestrated epithelium of the ventricles, which only allows for passage of some products. There is then some active transport of some substanes through the ependymal cells.

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47
Q

describe CSF drainage

A

drains via the superior sagital sinus through arachnoid villi

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48
Q

what are the functions of CSF (4)

A
  1. buoyancy: brain weighs 1400g but due to CSF creating a bath for the brain it has a net weight of 50g
  2. protection: shock absorber
  3. homeostasis: regulates distribution of metabolites surrounding the brain
  4. clearing system: waste products produced by the brain move into CSF
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49
Q

what is the rough resting membrane potential

A

-50 to -75 mV ( this value depends of the channels that are open and the concentrations of different ions inthe intre and extracellular fluid)

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50
Q

where is K+ in higher conc in neurons

A

inside the cell

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51
Q

where is Na+/cl- in higher conc in neurons

A

outside the cell

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52
Q

what ion has the greatest influence on membrane potential

A

k+ as the cell membrane is most permeable to this, the membrane pot is therefore closest to the equilibrium potential of K

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53
Q

where does an AP arise

A

in the axon hillock due to depolarisation

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54
Q

explain the generation of an AP

A

1.voltage gated Na+ channels open due to a stimuli
2. Na moves into the cell (+ve charge in the cell)
3.if the threshold is reached an AP is generated
4. once cell is depolarised (+ve charge) K+ channels open and move down the gradient out of the cell
5. this causes repolarisation
(repolarisation an overshoot resting membrane potential–> more negative and cause hyperpolarisation)

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55
Q

what happens after an AP

A

there is a refractory period (when Na channels close) in this time stimulation for another AP must be very high, this strength of stimulation required decreases as Na channels recover from inactivation

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56
Q

what is membrane resistance

A

the membrane resistance depends on the number of ion channels open, ie more leaky (a low resistance membrane allows lots of ion movement, and a high resistance membrane does not.)

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57
Q

what are the nodes of renvier

A

periodic gaps of myelin

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58
Q

what are endogenous opiods

A

a npeptide made in the cell body to allow formation of peptide bonds. Made by any secretory protein via transcription in the nucleus and translation in the endplasmic reticulum

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59
Q

How are NT released

A

APs arrive at the synaptic terminals–> stimulate the opening of Ca channels–> influx of Ca in the terminal–> migration of NT vesicles to the pre synaptic membrane–> exocytosis

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60
Q

what are inotropic receptors

A 
ligand gated 
ion influx alters cell voltage
rapid action
short response
DIRECT
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61
Q

what is membrane capacitence

A

the ability to store charge, if a membrane has a high capacitence then a greater distance can be travelled before the threshold is still reached

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62
Q

what are metabotropic receptors

A

G- protein coupled receptors
ligand binds to metabotropic receptor-> activated G protein-> activates another molecule
receptor acts via 2nd messenger to cause cellular effects
slow
prolonged response
INDIRECT

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63
Q

Classes of neurons and examples

A
  • unipolar (one neurite) eg peripheral autonomic neuron
  • pseudopolar (one neurite that splits) eg dorsal root ganglion
  • bipolar (2 neurites) eg retinal ganglion
  • multipolar (multiple neurites) eg LMN
64
Q

Types of synapses

A
  • axosomatic
  • axodendritic
  • axoaxonal
65
Q

Excitatory signals

A

usually glutamate, excites postsynaptic, cation selective, inotropic receptors (activation of nicotinic channels, movement of Na)

66
Q

inhibitory signals

A

usually GABA or glycine, activates anion selective, inotropic receptors, generating a hyperpolarising response

67
Q

what type of vesicles are amino acids and amines released from

A

synaptic

68
Q

what type of vesicles are peptides released from

A

secretory

69
Q

what NT activate inotropic ligand gated channels

A

glutamate, GABA, glycine, ach and 5-HT (fast transmission)

70
Q

What NT activate metabotropic g protein coupled channels

A

all except glycine (slow transmission)

71
Q

what are the different divisions of the somatosensory system

A
  1. exteroceptive division: cutaneous, registers info from the surface of the body
  2. prophoceptive division: monitors posture and movement (sensors in muscles, tendons and joints)
  3. enteroceptive division: reports on internal state of the body and closely related to autonomic function
72
Q

what is a first order neuron

A

primary sensory neuron in the PNS

cell body location in the dorsal root ganglion (limbs, trunk, post. head) or cranial ganglion (ant. head)

73
Q

what is a second order neuron

A

projection neuron in the CNS

cell body location: dorsal horn of spinal cord or brainstem nuceli

74
Q

what is a third order neuron

A

projection neuron in the CNS
cell body location: thalmic nuclei
projects to the somatosensory cortex

75
Q

what type of receptor sense touch, pressure and vibration

A

mechanoreceptors

76
Q

what types of receptors sense proprioception (forces on the joints and muscles)

A

mechanoreceptors

77
Q

what type of receptors sense temperature

A

thermoreceptors

78
Q

what types of receptors sense pain

A

mechanoreceptors, thermoreceptors and polymodal nociceptors

79
Q

low threshold receptors respond to low intensity

A

for example
low threshold mechanoreceptors mediate fine touch
low threshold thermoreceptors mediate cold–> hot touch

80
Q

high threshold receptors (nociceptors) responds to high intensity stimuli

A

for example

  • HT mechanoreceptors
  • thermal nociceptors: >45 deg and <10 deg
  • chemical nociceptors
  • polymodal nociceptors respond to at least 2 of the above
81
Q

different types of response to stimuli (3)

A
  1. slow adapting or static response: continuous info whilst nerve being stimulated, provides info on position and stretch
  2. fast adapting or dynamic response: detects change in stimuli strength, number of impulses are proportional to rate of change of stimuli
  3. V fast adapting response: responds only to fast movements eg rapid vibration
82
Q

what is the receptive field of a sensory neuron

A

the region which when stimulated produces a response in that neuron

83
Q

what is the receptive field of a sensory neuron

A

the region which when stimulated produces a response in that neuron

84
Q

what are meissner corpuscles

A

they sense touch and vibration, abundant in skin where 2 point discrimination are abundant (A beta sensory fibres)- not present on hairy skin

85
Q

What are merkel discs

A

sense touch, present on hairy skin (A beta sensory fibres)

86
Q

What are ruffini endings

A

sense pressure in the dermis and in joint capsules (A beta sensory fibres)

87
Q

what are pacinian corpuscles

A

sense pressure in the dermis and fascia (A beta sensory fibres)

88
Q

what is 2 point discrimination

A

is being able to distinguish 2 stimuli separately w/o overlap

89
Q

what is a dermatome

A

area of skin innervated by left and right dorsal roots of a spinal nerve

90
Q

organisation of laminae of rexed in the dorsal and ventral horns

A

they are defined by their cellular structure rather than by their location

91
Q

what are the 2 main tracts of the somatic sensory pathway

A
  1. dorsal column medial leminscal

2. spinothalmic

92
Q

dorsal columns consist of what 2 tracts

A

the gracile and the cuneate

93
Q

what sensory input does the gracile cover

A

T6 and below

94
Q

what sensory input does the cuneate cover

A

T6 and above

95
Q

what is the dorsal column medial leminscal pathway

A

major route by which touch and conscious proprioceptive info ascends to the cerebral cortex

96
Q

what is the capabilities of the DCML pathway

A
  1. stereognosis- ability to feel an object and recognise it (cortical function)
  2. vibration detection
  3. fine touch- two point discrimination
  4. conscious propriception- awareness of body position and movments
97
Q

what is contrast enhancement

A

when one neuron is activated it inhibits the activity of it neighbours via interneurons via lateral inhibition
it sharpens stimulus perception and is one mechanism by which info is transformed at the synapse of the DCML

98
Q

what is the trigeminothalmic pathway

A

brainstem pathways from the spinal nucleus of V (trigeminal nerve) and the principal (chief) nucleus of V to the ventral posterior medial nucleus of the thalamus

99
Q

what is the trigeminothalmic pathway

A

brainstem pathways from the spinal nucleus of V (trigeminal nerve) and the principal (chief) nucleus of V to the ventral posterior medial nucleus of the thalamus

100
Q

where is the somatosensory cortex located

A

in the post central gyrus of the parietal cortex

101
Q

What is the function of the posterior parietal cortex

A

recieves and integrates infro from the SI and other cortical areas (visual and auditory) and thalamus.

102
Q

what would occur if there was damage to the posterior parietal cortex

A

can cause agnosie, asterognosia and hemispatial neglect syndrome

103
Q

What does the somatic motor system consist of

A

upper motor neurons in the brain and lower motor neurons with soma in the brainstem and ventral horn of the spinal cord

104
Q

where do LMN receive input from

A

UMN
proprioceptors
interneurons
central terminals of dorsal root ganglion cells

105
Q

what are the different types of LMN

A
  1. alpha motor neurons which innervate the bulk of fibres within a muscle that generate force
  2. gamma motor neurons which innervate a sensory organ within the muscle (muscle spindle)
106
Q

what is it called when muscles work together

A

synergistic

107
Q

what is it called when muscles work against eachother

A

antagonistic

108
Q

what is the function of axial muscles

A

posture

109
Q

what is the function of proximal/ girdle muscles

A

mediate locomotion

110
Q

what is the function of distal muscles

A

fine manipulation

111
Q

where do axons of LMN exit the spinal cord

A

in ventral roots (each ventral root joins with a dorsal root to create a spinal pair of mixed M+S fibres) or in crainial nerves

112
Q

what is a motor unit

A

alpha motor neuron + all the skeletal muscle fibres it innervates (smallest functional component)

113
Q

what is a motor pool

A

the collection of alpha MN that innervate a single muscle

114
Q

what effects the force of a contraction

A
  1. the frequency of AP discharge of the alpha MN

2. recruitment of additional, synergistic motor units

115
Q

what effects the force of a contraction

A
  1. the frequency of AP discharge of the alpha MN

2. recruitment of additional, synergistic motor units

116
Q

where do LMN innervating the axial muscles sit in the ventral horn

A

more medially that distal muscles

117
Q

where do LMN innervating the flexors sit in the ventral horn

A

more posteriorly compared to those supplying the extensors

118
Q

what does muscle strength depend on

A
  1. firing rates of LMN
  2. the number of LMN that are simultaneously involved
  3. the coordination of the movment
119
Q

what does muscle force depend on

A

fibre size and the fibre phenotype (fast or slow fibre)

120
Q

motor unit features (small and large)

A

small: few fibres so finer movements
large: many fibres so innervate large postural muscles
small MU= small alpha MN and small soma diameter (vice versa)

121
Q

motor unit features (small and large)

A

small: few fibres so finer movements
large: many fibres so innervate large postural muscles
small MU= small alpha MN and small soma diameter (vice versa)

122
Q

What is the difference between muscle fibres

A

they differ in how quickly myosin ATPase can split ATP to provide energy for the cross bridge

123
Q

what are the different types of muscle fibres

A

Type 1- slow oxidative
Type 2a- fast oxidative
Type 2b- fast gylcolytic

124
Q

what are the different types of muscle fibres

A

Type 1- slow oxidative
Type 2a- fast oxidative
Type 2b- fast gylcolytic

125
Q

explain slow oxidative

A

-ATP derived from oxidative phosphorylation
-slow contraction and relaxation
-fatigue resistant
-red fibres (high myoglobin content)
low tension fibres, small alpha motor neurons
used in sustained movements

126
Q

explain fast oxidative

A

-ATP derived from oxidative phosphorylation
-fast conduction and relaxation
-fatigue resis
-red fibres
high tension fibres, alpha motor neurons
used in sustained locomotion (running)

127
Q

explain fast glycolytic

A

-ATP derived from glycolysis
-fast in contraction
not fatigue resis
-pale fibres, poorly vascularised
v high tension, large alpha motor neurons
used in burst power

128
Q

how are LMN recruited?

A

1st: 1
2nd: 2a
3rd: 2b
results in increasing increments towards maximal force

129
Q

how are LMN recruited?

A

1st: 1
2nd: 2a
3rd: 2b
results in increasing increments towards maximal force

130
Q

what is a myotatic relex

A

when a skeletal muscle is pulled, it pulls back. Change in length is sensed by muscle spindles

131
Q

what is a myotatic reflex

A

when a skeletal muscle is pulled, it pulls back. Change in length is sensed by muscle spindles

132
Q

what happens when muscle spindles shorten

A

activation of 1a afferent–> releases glutamate–> excitatory synaptic transmission in spinal cord–> activation of alpha MN–> contraction

133
Q

components of an intrafusal fibre

A
  • non contractile region innervated by 1a afferents

- contractile polar ends that receive efferent input from gamma MN

134
Q

classes of intrafusal fibres

A
  1. dynamic nuclear bag
  2. static nuclear bag
  3. chain fibres
135
Q

explain dynamic nuclear bag fibres

A

very sensitive to rate of change of muscle length. innervated by dynamic gamma MN

136
Q

explain static nuclear bag fibres

A

more sensitive to absolute length, innervated by static gamma MN

137
Q

explain chain fibres

A

sensitive to the absolute length, innervated by static gamma MN

138
Q

explain chain fibres

A

sensitive to the absolute length, innervated by static gamma MN

139
Q

types of afferent fibre innervation of intrafusal fibres

A
  1. Aalpha (Ia): form a primary annulospiral nerve ending around the centre of all IF
    2.Abeta (II): slowly conducting, form a flowerspray endings on all IF except dynamic bag IF
    (Ia is more sensitive to rate of change, II more sensitive to absolute length)
140
Q

when in dynamic gamma MN active

A

during rapid, unpredictable movements

141
Q

when is static gamma MN active

A

during slow, predictable movements

142
Q

what is the function of the golgi tendon organ

A

act to regulate muscle tension to protect from overload and to keep tension in optimal range

143
Q

where are golgi tendon organs located

A

at the junction of the muscle and tendon, monitors changes in muscle tension

144
Q

what is the golgi tendon organ innervated by

A

Ib afferent fibres

145
Q

what is reciprocal inhibition

A

eg when the quads contract and extend the antagonist flexor muscle (hamstrings) must relax. 1a afferent from the extensor muscle spindle make an excitatory monosynaptic contact with the alpha MN supplying the quad. Via a polysynaptic pathway involving interneurons, the 1a fibre also inhib the alphaMN supplying the hamstring

146
Q

where do the descending tracts originate

A

the cerebral cortex and brain stem

147
Q

what are 2 descending tracts

A
  1. lateral: under the control of the cerebral cortex. voluntary control of distal muscles–> discrete skilled movements
148
Q

what are 2 descending tracts

A
  1. lateral: under the control of the cerebral cortex. voluntary control of distal muscles–> discrete skilled movements
  2. ventromedial: brainstem control, important in posture and locomotion
149
Q

what are 2 kinds of lateral tracts

A
  1. corticospinal (pyramidal)

2. rubrospinal

150
Q

where are the cell bodies of the corticospinal tract found

A

in the motor cortex (BA4/6) and somatosensory area of the parietal cortex

151
Q

where are the cell bodies of the corticospinal tract found

A

in the motor cortex (BA4/6) and somatosensory area of the parietal cortex

152
Q

where are the cell bodies of the rubrospinal tract found

A

in the red nucleus, which receives input from the motor cortex and the cerebellum

153
Q

signs of lesions on the lateral tract

A
  • loss of fractionated movement(elbows, wrists etc cannot move independently)
  • slowing and impaired accuracy of voluntary movement
  • little effect on posture
154
Q

lesions on the corticospinal tract alone cause deficits as profound as a lesion on the lateral column, but recover can occur. If lesion on rubrospinal tract too- no reversal

A

the indirect rubrosponal tract can compensate for the direct corticospinal tract

155
Q

lesions on the corticospinal tract alone cause deficits as profound as a lesion on the lateral column, but recover can occur. If lesion on rubrospinal tract too- no reversal

A

the indirect rubrosponal tract can compensate for the direct corticospinal tract

156
Q

what are the ventromedial tracts

A
  1. vestibulospinal
  2. tectospinal
  3. pontine and medullary reticulospinal

NEUROLOGY (1 decks)

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