Homeostasis

Question 1

descrbie the difference between a stimulus an a response

Question 2

what is the purpose of homeostasis

Question 3

clarify how positive and negative feedback differ. suggest why positive feedback is generally not associated with homeostasis.

Question 4

what are the by products of cellular respiration

Question 5

differentiate between a tolerance range and optimal range

Question 6

explain the differences between cellular respiration and metabolic activity

Question 7

explain difference between ectotherms and endotherms

Question 8

define homeostasis

Answer 8

the process by which the body maintains a constant internal environment, this is done by nerves and hormones. it is important because many reactions (enzymes) only work at certain conditions

Question 9

what is the reange of deviation called

Answer 9

tolerance limits are the range of deviation that is acceptible for certain varations such as temperature, blood glucose levels, etc.

Question 10

define the stimulus response model

Answer 10

the body’s way of detecting a change in its external or internal environment, and reacting accordingly.

Question 11

what is regulation

Answer 11

regulation is responding to fluctuations around a set point.

Question 12

define negative feedback loop

Answer 12

information produced by the feedback causes a reversal in the effect of the stimulus

Question 13

describe in general terms how an organism maintains its internal environment within tolerance limits

Answer 13

homeostasis is the process by which the body maintains a stable internal environment through a stimulus-response negative feedback model, which works as follows:

1. stimulus: change in the internal or external environment
2. receptor: receptor detects stimulus
3. central nervous system: receptor produces a signal to send to the central nervous system to coordinate a response
4. effector: central nervous systems send message to an effector, such as muscles or glands
5. response: effector conducts a response to restore the body to its balanced state.

Question 14

Negative feedback mechanisms are typically used to maintain homeostasis.

Describe the main features of a negative feedback mechanism.

Answer 14

Change in internal environment (stimulus)
Receptor detects the change
Signal sent from receptor to the control centre (central nervous system) and processed
Signal sent from the control centre to the appropriate effector
Effector responds to the signal and restores homeostasis (reverses the effect of the stimulus)

Question 15

Outline the role of the effector in homeostasis.

Answer 15

An effector is responsible for amending a homeostatic imbalance that has been communicated to the control centre. Effectors are either muscles or glands. Muscles will either expand or contract, whereas glands will release a secretion.

Question 16

Outline the role of receptors in homeostasis.

Answer 16

Receptors detect changes in homeostasis. There are a variety of different types of receptor, all of which are able to respond to different types of stimuli. These receptors operate according to set levels. When they detect a deviation from a set level, the receptor sends a signal to the control centre.

Question 17

define endotherm

Answer 17

warm-blooded, largely create heat by adjusting processes in their bodies (we are endotherms), rely mainly on physiological sources of heat to regulate internal temperature

Question 18

define ectotherm

Answer 18

cold-blooded, rely on external sources of temperature to heat up or cool down, depend solely on the environment for heat regulation.

Question 19

physiological responses to cold to reduce heat loss

Answer 19

1. piloerection. hairs erect on your skin, trap air close to skin, preventing heat loss via the convection of air.
2. vasoconstriction. blood vessels constrict, so less blood travels near the skin’s surface. Less heat is lost from the blood

Question 20

physiological responses to cold to increase heat production

Answer 20

1. shivering. muscle cells perform respiration in order to break down glucose and make energy. respiration releases heat.
2. increasing metabolism. main source of heat production when your body is at rest. endocrine system can be used to influence the production of heat via metabolism.

Question 21

behavioural responses to cold to both reduce heat loss and increase heat production

Answer 21

reduce heat loss: seeking shelter, putting on clothing, decreasing surface area.
increasing heat production: voluntary movement.

Question 22

responding to heat, physiological processes to increase heat loss.

Answer 22

1. vasodilation, blood actively losses heat to the external environment.
2. sweating, from by glands on skin, this draw heat from the skin to evaporate the sweat, converting a liquid to a gas.

Question 23

responding to heat, physiological processes to reduce heat production

Answer 23

1. decreasing metabolism, in response to heat, the hypothalamus reduces the rate of cellular respiration in the bodies internal organs

Answer 24

Conduction, convection, radiation and evaporative cooling are the four ways we exchange heat with our environment, not rumination!

Question 25

Identify TWO responses of a named endotherm to a decrease in body temperature.

Answer 25

Shivering and vasoconstriction in humans.

Question 26

Outline the role of the nervous system of an endotherm in maintaining homeostasis when its body temperature changes.

Answer 26

Changing body temperature is detected using temperature receptors in the skin and brain. A signal is sent via nerves from the receptors to the central nervous system. Nerve signals are then sent from the CNS to effectors (muscles or glands).

Question 27

Explain how humans maintain homeostasis in response to changes in temperature.

Answer 27

The human sensory nervous system is responsible for detecting changes in temperature. Specific receptors on the skin are designed to detect specific temperatures and transmit that information along nerves to the brain. In response, effector tissues are activated to adapt to the detected changes and maintain homeostasis. For example, in response to cold, humans will shiver to generate heat in the muscles. This maintains a constant internal temperature.

Question 28

Distinguish between endotherms and ectotherms.

Answer 28

The body temperature of ectotherms is regulated by the ambient, or environmental temperature, as they are unable to generate heat themselves. Endotherms thermoregulate by modifying their internal body processes, using a negative feedback loop where a change in body temperature (stimulus) is detected by a thermoreceptor (receptor). This change is interpreted by the central nervous system (control centre) which activates an effector, producing a response which cancels out the original stimulus.

Question 29

Describe one structural feature and one physiological process that enables mammals living in cold environments to maintain a constant core body temperature. Identify clearly in your answer which is the structural feature and which is the physiological process.

Answer 29

Structural feature: Thick fur coat Traps layer of air close to body, providing insulation This reduces heat loss by conduction Stops air flow close to body, reduces heat loss by convection Hairs may be hollow (more insulation from hollow core) Furry tail can be folded over nose/extremities to improve insulation Physiological process: Vasoconstriction Blood vessels in skin constrict Restrict blood flow to skin, reducing temperature of skin Reduces heat loss through radiation Most blood remains below the insulating fat layer

Question 30

Rabbits have the ability to control the amount of blood flow to their ears. Explain how this can help them to thermoregulate.

Answer 30

Rabbits are endothermic, meaning that they maintain a constant internal temperature regardless of the temperature of the environment. The blood flowing from the body to the ears is relatively warm. The ear is in close contact with air, therefore heat in blood can be lost via the ear. If the air temperature is warm, rabbits increase the blood flow to their ears through vasodilation. This increases heat loss by radiation (and/or by convection if the rabbit is moving). If air temperature is cold, rabbits decrease the blood flow to their ears through vasoconstriction. This retains heat in their body (rather than losing heat to the environment).

Question 31

what is osmoregulation

Answer 31

the control of the concentration of body fluids, in order to maintain water balance, it controls how much water there is compared to other dissolved substances (solutes) in the body.