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Biology module 5 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is a sensory receptor

A

detects changes in the internal and external environment of an organism

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2
Q

What is homeostasis

A

maintenance of stable body conditions, a dynamic equilibrium with small fluctuations

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3
Q

What is an effector

A

A muscle or gland that reacts to a motor stimulus to bring about change in response to a stimulus

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4
Q

Features of a negative feedback system

A
  • change is detected, effectors work to reverse change and restore initial conditions
  • reverse the stiumulus
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5
Q

Examples of a negative feedback system

A

blood sugar level control

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6
Q

Features of positive feedback systems

A
  • change is detected, effectors are stimulated to reinforce the change and increase the response
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7
Q

Examples of positive feedback systems

A
  • blood clotting= platelets stick and attract more until clot formed
  • child birth= baby head against cervix stimulates oxytocin, which stimulates uterus contraction, causing head to press and repeat
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8
Q

What is thermoregulation

A

the maintenance of a relatively constant core body temperature to maintain optimum enzyme activity

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9
Q

Processes that can cause temperature to change, and what they are

A
  • exothermic chemical reactions
  • latent heat of evaporation= cool as water evaporates
  • radiation= transmission of electromagnetic waves too and from the air, water or ground
  • convection= heating and cooling by currents of air and water (warm rises, cold sinks)
  • conduction= heating as a result of the collision of molecules
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10
Q

What are ectotherms

A
  • use their surroundings to warm their bodies
  • core body temperature dependent on their environment
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11
Q

Examples of ecotherms

A

invertebrates, fish, reptiles, amphibians

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12
Q

Why do ectotherms not need to thermoregulate

A
  • IF they live in water, the high heat capacity of water means the temperature is relatively constant
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13
Q

What are on endotherms

A
  • rely on metabolic processes to warm up
  • have adaptations to enable maintenance of body temperature
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14
Q

Examples of endotherms

A
  • mammals
  • birds
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15
Q

Behavioural responses to change temperatures

A
  • increase/decrease radiation from the sun = BASKING
  • lie in sun exposing maximum surface area
  • press bodies against warm ground= conduction
  • cool down by seeking shade, press against cold surfaces, minimal surface area exposed to the sun
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16
Q

Physiological responses to warming

A
  • dark colours to absorb more radiation
  • some ectotherms alter heart rate to increase or decrease metabolic activity
17
Q

How are temperature changes detected

A
  • peripheral temperature receptors in the skin detect changes in the surface temperature
  • temperature receptors in the hypothalamus detect the change if temperature of blood deep in the body
  • combination of the 2 gives the body sensitivity and allows it to respond
  • temperature receptors in the hypothalamus act as the thermostat in the body
  • should be kept within 1 degrees of 37
18
Q

Principles of thermoregulation in endotherms

A
  • use internal exothermic metabolic activities to keep warm
  • use energy requiring physiological processed to keep cool
  • also rely on behavioural responses (basking, digging burrows etc., and humans can change clothes and air con)
  • some endotherms hibernate or aestivate
  • endotherms mainly rely on physiological adaptations - skin, muscles, receptors
19
Q

How organisms cool down

A
  • vasodilation= arterioles dilate near the skin, increases radiation
  • increased sweating= as it evaporates, heat is lost, cools blood below the surface (some organisms sweat glands restricted to less hairy areas)
  • reducing insulation= erector pili muscles relax, causing hair/feathers to lie flat to the skin, avoiding trapping an insulating layer
  • some endotherms in hot climates have anatomical adaptations= to maximise sa:vol ratio, e.g. large ears, wrinkly skin, pale fur
20
Q

Ways organisms warm up

A
  • vasoconstriction= arterioles near skin constrict, little radiation occurs
  • decreased sweating= reduce cooling by evaporation
  • raising body hair/feathers= erector pili muscles contract, trapping an insulating layer
  • shivering= rapid, involuntary contracting and relaxing, metabolic heat warms up body
21
Q

anatomical adaptations (of endotherms)

A
  • adaptations to minimise sa:vol e.g. small ears
  • Thick layer of insulating fat e.g. blubber
  • hibernation
22
Q

Examples of adaptations of polar bears

A
  • small ears and fur on feet to insulate from ice
  • fur traps an insulating layer
  • skin under fur is black to increase absorption of warming radiation
  • thick layers of fat under skin
  • dig dens to insulate
23
Q

What is the heat loss centre

A
  • activated when temperature of blood flowing through the hypothalamus increases
  • sends impulses through autonomic motor neurons to effectors in skin and muscles
  • triggers responses that lower core temperature
24
Q

What is the heat gain centre

A
  • activated when the temperature of the blood flowing through the hypothalamus decreases
    -sends impulses through the autonomic nervous system to effectors in skin and muscles that trigger responses to raise core temperature

Biology module 5 (4 decks)

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