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Biology 6th Form OCR A (missing exchange systems) > Module 5: Neuronal Communication > Flashcards

Module 5: Neuronal Communication Flashcards

1
Q

What stage of the cell cycle are neurones in?

A

G0.

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2
Q

What are the key features of a Neurone?

A

Cell Body - Location of DNA and most organelles
Dendrons - Input synapses send impulses into cell body
Axons - send impulses away from cell body.

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3
Q

Myelinated axons allow for what kind of conduction?

A

Saltatory conduction.

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4
Q

What is the structure of a typical motor neurone?:

A

Dendrites lead into a cell body, containing a nucleus, high mitochondria levels and endoplamsic reticulum. An axon myelinated with Schwann cells leads to a synaptic knob, containing more organelles.

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5
Q

Why do neurones need high mitochondria levels?

A

To carry out respiration to provide energy for endocytosis and active transports across the membrane.

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6
Q

Why do neurones have high amounts of endoplasmic reticulum and a golgi complex?

A

To synthesise neurotransmitters for exocytosis.

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7
Q

Nodes of Ranvier:

A

2-3μm size at 1-3mm intervals. They are interruptions of the myelin sheathe - location of ion channels.

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8
Q

Myelin Sheathe:

A

Many Layers of Schwann cell membranes, rich in lipoproteins and myelin. Electrically insulate axons. Schwann cells separated by nodes of Ranvier.

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9
Q

A nerve is a bundle of ______

A

A nerve is a bundle of neurones.

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10
Q

Characteristics of a reflex:

A

Unconscious, Very fast, protect organism from harm.

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11
Q

Perceived Intensity of stimulus is determined by:

A

Frequency of action potentials.

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12
Q

Where are Pacinian Corpuscles found?

A

Dermis of the skin

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13
Q

What do Pacinian Corpuscles detect?

A

Pressure (It is a mechanoreceptor)

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14
Q

What do Pacinian Corpuscles detect?

A

Pressure (It is a mechanoreceptor)

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15
Q

What are the 4 types of receptors in terms of type of stimuli?

A

Thermoreceptors, Chemoreceptors, Mechanoreceptors, Photoreceptors.

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16
Q

What is the type of channel on the neurone ending of at the corpuscle?

A

Stretch Mediated Na+ channels.

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17
Q

What does the intensity of a stimulus effect:

A

It effects the magnitude of the of generator potential.

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18
Q

What are the 3 types of receptors in terms of their environments?

A

Exteroceptors: stimuli from external environment
Enteroceptors: stimuli from internal environment
Proprioceptors: respond to tension within tendons and muscles.

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19
Q

What are the 2 types of receptors (types of sense)

A

Rapidly Adapting: Short signal - pain

Slowly Adapting: Constant Sense

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20
Q

How do Pacinian Corpuscles transduce pressure?

A

The pressure of the stimuli opens stretch mediated Na+ channels, causes diffusion of Na+ ions down the electrochemical gradient from the surrounding tissue into the cell. This depolarises the neurone membrane, generating and generator potential, if this potential exceeds threshold an action potential is produced and the impulse travels through a dendron.

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21
Q

Structure of Pacinian corpuscle:

A

Single myelinated sensory nerve fibre, enclosed in a multi-layered connective tissue capsule

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22
Q

What is the purpose of the fluid within the connective tissue capsule surrounding the Pacinian Corpuscle?

A

Greater sensitivity to changes in pressure.

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23
Q

Resting Potential Value?

A

-70mv

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24
Q

Action Potential Value:

A

+40mv

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25
Gated Channels:
diffusion of substance is dependent of particular membrane-affecting agent to either open/close the channel. Often ion specific.
26
Voltage Gated Channels
Voltage changes to the potential difference across the membrane alter channels tertiary structure and 3D shape. They're located on the axon of neurones and are utilised for the generation and propagation of action potentials.
27
Mechanically Gated Channels:
Located on the dendrites of sensory neurones and sensory receptor cells. Opening/closing dependent on the distension of the cell membrane from vibrations or changes in pressure.
28
Axoplasm:
Cytoplasm of axon.
29
Ligand Gated Channels:
Found at cell bodies or dendrites - hormones and neurotransmitters modify the tertiary structure and shape of channels for normal cell maintenance.
30
What is a nerve impulse?
An action potential moving across an axon as a unidirectional-wave of depolarisation.
31
At rest the outside of the membrane is more _______ charged than the the inside. Therefore the membrane is ____.
At rest the outside of the membrane is more positively charged than the the inside. Therefore the membrane is polarised.
32
Between impulses the resting potential is _______ restored and maintained by the axon.
Between impulses the resting potential is actively restored and maintained by the axon.
33
Describe and Explain how a resting potential is established and how it is maintained in a sensory neurone.
3Na+ and 2K+ are actively transported across the membrane by a sodium-potassium pump. the 3Na+ ions are transported into the surrounding tissue fluid. The 2K+ ions are transported into the sensory neurone. The cell has a high K+ permeability, because of the high number of K+ channels, causing K+ ions to leave the cell. The Cell is much less permeable to Na+ ions and-so there is little to no diffusion into the cell. The voltage ion channels remain closed.
34
What causes the refractory period (neurones)?
Hyperpolarisation of the membrane, periodically inactivating Na+ channels.
35
Neurone Depolarisation:
Depolarisation of previous section of axon/dendron causes voltage gated Na+ channels to open, increasing the membranes permeability to Na+. Na+ diffuses into the cytoplasm, making the cell less negative. This change is p.d causes further Na+ channels to open in a positive feedback system. Once at +40mv the voltage gated Na+ channels close and K+ opens. Repolarisation occurs as K+ diffuses out of the cell. this continues until hyperpolarisation causes the voltage-gated K+ channels to close. Resting potential then re-established by the pump and facilitated diffusion.
36
What is the importance of the refractory period (neurones)?
- Causes action potentials to be discrete/ non-overlapping | - Prevents impulses from travelling backwards.
37
3 types of neurone:
Sensory Relay Motor
38
Relay Neurones:
Transmit impulses between neurones.
39
Sensory Neurone:
Transmits an impulse from a sensory receptor to a relay neurone, motor neurone, or the brain.
40
Motor Neurone:
Transmits an impulse from a relay or sensory neurone to an effector.
41
Purpose of Reflexes:
Reduce severity of injury Allows brain to be occupied with complex issues Extremely fast Aid posture and digestion.
42
How does Saltatory conduction work?
Sodium ion channels are only located at the Nodes of Ranvier. This creates longer localised circuits, reducing the number of ion channels that are needed to open and close.
43
Advantages of saltatory conduction:
Faster and more energy efficient (By reducing the amount of repolarisation required.)
44
Synaptic Bulb:
Swollen end of a presynaptic neurone containing mitochondria, endoplasmic reticulum, and synaptic vessicles.
45
What do synaptic vesicles contain?
Neurotransmitters.
46
What is a receptor in a synapse?
A specific protein molecules on post-synaptic membranes, attached to a ligand-gated ion channel, that a neurotransmitter binds to.
47
What is convergence at a synapse?
Single post synaptic neurone for multiple presynaptic neurones.
48
What is divergence at a synapse?
A single presynaptic neurone to multiple post synaptic neurones.
49
How do synapses ensure unidirectional impulses.
Receptors for neurotransmitters are only located on the postsynaptic neurone.
50
How do synapses 'filter out' low level stimuli?
Temporal and spatial summation.
51
What are the two types of neurotransmitter?
Excitatory and Inhibitory.
52
What do Excitatory Neurotransmitters do?
- Cause depolarisation of postsynaptic neurone. | - > contributes towards generator potential -> helps reach threshold. -> increases likelihood of response.
53
What do inhibitory Neurotransmitters do?
Cause the hyperpolarisation of the post synaptic membrane, obstructs triggering of action potential/ reduces generator potential -> decreases likelihood of response.
54
At the presynaptic neurone what ions diffuse and where to?
Ca2+ ions diffuse into the synaptic knob.
55
Outline the role of synapses in the nervous system:
Synapses: - allow communication between neurones. - Filter out smaller stimuli to prevent overstimulation - Determine the intensity of a stimulus through summation.
56
What enzyme is found in the synaptic cleft?
Esterase
57
5 Stages at the Synapse:
``` Calcium ion channels open: Neurotransmitter Release: Sodium ion channels open: Depolarisation: Hydrolysis pf Acetylcholine: ```
58
Summation:
Combination of graded potentials in the post synaptic membrane.
59
Agonists:
Drugs that stimulate the nervous system.
60
Antagonists:
Drugs that inhibit the nervous system.
61
Central Nervous System:
Brain and Spinal Chord | - Relay neurones
62
Peripheral Nervous System:
Everything else -> peripheral nerves, sensory and motor neurones
63
Sensory Division:
64
Sensory Division:
Part of PNS that detects stimulus, conducting signals from receptors to the CNS.
65
Motor Division:
Motor neurones - from CNS to effectors. | Made up of autonomic + somatic
66
Somatic Nervous System:
Controls voluntary movement.
67
Autonomic Nervous System:
Involuntary Response- | Made up of sympathetic and parasympathetic division.
68
Sympathetic Division:
Mobilises body systems in 'Fight or flight' | -Noradrenaline
69
Parasympathetic Division:
Conserve energy Relaxation -Acetylcholine
70
Medulla oblongata:
Part of the brainstem responsible for autonomic activity. This includes the regulation of body activities.
71
Cerebral Cortex:
Two hemispheres with a range of functions. | e.g. Senses, language, memory and behaviour.
72
Cerebellum:
Controls balance and coordination. | Coordinates movement - makes it smooth.
73
Spinal Chord:
Consists of many bundles of neurones carrying information between the brain and the body.
74
In the brain, where is white and grey matter located?
White matter is located on the inside of the brain, made up of myelinated axons connecting regions together. Grey matter is located on the outside of the brain, made up of unmyelinated nerve fibres.
75
What happens at Grey matter in the brain?
Information is processed.
76
Hypothalamus and pituitary glands are types of ______ glands.
Neuroendocrine Glands
77
Neuroendocrine Glands:
Link nervous and endocrine systems.
78
Roles of the pituitary gland:
``` Metabolism Adult development Reproduction Growth Homeostasis ```
79
Ganglione:
Swelling of spinal chord.
80
How to identify sympathetic nervous response on a diagram:
Short preganglionic neurone + Long postganglionic neurone.
81
How to identify parasympathetic nervous response on a diagram:
Long preganglionic neurone + Short postganglionic neurone.
82
Posterior Pituitary Gland:
Stores and releases hormones produced by the hypothalamus.
83
Anterior Pituitary Gland:
produces six hormones including FSH.
84
Examples of Parasympathetic Division:
Constrict Pupils, decrease Heartbeat, Constrict Airways, Stimulate Stomach Activity, inhibit glucose release.
85
Examples of Sympathetic Division:
Dilate pupils, Relax Airways, Increased Heartbeat, Secrete Adrenaline, inhibit stomach activity.
86
Myosin:
Fibrous protein with globular heads that are hinged to allow for movement. One globular head that is the binding site of ATP and Actin.
87
Actin:
Have binding sites for myosin heads. The binding sites are blocked by tropomyosin which is held in place by troponin.
88
The arrival of an action potential in a muscle fibre causes __________:
Opening of the Ca2+ channels in the sarcoplasmic reticulum, causing the Ca2+ to diffuse into the muscle fibre.
89
What does Ca2+ do in muscle fibre?
Ca2+ binds to troponin molecules, causing them to change shape and move tropomyosin to a different position.
90
On a myofibril, what is the result of the movement of tropomyosin on actin?
The myosin binding sites are exposed.
91
When actin's myosin binding sites are free what binds to it?
Extended myosin heads bind to the actin and form a cross-bridge.
92
When myosin heads bind to actin what is released and what does this cause?
ADP and Pi are released, causing the myosin heads to revert to their original position, pulling the actin filaments towards the centre of the sarcomere.
93
Once ADP and Pi have been released from each myosin head what binds to the myosin heads?
ATP
94
How do Ca2+ ions re-enter the sarcoplasmic reticulum?
They are actively pumped. (Active transport)
95
During muscle contraction, once Ca2+ ions have been pumped back into the sarcoplasmic reticulum what happens?
The Ca2+ unbinds from troponin, moving the tropomyosin and blocking the binding site.
96
What kind of enzymes do Myosin heads act like?
ATPase, hydrolysing ATP into ADP and Pi
97
What is the Sarcolemma?
The sarcolemma is the plasma membrane of the muscle cell
98
What happens to myosin heads when they reattach to ATP?
The myosin heads detach from the actin.
99
Sarcomere Shortening:
Repeated reorientation of the myosin heads drags actin filaments towards centre of sarcomere. This pulls z-lines closer together. As sarcomeres become shorter, muscle fibre contracts.
100
What is the darker region in a sarcomere?
The a band where actin and myosin overlap.
101
What are the peripheral lighter regions on a sarcomere?
The I bands, where actin is present but not myosin.
102
What is the H zone?
The lighter region within the A band, where only myosin is present.
103
What are the Z- lines on a sarcomere?
The areas which the actin is attached to.
104
Cardiac Muscles:
Specialised Striated - branched + simultaneous contraction - Involuntary - intermediate speed and length - Uni-nucleated fibres.
105
Skeletal Muscles:
Striated - Voluntary - regular arrangement and unidirectional contraction - rapid contraction - short contraction length - tubular and multinucleated fibres.
106
Involuntary Muscles: (e.g smooth muscle)
Non-striated - no regular arrangement - involuntary - slow contraction - contraction length varies - spindle shaped and uninucleated -
107
What is the name of the cross bridges between Actin and Myosin filaments?
Actinomyosin
108
Source of ATP that doesn't require respiration:
Creatine Phosphate.

Biology 6th Form OCR A (missing exchange systems) (27 decks)

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