organisms respond to changes in their internal and external environments Flashcards
(151 cards)
1
Q
What are tropisms?
A
the response of a plant to a stimulus coming from a certain direction
2
Q
What are the two types of tropisms?
A
positive- plants growing towards stimulus
negative- plants growing away from stimulus
3
Q
What is phototropism?
A
shoots of plants growing towards light to photosynthesise - positive phototropism
shoots of roots growing away from light - negative phototropism
4
Q
What is gravitropism?
A
shoots of plants growing against gravity - negative phototropism
shoots of roots growing downwards with gravity - positive phototropism
5
Q
What is hydrotropism?
A
shoots of plants growing away from water - negative phototropism
shoots of roots growing towards water - positive phototropism
6
Q
What is thigmotropism?
A
shoots of plants growing towards objects they have touched - positive thigmotropism
explains why plants climb and attach to things
7
Q
What are plant growth factors? (e.g auxins)
A
hormone-like substances produced by cells throughout the plant that affect the growth of tissues in the plant (an example being auxins)
8
Q
What is IAA?
A
an example of an auxin which controls the elongation of plant cells
produced in the tips of shoots and tips of roots
9
Q
What happens to the shoots when light intensity changes?
A
the change in light intensity causes the movement of IAA from the light sides of the shoots to the shaded side
the shoot will then bend towards the light due to a greater concentration of IAA on the shaded side which elongates the one side
this is an example of positive phototropism
10
Q
What happens to the roots when light intensity changes?
A
IAA controls bending of the roots away fromt he light
IAA moves towards shaded side of the roots causing the elongation of cells on the shaded side and the bending of roots away from the light
this is negative phototropism
11
Q
How do shoots and roots move towards /against gravity?
A
IAA moves to the undersides of shoots/ roots causing elongation of ells, bending them and growing upwards/downwards
roots show positive gravitropism
shoots show negative gravitropism
12
Q
What would happen if the tip of a shoot was:
-removed
-covered with opaque material
-removed, put on agar and placed back
-agar put on half of shoot
A
- no bending due to no IAA
- no bending due to no IAA
- plant will bend and grow as normal - IAA will diffuse through agar
-plant would bend only towards that side, as IAA will only be able to diffuse on that side
13
Q
What are the different type of receptors?
A
Photoreceptors (light)
Thermoreceptors (temp)
Chemoreceptors (chemicals)
Mechanoreceptors (pressure)
Proprioceptors (movement)
14
Q
What is the role of sensory receptors?
A
they detect a specific stimulus and convert the change in energy into the nerve impulse/generator potentials
15
Q
What is taxis and kinesis?
A
Taxis means the guided movement to more favourable conditions
Kinesis is the non-directional change in motion in response to the change of conditions
16
Q
What is resting potential?
A
when there is no stimulus detected - ions move in and out of cell through ion channels and pumps
17
Q
What is generator potential?
A
Stimulus is detected
Membrane of receptors become more excited and more permeable
Creates a potential difference across the membrane as more ions can enter the cell
18
Q
What is the action potential?
A
When generator potential passes the ‘threshold level’ passing a detected stimulus onto the sensory neurone
19
Q
What are pacinian corupscules ?
A
mechanoreceptors that detect changes in pressure
20
Q
What is the structure of pacinian corupscules ?
A
sensory nerve ending surrounded by layers of connective tissue called lamellae
21
Q
How to pacinian corupscules respond to change in pressure?
A
-when stimulus is detetcted, lamelle become deformed and presson the sensory nerve ending which deforms the stretch-mediated sodium ion channels
-channels open and sodium ions diffuse in
-influx of ions changes potential difference across membrane creating a generator potential
-if potetnial reaches threshold level, it will trigger action potetnial which is passed onto CNS
22
Q
What are photoreceptors and where are they located?
A
receptors in the eye that detect changes in light
located in the fovea (in the retina)
23
Q
How do photoreceptors in the eye respond the change in light?
A
-light enters eye through pupil and is focused onto retina
-amount of light entering eye is controlled by muscles of iris
-Photoreceptors carry electrical impulses to the brain via the optic nerve (in the place called the blind spot)
24
Q
What are 2 types of photoreceptors?
A
rod and cone cells
25
What are the features of cone and rod cells?
rods- monochromatic vision, multiple rod cells connect to a singular sensory neurone, low visual ascuity, high sensitivty to light
cones - trichromatic vision (blue/green/red), each cone cell has its own sensory neurone, high visual ascuity, low sensitivty to light
26
What is spacial summation?
when a stimulus is detected from different areas
27
What is visual ascuity?
The ability to distinguish between 2 points close together
28
What are neurones?
Nerve cells that are responsibel for the conduction of electircal impulses (action potentials) in the body
29
What is the role of sensory neurones?
transmit nerve impulses from receptor to relay neurone which travels directly to motor neurone
30
What is a neurone cell body?
contains the cell organelles such as nucelus and large amounts of the Rough ER
31
What are dendrons ?
extensions of the cell body that divide into smaller branches called dendrites.
32
What is an axon?
a single long fibre that carries electrical impulses away from the cell body
33
What are dendrites?
dendrites can conduct electrical impulses towards cell body
34
What is a myelin sheath?
made up of Schwann cells that are rich in lipds called myelin - protects the axon and provides electrical insulation
35
What are nodes of Ranvier?
exposed parts of the axon between Schwann cells and where there is no myelin sheath
36
What takes place when a neurone is in resting potential?
Sodium potassium pump pumps 3 sodium ions in and 2 potassium ions out of cell.
The potential difference is at -70mV.
The outside of the cell membrane is more positive than the inside.
37
What happens during depolarisation?
Stimulus is detected, so voltage gated sodium ion channels open allowing sodium ions to diffuse back in, depolarising the membrane.
The inside of the membrane is now more positive so an action potential is generated, reaching at around 40mV.
38
What happens during repolarisation?
Voltage gated sodium ion channels close and potassium ion channels open.
Cell is less permeable to sodium ions but more to potassium ions.
This causes repolarisation as outside is more positive than inside.
39
What happens during the refractory period /hyperpolarisation?
Voltage gated potassium ion channels are slow to close so there is an overshoot in number of potassium ions that diffuse out of cell.
Outside becomes more positive than inside
Sodium potassium pump re-establishes resting potential as it pumps 3 sodium ions out and 2 potassium ions into the cell
40
What is a synapse?
junction between 2 or more neurones or between neurones and effector cells
41
What is the gap between two neurones called?
Synaptic cleft
42
What are the 2 types of neurones (before and after a synaptic cleft?)
presynaptic neurone
postsynaptic neurone
43
What is the end of a synaptic neurone called?
synaptic knob- the swollen portion of a neurone
44
How can you differentiate from presynaptic and postsynaptic neurones?
presynaptic have vesicles that contain neurotransmitters
postsynaptic have receptor sites complementary to specific neurotransmitters
45
What is the junction between 2 neurones called?
cholinergic synapse
46
What is the junction between a presynaptic neurone and a muscle called?
neuromuscular junction
47
What happens when an action potential reaches the end of the presynaptic neurone?
-voltage gated calcium ion channels open
-calcium ions diffuse across the cell surface membrane into presynaptic knob by facilitated diffusion
-influx of Ca2+ causes vesicles which contain neurotransmitters to fuse with membrane of the presynaptic knob
-neurotransmitters fuse with membrane of presynaptic knob
-neurotransmitters are released into synaptic cleft by exocytosis and bind onto complementary receptors on postsynaptic neurone
-sodium ion channels open and sodium ions diffuse down concentration gradient into postsynaptic neurone
-depolarisation of membrane
-influx of sodium ions into postsynaptic neurone causes a new action potential
-enzyme acetylcholinesterase hydrolyses ACh into acetyl and choline to stop continuous action potentials
-they will then diffuse back into knob of presynaptic neurone
-ATP produced by mitochondria is used to combine acetyl and choline to reform ACh, stored in vesicles for future use
48
What is ACh an example of and why?
An excitatory neurotransmitter - as it depolarises the postsynaptic membrane causing action potentials to be generated
49
What is AChE?
Acetylcholinesterase - an enzyme that hydrolyses ACh into acetyl and choline
50
What is an inhibitory neurotransmitter?
one that prevents an electrical impulse from being passed along further
51
Describe the different parts of skeletal muscle
-bone
-tendon
-muscle fibres
-sarcolemma
-transvers tubules
-sarcoplasmic reticulum
-myofibhril
-myofilaments
52
What are the different parts of a sarcomere?
H zone- only myosin filaments (middle)
A band- myosin and actin
I band- only actin
M line- middle line
Z line- mark the ends of the sarcomere
53
What are the 3 types of muscles?
Smooth, cardiac and skeletal
54
What are involuntary muscles?
ones that contract without our concious control
55
Describe smooth muscles
involuntary muscles
found in walls of internal organs like stomach and intestine
56
Describe cardiac muscles
found only in the heart
myogenic muscles
57
What are myogenic muscles?
ones that contract and relax on their own without recieving electrical impulses
58
Describe skeletal muscles
voluntary muscles
antagonsitic muscles
made up of muscle fibres
59
What are antagonistic muscles?
when one contracts the other relaxes
60
What is the muscle that is contracting called?
agonist
61
What is the muscle that is relaxing called?
antagonist
62
What is the sarcolemma?
the cell membrane of the muscle fibre cells - it fold inwards across muscle fibres forming transverse tubules
63
What is the role of transvers tubules?
help spread electrical impulses throughout whole of sarcoplasm
64
Where are calcium ions stored and released in skeletal muscles?
sarcoplasmic reticulum
65
What is ATP used for in skeletal muscles?
its provided by muscle fibres to provide energy for contractions
66
Describe the structure of myofibrils
contain thick (myosin) and thin (actin) myofilaments
each myofibril is made up of sarcomeres
67
What is the sliding filament theory?
when actin and myosin filaments slide over each other causing sarcomere to contract
When lots of sarcomeres contract it leads to muscle contractions
68
What happens when sarcomeres contract?
A band stays the same
I band shortens
H zone shortens
Z lines get closer
69
What is the structure of a myosin head/filament ?
It has a hinged globular head allowing it to move back and forth
each myosin head has a binding site for actin and ATP
70
Describe the structure of actin filaments
contain binding sites for actin-myosin binding site
contain tropomyosin
71
What is the role of tropomyosin?
helps filaments move past each other by blocking actin-myosin binding site when muscles are resting - leading to the inability of the filaments to slide over each other
72
What happens when an action potential is generated in skeletal muscles?
-depolarisation of sarcolemma
-release of Ca2+ ions triggering muscle reaction
-Ca2+ binds to tropomyosin, exposing the binding site
-Myosin head binds to binding site - called the actin-myosin cross bridge
- Ca2+ ions activate enzyme ATP hydrolase which hydrolyses ATP into ADP + Pi to provide energy
- this allows myosin head to move (power stroke) pulling actin filament with it
-ATP provides energy to break cross bridge so that myosin can dettach and attach to different position
73
What is the PCr system?
it involves ATP and phosphocreatine
it provides an immediate production of ATP by phosphorylating ADP by adding phosphate from PCr stored in cells
74
What are the properties of PCr?
used for short bursts of vigourous exercise
anaerobic - doesnt form lactate
75
What are slow twitch muscles and their properties?
contract slowly and work for a long time before getting tired
-energy released through aerobic respiration
-lots of blood vessels to provide O2
-mitochondria near edge of muscle fibres for short diffusion pathway
-rich in myoglobin to store O2
76
What are fast twitch muscles and their properties?
they contract very quickly but also get tired very quickly
-useful for short bursts of vigorous exercise
-found in high proportions in legs, arms and eyes
-energy released through anaerobic respiration using glycogen
-very few mitochondria and blood vessels
- whiter colour due to lack of myoglobin
77
What is homeostasis?
The maintenance of a stable internal environment within restricted limits, regardless of changes in the external environment.
78
Which internal conditions are commonly regulated by homeostasis?
* Body temperature
* Blood glucose levels
* Blood water potential
79
What is feedback in the context of homeostasis?
Feedback refers to the mechanisms that regulate the response to changes, ensuring stability in the internal environment.
80
What is meant by the term 'optimal point' in homeostasis?
the point at which the syste operates best
81
What are receptors?
Detect changes from the optimal point
82
What is the role of a coordinator in a system?
Coordinates changes and sends electrical impulses to effectors
83
What are effectors?
Bring change and return to the optimal point
84
What is negative feedback?
Changes detected are counteracted by the nervous system to re-establish the optimal point
85
Give an example of negative feedback.
Temperature regulation through sweating or shivering
86
What is positive feedback?
Amplifies change that has been detected
87
Give an example of positive feedback.
Blood clots forming due to platelets being activated
88
What is another example of positive feedback?
Women's menstrual cycle affecting the thickness of the womb
89
What is the internal temperature that humans need to maintain?
37°C
90
What happens to enzymes at temperatures below 37°C?
Substrates and enzymes have less energy, reducing activity -slower metabolic processes.
91
What occurs at temperatures above 37°C?
(enzymes)
Enzymes denature due to increased molecular vibration - breaking hydrogen bonds holding the 3D structure
92
What does pH represent?
The concentration of hydrogen ions in a solution
pH is a measure of acidity or alkalinity.
93
What happens when pH levels are too low or high?
Denaturation of proteins occurs, changing their 3D shape
94
What does an increase in hydrogen ions (H⁺) indicate about the pH level?
The pH level is lower and the solution is more acidic
95
How is the pH of a solution calculated?
Using the formula pH = -log10[H⁺]
96
What does each log value in the pH scale represent?
It indicates a x10 change from the previous value
97
What is the relationship between pH and acidity?
The lower the pH, the higher the acidity
98
What is the primary role of glucose in the body?
Needed for energy for respiration
99
How does blood glucose concentration affect water potential?
Affects the water potential of blood
100
What happens if blood glucose concentration is too low?
Cells are unable to carry out normal functions due to insufficient energy for respiration
101
What occurs if blood glucose concentration is too high?
Water will move out of cells by osmosis, causing them to shrivel and die
102
Define hormones
Chemical messengers produced in organs called glands
103
How are hormones released into the body?
Released directly into the bloodstream
104
What is the target for hormones?
Target cells that have complementary receptor/binding sites on the cell surface membrane
105
What are the characteristics of hormone effects?
Effective in low concentrations, but have long lasting and widespread effects
106
What is controlled by hormones?
Blood glucose concentration
107
Where is insulin produced?
In the pancreas
108
What are the groups called that produce hormones in the pancreas?
Islets of Langerhans
109
Which cells manufacture and secrete glucagon?
Alpha Cells
110
Which cells manufacture and secrete insulin?
Beta Cells
111
What happens when hormones are released?
They are carried to cells, including liver (hepatocytes) and muscle cells
112
What is glycogenesis?
Conversion of glucose into glycogen
113
What is glycogenolysis?
Breakdown of glycogen into glucose
114
What is gluconeogenesis?
Making glucose from other sources
115
What happens when we eat food containing carbohydrates?
Our blood glucose concentration increases
116
What do beta cells in the Islets of Langerhans secrete when blood glucose levels rise?
Insulin
117
What effect does insulin binding have on cell membranes?
Increases permeability to glucose
This is achieved by changing the tertiary structure of glucose transport carrier proteins.
118
What process allows glucose to enter cells?
Facilitated diffusion
119
What happens as a result of increased insulin concentration?
Causes carrier proteins to fuse with the cell surface membrane
This increases the number of transport proteins available for glucose uptake
120
What does insulin activate in liver cells?
enzymes that carry out glycogenesis and convert fat
121
What happens when enzymes in liver cells are activated?
lowering of blood gluocse concentration
increased rate of absoption
increased rate if respiration
increased rate of conversion of glucose to fat
122
What is glucagon?
a hormone that that binds to a specific receptor on cell surface membrane of liver cells
results in glycogenolysis and glycogenesis
123
What is adrenaline?
a hormone produced in the adrenal glands (top part of kidneys)
increases blood glucose concentration in times of excitment or stress - stimulatin glycogenolysis
124
What is the secondary messenger model?
a mechanism used by adrenaline and glucagon in regulation of blood glucose concentration - hormones are the first messenger
125
Describe the process of the secondary messenger model
-adrenaline binds to transmembrane protein within cell surface membrane on liver cell
-protein changes shape and activates enzyme adenylate
-activated adenylate converts ATP into cyclic AMP (cAMP) which binds to enzyme, changes its shape and causes glyogenlysis
-glucose moves out of liver cells into bloodstream through facilitated diffusion by carrier proteins
126
What does cAMP do?
acts as a secondary messenger that binds to enzyme kinase changing its shape and activating it which causes glycogenlysis
127
What are antagonistic hormones?
hormones that work in opposite directions
insulin decreases blood glucose concentration whereas glucagon increases it
128
What is the optimum blood glucose concentration?
5 mmol/dm3
129
What is osmoregulation?
control of water potential in the blood
130
What organ is responsible for osmoregulation?
the kidneys
131
What are osmoreceptors?
receptors that detect change in osmotic pressure in blood as it flows through
when osmotic pressure of blood changes, water moves in or out of osmoreceptors, causing cell to expand or contract
132
Where are osmoreceptors found?
in the hypothalamus
133
Describe the process of dehydration
-when water potential of body is very low
-water moves out of cells and causes osmoreceptors to shrink
-sends signals to other cells in hypothalamus to bring a response
-response ensures that more water is reabsorbed from blood tubules in nephron
(kidney cells)
-results in person producing small amounts of concentrated urine
-reduces water loss through excretion
134
What is excretion?
the removal of metabloic waste products from the body
135
What does metabolic waste consist of ?
toxic compounds e.g. nitrogen
136
What are the different parts of the kidney?
outer region - cortex
inner region - medulla
central region - pelvis - leads to uretrus and bladder
137
What are the different components of a nephron?
afferent arteriole
glomerulus
bowman's capsule
efferent arteriole
proximal convoluted tuubule
distal convoluted tubule
loop of Henle
collecting duct
138
What do antidiuretic hormones control?
volume of water reabsorbed
139
Where does regulation of water potential take place in a nephron?
loop of henle
distal convoluted tubule
collecting duct
140
What happens when osmosreceptors detect a low water potential in blood?
hypothalamus produces ADH
ADH binds to complementary receptors in plasma membrane of cells lining distal convoluted tubule and collecting duct
aqauporins inserted into plasma membrane causing water to move through membrane by osmosis into medulla.
141
What are aquaporins and what do they do?
protein channels that amke the walls of the distal convoluted tubule more permeable to water
142
What happens during overhydration?
-water moves into osmoreceptor cells causing them to expand
-pituitary gland releases less ADH into blood
-distal convoluted tubule and collecting duct become less permeable to water
- less water is absorbed into bloof and a large amount of dilute urine is produced
-increased amount of water loss in excretion
143
Info on camels relating to bood water concentration:
-they have a very long loop of henle meaning more water can be reabsorbed from glomerular filtrate back to blood
-they produce small amounts of very concentrated urine
144
What is ultrafiltration?
145
Describe the process of ultrafiltration
-blood enters kidney from renal artery
- blood enters glomerulus through the afferent arteriole that came from the renal artery, then carried away from glomerulus towards the efferent arteriole
-liquid and small molcules in blood forced out of capillary and into Bowman's capsule
-large molecules remain in the blood
-passes along the rest of the nephron while filtered blood leaves glomerulus via efferent arteriole
146
What is the glomerular filtrate?
substances that enter the Bowman's capsule
147
What is selective reabsorption?
as glomerular filtrate passes along nephron, useful substances are reabsorbed back into blood
epithilium walls of proximal convoluted tubule have microvilli which proved large surface area for this
glucose is reabsorbed by active transport and facilitated diffusion
water will re-enter blood via osmosis
148
What is urine usually made up of?
excess water, dissolved salts and hormones
149
Where is the Loop of Henle located and what is it in charge of?
located in medulla of kidneys
made of ascending and descending limb
controls sodium ions so water can be reabsorbed into blood
150
Describe the process of sodium ions and water absorption in a nephron
-sodium ions are pumped into medulla by active transport in the ascending limb and water stays inside it (creating low water potential)
-in descending limb, water moves out by osmosis from descending limb to medulla
(higher water potential)
-glomerular filtrate is concentrated due to the descending limb being impermeable to ions
- water is reabsorbed into blood from medulla to capillaries
-near bottom of ascending limb, Na+ ions diffuse into medulla, lowering the water potential
-water moves out of distal convoluted tubule by osmosis and reabsorbed by blood
-medulla increases in ion concentration and lowers in water potential
-water moves out of collecting duct by osmosis and it reabsorbed by blood
-ADH results in more water being absorbed from medulla back into blood resulting in small volumes of very concentrated urine.
151
What are the properties of the ascending and descending limb?
Ascending:
-impermeable to water
-permeable to ions
Descending:
-permeable to water
-impermebale to ions
