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DEN1DSA > Nervous system > Flashcards

Nervous system Flashcards

1
Q

structure of NS

A

CNS
- brain + spinal cord
PNS
- spinal + cranial nerves

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2
Q

function of NS

A

mainatain homeostasis
receive, coordinate and respond

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3
Q

divisions of the NS

A
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4
Q

function of PNS

A

Caries sensory information from body to CNS vis sensory nerves

Carries motor information from CNS to body via motor nerves

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5
Q

structure of PNS

A

cranial and spinal nerves

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6
Q

Autonomic NS

A

controls involuntary actions

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7
Q

Somatic NS

A

Controls voluntary skeletal movements

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8
Q

Sympathetic NS

A

prepares for flight or fight responses

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9
Q

Parasympathetic NS

A

prepares the body for rest and repair by returning body to homeostasis after threat has been subsided

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10
Q

what are glial cells?

A
  • provide structural support, insulation, and nutrients for neurons
  • non conductive –> do not transmit electrical impulses
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11
Q

examples of glial cells

A
  • Schwann cells
  • Oligodendrocytes
  • Microglial cells
  • Ependymal cells
  • Astrocytes
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12
Q

neuron

A

nerve cell that transmits electrical impulse signals for communication

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13
Q

properties of neurons

A
  • excitability
  • conductivity
  • synaptic transmission
  • plasticity
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14
Q

excitablility

A

respond to stimuli and generate action potentials in response to stimuli

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15
Q

conductivity

A

transmit electrical impulse over long distances (dendrite —> axon terminal)

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16
Q

synaptic transmission

A

neurotransmitters relay signals from one neuron to another

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17
Q

plasticity

A

ability to change and adapt in response to experience, learning and memory formation

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18
Q

What is A?

A

Dendrite

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19
Q

what is B?

A

cell body

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20
Q

what is C?

A

nucleus

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21
Q

what is D?

A

Schwann cell

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22
Q

what is E?

A

myelin sheath

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23
Q

what is F?

A

node of Ranvier

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24
Q

what is G?

A

axon terminal

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25
Q

what is H?

A

axon

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26
Q

What is the function of the nucleus of a neuron?

A

To provide DNA of cell

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27
Q

What is the function of a dendrite?

A

To RECEIVE information FROM other neurons and carry information TOWARDS the cell body

28
Q

What is the function of the axon?

A

To carry information FROM the cell body TO other neurons

29
Q

What is the function of an axon terminal?

A

To stores and secretes neurotransmitters which carry chemical messages to other neurons/cells

30
Q

What is the function of the myelin sheath?

A

To insulate axon which increases the rate at which nerve impulses are conducted along the axon

31
Q

What is the function of the nodes of Ranvier?

A

Gaps in the myelin sheath that allow for depolarisation of nerve impulse

32
Q

axon hillock

A

site where the action potential is
generated

33
Q

4 stages of an action potential

A

resting, threshold, depolarisation, repolarisation

34
Q

2 types of nervous tissue

A

neurons and neuroglia

35
Q

3 types of neurons

A

sensory, motor, interneurons

36
Q

synapse

A

The connection between adjacent neurons.

37
Q

2 types of neural messages

A

within neurons: electrical (action potential)
between neurons: chemical (neurotransmitters)

38
Q

neurotransmitter

A

The chemical secreted into the gap between neurons at a synapse.

39
Q

Nerve impulse

A

The high speed signals that pass along the axons of nerve cells.

40
Q

multipolar

A
41
Q

bipolar

A
42
Q

unipolar

A
43
Q

sensory (afferent) neurons

A

conduct impulses from sensory receptors into CNS

44
Q

motor (efferent) neurons

A

conduct impulses away from the CNS to the effector organs (muscles and glands)

45
Q

interneurons

A

lie between sensory and motor neurons or other interneurons

46
Q

Resting membrane potential

A
  • neuron maintains -70mV inside the cell
  • high [K+] inside
  • high [Na+] outside
  • at rest, more permeable to K+ through leak channels
47
Q

Sodium potassium pump: process

A

(1) Initially there is a lower concentration of Na+ ions outside versus those inside the cell.

(2) Three cytoplasmic sodium (Na+) ions bind to the pump.

(3) This promotes hydrolysis of ATP into ADP, releasing energy.

(4) The Na+ / K+ pump changes shape within the membrane and releases Na+ outside of the cell.

(5) The new shape of the channel binds two potassium ions.

(6) This triggers release of phosphate and the dephosphorylated pump resumes its original shape.

(7) K+ is released inside the cell.

48
Q

Action potential

A

Rapid change in the permeability of the neuronal membrane to Na+ and K+

49
Q

Threshold initiation

A

Signals from the dendrites and cell body reach the axon hillock.

As the axon hillock depolarises, voltage-gated channels for sodium open rapidly, increasing membrane permeability to sodium.

Sodium diffuses down its concentration gradient into the cell.

If the stimulus at the axon hillock is great enough, the neuron depolarises by about 15 mV to a point called ‘threshold’ (-55 mV).

At threshold, an action potential is generated.

50
Q

Depolarisation

A

More sodium voltage-gated channels open.

This causes more sodium to flow into the cell, which in turn causes the cell to depolarise further and opens more voltage-gated sodium channels.

This positive feedback loop produces the rising phase of the action potential.

This ends with the inactivation of the Na+ voltage-gated channels and the opening of K+ voltage-gated channels.

51
Q

Repolarisation

A

Potassium diffuses out of the cell as the potassium voltage-gated channels open.

With less sodium moving into the cell and more potassium moving out of the cell, the membrane potential becomes more negative, moving back towards the resting value.

Repolarisation restores the electrical
balance.

52
Q

Hyperpolarisation

A

Excessive potassium continues to diffuse out of the cell, causing the membrane potential to become more negative than the resting membrane potential.

All the potassium channels are closed and the sodium-potassium pump redistributes the ions to their original, resting state levels.

53
Q

Absolute refractory period

A

Occurs after the generation of an action potential and sodium voltage gated channels are open:

  • Neuron cannot generate another action potential
  • All Sodium channels are inactive regardless of stimulus
  • Potassium channels are open allowing diffusion of potassium
    out of the cell
  • Can only go in the forward direction
54
Q

Relative refractory period

A

Occurs after the absolute refractory period:
- Cell can generate action potential but only if it is depolarised to a value more positive than normal threshold
- Can occur since some sodium channels are still inactive but others have reset and returned to their resting state
- Some potassium channels are still open

55
Q

How does the central nervous system tell the difference between a weak stimulus and a strong one?

How does the central nervous system control different strengths of muscle contraction?

A

Neurons code the intensity of information by the frequency of action potentials.

56
Q

Conduction velocity

A

· the speed that an action potential is propagated along an axon

Fast:
· essential neural pathways
· Reflexes

Slow
· Serve internal organs
. Digestive tract, glands and blood vessels

57
Q

What 2 factors effect conduction velocity?

A

Axon Diameter –> longer axons conduct more rapidly b/c offer less resistance to flow of local current, bringing adjacent areas of the membrane to threshold quicker

Myelination –> insulation: proventing almost allleakage of the charge from the axon and allowing the membrane potentials to change more rapidly

58
Q

SALTATORY PROPAGATION

A
  • Conduction within a myelinated axon.
  • Jump between nodes.
59
Q

CONTINUOUS PROPAGATION

A
  • Conduction within an unmyelinated axon.
  • Charge leaks through channels
  • Separate opening of voltage gated channels = slow.
60
Q

SYNAPTIC TRANSMISSION

A
  1. AP arrives at axon terminals.
  2. Voltage gates calcium channels open and calcium enters the axon terminal.
  3. Calcium causes the vesicles to migrate towards presynaptic membrane, which fuse with membrane.
  4. Diffuse across synaptic cleft.
  5. Binds to receptors, chemically gated channels.
  6. Ion channles open to postsynaptic membrane.
  7. Potential of postsynaptic membrane changes.
  8. If enough excitatory – AP GENERATES.
61
Q

NT effects are terminated by

A
  1. Reuptake - NT’s re-enter presynaptic cell to be reused.
  2. Degradation - enzymes breakdown NT into a substance that cant be received by post synaptic
    receptors.
  3. Diffuse away from the synapse.
62
Q

An axon is connected to the neuron cell body at the

A

axon hillock

63
Q

Ion channels that are always open are called

A

leak channels

64
Q

Excitatory Postsynaptic Potential (EPSP)

A

Excitatory ion channels are permeable to sodium and potassium

  • More sodium moves into the cell, than potassium moves out of the cell.
  • Membrane becomes more positive, stimulating depolarisation of the membrane
65
Q

Inhibitory Postsynaptic Potential (IPSP)

A

Involve inhibitory ion channels that are permeable to chloride and potassium ions

  • Chloride ion moves into the cell whilst potassium moves out
  • Inside of cell becomes more negative causing hyperpolarisation
  • Effect makes it more difficult for the cell membrane potential to reach threshold
  • Makes it less likely for an action potential to be generated

DEN1DSA (17 decks)

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