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A Level Biology > Coordination > Flashcards

Coordination Flashcards

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1
Q

Describe the transmission of nerve impulses

A

The signals are very brief changes in the distribution of electrical charges across the cell surface membrane called action potentials caused by very rapid movement of Na+ and K+ ions into and out of the axon.

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2
Q

What is meant by Resting potential?

A

it is the difference in electrical potential that is maintained across a neurone when it is not transmitting an action potential it is normally about -70 mV inside and maintained by a Na+ and K+ pump.

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3
Q

What causes the presence of a resting potential?

A

Because of an overall excess of negative ions inside the the membrane compared to the outside.

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4
Q

Why is there a build up of negative ions inside the membrane than the outside?

A
  1. More protein channels for K+
  2. Negative ions attract K+
  3. K+ is mainly open but Na+ will only open when a certain potential difference is reached.
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5
Q

How does sodium move back into the membrane?

A

By an electrochemical gradient

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6
Q

How is the electrochemical gradient built up?

A
  1. Steep concentration gradient

2. Negative ions inside that attract the Na+

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7
Q

What is the purpose of a coordination system in most mammals?

A
  1. To coordinate the regulation of substances

2. To change the activity of some part of the organism in response to an external stimulus.

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8
Q

What are the 2 types of information transfer?

What is their mode of transmission?

A
  1. Nerves -> Electrical impulses

2. Blood -> Hormones

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9
Q

What are the two main parts of the mammalian nervous system?

A

A Central nervous system a peripheral nervous system.

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10
Q

What is the role of Neurones?

A

They coordinate the activities between sensory receptors and effectors

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11
Q

What are the 3 types of neurones?

What to they coordinate?

A
  1. Sensory neurones: Receptors and CNS
  2. Intermediate/ Relay neurone: Sensory and Motor neurones.
  3. Motor: CNS and effectors
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12
Q

What are dendrites?

A

They are a short cytoplasmic process of a neurone that receives nerve impulses from other neurons.

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13
Q

What is the Axon?

A

They are the long cytoplasmic process of a neurone.

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14
Q

Name the parts of a motor neurone.

A
  1. Nucleus
  2. Dendrite
  3. Cytoplasm containing many mitochondria and an extensive endoplasmic reticulum.
  4. Schwann cell
  5. Nucleus of a Schwann cell
  6. Synaptic knob
  7. Terminal branches
  8. Axon
  9. Node of Ranvier
  10. Cell body
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15
Q

What is the role of the dendrite?

A

It creates a larger surface area for other neurones

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16
Q

What is the role of the Axon?

A

it conducts nerve impulses over a long distance.

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17
Q

What is Myelin?

A

it is a substance that surrounds many axons, made up of many layers of the cell surface membranes of Schwann cells.

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18
Q

What are Schwann cells?

A

They are a cell that is in close association with a neuron, whose cell surface membrane wraps around the axon of the neuron to form a myelin sheath.

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19
Q

What is the Myelin sheath?

What is the role of the myelin sheath?

A

It is the enclosing sheath made largely of lipid, together with some protein.
The sheath affects the speed of conduction.

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20
Q

What are Nodes of Ranvier?

A

A Short gap in the sheath surrounding an axon.

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21
Q

What is a Reflex arc?

A

It is the pathway taken by an action potential leading to a reflect action; the action potential is generated in a receptor, passes along a sensory neurone into the brain or spinal cord, and then along a motor neurone.

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22
Q

What is a reflex action?

A

It is a fast automatic response to a stimulus; reflex actions may be innate (inborn) or learned (conditioned).

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23
Q

How is a reflex action coordinated?

A
  1. Neurones takes part of the impulse directly to the brain.
  2. The effector neurone responds to the stimulus before there is any voluntary response involving the conscious regions of the brain.
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24
Q

Describe the movement of ions during the generation of an action potential.

A

3 Na+ is moved out for every 2K+ brought inside the axon. This is done using proteins that use energy from the hydrolysis of ATP.

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25
Q

What is an electrochemical gradient?

A

A gradient across a cell surface membrane that involves both a difference in concentrations and a potential difference.

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26
Q

What are action potentials?

A

They are brief changes in the potential difference across a cell surface membrane of a neuron and muscle cells caused by the inward movement of sodium ions followed by the outward movement of potassium ions, it rapidly travels along the length of a neurone.

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27
Q

What is the change in the electrical potential of a cell surface membrane during an action potential?
What caused this change?

A

It changes from -70 to 30 mV

It is caused by a change in permeability of the membrane to Na+ and K+

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28
Q

What are voltage-gated ion channels?

A

They are a channel protein through in a cell membrane that opens and closes in response to an electrical potential across the membrane.

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29
Q

How is the positive charge inside the axon generated n during an action potential?

A

The movement of sodium causes a depolarization, which triggers some more channels to open so that more sodium ions can enter.

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30
Q

When do action potentials occur?

A

When a threshold voltage is reached - a pd of -50 to -60v

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31
Q

What is repolarization?

A

returning of the potential difference across the cell surface membrane of neurone/ muscle cell to normal following the depolarization of an action potential.

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32
Q

How does an action potential transmit across the membrane?

A
  • Neurons have to transmit impulses along with themselves.
  • An action potential at any point in an axon’s cell surface membrane triggers the production of an action potential on either side of it.
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33
Q

What is the refractory period of an action potential?

A

A period of time during which a neurone is recovering from an action potential and during which another actional potential cannot be generated.

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34
Q

What are the consequences of a refractory period?

A
  1. Action Potentials are discrete
  2. There is a minimum time between action potentials
  3. Determines the frequency
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35
Q

How does the action potential generated differ between strong and weak stimulus?

A

The frequency

A strong stimulus is likely to also stimulate more neurons.

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36
Q

How does the brain determine the nature of the impulse? e.g light sound, heat etc.

A

It depends on the position from which the impulse is coming from.

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37
Q

How does a myelinated neurone differ from an unmyelinated neurone?
Why does this difference occur?

A
  • Myelinated neurones have action potentials that travel much faster than that of an unmyelinated neurone.
  • Action potentials can only occur at the nodes of Ranvier, where all the channel proteins and pump proteins are concentrated.
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38
Q

What is saltatory conduction?

A

it is the pathway of an electrical impulse along a myelinated neurone, where the action potential appears to jump from one node of Ranvier to another..

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39
Q

what is a receptor cell?

A

It is a cell that is sensitive to a change in the environment and will produce an action potential as a result of that stimulus.

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40
Q

What is a chemoreceptor?

A

It is a receptor that detects chemical stimuli; Chemorecepttors are found in the tongue, nose and in blood vessels where they detect oxygen and carbon dioxide concnetrations.

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41
Q

Describe the presence of receptors in the tongue.

A

The tongue has papillae that can contain from 50 - 100 chemicals to give different sensations.

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42
Q

Describe how salt is detected in the tongue.

A
  1. Na + moves in and depolarizes, building up a receptor potential.
  2. When the voltage is high enough, the calcium ion channel open
  3. They lead to the exocytosis of vesicles
  4. The Neurotransmitter stimulate an action potential.
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43
Q

Describe how sweet is detected in the tongue.

A
  1. Receptors stimulate an action potential
  2. Enzymes produce cyclic AMP
  3. Enzyme cascade stimulate closure of the K+ ion channels
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44
Q

What is the All or nothing law?

A

It is a law that states that neurones and muscle cells only transmit impulses if the initial stimulus is sufficient to increase membrane potential above a certain threshold.

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45
Q

What is a synaptic cleft?

A

it is a very small gap between the neurons of a synapse.

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46
Q

What is a synapse?

A

It is a point at which two neurones meet but do not touch; the synapse is made of the end of presynapic neurones, the synaptic cleft and the end of the post-synaptic cleft.

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47
Q

What is the neurotransmitter substance?

A

It is a chemical that is released from a presynaptic neurone when an action potential arrives and then diffuses across the synaptic cleft and may initiate an action potential in the postsynaptic cleft.

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48
Q

What is the sequence of a transmission in a synapse?

A
  1. Action potential at the presynaptic neuron
  2. Transmitter substance diffuses to the post-synaptic neurone
  3. Depolarization occurs if the impulse is greater than the threshold voltage.
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49
Q

What are some neurotransmitter substances that are found throughout the body?

A
  1. Noradrenaline

2. Acetylcholine: Found in the presynaptic neurone of the neuromuscular joints.

50
Q

What are some neurotransmitter substances found in the brain?

A
  1. Dopamine
  2. Glutamic acid
  3. Gamma-aminobutyric acid
51
Q

What stimulates the vesicles to move to the synapse?

A

The arrival of the action potential stimulates both sodium ion voltage-gated channels and calcium ion channels which stimulate vesicles containing ACh to move and release

52
Q

How do chemically gated ion channels like Na+ open?

A

The binding of Ach at the postsynaptic receptors cause a change in chape that cause Na+ ion channels to open.

53
Q

How is further polarization prevented?

How is the Ach regenerated?

A

Acetylcholinesterase hydrolyses Ach to produce acetate and choline.
Ach is reformed with Acetyl Coenzyme A.

54
Q

What are the roles of synapses?

A
  1. Ensures one-way transmission
  2. Synapses allow integration of impulses
  3. Synapses allow the interconnection of nerve pathways
  4. Memory and Learning
55
Q

How d synapses allow the integration of impulses?

A

A synapse can divide into many relays

Since the threshold is not reached, the beam won’t be sensually overloaded.

56
Q

How do synapses allow for the interconnection of a nerve pathway?

A
  • One stimulus can go through many relay neurones o stimulate many effectors.
  • One neurone integrate the information coming from many different parts of the body.
57
Q

How do synapses help with memory and learning?

A

New synapses form that link neuron that passes information.

58
Q

What is a striated muscle?

A

It is a type of muscle tissue in skeletal muscles; the muscle fibres have regular striations that can be seen under a light microscope.

59
Q

What are the features of a striated muscle?

A
  1. They are attached to a skeleton

2. They are neurogenic: they only contract when there is an impulse from a motor neurone.

60
Q

What is a smooth muscle?

A

This is the type of muscle found in the walls of blood vessels, trachea, bronchi, and bronchioles, alimentary canals and ureter. the muscle cells are not striated.

61
Q

Describe the cardiac muscle.

A
  1. Stripes
  2. Uninucleate + intercalated discs
  3. its shorter + branches
  4. Myofibrils
  5. Heart
  6. Myogenic
62
Q

Describe striated muscles.

A
  1. Stripes
  2. Multinucleate
  3. Long and unbranched
  4. Myofibrils
  5. Skeleton
  6. Neurogenic
63
Q

Describe smooth muscles.

A
  1. No striations
  2. Uninucleate
  3. Long, unbranched and tapered
  4. Myofibrils
  5. Neurogenic
64
Q

What are transverse system tubules?

A

They are an infolding of the sarcolemma that goes deep into muscle fibre.

65
Q

What are Myofibrils?

What are they made of?

A

It is one of many cylindrical bundles of thick and thin filaments inside a muscle.
Mitochondria are tightly packed in it.
it is made of smaller components called filaments, which are made of proteins.

66
Q

What is myosin?

A

it is the contractile protein that makes up the thick filaments in a striated muscle.

67
Q

What is actin?

A

it is the protein that makes up the thin filaments in a striated muscle.

68
Q

What are the different types of bands in a striates muscle?

A 
A: (only thick) + (Thick + thin) 
I: No thick filaments
H: only thick
Z: attaches actin 
M: attaches myosin
69
Q

What is a sarcomere?

A

it is the part of the myofibril between the 2 discs.

70
Q

What are the thick filaments composed of?

A

Myosin, which is a fibrous protein with a globular head, which points away from the M line.

71
Q

What are the thin filaments composed of?

A

It has many actin molecules -globular proteins arranged in along chain.

72
Q

What is tropomyosin?

A

it is a fibrous protein that is part of the thin filaments in myofibrils in a striated muscle.

73
Q

What is troponin?

A

A calcium-binding protein that is part of the thin filaments in myofibrils in a striated muscle.

74
Q

What is the sliding filament model of muscle contraction?

A

The Z discs pull closer and myofibrils shorten

75
Q

Where does the energy for muscle contraction come from?

A

It comes from ATP which is hydrolysed at myosin heads.

76
Q

How do the myosin heads move?

Why does it occur?

A

The Ca2+ released from SR and binds to troponin, causing it to change shape.
This exposes the actin-binding sites for myosin.

77
Q

Describe the process of muscle contraction.

A
  1. The Troponin moves away.
  2. The myosin heads bind to the actin-binding site forming cross-bridges.
  3. The Mysoin heads tilt, pulling the actin towards the centre of the sarcomere.
  4. ATP hydrolysis provides energy to let go
  5. This process continues. \
78
Q

Describe the transmittance of an impulse that will stimulate a muscle to contract.

A

Pre synaptic neuron -> acetyl choline -> neuromuscular junction -> Receptor protein -> Post synaptic neurone
ion channels open -> Na+ diffuses in -> actionpotential generated.

79
Q

How does the arrival of the impulse stimulate troponin to move?

A

Ca2+ is secreted ->binds to troponin / tropomycin -> changes shape

80
Q

How do the sarcomeres return to their original shape?

A

Each skeletal muscle has an antagonistic muscle that restores the sarcomeres t their original lengths. e.g the bicep has the tricep.

81
Q

The reactions of creatine and creatine phosphate

A

When ATP is needed:
- creatine phosphate + ADP -> creatine + ATP
When ATP demand is less:
- creatine + ATP -> creatine phosphate + ADP
If the Demand is too high:
creatine -> creatinie which is secreted in the urine.

82
Q

Hormone definition

A

A substance secreted by an endocrine gland that is carried in blood plasma to another part of the body, where it has an effect.

83
Q

Movement of peptide and steroid hormones across the bilayer.

A

Peptides are lipids that cannot cross the bilayer -> Binds to receptor
Steroid hormones are lipid-soluble and can cross.

84
Q

Menstrual cycle

A

The changes that occur in the ovary on the uterus involving ovulations and the breakdown and loss of the lining of the uterus.

85
Q

What are the stages that lead to ovulation?

A 
1. A potential female gamete starts to develop 
2, Primary follicle
3. Secndary follicle
4. Ovarian/Gracian 
5. Ovulation
6. Corpus luteum
86
Q

Stages of the uterine cycle

A
  1. Uterus loses endometrium
  2. endometrium develops & ovarian follicle produced
  3. Further development of the endometrium & Ovulation
  4. Endometrium is maintained until the corpus luteum develops & degenerates
87
Q

How is the menstrual cycle coordinated?

A

by glycoprotein hormones that are released by the anterior pituitary gland

88
Q

FSH

A

Glycoprotein hormone secreted by the anterior pituitary gland to stimulate the development of follicles in the ovary

89
Q

LH

A

A glycoprotein hormone that is secreted by the anterior pituitary gland to stimulate ovulation and the development of the corpus luteum.

90
Q

Oestrogen

A

Asteroid hormone secreted by the follicles in the ovary; used in some contraceptive pills

91
Q

Progesterone

A

A Steroid hormone secreted by the corpus luteum in the ovary after ovulation used in the corpus luteum

92
Q

Describe the action of hormones in the menstrual cycle.

A
  1. LH and FSH are secreted
  2. Oestrogen is stimulated which causes negative feedback on LH and FSH
  3. When Oestrogen is very high, LH increases dramatically and FSH also increases. This causes ovulation and the production of a corpus luteum
  4. LH and FH maintain the uterus
93
Q

Contraception

A

Preventing fertilization when sexual intercourse takes place.

94
Q

Antiimplantation methods

A
  1. IUDs

2. Morning after pills

95
Q

Birth control pill

A

A pill that contains oestrogen and/or progesterone to prevent ovulation

96
Q

Is ovulation suppressed using a Birth control pill?

A

synthetic hormones suppress ovulation.

Oestrogen and Progesterone suppress FSH and LH

97
Q

Prescription of Birth control pills.

A

One pill daily for 21 days and stop for 7 days

98
Q

What do birth control pills with only progesterone do?

A

They allow ovulation but prevents the sperm from fertilizing and it increases cervical mucus to reduce penetration.

99
Q

Why is the morning after pill used?

A

It is used after sexual intercourse

100
Q

What is contained in the morning after pill?

what does this do?

A

Synthetic progesterone:

i. Prevents sperm from reaching & fertilizing an egg
ii. Prevents implantation

101
Q

What causes depolarization in plants?

A

The outflow of Cl- ions

102
Q

How do action potential travel in the cell membrane?

A

Action potentials are thought to bring about a metabolic change in the plant

103
Q

Describe the adaptations o the Venus flytrap?

A
  • Midrib with two lobes
  • Lobes are convex but can be stimulated to become convex
  • It has stiff sensory hairs
  • Has stiff hairs that interlock the insect
104
Q

What is a plant growth regulator?

A

it is any chemical produced in plants that influence their growth and development e.g auxins, gibberellins, cytokines and abscisic acid.

105
Q

What is auxin?

A

It influences growth and elongation -> length

106
Q

What are gibberellins?

A

They allow seed germination and stem elongation

107
Q

What is abscisic acid?

A

It controls the response of plants to environmental stresses.

108
Q

How are auxins synthesised and transported?

A

In growing tips

Active transport

109
Q

Stages of plant growth

Which stage are auxins involved in?

A
  1. Mitosis
  2. Elonation by Absorption of water
  3. Cell differentiation

Auxins are involved in elongation.

110
Q

How does elongation happen?

A
  1. Auxin binds to the receptor
  2. ATPase pumps H+ across the cell membrane into the cell wall
  3. Explansins are activated by the decrease in pH
  4. Explansins loosen linkages between microfibrils
  5. Microfibrils move past each other and expand.
111
Q

What are gibberellins?

A

They are a plant growth hormone that regulates plant height (stem growth) and stimulates seed germination; a lack of gibberellins causes dwarfness.

112
Q

How do gibberellins work?

A

Active gibberellins cause cell division which causes cell elongation which then causes growth.

113
Q

Why does dwarfness happen?

A

Mutations cause gibberellins to become inactive

114
Q

What is Dormancy?

A

The state of suspended animation - slowed metabolism survival in adverse conditions

115
Q

What is the endosperm?

A

It is a tissue that stores food in some seeds, such as cereal grains.

116
Q

What is the Aleurone layer?

A

It is a layer of tissues around the endosperm that synthesizes amylase during germination

117
Q

How do embryos get energy?

When in this process are the gibberellins released?

A
  1. Absorption of water by the embryo
  2. Gibberellins are released
  3. Gibberellins diffuse to the aleurone layer and stimulate the cells to synthesize amylase.
  4. Amylase hydrolysis starch
  5. Maltose produced
  6. Maltose -> Glucose
  7. Glucose can be respired.
118
Q

How do Gibberellins cause these effects?

A

By regulating genes that are involved in the synthesis of amylase.

119
Q

Explain why the membrane of the neurone depolarizes when the Na+/K+ pump stops working.

A
  • The resting potential is not maintained
  • During resting potential, the membrane is polarized
  • Na+ moves into the neurone
  • Outward diffusion of K+ is limited
  • They move in through non-voltage gets channels
120
Q

Suggest why calcium ions flood the neurone when the Na+/K+ pumps stop working

A
  • Voltage-gated calcium ion channels open.

- Calcium ions move in by diffusion

A Level Biology (6 decks)

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