Responding To Changes In Environment - 6 Flashcards
(191 cards)
1
Q
What is a stimulus?
A
A detectable change in the environment detected by cells called receptors.
2
Q
What comprises the central nervous system?
A
The brain and spinal cord.
3
Q
What comprises the peripheral nervous system?
A
Receptors, sensory and motor neurones.
4
Q
What are the steps in a simple reflex arc?
A
Stimulus → receptor → sensory neurone → coordinator (CNS / relay neurone) → motor neurone → effector (muscle) → response (contraction).
5
Q
What are the importance of simple reflexes?
A
They are rapid, involve a short pathway, consist of only three neurones and few synapses, are autonomic, and do not involve conscious thought.
6
Q
How do simple reflexes protect from harmful stimuli?
A
They provide a quick response to prevent injury, such as pulling away from a burning object.
7
Q
What is tropism?
A
Response of plants to stimuli via growth.
8
Q
What are the two types of tropism?
A
Positive (growing towards stimulus) and negative (growing away from stimulus).
9
Q
What controls tropism in plants?
A
Specific growth factors, such as Indoleacetic acid (IAA).
10
Q
What is phototropism?
A
Response of plants to light.
11
Q
What is gravitropism?
A
Response of plants to gravity.
12
Q
What is hydrotropism?
A
Response of plants to water.
13
Q
What is Indoleacetic acid (IAA)?
A
Type of auxin (plant hormone) that controls cell elongation in shoots and inhibits growth of cells in roots.
14
Q
Where is IAA produced?
A
Made in tips of roots and shoots.
15
Q
How does IAA affect shoots?
A
IAA diffuses to other cells and accumulates on the shaded side of the shoot, stimulating cell elongation.
16
Q
What is positive phototropism?
A
When the plant bends towards light due to IAA accumulation on the shaded side.
17
Q
What is phototropism in roots?
A
Root tip produces IAA. IAA concentration increases on lower (darker) side. IAA inhibits cell elongation, causing root cells to grow on the lighter side, resulting in the root bending away from light.
This is an example of negative phototropism.
18
Q
What is gravitropism in shoots?
A
Shoot tip produces IAA, which diffuses from the upper side to the lower side of the shoot in response to gravity. IAA stimulates cell elongation, allowing the plant to grow upwards.
This is an example of negative gravitropism.
19
Q
What is gravitropism in roots?
A
Root tip produces IAA, which accumulates on the lower side of the root in response to gravity. IAA inhibits cell elongation, causing the root to bend down towards gravity and anchor the plant.
This is an example of positive gravitropism.
20
Q
What is taxis?
A
Directional response by simple mobile organisms, moving towards favourable stimuli (positive taxis) or away from unfavourable stimuli (negative taxis).
21
Q
What is Kinesis?
A
When an organism changes its speed of movement and rate of change of direction in response to a stimulus.
22
Q
What happens if an organism moves to a region of unfavourable stimuli?
A
It will increase its rate of turning to return to the origin.
23
Q
What occurs if an organism is surrounded by negative stimuli?
A
The rate of turning decreases, causing the organism to move in a straight line.
24
Q
What are receptors?
A
They respond to specific stimuli.
25
What happens when a receptor is stimulated?
It leads to the establishment of a generator potential, causing a response.
26
What are examples of receptors?
Pacinian corpuscle, rods, and cones.
27
What does the Pacinian corpuscle respond to?
Pressure changes.
28
Where do Pacinian corpuscles occur?
Deep in the skin, mainly in fingers and feet.
29
What is the structure of a Pacinian corpuscle?
A sensory neurone wrapped with layers of tissue.
30
What are the components of the outer capsule of a Pacinian corpuscle?
Lamellae, sensory neurone, and Schwann cell.
31
How do Pacinian corpuscles detect pressure?
When pressure is applied, stretch-mediated sodium ion channels are deformed, allowing sodium ions to diffuse into the sensory neurone. This influx increases membrane potential, establishing a generator potential.
32
Where are rod cells concentrated?
Rod cells are concentrated at the periphery of the retina.
33
What pigment do rod cells contain?
Rod cells contain rhodopsin pigment.
34
How are rod cells connected to bipolar cells?
Rod cells are connected in groups to one bipolar cell, indicating retinal convergence.
35
Do rod cells detect color?
No, rod cells do not detect color.
36
Where are cone cells concentrated?
Cone cells are concentrated on the fovea.
37
How many types of cone cells are there?
There are three types of cones, each containing different iodopsin pigments.
38
How are cone cells connected to neurones?
One cone connects to one neurone.
39
Do cone cells detect color?
Yes, cone cells detect colored light.
40
What is the sensitivity of rod cells to light?
Rods are more sensitive to light.
41
What is the sensitivity of cone cells to light?
Cones are less sensitive to light.
42
What is the visual acuity of cones?
Cones give higher visual acuity.
43
What is the visual acuity of rods?
Rods have a lower visual acuity.
44
What is visual acuity?
The ability to distinguish between separate sources of light. A higher visual acuity means more detailed, focused vision.
45
What type of vision do rods allow?
Rods allow monochromatic vision (black and white).
46
What type of vision do cones allow?
Cones allow colour vision.
47
Why do rods have high sensitivity to light?
Rods are connected in groups to one bipolar cell, leading to retinal convergence and spatial summation. Stimulation of each individual cell alone is sub-threshold, but because rods are connected in groups, it is more likely that threshold potential is reached.
48
Why do cones have low sensitivity to light?
One cone joins to one neurone; no retinal convergence or spatial summation; higher light intensity required to reach threshold potential.
49
Why do rods have low visual acuity?
Rods are connected in groups to one bipolar cell; retinal convergence and spatial summation occur; many neurones only generate 1 impulse/action potential, which cannot distinguish between separate sources of light.
50
Why do cones have high visual acuity?
One cone joins to one neurone; if 2 adjacent cones are stimulated, the brain receives 2 impulses, allowing it to distinguish between separate sources of light.
51
Why do rods have monochromatic vision?
There is one type of rod cell with one pigment (rhodopsin).
52
What are the types of cone cells involved in color vision?
There are three types of cone cells: red-sensitive, green-sensitive, and blue-sensitive cones.
53
How do cone cells contribute to color perception?
Stimulation of different proportions of cones gives a greater range of color perception.
54
What is myogenic muscle?
Myogenic muscle, such as cardiac muscle, can contract and relax without receiving signals from nerves.
55
What is the sinoatrial node?
The sinoatrial node is located in the right atrium and is known as the pacemaker.
56
What does the sinoatrial node do?
It releases a wave of depolarization across the atria, causing muscles to contract.
57
Where is the atrioventricular node located?
The atrioventricular node is located near the border of the right and left ventricle within the atria.
58
What is the function of the atrioventricular node?
It releases another wave of depolarization after a short delay when it detects the first wave from the sinoatrial node.
59
What is the Bundle of His?
A structure that runs through the septum and can conduct and pass the wave of depolarisation down the septum and Purkyne fibres in the walls of ventricles.
60
What are Purkyne fibres?
Fibres located in the walls of ventricles that spread the wave of depolarisation from the AVN across the bottom of the heart.
## Footnote
The muscular walls of ventricles contract from the bottom up.
61
What is the role of non-conductive tissue?
Located between the atria and ventricles, it prevents the wave of depolarisation from travelling down to the ventricles, causing a slight delay in ventricular contraction.
62
Why is there a short delay between SAN and AVN waves of depolarisation?
To ensure enough time for the atria to pump all blood into the ventricles, allowing the ventricle to become full.
63
What is the role of the medulla oblongata?
Controls heart rate via the autonomic nervous system.
64
How does the medulla oblongata control heart rate?
Uses sympathetic and parasympathetic nervous system to control SAN rhythm.
65
Where are chemoreceptors located?
In the carotid artery and aorta.
66
What do chemoreceptors respond to?
pH / CO2 concentration changes.
67
Where are baroreceptors located?
In the carotid artery and aorta.
68
What do baroreceptors respond to?
Pressure changes.
69
What is the response to high blood pressure?
Baroreceptor detects high blood pressure.
70
What happens after a baroreceptor detects high blood pressure?
Impulse sent to the medulla.
71
What occurs after the impulse is sent to the medulla?
More impulses sent to SAN via parasympathetic neurones (releasing acetylcholine).
72
What is the effect of increased parasympathetic impulses on heart rate?
Fewer impulses from SAN, leading to a slowed heart rate.
73
What detects low blood pressure?
Baroreceptor detects low blood pressure.
74
What happens after the baroreceptor detects low blood pressure?
Impulse sent to the medulla.
75
What is released along sympathetic neurones when responding to low blood pressure?
Noradrenaline is released.
76
What is the effect on heart rate in response to low blood pressure?
Heart rate increases.
77
What detects low CO2 concentration or high pH?
Chemoreceptor detects low CO2 concentration/high pH.
78
What happens after the chemoreceptor detects low CO2 concentration/high pH?
Impulse sent to medulla.
79
What is released along parasympathetic neurones when responding to high blood pH?
Acetylcholine is released.
80
What is the effect on heart rate in response to high blood pH?
Heart rate slows.
81
What detects high CO2 concentration or low pH?
Chemoreceptor detects high CO2 concentration/low pH.
82
What happens after the chemoreceptor detects high CO2 concentration/low pH?
Impulse sent to medulla.
83
What is released along sympathetic neurones when responding to low blood pH?
Acetylcholine is released.
84
What is the effect on heart rate in response to low blood pH?
Heart rate increases to deliver blood to heart to remove CO2.
85
What are the main structures of a myelinated motor neurone?
Dendrite, Axon Terminal, Node of Ranvier, Cell body, Axon, Schwann cell, Myelin sheath, Nucleus.
86
What is resting potential?
The difference between electrical charge inside and outside the axon when a neuron is not conducting an impulse.
## Footnote
More positive ions (Na+/K+) outside axon compared to inside; inside the axon is -70mV.
87
How is resting potential established?
The sodium potassium pump actively transports 3 Na+ out of the axon and 2 K+ into the axon. The membrane is more permeable to K+ (more channels and always open), allowing K+ to diffuse out down the concentration gradient. The membrane is less permeable to Na+ (closed Na+ channels) with a higher concentration of Na+ outside.
## Footnote
K+ diffuses out via facilitated diffusion.
88
What is action potential?
When the neuron's voltage increases beyond the -55mV threshold, generating a nervous impulse due to the membrane becoming more permeable to Na+.
## Footnote
Voltage-gated Na+ channels open, allowing Na+ to diffuse into the neuron down the concentration gradient, increasing the voltage across the membrane.
89
What happens when a threshold potential is reached?
An action potential is generated.
## Footnote
More voltage-gated Na+ channels open, allowing Na+ to move into the axon.
90
What occurs during depolarisation?
Na+ moves by facilitated diffusion down the concentration gradient into the axon, making the inside more positive.
91
What happens during repolarisation?
Na+ channels close, making the membrane less permeable to Na+. K+ voltage-gated channels open, allowing K+ to diffuse out of the neuron.
## Footnote
This causes the voltage to rapidly decrease.
92
What is hyperpolarisation?
K+ channels are slow to close, causing an overshoot in voltage. Too many K+ diffuse out of the neuron, decreasing the potential difference to -80mV.
93
How is the resting potential restored?
The sodium-potassium pump returns the neuron to resting potential.
94
What does the action potential graph depict?
It shows depolarisation, repolarisation, and hyperpolarisation phases.
95
What is the all or nothing principle?
If depolarisation does not exceed -55 mV threshold, action potential is not produced. Any stimulus that does trigger depolarisation to -55mV will always peak at the same maximum voltage.
## Footnote
Ensures animals only respond to large enough stimuli rather than responding to every small change in environment.
96
What is the importance of the all or nothing principle?
It ensures that animals only respond to large enough stimuli, preventing overwhelming responses to small changes in the environment.
97
What is the refractory period?
After an action potential has been generated, the membrane enters a period where it cannot be stimulated because Na+ channels are recovering and cannot be opened.
## Footnote
This ensures discrete impulses are produced, as action potentials are separate and cannot be generated immediately.
98
What is the importance of the refractory period?
It limits the number of impulse transmissions, preventing overwhelming responses and ensuring that action potentials are unidirectional.
99
What factors affect the speed of conductance?
Myelination, axon diameter, and temperature increase speed.
100
How does myelination affect speed?
Myelination increases speed by allowing depolarisation to occur at Nodes of Ranvier only, leading to saltatory conduction.
101
What is saltatory conduction?
Impulse jumps from node to node in myelinated neurons.
102
How does axon diameter affect speed?
Larger axon diameter increases speed.
103
How does temperature affect speed?
Higher temperature increases speed due to increased kinetic energy.
104
What is the effect of myelination on ion leakage?
Myelination reduces leakage of ions, increasing speed of conductance.
105
How does temperature influence ion movement?
Higher temperature increases the rate of movement of ions due to more kinetic energy.
106
What is the relationship between respiration rate and speed of conductance?
Higher rate of respiration leads to faster enzyme activity, producing ATP faster, which enhances active transport.
107
What is saltatory conduction?
Saltatory conduction is the process where action potentials jump from node to node along a myelinated axon, allowing for faster transmission of impulses.
108
What are nodes of Ranvier?
Nodes of Ranvier are gaps between the myelin sheath on an axon where action potentials can jump during saltatory conduction.
109
What is the role of calcium ions in synaptic transmission?
Calcium ions (Ca2+) diffuse into the pre-synaptic knob when voltage-gated channels open, stimulating vesicles to release neurotransmitters into the synaptic cleft.
110
Why are synapses unidirectional?
Synapses are unidirectional because neurotransmitters are only released from the pre-synaptic neurone and receptors are only present on the post-synaptic membrane.
111
What happens to excess neurotransmitters in the synaptic cleft?
Enzymes in the synaptic cleft break down excess unbound neurotransmitters, establishing a concentration gradient between the pre- and post-synaptic neurone.
112
What is the neurotransmitter involved in cholinergic synapses?
The neurotransmitter is acetylcholine.
113
What enzyme breaks down acetylcholine?
The enzyme that breaks down acetylcholine is acetylcholine-esterase.
114
What does acetylcholine-esterase break acetylcholine down into?
It breaks down acetylcholine to acetate and choline to be recycled in the pre-synaptic neurone.
115
What are the two methods for rapid build-up of neurotransmitters in the synapse?
The two methods are spatial summation and temporal summation.
116
Why is summation required in cholinergic synapses?
Summation is required because some action potentials do not result in sufficient concentrations of neurotransmitters released to generate a new action potential.
117
What is spatial summation?
Many different neurones collectively trigger a new action potential by combining the neurotransmitter they release to exceed the threshold value.
## Footnote
Example: Retinal convergence for rod cells.
118
What is temporal summation?
When one neurone releases neurotransmitters repeatedly over a short period of time to exceed the threshold value.
## Footnote
Example: Cone cell signalling one image to the brain.
119
What is the function of inhibitory synapses?
Inhibitory synapses cause chloride ions (Cl-) to move into the post-synaptic neurone and K+ to move out, making the membrane hyperpolarized (more negative) and less likely to propagate an action potential.
120
What is a neuromuscular junction (NMJ)?
A neuromuscular junction is a synapse that occurs between a motor neurone and a muscle.
121
How does a cholinergic synapse differ from a neuromuscular junction?
Cholinergic synapses are bidirectional and only excitatory, connecting two neurones (sensory/relay/motor), while NMJs connect motor neurones to muscles and serve as the endpoint for action potentials.
122
What happens when acetylcholine (Ach) binds to receptors on muscle fibers?
When Ach binds to receptors on muscle fibers, it generates a new action potential in the muscle.
123
What is the structure of myofibrils?
Myofibrils are made up of fused cells that share nuclei/cytoplasm (sarcoplasm) and contain many mitochondria.
124
What is the relationship between muscle fibers and myofibrils?
Millions of muscle fibers make up myofibrils, which are responsible for bringing about movement.
125
What role does Ca2+ play in the sliding filament theory?
Ca2+ enters from the sarcoplasmic reticulum and causes tropomyosin to change shape, exposing binding sites on actin.
126
What is the function of tropomyosin in the sliding filament theory?
Tropomyosin covers binding sites on actin filaments. When Ca2+ binds to tropomyosin, it changes shape and exposes these binding sites.
127
How does ATP contribute to myofibril contraction?
ATP activates ATPase on myosin, leading to hydrolysis of ATP into ADP + Pi, which releases energy for myosin heads to recock and detach.
128
What happens during the power stroke in muscle contraction?
The movement of myosin heads pulls actin, resulting in the power stroke.
129
What occurs after the power stroke?
ATP binds to the myosin head, causing it to detach and break the cross bridge.
130
What is the process for returning Ca2+ to the sarcoplasmic reticulum?
There is active transport of Ca2+ back to the sarcoplasmic reticulum.
131
What is the role of myosin in myofibril contraction?
Myosin heads (with ADP attached) attach to binding sites on actin, forming actin-myosin cross bridges. The power stroke occurs as myosin heads move, pulling actin. ATP is required to release energy and break the cross bridge so myosin heads can move further along actin.
132
What is phosphocreatine?
A chemical stored in muscles that can rapidly regenerate ATP from ADP by providing a Pi group when ATP concentration is low.
133
What are slow-twitch muscle fibres specialized for?
Slow-twitch muscle fibres are specialized for slow, sustained contractions (endurance). They have lots of myoglobin, many mitochondria for high rates of aerobic respiration, and many capillaries to supply high concentrations of glucose/O2 and prevent lactic acid build-up.
## Footnote
Examples include thighs and calves.
134
What are fast-twitch muscle fibres specialized for?
Fast-twitch muscle fibres are specialized in producing rapid, intense contractions of short duration. They hydrolyze glycogen to glucose through glycolysis and have a higher concentration of enzymes involved in anaerobic respiration for fast glycolysis, along with phosphocreatine stores.
## Footnote
Examples include eyelids and biceps.
135
What is homeostasis?
Maintenance of constant internal environment via physiological control systems.
## Footnote
It controls temperature, blood pH, blood glucose concentration, and water potential within limits.
136
What happens when there is a deviation from normal values in homeostasis?
Restorative systems are put in place to return this back to the original level.
## Footnote
This involves the nervous system and hormones.
137
What are the Islets of Langerhans?
Region in the pancreas containing cells involved in detecting changes in blood glucose levels.
## Footnote
It contains endocrine cells (alpha cells and beta cells) which release hormones to restore blood glucose levels.
138
What do alpha cells do?
Release glucagon when they detect blood glucose concentration is too low.
139
What are beta cells?
Beta cells are located in the islets of Langerhans and release insulin when they detect that blood glucose concentration is too high.
140
What triggers the release of insulin?
The release of insulin is triggered by eating food containing carbohydrates, which results in glucose being absorbed from the intestine into the blood.
141
How does exercise affect blood glucose levels?
Exercise increases the rate of respiration, using glucose.
142
What is the action of insulin on liver cells?
Insulin binds to specific receptors on the membranes of liver cells, increasing the permeability of the cell membrane by facilitating the fusion of GLUT-4 channels.
143
What happens to glucose when insulin is present?
Glucose can enter from the blood into liver cells by facilitated diffusion.
144
What is glycogenesis?
Glycogenesis is the process activated by insulin in the liver, where glucose is converted into glycogen.
145
What is the effect of glucagon on liver cells?
Glucagon binds to specific receptors on the membranes of liver cells, activating enzymes for glycogenolysis and gluconeogenesis.
146
What happens to blood glucose concentration when glucagon is active?
When glucagon is active, the rate of respiration decreases and blood glucose concentration increases.
147
What is the role of adrenaline?
Secreted by adrenal glands above the kidney for fight or flight.
148
What does adrenaline activate?
Activates secretion of glucagon.
149
What processes does adrenaline stimulate?
Glycogenolysis and gluconeogenesis.
150
How does adrenaline work?
Works via secondary messenger model.
151
What is gluconeogenesis?
Creating glucose from non-carbohydrate stores in the liver, e.g., amino acids.
152
When does gluconeogenesis occur?
Occurs when all glycogen has been hydrolyzed and the body requires more glucose.
153
What initiates gluconeogenesis?
Initiated by glucagon when blood glucose concentrations are low.
154
What is glycogenolysis?
Hydrolysis of glycogen back into glucose.
155
What causes glycogenolysis?
Occurs due to the action of glucagon to increase blood glucose concentration.
156
What is glycogenesis?
Process of glucose being converted to glycogen when blood glucose is higher than normal.
157
What causes glycogenesis?
Caused by insulin to lower blood glucose concentration.
158
What is a second messenger model?
A process where stimulation of a molecule (usually an enzyme) leads to further stimulation of more molecules to bring about a desired response.
159
What role do adrenaline and glucagon play in the second messenger model?
They cause glycogenolysis to occur inside the cell when binding to receptors on the outside.
160
How do adrenaline and glucagon interact with cells?
They bind to specific complementary receptors on the cell membrane.
161
What does adenylate cyclase do?
It is activated by adrenaline/glucagon and converts ATP to cyclic AMP (secondary messenger).
162
What is the function of cyclic AMP (cAMP)?
cAMP activates protein kinase A (enzyme).
163
What is the role of protein kinase A?
It activates a cascade to break down glycogen to glucose (glycogenolysis).
164
What is Type 1 diabetes?
A disease when blood glucose concentration cannot be controlled naturally.
165
What causes Type 1 diabetes?
The body is unable to produce insulin due to an autoimmune disease where beta cells are attacked.
166
When does Type 1 diabetes typically start?
It usually starts in childhood.
167
How is Type 1 diabetes treated?
It is treated using insulin injections.
168
What is Type 2 diabetes?
A condition where receptors in target cells lose responsiveness to insulin, usually developing due to obesity and poor diet.
## Footnote
Treated by controlling diet, increasing exercise, and insulin injections.
169
What is osmoregulation?
The process of controlling the water potential of the blood, regulated by hormones such as antidiuretic hormone.
## Footnote
Affects the distal convoluted tubule and collecting duct.
170
What is a nephron?
The structure in the kidney where useful substances are reabsorbed into the blood.
## Footnote
Includes components like the proximal convoluted tubule and the collecting duct.
171
What is the function of the proximal convoluted tubule?
Reabsorbs useful substances from the filtrate back into the blood.
172
What is the ascending loop of the nephron?
Part of the nephron that helps in the reabsorption process.
173
What is the diameter of the efferent arteriole compared to the afferent arteriole?
The diameter of the efferent arteriole is smaller than the afferent arteriole.
174
What is the result of the smaller diameter of the efferent arteriole?
It leads to a build-up of hydrostatic pressure.
175
What substances are squeezed out of the capillary into Bowman's capsule?
Water, glucose, and ions are squeezed out through pores in the capillary endothelium, basement membrane, and podocytes.
176
What happens to large proteins during glomerular filtration?
Large proteins are too large to pass through.
177
What mechanism is used for the reabsorption of glucose by the PCT?
A co-transport mechanism is used.
178
What do the walls of the PCT contain to aid in glucose reabsorption?
The walls are made of microvilli epithelial cells to provide a large surface area for diffusion of glucose into cells.
179
How is sodium transported in the PCT?
Sodium is actively transported out of cells into the intercellular space to create a concentration gradient.
180
What happens to glucose after sodium is transported out of the PCT cells?
Glucose can then diffuse into the blood again.
181
What does the counter current multiplier mechanism describe?
It describes how to maintain a gradient of Na+ in the medulla by the loop of Henle.
182
How is Na+ transported in the loop of Henle?
Na+ is actively transported out of the ascending limb to the medulla to lower water potential.
183
How does water move out of the descending limb, DCT, and collecting duct?
Water moves out by osmosis due to the water potential gradient.
184
What controls the movement of water out of the DCT and collecting duct?
It is controlled by ADH, which changes the permeability of membranes to water.
185
What is the role of the hypothalamus in osmoregulation?
The hypothalamus contains osmoreceptors that detect changes in water potential and produces ADH.
186
What happens when blood has low water potential?
Osmoreceptors shrink and stimulate more ADH to be made, leading to more ADH being released from the pituitary gland.
187
Where is ADH produced and released?
ADH is produced by the hypothalamus and released by the pituitary gland.
188
How does ADH affect the kidneys?
ADH affects the permeability of the walls of the collecting duct and DCT to water, leading to more water reabsorbed back to the blood.
189
What is the effect of more ADH on urine concentration?
More ADH means more aquaporins fuse with walls, resulting in more water reabsorbed and more concentrated urine.
190
How does ADH travel from the hypothalamus to the kidneys?
ADH moves to the pituitary gland from the hypothalamus, is released into capillaries, and travels through the blood to the kidneys.
191
What structures are involved in synapse?
Synaptic vesicle, voltage-gated Ca2+ channel, post-synaptic density, neurotransmitters, neurotransmitter re-uptake pump, axon terminal, neurotransmitter receptors, and synaptic cleft.
