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Nervous System I Flashcards

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1
Q

Learning objectives for Nervous Tissue Lecture 1.

A

Identify and understand the role of the basic cell types of the nervous system.

  • Understand the structure of a nerve cell (neuron)
  • Explain how electrical signals are propagated
  • Understand terms such as resting membrane potential, action potential, refractory period
  • Understand the concept of summation
  • Explain why nervous transmission can occur at different speeds
  • Explain axonal transport
    This lecture is not comprehensive - basics only.
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2
Q

Content for the 6 nervous system lectures, (On the other side).

A
  1. Nervous Tissue
  2. Brain
  3. Spinal Cord & Spinal Nerves
  4. Reflexes and Pathways
  5. The Autonomic Nervous System (Fiona)
  6. Sleep
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3
Q

What does the nervous system do?

A

One part of the body’s internal coordination system
(other part = endocrine system - Fiona)

Nervous system:

  • Receives sensory information about external and internal environments
    (touch, smell, sight, hearing, taste, pain, balance, chemicals)
  • Processes that information and determines if a response is required
  • Issues commands to carry out response (mostly muscles and glands)
  • Maintains homeostasis — equilibrium in body systems (Fiona)
  • Remembering, learning & thinking, emotions
  • Involved in procreation (ANHB1101)
  • We are generally unaware of most of what the nervous system does
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4
Q

A photo showing what the nervous system looks like, (on the other side).

A
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5
Q

A photo showing the peripheral and central nervous system

A

remember SAME

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6
Q

A photo showing the basic structural organisation of the nervous system, (on the other side)

A
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7
Q

A photo showing the functional organisation of the nervous system, (on the other side)

A
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8
Q

What are the two cell types of the nervous system?

A
  1. Neurons (have extension - dendrites, axons)
  2. Glial cells = glue
    (originally only thought to hold neurons in place)

Both cell types occur in CNS & PNS

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9
Q

Info to know regarding neurons, (on the other side).

A

Neurons are:

  • excitable (respond to environmental changes = stimuli),
  • conductive (produce electrical signals that are conducted to other cells),
  • secretory (neurotransmitters secreted at end of nerve fibre to stimulate the next cell)
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10
Q

Info to know regarding glial cells, (on the other side).

A

Glial cells = Schwann cells (neurolemmocytes) PNS
only. (Other glia discussed in brain lecture.)

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11
Q

What are the basic features of dendrites and axons and give a brief definition of both.

A

Dendrites: signal input (receiving end)

Features: short, thick, unmyelinated

Axons: signal output (transmitting end)

Features: long (mm to over 1m), slender, unmyelinated or myelinated

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12
Q

A photo showing the anatomy of a neuron, (on the other side).

A
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13
Q

A photo showing the polarity of neurons, (on the other side).

A
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14
Q

Questions you should be able to answer (on the other side).

A

How are electrical signals produced and conducted by neurons?

Nerve fibres (axons) range in size from small to large.

Why?

Nerve fibres (axons) may be
myelinated or unmyelinated. Why?

What happens when the chemicals (neurotransmitters) are released at the axon terminals?

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15
Q

What are neurotransmitters secreted by?

A

Neurotransmitters secreted by neurons are made in the cell body (soma), (translation / transcription)
but have to get all the way to the end of the axon to be secreted (axon terminals - up to 1m or more away from the body).

How do these chemicals reach their destination?

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16
Q

How does a neuron generate an electrical signal?

A

Neural communication occurs because cells can produce electrical potentials and currents.
Living cells are polarised.

Neurons especially so.
+++++++
・ーーー
Polarised = different properties on different sides.

Because cells are polarised, they have electrical potential.

Electrical potential = differences between the concentration of charged particles on either
side of the cell membrane (e.g. Na+, K+, Cl, etc.).

Charge difference across a cell membrane = resting membrane potential (RMP)

In an unstimulated neuron RMP ~ -70mV (voltage = electrical potential)
Negative value = more -ve charged ions inside the membrane than on the outside.

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17
Q

How are neurons stimulated?

A

Under certain conditions electrical potential can produce an electric current = a flow of ions (charged particles) from one point to another.
Stimulation of a neuron usually starts at the Dendrite or Soma → Axon

Neurons can be stimulated by chemicals, light, heat, mechanical forces.

Stimulation can open channels in the cell membrane that allow +ve ions to flow into the cell.

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18
Q

What an important consequence of the stimulation of neurons?

A

This makes the inside of the cell less negative = voltage moves towards zero

Depolarisation = voltage shifts to a less —ve value

Opposite = Hyperpolarisation = voltage shift to a more -ve value

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19
Q

What does the stimulation of a dendrite or soma cell create?

A

Stimulation of a dendrite or soma creates a local potential which:

  • varies according to strength of stimulus (intense or prolonged),
  • gets weaker as it spreads from point of origin,
  • can be excitatory (depolarisation - voltage = less-ve) or

inhibitory (hyperpolarization - voltage = more -ve)

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20
Q

What occurs if excitatory local potentials are strong enough?

A

If excitatory local potentials are strong enough and arrive at the Trigger Zone of the Axon Hillock, an electrical signal called an action potential can initiate a current - sent to the end of the axon.

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21
Q

What is an action potential (AP)?

A

An action potential (AP) is a rapid up and down shift in voltage.

All or nothing response.

For an AP to occur, a critical voltage (threshold) must occur at the trigger zone.

Once threshold has been met the neuron “fires”
=massive depolarisation (inside the cell membrane becomes +ve very quickly)

Reversed polarity

Once the peak has been reached, the cell membrane starts to repolarise (become more -ve again).

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21
Q

What is the Trigger Zone?

A

Trigger Zone = specialised area of neuron

cell membrane that allows for a rapid change in voltage

(Fflow of ions - charged particles, e.g. Na+*)

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22
Q

A photo explaining how It’s never that simple, (on the other side).

A
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23
Q

What can Axoaxonic synapses do? (+ photo on the other side).

A

Axoaxonic synapses can also stimulate or inhibit nerve impulses at axon terminals.

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23
Q

What does the arrive of AP at the axon terminal trigger?

A

Arrival of AP at axon terminal (synaptic knob / bouton) triggers release of neurotransmitters from synaptic vesicles.

Neurotransmitter travels across synaptic cleft

Binds to neurotransmitter receptors on postsynaptic neuron

Neurotransmitter will depolarise postsynaptic membrane (make less -ve)
= local potential called a post-synaptic potential

If signal is strong enough and arrives at trigger zone of axon hillock, an AP will be generated
= nerve signal will continue in post-synaptic neuron

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24
Q

A photo detailing a post-synaptic neuron, (on the other side).

A
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25
Q

A diagram detailing the different types of synapses (on the other side).

A
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25
Q

A photo with an exam-style question (on the other side).

A
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26
Q

Explain AP nerve signals. (+ photo on the other side).

A

AP does not travel along an axon
It stimulates new AP in the cell membrane just in front
Nerve signal = chain reaction of APs

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26
Q

Why is the action potential propagation only unidirectional?

A

During AP and for a few milliseconds after it is impossible restimulate
that region to refire = refractory period (RF)

RF = Absolute refractory period (cannot trigger new AP) &
Relative refractory period (new AP possible but need +++ stimulus)
RF means AP only travels in one direction

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26
Q

The fastest conduction speeds occur in large myelinated axons. Why?

A

In larger axons membrane surface area is larger so more charge accumulates at the membrane
+ve ion inflow at nede generates action potential.

Positive charge flows rapidly along axon and depolarizes weaker with distance.

  • Depolarization of membrane at next node opens Na* channels.
    triggering new action potential.

The larger the diameter of an axon, the easier it is for ions to flow = a
faster electrical current

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26
Q

A photo with an exam-style question (on the other side)

A
27
Q

What are some non-myelinated nerve fibres?

A

Not all nerve fibres (axons) are myelinated

Nissi substance

In the PNS, unmyelinated nerve fibres are still enveloped by Schwann cells (neurolemmocytes)

Most unmyelinated axons travel through individual channels in Schwann cells.

Myelinatec
Collatera
— Musc e tiber
- Neuromusculal junction
Sometimes small fibres are bundled together in a si . channel

28
Q

What is the basic role of Schwann cells? What actually are nerves?

A

Nerves in the PNS are more vulnerable to physical damage.

Schwann cells play an important role in protection and regeneration of damaged axons.

Nerves are bundles of myelinated and unmyelinated axons that travel together

29
Q

What do Schwann cells produce?

A

Schwann cells produce the PNS myelin sheath

(CNS - brain lecture)

Spiral layer of insulation around a single nerve fibre.

Made of the cell membrane of glial cells ~ 80% lipid (good insulators)

Can be up to 100 layers

  • almost no cytoplasm between layers
    Requires many cells to myelinate a single nerve fibre.

Therefore myelin sheath is segmented.

Gaps between segments are myelin sheath gaps = node of Ranvier

Purpose = increase speed of nerve signal

30
Q

Explain Axonal transport.

A

Passage of proteins, organelles and other materials along an
axon = axonal transport

Nerve cell bodies (soma) make all of the materials required, e.g. neurotransmitters, vesicles

Two way passage:

Anterograde transport = soma to end of axon
(e.g. mitochondria, vesicles, proteins for maintenance/growth)

Retrograde transport = axon end to soma
(e.g. waste, materials for recycling)

  • Fast axonal transport - anterograde or retrograde
    (200 - 400 mm / day) - vesicles (neurotransmitters)
  • Slow axonal transport - anterograde only
    (0.2 - 0.5mm / day) - proteins (stop and go transport)

Materials travel along axonal microtubules - guide to destination.

31
Q

A photo with an exam-style question (on the other side).

A
32
Q

What does the addition of postsynaptic potentials do?

A

Summation = addition of postsynaptic potentials

Determines whether or not an action potential will be produced. For example:

Neuron 1
Stimulus 1
Stimulus 2
C
Stimulus 3
D

The resting membrane potential for Neuron 1 is -70millivolts and the threshold value is -55mV.

Three stimuli arrive at this neuron simultaneously.

  • Stimulus 1 causes depolarisation of 20mV,
  • Stimulus 2 hyperpolarises by 25mV,
  • Stimulus 3 depolarises by 10mV.

E -

Will these 3 stimuli result in an action potential? (Show your working).

Neuron 2
-55
-70
Devolanzation-
* Revolarization
hreshold
Locdi
potential
- Kesung membrane
potenual
- ACtion potential
-70mV + 20mV (depolarisation = less negative) = -50mV
-50mV - 25mV (hyperpolarisation = more negative) = -75mV
-75mv + 10mV = -65mV
© L Hyperpolarization

Conclusion: -65mV is more negative than the threshold of -55mV = no action potential

Practice: For a 4 stimulus to cause an action potential in Neuron 1 what is the minimum depolarisation or hyperpolarisation needed?

33
Q

A photo detailing depolarisation (on the other side).

A
34
Q

Learning objectives for Brain Lecture.

A

Know the basic anatomy of the brain
* Understand the development the nervous system
* Understand the origin of some common defects of nervous system development
* Know the basic anatomy of the cranium
* Understand how the brain is protected and supported within the cranium: cells, meninges (membranes) and cerebrospinal fluid
* Know some basic functions of the brain that relate to later ANHB1102 lecture topics
* Know the nerves that originate in the brain and exit as peripheral nerve (PNS) - cranial nerves

35
Q

Brain - an overview

A

Protected by cranium & 3 specialised membranes; suspended in fluid Average brain weight: 1450g in females & 1600g in males.
Highly variable - normal range: 1000-2000g.
Basic function = receive and send electrical pulses
Contains tens of billions of nerve cells; each neuron has thousands of connections ~2% of body weight; consumes 20% of the body’s energy
= body’s most expensive organ but consumes energy at a steady state (glucose)
75-80% H20; remainder = fat & protein; consistency is soft (butter; tofu)
Brain tissue has no pain receptors

35
Q

What is the basic arrangement of the brain?

A

Basic arrangement
* Forebrain (4 lobes, >80% brain volume),
* Cerebellum (little brain, ~ 10% brain volume, 50% of the brain’s neurons)
* Brainstem
Outside composed of gray matter (nerve cell bodies)
Inside composed of white matter (myelinated axons), some gray matter & spaces
Surface of the brain is highly folded:
* Gyri = convoluted ridge
* Sulci = shallow grooves
* Fissures = deep grooves
* Pattern is distinctive to individuals

35
Q

Nervous system development - neurulation

A

Neural Tube - brain & spinal cord
Neural canal - fluid filled spaces in CNS
Neural crest cells = most of the PNS
(sensory nerves, autonomic nerves,
ganglia = collection of nerve cell bodies in PNS),
Schwann cells,
two inner most membranes covering the brain & spinal cord

36
Q

neurulation photo

A
36
Q

After Neurulation - the fate of the Neural Tube photo

A
37
Q

Cells of the CNS: Neurons & Neuroglia (Neuro = nerve; glia = glue)

A

Oligodendrocytes (oligo = few; dendro = branching; cyte = cell) - myelination
Astrocytes (astro = star) - supportive framework, blood brain barrier, nourishment and maintenance
of neurons, promote formation of synapses
Microglia (micro = small) - removes dead nervous tissue, foreign matter, microorganisms
Ependymal cells (ependyma = put on over) - ciliated, circulate fluid in the cavities of brain and spinal cord derived from
neural canal

37
Q

Cells of the CNS: Neurons & Neuroglia (Neuro = nerve; glia = glue) photo

A
37
Q

more photo

A
37
Q

brain diagram photo

A
38
Q
A

Gray matter:
* outside &
* inside - forms cerebral nuclei
Nucleus = aggregation
of functionally related nerve cell bodies

39
Q
A

White matter forms tracts:
: assocaion-tedrternal capsule),
(connect different regions in same hemisphere),
* bridges - yellow
(cross from one side of cerebrum to the other - corpus callosum)

40
Q

brain cerebellum and brain stem photo

A
41
Q

photo showing the insula of the brain

A
41
Q

Protecting the brain - Bone

A
42
Q

Protecting the brain - Bone continued

A
43
Q

Protecting the brain - Meninges

A
44
Q

photo showing the brain dura

A
44
Q

The fate of the Neural Canal:
Ventricles & Cerebrospinal fluid

A

Ventricles (4) are filled with cerebrospinal fluid (CSF).
CSF
* Clear, colourless liquid
* Constantly produced and reabsorbed at the same rate
* About 500mls produced per day
* Only 100-160ml in and around brain and spinal cord at any time
Produced by specialised areas in ventricles called choroid plexuses

45
Q

The fate of the Neural Canal:
Ventricles & Cerebrospinal fluid photo

A
46
Q

Protecting the brain - CSF

A

Function:
Buoyancy - brain is suspended is CSF (neither floats nor sinks)
Effective weight = 50g
(not 1500g)
No CSF = brain damage
due to crushing
Protection - against jolts
But only up to a point.
Traumatic brain injury - car crash, contact sport
Chemical stability - regulates chemical environment, rinses metabolic waste (sleep)

46
Q

Protecting the brain - CSF photo

A
47
Q

What happens if CSF gets blocked?

A

Hydrocephalus

48
Q

Protecting the brain: blood & the brain barrier system

A

Brain = 2% adult body weight; uses 20% of oxygen and glucose
To satisfy high energetic demand brain receives 15% of blood supply
10 sec interruption to blood flow = unconsciousness
4 minutes without blood = irreversible brain damage
Damaged brain tissue can’t be replaced
Blood flow in brain = potential problems:
* Blood carries harmful agents (antibodies, macrophages, bacterial toxins) &
* Capillaries (smallest blood vessels) are leaky due to gaps between cells
Brain has 2 protective strategies:
1. Blood-brain barrier
* tight junctions between simple squamous epithelium (endothelium) lining BVs
* peri-vascular feet of astrocytes surround capillaries (initiate the formation of tight junctions)

  1. Blood-CS barrier (at choroid plexuses)
    * tight junctions between ependymal cells

What is allowed through?
H20, glucose, lipid soluble substances (e.g. 02, COz, alcohol, caffeine, nicotine, anaesthetics)
Barrier to antibiotics & cancer drugs

49
Q

Cerebral hemispheres = Cerebrum

A

Cerebral lateralisation - some differences in functions of hemispheres
* Left (usually) - breaks information into fragments and analyses in linear fashion
(language - spoken, written; analytical reasoning - science & maths)
Right (usually) - perceives information more holistically & integrated (insight, imagination, musical & artistic skill)

50
Q

Cerebral hemispheres = Cerebrum photo

A
51
Q

Limbic system = ring of cortex, medial
side of each hemisphere

A

Centre of emotion & learning
: Amgale - me diates emotional
responses to e.g. foul smell or taste, beautiful sight or sound Important in sense of fear.
* Hippocampus - memory forming centre. Transfers short term memories to long term memory (Sleep lecture)

52
Q

Limbic system = ring of cortex, medial
side of each hemisphere photo

A
53
Q

Diencephalon - Thalamus & Hypothalamus

A

Thalamus - 2 ovoid masses
superior to brainstem, between lateral and third ventricles
“Gateway” to cerebral cortex
Nearly all sensory input to cerebrum passes though thalamus (taste, some smell, hearing, balance, vision, touch, pain, pressure, heat & cold)
Thalamus process & screens out much of this information - relays only small amount to cerebral cortex, postcentral gyrus (= primary somatosensory cortex - NS lecture 4)
Allows for focus and sleep
Motor function = relays signals between superficial
(e.g. precentral gyrus = primary motor cortex) and deep
cerebral gray matter and cerebellum
(regulation of locomotion & practiced behaviours such as writing, driving a car)

54
Q

Hypothalamus

A

Sits under the thalamus (base of the 3rd ventricle)
Major control centre of the endocrine and autonomic nervous systems.
Involved in homeostatic regulation (normal functioning) of nearly all organs.
Houses 10 nuclei (aggregations of nerve cell bodies) involved in regulation of:
* Thirst
* Water balance (Urinary system lectures)
* Temperature control
* Appetite (lecture)
* Growth (lecture)
* Hormonal control of reproductive functions
* Childbirth, lactation, orgasm
* Biological clocks (Sleep regulation & circadian rhythm)
* Long term memory (hippocampus to thalamus)
* Emotional behaviour
(anger, aggression, fear, pleasure, contentment)
Pituitary gland is attached to the hypothalamus by a thin stalk
Anterior & posterior parts.
Responds to signals from hypothalamus to produce hormones.

54
Q

Brain stem

A

Midbrain, pons, medulla oblongata
White matter outside & gray matter inside (nuceli)
Most cranial nerves emerge from the brainstem (muscles and sense organs of head and neck)
Midbrain - contains cerebral aqueduct, connects forebrain (cerebrum & diencephalon) to hindbrain (Pons, cerebellum & medullar oblongata)
houses visual and auditory control centres (reflexes),
roles in fine motor control & suppression of unwanted body movement
(degeneration = Parkinson’s disease)

55
Q
A

Pons - anterior portion - white matter
* connects the 2 sides of the cerebellum
* carries sensory and motor information up and down the brainstem
Gray matter - nuclei for sleep, respiration & posture

56
Q
A

Medulla oblongata - all nerve fibres connecting brain and spinal cord pass through
Examples of neural networks (not exhaustive):
* Ascending / sensory - hearing, balance, touch, pressure, temp, pain
* Descending / motor tracts -coughing, sneezing, vomiting, gagging, sweating
~90% of nerve fibres cross over at the Pyramidal Decussation (why???)
Nuclei influence rate and force of heart beat, blood pressure, rhythm and
depth of breathing (cardiovascular & respiratory system lectures)

56
Q
A

Gray matter of the brainstem forms the Reticular Formation

  • Somatic motor control
  • Cardiovascular control
  • Pain modulation
  • Sleep & consciousness
  • Habituation
57
Q

Cerebellum

A

2 hemispheres; 10% brain mass; 60% of the surface area of cerebrum;
>50% brain’s neurons
Gray matter outside; white matter & gray (nuclei) inside
Cerebellum connects directly with Medulla oblongata, Pons & Midbrain Extensive input & output from spinal cord & cerebral hemispheres

57
Q

Cerebellum function

A

Functions:
* Monitors muscle contractions
* Aids in motor coordination (fluidity)
* Timekeeper - judge interval between 2 stimuli, prediction of where moving object will be in next second
* Compensates for head movements to keep eyes fixed on an object
* Sensory, linguistic, hearing & emotional functions

58
Q

cranial nerves

A

There are 12 (don’t need to learn all)
Most originate from the brain stem (2 exceptions, e.g. olfactory nerve)
Exit the skull through foramina (holes) - form part of the peripheral nervous system
Almost all innervate muscles and sense organs located in the head and neck
Generally classified as
* Sensory (e.g. olfactory, optic)
* Motor (e.g. oculomotor)
* Mixed (motor and sensory e.g. facial, glossopharyngeal, vagus)
Motor nerve fibres can be somatic (skeletal muscle) or autonomic (cardiac & smooth muscle & glands)
Names have meaning
- outlined in Nervous System 1 Tutorial chapter
- review before coming to tutorial.

59
Q

photo showing a exam question

A
59
Q

Which cranial nerves do you need to know?

A

CN 1 Olfactory Nerve
CN 2 Optic Nerve
(Only olfactory and optic = truly sensory)
CN 3 Oculomotor Nerve
(Motor contain sensory fibres related
to muscle function = proprioception)
CN 7 Facial Nerve
CN 9 Glossopharyngeal Nerve
(Mixed - sensory functions unrelated to motor functions CN 9 & 10 - Autonomic NS lecture)
CN 10 Vagus Nerve

59
Q

photo showing another learning challenge

A

Human Bio II Flashcards (17 decks)

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