1.5 - Response and regulation

What are receptor cells?

Cells that detect external stimuli and send an electrical signal along neurones to the Central Nervous System (CNS), made up of the brain and the spinal cord, to coordinate a response.

What are the 5 sense organs and their stimulus?

Eyes - Light

Ears - Sound

Nose - Chemical smells

Tongue - Chemical tastes

Skin - Pain, pressure and temperature

What is a reflex response always?

Rapid, automatic and (generally) protective.

What is the order of the reaction to change in humans?

Stimulus, Receptor, Sensory neuron, CNS, Motor neuron, Effector.

What is the reflex arc?

The path taken by an electrical impulse from stimulus to response by an effector (muscle or gland). Withdrawal action reflex is shown during an automatic reaction.

What is homeostasis?

The maintenance of a constant internal environment.

What are hormones?

Chemical messengers secreted in to the blood by glands.

What is negative feedback?

Any change from the balance in optimal internal conditions, resulting in the body’s hormonal and nervous systems compensating for the change and restoring the balance.

What happens when glucose increases in blood (due to eating)?

Pancreas detects increase and releases the hormone - insulin - into the blood. Insulin travels to liver and liver turns glucose into insoluble glycogen for storage. Glucose level decreases to normal.

What happens when glucose decreases in blood (due to exercising)?

Pancreas detects the decrease and releases the hormone - glucagon - into the blood. Glucagon tells liver to turn stored glycogen into glucose and release into the blood. Glucose levels in blood increase to normal level.

What is diabetes?

A condition where you are unable to control your own blood glucose levels. In Type I diabetes the body does not release insulin. In Type II diabetes the body cells do not respond to the chemical signal from insulin.

What are the symptoms of diabetes?

Glucose detected in urine (by a Benedict’s test).

How can diabetes be treated?

By injecting insulin, having a low sugar/carbs diet and pancreatic transplants.

How does your body regulate temperature when you are too hot?

Hair lies flat. A layer of liquid sweat (made by sweat glands, carried up by sweat ducts and released by sweat pores onto the skin) evaporates, removing heat energy. Vasodilation - blood vessels in the skin widen so more heat from the blood is lost to the environment.

How does your body regulate temperature when you are too cold?

Hairs stand on end to trap a layer of insulating air over skin, reducing heat loss. Shivering (involuntary contraction of muscles) increases respiration and the release of heat energy. Vasoconstriction - blood vessels in the skin get narrower so less heat is lost from the blood to the environment.