Communication and homeostasis

Question 1

What is Cell Signalling?

Answer 1

They involve receptors on molecules on the cell surface membrane. the cell signalling molecules have a shape complementary to the shape of their receptors.

Question 7

Why would cells need to communicate?

Answer 7

• to create a co-ordinated response.
• to identify/ recognize each other via cell signalling.

Question 7

What are the two communication systems?

Answer 7

Neuronal and Hormonal.

Question 7

Explain the hormonal system

Answer 7

There is no specific pathway.
Cells within the endocrine glands release hormones directly into the blood. It is a chemical messenger which has a specific shape then recognised by specific target cells. this system allows longer term responses to co-ordinated a long with short term.
chemical transmission
slower transmission

Question 7

Explain the nervous system

Answer 7

The pathway is specific to nerve cells. Interconnected network of neurones that signal to each other across synapses via neurotransmitters. These neurones are specialised cells which can conduct electrical impulses, very quickly to enable rapid responses.
it is both a chemical and electrical transmission.
rapid transmission + response

Question 8

What is homeostasis?

Answer 8

Maintenance of a stable internal environment around set points despite internal/external environment.

Question 8

What is negative feedback?

Answer 8

When a change occurs it initiates a series of events and negative feedback is a mechanism that reverses the changes to bring back the system to optimum.

Question 9

What is positive feedback?

Answer 9

Mechanism that increases a change, taking the system further away from the optimum, tends to be harmful and NOT involved in homeostasis.

Question 10

What is thermoregulation?

Answer 10

Controlling body temperature.

Question 12

What is the core temperature?

Answer 12

Operating temperature inside body. [close to set point]

Question 13

What is the peripheral temperature?

Answer 13

Temperature of skin. [more variable as it can be influenced by environment]

Question 14

What is conduction?

Answer 14

Transfer of heat from hotter to the cooler of two objects in contact. Heat energy can also be conducted to surrounding mediums.

Question 15

What is convection?

Answer 15

Warmer air is less dense and so will rise through surrounding colder air and so creating air currents. This speeds up loss of energy.

Question 16

What is radiation?

Answer 16

Transfer of heat energy from a body to colder objects that are not in contact with each other. The heat energy is transferred by infrared waves.

Question 17

What are endotherms?

Answer 17

[mammals]
They are organisms that use heat from metabolic reactions to maintain body temperature so they have a higher metabolic rate. They control body temps with strict limits and use a variety of mechanisms to control it.

Question 18

What are ectotherms?

Answer 18

[fish, lizards]
rely on external sources of heat to maintain body temp.
they can’t control their temp internally and so can’t increase their metabolism to increase temp.
body temp fluctuates w/ external temp.
activity level depends on external temp.

Question 19

What are the disadvantages of being an ectotherm?

Answer 19

Can’t exploit as many locations.
More susceptible to predation if less active.
Less active as colder temps limits them.

Question 20

What peripheral temp receptors ?

Answer 20

detects changes in the temperature of the skin and impulses to hypothalamus.

Question 21

What is the hypothalamus role with thermoregulation?

Answer 21

monitors temp of blood flowing through it
receives impulses from peripheral temp receptors in skin.
sends impulses to motor neurones to sweat glands and muscles in arterioles and skeletal muscles and hair erectors muscles.
increases metabolism and increase exogamic reactions

Question 22

What are the advantages of ectotherms?

Answer 22

• less of their food is used in respiration
• more of the energy is gained from and can converted to growth
• they need to find less food
• they can survive for long periods without food.

Question 23

What are the advantages of endotherms?

Answer 23

maintain a fairly constant body temperature whatever the temperature externally.
- remain active even when external temps are low.
- can inhabit colder parts of the planet.

Question 24

What are the disadvantages of endotherms?

Answer 24

use a significant part of their energy intake to maintain body temp.
- need more food
- less energy and nutrients used for growth.
- may overheat in hot weather.

Question 25

What happens in response to when the body temp is lowered?

Answer 25

• Vasoconstriction occurs [narrowing of arterioles to prevent less radiation of heat out]
• erectors muscles contract causing hairs to stand up for insulation to trap heat.
• Muscles contract to cause shivering and respiration to release heat.

Question 26

What happens in response to when the body temp is higher?

Answer 26

• Vasodilation occurs.
• Muscles relax to prevent any release of heat.
• hairs lowered
• Sweat gland have a blood supply that provides the fluid for making sweat.