B11 Systems in balance

Define the term stimuli.

Changes in the environment such as daylight, wind, speed, pressure, temperature, movement, and availability of food that living organisms detect.

What's the difference between a receptor and an effector?

Receptors are cells that detect stimuli (like taste buds), whereas effectors are organs that bring about responses (such as muscles and glands).

What does the human nervous system consist of?

The central nervous system (CNS) and the peripheral nervous system (PNS).

What organs make up the central nervous system?

The brain and the spinal cord, both of which are areas of coordination.

What makes up the peripheral nervous system?

It is made up of all nerves that connect the central nervous system to the rest of the body.

What's the combined function of the CNS and the PNS?

Together, they serve to coordinate and regulate bodily functions.

What do motor neurones do?

They transmit impulses away from the brain and spinal cord to effector organs like muscles and glands.

What do relay neurones do?

These are short neurons that pass on impulses from sensory neurones to motor neurones inside the brain and spinal cord.

What do sensory neurones do?

They transmit information from sensory organs to the brain and spinal cord.

Define a reflex (involuntary) action.

A means of automatically and rapidly integrating and coordinating stimuli with responses.

What is a neurone?

Neurones are highly specialized cells whose structures allow them to transmit information over long distances.

Define the phrase 'reflex arc'.

The pathway of the impulse along the neurones.

Explain the process of a reflex arc in detail.

Receptors receive a stimulus; a nerve impulse is sent down a sensory neurone; connects via a synapse to a relay neurone; which connects via a synapse to a motor neurone; which connects to an effector (e.g., a muscle or a gland); which brings about a response (e.g., muscle contraction).

Define homeostasis.

Homeostasis is the maintenance of a constant internal environment within an organism, despite changes in the external environment.

Explain how negative feedback mechanisms maintain homeostasis.

Negative feedback mechanisms detect deviations from a set point and initiate responses to counteract changes, restoring the internal environment to its optimal state.

How do mammals regulate their internal body temperature?

Mammals regulate body temperature through insulation (hair or fat layers), sweating, shivering, and brain regulation. They also use vasodilation and vasoconstriction of blood vessels to control heat loss or retention.

What are vasodilation and vasoconstriction

and how do they assist in temperature control?,Vasodilation is the widening of blood vessels near the skin surface to increase heat loss; vasoconstriction is the narrowing of blood vessels to reduce blood flow and conserve heat.

How does the eye convert light energy into electrical impulses?

Photoreceptor cells in the retina (rods and cones) detect light and generate electrical impulses, which are sent to the brain via the optic nerve for visual processing.

Identify the main structures of the eye and their functions.

Cornea refracts light; iris controls pupil size and light entry; pupil allows light into the eye; lens focuses light onto the retina; retina contains photoreceptors; optic nerve transmits visual information to the brain; blind spot is where the optic nerve exits.

Explain the pupil reflex and the roles of the iris muscles.

The pupil reflex adjusts pupil size in response to light intensity: in bright light, circular muscles contract and radial muscles relax, causing pupil constriction; in dim light, radial muscles contract and circular muscles relax, causing pupil dilation.

What is accommodation in the eye

and how is it achieved?,Accommodation is the adjustment of the lens shape to focus on near or distant objects, achieved by ciliary muscles contracting or relaxing to change lens thickness, with suspensory ligaments adjusting tension accordingly.

Define a hormone and describe its function in the endocrine system.

A hormone is a chemical substance produced by an endocrine gland, carried in the blood to target organs, where it alters their activity to regulate bodily functions.

List key endocrine glands and the hormones they secrete.

Adrenal glands secrete adrenaline; pancreas produces insulin; testes produce testosterone; ovaries produce oestrogen.

Describe the effects of adrenaline during 'fight or flight' situations.

Adrenaline prepares the body by increasing heart rate and breathing rate, dilating pupils, raising blood glucose levels, and redirecting blood flow to muscles.

How does insulin regulate blood glucose concentration?

Insulin decreases blood glucose levels by promoting glucose uptake by body cells and stimulating the liver to convert glucose into glycogen for storage.

Explain the roles of insulin and glucagon in blood glucose regulation.

Insulin lowers blood glucose when levels are high; glucagon raises blood glucose when levels are low by stimulating glycogen breakdown in the liver.

What are the causes and treatments of Type 1 and Type 2 diabetes?

Type 1 diabetes is caused by the pancreas producing little or no insulin and is treated with insulin injections and dietary management; Type 2 diabetes is caused by body cells resisting insulin effects and is treated with lifestyle changes, medication, and sometimes insulin therapy.

Why is excretion important

and what roles do the liver and kidneys play?,Excretion removes toxic waste products; the liver converts excess amino acids into urea, and the kidneys filter blood to excrete urea, excess water, and ions as urine.

What could happen if the excretory system fails to remove metabolic waste?

Accumulation of toxic substances like urea can disrupt cellular functions, leading to organ failure and potentially death.

Describe common diseases of the liver and kidneys and their consequences.

Liver diseases like hepatitis and cirrhosis impair detoxification and metabolism; kidney diseases like chronic kidney disease lead to waste accumulation; consequences may require treatments like dialysis or transplantation.

Compare the nervous and endocrine systems in terms of speed and duration of responses.

The nervous system is rapid with short-term effects using electrical impulses via neurons; the endocrine system is slower with long-lasting effects using hormones via the bloodstream.

How do organisms detect and respond to changes in their environment?

Organisms use receptors to detect stimuli; the nervous system processes information; effectors (muscles or glands) respond to maintain homeostasis.

What are interdependent relationships in biological systems?

Interdependent relationships are mutual dependencies between organisms or systems that rely on each other for survival and proper functioning, such as coordination between the nervous and endocrine systems.

How do living things achieve balance with a changing environment?

By detecting changes through receptors, processing information via nervous and endocrine systems, and initiating appropriate responses to maintain homeostasis.