1
Q
Why do animals respond to changes in the external environment?
A
To increase their chance of survival by avoiding harmful environments e.g places that are too hot or cold.
2
Q
Why do animals respond to changes in their internal environment?
A
To make sure that conditions are always optimal for metabolism. Plants also do this
3
Q
What is a stimulus?
A
Any change in the internal or external environment
4
Q
What are some examples of stimuli?
A
Internal:
-Carbon dioxide concentration
-Oxygen concentration
-Glucose concentration
External:
-Light
-Temperature
-Sound
-Humidity
5
Q
How do plants respond to stimuli?
A
Chemical responses
6
Q
How do animals respond to stimuli?
A
Electrical impulses
7
Q
What detect stimuli?
A
Receptors
8
Q
What are receptors?
A
They are specific to each stimuli
9
Q
What are effectors?
A
Effector are cells that bring about a response to a stimulus to produce an effect. Effectors include muscle cells and cells in glands
10
Q
What is cell signalling?
A
Where adjacent cells or distant cells communicate with each other
11
Q
What is the hormonal system?
A
This system works by releasing chemicals called hormones which travel in the blood and act as signals to distant cells. Cell surface receptors then recognise the chemicals involved in cell signalling
12
Q
What are neurotransmitters?
A
Chemicals secreted which send signals to adjacent cells
13
Q
What is a transducer?
A
A cell that converts another type of energy into an electrical impulse
14
Q
What are the types of cell signalling?
A
-Endocrine secretion
-Neurosecretion
-Paracrine secretion
-Nerve cells
15
Q
What is endocrine secretion?
A
Where endocrine glands (glands that release hormones) release hormones directly into the bloodstream where they travel to target cells
16
Q
What is neurosecretion?
A
Where special neurones (nerve cells) secrete hormones directly into the bloodstream. E.g hormones released from neurosecretory cells including the anti-diuretic hormone and oxytocin
17
Q
What is paracrine secretion?
A
Where chemicals diffuse short distances to adjacent cells
18
Q
What is nerve cells in cell signalling?
A
They use an electrical impulse to travel large distances but release chemicals where they terminate
19
Q
Explain the pathway of nervous communication
A
Stimulus > receptors > sensory neurone > CNS > motor neurone > effectors > response
20
Q
When are relay neurones used?
A
In rapid responses such as reflex arcs because they bypass the conscious brain and just goes throughbthe spinal cord
21
Q
What is a nerve cell usually refered to as?
A
A neurone
22
Q
What is a bundle of neurones usually called?
A
A nerve
23
Q
What is the central nervous system?
A
Composed of the brain and spinal cord
24
Q
What is the peripheral nervous system?
A
Consists of all the neurones which bring infomation to the CNS and all the neurones which take infomation away from the CNS. It is organised in 2 ways.
25
What are the 2 ways in which the Peripheral nervous system is organised?
-Somatic nervous system
-Autonomic nervous system
26
What is the somatic nervous system?
The system of responses that is under voluntary control
27
What does the somatic system use as its neurotransmitter?
Acetylcholine
28
What is the autonomic nervous system?
The system under the subconscious control and is used when the body does something automatically. It is involuntary. It is broken down into two further systems: sympathetic and parasympathetic
29
What neurotransmitters does the autonomic nervous system use?
Acetylcholine and noradrenaline
30
What is the sympathetic nervous system?
It is involved in the 'fight or flight response' and uses the neurotransmitter noradrenaline
31
What is the parasympathetic nervous system?
Involved in the 'rest or digest' response and uses the neurotransmitter acetylcholine
32
What do dentrites and dendrons do?
Carry impulses to the cell body
33
What do axons do?
Carry nerve impulses away from the cell body
34
What are the ends of axons refered to as?
Axon terminals
35
Describe the structure of a sensory neurone
They have short dentrites that attach to the receptor cells. These then join together to form a dendron and bring the impulse to the cell body, which is about 3/4 of the way to the axon terminals. It then has 1 short axon that brings the impulse away from the cell body, which then connects to the axon terminals
36
Describe the structure of a motor neurone
It has a star like cell body which has lots of dentrites bringing impulses to the cell body. It then has one long axon brining the impulse away from the cell body to the axon terminals, and then effector cells
37
Describe the structure of a relay neurone
Relay neurones have many short dentrites, like a motor neurone that carry nerve impulses to the cell body. It then has one short axon which takes nerve impulses away from the cell body
38
What is an impulse?
The flow of current along a neurone and is bought about by the flow of positive ions not electrons
39
What does the resting potential describe?
The potential difference across the membrane of a neurone when it is not transmitting an impulse.
40
What is the usual resting potential?
70mv
41
How isnresting potential established?
-A carrier protein called the sodium/potassium pump actively pumps 3 Na+ ions out and 2K+ ions into the membrane.
-sodium channels are shut to prevent the flow of Na+ ions
-Some K+ channels are open to allow K+ ions to diffuse down their concentration gradient, making the outside of the membrane more positive (facilitated diffusion)
-This creates an electrochemical gradient as the outside of the membrane is more positive than the inside, making the membrane polarised.
42
What is the generator potential?
The change in potential difference due to a stimulus
43
Describe the generator potential
The stimulus excited the neurone cell membrane, causing sodium ion channels to open. This makes the membrane more permeable to Na+ causing an influx down the electrochemical gradient. This causes depolarisation as the inside of the membrane becomes more positive, until around +30mv
Sodium ion channels then close at 30mv, and potassium ion channels open so the membrane is more permeable to potassium, causing them to diffuse down their concentration gradient to the outside of the neurone, helping with resting potential reistablishment.
Potassium ion channels are slow to close so there is a slight 'overshoot' and the potential difference becomes more negative than resting potential, at roughly 70mv. This is hyperpolarisation. Most potassium channels then close
44
How is the generator potential slightly different in the pacinian corpusle
The pacinian corpusle detects mechanical stimuli such as pressure or vibrations. When occurring, this mechanical stimuli will cause deformity of the layers of connective tissue which are around the dentirte of a neurone, causing deformity of the stretch mediated Na+ channels, causing them to open. The rest of the potential is the same. If light pressure is applied, it is not transmitted, and the pressure only causes the gel to move to either side of the membrane
45
Describe how an action potential occurs
If the generator potential reaches the threshold, then an action potential will be generated.
When the neurone is sufficiently stimulated, voltage gated sodium ion channels will open, allowing Na+ to diffuse into the membrane. If this reaches around -55mv a large amount of voltage gated Na+ channels will open causing Na+ to rush in until around +40mv. The membrane is then said to be depolarised. Sodium channels then close and voltage gated potassium ones open allowing then to diffuse down their concentration gradient causing the inside to become less positive again until around -80mv. This is called hyperpolarisation. Resting potential is then reestablished via the potassium/sodium pump and facilitated diffusion
46
What is the threshold?
The actual potential difference that causes a gate to open
47
What is the refractory period?
It acts as a time delay between 2 action potentials to ensure that they are discrete and are unidirectional. It is the time between an action potential and resting potential, because after an AP a neurone cannot be excited again straight away. This is because ion channels are recovering
48
Explain the waves of depolarisation
When an AP occurs, some of the Na+ ions diffuse sideways causing adjacent voltage gated channels to open. This wave moves away from the parts of the membrane in the refractory period because these parts cannot fire an action potential.
49
What are the types of gates?
Ligand gated sodium ion channels:
Open when pressure is applied
Voltage gates (potassium and sodium): open once a certain potential difference has been reached
Ligand gates: opens when a neurotransmitter binds to it
50
What are some types of receptor?
Mechanoreceptor: detects pressure. E.g pacinian corpusle
Chemoreceptor: detects chemicals. E.g CO2
Thermoreceptoe: detects temperature
Photoreceptor: detects light (cone cells in the retina)
51
What is the all or nothing law?
It states that if a stimulus is below a threshold, then no action potential will occur. If the stimulus is above the threshold, then 1 will occur.
52
What is propagation?
The wave of action potential down an axon
53
Is propogation faster in myleinated or non myleinated neurones?
Myleinated neurones because they 'jump' in a process called saltatory conduction
54
What is saltatory conduction?
A neurones cytoplasm conducts enough electrical charge to depolarise the next node of ranvier, so the impulse jumps from node to node
55
What are the factors affecting the speed of conduction?
1) Myelination: some neurones have a myelin sheath, causing saltatory conduction
2) Axon diametre:
AP are conducted quicker along axons with large diameter because there is less resistance to the flow of ions than in the cytoplasm of a smaller axon. This causes depolariation to reach other parts of the neurone cell membrane quicker
3) Temprature:
As temp increases so does the speed of conduction (Only until around 40 degrees though as after that proteins denature). Respiration also occurs faster to provide ATP for the pumps, reistablishing rp fatser
56
What are all neurones in the peripheral nervous system surrounded by?
Glial cells. These support neurones.
57
What are the glial cells called?
Schwann cells
58
What do schwann cells do?
Most produce myelin. If they do thisthey produce myelinated neurones
59
Hat does the myelin sheath do?
It acts as an electrical insulator. Between adjacent schwann cells, are gaps called nodes of ranvier, from which an action potential jumps from and to.
60
What is the synaptic cleft?
The gap between 2 neurones from which neurotransmitters diffuse
61
What is the synaptic knob?
The swollen end of the pre-synaptic neurone
62
What are some features of a synaptic knob that adapt it for its role?
It has a large surface area, lots of mitachondria, and synpatic vesicles
63
What is a cholinergic synapse?
A cholinergic synapse uses the neurotransmitter acetylcholine which binds to receptors called cholinergic receptors
64
Describe how a nerve impulse is transmitted across a cholinergic synapse
1) The flood on Na+ ions due to the arrival of the AP causes the voltage gated calcium ions channels to open on the pre-synaptic neurone.
2) Calcium ions diffuse into the knob
3) The influx of Ca2+ ions causes synaptic vesicles to move and fuse to the pre-synaptic neurone membrane, in a process called expcytosis.
4) This releases the neurotransmitter
5) The neurotransmitter diffuses across the synaptic cleft and binds with specific receptors (in this case cholinergic receptors)
6) this causes ligand sodium ion channels to open causing depolariation of the post synaptic neurone due to the influx of Na+ ions.
7) If the threshold is reached then an action potential will occur in the post synaptic neurone
8) action potential stops, causing Ca2+ gates to shut due to a less positive charge, allowing resting potential to be reached
9) This stops exocytosis
10)Neurotransmitter is cut in half, so ligand gates sodium ion channels shut
11) the products are taken back into the knob and resynthesised.
12) Resting potential is reestablished
65
What are the products from ACH break down
Choline and ethanoic acid
66
Where does ACHE stay
It stays in the cleft, so is always working. This is why more than one AP is needed in the pre-synaptic cleft to cause 1 AP in the post synaptic cleft, as the ACHE must be overwhelmed
67
What does ACHEI do?
It is ACHE inhibitor, and it inhibits ACHE to allow for an easier action potential in the post synaptic neurone as ACH is not broken down
68
Explain how ligand gated sodium ions work
They must bind with 2 neurotransmitters to open, so they almost act as a threshold because enough must be open to generate and AP in the post synaptic neurone. In this sense, enough ACH must also be released to overhwhelm ACHE, so there is enough left over to bind to the gates
69
When can ACHI be used?
For Alzheimers as this allows for easier AP
70
What can neurotransmitter be?
Excitory or inhibitory
71
What do editors neurotransmitters do?
Depolarise the post synaptic neurone making it fire an action potential if the threshold is reached
72
What do inhibitory neurotransmitters do?
Hyperpolarise the post synaptic neurone preventing it from firing an action potential.
73
What is an excitory synapse?
A synapse where exitory neurotransmitters are released
74
What is an inhibitory synapse?
A synapse where inhibitory neurotransmitters are released
75
What does an inhibitory neurotransmitters do?
It causes chlorine ion channels to open, causing an influx of 'negative charge- causing hyperpolarisation
76
What is synaptic divergence?
Where one neurone connects to many neurones and infomation can be dispersed to many different parts of the body
77
What is synaptic convergence?
When many neurones connect to one neurone and infomation can ba amplified/ made bigger
78
What is summation?
Summation is basically where more than one AP is needed to cause an AP in the post synaptic neurone, mainly due to ACHE.
79
What is temporal summation?
This is when the frequency of AP in the pre synaptic neurone is increased, which will help overwhelm ACHE
80
What is spatial summation?
When AP from different neurones are added together at the synaptic cleft, which will cause enough ACH to be released to overwhelm ACHE
81
Can temporal and spatial summation occur at the same time?
Yes
82
Describe smooth muscle and where it is located.
They are involuntary. They are also called smooth muscle because it doesn't have the striped appearance that skeletal muscle has. Its found in the walls of hollow organs. Each muscle fibre is uniceleate. The muscle fibres are spindle shaped eith pointed ends and about o.2 mm long
83
Describe cardiac muscle and where it is located
It is myogenic. Its found in your heart. Its made of muscle fibres connected by intercalated discs, which have low electrical resistance so nerve impulses pass easily between cells. The muscle fibres are branched. Each cardiac muscle fibre is uninucleate. The muscle fibres are shaped like cylinders and around 0.1mm long. You sometimes see cross striations but they are not as strong as skeletal muscle
84
Describe skeletal muscle and where it is located
It is complex (syncitium) and contain multicellulate cells. They are tubular muscle fibres. The cells are large, and they are striated. They are under voluntary control and do fatigue
85
What is a muscle made up of?
Bundles of muscle fibres
86
What is one bundle of muscle fibres made up of?
Individual muscle fibres
87
Describe the structure of a single muscle fibre
The sarcolemme is it's membrane. It has sarcoplasmic reticulum. It has sarcoplasm, filling spaces in between. It contains many myofibrils and mitachondria to provide energy for the muscle to contract. It has transverse T tubules throughout. This is important to lower the diffusion pathway
88
What is a T-tubule?
An infold in the membrane to form a tube
89
What is a sarcomere?
A co tactile unit that works independently
90
What are the thick myofilaments?
The protein myosin. These make the darker bands
91
What are the thin myofilaments?
The protein actin. These make the lighter bands
92
What is a myofibril made up of?
Many short contractile units called sarcomeres
93
What is the Z line?
The ends of each sarcomere
94
What is the M line?
The middle of each sarcomere. It is the middle of the myosin filaments
95
What is the H zone?
The zone around the M line. It only contains myosin filaments
96
What band contains just actin?
The I band
97
What band contains myosin and actin?
The A band
98
What zone contains myosin only?
The H zone
99
How is muscle contraction explained?
The sliding filament model
100
Explain the structure of actin filaments
They have a binding site for myosin heads called actin-myosin binding sites. It also contains proposing and tropomyosin. Tropomyosin is the long strand
101
Explain the structure of myosin filaments
They have globular heads that are hinged so they can move back and forth. Each myosin head has a binding site for actin and binding site for ATP
102
How does myosin bind with actin at rest.
It doesn't. The binding site is covered by tropomyosin so no contraction occurs
103
Explain the filament theory in steps
1) Calcium ions bind to troponin, changing its shape. Troponin then pulls tropomyosin out of the actin-myosin binding site, exposing the binding site. The myosin then binds with the site forming an actin-myosin cross bridge
2) The calcium ions also activate ATPase, which breaks down the atp attached to myosin. The energy released from this moves the myosin head, and pulls the actin filament along. This is called the powerstroke.
3) ATP then binds to the myosin head again which breaks the cross bridge. The myosin head then binds to a new bidning site further up
5) This happens many times until no more action potential is received
104
Explain how a muscle contracts
1) The sarcolemma will begin polarised due to the constant action of the Na/K pump
2) The action potential arrives at the neuromuscular junction. This causes exocytosis and neurotransmitters to diffuse. Enough must diffuse to overcome the enzyme in the cleft
3) Neurotransmitter binds with Na ligand gated channels causing an influx of sodium, depolarising the sarcoplasm
4) If the threshold is reached, Voltage gated Na channels will open along the whole sarcolemma
5) Change in charge opens voltage gated Ca channels on the endoplasmic reticulum
6) Ca floods into the fibre. Ca then associates with troponin, which then rolls tropomyosin away from the binding sites
7) Sliding filament theory
8) When myosine reaches the Z line, it can go no further
9) When AP stops, enzymes cleave neurotransmitters off ligand gates so they close
10) Repolarisation. Ca pumps pump ca back into sarcoplasmic reticulum. Ca voltage gates close
11) Troponin rolls tropomyosin back over the binding site
12) ATP is still available so myosin heads are still all extended
105
What is the function of fast twitch muscle fibres?
The duration of the twitch is faster by 2-3 times. It is brief and powerful but they are highly fatiguing
106
What is the structure of fast twitch muscle fibres?
-have more glycogen stores
-Less capillaries a day myoglobin
-Larger sarcoplasmic reticulum to increase voltage gated ca ions so ca leaves quicker. This increases speed of contraction
-More t-tubules so signals get to the sarcoplasmic reticulum faster
107
What are slow twitch muscle fibres?
They have a slower contractile speed than fast twitch fibres. They fatigue less as well and use aerobic respiration
108
What is the structure of slow twitch muscle fibres?
-More capillaries
-More myoglobin
-More mitachondria
-Less sarcoplasmic reticulum
109
What is phosphorylation?
In simple terms, ATP Synthesis
110
What are the types of phosphorylation?
1) Photophosphorylation through photosynthesis
2) Oxidative phosphorylation via respiration
3) Substrate level phosphorylation via creatine phosphate
111
What is the cerebrum?
It is the largest part of the brain
112
What does the cerebrum do?
Controls conscious activities such as speech, memory and thought. It is divided into 2 halves called cerebral hemispheres. The left side controls the ride side of the body
113
Describe the structure of the cerebrum
It has a thin outer layer called cerebral cortex. This is where grey matter is located, and is where all the cells bodies are connected. The more grey matter, the more connections. Cerebral cortex is highly folded to increase surface area for these connections. Below the cerebral cortex is white matter, as it houses all the myelinated axons
114
What is the hypothalamus?
It is found just beneath the middle part of the brain, and connected and above the pituitary gland. It monitors blood flowing through it and is involved on homeostasis. It releases hormones directly into the blood stream or via the pituitary gland.
115
What is the pituitary gland?
It is located below the hypothalamus and produces a range of hormones that act on the body directly or indirectly by acting on endocrine glands. It has 2 lobes, the posterior and anterior. The anterior produces and releases hormones whilst the posterior stores hormones produced by the hypothalamus
116
What is the cerebellum?
It is located underneath the cerebrum and is involved in motor control including balance. Functions are involuntary
117
What is the medulla oblongata?
It is located at the Base of the brain where it joins the spinal cord. It has 3 co trol centres
118
What are the medulla oblongatas 3 control centres
Cardiac centre
Vasomotor centre (controls blood pressure)
Respiratory centre
119
What reflex arc does not require a relay neurone?
The knee jerk
120
Why in babies is the NCV value half of that in adults?
Because the myelin sheath takes time to develop
121
What happens to the A band when a muscle contracts?
It stays the same length
122
What does skeletal muscle look like under a microscope?
You will see cross striations, alternating darker and lighter pink. These are the A bands and the I bands. Many purple nuclei will be in each muscle fibre. Muscle fibres will be long
123
What neurotransmitter do neuromuscular junctions use?
Acetylcholine. These bind to receptors called nicotinic cholinergic receptors. AChE breaks down ACh
124
What is pancuronium bromide?
A non depolarising neuromuscular drug that competes with ACh for the nicotinic cholinergic receptors. It can be reversed by inhibiting the action of AChE
Biology OCR
flashcards
Decks in class (25)
# Cards
-
Cell Structure And Microscopy51
-
Biological Molecules97
-
Nucleotides And Nuclaic Acids32
-
Enzymes35
-
Biological Membranes36
-
Cell Division And Organisation41
-
Exchange And Transport55
-
Transport In Animals66
-
Transport In Plants46
-
Disease And The Immune System71
-
Biodiversity59
-
Classification And Evolution77
-
Ecosystems80
-
Populations And Sustainability45
-
Neurology124
-
Homeostasis And Hormonal Control83
-
Plant Responses And Hormones79
-
Excretion133
-
Photosynthesis75
-
Respirstion56
-
Cellular Contril53
-
Patterns Of Inheritance58
-
Evolution ^31
-
Manipulating Genomes97
-
Cloning And Biotechnology57
