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Biology Eduqas A Level > A2C3 - Chapter 13 - Nervous System > Flashcards

A2C3 - Chapter 13 - Nervous System Flashcards

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1
Q

State the components of a nervous response. (3)

A

Receptors

Nervous system or hormones transfer information from receptors to effectors.

Effectors

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2
Q

Name the two divisions of the nervous system.

A

Central Nervous System (CNS)
Peripheral Nervous System (PNS)

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3
Q

Outline the gross structure of the mammalian nervous system.

A

pns = voluntary, autonomic

autonomic = sympathetic, parasympathetic.

cns = spinal cord and brain

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4
Q

What is the central nervous system? (CNS)

A

Brain and spinal cord.

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5
Q

What is the peripheral nervous system? (PNS)

A

Pairs of nerves that originate from the CNS and carry nerve impulses into and out of the CNS.

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6
Q

Label the spinal cord. (7)

A

Posterior dorsal root ganglion.
White matter, Grey matter, Central canal.
Posterior dorsal root.
Anterior Ventral root.
Meninges.

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7
Q

What is the dorsal root?

A

One of the two roots emerging from the spinal cord.
Travels to the dorsal root ganglion.
Sensory neurones enter the spinal cord via the dorsal root.

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8
Q

What is the ventral root?

A

One of the two roots emerging from the spinal cord.
Motor neurones leave the spinal cord through the ventral root.

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9
Q

What is a reflex?

A

A rapid autonomic nervous system response to a sensiry stimulus by the body. It serves as a protective mechanism.

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10
Q

Outline the simple reflex arc.

A

Stimulus –> receptor –> sensory neurone –> relay neurone –> motor neurone –> effector –> response

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11
Q

How does a reaction differ from a reflex.

A

Reaction is voluntary and coordinated by the brain.
Reflex is non-voluntary and does not involve the brain.

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12
Q

What is a nerve net?

A

Simplest form of nervous system found in cnidarians

Consists of interconnected nerve cells with short extensions to allow for response to a limited number of stimuli.

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13
Q

State the 3 types of functional neurones.

A

Sensory Neurone
Relay Neurone
Motor Neurone

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14
Q

State the function of the sensory neurone.

A

Carries nerve impulses from receptors to CNS via the dorsal root.

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15
Q

State the function of the motor neurone.

A

Carries nerve impulses from the CNS to the effectors via the ventral root.

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16
Q

State and explain the structure of the motor neurone.

A

Short dendrites = Carry impulses from CNS to cell body

Cell body at end of axon = Found at one end of the neurone

Long Axon = Carries impulse from cell body to effectors.

Axon Terminal = Site of neurotransmitter release.

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17
Q

State the function of a relay neurone.

A

Located in the spinal cord.
Links the sensory neurone to the motor neurone.

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18
Q

What is the function of the dendrites?

A

They are short, branched extensions of the cell body.

Recieve nerve impulses from other neurones.

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19
Q

Describe the cell body.

A

The region of the neurone containing the organelles, notably the nucleus and endoplasmic reticulum.

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20
Q

What is the function of the axon?

A

A long fibre that conducts nerve impulses away from the cell body.

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21
Q

What are axon terminals?

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A

Branched endings of an axon that approach the muscle fibre.

22
Q

What is a synaptic end bulb?

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A

The end of an axon that is bulbous shaped and contains synaptic vesicles filled with synaptic neurotransmitters.

23
Q

Describe the additional features of a myelinated neurone.

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A

Schwann cells = wrap around axon, involved in electrical insulation, phagocytosis, nerve regeneration

Myelin sheath = made from myelin rich membranes of schwann cells.

Nodes of ranvier = small gaps between neighbouring schwann cells where there is no myelinated sheath.

24
Q

Define action potential.

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A

The temporary change in electrical potential across a membrane due to the response to the transmission of a nerve impulse.

25
What is resting potential?
The potential difference (voltage) across a neurone membrane when not stimuated (-70mV)
26
How is resting potential established?
Membrane is more permeable to K+ than Na+. The sodium/potassium pump actively transports 3Na+ out and 2K+ into the cell. Organic phosphates and large protein anions remain in the cytoplasm. Establishes electrochemical gradient because the cell contents are more negative than the extracellular environment.
27
Name the stages of the action potential.
1. Depolarisation 2. Repolarisation 3. Hyperpolarisation 4. Return to resting potential.
28
What happens during depolarisation?
Stimulus causes for a change in voltage across an axon membrane, opening the na/k channels. Na+ diffuses into the axon. The potential difference across the membrane becomes more positive, membrane depolarises.
29
What happens during repolarisation?
1. Membrane potential reaches +40mV. 2. voltage-gated Na+ channels close and K+ channels open. 3. K+ diffuses out of the cell down the electrochemical gradient. 4. Potential difference across the membrane becomes more negative, therefore the membrane repolarises.
30
What happens during hyperpolarisation?
1. Overshoot of K+ going out. 2. Potential difference becomes more negative than the resting potential. 3. Membrane hyperpolarises preventing another impulse from occuring.
31
What is the refractory period?
The time period after an action potential in which another action potential is prevented.
32
Why is the refractory period important?
Ensures that action potentials can only be propagated in one direction.
33
Describe the shape of the oscilloscope trace showing the passage of an action potential.
Up - depolarisation Down - repolarisation Down further - hyperpolarisation Normal - refractory period
34
Describe the 'all or nothing' law.
Principle stating that all stimuli above the threshold for an action potential will generate the same size of action potential, regardless of the strength of the stimulus.
35
State the factors affecting the speed of conduction in a nervous response.
- Temperature - Axon diameter - Myelin sheath
36
Explain why myelinated axons conduct impulses faster than unmyelinated axons.
Saltatory Propagation = Impulse can jump from one node of ranvier to another (depolarisation cannot occur where there is myelin sheath as it is an electrical insulator). Therefore, the impulse does not travel the whole length of the axon.
37
How does temperature affect the speed of conduction of nervous impulses?
The higher the temperature, the faster the speed of conduction.
38
How does axon diameter affect the speed of conduction of nervous impulses?
The larger the diameter, the faster the speed of conduction.
39
What is a synapse?
The junction between two nerve cells or nerve cell and effector.
40
What is the function of the synapses? (4)
- Electrical impulse is unable to cross the junction. - Neurotransmitters send impulses between neurones or from neurones to effectors. - Summation of sub-threshold impulses -New impulses can be generated at several different neurones for multiple simultaneous responses.
41
Think of the synaptic photo, what are the 5 labels to remember?
Pre-synaptic knob Vesicle with neurotransmitters Synaptic cleft Receptor Post-synaptic knob
42
Describe the structure of a synapse. (4)
Presynaptic neurone ends in pre-synaptic knob Synaptic knob contains high concentration of mitochondria, vesicles with neurotransmitters and endoplasmic reticulum. Synaptic cleft (20-30nm) Post synaptic neurone has complementary receptors to the neurotransmitters. (Ligand-gated Na+ channels)
43
What is the synaptic cleft?
A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters.
44
Describe synaptic transmission in the presynaptic neurone. (3)
1. Wave of depolarisation comes down the presynaptic neurone, causing voltage-gated Ca2+ channels to open. 2. Ca2+ causes the vesicles of neurotransmitters to move towards and fuse with the presynaptic membrane. 3. Exocytosis of neurotransmitter (eg: acetylcholine) into synaptic cleft.
45
How do neurotransmitters cross the synaptic cleft?
Simple diffusion.
46
Describe synaptic transmission in the post-synaptic neurone. (3)
1. Acetylcholine diffuses across the synaptic cleft and binds to specific receptors on the post-synaptic neurone. 2. Ligand-gated Na+ channels open. 3. Influx of Na+ ions raises the membrane to threshold potential, action potential is generated.
47
How is the merging of impulses prevented during synaptic transmission? (3)
Active transport of Ca2+ out of synaptic knob. Acetylcholinesterase breaking it down into Choline and Acetate. Reabsorption of neurotransmitters.
48
Describe the role of acetylcholinesterase in synaptic transmission.
Hydrolyses acetylcholine in the post-synaptic neurone. Products diffuse back across the cleft.
49
What is the effect of organophosphates on the transmission of impulses?
Act as acetylcholinesterase inhibitors, preventing the hydrolysis of acetylcholine in the post-synaptic neurone. Results in continuous stimulation of the neurone
50
Where are organophosphates commonly found?
Component of insecticides.
51
How do psychoactive drugs (eg: amphetamine) affect the transmission of impulses?
Excitatory drugs Stmulate the release of neurotransmitters such as noradrenaline.

Biology Eduqas A Level (14 decks)

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