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Biology > 5:1:1 Communication and Homeostasis > Flashcards

5:1:1 Communication and Homeostasis Flashcards

1
Q

Define homeostasis

A

The body’s responses to changes in their internal and external environment in order to maintain optimal conditions for enzyme action and cell function

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2
Q

How is the body’s internal environment controlled

A

Physiological control systems:
- Nervous system
- Endocrine system

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3
Q

What is the nervous system

A
  • Allows us to respond to our surroundings and coordinate and regulate bodily functions
  • Information sent through the nervous system as nerve impulses (electrical signals) through neurones
  • Neurones coordinate the activity of sensory receptors, decision making centres in the central nervous system, and effectors
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4
Q

What does the nervous system consist of

A
  • Central nervous system (CNS): brain, spinal cord
  • Peripheral nervous system (PNS): all nerves in body
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5
Q

What is the endocrine system

A
  • System which has hormone producing glands (endocrine glands), allowing these chemicals to transmit information within the organisms
  • Hormones can alter activity of target organs, and used to control functions that don’t need instant responses
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6
Q

Label diagram of the endocrine system in humans

A
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7
Q

What are the main factors that need controlling in organisms

A
  • Temperature (vital for enzyme activity)
  • pH (vital for enzyme activity)
  • Blood glucose concentration
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8
Q

Why does pH have to be controlled

A
  • Enzymes have optimum pH’s, and can be denatured at pH extremes
  • Denaturing occurs when the H and ionic bonds holding the tertiary protein structure break which alters the shape of the active site
  • Enzyme-substrate complex can’t form
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9
Q

Why does blood glucose concentration have to be controlled

A
  • Amount of glucose present affects water potential of the blood and the availability of respiratory substrates for cells
  • Usual glucose concentration for humans is 90mg/100cm^3
  • Glucose is essential for cellular respiration
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10
Q

Why does the opening/closing of stomata have to be controlled

A
  • Plants require a constant supply of CO2, and well as controlling the water levels in the plant
  • Stomata respond to internal and external stimuli (e.g. darkness/water stress)
  • Regulation of stomata balances the need for CO2 uptake and water loss
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11
Q

What are negative feedback loops

A
  • A majority if homeostatic control mechanisms use negative feedback to maintain homeostatic balance
  • The loops involve:
  • A receptor to detect a stimulus
  • A coordination system (nervous/endocrine) to transfer the information
  • An effector (muscles/glands) to carry out the response
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12
Q

What is the outcome of a negative feedback loop

A
  • The stimulus is continuously monitored
  • If there is an increase in the factor, the body responds to make it decrease
  • If there is a decrease in the factor, the body responds to make the factor increase
  • They reduce the initial effect of the stimulus
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13
Q

What are the two corrective methods used by negative feedback loops to control homeostasis

A
  • One for when the factor becomes too high
  • One for when the factor becomes too low
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14
Q

What are positive feedback loops

A
  • Where the original stimulus produces a response that causes the factor to deviate even more from the normal range
  • They enhance the effect of the original stimulus
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15
Q

Describe how positive feedback loops work (e.g. bone repair)

A
  • Osteoblasts secrete a hormone called osteocalcin in an inactive form
  • The osteoclasts secrete acid which lowers the pH and the acidic conditions to cause the inactive form of osteocalcin to the active one
  • The active from of osteocalcin binds to a receptor on beta cells in the pancreas which stimulates then to release insulin
  • Osteoblasts have insulin receptors which release more osteocalcin when stimulated
  • The osteoblasts cells enhance the effect of the original stimulus (insulin)
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16
Q

What is cell signalling and why is it important

A
  • Cell signalling is the process by which cells communicate with each other
  • It is important as it allows multicellular organisms to control and coordinate their bodies to respond to their environments
17
Q

What occurs in cell signalling pathways

A
  • A stimulus is received by a receptor cell
  • The stimulus is converted to a signal (chemical) that can be passed on (process called transduction)
  • Signal is transmitted to a target cell (effector) that detects it
  • An appropriate response is made
18
Q

What are the two categories of cell signalling pathways

A
  • Paracrine signalling (signalling between close together cells)
  • Endocrine signalling (signalling between far apart cells using hormones as the signalling molecules)
19
Q

How are cell membranes involved in cell signalling

A
  • Transmission of messages in cell signalling pathways requires crossing barriers (cell membranes)
  • The membranes control what moves in and out of the cell, therefore signalling molecules are very small for easy transport across the membrane
  • Receptor molecules on/in the cell surface membrane are proteins or glycoproteins
  • Signalling molecules bind to the receptor molecule cause in specific changes in the receiving cell
20
Q

What is thermoregulation and why is it important

A
  • Thermoregulation is the control of internal body temperature
  • It’s control is vital for enzyme activity
  • As well as rate of reactions
21
Q

What are endotherms

A

Animals that posses physiological mechanisms to control their internal body temperature (using heat generated within tissue) (e.g. mammals and birds)

22
Q

What are ectotherms

A

Animals that rely on behavioural adaptations to ensure their internal body temperature doesn’t get too high or low (absorbing heat from their environment) (e.g. reptiles and amphibians)

23
Q

How does thermoregulation work in endotherms

A
  • They detect external temperatures via peripheral receptors (for both heat and cold)
  • These receptors communicate with the hypothalamus to bring about a physiological response
  • The hypothalamus can also regulate body temperature by monitoring the temperature of the blood flowing through it and initiating homeostatic responses when it’s too low or high
24
Q

What are examples of endotherms cooling mechanisms

A
  • Vasodilation
  • Sweating
  • Flattening of hairs
25
Q

What are examples of endotherms warming mechanisms

A
  • Vasoconstriction
  • Boosting metabolic rate
  • Shivering
  • Erection of hairs
26
Q

How does vasodilation work as a cooling mechanism

A
  • Heat exchange occurs at the bodies surface
  • To increase heat loss, the capillaries are supplied with a greater volume of blood (carries heat energy) which loses heat via radiation
  • During vasodilation the muscles in arteriole walls relax, causing the arterioles near the skin to dilate and allow more blood to flow
27
Q

How does sweating work as a cooling mechanism

A
  • Sweat is secreted by sweat glands
  • The sweat cools the skin by evaporation which uses heat energy from the body to convert the liquid water into water vapour
  • Sweating is less effective in humid environments
28
Q

How does the flattening of hairs work as a cooling mechanism

A
  • Hair erector muscles in the skin relax, causing the hairs to lie flat
  • This stops then from forming an insulating layer by trapping air, and instead allows air to circulate over the skin so heat can leave by radiation
29
Q

How does vasoconstriction work as warming mechanism

A
  • Supplying the capillaries with less blood volume minimises heat loss by radiation
  • The muscles in the arteriole walls contract, causing constrictions which reduced the blood flow
  • Blood is instead diverted through shunt vessels further down in the skin to preserve heat
30
Q

How does boosting metabolic rate work as a warming mechanism

A
  • Most of the metabolic reactions in the body are exothermic and provide warmth to the body
  • The hormone thyroxine is released in cold environments, where is increases the basal metabolic rate, increasing heat production
31
Q

How does shivering work as a warming mechanism

A
  • Reflex action in response to the decrease in temperature
  • The muscles are the effectors, and they contract rapidly in a regular manner
  • The metabolic reactions required to power this shivering generate warmth for the body
32
Q

How does the erection of hairs work as a warming mechanism

A
  • Hair erector muscles in the skin contract, causing the hairs to stand on end
  • This forms an insulating layer over the skin by trapping air between the hairs, stopping heat being lost via radiation
33
Q

Why do aquatic ectotherms have little difficulty thermoregulating

A

Due to the water temperature varying much less than land temperatures, due to the high specific heat capacity of water

34
Q

How do ectotherms heat up

A

Seek out the sun or warm surfaces to bask in until their body temperatures have increased

35
Q

How do ectotherms cool down

A

By seeking shade or water, until their body temperature has decreased

36
Q

What are the disadvantages and advantages of ectotherms thermoregulation mechanisms

A
  • Advantage: they require very little energy, so they would be able to survive better in environments with little food
  • Disadvantage: their behaviour is more restricted by environmental temperatures, so they can’t easily colonise areas that have extreme temperatures

Biology (25 decks)

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