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BRS > Cells of the nervous system > Flashcards

Cells of the nervous system Flashcards

1
Q

What makes up the CNS?

A

Two central hemispheres Brainstem Cerebellum Spinal Cord

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2
Q

What makes up the PNS?

A

Nerve fibres originating from the CNS

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3
Q

What are the functions of the 4 regions of the brain?

A

Frontal: responsible for executive functions e.g. personality

Parietal: contains sensory cortex

Temporal: contains structures such as hippocampus (short term memory), amygdala (behaviour) and Wernicke’s area (auditory perception and speech)

Occipital: processing of visual info

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4
Q

What is the brainstem?

A

Consists of midbrain, pons and medulla in descending order

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5
Q

Where is the cerebellum located and what is its role?

A

Located towards the dorsal region of the CNS and is attached to brainstem

Has important roles in mater coordination, balance and posture

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6
Q

What is a unipolar cells?

A

Has a cell body and a single axon

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7
Q

What is a pseudo-unipolar cell?

A

Has a cell body and a single projection

Single projection is able to fork into two different branches so forms 2 projections

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8
Q

What is a bipolar cell?

A

Has cell body and 2 projections

One projection is an axon, the other is a dendrite

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9
Q

What is a multipolar cell?

A

Numerous projections rom cell body

Only 1 projection is an axon, rest are dendrites

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10
Q

What are the types of multipolar cells?

A

Pyramidal cell: pyramid shaped cell body

Purkinje cell: GABA neurones found in the cerebellum

Golgi cells: GABA neurones found in cerebellum

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11
Q

What are neurones?

A

Excitable cells of the CNS- have ability to change their resting membrane potential

Non-dividing cells

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12
Q

What are common features of a neurone?

A

Have soma (cell body/ perikaryon ): contains nucleus and ribosomes and neurofilaments which provide structure and transport

Have a long process (nerve fibre/ axon) which originates from soma at axon hillock: can branch off into collaterals, usually covered in myelin

Has dendrites: highly branched cell body, not covered in myelin, receives signal from other neurones

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13
Q

What are astrocytes?

A

Most abundant cell type in brain

Function as structural cells and play important role in cell repair, synapse formation, neural motivation and plasticity

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14
Q

What are oligodendrocytes and Schwann cells?

A

Oligodendrocytes are myelin producing cells of CNS

Schwann cells perform the same function but in the PNS

Each oligodendrocyte cell body sends out many projections that form internodes of myelin covering the axons of neurones

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15
Q

Whats the difference between a oligodendrocyte and Schwann cell?

A

Oligodendrocyte can myelinate many axons

Schwann cell can only myelinate a single axon segment

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16
Q

What are microglia?

A

Microglial cells are specialised cells similar to macrophages and perform immune function in the CNS

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17
Q

What are ependyma?

A

Epithelial cells that line the fluid filled vesicles regulating the production and movement of CSF

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18
Q

What is an ion flux?

A

The number of molecules that move across a particular area per unit of time (units: molecules . m^-2 . s^-1

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19
Q

How do we measure membrane potential?

A

We can put an electrode outside a cell and one inside a cell

20
Q

What is the Nernst equation?

A

E= (RT/ZF) ln (X2/X1)

Where

E= reduction potential

R= gas constant

T= temp. (k)

Z= charge of ion

F= Faraday’s number

X1= extracellular ion conc.

X2= intracellular ion conc.

21
Q

What is the Goldman- Hodgkin- Kotz (GHK) equation?

A

Describes the membrane potential more accurately

Subscript i or o indicates inside or outside of cell

P is permeability or channel open probably (0 to 1)

22
Q

What forms a potential difference?

A

Relative concentrations of ions gives the cell membrane an electromotive force (emf) or a potential difference between inside and outside of cell

23
Q

What is the zero reference point?

A

Outside of cell is zero reference point and has voltage of 0mV

Inside of cell has negative membrane potential of around -70mV: this is the resting membrane potential

24
Q

What are the 4 major physiological ions?

A

Potassium (higher intracellular conc.)

Sodium (higher extracellular conc.)

Calcium (higher extracellular conc. - high conc. gradient due to big difference between intracellular and extracellular conc.)

Chloride (higher extracellular conc.)

25
Q

What is an overshoot?

A

Membrane potential becomes more positive (after depolarisation)

26
Q

What is hyperpolarisation?

A

membrane potential becomes more negative (after repolarisation)

27
Q

What is depolarisation?

A

Membrane potential becomes more positive

28
Q

How is an action potential generated?

A

When cell depolarisation reaches threshold, an AP is generated

Theres a brief depolarisation spike in membrane potential before returning to resting membrane potential

The action potential is transmitted along the membrane and axon by cable transmission

29
Q

How do Na+ and K+ generate a neuronal action potential?

A

At RMP there’s a high conc. of Na+ outside the celland high conc. of K+ inside cell

In normal conditions voltage gated sdoum channels (VGSCs) and voltage gated potassium channels (VGKCs) are closed

When theres a change in membrane potential theres a change in ionic channel configuration that allows channels to open

30
Q

How is depolarisation borought about?

A

VGSCs open meaning theres an Na+ influx, this causes futher depolarisation

VGSCs have faster kinetics than VGKCs- open and close faster

31
Q

How is membrane repolarisation brought about?

A

VGKCs open more slowly

This causes an efflux of K+ - they move out of the cell

This causes a decrease in membrane potential so auses repolarisation

32
Q

What restores the balance of Na+ and K+?

A

Na+/K+/ATPase pump

  1. Resting configuration: Na+ enters vestibule upon phosphorylation and is transported into cell
  2. Active configuration: Na+ is removed from cell and K+ enters vestibule- works against Na+ conc. gradient
  3. Pump returns to resting configuration and K+ is transported back into cell
33
Q

What is saltatory conduction?

A

AP is spread along the axon by cable transmission

Myelin prevents AP spreading because it has high resistance and low capacitance

This means AP must jump between gaps in myelin known as nodes of ranvier

However AP is unable to jump across gap at axon terminal- this is where electrical signal turns to chemical signal

34
Q

Label the following

A
35
Q

What is a graded potential?

A

Change in membrane potential is granded in response to strength of stimulus

Graded potentials initiate or prevent action potentials

These graded potentials decay from the stimulus site

Graded potentials can be a depolarisation or hyperpolorisation

36
Q

Why do graded potential decay away from the stimulus site?

A

The charge leaks from the axon and size of the potential charge decreases along the axon

37
Q

How does a graded potential lead to an action potential?

A

When graded potential reaches a threshold, an AP is achieved

This results in an “all-or-nothing” event- once started it can’t be stopped

38
Q

What is the absolute refractory period?

A

New AP cannot be triggered even with a very strong stimulus

This limits the number of APs that a given nerve cell can produce per unit time

Na channels are inactive

39
Q

What is the relative refractory period?

A

Some Na+ channels have recovered and open

Stonger than noral stimulus is needed to trigger an AP

40
Q

What is a synapse?

A

Small gap between two neurones

Synapse has a pre synaptic terminal and post synaptic termial- these are seperated by a space known as the synaptic cleft

Electrical signal is converted into a chemical signal to cross the synaptic cleft

41
Q

What happens to the AP when it arrives to the axon terminal?

A

AP encounters a different species of ion channels- VGCCs (calcium)

It allows calcium ions in or out of the cell

High Ca2+ gradient promotes influx down its conc. gradient

42
Q

How are neurotransmitters released from vesicles?

A

AP opens VGCCs at presynaptic terminal- influx of Ca2+ into cell

Ca2+ binds to vesible containing neurotransmitter (NT)

Vesical binds to presynaptic membrane and leaves by exocytosis

43
Q

How are post synaptic receptors activated?

A

NT binds to receptors on post-synaptic membrane

This depolarises the post synaptic cell and generates another AP

44
Q

What happens to the NT after it has bound to the post synaptic receptors?

A

Its removed fairly quickly

This is done by enzymes e.g. cholinesterase which binds to ACh and reaks it down allowing reuptale by pre-synaptic terminal

In some cases enzyme isnt needed and NT can be taken dorectly by pre synaptic terminal

45
Q

What effects conduction velocity?

A

Axon diameter and myelination - (small diameter non-myelinated axon 1 m/s VS large diameter, melinated axon 120 m/s)

Some diseases e.g. MS, colds, anasthesia and drugs can reduce conduction velocity

BRS (60 decks)

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