Communication and Homeostasis Flashcards Preview

OCR A-level Biology > Communication and Homeostasis > Flashcards

Flashcards in Communication and Homeostasis Deck (26)
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What conditions do cells need to maintain?

Aqueous environment (solute concentrations)
Freedom from toxins and inhibitors


What will happen if conditions are compromised?

Cells will be damaged, become inactive and potentially die.


Why do cells communicate?

Cells all all specialised for a specific purpose
Need to communicate so they can carry out functions smoothly


How do he actions of the cells alter their own external environment?

Some products of metabolic reactions are toxic

They are moved out of the cell into the tissue fluid

Therefore altering the external environment of the cell


How does the body maintain its internal environment?

Moves toxins into tissue fluid

These then move into blood

Moved to excretory organs (kidneys and liver)



List features of a good communication system

Cover the whole body

Enable cells to communicate with each other

Enable specific communication

Rapid communication

Enable both long and short term responses


How does cell singanling work?

Cells release a specific chemical

Second cell has a receptor for this chemical which it binds to sending the message


What are the 2 major communication systems?

Neuronal System

Hormonal system


How does the neuronal system work?

network of neurons that signal to each other via synapses

Can send signals very quickly and responses are rapid


How does the emdocrine system work?

Uses the blood to send signals

Endocrine system secretes hormones directly into blood

Response takes longer to come to effect but enables a longer term response


What does homeostasis regulate?

Body temp
Blood glucose concentration
Blood salt concentration
Water potential of blood
Blood pressure
CO2 Concentration


What are sensory receptors?

Sensory receptors are on the surface of the body

They monitor the external environment and alert the body to change

When stimulated it sends a signal to an effector


What is an Effector?

Cells that bring about a response

such as Muscle (sarcomeres) or liver cells (hepatocytes)


What is negative feedback?

A change is detected

The body responds in opposition to this change

Return the body to optimum


What is positive feedback?

A change is detected

The body reacts to exacerbate this change

This moves the body away from optimum so is usually harmful


Why is positive feedback often harmful?

Because it moves the body away from optimum conditions

Enzymes can become less effective and even become denatured

Impacts metabolic reactions causing harm to the body


What is an example of where positive feedback is beneficial the body?

Cervix dilation during labour

The body detects the stretch of the cervix

The pituitary gland releases oxytocin which increases uterine contractions causing the crevix to stretch more

This is essential for a safe delivery of the baby


What is an endotherm?

An organism that regulates its own internal body temperature

Very strict tolerances

largely independent of external factors


What is an ectotherm?

Can't control own body temp

rely on external sources

use behavioral mechanisms to maintain body temperature in different conditions


Give examples of how ectotherms maintain body temp

Too hot:
Move to a sunny area/ lie on a warm surface
expose more of their surface area to the sun

Too cold:
Move out the sun
Move underground
reduce surface area exposed to the sun


Give 4 advantages of Ectothermy

Less energy used in respiration

More nutrients gained from food (because less energy is required)

Don't need to find food as often

Can survive long periods without any food


Give a disadvantage of Ectothermy

Less active in cold environments

so they are more at risk from predators when it is cold


Give 3 advantages of Endothermy

Can maintain fairly constant temperature despite external conditions

Remain active even when environment is cold

Can inhabit colder parts of the planet


Give 4 disadvantages of Endothermy

Use energy in order to maintain body temperature in cold conditions

Require more food

Less energy can be used towards growth

Can overheat in hot conditions


Where are the temperature receptors in the brain?



What is the role of periphery temperature receptors?

To give the hypothalamus an early warning that core body temperature could change