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Biomed2 > Nervous System > Flashcards

Nervous System Flashcards

1
Q

What is the nervous system

A

A network of fibres which span the body, coordinating a diverse range of voluntary & involuntary actions
Transmits signals
Rapidly responds to changes within the internal & external environment
Works alongside endocrine to maintain homeostasis

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2
Q

What are the two main divisions of the nervous system

A
  1. CNS - central consists of brain & spinal cord
  2. PNS - peripheral nerves (not in the CNS)
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3
Q

functions of the cns in sensory input

A

Detects internal & external environment changes e.g Proprioception, sensation etc
Impulse is carried by sensory neurons

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4
Q

What is proprioception

A

The awareness of body position in space
(Standing with eyes closed)

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5
Q

functions of the cns with integration impulses

A

Processes sensory info by analysing, storing & making decisions
Abundant in the brain ‘perception’
Carried by interneurons

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6
Q

functions of the ans with motor impulses

A

Produces a response to sensory info to effect change
Impulse is carried by motor neurons

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7
Q

Sympathetic vs parasympathetic nervous system

A

Sympathetic arouses the body to expend energy ‘fight or flight’
Vs
Parasympathetic controls body to maintain & conserve energy ‘rest & digest’

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8
Q

Where are the branches of the sympathetic nervous system

A

Found in the thoraco-lumbar region
In front of the ribs

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9
Q

What is the enteric ns known as

A

The ‘brain’ of the gut, containing around 100 million neurons
Functions independently but regulated via the autonomic ns
Links with the cns via sympathetic nerve fibres (vagus nerve) - involuntary
Contains all 3 neurons

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10
Q

What are the two parts of the enteric ns

A

Submucosal plexus - deals with sercetions

Myenteric plexus - gut motility

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11
Q

Where is serotonin found

A

Predominantly in digestive tract
95% serotonin found in enteric nervous system

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12
Q

What are the main two types of cells found in the nervous system

A
  1. Neurons - process & transmit information, structural & functional units, electrically excitable (make up 10% of brain)
  2. Neuroglia aka ‘glial cells’ - glue! Supporting cells that nourish, support & protect, 6 types: 4 in the cns & 2 in pns (90% brain volume)
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13
Q

What is a nerve

A

Made up of one - thousands of neurons

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14
Q

What parts do neurons contain

A

Cell body, nucleus, dendrites
Axon
Myelin sheath & nodes of Ranvier
Terminal endings

Possess electrical excitability: the ability to create a nerve impulse ‘action potential’

Amount set at birth !

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15
Q

What is a stimulus

A

Anything able to generate an action potential
The stimulus can be internal or external

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16
Q

What are bundles of cell bodies in the cns known as

A

Grey matter
Describes the appearance of tissue in the cns
In the cns known as nuclei
In the pns known as ganglia

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17
Q

What are dendrites

A

The receiving portion of the cell. They communicate with other neurons/dendrites

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18
Q

What is white matter

A

Describing axons surrounded by myelin (white coloured)

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19
Q

functions of the axons of a neuron

A

Projections that carry nerve impulses towards anothr neuron, away from the cell body

They are covered by a membrane known as the axolemma
Ends are called axon terminals
Bundles are called tracts in the cns & nerves in the pns
Slow regeneration

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20
Q

What is the biggest nerve in the body

A

The sciatic nerve
Runs down from pelvis through leg to foot and approx 1m in length

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21
Q

What are the 3 main tracts in the cns

A

2 tracts go up towards the brain are sensory tracts

1 tract that leads away from the brain is the motor tract

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22
Q

functions of the myelin sheath

A

A multi-layered lipid & protein covering around the axons
Can cover up to 100 layers
Electrically insulates the axon & increases the speed of nerve conduction

Vit B12 co-factor needed for production of myelin

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23
Q

What are the two glial cells that form myelin sheath

A
  1. Schwann cells - produce in the pns
  2. Oligodendrocytes - produce in the cns

Mostly takes place throughout childhood (by 3yrs age)

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24
Q

What are the gaps between myelin along the axon of a neuron known as

A

Nodes of Ranvier

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25
Q

Functions of neuroglia cells

A

Non-excitory, surround & bind neurons
Supply nutrients & oxygen to neurons
Destroy pathogens & remove dead neurons

Formation of new cells as can undergo division if neurons damaged
50x more prevelant than neurons

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26
Q

Functions of astrocytes in the cns

A

Most numerous & largest, bind neurons to their blood supply
Provide physical support
Make up the ‘blood brain barrier’

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27
Q

Functions of oligodendrocytes in the cns

A

Myelinate axons in the cns

Which insulates & increases speed of nerve impulses

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28
Q

Functions of microglia cells in the cns

A

Phagocytic - mobile & can multiply

Derived from monocytes that migrate to the cns before birth

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29
Q

Functions of ependymal cells in the cns

A

Produce cerebrospinal fluid (csf) which cilia circulate
Epithelial cells that line the 4 ventricles of the cerebrum & central canal of spinal cord

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30
Q

Functions of schwann cells in the pns

A

Produce myelin around axons
Which insulates & increases speed of nerve impulses
Also participates in axon regeneration

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31
Q

Functions of satellite cells in the pns

A

Provide structural support & area of substance exhchange
Surround cell bodies in the pns ganglia

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32
Q

What is the graded potential in a neuron

A

Electrical signal that travels around the cell body of a neuron

For short distance communication
Occur in dendrites & cell body
Longer duration
Has no threshold for a signal

33
Q

What is the action potential in a neuron

A

The elctrical signal that passes through the axon to another neuron

Has a threshold to be sent
Used for long distance communication
Shorter duration

34
Q

What ions help facilitate graded & action potentials

A

Sodium & potassium

35
Q

What is the resting potential of a neuron

A

The neuron has a negative charge/ions which creates a difference in electrical charge to the extracellular fluid which contains more positive ions
The separation of charges creates potential energy (approx -70millivolts)
helping to facilitate graded & action potential

At rest neurons possess an electrochemical gradient across the cell membranr

36
Q

What are ion channels

A

Transport channels for ions created by transmembrane proteins that span across neuron membranes
They open in response to a stimulus

37
Q

What is the sodium-potassium pump

A

As sodium and potassium try to move through the ion channels to equalise, the separation of charged is maintained by the pump, pumping 3 Na+ out for every 2 K+ it pumps back in
(Active trabsport ATP)

38
Q

What is the process of action potential

A

Action potential has a threshold of -55mV which stimulus must reach to create an action potential

  1. Depolarisation = Stimulus causes reversing of the membrane potential, negative 70mV potential reaches positive around 30mV. Na+ channels open with Na+ flooding into cell building positive charge
  2. Repolarisation = membrane restored to -70mV
    K+ channels open more slowly for K+ to move out of cell
39
Q

What is the refractory period of action potential

A

Period of time after repolarisation in which a nerve cannot generate another action potential because Na+ & K+ are on wrong sides of the membrane

40
Q

What is the absolute refractory period

A

Even a strong impulse cannot generate another action potential

41
Q

What is the relative refractory period

A

Larger than normal stimulus needed to generate an action potential

42
Q

What does conduction describe

A

The movement of a nerve impulse along the axon of a neurom

43
Q

How does an impulse travel along an unmyelinated axon

A

Membrane becomes depolarised in a continuous conduction away from the cell body down the axon
Depolarisation & repolarisation Occurs of each adjacent segment of cell membrane, occuring in one direction only

Eg olfactory nerve is unmyelinated hence slower reaction

44
Q

How do the nodes of ranvier cause saltatory conduction

A

At each nodes there are high concentrations of Na+ gates which causes the appearance of the conduction leaping from node to node

Saltatory conduction is much more energy efficient as less ATP is needed for the sodium-potassium pumps
Hence these nerves are vital for rapid response reactions

45
Q

Why can ice help relieve pain

A

Lower temperatures slows speed of impulses

46
Q

How do local anaesthetics work in pain relief

A

Block Na+ gates, preventing them from opening & thus stopping an action potential from being formed, inhibiting the nerve from transmitting pain messages

47
Q

What are the ends of axon terminals called

A

Synaptic end bulbs

Space between these & post-synaptic neuron is the synaptic cleft which is filled with interstitial fluid. The nerve impulse is carried across this fluid by chemical messengers aka ‘neurotransmitters’ which are stored in synaptic vesicles

48
Q

What impact does increased calcium concentration (after depolarisation) have on synapses

A

Causes exocytosis of synaptic vesicles, releasing neurotransmitters into the synsptic cleft

49
Q

What is a neurotransmitter (NT)

A

A chemical messenger that gets released from a pre-synaptic terminal, causing an effect on the post-synaptic cell
More than 100 have been identified

50
Q

What are the main categories of neurotransmitters

A
  1. Amino acids e.g glutamate, GABA (formed from glutamine)
  2. Monoamines e.g dopamine, serotonin, adrenaline
  3. Neuropeptides e.g endorphins, substance P
  4. Unique molecules e.g acetylcholine
51
Q

What 2 charectoristics can be used to distinguish neurotransmitters

A
  1. Excitory = depolarisation of the post-synaptic neuron. Opens Na+ ion channels, more positive inner membrane
  2. Inhibitory = hyperpolarisation of post-synaptic neuron. Opens K+ ion channels move out, inner membrane becoming more negative
52
Q

How can neurotransmitters be inactivated & removed for process to be sble to start again

A

Can occur by diffusion, enzymes breakdown (eg MAO for serotonin) or re-absorption

53
Q

What is glutamate (glutamic acid)

A

Major excitatory NT in the CNS
Plays a major role in memory & learning

Synthesised from glutamine

54
Q

What is GABA

A

Major inhibitory NT in the brain, produced from glutamate

1/3 brain synapses use GABA
It is essential in preventing neural over-activity

55
Q

What vitamin is needed for conversion of glutamate to GABA

A

Vitamin B6

56
Q

What is serotonin

A

Produced from amino acid ‘tryptophan’
95% produced in enteric ns

Vital role in the GIT, involved in intestinal motility (peristalsis) & epithelial cell secretion
Also plays a role in attention, sleep & pain regulation

Removed from a synapse by the enzyme MAO

57
Q

Where is dopamine located

A

In several areas of the brain includinh the substantia nigra
‘Black substance’ as appearance

58
Q

What is dopamine

A

Found in substantia nigra
Synthesised from the amino acid ‘tyrosine’
Plays a key role in movement, reward mechanisms, regulating muscle tone (deficiency = parkinsons) , cognition & emotion
Also inhibitor for prolactin
Re-uptake or removed by enzymes MAO & COMT

59
Q

What is the amino acid tyrosine used for

A

The production of thyroid hormones, adrenaline, melanin, T3 & T4, dopamine

60
Q

What are two types of monoamine nuerotransmitters

A

Adrenaline & noradrenaline
Excitatory hormones, opens Na+ channels
Found in the sympathetic nervous system, motor neurons & adrenal medulla
Re-uptake or removal by enzymes MAO & COMT

61
Q

What two enzymes break down neurotransmitters

A

MAO = found in neutons & astrocytes
Breakdowns monoamines

& COMT
Catalyses Break down of adrenaline, noradrenaline & dopamine

62
Q

Function of neuropeptides

A

Work to influence pain
Eg endorphins reduce pain (opiod analgesics)
Substance p amplifies pain

63
Q

role of acetylcholine as a neurotransmitter

A

Excitatory
Released in neuromuscular junction to cause electrical impulse to diffuse across muscle to cause contractions, also used in cognition
Deficiency = alzheimers
Botox blocks ACH

64
Q

Role of neurotransmitter nitric oxide

A

Excitatory
Vasodilation - lasts less than 10s
Formed form arginine
Used for angina, viagra enhances

65
Q

What is a dermatome

A

A distribution of skin where nerves run along

66
Q

What parts of a nerve carry the two sensory & motor neurons

A

Outer part = sensory information
Inner = motor information

67
Q

Which nerves can regenerate

A

Glial cells huge regenerative capacity

Peripheral nerves can regenerate if schwann cells & cell body are intact

68
Q

Where is the carpal tunnel

A

A narrow passageway in the anterior wrist containing tendons & the median nerve. These carry sensory info to the hand & controls movement in the hand & fingers
In carpal tunnel syndrome the median nerve becomes compressed

69
Q

What nerve is impacted in bell’s palsy

A

Facial nerve that controls facial muscles becomes inflamed or compressed
Usually due to viral infection or post surgery/injury

70
Q

Symptoms guillain-barre syndrome associated with

A

Post-infectious, autoimmune triggered, de-myelinating disease with neuritis
Antibodies cross react with lipids in myelin

Acute, ascending paralysis, progressive inflammation & demyelination of peripheral nerves, neuropathic pain jnto legs

Emergency care needed as quick progression

71
Q

Pathophysiology of ms

A

Autoimmune inflammatory disease causing demyelination of axons in CNS neurons
T-lymphocytes attack myelin antigens causing multiple areas of sclerosis along axons which disrupts conduction

Most commonly optic nerve symptoms first as higher myelinated nerve

72
Q

Where are motor neurons affected in MND

A

Progressive degeneration of motor neurons in spinal cord, motor cortex & brain stem - weakness in upper limbs
Sensory functions remain intact

73
Q

What id dementia

A

A SYNDROME
caused by a number of brain disorders which cause
Memory loss, decline in other brain cognition, difficulty performing daily activities

50% cases caused by alzheimers

74
Q

Key characteristic for dementia & alzheimers

A

Deposition of protein plaques, beta-amyloid in brain & atrophy of neurons

Plus Degeneration of cerebral cortex & reduced acetylcholine

75
Q

What areas of the brain does alzheimers affect

A

Neurodegeneration of cerebral cortex

Hippocampus is among first area affected (short term memories)
The amygdala is often affected later & is key centre for longer term memories & emotions

Additional areas become affected as disease progresses

76
Q

Risk factors for alzheimers

A

Heavy metal toxicity as degenerate blood brain barrier eg excess mercury, aluminium, copper
& oxidative damage
Vaccines containing polysorbate 80

Genetic links ApoE4 gene
Chronic inflammation including insulin resistance, leaky gut etc
Cardiovasc disease, pathogenic organisims
B vitamin deficiencies, omega3s
Hormone deficiencies

77
Q

What area of brain is affected in parkinsons

A

Loss of dopaminergic neurons in the substantia nigra - regulates movement & reward process

Accumulation of abnormal proteins “Lewy Bodies” also found within neurons

78
Q

What is bradykinesia

A

Short shuffling steps with difficulty stopping/starting
A common sign of parkinsons

79
Q

What area of brain is affected in huntingtons disease

A

Neurodegenerative disorder affecting the basal ganglia - resulting in loss of muscle co-ordination (jerky movements) with cognitive impairment & mood changes

A genetic association with defect on chromosome 4

Biomed2 (9 decks)

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