Response To Changes In Environment. Flashcards
1
Q
Define stimulus.
A
A change in internal or external environment.
2
Q
Define receptors.
A
Specialised cells or proteins in cell membranes which detect stimuli - they are specific to one type of stimuli.
3
Q
Define effector.
A
Cells which bring about a response to a stimuli.
4
Q
Define sensory neurons.
A
Transmit impulses from receptors to the CNS or relay neuron.
5
Q
Define motor neurons.
A
Transmit impulses from CNS/rely to the effectors.
6
Q
Define relay neurons.
A
Transmits impulses from sensory to motor neurons.
7
Q
Which part of the nervous system controls unconscious activities?
A
Autonomic Nervous System.
8
Q
Define reflex.
A
A rapid, automatic response which does not need to be learnt.
9
Q
Describe the process of the reflex arc.
A
- Receptors detect stimuli.
- Sensory neuron sends an impulse to the spinal cord via the dorsal root.
- Relay neuron connects the sensory neuron to the motor neuron.
- Motor neuron sends impulse to an effector via the ventral root.
- Effector receives impulse and carries out movement.
10
Q
Give 5 importance’s of a reflex arc.
A
- Rapid.
- Protect against damage to body tissues.
- Do not have to be learned.
- Help escape from the predators.
- Enables homeostasis control.
11
Q
Define taxes.
A
Organisms move towards or away from a directional stimulus.
12
Q
What is the difference between a positive and a negative taxis?
A
Positive taxis are when organisms move towards stimulus, whereas negative taxis are when organisms moves away from stimulus.
13
Q
Define kinesis.
A
The organisms’ movements is affected by a non-directional stimulus.
14
Q
How does an organism respond to a kinesis?
A
By increasing speed of movement and more rapid change in direction, both slow down when favourable conditions are met.
15
Q
What is a tropism?
A
A response in a flowering plant to a directional stimulus.
16
Q
What is a positive tropism?
A
Towards the stimulus.
17
Q
What is a negative tropism?
A
Away from the stimulus.
18
Q
What are auxins?
A
Growth factors, which stimulate the growth of shoots by cell elongation.
19
Q
Where are IAA molecules produced?
A
Meristem of shoots and roots.
20
Q
What is the function of IAA molecules?
A
IAA stimulates growth by effecting the elongation of cells in roots and shoots.
21
Q
How does a higher concentration of IAA affect the plant?
A
Higher concentration of IAA can have an inhibitory effect on growth of the roots in plants and a stimulatory effect on shoots.
22
Q
Explain the curvature of the shoot.
A
- Tip produces IAA.
- IAA diffuses into shoot.
- More elongation of cells on one side.
23
Q
Explain how the uneven distribution of IAA causes a root to bend.
A
- IAA at bottom of root where AII concentration high inhibits elongation of cells.
- IAA at the top of the root, where IAA low concentration leads to elongation of cells.
24
Q
What is meant by myogenic?
A
Generates own electrical impulse.
25
Describe the role of the sinoatrial node?
1. Sends out electrical impulses.
2. Initiates the heartbeat.
26
Describe and explain the initiation and co-ordination of a heartbeat?
1. Sinoatrial node (SAN) initiates heartbeat by sending electrical impulse across arial walls.
2. Excitation wave doesn't pass ventricular walls as it is blocked by collagen non-conducting tissue.
3. Atrioventricular node (AVN) delays impulse, then relays impulse to septum between ventricles. This allows atria to completely empty before ventricles contract.
4. Bundle of His fibres running through septum conduct electrical impulse to apex of the heart.
5. Purkyne tissue within Bundle of His carry excitation wave upwards through ventricle muscles from base.
6. Ventricles contract simultaneously from base upwards.
27
Explain importance of delay caused by AVN.
1. Allows atria to completely empty of blood before ventricles contract.
28
Explain how this is co-ordinated in the heart after initiation of heartbeat by SAN.
1. Electrical impulse only through Bundle of His.
2. Wave of electrical activity passes over.
29
What are baroreceptors?
Pressure receptors that detect changes in blood pressure.
30
Where are baroreceptors located?
Aorta and carotid arteries.
31
What are chemoreceptors?
Chemical changes that detect changes in the concentration of oxygen and carbon dioxide and changes of pH in the blood.
32
Where are chemoreceptors located?
Aorta, carotid receptors and medulla.
33
How does heart respond to high blood pressure?
1. Baroreceptors respond to blood pressure.
2. More impulses along the parasympathetic neurons, which secrete acetylcholine that bind to receptors on the SAN.
3.Heart rate slows to reduce blood pressure back to normal.
34
How does the heart respond to low blood pressure?
1. Baroreceptors respond to blood pressure.
2. More impulses along the sympathetic neurons, which secrete noradrenaline that bind to receptors on the SAN.
3.Heart rate speeds up to increase blood pressure back to normal.
35
How does the heart respond to high blood oxygen/low cardon dioxide/high pH?
1. Chemoreceptors detect changes in oxygen, carbon dioxide and pH.
2. More impulses along parasympathetic neurons, which secretes acetylcholine that binds to receptors on the SAN.
3. Heart rate slows to return oxygen, carbon dioxide and pH back to normal.
36
How does the heart respond to low blood oxygen/high cardon dioxide/low pH?
1. Chemoreceptors detect changes in oxygen, carbon dioxide and pH.
2. More impulses along sympathetic neurons, which secretes noradrenaline that binds to receptors on the SAN.
3. Heart rate speeds up to return oxygen, carbon dioxide and pH back to normal.
37
What are dendrites?
Receives and carry impulses towards the cell body.
38
What is an axon?
Long, membrane covered in cytoplasmic extension which generates action potentials and transmits impulses away from cell body.
Has axon endings which form synapses with effector.
39
What are Schwann cells?
Grow around the axon forming a myelin sheath around the cell membrane.
40
What is the myelin sheath?
Electrical insulation of the neuron, speeding up transmission of the impulse.
41
What are the nodes of Ranvier?
The areas between Schwann cells causing gaps in the myelin sheath important in speeding up rate of transmission of the impulse.
42
How is resting potential maintained and established?
1. Na/K pump actively transports 3Na ions out and 2K ions into the axon membrane.
2. Membrane is impermeable to Na ions, so Na cannot diffuse back in.
3. Membrane is slightly permeable to K ions, so some K ions can diffuse back out of axon down electrochemical gradient.
43
What is an action potential?
A sudden change in membrane voltage of a neuron in response to a stimulus.
44
Describe what is known as the threshold potential.
1. A stimulus must cause a change in voltage to reach -55mV.
2. This causes the opening of sodium ion channels in membrane, allowing sodium ions to diffuse into axon down their gradient.
3. This triggers an action potential.
45
What happens when there is a bigger stimulus?
A bigger stimulus increases the frequencies of action potentials, resulting in more action potentials per second.
46
What is the all or nothing principle?
If the threshold potential is not reached, there will be no action potential.
47
Describe the generation of an action potential?
1. A stimulus causes an increase in sodium ions inside the axon and it begins to depolarise. Voltage increases.
2. Depolarisation - if voltage reaches threshold potential, sodium ion channels open, Membrane becomes more permeable to to sodium ions and sodium ions diffuse rapidly into neuron.
3. Repolarisation - Sodium ion channels close and potassium ion channels open. Membrane is more permeable to potassium ions, potassium ions diffuse out of neuron down potassium ion gradient.
4. Hyperpolarisation - Too many potassium ions diffuse out of neurone. Voltage is more positive than resting potential.
5. Resting potential - sodium/potassium pump returns the membrane to -70mV until there is another stimulus.
48
What is a refractory period?
A neuron is resistant to a second action potential during this period.
49
What does it mean that the sodium ion channels cannot open during the refractory period?
1. Action potentials don't overlap.
2. There is a limit to the frequency at which the nerve impulse can be transmitted.
3. Action potentials are uni-directional.
50
What are 3 factors which affect the rate of transmission of an impulse?
1. Myelination.
2. Increase in diameter of an axon.
3. Higher body temperature.
51
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon.
1. Myelination provides electrical insulation.
2. In myelinated, there is saltatory conduction.
3. In non-myelinated, depolarisation occurs along whole length of axon.
52
How does the diameter of an axon affect the transmission of an impulse?
An increase in the diameter of an axon means less resistance to the flow of ions in the cytoplasm.
53
How does body temperature affect the rate of transmission?
At a higher body temperature, rate of diffusion of ions is faster.
However, over 40 degrees, proteins begin to denature , and the speed decreases.
54
Describe the sequence of events during synaptic transmission.
1. Action potential arrives at action terminal, depolarisation causes pre-synaptic membrane to become more permeable to Ca2+ as voltage gated Ca2+ ion channels open and Ca2+ enters by diffusion.
2. Synaptic vesicles fuse with presynaptic membrane.
3. Neurotransmitter released by exocytosis and diffuses across synaptic cleft.
4. Neurotransmitter binds to receptors on post synaptic membrane, causing Na+ channels open.
5. Na+ diffuses in through channels and depolarises the post synaptic membrane. If threshold potential is reached, action potential is generated.
55
What is a Pacinian Corpusle?
A receptor in the skin which responds to changes in pressure.
56
What is a photoreceptor?
Receptors in the eye which responds to changes in light.
57
Define generator potential?
A change in the membrane potential of a receptor cell in response to a stimulus.
58
Describe and explain the creation of a generator potential.
1. The stimulus causes membrane of receptor to become more permeable to sodium ions.
2. Sodium ions diffuse down their gradient into receptor, depolarising it.
3. Change in potential difference due to a stimulus is generator potential.
4. If threshold potential is reached, action potential is triggered, voltage gated sodium ion channels open and sodium ions diffuse in causing depolarisation.
59
Describe how a generator potential is generated through Pacinian corpuscles.
1. When the Pacinian corpuscle is stimulated, the lamella become deformed and press on sensory nerve endings.
2. Stretch mediated sodium ion channels open, sodium diffuses into cell.
3. If threshold potential is reached an action potential is generated.
60
Where is densely packed with photoreceptors?
Fovea
61
Explain how photoreceptors respond to light.
1. Light enters eye and hits photoreceptors.
2. Light-sensitive pigments in the membranes absorb light, causing them to become bleached and breakdown.
3. Sodium ion channels open, sodium ions diffuse in causing a generator potential to be created.
4. If threshold potential is reached, an action potential is generated and transmitted to bipolar neuron then sensory neuron.
5. Impulse is transmitted to optic nerve, which takes impulse to brain.
62
State 3 features of rod cells.
1. Black and white.
2. Low visual acuity.
3. Very sensitive to light.
63
State 3 features of cone cells.
1. Colour vision.
2. High visual acuity.
3. Low sensitivity to light.
64
How many rod cells synapse with the same one bipolar cell?
Many.
65
How many cone cells synapse with the same one bipolar cell?
One.
66
What is meant by the term agonist?
Contracting muscle.
67
What is meant by the term antagonist?
Relaxing muscle.
68
Why does a muscle cell have many mitochondria?
Provide more ATP for contraction.
69
Why does a muscle cell have many nuclei?
Allows proteins to be produced at any point in the cell.
70
State features of an actin filament.
1. Surrounded by tropomyosin.
2. Has many myosin binging sites.
3. Has calcium binding sites.
71
State features of a myosin filament.
1. Consists of many heads, which point in different directions.
72
State what occurs during muscle contraction and what does this cause?
1. Myosin and actin slide over each other.
2. Sarcomere gets shorter as Z lines get closer.
3. H band gets shorter, more overlap means less myosin.
4. I band gets shorter, more overlap, so less actin.
73
Describe the sliding filament theory.
1. Muscle cell surface membrane is depolarised and calcium ion channels open.
2. Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm and then into microfibril.
3. Calcium ions bind to troponin.
4. Tropomyosin moves exposing the myosin binding sites on actin.
5. Myosin heads bind to myosin binding sites forming an actinomyosin bridge using ATP.
6. Myosin heads spontaneously bend releasing ATP, pulling the actin filament towards the centre of the sarcomere.
7. ATP binds breaking the actinomyosin bridge and detaching myosin from the actin filament.
8. Calcium ions activate ATPase, resulting in ATP being hydrolysed and releasing energy and heads move back to original position.
74
What is the purpose of phosphocreatine?
Generates ATP very quickly.
75
What is myoglobin?
A molecule which binds to oxygen in a similar way as haemoglobin.
76
What does myoglobin do?
1. Has a very high affinity for oxygen.
2. Aerobically respires at low partial pressures of oxygen.
77
What are 6 features of slow twitch fibres?
1. Slow, over a long time.
2. For endurance work.
3. Less calcium ions and ATPase.
4. Aerobic respiration.
5. Less glycogen stores.
6. Less phosphocreatine.
78
What are 6 features of fast twitch fibres?
1. Fast, over a short period of time.
2. More calcium ions for ATPase for rapid muscle contraction.
3. For sprint work.
4. Anaerobic respiration.
5. More glycogen stores.
6. More phosphocreatine stores.
79
What is homeostasis?
Involves physiological control systems that maintain the internal environment within restricted limits.
80
What is negative feedback in terms of homeostasis? And how is it detected and restored?
Restores systems back to original levels.
Detected by receptors, communication via nervous system or hormones and restored by effectors to counteract change.
81
What is positive feedback in terms of homeostasis?
Mechanisms which amplify a change from normal levels.
82
What is glycogenesis?
The formation of glycogen from glucose?
83
What is glycogenolysis?
The breakdown of glycogen to glucose.
84
What is gluconeogenesis?
The formation of a new glucose molecule from non-carbohydrates.
85
What is glucose control an example of?
Negative feedback.
86
What is the role of insulin?
Lowers blood glucose concentration by increasing the uptake of glucose into target cells by facilitated diffusion.
87
Describe the process of how insulin decreases blood glucose concentration.
1. Insulin binds to receptors on liver cells on the cell surface membrane.
2. Increases the permeability of glucose by increasing the number of GLUT4 channel proteins., so there is more facilitated diffusion of glucose.
3. It activates enzymes causing glycogenesis.
4. Cells store more glycogen.
5. Increases rate of respiration.
88
What is the role of glucagon?
Raises blood glucose concentration by increasing the production of glucose.
89
Describe the process of how glucagon increase blood glucose concentration.
1. Binds to receptors of liver cells on the cell surface membrane.
2. Activates enzymes stimulating glycogenolysis .3. Activates enzymes stimulating gluconeogenesis.
4. Decreases rate of respiration.
90
What is the role of adrenaline in glucose control?
Increases blood glucose concentration.
91
Describe the process of how adrenaline increases blood glucose concentration.
1. Binds to receptors on cell surface membrane of liver cells.
2. Activates glycogenolysis.
3. Inhibits glycogenesis.
4. Activating glucagon secretion.
5. Inhibiting insulin secretion.
92
What are second messengers?
Chemicals within a cell which stimulate the internal response.
93
Describe the process of the second messenger response.
1. Glucagon/adrenaline bind to receptors on cell surface membrane.
2. This activates adenylate cyclase to covert ATP into cAMP.
3. This activates protein kinase A which stimulates breakdown of glycogen into glucose.
94
What causes type 1 diabetes and how is it treated?
People with type 1 diabetes cannot produce insulin.
It is treated by insulin therapy.
95
What causes type 2 diabetes and how is it treated?
People with type 2 diabetes do not produce enough insulin or their body's cells do not respond to it, may have faulty receptors.
Treated by diet and exercise.
96
What are the two main functions of the kidney?
1. Removal of urea.
2. Osmoregulation, maintaining a a balance between water and dissolved solutes.
97
Describe the process of ultrafiltration.
1. High blood/hydrostatic pressure.
2. Small substance pass through the pores in the capillary endothelium and through the basement membrane.
3. For example, water, glucose, ions, urea and amino acids.
98
What is reabsorbed in selective reabsorption in the proximal convoluted tubule and how are they transported?
1. Glucose and amino acids are reabsorbed by facilitated diffusion, co-transport and active transport.
2. Water is reabsorbed by osmosis.
3. Salt ions are reabsorbed by facilitated diffusion and active transport.
99
How are cells in the proximal convoluted tubule adapted for reabsorption?
1. Large surface area due to microvilli.
2. Lots of mitochondria to synthesise ATP for active transport.
3. Many ribosomes for more protein synthesis to produce transport proteins.
4. Close to blood capillaries to reduce diffusion pathway.
100
Explain why glucose is found in the urine of a person with untreated diabetes.
1. High concentration of glucose in the blood.
2. Not all glucose is reabsorbed at the proximal convoluted tubule.
3. Carrier/co-transport proteins are saturated and working at maximum rate.
101
What are features of the descending and ascending limb in the loop of Henle?
1. Descending limb is permeable.
2. Ascending limb is impermeable.
102
Explain how the loop of Henle provides an osmotic gradient in the medulla for reabsorption of water.
1. Sodium and chloride ions are actively transported out of filtrate in the ascending limb into the tissue fluid, lowering the water potential.
2. Water diffuses out of descending limb by osmosis.
3. Descending limb becomes more concentrated.
4. Salts diffuse down a concentration gradient.
5. Sodium and chloride ions diffuse out of filtrate at the bottom.
6. As the filtrate passes up ascending limb it becomes more dilute due to loss of ions.
