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B2- Anatomy (T-level Nursing) > Nervous system > Flashcards

Nervous system Flashcards

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1
Q

What is the nervous system?

A

It controls and coordinates our movements. It allows us to interact with our surrounding through receptors and effectors.

It also controls many autonomic functions - those we have no control over. Like peristalsis, regulation of breathing rate and heart rate. l

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2
Q

What are the components of the nervous system?

A

• brain
• spinal cord
• nerves

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3
Q

What makes up the central nervous system (CNS)?

A

• Brain
• Spinal cord

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4
Q

What makes up the peripheral nervous system?

A

The sensory neurones that connect receptors with the CNS and also the motor neurones that connect to muscles or glands and bring about responses like movement.

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5
Q

What is the autonomic nervous system?

A

The neuron’s which control the:
• Sympathetic nervous system: which regulates heart rate and the fight or flight response.
• Parasympathetic nervous system: which regulates excretion, digestion and metabolic activities.

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6
Q

Explain the structure of a neuron?

A

• Cell body/soma: contains all the organelles and information needed for the cell to work.
• Dendrites: extensions of the soma. They receive information and transfer it to the cell body.
• Axon: the conductive arm of the neuron. It transmits an impulse to the axon terminal which ends in a muscle or a gland.

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7
Q

Where does an impulse travel from and to in a neuron?

A

The impulse travels from the dendrite to the axon terminal.

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8
Q

What is the role of the brain?

A

The brain is where sensory inputs (hearing, touch and vision) are processed and responses (movement) are initiated.

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9
Q

What is the role of the spinal cord?

A

It is important in reflex actions like moving your hand away from a hot plate.

It also forms the main connection between the brain and the sensory and motor neurones.

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10
Q

What are nerves made up of?

A

Bundles of many neurones.

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11
Q

What are neurones?

A

Nerve cells.

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12
Q

What are nerve impulses?

A

Electrical signals transmitted along a neurone.

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13
Q

How is an electrical impulse stimulated and what path does it take to enable a response?

A

• Stimulus
• Receptor cell detects stimulus
• Sensory neurone
• Relay neurone in spinal cord
• Motor neurone
• Effector
• Response

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14
Q

What is a receptor cell?

A

These are specialised cells that detect changes in surroundings.

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15
Q

What are examples of effectors?

A

• Muscles
• Glands

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16
Q

What do motor neurones do?

A

They transmit nerve impulses in one direction (away from the cell body).

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17
Q

What are the features of a motor neurone?

A

• Dendrites: that make connections with other neurones, mostly within the CNS.
• Cell body: contains the nucleus and other organelles.
• Axon: carries the nerve impulse from the cell body.

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18
Q

What is in the myelin sheath?

A

It consists of schwann cells, a specialised type of cell wrapped around the axon which acts in a similar way to the insulation on an electrical cable.

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19
Q

What are the small gaps between the schwann cells called?

A

Nodes of Ranvier.

The combination of the myelin sheath and the noses of Ranvier helps to significantly increase the rate at which the nerve impulse is carried along the axon.

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20
Q

What connections do relay neurones make?

A

The connections are called synapses. These are between other neurones, specifically sensory and motor neurones.

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21
Q

What do sensory neurones do?

A

They carry nerve impulses from receptors that act as the body’s sensors towards the CNS.

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22
Q

What is the role of the CNS?

A

It takes all the information contained in inputs from sensory neurones and processes it.

It then sends impulses via motor neurones to effector organs.

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23
Q

Explain the structure and function of a myelinated nerve fibre.

A

• They’re long, making up the majority of the neurones in the CNS and peripheral.
• They’re white.
• The schwann cells wrap around the axon.
• The nodes of ranvier are present for conduction.
• The speed of conduction is fast, due to the nodes of ranvier (1-3 m/s).
• There is no loss of impulse.

24
Q

Explain the structure and function of a non myelinated nerve fibre.

A

• They’re short in the CNS and peripheral, but make up the majority of the automatic.
• They don’t have any schwann cells, which forms a groove in the axon.
• The nodes of ranvier aren’t present.
• The speed of conduction is slow (3-120 m/s).
• There is a loss of impulse.

25
Q

What happens when a neurone is at rest?

A

There is a small potential difference across the plasma membrane of about -60mV.

This means the inside of the neurone is slightly more negative that the outside due to positive sodium ions, which have been pumped out of the neurone.

This polarisation of the plasma membrane neurone is described as the resting potential.

26
Q

How does a nerve impulse impact the membranes potential?

A

It causes a rapid change in the membrane potential, so that the membrane is depolarised.

The inside is now slightly positive compared to the outside.

This is rapidly revered within a few milliseconds and the membrane becomes depolarised. This is known as an action potential, which is transmitted along the axon, representing a nerve impulse.

27
Q

How does the action potential travel in a myelinated neurone?

A

It jumps from one node of ranvier to the next. This makes the transfer of the nerve impulse faster.

28
Q

Give an example of a myelinated neurone.

A

A motor neurone.

29
Q

Why is the speed of an impulse important?

A

A motor neurone could be considerably long.

30
Q

What is a synapse?

A

These are the gaps or connections between the end of one neurone and the start of another.

31
Q

What is the nerve before a synapse called?

A

The pre synaptic nerve.

32
Q

What is the nerve after a synapse called?

A

The post synaptic nerve.

33
Q

How does an impulse travel across a synapse?

A

• An impulse only moves in one direction.
• An impulse can’t jump across a synapse itself.
• Chemicals, called neurotransmitters release into the synapse and diffuse across the membrane, carrying the synapse with it.

34
Q

Define polarisation.

A

Different electrical charges on either side of the plasma membrane caused by the active transport of ions.

35
Q

Define depolarisation.

A

The reversal of the charge difference.

36
Q

Define repolarisation.

A

The restoration of the original charge difference.

37
Q

Explain how an impulse travels across a synapse.

A

• The synaptic knob makes a connection with a muscle or another neurone.
• When the nurse impulse arrives at the synaptic knob it causes the release of neurotransmitters from membrane bound vesicles.
• These diffuse across the synaptic cleft and binds to the decorators on the membrane of the muscle cells or next neurone.
• If enough neurotransmitters bind, the post synaptic membrane will become depolarised and a new nerve impulse will be generated in the next neurone. (If in a muscle cell its will result in a contraction rather than a new nerve impulse).

38
Q

Explain how an impulse travels across a synapse with the use of calcium channels.

A

• In the pre-synaptic nerve, the action potential arrives at the axon terminal.
• Calcium channels open and calcium ions flood down their concentration gradient.
• The calcium concentration increases inside the terminal, causing synaptic vesicles to move to the pre synaptic membrane.
• Synaptic vesicles fuse with the membrane and release neurotransmitters into the synaptic gap.
• The neurotransmitters diffuse across the synapse.
• Neurotransmitters then bind to receptors on the sodium channels.
• They sodium channels then open and sodium ions diffuse in creating an excitatory post synaptic potential.
• It reaches the threshold, causing the action potential to generate.

39
Q

What is a reflex action?

A

This is an automatic response to an external stimulus.

This helps minimise the damage caused and allows us to think of survival responses.

40
Q

What is the reflex response to a bright light?

A

Muscle contracts to make the pupil smaller.

41
Q

What does the brain stem contain and what are their functions?

A

• Pituitary gland: produce hormones.
• Thalamus: sends and receives sensory info and directs messages to the right areas of the cerebrum for further processing.
• Pons: controls breathing, sleeping, swallowing, bladder control and aids in signal transmission.
• Medula oblongata: controls automatic functions like vomiting, sneezing and involuntary bodily processes.

42
Q

What is the function of the cerebellum?

A

It has a role in motor control and some cognitive functions like attention, language and emotional control like fear and pleasure response.

It contributes to coordination and timing by processing information from sensory system.

43
Q

Define resting potential.

A

The difference in voltage across a neurone membrane, when not transmitting an impulse.

The average resting potential is -70mV.

44
Q

What is meant by mV?

A

milli-volts.

45
Q

What indicates a higher voltage?

A

Ions like Na+ and K+ carry an electrical charge (voltage).

The more ions in a cell, the higher the voltage.

46
Q

What is voltage?

A

Electrical charge.

47
Q

What is potential difference?

A

The difference in ion concentration in the cell and the surrounding area.

If there is a difference in this, the cell is polarised.

48
Q

What is an electrical impulse also, in an axon terminal?

A

A wave of depolarisation.

49
Q

Explain how a less positive environment is created inside of a nerve cell.

A

• Na+ and K+ ions move in and out of the cell to create a resting potential.
• For every 3Na+ transferred out the cell, 2K+ are transferred in.
• This creates a less positive environment in the cell (-70mV).

50
Q

How is an action potential generated?

A

• The membrane is stimulated, via touch.
• Na+ gates open.
• Na+ is in the cell.
• If the stimulus is big, more Na+ gates open.
• There’s an influx of Na+.

51
Q

Is the cell polarised at rest?

A

Yes.

52
Q

Is energy required to maintain a resting state?

A

Yes.

53
Q

Explain in full how an action potential is generated.

A

• A nervous impulse is stimulated by a receptor cell or another neurone, causing an action potential.
• This causes a sodium channel to open and sodium ions to enter the cell, making it more positive.
• If the action potential causes the voltage to change, it reaches -50mV, causing the rest of the sodium gates to open.
• This allows for a massive influx of sodium ions, making the potential positive, to around +40mV.
• Once the potential difference reaches +40mV the sodium gates close.
• The potassium channels open and potassium ions exit the cell.
• This decreases the potential difference and repolarises the cell. Making the inside more negative again.
• It’s now back to its resting potential.

54
Q

What is saltatory conduction?

A

This is how an action potential is conducted in a myelinated neurone.

It describes how an electrical impulse skips from node of ranvier to node of ranvier down the full length of an axon.

55
Q

How does saltatory conduction affect the speed of conduction?

A

It increases the speed of conduction and looses no impulse.

56
Q

Where does ion exchange occur in saltatory conduction?

A

• At the node of ranvier, between schwann cells.

• When action potential reaches a node, sodium ions diffuse into the axon membrane.

• They then diffuse through the axon side ways to the next node.

57
Q

What are 2 benefits of saltatory conduction?

A

• Less ATP is needed.
• Fewer ions are exchanged.

B2- Anatomy (T-level Nursing) (23 decks)

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