Chapter 13 (Neuronal Communication) Flashcards

(50 cards)

1
Q

How does the Pacinian corpuscle convert mechanical pressure into a nervous impulse

A

1) In the resting state, stretch mediated sodium ion channels are closed, so the Pacinian corpuscle has a resting potential
2) Pressure= surrounding membrane stretches
3) Therefore, sodium ion channels widen and diffusion occurs
4) An influx of positive ions depolarises the membrane = generator potential
5) Generator potential creates an action potential (nerve impulse) and passes along the sensory neurone

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2
Q

How is a resting potential established?

A

1) Sodium-potassium pump moves 3 Na+ ions out and 2 K+ ions into the axon
2) Therefore, there mare more Na+ ions outside the membrane and more K+ ions inside, so both diffuse down their respective electrochemical gradients
3) However, most gated sodium ion channels are closed but potassium ion channels are open, meaning that only K+ ions can diffuse, resulting in a positive outside and negative inside (resting potential of -70mv)

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3
Q

What is the value of resting potential across a membrane?

A

-70mv

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4
Q

What are the stages of myosin binding to actin in the sliding filament model?

A

1) Tropomyosin blocks binding site on actin molecule
2) Ca2+ ions released from endoplasmic reticulum causes tropomyosin to move away from the binding sites
3) Myosin head (with ADP molecule) attaches to the binding site on actin filament
4) Myosin head changes angle, moving actin filament and ADP is released
5) ATP molecule attaches to myosin head, causing the head to detach from actin
6) Hydrolysis of ATP to ADP provides energy for myosin head to go back to its original position
7) Myosin head attaches to actin binding site further along and the cycle is repeated

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5
Q

What are the cells called that make up the myelin sheath?

A

Schwann cells

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6
Q

Where is the cell body on a sensory neurone?

A

Cell body is found on an offshoot from the axon/dendron

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7
Q

Where is the cell body on a relay neurone?

A

Cell body is near the start of the neurone, connected to the dendrites by a short dendron

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8
Q

Where is the cell body on a motor neurone?

A

Cell body is at the start of the neurone, where all the dendrites meet

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9
Q

When is ADP released from myosin?

A

When the myosin head changes angle while bounded to the actin

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10
Q

What is the Cerebrum and what does it do?

A

Made up of the 4 lobes, controls voluntary actions

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11
Q

What is the cerebellum and what does it do?

A

Controls unconscious functions, but does not initiate them

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12
Q

What is the Medulla oblongata and what does it do?

A

Part below the pituitary gland, used in autonomic control (e.g. breathing and heart rate)

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13
Q

What does the hypothalamus do?

A

• Regulatory centre for temperature and water balance
• Main control for the autonomic nervous system

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14
Q

What does the pituitary gland do?

A

• Anterior pituitary- Produces six hormones, such as FSH
• Posterior pituitary- store and release hormones

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15
Q

What is homeostasis?

A

When the internal environment is kept within a narrow range

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16
Q

What is cell signalling?

A

One cell releases a chemical which affects another cell

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17
Q

What is the electrical impulse pathway?

A

(Stimulus)
1) Receptor
2) Sensory neurone
3) Relay neurone
4) Motor neurone
5) Effector cell
(Response)

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18
Q

What is a node of Ranvier?

A

The gap between adjacent Schwann cells

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19
Q

What are the 4 types of sensory receptors, and where can they be found?

A

Mechanoreceptor- skin (Pacinian corpuscle)
Chemoreceptor- nose (olfactory receptor)
Photoreceptor- eye (cone cells)
Thermoreceptor- tongue (end-bulbs of Krause)

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20
Q

How do action potentials propagate?

A

1) There are more positively charged ions outside of the cell, so the membrane is polarised
2) Stimulus causes an action potential, depolarising the membrane
3) Influx of Na+ ions causes channels to open a little further along the axon, causing more depolarisation. At the start of the axon, V-G NA+ channels close and K+ ions leave down an electrochemical gradient
4) The start of the membrane becomes repolarised while the action potential is propagated along the axon
5) The membrane begins to return to its resting potential to receive another impulse

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21
Q

What is the time called when the axon cannot be excited again?

A

The refractory period

22
Q

Why is the refractory period important?

A

Ensures impulses only travel forwards and are distinct from each other

23
Q

What is saltatory conduction?

A

When the action potential jumps from one node of Ranvier to another. This is because the membrane only has to be depolarised at the nodes. More energy efficient

24
Q

What factors affect the speed of action potential transmission?

A

• Myelination
• Axon diameter (Bigger=faster, as there is less resistance)
• Temperature

25
What is the all or nothing principle?
The size of the stimulus does not affect the size of the action potential. It does affect the number of action potentials
26
What is the synaptic knob, and what are its features?
• The end of a presynaptic neurone • Contains many mitochondria and endoplasmic reticulum to create neurotransmitters
27
What are the two types of neurotransmitter?
• Excitatory- Cause depolarisation in the postsynaptic membrane if threshold is reached • Inhibitory- Cause hyper polarisation of the postsynaptic membrane, preventing an action potential (E.g. GABA in the brain)
28
How is an impulse transmitted across synapses?
1) Action potential reaches presynaptic knob 2) Depolarisation causes Ca2+ channels to open 3) This causes neurotransmitters carried in synaptic vesicles to leave the knob by exocytosis 4) Neurotransmitter diffuses along synaptic cleft and binds to the receptor molecule on the postsynaptic membrane 5) Na+ channels open 6) Action potential is created
29
What type of synapse uses acetylcholine as a neurotransmitter?
Cholinergic synapses
30
What happens to acetylcholine after binding to its receptor?
It is hydrolysed by acetylcholinesterase, creating choline and ethanoic acid. This is taken back to the presynaptic knob to be used to create acetylcholine
31
Why are synapses important?
• Allow unidirectionality • Allow one impulse to be converted to many, and vice versa
32
What are the two types of summation?
Spatial summation Temporal summation
33
What is the somatic nervous system?
Under conscious control
34
What is the autonomic nervous system?
Works under subconscious control Split into sympathetic and parasympathetic nervous system
35
What does the sympathetic nervous system do?
Stimulates "fight or flight" responses
36
What does the parasympathetic nervous system do?
Stimulates the "rest and digest" responses
37
What happens in the knee jerk reflex?
• When the leg is tapped just below the kneecap, the patellar tendon stretches, acting as a stimulus • Used to keep balance
38
What happens in the blinking reflex?
Eyelids blink when the cornea is touched, to protect it
39
What are the three types of muscle?
Skeletal Cardiac Involuntary
40
What are features of skeletal muscle?
• Striated fibres • Controlled consciously • Regularly arranged • Rapid, short length of contraction • Fibres are tubular and multinucleated
41
What are features of cardiac muscle?
• Fainter striated fibres • Involuntary control • Branched cells • Intermediate contraction speed and length • Uninucleated
42
What are features of involuntary muscle?
•Non striated fibres • Involuntary control • No regular arrangement • Slow contraction speed, long length of contraction • Spindle shaped and uninucleated
43
What are myofibrils?
Long organelles specialised for contraction (contain sarcomeres)
44
What is a light band in a sarcomere?
Where actin and myosin don't overlap (only actin)
45
What is a dark band in a sarcomere?
Presence of thick myosin filaments
46
What is a z-line in a sarcomere?
Found at the centre of each light band
47
What is a H-zone in a sarcomere?
Centre of dark band where only myosin filaments are present
48
What is a sarcolemma?
The postsynaptic membrane at a neuromuscular junction
49
What is the sarcoplasm?
The cytoplasm of a muscle fibre
50
What are t-tubules?
Parts of the sarcolemma which fold inwards, to help spread electrical impulses throughout the sarcoplasm