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Brain and Behaviour > Cells of the Nervous system > Flashcards

Cells of the Nervous system Flashcards

1
Q

What are the components of a neuron?

A

 Soma (cell body)
 Dendrites attached to Soma (receives messages from different neurons)
 Axon (inside myelin sheath)
 Myelin is a lipid layer that insulates axon
 Axons branches into terminal buttons which transfer information to different neurones

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2
Q

What do sensory neurones detect?

A

Changes in the external and internal environment

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3
Q

What do motor neurones do?

A

control muscle contraction and also gland secretion (CNS and PNS)

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4
Q

What are interneurons?

A

lie entirely within CNS and are involved in cognition (i.e. perceiving, learning)

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5
Q

What are projection neurons?

A

They connect distal regions of the brain and have long axons

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6
Q

What is a multipolar neuron?

A

one axon and many dendrites attached to its soma

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7
Q

What are bipolar neurones?

A

one axon and one dendrite attached to its soma

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8
Q

What are unipolar neurones?

A

neurons with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system

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9
Q

What cells do we have in the cerebellum?

A

Purkingjie cells

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10
Q

Who came up with a special stain that can be applied to the nervous system?

A

Golgi

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11
Q

Who used Golgi’s stain and discovered neurones?

A

Ramon y Cajal

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12
Q

What do glial cells do?

A

‘glue’ the nervous system together

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13
Q

What do microglia do?

A

Control the immune response of the brain

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14
Q

What are astrocytes and what do they do?

A
  • Star cells
  • Provide physical support to neurons
  • Provide nourishment in the form of broken down glucose
  • when neurons die they clean up debris (phagocytosis) and form scar tissue
  • Control chemical composition of fluid surrounding neurons
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15
Q

What do Oligodendrocytes do?

A
  • support axons and produce the myelin sheath

- wraps around many different axons in the CNS

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16
Q

What do Schwann cells do?

A

Wrap around a single PNS axon

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17
Q

What is the blood-brain barrier?

A

The brain has a semipermeable barrier between the CNS and circulatory system, which helps to regulate the flow of nutrient rich fluid into the brain (much smaller gaps than the capillaries in the body system)

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18
Q

What is the area postrema?

A

a region of the medulla where the blood brain barrier is weak. This allows toxins in the blood to stimulate this area, this initiates vomiting – poison removed from body

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19
Q

What is the membrane potential?

A

electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell
- Stored up source of electrical energy

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20
Q

What is the resting potential?

A

membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials, normally about -70 mV

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21
Q

What is key in keeping the resting membrane potential?

A

The ions of either side of the cell membrane and diffusion and electrostatic pressure

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22
Q

What are neurons filled with and what do they bathe in?

A

Neurons bathe in fluid called extracellular fluid and are filled with intracellular fluid.

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23
Q

What happens when a positive charge is applied to the resting membrane?

A

depolarisation - reduction of negative charge (toward zero) of the membrane potential)

24
Q

What is an action potential and when does it occur?

A
  • Occurs when depolarisation reaches the threshold of excitation
  • Brief electrical impulse that provides the basis of conduction of information along an axon
25
Q

What is the threshold of excitation?

A

the value of the membrane potential that must be reached to produce an action potential

26
Q

Which balance of two forces is the membrane potential made up of and what are these two forces?

A
  • Diffusion: movement of molecules from areas of high concentration to areas of low concentration
  • Electrostatic pressure – when substances dissolve in water, they split into 2 parts with opposing electrical charges, e.g. Na+ and Cl- ions
  • Attraction of oppositely charges ion (+-) and repulsion of similarly charged ions (++;–) is exerted by electrostatic pressure
27
Q

What is the composition of the intracellular fluid?

A

 Negatively charged intracellular fluid due to large anions
 Large concentration of K+ ions on inside of cell (force of diffusion and electrostatic pressure balance each-other and K+ stays inside the cell)

28
Q

What is the composition of extracellular fluid?

A

 Positively charged
 Low concentration of K+ ions outside the cell
 Cl- large concentration outside cell (force of diffusion and electrostatic pressure balance each-other and Cl- stays outside of the cell
 Na+ found in high concentrations outside cell but both electrostatic pressure and force of diffusion push sodium into cell

29
Q

What is the sodium potassium pump and what does it mean?

A
  • Pumps 3Na+ ions out and brings in 2 K+ ions in
  • Active mechanism
  • That is why many Na+ ions are found outside the cell
30
Q

What do action potentials results from?

A

Movement of ions across a membrane

31
Q

What are ion channels and voltage gated ion channels?

A
  • Proteins that open and close, thus allowing ions to pass through the cell wall
  • Voltage gated ion channels are opened and closed based on charge that arrives
32
Q

What happens during an action potential?

A
  • Threshold of excitation reached
  • Na+ channels open, Na+ begins to enter cell
  • Membrane potential becomes more positive (from -70 to +40)
  • K+ channels open after slight delay, K+ begins to leave cell
  • Then Na+ channels become refractory (at +40mV), no more Na+ enters cell
  • K+ continues to leave cell, causes membrane potential to return to resting level
  • K+ channels close, Na+ channels reset
  • The membrane potential overshoots its resting -70mV and hyperpolarisation occurs as a results of extra K+ ions outside the axon. Extra K+ outside diffuses away and resting membrane potential is restored
33
Q

What is the all-or-none-law?

A

once the action potential begins, it proceeds without decrement to the terminal buttons (it either occurs or it doesn’t)

34
Q

How can the speed of conduction be calculated?

A

from the delay between stimulus and action potential

35
Q

What is the rate law?

A

variations in the intensity of a stimulus are represented by variations in the rate at which that axon fires
- Rate of firing causes stronger muscle contraction

36
Q

What is the all or none law supplemented by?

A

the rate law

37
Q

What is Saltatory conduction?

A

 Conduction of action potentials by myelinated axons
 The action potential appears to jump from one node of Ranvier to the next (myelin sheath doesn’t allow it to be in contact with extracellular fluid)

38
Q

What are the advantages of Saltatory conduction?

A

 Economy: less energy used by the Na-K pump (located only at the Nodes of Ranvier)
 Speed: conduction must faster in a myelinated axon

39
Q

What type of conduction do unmyelinated axons exhibit?

A

continuous conduction

40
Q

What do terminal buttons make connections to?

A

adjacent dendrites of different neurons

41
Q

What is a synapse?

A

the junction between 2 neurons – it is the primary means of communication between 2 cells

42
Q

What is the synaptic cleft?

A

a very narrow gap of about 20 nm between neurons

43
Q

What are nerve impulses carried across the synapse by?

A

neurotransmitters

44
Q

What happens with transmission of an action potential across the synapse?

A
  • Action potential causes synaptic vesicles filled with neurotransmitters to fuse with presynaptic membrane
  • Neurotransmitters released into synaptic cleft
  • Postsynaptic neurons receive neurotransmitter
45
Q

Where is a neurotransmitter made and stored?

A

made by the pre-synaptic neuron and is stored in synaptic vesicles at the end of the axon

46
Q

What does the membrane of the post synaptic neuron have?

A

chemical-gated ion channels called neuroreceptors. These have specific binding sites for neurotransmitters. The chemical messenger fits the binding site like a lock and key

47
Q

How does the direct opening of an ion channel work?

A
  • Ionotropic receptor
  • Neurotransmitter binds to neuroreceptor on the outside of the cell
  • Opens the ion channel from the outside
48
Q

How does the indirect opening of an ion channel work?

A
  • Metabotropic receptor
  • Neurotransmitter binds to receptor
  • Receptor starts a chain reaction which opens the ion channel from the inside
49
Q

What happens with reuptake?

A
  • Active reuptake: another protein transporter sucks up all the neurotransmitter once the ion channels are open
  • Enzymes destroy molecules of neurotransmitter because:
  • Exposure of the neurotransmitter to the receptors needs to be brief
50
Q

What are excitatory post synaptic potentials? (EPSP)

A

excitatory depolarization of the postsynaptic membrane

51
Q

What are inhibitory postsynaptic potentials (IPSPs)?

A

inhibitory hyperpolarisation of the post synaptic membrane

52
Q

What is the nature of the postsynaptic potential determined by?

A

Which ion channels the post synaptic receptors open

53
Q

Which ion channels will cause EPSPs and which will cause IPSPs?

A
  • Sodium causes a EPSP as the influx of positive charge causes depolarisation
  • Potassium and Chloride channels cause IPSPs because
     potassium is positive and leaves the cell making the cell more negative
     chloride is negative and brings negative charge into the cell causing hyperpolarisation
54
Q

What is neuronal integration?

A

the process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron

55
Q

What happens with activity of excitatory and inhibitory synapses?

A
  • Activity of excitatory synapses produces ESPs in postsynaptic neuron: the axon hillock reaches threshold of excitation; action potential is triggered in axon
  • Activity of inhibitory synapses produces IPSPs in postsynaptic neuron
  • ISPs counteract EPSPs; action potential is not triggered in axon

Brain and Behaviour (11 decks)

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