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A2 Biology Unit 4 > Section 1- Communication And Homeostasis > Flashcards

Section 1- Communication And Homeostasis Flashcards

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1
Q

Define Cell Signalling

A

Communication between cells

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2
Q

Give two examples of Cell Signalling

A

Neuronal- transport action potentials through neurones and across synapses
Hormonal- transport signals via the blood

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3
Q

Define Negative Feedback

A

A process which any change in a parameter brings about the reversal of the change, so the parameter remains constant

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4
Q

Define Positive Feedback

A

A process in which any change in a parameter brings about an increase in that change

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5
Q

Define Homeostasis

A

The maintenance of a constant internal environment

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6
Q

Explain the Principle Of Homeostasis

A

Any change is detected by receptors, the communication system transmits a message from the receptor to the effector and, through negative feedback, the effectors revers the change

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7
Q

How do ectotherms maintain a constant core body temperature, physiologically and behaviourally (include examples)

A

Physiologically - Horned lizard expands its ribcage and the frilled lizard uses its frill to expand its surface area to absorb more heat

Behaviourally - Snakes expose their body to the sun so more heat is absorbed.
Locusts orientate their body towards the sun to expose a larger surface area so more heat is absorbed

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8
Q

Why do we need communication systems in multicellular organisms ?

A

Organisms need to respond to external stimuli (e.g temperature)
Coordinate different organs

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9
Q

How do endotherms maintain a core body temperature, physiologically

A

Sweat Glands - secrete sweat when hot, water evaporates using heat from the blood removing this excess heat
Lungs/nose/mouth - when hot pant to increase water evaporation from the lungs, tongue and moist surfaces
Hairs On Skin - hairs lie flat when hot providing little insulation, heat can be lost by convection

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10
Q

Define stimulus

A

Any change in internal and external environment

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11
Q

Why do organism need to respond to stimuli

A

To increase their chances of survival

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12
Q

What is the role of a receptor

A

To detect stimuli

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13
Q

Give two types of cell that can act as effectors

A

Muscle cells

Cells in glands

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14
Q

What is the function of a sensory neurone

A

To transmit nerve impulses from receptors to the central nervous system (CNS)

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15
Q

What is the function of a motor neurone

A

To transmit nerve impulses from CNS to effectors

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16
Q

Give three structural differences between a sensory neurone and a motor neurone

A
  • Dendrites in sensory neurone are further away from the cell body than they are in the motor neurone
  • Axon in the sensory neurone are shorter than they are in the motor neurone
  • Sensory neurones have dendrons, motor neurones do not
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17
Q

Describe the pathway of nervous communication from stimulus to response

A

Receptor cell detects stimuli
Sensory neurones transmit electrical impulses from receptors to CNS
CNS processes information and sends impulses along motor neurone to effector

18
Q

Why are sensory receptors described as a transducers

A

Convert energy of stimulus into electrical energy

19
Q

How is a generator potential produced

A

Stimulus detected
Cell membrane excited
More permeable (more ions to move)
Alter potential across cell membrane

20
Q

Which two proteins in a neurone’s cell membrane are responsible for creating and maintaining resting membrane potential

A

Sodium- Potassium pumps

Potassium ion channels

21
Q

Give three types of cell that have receptors for neurotransmitters

A
  • Neurone
  • Muscle
  • Gland
22
Q

Explain how waves of depolarisation are produced

A

During an action potential

  • some sodium ions that enter neurone diffuse sideways
  • sodium ion channels in next region open
  • sodium ions diffuse into that part
  • causes wave of depolarisation
23
Q

How does the conduction along the myelinated neurone differ compared to conduction along the non-myelinated neurone

A
  • in myelinated neurone the action potentials happen in the node of ranvier
  • non-myelinated neurone action potential happens in whole length of axon
  • conduction in myelinated happens quicker
24
Q

Describe the structure of a myelinated neurone

A
  • myelin sheath: made up of Schwann cell wrapped around axon
  • between Schwann cells tiny patches called nodes of Ranvier
  • sodium ions concentrated at NoR
25
Q

Give two factors other than myelination, that affect the conduction of action potentials

A

Temperature and Axon diameter

26
Q

Give three types of cells that have receptors for neurotransmitters

A

Neurone
Muscle
Gland

27
Q

Explain the purpose of synaptic divergence

A

Information from one neurone can be dispersed to many regions of the body

28
Q

Explain the purpose of synaptic convergence

A

Information from many neurones can be amplified

29
Q

Explain why impulses are unidirectional

A

Neurotransmitters are only released from pre synaptic neurones and receptors are only on postsynaptic membranes.
Neurotransmitter can’t activate an action potential back along pre-synaptic membrane

30
Q

Explain how an action potential may be more likely as a result of spatial summation

A

Where two or more pre-synaptic neurones release their neurotransmitters at the same time onto same postsynaptic membrane, the combined amount may be able to reach the threshold and induce an action potential

31
Q

Explain how an action potential may be more likely as a result of temporal summation

A

When two of more nerve impulse arrive in quick succession from same pre-synaptic neurone, more neurotransmitters released into synaptic cleft.
Action potential more likely

32
Q

What is an endocrine gland

A

A group of cells that is specialised to secret hormones

33
Q

Give two types of stimuli that trigger hormone secretion

A

Change of concentration of a specific function

Electrical impulses

34
Q

Why doesn’t a hormone affect every cell in the body

A

Each hormone will only bind to specific receptors

35
Q

How does the endocrine gland differ from exocrine gland

A

Endocrine secret hormones

Exocrine secrete chemicals(enzymes)

36
Q

Give two examples of substances secreted by exocrine gland

A

Sweat

Enzymes

37
Q

What is the name of the second messenger produced when adrenaline binds to liver cell

A

Cyclic AMP

38
Q

How does the body respond to a rise in blood glucose

A
  • Insulin secreted from the Islets Of Langerhans
  • Binds to specific receptors to increase permeability of cell membrane to glucose
  • activates enzymes
  • glycogenesis happens
  • Liver cells store glycogen in cytoplasm
  • increase rate of respiration
39
Q

How does the body respond to a fall in blood glucose

A
  • Glucagon secreted by Islets Of Langerhans
  • Activates enzymes
  • glycogenolysis takes place
  • glycagon promotes formation of glucose from glycerol and amino acids
  • Decrease rate of respiration
40
Q

Hormonal control of heart rate includes :

A
  • organism threatened
  • adrenal glands release adrenaline
  • adrenaline binds to heart receptors
  • cardiac muscle contracts more frequently
  • heart rate increases
41
Q

Body has High Blood Pressure
High Blood Oxygen Content
High pH
Low Carbon Dioxide Content

A
  • Baroreceptors (Pressure)/Chemoreceptors (Chemical) detect
  • Send impulses to cardiovascular centre
  • parasympathetic pathway
  • secrete acetylcholine
  • binds to receptors on SAN
  • Heart Rate decreases
42
Q

Body has Low Blood Pressure
Low Blood Oxygen Content
Low pH
High Carbon Dioxide Content

A
  • Baroreceptors (Pressure)/Chemoreceptors (Chemical) detect
  • Send impulses to cardiovascular centre
  • sympathetic pathway
  • secrete noradrenaline
  • binds to receptors on SAN
  • Heart Rate increases

A2 Biology Unit 4 (4 decks)

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