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Unit 5 - module 2

Define "Homeostasis"

The maintenance of a stable internal environment.

Why is homeostasis important?

We must be able to adjust to changes in our environment because living cells can function only within a narrow range of:
-oxygen and nutrients availability
-pH & ion concentration

What is meant by "set point"?

An average of the fluctuation of conditions inside our bodies (within the narrow range).

What does homeostasis require?

- a receptor - that receives info about a change
- an effector that responds and bring about changes to return to set point
- an efficient means of communication between the receptor and the effector
- continuous monitoring of the factor being controlled

What is negative feedback?

When the body senses an internal change and then acticates mechanisms that reverse the change.

What is the role of the involuntary/autonomic nervous system in homeostasis?

-responsible for homeostasis
-controls are done automatically below the conscious level

Features of autonomic nervous system?

-consists of 2 sets of motor neurons carrying impulses to effectors
-Neurones of the sympathetic and parasympathetic nervous system have different effects.
-Coordinatinated by hypothalamus

How do effectors reduce heat loss of human?

-vasoconstriction of skin arterioles
-contraction of hair erector muscles
-decreasing sweating

Why is it important to measure core body temperature?

-because a number of diseases are accompanied by characteristic changes in body temperature (e.g. fever)

-as a way of monitoring the course of certain diseases

-for doctor to evaluate the efficiency of a treatement

What is hypothermia and hyperthermia?

Hypothermia occurs when the body's core temp drops below 35degrees.

Hyperthermia occurs when the core body temp rises significantly above normal.

Give 3 symptoms of hypothermia?

-weak pulse
-muddled thinking/ inability to think

Give 3 symptoms of hyperthermia?

-Mental confusion
-muscle cramps

How do we become acclimatised to living in cold conditions?

Thyroid gland secrets extra thyroxin. Thyroxin increases the metabolic rate which increases heat production.

What are the different ways in which body temperature can be measured?

- Electronic thermometers - measures how well electricity travels through a wire. (mouth, rectum or armpit)

- Ear thermometers - uses infrared energy; ear temp reflect core body temp better because the eardrum shares its blood supply with hypothalamus

- Forehead thermometers

Why is hypothermia are problem?

As the core temp falls all metabolic reaction slow down, this is because molecules have less kinetic energy so there will be fewer collisions between enzymes & their substrates.

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