Homeostasis and Response Flashcards
What are the two main components of the human nervous system?
Central nervous system (CNS) and peripheral nervous system (PNS)
CNS includes the brain and spinal cord, while PNS consists of all the nerves in the body.
How does information travel through the nervous system?
As electrical impulses along nerve cells known as neurones
A bundle of neurones is referred to as a nerve.
What are the cytoplasmic extensions of a neurone called?
Axons and dendrites
What is the function of the myelin sheath on axons?
Insulates the axon and allows electrical impulses to jump along nodes
This increases the speed of impulse transmission.
What is the pathway through the nervous system for a response?
stimulus → receptor → coordinator → effector → response
What is a reflex arc?
An involuntary response that does not involve the conscious part of the brain
List the three types of neurones involved in a reflex arc.
- Sensory neurones
- Relay neurones
- Motor neurones
What is the role of sensory neurones?
Carry impulses from sense organs to the CNS
What are neurotransmitters?
Chemicals released into the synaptic cleft that transmit signals between neurones
True or False: Electrical impulses can cross synapses.
False
What happens when neurotransmitters bind to receptor molecules on the postsynaptic neurone?
Stimulates the second neurone to generate an electrical impulse
Fill in the blank: The _______ is the time taken to respond to a stimulus.
reaction time
What factors can affect human reaction time?
- Age
- Stress
- Use of drugs (e.g., caffeine)
What is the role of the cerebral cortex?
Responsible for higher-order processes such as intelligence, memory, consciousness, and personality
What does the cerebellum control?
Balance, muscle coordination, and movement
What does the medulla control?
Unconscious activities such as heart rate and breathing
What is the purpose of MRI scanners in studying the brain?
To produce images of different regions of the brain that are active during activities
What is the function of the retina in the eye?
Detects light intensity and colour
What is the role of the optic nerve?
Carries electrical impulses from the eye to the brain
Fill in the blank: The _______ controls how much light enters the pupil.
iris
What are ciliary muscles responsible for?
Changing the shape of the lens to focus light
Define accommodation in the context of the eye.
The ability to focus on near or distant objects
What is adaptation in the eye?
The ability of the eye to adjust its structures in response to light intensity
What is the function of the iris in the eye?
Controls how much light enters the pupil
The iris adjusts the size of the pupil based on light intensity.
What do ciliary muscles do?
Relax and contract to change the shape of the lens
This action is crucial for focusing light on the retina.
What are suspensory ligaments?
Work with the ciliary muscles to change the shape of the lens
They attach to the lens and help regulate its curvature.
What is the function of the lens in the eye?
Transparent disc that changes shape to focus light onto the retina
The lens must adjust to focus on objects at different distances.
Define adaptation in the context of the eye.
The process by which the eye adjusts its structures in response to light intensity
This is a reflex action to protect the retina.
What happens to the pupil in dim light?
The pupil dilates (widens)
This allows more light to enter the eye.
What occurs to the pupil in bright light?
The pupil constricts (narrows)
This prevents too much light from damaging the retina.
What is accommodation in the eye?
The process of changing the shape of the lens to focus on near or distant objects
This is essential for clear vision at varying distances.
What happens when focusing on a near object?
Ciliary muscles contract, suspensory ligaments loosen, and the lens becomes thicker
This increases the lens’s refractive power.
What occurs when focusing on a distant object?
Ciliary muscles relax, suspensory ligaments are pulled tight, and the lens becomes thinner
This decreases the lens’s refractive power.
What are the two common defects of the eye?
- Myopia (short-sightedness)
- Hyperopia (long-sightedness)
Both defects affect how light focuses on the retina.
How is myopia treated?
Spectacle lenses that refract light to focus on the retina
New technologies like contact lenses and laser surgery are also available.
What is the role of the thermoregulatory centre in the brain?
Monitors and controls body temperature
It contains receptors sensitive to blood temperature.
What happens when body temperature is too high?
Blood vessels dilate (vasodilation) and sweat is produced
These actions help cool the body down.
What is vasoconstriction?
The narrowing of blood vessels when body temperature is too low
This reduces heat loss from the blood.
What is the result of sweating?
Heat energy is lost as liquid water in sweat becomes water vapour
This is a state change that cools the skin.
What does homeostasis involve?
The maintenance of a constant internal environment
Temperature control is an example of negative feedback.
What is homeostasis in biology?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
It maintains optimal conditions for enzyme action and all cell functions.
Which internal conditions are controlled by homeostasis in the human body?
- Blood glucose concentration
- Body temperature
- Water levels
How is maintaining homeostasis controlled in the body?
Maintaining controlled conditions within the body is under involuntary (automatic) control.
What are the components of a control system in homeostasis?
- Receptors
- Coordination centres
- Effectors
What is the role of the pancreas in blood glucose control?
The pancreas monitors and controls blood glucose concentration by producing insulin and glucagon.
What hormone does the pancreas produce when blood glucose concentration is too high?
Insulin
What is Type 1 diabetes?
Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels.
What is Type 2 diabetes?
Type 2 diabetes occurs when body cells no longer respond effectively to insulin produced by the pancreas.
What is deamination?
Deamination is the process of breaking down excess protein, predominantly occurring in the liver.
What does deamination produce from excess amino acids?
Urea
What is the function of the kidneys in the body?
The kidneys help control the water content of the body and the concentrations of substances dissolved in the fluids.
What is filtration in the kidneys?
Filtration is the process where high-pressure mass flow forces small molecules out of the bloodstream through the kidney filters.
What substances are forced out of the blood during filtration?
- Glucose
- Urea
- Water with ions dissolved in it
What is the role of ADH in water regulation?
ADH affects the permeability of the kidney tubules to water, regulating how much water is reabsorbed.
What happens when blood glucose concentration is too low?
The pancreas produces glucagon, which causes glycogen to be converted into glucose and released into the blood.
True or False: Glucagon is the hormone that stimulates the conversion of glycogen into glucose.
True
Fill in the blank: The human endocrine system is composed of ______ that secrete hormones directly into the bloodstream.
glands
Which gland is known as the ‘master gland’?
Pituitary gland
What is the primary function of insulin?
To lower blood glucose levels by stimulating cells to take in glucose.
What can high blood glucose levels lead to?
Cells losing water by osmosis, which can be dangerous.
What are the two main sources of water in the body?
- Water produced from aerobic respiration
- Water from the diet
What are the consequences of too much water in the blood?
Cells may swell and burst (cell lysis).
What is the main role of the kidneys in excretion?
To filter blood to produce urine, controlling water, ions, and urea.
What is kidney dialysis?
A treatment that acts as an artificial kidney to remove toxins and restore water and salt balance in the blood.
What is the difference between glucagon and glycogen?
Glucagon is the hormone, while glycogen is the polysaccharide that glucose is stored as.
What happens to urea in a healthy kidney?
Urea is not selectively reabsorbed and is excreted in urine.
What is the effect of ADH when blood water content is too high?
Less ADH is released, leading to less water being reabsorbed in the kidneys.
What is the purpose of a kidney transplant?
To provide a long-term solution to kidney failure.
What is a risk factor for Type 2 diabetes?
Obesity
What is the consequence of kidney failure?
A build-up of toxic wastes in the body, which can be fatal.
What is dialysis?
An artificial method of filtering the blood to remove toxins and excess substances
Dialysis is commonly used for patients with kidney failure.
What is a better long-term solution to kidney failure than dialysis?
Kidney transplants
Kidney transplants provide a more permanent solution compared to dialysis.
What are some disadvantages of kidney transplants?
- Immune response to new kidney due to differing antigens
- Need for lifelong immunosuppressant drugs
- Long-term side effects of immunosuppressants
- Vulnerability to infections
- Insufficient donors to meet demand
These factors can complicate the success of kidney transplants.
How can the risk of rejection in kidney transplants be reduced?
By ‘tissue typing’ the donor and the recipient first
Tissue typing ensures better compatibility between the donor and recipient.
What are the benefits of a kidney transplant over dialysis?
- More freedom for the patient
- Less restrictive diet
- Removal of the high cost of dialysis machines
- Long-term solution
These benefits make kidney transplants a preferable option for many patients.
What does the best answer about dialysis refer to?
Differences in concentration gradients between the dialysis fluid and the blood
Understanding concentration gradients is crucial for explaining the movement of substances during dialysis.
Fill in the blank: Dialysis is used to filter the blood to remove _______.
toxins and excess substances
This highlights the primary function of dialysis in treating kidney failure.
True or False: A kidney transplant eliminates the need for immunosuppressant drugs.
False
Immunosuppressant drugs are necessary to prevent rejection of the transplanted kidney.
Fill in the blank: A kidney transplant offers a _______ solution compared to dialysis.
long-term
This emphasizes the sustainability of kidney transplants for patients.
What are plant hormones called that coordinate and control growth?
Auxins
What is the positive phototropic response in plants?
Shoots grow upwards towards light
What is the negative gravitropic response in plants?
Roots grow downwards away from light
Where are auxins produced in plants?
In the tips of the shoots and roots
What effect does auxin have in the shoots?
Promotes cell elongation
What effect does auxin have in the roots?
Inhibits cell elongation
What happens to auxin distribution when a shoot is placed on its side?
Auxins accumulate along the lower side
What causes the shoots to grow upwards when placed on their side?
The lower side grows faster due to higher auxin concentration
What is the role of gibberellins in plants?
Initiates seed germination and induces flowering
What gas released by plants controls cell division and ripening of fruits?
Ethene
What is the aim of the required practical investigating plant growth?
To investigate the effect of light or gravity on the growth of newly germinated seedlings
What is a clinostat used for in plant experiments?
It cancels out the effect of gravity
What is the expected growth direction of radicles in a gravitropic response?
Downwards
What happens to seedlings placed on a clinostat in terms of gravitropic response?
They grow straight outwards, showing no gravitropic response
What are the commercial uses of plant hormones?
Control plant growth to obtain larger yields
How do auxins work as selective weed killers?
Negatively affect the growth of broadleaved plants
What is the purpose of rooting powders containing auxins?
To encourage rapid development of roots in plant cuttings
How is ethene used in the food industry?
To control ripening of fruit during storage and transport
What effect does gibberellin have on seed dormancy?
Ends seed dormancy and promotes germination
What is the role of gibberellins in fruit development?
Increases fruit size by promoting growth
Fill in the blank: Auxins promote _______ in shoots.
cell elongation
Fill in the blank: Ethene can be used to _______ the ripening of fruits.
control
True or False: Auxins are only produced in the roots of plants.
False
True or False: Gibberellins can promote flowering regardless of weather conditions.
True
