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Biology - OCR A > 5.1.1 - Communication And Homeostasis > Flashcards

5.1.1 - Communication And Homeostasis Flashcards

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1
Q

What is the purpose of an effective communication system in organisms?

A

To ensure an organism is able to function effectively.

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2
Q

What is a stimulus in the context of cell signaling?

A

An environmental change like temperature.

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3
Q

What is the response in the context of a stimulus?

A

A change in behaviour or physiology.

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4
Q

What is the difference between external and internal stimuli?

A

External stimuli are environmental changes; internal stimuli are changes to tissue fluid and blood composition.

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5
Q

What are the components of the coordinating communication system?

A
  • Stimulus
  • Receptor
  • Effector
  • Response
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6
Q

What is the standard response pathway for homeostasis?

A

Stimulus → Receptor → Communication pathway → Effector → Response.

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7
Q

Where are sensory receptors typically found?

A

On surfaces like the skin and in the brain.

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8
Q

What do sensory receptors do when they detect a change?

A

They send a signal to an effector.

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9
Q

What are the two main communication systems in the body?

A
  • Neural system
  • Hormonal system
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10
Q

What is homeostasis?

A

The maintenance of a constant internal environment despite changes in external and internal factors.

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11
Q

List six examples of homeostatic control systems.

A
  • Blood glucose concentration
  • Body temperature
  • Blood pressure
  • Water potential of the blood
  • Blood salt concentration
    *Carbon dioxide concentration
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12
Q

What is negative feedback?

A

A mechanism used to reverse changes to maintain a constant environment.

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13
Q

Fill in the blank: The closer the conditions get to optimum, the receptors detect the reduction in stimulus so they reduce the _______.

A

input that is sent to the coordination centre.

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14
Q

True or False: The effector causes a change back to the optimum conditions.(negative feedback)

A

True.

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15
Q

What role do effectors play in the communication system?

A

They match a response to the stimulus (muscle or gland).

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16
Q

What are the main steps of negative feedback?

A
  1. Conditions in the body change from a set point
  2. The change is detected by receptors in/out of the body
  3. Once the receptor has received a signal a corrective mechanism, is activated
  4. Conditions return to a set point
  5. Corrective mechanism is switched off
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17
Q

What is an example of cell signaling between adjacent cells?

A

The nervous system secreting neurotransmitters which send signals to other nerve cells or muscle cells

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18
Q

What is an example of cell signalling between distant cells?

A

The hormonal system releases hormones which travel through the blood and are detected by cell surface receptors

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19
Q

What is the difference between receptors and effectors?

A
  • Receptors detect specific stimuli, like pressure change
  • Effectors are cells that bring about a response to a stimulus, like muscles contracting
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20
Q

What is a positive feedback mechanism?

A

A process that amplifies or increases the effects of a stimulus.

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21
Q

True or False: Positive feedback mechanisms are commonly involved in homeostasis.

A

False
It is not involved as it does not keep the internal environment constant

22
Q

Fill in the blank: In a positive feedback loop, the output enhances the __________.

A

initial stimulus

23
Q

Which of the following is an example of a positive feedback mechanism? A) Blood sugar regulation B) Childbirth C) Body temperature control

A

B) Childbirth

24
Q

Short answer: Describe one situation in which a positive feedback mechanism is beneficial.

A

During childbirth, the release of oxytocin increases contractions, facilitating delivery.

25
Q

Fill in the blank: Positive feedback is useful to ______________ something, eg. blood clots after injuries

A

Rapidly activate

26
Q

What is the effect of increased temperature on molecular activity?

A

Increased temperature provides more kinetic energy, leading to faster molecular movement and increased collision rates.

This results in a faster rate of chemical reactions.

27
Q

What happens to enzyme-controlled reactions at higher temperatures?

A

Enzymes can denature due to increased temperature, disrupting the complementarity between the substrate and active site.

Denaturation affects the enzyme’s functionality.

28
Q

Define ectotherms.

A

Organisms that rely on external sources to maintain body temperature.

Examples include fish, reptiles, and amphibians.

29
Q

Define endotherms.

A

Organisms that use heat from metabolic reactions to maintain body temperature.

Examples include mammals and birds.

30
Q

How do ectotherms generally regulate their temperature?

A

Through behavioral means such as:
* Moving out of direct sunlight
* Going underground
* Orientating their body away from the sun
* Moving into the sun
* Lying on warm surfaces
* Orientating their body towards the sun

These behaviors help maintain optimal body temperatures.

31
Q

How do endotherms regulate their body temperature?

A

Through both behavioral and physiological mechanisms.

They do not rely on external heat sources.

32
Q

What are the three mechanisms endotherms do to reduce body temperature?

A
  • Sweating
  • Hairs lie flat
  • Vasodilation
33
Q

What mechanisms do endotherms use to increase body temperature?

A
  • Shivering
  • Much less sweat
  • Hairs stand up
  • Vasoconstriction
  • Hormones
34
Q

How does sweating reduce body temperature?

A
  • More sweat is secreted from the sweat glands
  • The water in the sweat evaporates from the surface of the skin to take heat from the body
  • This cools the skin
35
Q

How does hairs laying flat reduce body temperature?

A
  • Erect pili muscles relax causing the hairs to lie flat
  • This traps less air, so the skin is less insulated
  • Heat can be lost more easily
36
Q

How does vasodilation reduce body temperature?

A
  • Arterioles near the skin surface dilate
  • This means more blood flows through the capillaries in the dermis
  • This cause more heat to be lost from the skin by radiation lowering the temperature
37
Q

How does shivering increase body temperature?

A
  • When it is cold the muscles contract in spasms
  • This makes the body shiver producing more heat from respiration
38
Q

How does sweating less increase body temperature?

A
  • Less sweat is screamed from the gland which reduces heat loss
39
Q

How does hairs standing up increase body temperature?

A
  • Erector pili muscles contract when it’s cold
  • This causes the hairs to stand up and trap more hair
  • This prevents heat loss
40
Q

Fill in the blanks: Vasoconstriction is when _______ near the surface constrict, so less blood flows through the _________ in the dermis.

A
  1. Arterioles
  2. Cappilaries
41
Q

Fill in the blanks: The body releases ___________ and ___________ (hormones) to increase metabolism so less heat is produced

A
  1. Adrenaline
  2. Thyroxine
42
Q

What part of the brain is primarily responsible for regulating body temperature?

A

The hypothalamus.

43
Q

True or False: The hypothalamus can induce sweating to help cool the body.

A

True.

44
Q

Fill in the blank: The hypothalamus maintains body temperature by balancing heat production and _____ .

A

heat loss.

45
Q

Which physiological response is initiated by the hypothalamus when body temperature rises?

A

Vasodilation and sweating.

46
Q

Multiple Choice: What is the set point temperature for the human body that the hypothalamus typically maintains? A) 36.5°C B) 37.0°C C) 38.5°C D) 39.0°C

A

B) 37.0°C.

47
Q

What are the receptors in the hypothalamus?

A

Thermoreceptors

48
Q

What happens after the thermoreceptros detect a change in temperature?

A
  1. Send an impulse along the sensory neurones to the hypothalamus
  2. This sends an impulse along the motor neurones to the effectors
49
Q

How do plants increase their chance of survival?

A

Responding to changes in the environment

50
Q

How do animals increase their chance of survival?

A

By responding to their external environment (avoiding harmful environments) and responding to their internal environment changing so that their conditions are optimal for their metabolism

Biology - OCR A (25 decks)

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