Biology Topic 1

How does the body maintain homeostasis?

By adjusting its internal environment to keep conditions stable and optimal for survival, such as temperature, pH, hydration, and blood glucose levels.

What is the role of the control centre in the homeostatic stimulus-response model?

It acts as a command hub that receives information, makes decisions, and sends out instructions to correct deviations from normal conditions.

What are the components of a feedback system?

Stimulus -> Receptor -> Control Centre -> Effector -> Response -> Feedback to Stimulus.

What is the difference between a receptor and an effector?

Receptors detect changes in the environment, while effectors respond to signals from the control centre to restore balance.

How does negative feedback function in maintaining homeostasis?

Negative feedback detects a change and initiates responses to maintain stability and homeostasis.

How does positive feedback differ from negative feedback?

Positive feedback intensifies a change until a specific outcome occurs, while negative feedback works to counteract changes.

What type of feedback loop is involved in blood clotting when thrombin is produced?

Positive feedback, as the presence of thrombin promotes the activation of more thrombin.

What type of feedback loop is involved in the complement cascade during an immune response?

Positive feedback, as the activation of one complement protein leads to the activation of many more.

What type of feedback loop is involved in the body's response to alkalosis?

Negative feedback, as the body slows breathing to retain carbon dioxide, which lowers pH back to normal.

In the ruler drop test, what is the stimulus?

The visual cue of the ruler being dropped.

In the ruler drop test, what is the response?

The student's physical action of catching the ruler.

How is the average reaction time calculated in the ruler drop test?

By calculating the mean of the reaction times recorded for each trial.

What was the average reaction time for Trial 1 in the ruler drop test?

222.8 milliseconds.

What was the average reaction time for Trial 2 in the ruler drop test?

209.7 milliseconds.

What was the average reaction time for Trial 3 in the ruler drop test?

200.7 milliseconds.

What was the average reaction time for Trial 4 in the ruler drop test?

193.4 milliseconds.

What was the average reaction time for Trial 5 in the ruler drop test?

188.6 milliseconds.

What is the function of effectors in the homeostatic process?

Effectors respond to commands from the control centre to restore balance.

What is the significance of feedback in maintaining homeostasis?

Feedback mechanisms help the body adjust and maintain stable internal conditions despite external changes.

What happens during a negative feedback loop when a parameter deviates from its set point?

The control centre activates effectors to counteract the deviation and restore the parameter to its set point.

What is an example of a physiological parameter regulated by negative feedback?

Blood glucose levels.

What is the overall goal of homeostasis in the body?

To maintain stable internal conditions necessary for survival.

Why might Student 10's reaction time of 400 ms be considered an outlier?

It is significantly higher than the other recorded reaction times for the same drop distance of 20 cm, suggesting an abnormal response.

What is a possible reason for the outlier reaction time recorded by Student 10?

Factors such as distraction, fatigue, or a lack of focus during the trial could have contributed to the slower reaction time.

What conclusion can be drawn about average reaction time in response to practice?

As practice increases, reaction times generally decrease, indicating improved reflexes and response efficiency.

What was the average reaction time for Subject 1 without noise?

188 ms.

What was the average reaction time for Subject 2 with noise?

273 ms.

Which condition produced the best reaction time according to the data?

Subject 1 with noise had the best reaction time at 187 ms.

How much slower was Subject 2's reaction time compared to Subject 1's with noise?

Subject 2 was 86 ms slower than Subject 1.

What do chemoreceptors detect?

Chemoreceptors detect chemical stimuli.

What do mechanoreceptors detect?

Mechanoreceptors detect mechanical pressure or distortion.

What type of sensory receptor detects sound?

Hair cells in the inner ear detect sound by responding to vibrations caused by sound waves.

What is the stimulus for nociceptors?

Potentially damaging stimuli, such as touching a hot stove.

How do living organisms detect changes in their environment?

They use sensory receptors to monitor stimuli, which are transmitted to the brain for interpretation and response.

What is the function of dendrites in nerve cells?

Dendrites receive signals from other neurons and transmit them to the soma.

What role does the axon play in nerve cells?

The axon transmits electrical impulses away from the soma to other neurons or muscles.

What is the function of the myelin sheath?

The myelin sheath insulates the axon, increasing the speed of electrical impulses.

What are nodes of Ranvier?

Nodes of Ranvier are gaps in the myelin sheath that facilitate rapid signal transmission along the axon.

What is the role of the axon terminal?

The axon terminal releases neurotransmitters into the synapse to communicate with other neurons.

What distinguishes sensory neurons from motor neurons?

Sensory neurons transmit signals from sensory receptors to the central nervous system, while motor neurons carry signals from the central nervous system to muscles or glands.

What is the function of interneurons?

Interneurons connect sensory and motor neurons within the central nervous system and process information.

What effect does background noise have on human reaction times?

Background noise increases reaction times, making it harder to focus and respond quickly.

What evidence supports the conclusion about the impact of noise on reaction times?

Both subjects reacted slower with noise, indicating that noise negatively affects reaction times.

What is the average reaction time for Subject 1 with noise?

187 ms.

What are the main components of a nerve cell and their functions?

Nerve cells consist of dendrites (receive signals), soma (cell body), axon (transmits signals), myelin sheath (insulates axon), nodes of Ranvier (gaps in myelin for faster transmission), axon terminal (releases neurotransmitters), and synapse (junction between neurons).

What is the role of neurotransmitters in synaptic transmission?

Neurotransmitters are released from presynaptic neurons into the synaptic cleft, bind to receptors on postsynaptic neurons, and facilitate signal transduction.

What triggers an action potential in a neuron?

An action potential is triggered when a neuron's membrane potential reaches a threshold level, causing a rapid change in voltage.

What is the resting potential of a neuron?

The resting potential is the membrane potential when the neuron is not transmitting signals, typically around -70mV.

What is the significance of the threshold potential in action potentials?

The threshold potential is the minimum membrane potential that must be reached to initiate an action potential.

How does the membrane potential change during an action potential?

During an action potential, the membrane potential rapidly depolarizes, reaches a peak, and then repolarizes back to resting potential.

What is the difference between electrical and chemical signals in neurons?

Electrical signals (action potentials) travel within neurons, while chemical signals (neurotransmitters) transmit between neurons across synapses.

How do hormones relay messages to cells?

Hormones are chemical messengers released into the bloodstream or lymphatic system, targeting cells with specific receptors.

What are the differences between hormonal control and nervous control?

Nervous control uses electrical impulses for fast, short-lived, targeted responses, while hormonal control uses chemical messengers for slower, long-lasting, widespread effects.

What determines a cell's sensitivity to a specific hormone?

A cell's sensitivity to a hormone is directly related to the number of specific receptors it displays for that hormone.

What is the role of the synaptic cleft in neurotransmission?

The synaptic cleft is the space between presynaptic and postsynaptic neurons where neurotransmitters are released and bind to receptors.

What happens to the membrane potential after an action potential?

After an action potential, the membrane potential returns to resting potential, allowing for another action potential to occur.

What is the function of the nodes of Ranvier?

Nodes of Ranvier facilitate faster signal transmission along the axon by allowing action potentials to jump between nodes.

What is the difference between presynaptic and postsynaptic neurons?

Presynaptic neurons release neurotransmitters, while postsynaptic neurons receive these signals through their receptors.

How does the number of receptors affect cellular response to hormones?

The more receptors a cell has for a specific hormone, the more sensitive it is to that hormone's effects.

What is the role of vesicles in synaptic transmission?

Vesicles store neurotransmitters in presynaptic neurons and release them into the synaptic cleft during neurotransmission.

How does a sensory neuron transmit signals?

A sensory neuron transmits signals from sensory receptors to the spinal cord through its unipolar structure.

What is the significance of the peak of action potential?

The peak of action potential represents the maximum depolarization of the neuron's membrane potential.

Why is the resting potential negative?

The resting potential is negative because there are more negative ions and fewer Na+ ions inside the neuron compared to the outside.

What is the relationship between action potentials and signal transduction?

Action potentials initiate signal transduction processes that result in the transmission of signals across synapses.

What type of cell is most likely to respond to a hormone, and why?

The cell most likely to respond to a hormone is the one with a matching receptor, as hormones affect only target cells with specific receptors.

What is the significance of up- and down-regulation of cell receptors in organisms?

Cells adjust sensitivity to hormones by changing receptor numbers, crucial for maintaining balance and responding to changing conditions.

What is up-regulation in the context of cell receptors?

Up-regulation is the increase in receptor numbers to boost sensitivity to a hormone.

What is down-regulation in the context of cell receptors?

Down-regulation is the decrease in receptor numbers to reduce sensitivity to a hormone.

In a feedback-control diagram, what does rectangle 2 represent?

Rectangle 2 represents the receptor, which detects the stimulus.

In a feedback-control diagram, what does rectangle 4 represent?

Rectangle 4 represents the effector, which carries out the response.

What is the modulator or control center for human body temperature regulation?

The hypothalamus in the brain acts as the control center.

What are two responses that lower body temperature when it increases?

Sweating and vasodilation.

How does sweating help in thermoregulation?

Sweating releases fluid onto the skin, and the evaporation of sweat absorbs heat, cooling the body.

What is vasodilation?

Vasodilation is when blood vessels near the skin widen, allowing more blood flow to the surface to dissipate heat.

What is the stimulus-response model for pulling back an arm after being punctured by a thorn?

Stimulus (thorn punctures skin) -> Receptor (pain receptors detect injury) -> Control Centre (spinal cord processes signal) -> Effector (arm muscles) -> Response (arm pulls back quickly).

Is the reflex action of pulling back an arm an open or closed loop?

It is an open loop because there is no feedback to adjust or reverse the response.

Is the reflex action of pulling back an arm an example of homeostatic regulation?

No, it is not homeostatic regulation; it is a reflex action that does not maintain internal balance.

What are some structural features of endotherms that help reduce heat loss?

Brown adipose tissue and insulation.

What are some behavioral responses of endotherms for thermoregulation?

Kleptothermy, hibernation, aestivation, and torpor.

What are some physiological mechanisms of thermoregulation in endotherms?

Evaporative heat loss, thermogenesis, and vasomotor control.

What is an example of increasing heat loss from the body?

Sweating, which cools the body as sweat evaporates.

What is kleptothermy?

Kleptothermy is a mode of heat transfer where one animal gains warmth from another.

How do male red-sided garter snakes use kleptothermy?

They mimic female pheromones to attract other males, transferring heat through physical contact.

What is the role of brown adipose tissue in thermoregulation?

Brown adipose tissue helps generate heat through thermogenesis.

How do endotherms living in cold environments reduce heat loss?

They have structural features that minimize heat loss.

How does thick fur help mammals in cold environments?

Thick fur reduces heat loss by minimizing thermal exchange with the cold environment.

What structural feature contrasts between mammals adapted to hot and cold environments?

Extremity size; mammals in hot climates have long ears or limbs for heat dissipation, while cold climate mammals have shorter extremities to conserve heat.

Why do reptiles like geckoes become inactive at night while mammals remain active?

Reptiles are ectotherms relying on external heat sources, becoming inactive in cooler temperatures, whereas mammals are endotherms that generate internal heat, allowing them to remain active.

What is the difference between torpor and aestivation?

Torpor is a short-term response triggered by cold or food scarcity to conserve energy, while aestivation is a long-term response triggered by heat and drought to survive extreme conditions.

How does shivering contribute to thermoregulation?

Shivering is an involuntary muscle contraction triggered by the hypothalamus that generates heat through ATP hydrolysis, helping to raise core temperature and maintain thermal homeostasis.

What role does sweating play in thermoregulation?

Sweating involves the release of water from sweat glands onto the skin surface, which cools the body through evaporation while also resulting in water loss.

At what time does the water level in the blood peak according to the graph?

The water level in the blood peaks around 9am.

When is the water level in the blood at its lowest according to the graph?

The water level in the blood is at its lowest around 3pm.

What mechanism maintains osmoregulation when water levels drop?

Hormonal regulation via ADH; the hypothalamus detects increased blood osmolarity and signals the pituitary gland to release ADH, prompting kidneys to reabsorb more water.

Why do water levels in the blood fluctuate throughout the day?

Water levels fluctuate due to daily activities, environmental factors, physical exertion leading to increased sweating, and temperature changes affecting evaporation rates.

What is the role of stomata in maintaining water balance in plants?

Stomata regulate gas exchange and water loss; they open to allow CO2 in for photosynthesis and close to minimize water loss during dry conditions.

How do vacuoles contribute to water balance in plant cells?

Vacuoles store water and help maintain turgor pressure, which supports cell structure and prevents wilting.

What is the function of the cuticle in plants adapted to dry environments?

The cuticle is a waxy layer that reduces water loss by preventing evaporation from the leaf surface.

What role does abscisic acid play in plant water regulation?

Abscisic acid signals stomata to close during water stress, reducing water loss and helping the plant conserve moisture.

Which diagram represents a plant not adapted to dry environments?

Diagram B is not from a plant adapted to dry environments.