Organisms Respond To Changes In Their Internal And External Environments (3.6) Flashcards
1
Q
how can receptor cells respond to stimuli?
A
- some produce electrical activity in nerve cells
- some secrete substances
2
Q
what are 2 examples of a coordinator?
A
brain
spinal chord
3
Q
what are the 3 stages in the reflex arc?
A
detection
coordination
action
4
Q
describe the reflex action process
A
stimulus -> receptor -> coordinators -> effectors -> response
5
Q
how do organisms respond to change?
A
they detect a stimulus (by a receptor cell)
6
Q
an organism must find ________ conditions to survive
A
favourable
7
Q
what is taxis and kinesis?
A
simple responses that enable mobile organisms to stay in a favourable environment
8
Q
what is kinesis?
A
a non-directional response to a stimuli
e.g when flatworms under a stone are exposed to light they move in random directions which eventually bring them back into the darkness, they will then stop moving
9
Q
the rate of movement of an organism is affected by the ________ of the stimulus
A
intensity
10
Q
what is taxis?
A
a directional response to a stimulus (the organism moves directly away or towards the stimulus)
e.g euglena swims directly towards the light in a pond using its flagellum
11
Q
what is phototropism?
A
a growth response to light
12
Q
what is a tropism?
A
a growth response towards a stimulus (in plants)
13
Q
what is geotropism?
A
growth response to gravity
14
Q
a tropism can be __________ or __________ causing the plant to grow towards or away from the stimulus
A
positive
negative
15
Q
plant growth regulators act in a similar way to _________________ in animals
A
hormones
16
Q
the growth response in plants relies on plant growth ____________ that are released in response to a _________.
A
regulators
stimulus
17
Q
what are 2 examples of plant growth regulators?
A
auxin
IAA’s
18
Q
what does IAA stand for?
A
indoleactic acid
19
Q
where is IAA found in the plant
A
just before the tip
20
Q
how does IAA influence the growth of a plant towards a stimulus?
A
- when IAA moves into the elongating region of the shoot it lowers the PH
- this breaks some of the bonds in the cellulose cell wall
- the cell wall loosens and the cells can be more easily stretched (cell elongation)
-by effecting the cell elongation, IAA influences the growth of a plant towards the stimulus
21
Q
what is it called when shoots grow towards the light?
A
positive phototropism
22
Q
describe the process of phototropism?
A
-in shoots, higher concentrations of IAA results in a greater rate of cell elongation
-IAA moves from the illuminated side of a shoot to the shaded side
- the higher concentration of IAA on the shaded side causes a faster rate of cell elongation
- this causes the shoot to bend towards the light
23
Q
What are some elements of hormonal communication?
A
Chemical
Transmition by blood
Slow
Long lasting response
Permanent effect
24
Q
What are some elements of nervous transmission?
A
Neurone transmission
Rapid transmission
Localised
Temporary effect
Nerve impulse specifically targeted
25
What are the 2 elements of the peripheral nervous system?
Autonomic - unconscious
Voluntary - conscious control
26
What type of cell is the Pacinian Corpuscle?
Receptor cell
27
The Pacinian Corpuscle responds to changes in _____________ __________.
Mechanical pressure
28
How is a nerve impulse generated in the Pacinian Corpuscle?
When pressed, the change in pressure on the membrane passes to the core and causes increased permeability to sodium ions causing depolarisation leading to a generator potential. If this exceeds the threshold then a nerve impulse is generated.
29
The Pacinian Corpuscle is a t___________.
Transducer
30
What is a transducer?
Converts one form of energy to anothr
31
How does the Pacinian Corpuscle act as a transducer?
It converts the energy of the stimulus into a nervous impulse known as a generator potential.
32
What happens to the stretch mediated sodium channel protein when they are deformed?
Their permeability to sodium changes and allow sodium ions to pass along them.
This stretching widens the sodium channels and sodium ions diffuse into the neurone.
The influx of sodium ions changes the potential of the membrane (depolarised), making a generator potential.
The generator potential therefore starts an action potential-nerve impulse
33
What is the lining of the eyeball called?
The retina
34
What do light receptors do?
Send nerve impulses along sensory neurones in the optic nerve to the brain
35
What are the 2 types of photoreceptors?
Rods and cones
36
Light use pass through other structures e.g ________ ____ to reach the rods and cones.
Bipolar cells
37
What photosensitive chemical do rods contain?
Rhodopsin
38
What photosensitive pigment do cones contain?
Iodopsin
39
What happens to photosensitive chemicals in light?
The pigments are bleached by the light.
After bleaching rhodopsin regenerates slowly and iodopsin regenerates quickly
40
How many rods are there in the eye?
120 million
41
How many rods connect to one bipolar cell?
15 to 45
42
Where are rods found?
In all the retina but not in the fovea
43
Rods have ______ sensitivity
Good
44
How many cones are there in the eye?
6 million
45
How many cones connect to 1 bipolar cell?
1
46
Where are cones found?
In all the retina, there are lots in the fovea
47
Cones have _____ sensitivity
Poor
48
What are the 3 types of cones?
Red
Green
Blue
Each type of cone has a broad sensitivity to different wavelengths so the responses overlap to distinguish other colours e.g yellow
49
Iodopsin regenerates ______.
Quickly
50
Rhodopsin regenerates ______.
Slowly
51
What are the two divisions of the autonomic nervous system?
Sympathetic nervous system
Parasympathetic nervous system
52
The sympathetic nervous system _______ up activities and thus allows us to cope with stressful situations e.g the fight or flight response
Speeds
53
The parasympathetic nervous system inhibits effects and ______ _____ activities. This allows energy to be conserved. Controls under normal resting conditions.
Slows down
54
The sympathetic and parasympathetic nervous system are ____________, meaning their effects oppose one another.
Antagonistic
55
Where are chemoreceptors found?
In the wall of the coronary arteries
56
What do chemoreceptors detect change in?
PH
57
When CO2 concentrations in the blood is too _______, chemoreceptors detect the drop in __ and send impulses to the section of the medulla oblong at a responsible for increased heart rate.
High
PH
58
Where do chemoreceptors send impulses to in the brain?
The medulla oblongata
59
What is the medulla oblongata?
The cardiac centre of the brain
60
The medulla oblongata is linked to the ___ node that decreases ______ rate via the parasympathetic nervous system.
SA
Heart
61
How does the medulla oblongata increase heart rate?
Increases the number of impulses sent to the SA node via the sympathetic nervous system.
62
What is a baroreceptor?
A pressure receptor
63
Where are baroreceptors found?
In the wall of the coronary artery and the atria
64
What happens when blood pressure is too high?
Impulses are sent to the medulla oblongata which sends impulses to the S.A node via the parasympathetic nervous system which decreases the heart rate.
65
What happens when blood pressure is too low?
Impulses are sent to the medulla oblongata which then sends impulses to the S.A node via the sympathetic nervous system which increases the heart rate
66
What is an ECG?
Electrocardiogram
67
What does the parasympathetic nervous system do?
Inhibits effectors
Controls actions under resisting conditions
Slows down activity
Conserves energy
68
What does the sympathetic nervous system do?
- stimulates effectors
- controls conditions under stress or activity
- initiates the fight or flight response
69
What is a nerve impulse?
A self propagating wave of electrical disturbance that travels along the surface of the axon membrane.
70
What is the resting potential of an axon?
-65mv
71
When is an axon said to be polarised?
When it is at its resting potential
72
The active transport of sodium ions is greater than that of potassium ions. How many sodium ions move out for the potassium ions that move in?
3 sodium ions move out for every 2 potassium ions that move in.
73
How is a chemical gradient created in the axon?
There are more sodium ions in the tissue fluid surrounding the axon than in the cytoplasm, and more potassium ions in the cytoplasm than in the tissue fluid, this creating a chemical gradient.
74
Why is there an electrical gradient in the axon?
As more potassium ions diffuse out of the axon, the outside of the axon becomes more and more positive.
75
What is an action potential?
The temporary reversal of the charge on the axon membrane. As a result the negative charge of -65mv inside the membrane becomes a positive charge of around +40mv
76
What happens to the axon membrane during an action potential?
It is depolarised
77
Briefly describe an action potential.
1. Na gated channels open
2. Na food into axon
3. Potential difference reversed
4. Na gates close
5. K gated channels open
6. K flood out of axon
7. Inside axon returns to negative
8. Resting potential is restored
78
What is hyperpolarisation?
The temporary overshoot of outward diffusion of potassium ions leads to the inside of the axon being more negative (relative to the outside) than usual.
79
What are the 3 factors that affect the speed of an action potential?
- myelination and saltatory conduction
- axon diameter
- temperature
80
How does myelination effect the speed of an action potential?
The action potential jumps from node to node (saltatory conduction) which means the action potential travels along the axon faster as it doesn’t have to generate an action potential along the entire length, just the nodes of Ranvier
81
How does axon diameter effect the speed of an action potential?
The wider the diameter, the speed of conductance increases
A wider diameter means that there is less leachate of ions out and therefore action potentials travel faster
82
How does temperature affect the speed of an action potential?
A higher temperature increases the speeds of conductance because:
- the ions diffuse faster
- the enzymes involved in respiration work faster therefore there is more ATP for active transport in the sodium potassium pump
83
Describe how a synapse functions.
1) an action potential arrives at the synaptic knob. Depolarisation of the synaptic knob leads to opening of Ca+ channels and Ca+ diffuses into the synaptic knob.
2) vesicles contain neurotransmitters move and fuse with the presynaptic membrane. Neurotransmitter is released into the synaptic cleft.
3) Neurotransmitter diffuses, down concentration gradient, across synaptic cleft, to post-synaptic membrane; neurotransmitter binds by complementary shape to receptors on the surface of the post-synaptic membrane.
4) Na+ ion channels on the post-synaptic membrane open and Na+ diffuses in; if enough neurotransmitter, then enough Na+ diffuses in, above threshold, and post-synaptic neurone becomes depolarised.
5) neurotransmitter is degraded and released from the receptor; the Na+ channel close and the post-synaptic neurone can re-establish resting potential; the neurotransmitter is transported back into the presynaptic neurone where is it recycled.
84
1) an action potential arrives at the synaptic _____. Depolarisation of the synaptic knob leads to opening of Ca+ channels and Ca+ diffuses into the synaptic knob.
2) vesicles contain neurotransmitters move and fuse with the presynaptic membrane. Neurotransmitter is released into the synaptic _____.
3) Neurotransmitter diffuses, down ____________ gradient, across synaptic cleft, to post-synaptic membrane; neurotransmitter binds by complementary shape to receptors on the surface of the post-synaptic membrane.
4) Na+ ion channels on the post-synaptic membrane open and Na+ diffuses in; if enough neurotransmitter, then enough Na+ diffuses in, above ________, and post-synaptic neurone becomes depolarised.
5) neurotransmitter is degraded and released from the receptor; the Na+ channel close and the post-synaptic neurone can re-establish _______ potential; the neurotransmitter is transported back into the presynaptic neurone where is it recycled.
1) knob
2) cleft
3) concentration
4) threshold
5) resting
85
What is unidirectionality?
- synapses can only travel in one direction from the presynaptic neurone to the postsynaptic neurone
86
What are the 2 types of summation?
Spatial summation
Temporal summation
87
What is spatial summation?
- a number of different presynaptic neurones together release enough neurotransmitter to exceeded the threshold value of the post synaptic neurone. Together they therefore trigger a new action potential
88
What is temporal summation?
- a single presynaptic neurone releases neurotransmitters many times over a short period. If the total amount exceeds the threshold value of the postsynaptic neurone, then a new action potential is triggers.
89
What is inhibition in a synapse?
- on the postsynaptic membrane of some synapses, the protein chapels carrying chlorine ions (Cl-) can be made to open.
- this leads to an inward diffusion of Cl- ions, making the inside of the postsynaptic membrane even more negative than when it is at resting potential (hyperpolarisation)
- this makes it less likely that a new action potential will be created (inhibitory synapses)
90
What are the different modes of action drugs can have on a synapse?
- stimulating the release of a neurotransmitter
- providing the chemicals needed to synthesise neurotransmitters
- acting in the same way as a neurotransmitter by binding to the same specific receptor
- preventing the reuptake of the neurotransmitter by the presynaptic neurone
91
Neurotransmitters are inhibitory or __________.
Excitatory
92
Excitatory neurotransmitters result in the production of an a_____ p________.
Action potential
93
Inhibitory neurotransmitters prevent the production of an a______ p_______. They do this by causing __________ ions to leave the postsynaptic membrane.
Action potential
Potassium
94
Striated muscles make up the muscles in the body that are attached to the ________.
Skeleton
95
What is a striated muscle made up of?
Muscle fibres
96
What is a striated muscle made up of?
Muscle fibres
97
What is the cell surface membrane called in a striated muscle cell?
Sarcolemma
98
What is the cytoplasm called in a striated muscle cell?
Sarcoplasm
99
what is the Endoplasmic reticulum called in a striated muscle cell?
Sarcoplasmic reticulum (SR)
100
What does the sarcoplasm contain?
Mitochondria and Myofibrils
101
What are Myofibrils?
Bundles of actin and myosin filaments - slide past each other during muscle contraction
102
How are calcium ions transported into lumen of the sarcoplasmic reticulum?
The membrane of the SR contain protein pumps that transport calcium ions into the lumen of the SR
103
Where are Myofibrils located?
In the sarcoplasm
104
What are the 2 types of protein filament that a Myofibrils is made up of?
Myosin
Actin
105
Each Myofibril is made up of _____ filaments of myosin and ____ filaments of actin.
Thick filaments of myosin
Thin filaments of actin
106
What are the 6 elements of a myofibril?
H band
I band
A band
M line
Z line
Sarcomere
107
What is the H band?
Part of a Myofibril where only thick myosin filaments are present
108
What is the I band?
Part of a Myofibril where only thin actin filaments are present
109
What is the A band?
Part of a Myofibril that contains areas where only myosin filaments are present and areas where myosin and actin filaments overlap
110
What is the M line?
Part of a Myofibril where there is attachment for myosin filaments
111
What is the Z line?
Part of a Myofibril where there is attachment for actin filaments
112
What is the sarcomere?
The section in a Myofibril between two Z lines
113
What are the 2 types of muscle fibres?
Slow-twitch
Fast-twitch
114
What are some elements of fast muscle fibres?
- short contraction-relaxation cycle
- fewer capillaries
- ATP supplied mostly from anaerobic respiration
- fewer, smaller, mitochondria present
- large store of calcium ions in the SR
- large amounts of glycogen and phosphocreatine present
- faster rate of ATP hydrolysis in myosin heads
- fatigues rapidly due to grater lactate formation
115
What are some elements of slow muscle fibres?
- long contraction -relaxation cycle
- denser network of capillaries
- ATP supplies mostly from aerobic respiration
- many, lager, mitochondria present
- small store of calcium ions in the SR
- small amounts of glycogen present
- slower rate of ATP hydrolysis in myosin heads
- fatigues more slowly due to rescued lactate formation
116
What proportions of fast muscle fibres do high intensity athletes have?
Higher proportions
- low proportion of slow muscle fibres
117
What proportions of slow muscle fibres do endurance athletes have?
High
- low proportion of fast muscle fibres
118
What effects can training have on an individual’s muscles?
- influence which fibre types develop
- increase the number of capillaries and mitochondria present in muscles
119
What 3 molecules make up an actin fibre?
Actin, tropomyosin, troponin
120
What is the named neurotransmitter?
Acetylcholine
121
Which enzyme breaks down acetylcholine?
Acetylcholinesterase
122
Muscles are ________.
Antagonistic
123
Skeletal muscle is under conscious (V________) control.
Voluntary
124
Describe the structure of a myosin filament.
Composed of polypeptide chains twisted around each other with two globular heads on the end.
125
Describe how a wave of depolarisation spreads across the sarcolemma in a neuromuscular junction.
An action potential causes the release of acetylcholine into sarcolemma
126
What causes the release of calcium ions from the SR in a neuromuscular junction?
The wave of depolarisation spreads over the sarcolemma into T tubules- this causes the release of calcium ions from the SR
127
What to calcium ions attach to on the actin filament snd what does this do? (Neuromuscular junction)
The calcium ions attach to the troponin complexes and cause them to detach from tropomyosin. This exposes myosin binding sites
128
What provides the energy for a contraction (Neuromuscular junction)?
As the myosin attaches to the acid a molecule of ATP is broken down into ADP and Pi. This release of energy provides the energy for the contraction
129
Describe a power stroke.
Myosin, locked onto actin, now contracts - pulling the actin filaments. The 2 filaments slide past each other - this s why it’s called the sliding filament model of muscle contraction
130
What is the role of homeostasis?
Ensure the internal conditions of an organism are kept relatively constant
131
What are some processes that homeostasis in mammals control?
Core body temperature
Metabolic waste
Blood PH
Concentration of blood glucose
Concentration of respiratory gasses (carbon dioxide and oxygen) in blood
132
What are the homeostatic mechanism in mammals?
Nervous system
Endocrine system
133
What does homeostasis control to ensure constant enzyme activity?
Temperature
PH
134
Why does homeostasis control blood glucose concentration?
The amount of glucose in the blood can affect the water potential of the blood
135
What are the elements of a negative feedback control loop?
Receptor -> coordination system (nervous/endocrine system) -> effector
136
What are the elements of a negative feedback control loop?
Receptor -> coordination system (nervous/endocrine system) -> effector
137
What is the purpose of negative feedback?
If there is an increase in a factor the body respond to make the factor increase.
If the factor decreases the body responds to make the factor decrease.
The system is restored to its original level
138
What is positive feedback?
The original stimulus produces a response that causes the factor to deviate even more from the normal range which enhances the effect of the stimulus
139
What is an endotherm?
An organism who generates their own heat to maintain a constant body temperature
140
What is an ectotherm?
Organisms who relies on external sources of heat to regulate their body temperature
141
What is the role of the hypothalamus in thermoregulation?
Receives information about the body’s internal and external temperature and coordinates the appropriate response to maintain a constant temperature
142
What is vasoconstriction?
Narrowing of blood vessels
143
What is vasodilation?
Widening of blood vessels
144
What are some examples of physiological responses to heat?
Sweating, vasodilation and increased breathing rate
145
What are some physiological responses to cold?
Shivering, vasoconstriction, piloerection (raising of body hair)
146
Describe the second messenger model.
- adrenaline binds to transmembrane protein receptor on CSM of liver cell
- binding of adrenaline causes the protein to change shape
- leads to activation of the enzyme adenyl cyclase
- cAMP acts as a second messenger that binds to kinase enzyme
- active protein kinase catalyses conversion of glycogen to glucose
147
Which cells in the pancreas are involved in blood sugar control?
Islets of Langerhans
148
What are the islets of Langerhans?
Alpha cells
Beta cells
149
Describe the role of alpha cells in the pancreas.
Secrete glucagon
150
Describe the role of beta cells.
Secrete insulin
151
Insulin and glucagon are a___________ hormones.
Antagonistic
152
153
What are the 3 processes of blood glucose control that occur in the liver?
Glycogenesis
Glycogenolysis
Gluconeogenesis
154
Describe glycogenesis.
Glycgogenesis is the synthesis of glycogen from glucose molecules
Insulin triggers this process after it detects an increased blood glucose concentration
155
Describe glycogenolysis
Glycogenolysis is the breakdown of glycogen to produce glucose molecules
Glucagon triggers this process after it detects a decreased blood glucose concentration
156
Describe gluconeogenesis
Gluconeogenesis is the synthesis of glucose molecules from non-carbohydrate molecules
157
Describe the role of insulin in regulating blood glucose concentration.
- a change in the tertiary structure of glucose transport carrier proteins happens. They change shape to open allowing more glucose in by facilitated diffusion
- glucose carrier proteins (that are present as vesicles in the CSM at low insulin concentration) become fused with CSM at high concentrations of insulin - increasing the number of glucose transport channels
158
Describe how blood sugar is regulated when blood sugar level rises.
- rise is detected by beta cells of islets of Langerhans in pancreas
- insulin released into the blood and binds to receptors on liver and muscle cells
- glucose transport proteins open and glucose enters cells
- enzymes are stimulated to convert glucose to glycogen OR glucose is converted into triglycerides OR rate of respiration is increased
- blood sugar level falls
159
Describe how blood sugar levels are regulated when the blood sugar level falls.
- detected by alpha cells of islets of Langerhans in pancreas
- glucagon released into the blood. Glucagon binds to receptors on liver cells only
- glycogenolysis: glycogen broken down into glucose OR gluconeogeneis: glycerol and amino acids are converted into glucose
- glucose enters the blood
- blood sugar level rises
160
161
what are the 2 functions of the kidneys?
- as an osmoregulatory organ - they regulate the water content of the blood
- as a excretory organ - they excrete the toxic waste products of metabolism (urea) and substances in excess of requirements (salts)
162
What is the function of the Renal artery?
Carries oxygenated blood (containing urea and salts) to the kidneys
163
What is the function of the Renal vein?
Carries deoxygenated blood (that has has urea and excess salts removed) away from the kidneys
164
What is the function of the kidney?
Regulates water content of the blood and filters blood
165
What is the function of the ureter?
Carries urine from the kidneys to bladder
166
What is the function of the bladder?
Stores urine (temporarily)
167
What is the function of the urethra?
Releases urine outside of the body
168
What are the 3 main elements beneath the fibrous capsule in the kidneys?
Cortex
Medulla
Renal pelvis
169
What does the cortex contain?
Glomerulus
Bowman’s capsule
Proximate convoluted tubule
Distal convoluted tubule of the nephrons
170
What does the medulla contain?
The loop of Henle
Collecting duct of the nephrons
171
What structure is within Bowman’s capsule?
Glomerulus
172
What supplies the glomerulus with blood?
Afferent arteriole (carries blood from the renal artery)
173
The capillaries of the glomerulus rejoin to form an….
Efferent arteriole
174
175
Where does ultrafiltration take place?
At the barrier between the blood in the glomerulus and the filtrate in the renal capsule
176
Ultrafiltration takes place due to the _______ maintained by the afferent and efferent arterioles.
Pressure
177
Why does blood pressure rise in the glomerulus in ultrafiltration?
The efferent arteriole is narrower than the afferent arteriole, so pressure rises as blood enters the glomerulus
178
What are the elements of the three-part filter?
Endothelium of blood capillary
Basement membrane
Epithelium of renal capsule
179
Describe the endothelium of the blood capillary in the three part filter.
Thin
Perforated with thousands of pores
Provides a barrier to cells but not plasma proteins
180
Describe the basement membrane in the three part filter.
- meshwork of collagen and glycoprotein fires
- water and small molecules can pass through
- proteins are too large and are repelled by negative charges on fibres
181
Describe the epithelium of the renal capsule in the three-part filter.
Made of podocytes which are modified for filtration
182
Describe the structure of a podocyte.
- has foot-like extensions projecting from its surface which wrap around the capillaries of the glomerulus and interlink with extensions from neighbouring cells
- these extensions fit together leaving filtration slits where fluid can pass through
183
What are some of the molecules that can pass through the three-part filter?
Ions
Water
Glucose
Amino acids
184
What molecules cannot fit through the three part filter and remain in the capillary?
Cells
Platelets
Plasma proteins
185
Where does selective reabsorption take place?
Loop of Henle
186
What adaptations does the PCT have for reabsorbtion?
Microvilli - large surface area to transfer substances back into capillaries
High density of mitochondria to provide ATP for active transport
187
Describe the process in the PCT during reabsorption?
- Na+ pass out of cells that line the PCT by active transport into blood capillaries which carry them away. Na_ contents of cells lowered
- Na+ now diffuse down a concentration gradient from the lumen out of the PCT into epithelia cells through carrier proteins by facilitated diffusion
- these carrier proteins also carry another molecule e.g glucose with the Na+ (co-transport)
- the molecules which have been co-transported into the cells of the PCT then diffuse into the blood
-all the glucose and most other valuable molecules are reabsorbed
188
What are the 3 elements of the loop of henle?
Descending limb
Medulla
Ascending limb
189
Describe reabsorption in the descending limb of the loop of henle.
As the fluid in the tubule descends into the medulla down the descending loop, the water potential becomes lower (more negative)
This is due to:
- the walls are permeable to water
- water leaves by osmosis into the surrounding tissue fluid
- sodium and chloride ions move into the tubule from surrounding fluid
190
The descending limb of the loop of henle is ____________ to water
Permeable
191
Describe reabsorption in the ascending limb of the loop of henle.
As fluid in the tubule ascends back up towards the Cortex the water potential becomes higher (less negative)
This is due to:
- sodium and chloride ions diffusing out of the tubule into the tissue fluid at the base
- higher up the tubule, sodium and chloride ions are actively transported out into the tissue fluid
- the wall of the ascending limb is impermeable to water so it cannot leave the tubule
192
Where does fluid pass to from the ascending limb?
Distal convoluted tubule
193
What happens in the distal convoluted tubule in reabsorption?
Active transport adjust the concentration of various salts in the tube
194
Describe what happens in the collecting duct in reabsorption.
- when fluid reaches the collecting duct it as a high water potential (less negative)
- the collecting duct carries fluid back into the medulla which contains lots of salts
- therefore as the fluid passes through, water moves by osmosis from the tubule into the surrounding tissue
- it the enters the blood capillaries by osmosis and is carried away
195
The walls of the collecting duct can be made more or less ________ to water according to the needs of the body.
Permeable
196
What is the permeability of the collecting duct controlled by?
ADH (hormone)
197
Describe the process of making the collecting duct more permeable to water.
- ADH binds to receptors on the cel wall of the collecting duct
- this causes a chain of enzyme controlled reactions inside the cell
- vesicles fuse with the CSM which contain aquaporins
- these make the walls more permeable to water
- more ADH in the blood means more aqauporins are inserted allowing more water to be reabsorbed and more concentrated urine
198
What happens to the collecting duct when there is less ADH in the blood?
- less water is absorbed
- this is excuse the CSM folds inwards to create new vesicles that remove them aqauporins from the membrane
- the wall is less permeable and more water passes out in urine with a higher (less negative) water potential
199
How is ADH produced?
- osmoreceptors in the hypothalamus monitor the blood’s water potential
- when the water potential is low, these cells loose water by osmosis and shrink, stimulating neurosecretory cells
- neurosecretory cells produce ADH which flows into the posterior pituitary glans where is is stored until needed
200
Where is ADH stored?
Posterior pituitary gland
201
Where are osmoreceptors found?
Hypothalamus
202
What is type 1 diabetes caused by?
Caused by the insulin producing cells in the pancreas being destroyed by the body’s own immune system
203
What is type 2 diabetes controlled by?
Caused by the body’s own cells e.g liver and muscle cells being unable to respond to insulin and can sometimes be due to diet and lifestyle
204
What is type 1 diabetes controlled by?
Injections of insulin or oral medications
205
What is type 2 diabetes controlled by?
Healthy diet, avoiding high sugar food and doing exercise
206
What are the symptoms of diabetes?
Thirst
Frequent urination
Weight loss
Tiredness
Fatigue
Blurred vision
207
What are some of the possible impact of diabetes?
Weight loss
Kidney damage
Heart attack
Stroke
Blindness
Death
