Response & Regulation (WJEC GCSE Science (Double Award): Biology): Flashcards

False.

Receptor cells are specific, each responding to one particular type of stimulus.

True.

It contains groups of receptor cells sensitive to pressure, temperature and pain.

So it can detect a wide range of changes in its internal and external environment and respond appropriately to each.

A change in the internal or external environment that is detected by receptor cells.

• The brain

• The spinal cord

• All the nerves of the body

The brain and the spinal cord.

CNS.

To all other regions of the body, and importantly to all the sense organs.

The central nervous system consists of the brain and the spinal cord.

The brain, spinal cord and all the nerves of the body form the nervous system.

False.

Only the brain and spinal cord form the CNS. The other nerves connect the CNS to the rest of the body.

True.

The CNS is made up of the brain and the spinal cord.

To receive information from the sense organs and coordinate a response, sending impulses out to the effectors.

The nerves carry electrical impulses between the CNS and the rest of the body, including the sense organs and effectors.

The spinal cord carries impulses between the brain and the body.

If it is damaged, impulses cannot reach the muscles below the injury, so they cannot be made to contract.

• The brain, protected by the skull

• The spinal cord, protected by the vertebrae of the backbone

An involuntary response that does not involve the conscious part of the brain as coordinator.

• Fast

• Automatic

• Some are protective

Limb muscles contract to pull the limb away from a potentially damaging stimulus, such as high heat or a sharp object.

This protects the limb from harm.

Muscles in the eyelid contract to close the eye against a harmful stimulus such as an allergen or bright light, protecting the eye from damage.

The pupil becoming smaller protects the back of the eye from damage in bright light.

The pupil becoming larger lets more light in when conditions are dark.

After the response has already been carried out. Reflexes do not involve the conscious brain.

A reflex action is an involuntary response that does not involve the conscious part of the brain.

False.

Blinking is a reflex action. It is automatic and happens before you are consciously aware of it.

The pathway taken by electrical impulses as they travel along neurones during a reflex response.

• Stimulus

• Receptor

• Coordinator

• Effector

• Receptor

• Sensory neurone

• Relay neurone in the spinal cord

• Motor neurone

• Effector

• Synapses

A receptor in the skin detects the stimulus.

A sensory neurone carries impulses to the coordinator in the spinal cord.

A relay neurone passes the impulse to a motor neurone across a synapse.

The motor neurone carries the impulse to a leg muscle, the effector, which contracts to pull the foot away.

A muscle or a gland that brings about the response.

Always from the stimulus and receptor, towards the spinal cord, and then out to the effector.

In a reflex arc, the sensory neurone carries the impulse from the receptor to the spinal cord.

False.

For reflexes involving the eyes, such as blinking or the pupil reflex, the coordinator is in the brain, though never in its conscious part.

The time taken to respond to a stimulus. Reactions are usually very quick, typically less than a second.

• Age

• Stress

• Use of drugs, such as caffeine

The volunteer rests their forearm on a table with their hand over the edge, thumb and fingers either side of a vertical ruler at the 0 cm mark.

The ruler is dropped without warning and the volunteer catches it as quickly as they can.

The number just above the thumb is recorded, and the test is repeated five times.

A faster reaction time. The further down the ruler is caught, the quicker the response.

• Independent variable: the person catching the ruler

• Dependent variable: the reaction time, measured by the catch distance

• Using the dominant hand each time

• Dropping the same ruler from the same height and angle

• Keeping the ruler in the same orientation, with 0 cm facing down

To calculate a mean distance, which gives a more reliable measure of reaction time and allows anomalies to be spotted.

• Difficulty seeing exactly where the fingers caught the ruler

• The ruler not being held in exactly the same position above the fingers each time

Use a computer to record reaction times, which removes human error, and record in milliseconds, which is more precise than seconds.

Converting the ruler drop distance in centimetres into a reaction time, using a conversion table.

The volunteer should hold the ruler at the 0 cm mark before it is dropped.

Recording reaction times in milliseconds rather than seconds gives greater precision.

True.

A warning would let the volunteer anticipate the drop, so the measurement would not reflect their true reaction time.

False.

A higher catch point means the ruler fell further before being caught, so the reaction time was slower.

The regulation of conditions inside an organism to keep them relatively constant and protected from harmful effects.

• Water content

• Temperature

• pH

• Blood pressure

• Blood glucose concentration

To keep the organism healthy and maintain optimum conditions for it to function.

If the limits are exceeded, the organism may die.

Enzymes only work within a narrow range of temperature and pH.

Homeostasis maintains those optimum conditions, so reactions in body cells can continue.

They would denature. Their active sites would lose shape, so the reactions of metabolism would stop.

Homeostasis is the regulation of internal conditions to keep them relatively constant.

Homeostasis maintains optimal conditions for enzyme action and all cell functions.

False.

It keeps them relatively constant, fluctuating within set limits rather than staying at a fixed value.

True.

It is one of several internal conditions kept within set limits, alongside temperature, pH, water content and blood pressure.

So its internal conditions stay within the narrow range its cells need, regardless of what is happening outside the body.

Homeostasis maintains the conditions cells need for enzymes to work.

If cell reactions can continue, the cells stay alive, and so the organism as a whole can live.

• Temperature

• pH

A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more target organs.

In glands.

In the blood.

The organ whose activity is altered by a particular hormone.

The collective name for all the glands that produce hormones in an animal.

They transmit information from one part of the organism to another and bring about a change in the target organ.

Hormones are carried around the body in the blood.

The glands that produce hormones are known collectively as the endocrine system.

False.

Hormones are carried in the blood. Electrical impulses travel along neurones.

True.

Although a hormone travels all round the body in the blood, it only alters the activity of its target organs.

Insulin, produced by the pancreas, which lowers blood glucose concentration.

Hormones must be carried in the blood to reach their target organ, which takes longer than an electrical impulse travelling along a neurone.

The pancreas.

Cells in the pancreas detect the rise.

The pancreas secretes the hormone insulin into the blood.

Insulin causes the liver and muscles to take up glucose and store it as glycogen.

Blood glucose falls back to normal and insulin secretion stops.

A protein hormone released by the pancreas that lowers blood glucose by causing the liver to convert glucose into glycogen.

The insoluble storage form of glucose, stored in the liver and muscles.

The liver, and also the muscles.

Cells of the body can lose water by osmosis, because the blood becomes too concentrated.

The brain receives insufficient glucose for respiration, which can lead to a coma or even death.

It is insoluble, so it can be stored without affecting the water balance of cells by osmosis.

The pancreas releases the hormone insulin when blood glucose levels rise.

Insulin causes the liver to convert glucose into insoluble glycogen for storage.

True.

Insulin is a protein hormone secreted into the blood by the pancreas.

False.

The pancreas stops secreting insulin once blood glucose has returned to normal levels.

Blood glucose concentration must be kept within a narrow range, so the body constantly regulates it to keep internal conditions relatively constant.

It rises sharply as the carbohydrate is digested to glucose and absorbed.

The pancreas then releases insulin to bring it back down.

A common disease in which a person has a high blood glucose level.

The pancreas fails to produce sufficient insulin.

Scientists think this results from the person's immune system destroying the insulin-producing cells of the pancreas.

The body cells no longer respond properly to insulin.

The person still produces insulin, but their cells are resistant to it.

• Insulin injections, several times a day

• A controlled diet, limiting simple carbohydrates that raise blood sugar quickly

• In rare cases, a pancreas transplant

• A carbohydrate-controlled diet

• A regular exercise regime

Obesity, often linked to a diet high in carbohydrates and a lack of exercise.

By testing for the presence of glucose in the urine, using Benedict's solution.

Add equal volumes of the urine sample and Benedict's solution to a test tube.

Gently heat the solution for five minutes.

If glucose is present, the solution turns from blue to orange.

In type 1 diabetes the pancreas fails to produce sufficient insulin.

Benedict's solution is used to test a urine sample for the presence of glucose.

False.

They still produce insulin, but their body cells have become resistant to it.

True.

Because the pancreas cannot make enough insulin, it must be injected, normally several times a day.

Blood glucose is so high that the excess is excreted in the urine rather than being stored in the liver as glycogen.

Simple carbohydrates are converted quickly into glucose, causing blood sugar to rise rapidly, which is harder to control.

• Hair

• Erector muscle

• Sweat gland

• Sweat duct

• Sweat pore

• Blood vessels

About 37 °C.

This is the temperature at which enzymes work best. Above it they begin to denature.

The widening of blood vessels near the skin surface, which increases blood flow to the capillaries so more heat is lost by radiation.

The narrowing of blood vessels leading to the skin capillaries, which reduces blood flow near the surface so less heat is lost by radiation.

Sweat is secreted onto the skin by sweat glands.

It evaporates, which uses heat energy from the body to turn liquid water into water vapour, cooling the skin.

The erector muscles contract, making the hairs stand on end.

This traps a layer of air over the skin, which insulates the body and reduces heat loss by radiation.

It is a reflex action in which muscles contract rapidly and regularly.

The respiration needed to power this releases enough heat to warm the blood and raise core body temperature.

• Vasodilation of blood vessels near the surface

• Sweating

• Hairs lie flat

• Vasoconstriction of blood vessels near the surface

• Erection of hairs to trap an insulating layer of air

• Shivering to generate heat

When we are hot, blood vessels near the skin surface widen. This is called vasodilation.

Sweat cools the skin by evaporation, which uses heat energy from the body.

False.

The blood vessels do not move. They widen (vasodilate), so more blood flows through the capillaries near the surface.

True.

It happens automatically in response to a fall in core body temperature.

It contains many receptors across the whole body surface that detect touch, pressure, pain, heat and cold.

Enzymes work best at about 37 °C. If the body gets too hot they denature and can no longer catalyse reactions such as respiration.

A control mechanism that returns conditions to a set point when they change from the ideal.

• If a level rises, control systems switch on to reduce it

• If a level falls, control systems switch on to raise it

• Core body temperature

• Blood glucose concentration

• Insulin, which lowers blood glucose

• Glucagon, which raises blood glucose

Cells in the pancreas detect the fall.

The pancreas produces glucagon.

Glucagon causes glycogen in the liver to be converted into glucose and released into the blood.

Blood glucose rises back to normal and glucagon secretion stops.

The pancreas, which makes the hormones, and the liver, which stores and releases glycogen.

The hormonal system and the nervous system.

• INsulin takes glucose IN to the liver

• GlucaGON is needed when glucose is GONe

Glucagon causes glycogen in the liver to be converted back into glucose.

Negative feedback returns conditions to the ideal value, known as the set point.

False.

It is a continuous cycle of raising and lowering, keeping the condition within a narrow range around the set point.

True.

Insulin lowers blood glucose by storing it as glycogen, while glucagon raises it by converting glycogen back to glucose.

If core temperature rises above the set point, vasodilation and sweating cool the body.

If it falls, vasoconstriction, hair erection and shivering warm it.

Either way, the response returns temperature to the set point.

A conscious decision an individual makes that may increase or decrease their risk of disease.

• Consumption of alcohol

• Smoking cigarettes

• Diet

• Amount of exercise

Reaction time is generally lowered, because alcohol affects the nervous system.

Any three of:

• Slurred speech

• Loss of balance

• Loss of inhibitions and aggressive behaviour

• Blurred vision

• Liver disease, such as cirrhosis

• Cancers, such as mouth cancer

• Circulatory and heart disease, as alcohol raises blood pressure

The liver is the main site of drug metabolism.

Breaking down alcohol produces toxic waste products that damage liver cells, leading to conditions such as cirrhosis.

Toxic products from its breakdown can damage DNA, causing cancerous cell mutations.

Symptoms experienced when an addicted person stops taking a substance.

For alcohol these include headaches, depression and body tremors.

A poor diet and a lack of exercise increase the chance of developing it.

Obesity is a major risk factor.

The liver is the primary site of drug metabolism in the body.

Obesity is a major risk factor for developing type 2 diabetes.

False.

All drugs, legal medicinal ones included, can be harmful if misused or overused.

True.

Alcohol is a poison that changes various chemical processes in the body.

• Drugs taken to boost sporting performance

• Illegal recreational drugs such as ecstasy, cocaine and heroin