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A level Biology - Regular > Chapter 13 - Neuronal Communication > Flashcards

Chapter 13 - Neuronal Communication Flashcards

1
Q

What are the different ways cell signalling can happen ?

A
  • Transfer signals locally (Nuerotransmitter)
  • Transfer signals across large distances (Hormonal)
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2
Q

What is cell signalling ?

A

When one cell releases a chemical which has an affect on another cell

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3
Q

Why is coordination needed ?

A

Specialised cells must work together to carry out an overall function. To carry out this whole function cells must be able to communicate with one another

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4
Q

What is Homeostasis ?

A

The regulation of internal conditions of a cell or organism to maintain optimum conditions for its function

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5
Q

What is the nervous system used for ?
What are the roles of the neurone ?

A
  • Responsible for detecting stimuli and triggering a response
  • Used to transmit electrical impulses rapidly
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6
Q

What are the 3 main types of neurones ?

A

1) Sensory
2) Relay
3) Motor

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7
Q

What pathway do electrical impulses follow ?

A

Receptor->Sensory->Relay->Motor->Effector

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8
Q

What are the features of a sensory neurone ?

A
  • Cell body in the middle of a neurone
  • Long dendron
  • Lond axon, needs to travel far distances
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9
Q

What are the features of a relay neurone ?

A
  • Short axon, Short dendron as they do not need to travel far distances
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10
Q

What are the features of a motor neurone ?

A
  • Long axon, no dendron as they are located directly in CNS
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11
Q

What are the features of the Myelin sheath ?

A
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12
Q

What is the function and the features of the Myelin sheath ?

A
  • Composed of layer of Shwann cells
  • Each Shwann cell adds a double layer of phospholipids
  • Myelin sheath acts as an insulating layer; allowing myelinated neurones to transmit impulses at a faster rate
  • Electrical impilses jump between nodes of Ranvier (Saltatory conduction)
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13
Q

What is the function of sensory receptors ?
What do they acts as ?

A

Detect chane in an organisms environment and act as transducers (convert physical stimuli detected into nerve impulses)

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14
Q

What is an example of a sensory receptor ?
What does it detect for ?

A

Pacinian corpuscle
- Detects mechanical pressure

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15
Q

What are the structural features of the Pacinian Corpuscle ?

A
  • Within the membrane of the neurone there are Na+ channels and when they stretch their permeability changes
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16
Q

How does the Pacinian Corpuscle work ?

A

1) In the resting state, Na+ channels are not stretched hence no ions released (In resting potential)
2) Pressure is applied; membrane stretches
3) Na+ channels widen; Na+ diffuses into neurone
4) Influx of Na+ causes neurone to be polarised (Generator potential)
5) Generator potential creates action potential which transmits along neurone to CNS

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17
Q

What happens during resting potential ?

A
  • When a neurone is not transmitting an impulse the membrane is polarised with a P.D of -70mV
  • Occurs as a result of the movement of 3 Na+ out of the axon and 2K+ into the axon past a Na-K active pump
    (Leaky membrane hence K+ also leaks out passively)
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18
Q

What are the steps for the propagation of an impulse ?

A

1) Resting potential
2) Action potential
3) Depolarisation
4) Repolarisation
5) Hyperpolarisation
6) Resting potential

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19
Q

What is action potential ?

A
  • The increasing of potential difference inside the axon via the energy from a stimulus - causing some voltage gated Na+ channels to open
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20
Q

How is an action potential propagated ?

A

1) At resting potential the overall concentration of negative ions inside the axon is greater than positive
2) When the stimulus is deteceted there is an influx of Na+ -> causing the axon to be more positive
3) The Na+ within the axon are attracted to the negative regions of the axon thereby moving up along the axon; creating a localised circuit (AREA BEHIND WILL RETURN TO ITS ORIGINAL STATE)

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21
Q

What happens at depolarisation ?

A

Stimulus triggers voltage gated sodium ion channels to open; making the membrane more permeable to Sodium ions; sodium ions diffuses into the axon down an electrochemical gradient which makes the axon less negative

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22
Q

What happens at repolarisation ?

A

When the P.D reaches +40mV the voltage gated sodium ion channels close and voltage gated potassium ion channels opens. Pottasium ions diffuse out of the axo, down the electrochamical gradient which reduces its charge

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23
Q

What does the graph for impulses look like ?

A
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24
Q

What is hyperpolarisation ?
Why is it necessary ?

A
  • After an action potential there is a short period where the axon cannot be excited again
    1. Makes sure action potential is unidirectional
    2. Prevents propagation backwards
    3. Ensured action potentials dont overlap
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25
Q

What is saltatory conduction ?

A

Within myelinated axons, Sodium ion channels are only present at the nodes of Ranvier hence depolarisation can only occur at the nodes of Ranvier (Action potentials jump between nodes)

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26
Q

What is the benefits of saltatory conduction in myelinated axons ?

A

1 - Faster wave of depolarisation as opening channels takes time and reducing the number of channels present reduces the time for action potentials
2 - More energy efficient as Sodium pumps require ATP so reducing the amount of pumps needed reduces energy used

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27
Q

What factors affect rate of action potential ?

A
  • Myelinated or unmyelinated
  • Axon diamter = greater diameter means less resistance to the flow of ion in the cytoplasm
  • Temperature = higher temperature means a quicker rate of ion diffusion until denaturing
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28
Q

What is the all or nothing principle ?

A
  • A certain threshold will always stimulate a response, if the threshold is reached an action potential will always be created no matter how large the stimuli is
  • The only difference between weak and strong stimuli is the frequency of action potentials
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29
Q

What is a synapse ?

A
  • Junction between two neurones, or a neurone and effectors and is the location of impulse transfer
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30
Q

What is the structure of a neurone to neurone synapse ?

A

1) Presynaptic neurone
2) Synaptic knob
3) Synaptic cleft
4) Presynaptic membrane
5) Post synaptic membrane
6) Neurostransmitter receptors
7) Post synaptic neurone

31
Q

What are the two types of neurotransmitters ?

A

1) Excitatory (Acetylcholine) - Results in depolarisation of post synaptic neurone
2) Inhibitory (GABA) - Results in hyperpolarisation of postsynaptic neurone thereby preventing action potentials

32
Q

How does an excitatory neurotransmitter transmit impulses ?

A

1) Arrival of action potential at the presynaptic neurone; causing Ca2+ voltage gated channels to open and Ca2+ enters synpaptic knob
2) Influx of Ca2+ causes synaptic vesicle to fuse with the presynaptic membrane via exocytosis and releases Acetylcholine into synaptic cleft
3) Acetylcholine molecules fuse with receptor sites on Na+ channels; causing Na+ channels to open and Na+ diffuses into post synaptic neurone
4) Influx of Na+ generates action potential in post synaptic neurone
5) Acetylcholinesterase causes the hydrolysis of ACH into choline and acetyl which diffuse back into presynaptic neurone; preventing new action potentials
6) ATP released via mitochondria is used to recombine choline and acetyl into ACH(stored in vesicles) and Na+ channels close in the lack of ACH

33
Q

What is the role of the synapse ?

A
  • Ensure impulses are unidirectional as receptors are only present on post synaptic neurone
  • Single stimuli can create a number of simultaneous responses
  • Prevents overstimulisation
  • Allows for memory
  • Multiple stimuli can produce one response
34
Q

What is summation ?

A
  • When multiple small impulses are added together to create a succesful action potential
35
Q

Why may summation be required ?

A
  • Small amounts of ACH are released into synaptic cleft
  • Small number of voltage gated ion channels open
    therefore threshold is not reached
36
Q

What are the benefits of summation ?

A
  • Effects of stimuli are magnified
  • Avoids nervous system being overwhelmed
37
Q

What are the two main types of summation ?

A

1) Spatial summation
- When a number of presynaptic neurone connect to one post synaptic
2) Temporal summation
- Occurs when one presynaptic neurone releases neurotransmitter as a result of multiple other action potentials

38
Q

How is the mammalian nervous system organised ?

A

1 - CNS = nrain and spinal cord
2 - PNS = All the sensory and motor neurones

39
Q

How is the PNS organised ?

A
  • Somatic - Autonomic
    conscious control subconsious
    1) Symphatic
    fight or flight motor
    2) Parasymphatic
    voluntary motor
40
Q

What is the brain ?
Why is it an advantage ?

A

The brain is the control centre
Advantage of having a brain is that it means communication is faster than if the ocntrol centres were used for specific functions

41
Q

What is the gross structure of the brain ?

A

1 - Cerebrum (Very back)
2 - Cerebellum (Below cerebrum but also at the back)
3 - Medulla oblongata (On brain stem in the middle)
4 - Hypothalamus (to the left of the medulla oblongata, towards the face)
5 - Pituitary gland (Very bottom)

42
Q

What is the function of the Cerebrum ?

A
  • Recieves sensory informatio and responds in accordance with past experience
43
Q

What are the features of the Cerebrum ?

A
  • Highly convoluted to increase SA hence capacity for complex activity
  • Split into left and right hemisphere
44
Q

What is the function of the Cerebellum ?

A
  • Controls muscular movement, posture, and movement hence it coordinated movvement
  • Recieves information about balance -> relays information to cerebral cortex
45
Q

What is the function of the Medulla Oblongata ?

A
  • Contains regulatory centres to control reflex activity
  • Breathing rate - Heart rate etc.
46
Q

What is the function of the Hypothalamus ?

A
  • Controlling region for Autonomic Nervous system
47
Q

What are the Hypothalamus’ functions split up into ?

A

1 - Parasymathetic
2 - Symphatic
- Controls complex patterns of behaviour
- Produces Hormones

48
Q

What are the features of the Pituitary Gland ?

A
  • Controls most of the glands in the body
  • Divided into :
    1. Anterior pituitary gland
    2 - Posterior Pituitary
49
Q

What is the definition of Reflex ?

A
  • When the body responds to stimuli without conscious thought (Involuntary action)
50
Q

What is a Reflex arc ?

A

Pathway that neurones involed in reflex action take

51
Q

What is an example of a Reflex arc pathway ?

A
  1. Receptor (Detects stimuli)
  2. Sensory neurone (Connects impulse to spinal chord)
  3. Relay neurone (Connects sensory neurone to motor neurone in spinal chord)
  4. Motor neurone (Carries impulse to effector)
52
Q

What are the 2 main examples of Reflex arc ?

A

1 - Knee jerk reflex (Spinal chord)
2 - Blinking reflex (Brain)

53
Q

Explain the knee jerk reflex

A
  • When leg is tapped at the patella, patellar tendon stretches (Stimuli)
  • Initiates a reflex arc; causing the thigh muscles to contract
  • Simultaneously there is a relaxing of the antagonistic flexor hamstring; a kick occurs
54
Q

What is the function of the knee jerk reflex ?

A
  • Allows you to maintain posture and balance
55
Q

Explain the Blinking reflex

A
  • When Cornea is irritated (Stimuli)
  • Impulse is triggered along sensory neurone; which is passed along relay neurone in brain stem
  • Impulse sent to motor neurones connected to eyelid muscles
56
Q

What is the survival importance of Reflexes ?

A
  • Reflexes minimise the riskof harm or reduce severity of harm
  • Increase chance of survival by :
    a) Being involuntary = fast
    b) Not having been learned = Provides immediate protection
    c) Extremely fast
57
Q

What are the two ways the body can coordinate a stress response ?

A
58
Q

How can Nervous and Edocrine systems work together to to control heart rate ?

A
  • Nervous or Hormonal system can signal one of two centres located in the medulla Oblongata linked to the SAN in the heart
  • The centre stimulated is dependent on BP change or pH of blood
59
Q

How do the two centres work to control blood pressure in the Medulla Oblongata

A

1 - One centre increases heart rate by sending impulses through Sympathetic nervous system Impulses transmitted via accelerator nerve
2 - Other centre decreases heart rate by sending impulses through parasymphathetic nervous system
- Impulse transmitted via Vagus nerve

60
Q

Why are each centres stimulated ?

A

Baroreceptros - Receptors detecting changes in BP
Chemoreceptors - Receptors detecting changes in chemical levels such as CO2

61
Q

Where are the receptors linked to controlling blood located ?

A

Baroreceptors - Aorta, Vena Cava, Carotid artery
Chemoreceptors - Aorta, Carotid artery (Main artery in neck), and Medulla

62
Q

How do Chemoreceptors work ?

A
  1. Increased muscular activity (metabolic activity)
  2. More CO2 produced by tissues
  3. Blood pH is lowered
  4. Centre in medulla oblongata that speeds heart rate increases frequency of impulses to SAN cia SYMPATHETIC PATHWAY
  5. SAN increases heart rate
  6. Increased blood flow to remove CO2 faster
    (OPPOSITE OCCURS WHEN METABOLIC ACTIVITY DECREASES)
63
Q

How do Baroreceptors work ?

A
  • Present in Aorta and Carotid artery walls
    1. B.P increases, Baroreceptors detect the change in pressure
    2. Impulses are sent to medulla oblongata centre which lowers Heart rate
    3. Centre sends impulses along parasymphathetic neurones to SAN which decreases heart rate to reduce B.P back to normal
    (OPPOSITE OCCURS WHEN BP IS TOO LOW)
64
Q

How is heart rate affected by hormones ?

A
  • HORMONAL COMMUNICATION CHAPTER
65
Q

What are the 3 main types of muscles ?

A
  1. Skeletal muscle
  2. Cardiac muscle
  3. Incolumtary
66
Q

What are the features of skeletal muscles ?

A
  • Striated
  • Voluntary
  • Regularly arranged to be able to contract in one direction
  • Rapid
  • Short contractions
  • Multinucleated
67
Q

What are the features of Cadiac muscles ?

A
  • Specialised striated
  • Involuntary
  • Cells branch and are interconnected; simultaneous contractions
  • Intermediate speed
  • Intermediate contraction times
  • Shows faint striations
  • Uninucleated
68
Q

What are the features of Involuntary muscles ?

A
  • Non striated
  • Involuntary
  • no regular arrangement
  • Slow
  • Remain contracted for long
  • Show no striations
  • Spindle fibre shaped
  • Uninucleated
69
Q

What are the features of skeletal muscles ?

A
70
Q

What happens to the bands during skeletal muscle contractions ?

A

Z line does not change
I band shortens/disappears
A band does not change
H-zone shortens/disappears
Sarcomere shortens

71
Q

What is the structure of the skeletal muscle filament ?

A
72
Q

How does an action potential get carried into a muscle ?

A

1 - Action potential arrives at acon terminal
2 - Action potential causes uptake of Ca2+
3 - Ca2+ ions cause vesicles containing ACh to fuse with presynaptic membrane
4 - ACh molecules bind with receptors in the sarcolemma; causing them to open Na+ channels
5 - ACh molecules bind with receptors in sarcolemma; causing them to open Na+ channels
6 - Na+ ions flood in through the open channels in sarcolemma. This depolarises membrane and initiates an action potential which spreads alone membrane

7 - Depolarisation of sarcolemma spreads down T tubules
8 - Ca2+ channels open and Ca2+ ions diffuse out of the sarcoplasmic reticulum
9 - Ca2+ ions bind to troponin. Tropomyosin moves to expose myosin binding sites on actin filaments; Myosin heads bind and filaments slide

73
Q

How does ATP allow for the sliding filament model to work ?

A

1 - Myosin heads hydrolyze ATP and become reorientated and energised
2 - Myosin heads bind to actin to form crossbridges
3 - Myosin heads rotate towards center of sarcomere
4 - Myosin heads bind to ATP; crossbdridge will detach from actin

74
Q

How can creatine phosphate act as a reserve for ATP ?

A

Creatine acts as a reserve supply of Pi for ADP molecules to form ATP
- Used for short bursts bevause ATP is provided quickly but Creatine is used up quickly

A level Biology - Regular (14 decks)

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