Practice Test

The response to an increase in the level of ADH in the blood of a healthy human being would include:

J. Increased urine output
K. Decreased production of insulin
L. Decreased blood pressure
M. Increased water reabsorption

M

Which one of the following combinations correctly compares a feature of the nervous system with a feature of the endocrine system?

Nervous - Endocrine

J. Produces longer-lived messages vs Produces shorter-lived messages

K. Produces a slower response to a stimulus vs Produces a faster response to a stimulus
L. Transmits electrochemical messages vs transmits chemical messages

M. Uses chemicals to detect a stimulus vs uses hormones to detect a stimulus

L

‘Positive phototropism’ describes the growth of plants towards a light source. Phototropins detect light and trigger the release of auxin, a plant hormone. Auxin is selectively transported to the shade side of the plant, where it stimulates elongation of cells. The increase in the length of the cells on one side of the plant causes it to bend towards the light source.

In this example of a stimulus-response model,

J. Auxin is the receptor
K. The plant cells are the effectors
L. The release of auxin is the final response
M. Phototropins are the stimulus

K

Oxycodone is a powerful prescription drug that is used to treat serious pain in patients. One of its effects is to inhibit the release of neurotransmitters such as acetylcholine.

Which one of the following is least likely to be affected by this drug?

J. The transmission of a nerve impulse along the axon
K. The number of nerve impulses crossing the synpase
L. The level of pain suffered by a patient
M. The number of membrane receptors in a synapse that have acetylcholine bound to them

J

A person suffering from a severe deficiency of thiamine may develop nerve damage in a condition known as ‘dry beriberi’. Two of the many unpleasant symptoms of dry beriberi are a lack of feeling in the feet and loss of muscle function in the lower legs.

Damage to which one of the following could lead to at least one of these symptoms?

J. Receptors in the peripheral nervous system
K. Motor neurons in the central nervous system
L. Interneurons in the peripheral nervous system
M. Sensory neurons in the central nervous system

J,

Fentanyl belongs to a class of medical drugs known as opioids. It binds to opioid receptors in the membranes of nerve cells, and this results in the release of fewer neurotransmitters. Fentanyl can be prescribed by doctors for the temporary relief of sever pain.

The relief of pain symptoms by fentanyl occurs because

J. Pain messages are unable to be transmitted through motor neurons
K. It reduces the fusion of vesicles with cell membranes
L. It has a shape that is complementary to neurotransmitters
M. It lowers the stimulation of sensory neurons

K.

The ‘glabellar tap sign’ is a reflex response of involuntary blinking that results from repeated tapping on the forehead. It is thought that this response has evolved to help protect the eyes from harm.

Which one of the following statements is consistent with this information?

J. The nerve signal passes from a motor neuron to an interneuron, but not through the brain
K. The response is controlled by the endocrine system
L. The response is a reflex response because it only passes through the peripheral nervous system
M. The nerve signal passes from a sensory neuron to an interneuron

M

Which one of the following combinations correctly identifies the stimulus, the receptor, and the response involved in the control of blood sugar levels?

L

The nervous and endocrine systems both help regulate body temperature.
Compare two characteristics of the nervous and endocrine systems in regulating body temperature.

Any two:

Speed/duration

• Nervous regulation is rapid and short-lived because electrical impulses travel quickly along neurons

• Endocrine regulation is slower but longer-lasting because hormones travel through the bloodstream

Route of transmission

• Nervous signals travel along neurons and across synapses

• Endocrine signals travel through the circulatory system

Signal type

• The nervous system uses electrical impulses and neurotransmitters

• The endocrine system uses chemical hormones

Specificity

• Nervous regulation targets specific effectors such as sweat glands or blood vessels

• Endocrine regulation affects any cell that possesses the appropriate hormone receptor

Role in thermoregulation

• The nervous system rapidly adjusts sweating and blood vessel diameter

• The endocrine system contributes to long-term regulation by altering metabolic rate (e.g., thyroid hormones)

Describe negative feedback and explain its role in regulating body temperature (increase)

Negative feedback is a homeostatic mechanism in which a change in a variable triggers responses that oppose the change, returning the variable towards its set point

When body temperature rises above normal, thermoreceptors detect the increase and send signals to the hypothalamus. The hypothalamus stimulates sweating and vasodilation, increasing heat loss

As body temperature falls back to the normal set point, these responses decrease, preventing excessive cooling and maintaining a stable internal temperature

A person develops severe dehydration after prolonged exercise on a hot day.

Sweating has caused a significant loss of body water.
The pituitary gland responds by increasing secretion of ADH

a) state and explain the effect of increased ADH secretion on urine production

Urine volume decreases and becomes more concentrated

ADH increases water reabsorption in the collecting ducts of the kidneys, allowing more water to return to the bloodstream and reducing water loss

A person develops severe dehydration after prolonged exercise on a hot day.

Sweating has caused a significant loss of body water.
The pituitary gland responds by increasing secretion of ADH

b) Explain why thirst increases during dehydration

Osmoreceptors in the hypothalamus detect the increased concentration of the blood caused by water loss

The hypothalamus stimulates the thirst centre, encouraging the person to drink water and restore normal blood water concentration

Caffein is one of the most widely consumed simulants in the world. It affects both the nervous and endocrine systems by increasing alertness, raising heart rate and influencing kidney function.

Caffeine stimulates the release of adrenaline (epinephrine) from the adrenal glands

a) Describe how this action results in an increase in body temperature.

Caffeine stimulates the adrenal glands to release adrenaline into the bloodstream. Adrenaline increases the rate of cellular respiration and metabolic activity in body cells. This increased metabolic rate produces more heat, causing body temperature to rise.

Caffein is one of the most widely consumed simulants in the world. It affects both the nervous and endocrine systems by increasing alertness, raising heart rate and influencing kidney function.

b) Caffeine also causes blood vessels in the skin to constrict.
Explain how this action helpts reduce heat loss from the body

Caffein causes vasoconstriction of skin blood vessels, reducing blood flow near the skin surface.

Less heat is transferred to the environment, helping maintain body temperature

Caffeine acts as a milk diuretic by reducing water reabsorption in the kidneys

a) State and explain the effect of caffeine consumption on urine production

Urine volume increases
Less water is reabsorbed from the distal tubules and collecting ducts of the nephrons

More water remains in the filtrate, producing a larger volume of dilute urine

Caffeine acts as a milk diuretic by reducing water reabsorption in the kidneys

b) Explain how caffeine consumption can affect blood pressure

Blood pressure may decrease slightly if excess water is lost through increased urine production

Reduced blood volume decreases the pressure exerted on blood vessel walls

The body regulates blood glucose concentration through the coordinated action of the endocrine system

Explain in detail how the body responds to an increase in blood glucose concentration after eating a meal

• Blood glucose concentration rises after carbohydrates are digested and absorbed

• Beta cells in the pancreas detect the increase in blood glucose

• Insulin binds to complementary receptors on liver, muscle, and body cells

• Cells increase glucose uptake from the blood

• The liver and muscles convert excess glucose into glycogen

• Blood glucose concentration decreases back towards the normal set point through negative feedback

Caffeine stimulates the nervous system and may affect heart rate

An investigation was conducted to determine the effect of caffeine on resting heart rate

Five participants had their resting heart rate measured before drinking a cup of coffee containing 150 mg of caffeine. Thirty minutes later, their resting heart rate was measured again.

Identify the factor that cannot be held constant in this investigation and explain the effect that this could have on the data

Individual caffeine tolerance

• Some participants regularly consume caffeine while others do not.

• Habitual caffeine users may show a smaller increase in heart rate, increasing variation between participants

Body mass

• Participants of different body masses receive different effective doses per kilogram.

• This may produce different heart rate responses and increase variability

Stress or anxiety

• Some participants may be anxious during testing

• Stress independently increases heart rate, reducing the validity of the investigation

Sleep quality

• Participants who are tired may respond differently to caffeine

• Differences in alertness can influence the physiological response and increase variability

Caffeine stimulates the nervous system and may affect heart rate

An investigation was conducted to determine the effect of caffeine on resting heart rate

Five participants had their resting heart rate measured before drinking a cup of coffee containing 150 mg of caffeine. Thirty minutes later, their resting heart rate was measured again.

State one ethical consideration relevant to this investigation

• Obtain informed consent

• Participants should be screened for heart conditions

• Participants should be free to withdraw

• Keep participant data confidential

• Minimise risks associated with caffeine consumption

• Avoid excessive caffeine doses

• Ensure participants understand possible side effects

In 2024, an endurance athlete was suspended after testing positive for excessive levels of synthetic thyroxine (T4), a hormone that increases metabolic rate. Some athletes misuse thyroxine in an attempt to reduce body mass and improve endurance

Explain why injecting thyroxine can improve an athlete’s performance during endurance events

Injecting thyroxine increases the body’s metabolic rate by stimulating cellular respiration

This increases ATP production and energy availability, allowing muscles to sustain activity for longer and potentially improving endurance performance

Athletes who misuse thyroxine risk developing hyperthyroidism, a condition characterised by an abnormally high metabolic rate

State on consequence of hyperthyroidism for an athlete

Increased heart rate

Excessive sweating

Heat intolerance

Weight loss

Anxiety of nervousness

Tremors

Fatigue

Difficulty sleeping

Increased breathing rate

Describe the response of the endocrine system when blood thyroxine levels rise above the normal tolerance limits

High thyroxine levels are detected by the hypothalamus and anterior pituitary gland.

The hypothalamus decreases secretion of TRH, causing the pituitary to release less TSH. Reduced TSH decreases thyroxine secretion by the thyroid gland until hormone levels return to the normal range through negative feedback

High body temperatures stimulates thermoreceptors that initiate a reflex response.
The reflex pathway uses sensory neurons to transmit signals to the hypothalamus and motor neurons that transmit signals to sweat glands

Identify two structural differences between sensory and motor neurons

The sensory neuron cell body is located along the axon, whereas the motor neuron cell body is located at one end

Sensory neurons generally have one long dendron and one short axon, whereas motor neurons have many dendrites and one long axon

Motor neurons possess numerous dendrites for receiving signals from other neurons, whereas sensory neurons have few or no dendrites on the cell body

Sensory neurons carry impulses toward the CNS, while motor neurons carry impulses away from the CNS to effectors

Acetylcholine is the neurotransmitter released at the synapse between motor neurons and sweat gland cells.

Describe the roll of acetylcholine at this synapse

Acetylcholine is released from the motor neuron into the synaptic cleft. It binds to complementary receptors on the sweat gland cell membrane, opening ion channels and initiating a response that stimulates sweat production

The response is increased sweating. Describe one other response of the body that helps reduce body temperature

Vasodilation

Blood vessels suppling the skin widen, increasing blood flow near the skin surface

This allows more heat to be lost to the environment by radiation and convection

Reduced metabolic heat production

The hypothalamus decreases TSH secretion, reducing thyroxine production

Lower metabolic activity decreases heat production

Reduced muscle activity

The body supresses shivering

Less ATP is used by skeletal muscles, reducing heat production

The use of thyroxine without a medical need is prohibited in many sporting competitions

Explain, with reference to the imbalance of hormones regulating metabolic rate, why individuals with hypothyroidism require thyroxine replacement therapy

Individuals with hypothyroidism produce insufficient thyroxine despite normal or increased TSH secretion

Thyroxine replacement restores normal metabolic rate, cellular respiration and heat production, returning metabolism towards the normal range

Synthetic thyroxine differs slightly from naturally produced hormones and can be detected using analytical chemistry techniques such as chromatography and mass spectrometry

Explain how this example demonstrates ONE key concept of SHE

Influence

Scientific advances in hormone detection influences sporting policies by allowing governing bodies to identify unfair performance enhancement

Ethical concerns about fairness and athlete welfare also influence anti-doping regulations

Application and Limitation

Knowledge of hormone chemistry is applied to detect synthetic thyroxine and protect fair competition

However, natural variation in hormone concentrations and metabolism may make interpretation difficult and occasionally limit certainty when analysing results

The brain becomes aware of painful stimulus shortly after the hand has been withdrawn. Explain why the hand is withdrawn before the person consciously feels pain

The withdrawal reflex is coordinated within the spinal cord rather than the brain.

Motor neurons are activated immediately after processing by the relay neuron, allowing the muscles to contract rapidly

Signals are sent to the brain at the same time, but conscious awareness occurs after the reflex response has already taken place.

What is a cause of less ADH?

Increased consumption of alcohol. Alcohol inhibits ADH release from the pituitary gland. Resulting in excessive urination, which leads to dehydration, which causes hangovers