Homeostasis Flashcards
(187 cards)
1
Q
Homeostasis Definition:
A
The process that regulates the internal environment within a narrow range to maintain stable conditions necessary for survival.
2
Q
Why is homeostasis important for enzymes?
A
Because enzymes require specific conditions (like pH, temperature, and solute levels) to function. If these conditions aren’t met, it can be deadly.
3
Q
What are the four components of a homeostatic system?
A
Stimulus, Sensor, Control Centre, Effector.
4
Q
What is the role of the stimulus in homeostasis?
A
It is the variable being measured that indicates deviation from the set point.
5
Q
What is the function of the sensor (or receptor)?
A
It monitors the variable and sends data to the control centre.
6
Q
What does the control centre do?
A
Compares the current data to the set point and sends instructions to effectors if needed.
7
Q
What is the effector’s job in homeostasis?
A
It carries out the response to restore the variable to its normal range.
8
Q
What is a negative feedback loop?
A
A process that counteracts a change to bring a system back to its set point.
9
Q
What is a positive feedback loop? Give an example.
A
A process that increases the change or output. Example: Contractions during childbirth.
10
Q
Example of temperature regulation through negative feedback?
A
Body temp > 37°C – Nerve sensors detect – Brain control centre – Sweating lowers body temp.
11
Q
What is diffusion?
A
The net movement of atoms or molecules down their concentration gradient, from high concentration to low concentration.
12
Q
What is osmosis?
A
The diffusion of water across a semi-permeable membrane from low solute concentration to high solute concentration.
13
Q
What does it mean if a membrane is permeable to water?
A
Water can pass through it.
14
Q
What does it mean if a membrane is impermeable to water?
A
Water cannot pass through it.
15
Q
What role does water play in the human body?
A
All chemical reactions in the body occur in the presence of water.
16
Q
What is the relationship between oxygen and carbon dioxide in the body?
A
They are inversely proportional – as one increases, the other decreases.
17
Q
What is glucose regulation?
A
The process by which the body maintains stable blood sugar levels, primarily through insulin and glucagon.
18
Q
What is temperature regulation?
A
The body’s method of maintaining a stable internal temperature, typically around 37°C.
19
Q
Why must solutes and pH be tightly regulated in the body?
A
To ensure proper enzyme function and prevent cell damage or death.
20
Q
What does the effector do?
A
An effector is an organ, gland, or muscle or cells capable of being activated by nerve endings or a hormone and reads the input from the control centre and brings about an output that brings about a response (altering of the stimulus).
21
Q
The nervous system communicates via…
A
Electric signals
22
Q
The endocrine system communicates via…
A
Chemical Signals
23
Q
T or F: Diffusion is a passive transport (does not require energy)
A
True
24
Q
How are receptors and effectors connected in vertebrates?
A
Via control centres using nervous, hormonal, or both pathways.
25
What is homeostasis?
The regulation of internal conditions within a narrow range, despite changes in external or internal environments.
26
What is the stimulus-response model in homeostasis?
It includes a stimulus, sensor (receptor), control centre, effector, and response to maintain internal balance.
27
What is negative feedback?
A process where the body counters a change to return to normal conditions.
28
What is positive feedback?
A process where the body amplifies a change (e.g., childbirth contractions).
29
What are the four key components of a feedback loop?
Stimulus → Sensor → Control Centre → Effector.
30
How are receptors and effectors connected in vertebrates?
Via control centres using nervous, hormonal, or both pathways.
31
What are neural pathways?
Networks of neurons that transmit impulses from receptors to effectors.
32
What is an action potential?
Action potential is a rapid, temporary change in the electrical potential across a neuron’s membrane, where the inside of the cell becomes briefly positive compared to the outside. It occurs when a neuron sends a signal down its axon in response to a stimulus.
33
What is synaptic transmission?
The process of neurotransmitters carrying signals across synapses between neurons.
34
What is signal transduction?
Signal transduction is the process by which a cell responds to signals from its environment. It involves a series of molecular steps that convert an external signal (like a hormone or neurotransmitter) into a specific cellular response, such as gene activation or a change in cell behavior. Conversion of a signal into a cellular response, often via neurotransmitters or hormones.
35
What do hormones do?
They act as chemical messengers in the bloodstream, coordinating and regulating physiological processes—such as growth, metabolism, reproduction, stress responses, and fluid balance—to maintain the body’s internal stability (homeostasis).
36
How are hormones transported in the body?
Via the circulatory or lymphatic system to target tissues or organs.
37
What is thermoregulation?
The maintenance of a stable internal body temperature.
38
What is the stimulus-response model for thermoregulation?
Stimulus: ↑ or ↓ body temp → Sensor: Thermoreceptors in skin/brain → Control Centre: Hypothalamus → Effector: Sweat glands/muscles → Response: Sweating or shivering.
39
What are effectors involved in cooling the body?
Sweat glands (evaporation) and blood vessel dilation (heat loss).
40
What are effectors involved in warming the body?
Muscles (shivering), blood vessel constriction, increased metabolism.
41
What is glucose regulation?
The process of maintaining blood glucose levels within a narrow range.
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What is the stimulus-response model for glucose regulation?
Stimulus: ↑ or ↓ blood glucose → Sensor/Control: Pancreas → Effector: Liver, muscles → Response: Insulin or glucagon release.
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What does insulin do?
Lowers blood glucose by promoting glucose uptake and storage.
44
What does glucagon do?
Raises blood glucose by stimulating the liver to release glucose.
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What is osmoregulation?
The regulation of water and salt concentrations in the body.
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What is the stimulus-response model for osmoregulation?
Stimulus: ↑ or ↓ water concentration → Sensor: Hypothalamus → Control: Pituitary gland → Effector: Kidneys → Response: ADH release or inhibition.
47
What does ADH (antidiuretic hormone) do?
Increases water reabsorption in kidney nephrons, reducing urine volume.
48
What is the nephron’s role in osmoregulation?
Filters blood and reabsorbs water depending on ADH levels.
49
How is water transported from roots to leaves in plants?
Via xylem, driven by root pressure, cohesion, and transpiration.
50
What factors influence transpiration rate?
Light intensity, temperature, wind, and humidity.
51
What is transpiration?
The loss of water vapor from plant leaves through stomata.
52
What structural adaptations help desert animals conserve water?
Thick fur, reduced surface area, concentrated urine, nocturnal behavior.
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What behavioral responses help maintain water in arid environments?
Staying in shade, being active at night, burrowing.
54
What physiological responses assist water retention in desert animals?
Producing dry feces, reducing sweat, and efficient kidneys.
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What are xerophytes?
Plants adapted to dry environments with features like waxy leaves and sunken stomata.
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How do xerophytes reduce water loss?
Through structural features like thick cuticles, rolled leaves, and reduced stomata.
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What are Cranial Nerves
Nerves that go from the brain to the eyes nose, and other parts of the head.
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What are central nerves
Nerves in the brain and spinal chord
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What are peripheral nerves
Nerves that go from the spinal chord to the hands, arms, legs and feet.
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What are autonomic nerves
Nerves that go from the spinal chord to the lungs, heart, bladder, intestines, bladder and sex organs.
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Afferent nerves
The neuron signalling pathway leading towards the brain is the afferent pathway
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Efferent nerves
The pathway traveling away from the brain is the efferent pathway.
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Neural Pathways:
Neural pathways are networks of neurons (nerve cells) that carry electrical signals (nerve impulses) from:
Sensory receptors (detect stimuli like heat, pain, light)
➡️ to interneurons (in the brain or spinal cord),
➡️ to effectors (muscles or glands that carry out a response).
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Action Potential: The Electrical Signal
Once the receptor detects a stimulus, it triggers an electrical signal called an action potential.
This action potential travels along the axon of a neuron like a wave of voltage.
It's caused by the movement of ions (like sodium and potassium) across the neuron's membrane.
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Synaptic Transmission: Jumping the Gap
Neurons don’t touch each other directly. They’re separated by tiny gaps called synapses.
So how does the signal keep going?
At the end of the first neuron, the action potential causes neurotransmitters to be released into the synapse.
These chemical messengers cross the gap and bind to receptors on the next neuron.
This triggers a new action potential in the next neuron.
66
Signal Transduction: Message Turned Into Action
Once the signal reaches the effector cell (like a muscle or gland), the message needs to be converted into a response.
This is called signal transduction:
The chemical message triggers a cellular response, such as a muscle contracting or a gland releasing a hormone.
67
What is endocytosis?
Endocytosis is a type of active transport where a cell engulfs substances from outside by folding its membrane inward to form a vesicle. This process requires energy (ATP) and is used to bring in large molecules or particles.
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What are the three types of endocytosis?
1. Phagocytosis ("cell eating") – takes in large solid particles.
2. Pinocytosis ("cell drinking") – takes in fluids and small dissolved substances.
3. Receptor-mediated endocytosis – uses receptors to target and engulf specific molecules.
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What is a vesicle in endocytosis?
A vesicle is a small membrane-bound sac formed when the cell membrane folds around material to transport it into the cell.
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How is endocytosis connected to other transport types?
• Like active transport, it requires energy.
• It differs from passive transport (like diffusion and facilitated diffusion), which doesn’t require energy and moves smaller molecules.
• Endocytosis allows intake of large or complex substances.
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What happens when material is too large for a protein channel?
The cell membrane bends around the material and forms a vesicle to transport it inside. This is endocytosis.
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What is the difference between phagocytosis and pinocytosis?
Phagocytosis is 'cell eating' (solids), and pinocytosis is 'cell drinking' (liquids).
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What is exocytosis?
Exocytosis is the process of moving large materials out of the cell using vesicles that fuse with the membrane.
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What is diffusion?
The movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached. It happens naturally and doesn't require energy.
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What is facilitated diffusion?
A type of diffusion where molecules move across a cell membrane through protein channels or carriers. It moves from high to low concentration and doesn't require energy.
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What is passive transport?
A general term for the movement of substances across a cell membrane without using energy. It includes both simple diffusion and facilitated diffusion.
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What is active transport?
The movement of substances across a membrane against their concentration gradient (from low to high concentration), which requires energy, usually in the form of ATP. Often involves protein pumps.
78
What is the resting membrane potential?
Resting potential is the electrical potential difference (voltage) across the membrane of a neuron or other excitable cell when it is not actively sending a signal. It is typically around –70 millivolts (mV) in neurons, with the inside of the cell being more negative than the outside.
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What is a typical resting membrane potential value in neurons?
–70 mV (approximately).
80
Which ion mainly leaks out of cells at rest?
Potassium (K⁺).
81
What pump maintains Na⁺ and K⁺ gradients?
Sodium–potassium ATPase (Na⁺/K⁺ pump).
82
What is the stoichiometry of the Na⁺/K⁺ pump?
3 Na⁺ out, 2 K⁺ in per ATP.
83
What energy source powers the Na⁺/K⁺ pump?
ATP hydrolysis.
84
What is an action potential?
Action potential is a rapid, temporary change in the electrical potential across a neuron’s membrane, where the inside of the cell becomes briefly positive compared to the outside. It occurs when a neuron sends a signal down its axon in response to a stimulus.
85
Where is the sodium–potassium pump located?
In the plasma membrane of cells.
86
Why is the Na⁺/K⁺ pump important?
It keeps Na⁺ low inside and K⁺ high inside, which is essential for cell function.
87
Give one role of the Na⁺/K⁺ pump besides maintaining resting membrane potential.
Regulating cell volume.
88
What is depolarization?
The process by which the membrane potential becomes less negative (moves toward zero) compared to its resting value.
89
What is the typical resting membrane potential before depolarization?
Around –70 mV.
90
Which channels open to start depolarization?
Voltage-gated Na⁺ channels.
91
Describe the movement of ions during depolarization.
Na⁺ rushes into the cell down its concentration and electrical gradients, bringing positive charge inside.
92
What is the approximate threshold for depolarization?
Around –55 mV.
93
What is the peak membrane potential during depolarization?
Approximately +30 mV.
94
What happens after depolarization?
Na⁺ channels inactivate and voltage-gated K⁺ channels open, allowing K⁺ to exit and repolarize the membrane.
95
Why is depolarization important?
It is the upstroke of the action potential, allowing rapid electrical signal transmission in nerves and muscle contraction.
96
How does an action potential start at one location on the axon?
A stimulus opens voltage-gated Na⁺ channels, causing depolarization at that site.
97
What causes adjacent regions of the axon to reach threshold?
Influx of Na⁺ creates positive charge that flows into neighboring regions, raising their membrane potential.
98
What are local circuit currents?
Local circuit currents are flows of ions between depolarized and resting regions that depolarize the next segment.
99
Why doesn't the action potential travel backward?
Because recently depolarized regions are temporarily inactivated and cannot open Na⁺ channels again.
100
What ensures the action potential moves in one direction?
Sequential opening of Na⁺ channels and refractory periods prevent backward flow.
101
How is the refractory period involved in propagation?
The refractory period in the just-active region prevents it from firing again immediately, directing the wave forward.
102
How does the membrane reset after the action potential passes?
After repolarization by K⁺ efflux, the Na⁺ channels return to a ready state, restoring the resting potential.
103
Does depolarization move along the axon?
Yes, it propagates as a wave along the axon.
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What drives depolarization to the next segment?
Local circuit currents of positive ions.
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Can the action potential travel backward?
No, because the previous segment is refractory.
106
What prevents a segment from depolarizing again immediately?
The refractory period of Na⁺ channels.
107
What type of channels does sodium use to enter neurons?
Voltage-gated sodium channels.
108
What allows ions to pass in and out of cells?
Protein channels in the cell membrane.
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What is a concentration gradient?
A difference in ion concentration across a membrane.
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What restores Na⁺ and K⁺ gradients during the refractory period?
The sodium–potassium pump.
111
What defines the resting membrane potential?
High Na⁺ outside and high K⁺ inside the neuron.
112
What triggers the depolarization threshold?
Electrical signals received by dendrites from other neurons or sensory organs.
113
Describe the distribution of Na⁺ and K⁺ at resting potential.
Na⁺ is high outside/low inside; K⁺ is high inside/low outside, making the inside negative.
114
What change is required for an action potential to move along a neuron?
A change in ion charge balance involving Na⁺ and K⁺.
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What is resting membrane potential
Resting potential is the electrical potential difference (voltage) across the membrane of a neuron or other excitable cell when it is not actively sending a signal. It is typically around –70 millivolts (mV) in neurons, with the inside of the cell being more negative than the outside.
116
Explain how the myelin sheath enables salutatory conduction
The myelin sheath is a fatty insulating layer that wraps around the axons of some neurons. It enables saltatory conduction, which means the electrical impulse “jumps” from one node of Ranvier to the next, rather than traveling continuously along the axon.
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What is a synapse?
The junction between the axon terminal of the pre-synaptic neuron and the dendrites of the post-synaptic neuron (or muscle).
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Stages in synaptic transmission
1. Depolarisation of the membrane at the axon terminal causes voltage-gated Ca2+ channels to open. Calcium ions flow into the neuron.
2. Synaptic vesicles containing neurotransmitters move towards the presynaptic membrane.
3. The neurotransmitter is released into the synaptic cleft, after the synaptic vesicle fuses with the membrane.
4. Chemically-gated ion channels open on the post-synaptic membrane; Na+ rushes in, K+ exits (depolarisation and repolarisation).
5. Enzymes degrade neurotransmitter so that their effect on the ion channels is short-lived.
6. Neurotransmitter molecules are reabsorbed into the synaptic vesicles.
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Signal transduction
The signal (nervous impulse) is converted from electrical to chemical to electrical.
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What are hormones?
Chemical messengers secreted by endocrine glands into the bloodstream that bind to specific receptors on target cells to regulate physiological processes and maintain homeostasis.
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Where are hormones produced?
Hormones are produced in endocrine glands (glands which release their products directly into the blood)
*Endocrine glands release their products through ducts.
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How do hormones travel through the body.
Hormones travel through the circulatory and or lymph systems until they reach the target cell.
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Negative feedback
A change in the body is detected and reversed: the input to a system results in an output that is reversed.
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Positive feedback
A change in the body is detected and amplified: the input to a system result in a change that is amplified.
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Types of adaptions:
Structural - to do with shape, colour or size
Behavioural - to do with the way an organism reacts to its environment
Physiological - internal, cellular processes
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Function of the kidneys
The kidneys are paired organs that filter blood to remove waste products and excess fluid, maintaining homeostasis through several key processes:
- they filter blood to produce urine
- regulate blood pressure
- control pH balance
- produce hormones that help make red blood cells
- maintain proper levels of essential minerals like sodium, potassium, and calcium in the body.
127
What is the primary function of the Pineal Gland?
Modulates sleep and waking patterns by affecting different cells within the brain and body. Produces melatonin.
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Define Diuresis.
The increased production and excretion of urine by the kidneys. Essentially means the kidneys are filtering and producing more urine than usual.
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What does ADH stand for, and what is its other name?
ADH stands for Antidiuretic Hormone, also known as vasopressin.
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Where is ADH produced?
The hypothalamus (a region in the brain).
The pituitary gland then releases it into the blood stream.
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Where is ADH stored and released from?
The posterior pituitary gland.
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What is the main job of ADH?
To prevent the body from losing too much water by acting on the kidneys.
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Explain ADH's role in Water Reabsorption.
ADH signals the kidneys to reabsorb more water back into the bloodstream, instead of letting it be lost in urine. This makes the urine more concentrated and reduces water loss.
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How does ADH regulate blood pressure?
By increasing water reabsorption, ADH increases blood volume, which can raise blood pressure.
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When is ADH released? (List conditions)
When the body needs to conserve water, such as:
When you're dehydrated
When your blood pressure is low
When your blood is too salty (high osmolality)
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What happens if there's too little ADH?
Can cause a condition called diabetes insipidus, where the body loses too much water through dilute urine. Leads to excessive thirst and frequent urination.
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What happens if there's too much ADH?
Can cause SIADH (Syndrome of Inappropriate ADH Secretion), where the body retains too much water, leading to low blood salt levels (hyponatremia).
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ADH: Made by?
Hypothalamus
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ADH: Released by?
Posterior pituitary gland
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ADH: Target organ?
Kidneys
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ADH: Main function?
Water retention (reduces urine output)
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ADH: Triggered by?
Dehydration, high salt levels, low blood pressure
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ADH: Effect?
More concentrated urine, increased blood volume and pressure
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What is the Endocrine System?
A series of glands (a group of cells that release chemicals) that release hormones (messenger substances) that are a part of many homeostatically controlled processes.
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What does "Endocrine" mean in the context of the endocrine system?
"Ductless" - the hormones are released directly from the cell that produces it into the bloodstream, which can potentially carry the hormone to target cells in the body.
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How is the endocrine system mostly controlled?
Mostly under the control of the brain via the hypothalamus (nerve tissue) that stimulates the pituitary gland to release specific hormones.
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Why is the pituitary gland called the "master gland"?
Some of its hormones have specific target organs, but many of the hormones secreted by the pituitary stimulate other endocrine glands.
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How do hormones interact with cells?
Hormones interact with cells that have receptors on their membranes that are specific for that hormone, which explains why hormones can target a few cells or every cell in the body.
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What is Thermoregulation?
All mammals are warm-blooded (homeothermic/homiothermic) and have the ability to adapt themselves according to the change in temperature.
150
Compare the Nervous System and Endocrine/Hormonal System: Type of message.
Nervous System: Electrical (action potential) + some chemical synapse (neurotransmitters)
Endocrine/Hormonal System: Chemical
151
Compare the Nervous System and Endocrine/Hormonal System: How transmitted.
Nervous System: Via neurones
Endocrine/Hormonal System: Via the blood
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Compare the Nervous System and Endocrine/Hormonal System: Speed of message.
Nervous System: Very rapid/instantaneous
Endocrine/Hormonal System: Slow (dependent on blood circulation)
153
Compare the Nervous System and Endocrine/Hormonal System: Duration of message.
Nervous System: Short lived
Endocrine/Hormonal System: Much longer potential duration
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Compare the Nervous System and Endocrine/Hormonal System: Target.
Nervous System: Muscles or glands
Endocrine/Hormonal System: Some specific but potentially every cell in the body
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What is Diuresis?
The loss of water in the urine.
156
How does ADH control the concentration of urine and water reabsorption?
ADH can either increase or decrease the permeability of the membranes of the collecting ducts to water, so that more or less water is reabsorbed back into the blood and tissues (water retention).
157
How is the release of ADH regulated?
By a negative feedback mechanism involving the posterior lobe of the pituitary gland (just below the hypothalamus in the brain).
158
What is Osmoregulation?
The process of maintaining appropriate water and solute levels in the body.
159
Describe the osmoregulation process when water levels are low and solute levels are high (dehydration).
Low water, high solutes in blood detected by osmoreceptor cells in the hypothalamus.
Hypothalamus stimulates the pituitary gland to release ADH.
ADH (via blood) reaches collecting ducts, increasing their permeability to water and urea.
Water is reabsorbed and retained, increasing water levels in blood and tissues.
160
Describe the osmoregulation process during waterlogging (high water, low solute levels).
Hypothalamus is signaled that water level in bodily fluids is too high.
Signal sent to pituitary gland, which stops ADH production/secretion.
Kidney reabsorbs less water, producing more dilute urine.
Body fluids become more isotonic to remove excess water.
161
What is the risk if cells are exposed to dilute blood and interstitial fluid during waterlogging?
They will take up water via osmosis causing them to burst.
162
During waterlogging, how does the lack of ADH affect the collecting ducts?
This lack of stimulation/ADH results in decreased permeability to water of the collecting duct membranes. More water is excreted, less water is reabsorbed/retained causing water levels in the blood and tissues to decrease.
163
What is thermoregulation?
The process by which the body maintains its internal temperature within a narrow, healthy range.
164
How does shivering help in thermoregulation?
Shivering involves muscle contractions that require ATP, produced by cellular respiration, which is exothermic and generates heat.
165
What is vasoconstriction and how does it reduce heat loss?
Vasoconstriction is the narrowing of blood vessels, keeping blood further from the skin surface, reducing heat radiation and heat loss.
166
How does piloerection (hair standing up) reduce heat loss?
It traps a layer of air close to the skin, acting as insulation and reducing heat loss.
167
What kind of feedback is shivering an example of?
Negative feedback, as it increases body temperature in response to cold.
168
What are two effectors used to cool the body during thermoregulation?
Sweat glands (sweating) and muscles around arterioles (vasodilation).
169
How does sweating cool the body?
Evaporative cooling—when sweat evaporates, it removes heat energy from the skin.
170
What is vasodilation and how does it help regulate temperature?
Blood vessels widen, bringing blood closer to the skin surface, allowing heat to radiate into the environment.
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What happens when blood glucose levels increase?
The pancreas detects it and releases insulin, which signals body cells to take up glucose and liver/skeletal muscle cells to store glucose as glycogen.
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What is the role of insulin in glucose regulation?
Insulin facilitates glucose uptake by body cells and storage of glucose as glycogen in the liver and muscles.
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What happens when blood glucose levels decrease?
The pancreas releases glucagon, which signals the liver and muscle cells to break down glycogen into glucose and release it into the bloodstream.
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What is the role of glucagon in glucose regulation?
It stimulates the liver and muscles to convert glycogen into glucose to increase blood sugar levels.
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What is an ectotherm, and how does it differ from an endotherm in thermoregulation?
An ectotherm is an animal that relies on external environmental heat to regulate its body temperature. Unlike endotherms, ectotherms cannot generate enough internal heat to maintain a constant body temperature and depend on behaviours like basking in the sun or seeking shade to manage their body temperature.
176
Describe the stimulus-response pathway for a rise in blood sugar.
Set point → Rise in blood sugar (stimulus) → Islets of Langerhans in the pancreas (receptor) → Insulin release (control centre) → Body cells absorb glucose & liver converts glucose to glycogen (effectors) → Lower blood sugar back to normal (response) → Set point
177
Describe the stimulus-response pathway for a decrease in blood sugar.
Set point → Decrease in blood sugar (stimulus) → Islets of Langerhans in the pancreas (receptor) → Alpha cells release glucagon (control centre) → Liver converts glycogen to glucose & body cells do not absorb glucose (effectors) → Increase blood sugar back to normal (response) → Set point
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What is osmoregulation?
Controlling solute concentrations to avoid water moving out of cells (dehydration) or into cells to the point of bursting.
179
How does solute concentration affect water movement across cell membranes?
High solute concentration in blood: water moves out of cells; low solute concentration: water moves into cells and may cause bursting; equal concentration: no net movement.
180
Describe the stimulus-response pathway for excess water in the blood (hypotonic).
Set point → Rise in water in the blood (hypotonic) → Osmoregulatory centre in hypothalamus (receptor & control centre) → Kidney releases dilute urine (effector) → Solute concentration returns to isotonic (response) → Set point
181
Describe the stimulus-response pathway for low water in the blood (hypertonic).
Set point → Drop in water in the blood (hypertonic) → Osmoregulatory centre in hypothalamus (receptor) → Anterior pituitary releases ADH (control centre) → Kidney reabsorbs more water (effector) → Solute concentration returns to isotonic (response) → Set point
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Why is the threshold important in an action potential?
The threshold voltage (½) of 55mV is required to initiate depolarisation (½), trigger an
action potential (½), initiate opening of the voltage gated sodium channels (½), this
ensures that only large enough stimuli trigger an action potential (½).
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What is the purpose of the neurotransmitter reuptake pump?
Removes neurotransmitter from synaptic gap and
terminates signal.
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Autonomic Nervous System (ANS)
The autonomic nervous system is a division of the peripheral nervous system that controls involuntary body functions, such as heart rate, digestion, breathing, and gland activity. It operates automatically without conscious effort and is divided into the sympathetic and parasympathetic nervous systems.
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Somatic Nervous System (SNS)
The somatic nervous system is a part of the peripheral nervous system that controls voluntary movements of skeletal muscles. It involves motor neurons that transmit signals from the central nervous system to muscles, as well as sensory neurons that carry information from the senses to the brain.
186
Sympathetic Nervous System
The sympathetic nervous system is a branch of the autonomic nervous system that prepares the body for 'fight or flight' responses in stressful or dangerous situations. It increases heart rate, dilates pupils, slows digestion, and releases adrenaline to help the body respond quickly.
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Parasympathetic Nervous System
The parasympathetic nervous system is the other branch of the autonomic nervous system that promotes 'rest and digest' functions. It helps the body calm down after stress, slows the heart rate, stimulates digestion, and conserves energy to maintain homeostasis.
