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Biological Sciences > Lecture 7 - Part 1 - Structure of the Nervous System > Flashcards

Lecture 7 - Part 1 - Structure of the Nervous System Flashcards

1
Q

What are the two original theories for composition of nervous system

A

Reticular theory

Cell theory

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2
Q

What’s the reticular theory

A

Composed of a network of structures - joined together tubes ( continuous ) - vascular - blood vessels
- reticulum = a fine network of net like structure

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3
Q

What’s the cell theory

A

Composed of discrete cells - everything else in body

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4
Q

What’s nervous system made of

A

Millions of individual cells called neurons ( nerve cells )

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5
Q

Role of nervous system

A

Sending (electrical) signals very rapidly throughout the body
Transmits info quickly into little electrical signals

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6
Q

Nervous system organisation ( reflex arc )

A

Stimulus - Receptor - Sensory neuron ( afferent ) - CNS - Motor neuron ( efferent ) - Effector - Response

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7
Q

What is the effector

A

Muscle or Gland

Muscle contracts

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8
Q

What is transduction

A

Converting stimulus into electrical signals ( receptor does this )

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9
Q

What is part of PNS

A
  • Sensory neuron

- Motor neuron

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10
Q

What is part of CNS

A
  • Brain

- Spinal cord

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11
Q

Summary of reflex arc

A

Stimulus - electrical signal ( transduction ) - done by receptor
Receptor sends signals to sensory nervous system via sensory neurones
CNS interprets electrical signal - another electrical signal along motor neuron = response ( muscle contracts )

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12
Q

Example of reflex arc

A

Myotactic reflex - knee jerk reflex

Modified muscle cell - wrapped with sensory nerves

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13
Q

What is stimulus in knee jerk reflex

A

Hammer in knee

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14
Q

What is response in knee jerk reflex

A

Leg in air

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15
Q

How does knee jerk reflex work

A

Stretching a muscle (by hitting the patellar tendon with a hammer), activates a muscle stretch receptor (the muscle spindle) and cause nervous activity in a sensory motor neuron
The sensory neuron synapses with an alpha motor neuron in the spinal cord, which causes the quadriceps muscle to contract (& causing the leg to ‘jerk’.
(At the same time the opposing muscle is inhibited)

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16
Q

What are the 3 types of muscle

A
  • Skeletal
  • Cardiac
  • Smooth
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17
Q

Skeletal muscle

A
  • Attached to skeleton
  • Striated
  • Forceful
  • Voluntary
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18
Q

Cardiac muscle

A
  • Found in heart
  • Striated
  • Forceful
  • Involuntary
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19
Q

Smooth muscle

A
  • Hollow organs/glands
  • Unstriated
  • Weak
  • Involuntary
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20
Q

Somatic nervous system

A

Innervates skeletal muscle

Voulantary

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21
Q

Autonomic nervous system

A

Innervates smooth and cardiac muscle, + glands

Invoulantary

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22
Q

What is Autonomic system divided into

A
  • Symphathetic

- Parasympathetic

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23
Q

Symphathetic nervous system

A
  • Flight, fright + fight
  • Increases heart rate
  • Inhibits bladder contraction
  • Dilates pupil
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24
Q

Parasympathetic nervous system

A
  • Resting and digesting
  • Decreases heart rate
  • Contracts bladder
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25
Q

How many pairs of nerves connect CNS to rest of body

A

43

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26
Q

How many cranial nerves exit brain

A

12

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27
Q

How many exit at various levels of spinal cord

A

31

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28
Q

What are the cells of the nervous system

A

NEURONS or NERVE CELLS
Generate & transmit electrical signals
SUPPORTING CELLS
Supporting roles in Nerve Cell functions

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29
Q

Nerve cells and other cells comparison

A

Nerve cells are similar to other cells - plasma membrane, nucleus, organelles, obey same rules BUT…
Function is unique - transmit and store info

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30
Q

What is structure of neurone

A
  • Several dendrites (input to the cell)
  • Cell body (soma)
  • A long axon
  • A synaptic region (axon terminals) – (output)
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31
Q

How are neurones polar strcutures

A

Information comes one end and goes out other end - 2 ends to different things ( left and right )

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32
Q

How many directions is information flow and where

A
  • One direction
  • Dendrites to synapses
  • A single neuron can receive input from many others
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33
Q

What do neurons form

A

Complex networks - when neurons connect together information comes into dendrites - axon - leaves synapse into 2nd neuron

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34
Q

Dendrites

A
  • Receive incoming electrical information
  • Their branching increases surface area = gather info from lots of areas
    -Spines on dendrites increase surface area
    further
  • Most input is on to dendrites (axondendritic), some incoming neurons connect to the cell body (axosomatic) or even the axon (axoaxonic)
  • Each cell connecting to dendrite will produce electrical signal - conducted along dendrites and cell body
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35
Q

What is the cell body also called

A

Soma

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36
Q

Role of cell body ( soma )

A
  • ‘Sums’ electrical signals coming from dendrites
  • Contains the usual organelles including;
    prominent nucleus and nucleolus, rough ER (known as Nissl substance)
  • Makes proteins
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37
Q

What is the rough ER called in cell body

A

Nissl substance

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38
Q

What does Nissl substance look like under microscope

A

Grainy

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39
Q

Role of Axon

A
  • Takes electrical signals away from the cell body
  • Movement of substances via ‘axonal transport’ and
    ‘axoplasmic flow’
  • Transfers electrical signal along neurone
  • Gets proteins to every part of cell
40
Q

Size of axon

A

Varies in length from «1 mm to >1 m

41
Q

Structure of axon

A
  • Usually unbranched, but may have collaterals
  • The axoplasm is surrounded by a ‘normal’ phospholipid bilayer membrane embedded with proteins (which act as ion channels)
  • Joins soma at ‘axon hillock’ (where signal is generated)
  • Ends in synaptic terminals (where it contacts other neurons)
  • Possession of a myelin sheath
  • Contains microfilaments (actin), microtubules & intermediate filaments
42
Q

What is Axon Hillock

A

Where signal is generated
Where axon and soma join
Receive electrical signals from dendrites - added together at axon hillic = bigger electrical signals - travels along axon

43
Q

What is myelin sheath

A

Fatty substance wrapped around

44
Q

How are substances transported within axon

A
  • Axoplasmic flow

- Axonal transport

45
Q

What is axoplasmic flow

A
  • Anterograde transport from cell body to synapse. -Involves intermediate filaments - transports proteins
  • Slow (1-5 mm day)
  • Repairs and maintains cells
46
Q

What are axon terminals

A

Where axons terminate in series of synapses

Where electrical signals are transferred to other neurons or muscles.

47
Q

How are electrical signals transferred to other neurons

A

Through the release of a chemical (neurotransmitter) - bought by axoplasmic flow + axonal transport to cell body

48
Q

What do axon terminals contain

A

Vesicles - lots of tiny bags which contain proteins/chemicals - release neurotransmitter

49
Q

How do neurons talk to each other

A

By releasing chemicals

50
Q

What are neuroglial cells

A

Supporting cells - nerve glue

51
Q

What are the neuroglial cells in CNS

A

Oligodendrocytes
Microglia
Ependymal cells
Astrocytes

52
Q

What are the neuroglial cells in PNS

A

Schwann cells

Satellite cells

53
Q

What are Schwann cells

A
  • Produce myelin in the PNS (in the process of ‘myelinisation’)
  • The Schwann cell membrane repeatedly wraps itself around an axon
  • A single Schwann cell provides myelin for only one neuron but a single neuron receives its myelin from several Schwann cells
54
Q

What is the membrane of Schwann cells and what does it do

A

Myelin

Surrounds axon with hundreds of layers

55
Q

What are nodes of ranvier

A

Gaps in the myelin sheath formed between the bits of myelin provided by individual Schwann cells

56
Q

Where is the electrical signal generated

A

Nodes of ranvier

57
Q

Role of nodes on ranvier

A
  • Regenerates electrical signal

- Insulator - makes sure electrical signals can be transported along axon

58
Q

What happens if there’s no myelin

A

Nervous system slows down/ loses control = doesn’t conduct electrical activity

59
Q

Some small axons

A

Remain umyelinated and rather than being wrapped in Schwann cell cytoplasm, simply lie in a groove on the surface of such a cell.

60
Q

Oligodendrocytes

A
  • Produce myelin in the CNS
  • A single oligodendrocyte provides myelin for only several neurons
  • Wrap around neurons in CNS
61
Q

Astrocytes

A
  • Star-shaped with ‘feet’ covering blood vessels
  • Important for blood:brain barrier
  • Also have a role in damage repair (proliferate & form scar tissue) - protects brain
  • Store nutrients (glucose)
  • Isolate synapses = mop up neurotransmitters
  • Disease: main source of CNS tumours = Gliomas
62
Q

What is main role of astrocytes

A

Blood brain barrier - controls what goes in/out

63
Q

Replication of astrocytes

A

Causes cancer/ tumour - does not come from nerve cells, comes from astrocytes - as nerve cells in CNS don’t replicate

64
Q

Can neurone in brain regenerate

A

No

65
Q

What is main source of CNS tumours

A

Gliomas

66
Q

Ependymal cells

A
  • Line ventricles of brain and central canal of spinal cord
  • Involved in secretion of CSF
  • Surface cells of ventricles, brain = fluid filled space
67
Q

Microglia

A
  • Phagocytic cell
  • Normally ‘dormant’, but involved in CNS injury/inflammation
  • Move to damage site
  • Phagocytose debris & pathogens
  • Release cytokines to attract other immune cells, e.g. lymphocytes
68
Q

Main role of microglia

A

Hoover of brain - eating u and digesting things around brain that need to be destroyed

69
Q

What are the 4 basic morphological types of nerve cell

A
  • Anaxonic
  • Unipolar
  • Bipolar
  • Multipolar
70
Q

Anaxonic nerve cell

A

(no axon - rare) – e.g. retinal amacrine cell

71
Q

Unipolar nerve cell

A

only one neuron emanating from the cell body = one process coming out of cell body
e.g. some sensory neurons

72
Q

Bipolar nerve cell

A

one dendritic process and one axon leave the cell body) - e.g. retina

73
Q

Multipolar nerve cell

A

(many neurites emanating from the cell body)

- e.g. most CNS neurons (e.g. the typical neuron)

74
Q

Which nerve cell is retina example of

A

Bipolar nerve cell

75
Q

What is organisation of a nerve

A
  • A nerve is a collection of neurons
  • It can contain both afferent and efferent fibres
  • Individual neurons are separated by a connective tissue sheath –endoneurium
  • The perinurium splits nerves into fascicles
  • The epineurium forms an outer coat
76
Q

What forms outer coat in nerve

A

Epineurium

77
Q

What does perinurium do

A

Splits nerves into fascicles

78
Q

What is meant by reticulum

A

A fine network of net like structure

79
Q

What is a nerve

A

Collection of neurons

80
Q

What happens in a Myotactic reflex

A

Skeletal muscle contracts

81
Q

How many neurons or nerve cells

A

10^11

82
Q

How many supporting cells ( neuroglia )

A

10^12

83
Q

What is function of neurons/ nerve cells

A

Generate and transmit electrical signals

84
Q

What is function of supporting cells ( neuroglia )

A

Supporting roles in nerve cell functions

85
Q

What do dendrites connect to

A

Cell body

86
Q

What contains the nucleus

A

Cell body ( soma )

87
Q

Where are electrical signals from dendrites added together

A

Axon Hilic

88
Q

How many directions is axoplasmic flow

A

One - cell body to synapse

89
Q

How many directions is axonal flow

A

Both - synapse to cell body and back

90
Q

What is function of axonal flow

A

Relase waste products

91
Q

What is function of axoplasmic flow

A
  • Repair and maintain cell

- Transport proteins

92
Q

What do axons terminate into

A

Synapses ( axon terminals )

93
Q

What is final area of neurone

A

Axon terminal

94
Q

How is a chemical released

A

Axoplasmic flow and axonal transport to cell body

95
Q

What is stuck on side on Shcwann Cell

A

Remaining nucleus of Schwann Cell

96
Q

What happens if neuron in brain dies

A

It stays dead forever - cannot regenerate

97
Q

What makes the myelin

A

Oligodendrocytes

Biological Sciences (27 decks)

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