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OCR Biology Paper 1 > 5.5 - Animal Responses > Flashcards

5.5 - Animal Responses Flashcards

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1
Q

State the difference between the central nervous system and peripheral nervous system

A

CNS is the brain and spinal cord
PNS is all other neurones

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2
Q

What is the role of the somatic nervous system?

A
  • Conscious control of actions
  • i.e. voluntary responses
  • e.g. throwing a ball, walking
  • Carries nerve impulses to skeletal muscles
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3
Q

What is the role of the autonomic nervous system?

A
  • Subconscious control
  • i.e. involuntary reactions
  • e.g. pupil dilation, heart beat, food digestion
  • Carries nerve impulses to glands, smooth muscle or cardiac muscles
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4
Q

Why are autonomic responses necessary?

A
  • Frees up conscious areas of brain
  • Allows multiple vital tasks to be performed without thinking
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5
Q

Why can many autonomic functions also be controlled consciously?

A
  • Enables response to certain situations / environments
  • e.g. breathing can be controlled
  • A person can hold their breath underwater
  • Because not possible to breathe normally in this environment
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6
Q

Outline the role of the cerebrum

A

Controls voluntary actions
- e.g. learning, memory, conscious thought, walking

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7
Q

Outline the role of the cerebellum

A

Controls unconscious functions
- e.g. posture, balance, non-voluntary movement

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8
Q

Outline the role of the Medulla oblongata

A

Autonomic control
- e.g. heart rate, breathing rate

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9
Q

Outline the role of the hypothalamus

A

Regulatory centre for temperature (thermoregulation) and water balance (osmoregulation)

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10
Q

Outline the role of pituitary gland

A
  • Anterior pituitary produces hormones
  • e.g. FSH
  • Posterior pituitary stores and releases hormones produced by hypothalamus
  • e.g. ADH
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11
Q

Which part of the brain is responsible for the coordination of the autonomic control of heart rate?

A

Medulla oblongata

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12
Q

Which part of the brain is responsible for osmoregulation by the kidney?

A

Hypothalamus and pituitary gland

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13
Q

Which part of the brain is responsible for the coordination of the muscles involved in walking in an adult?

A

Cerebrum (conscious muscle movement) and cerebellum (balance and coordination)

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14
Q

A stroke is when cells in part of the brain die. Explain how the following effects of a stroke are
caused:
- Problems with coordination of movement
- Loss of memory and speech
- Paralysis of the body below the neck

A

Problems with coordination of movement
- Damage to cerebellum

Loss of memory and speech
- Damage to cerebrum

Paralysis of the body below the neck
- Damage to medulla oblongata and/or cerebrum

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15
Q

What type of actions are not processed by the brain?

A

Reflex actions

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16
Q

Describe the pathway of a reflex arc

A

Receptor → Sensory neurone → Relay neurone → Motor neurone → Effector

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17
Q

Describe the actions that take place when you touch a sharp object

A
  • Pressure receptors in skin detect change in pressure
  • Sensory neurone passes nerve impulses to spinal cord
  • Relay neurone passes impulses across the spinal cord
  • Motor neurone passes impulses to the effector (a muscle)
  • Muscle contracts
  • Body part is removed from sharp object
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18
Q

What is the purpose of the knee-jerk reflex?

A

Helps body maintain posture and balance

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19
Q

What does the absence of a knee-jerk reflex indicate?

A

Nerve damage in spinal cord

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20
Q

What type of reflex in the blinking reflex?

A

Cranial reflex
- Occurs in brain
- Involuntary response

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21
Q

What is the purpose of the blinking reflex?

A

Prevents objects entering or damaging eye

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22
Q

Explain how the blinking reflex occurs

A
  • Cornea of eye irritated
  • Stimulus triggers impulse along sensory neurone
  • Impulses passes along relay neurone in lower brain stem
  • Impulses sent along motor neurone to muscles in eyelids
  • Causes eyelids to close
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23
Q

Explain how a reflex action can improve an organism’s chance of survival

A

Reflex arc does not include the brain
- Involuntary response
- Prevents brain being overloaded
Decreases time taken for body to react to harmful situation
Does not have to be learnt
- Provides immediate protection

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24
Q

Define coordinated response

A
  • Nervous and endocrine systems working together
  • Detect and respond appropriately to stimuli
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25
Q

Describe the fight or flight response

A
  • Coordinated response in mammals
  • Body reacts to potentially dangerous situations
  • Prepares body to either run or fight
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26
Q

Which part of the nervous system detects potential threats?

A

Autonomic nervous system

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27
Q

Which part of the nervous system is stimulated in the fight or flight response?

A

Sympathetic nervous system

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28
Q

Which hormones are involved in the fight or flight response?

A
  • Adrenaline
  • Noradrenaline
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29
Q

Explain the effect of adrenaline on liver cells

A
  • Triggers increase in glycogenolysis
  • Makes more glucose available for respiration
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30
Q

Where are adrenaline and noradrenaline secreted from?

A

Adrenal medulla

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31
Q

Why can’t adrenaline cross plasma membranes?

A

Hydrophilic molecule
- Not lipid soluble

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32
Q

Describe the function of adenylyl cyclase

A
  • Membrane-bound enzyme
  • Found on inside of plasma membrane
  • Associated with adrenaline receptor proteins
  • Converts ATP to cyclic AMP (cAMP)
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33
Q

Describe the function of cAMP

A
  • Acts as second messenger
  • Activates other enzymes in the cell
34
Q

How are enzymes activated?

A
  • By phosphorylation
  • By changing the tertiary structure
35
Q

Outline the second messenger model of adrenaline action on target cells

A
  • Adrenaline binds to receptor
  • Receptor complementary to adrenaline
  • Adrenaline acts as first messenger
  • Adenylyl cyclase enzyme activated
  • ATP converted to cAMP
  • cAMP acts as second messenger
  • cAMP activates protein kinase enzymes
  • Protein kinases activate enzymes to carry out response
36
Q

Suggest how the adrenaline molecule can cause different effects in different target tissues

A
  • Different tissues have different receptors
  • Binding of adrenaline to receptors causes cAMP concentration to increase or decrease
  • Second messenger may be different in different cells
  • cAMP or other second messenger activates different enzymes
37
Q

Explain how the second messenger model enables a small number of adrenaline molecules to
rapidly cause large effects

A
  • One adrenaline molecule causes activation of many other molecules
  • Multiplying effect repeated at every step
38
Q

Explain how the nervous system and endocrine system work together to enable the body to
respond to danger

A
  • Danger detected by the autonomic nervous system
  • Hypothalamus triggers sympathetic nervous system
  • Nervous impulse triggers release of hormones from adrenal medulla
  • Adrenaline causes glycogenolysis in liver cells
  • Increased blood glucose used for respiration
  • Creates ATP for muscle contraction
  • Pituitary gland stimulates the adrenal-cortical system
  • Hormones release from adrenal cortex
39
Q

Which part of the nervous system is responsible for controlling the heart rate?

A

Autonomic

40
Q

Which section of the brain is responsible for controlling the heart rate

A
  • Cardiovascular centre
  • In medulla oblongata
41
Q

How does the medulla oblongata communicate with the heart?

A

Sympathetic nervous system
- Impulses transmitted through accelerator nerve
- To sinoatrial node (SAN)
- Increases heart rate

Parasympathetic nervous system
- Impulses transmitted through vagus nerve
- To sinoatrial node (SAN)
- Decreases heart rate

42
Q

What is the role of baroreceptors?

A

Detect change in blood pressure

43
Q

Where are baroreceptors located?

A
  • Aorta
  • Vena cava
  • Carotid artery
44
Q

What is the role of chemoreceptors?

A
  • Detect change in chemicals in blood
  • e.g. carbon dioxide
  • Sensitive to pH level
45
Q

Where are chemoreceptors located?

A
  • Aorta
  • Carotid artery
  • Medulla oblongata
46
Q

Why does CO2 decrease the pH of blood?

A
  • Carbon dioxide reacts with water
  • Forms carbonic acid (H2CO3)
  • Carbonic acid dissociates to form hydrogencarbonate ions and hydrogen ions
  • H+ ions reduce pH
47
Q

Explain what could cause a decrease in blood pH

A
  • Increase in aerobic respiration
  • Produces more carbon dioxide
48
Q

Outline why exercising causes heart rate to increase

A

Increased metabolic activity
- More CO2 produced by aerobic respiration
- Blood pH lowered
- Detected by chemoreceptors in medulla oblongata and aorta
- Increases frequency of impulses to SAN
- Sent via sympathetic nervous system
- SAN increases heart rate
- Increases rate of depolarisation
- Increased blood flow removes CO2 faster
- CO2 level returns to normal
- Blood pH increases

49
Q

Outline how an increase in blood pressure causes heart rate to decrease

A
  • Baroreceptors in aorta and carotid artery detect increase in blood pressure
  • Send impulses to medulla oblongata
  • Medulla oblongata sends impulses to SAN
  • Sent via parasympathetic nervous system
  • SAN decreases heart rate
  • Decreases rate of depolarisation
50
Q

Which hormones cause an increase in heart rate?

A
  • Adrenaline
  • Noradrenaline
51
Q

Which cells does adrenaline target to increase heart rate?

A

SAN in heart

52
Q

Outline the hormonal and nervous mechanisms involved in the control of heart rate

A
  • Adrenaline increases heart rate
  • Targets cells in SAN
  • Cardiovascular centre in medulla oblongata
  • Connected by nerves to SAN
  • Controls frequency of depolarisation
  • Parasympathetic (vagus) nerve decreases heart rate
  • Sympathetic (accelerator) nerve increases heart rate
  • High blood pressure detected by baroreceptors
  • Receptors in aorta, vena cava, carotid arteries
  • Low blood pH detected by chemoreceptors
  • Receptors in aorta, carotid arteries, medulla oblongata
53
Q

Outline the differences in the ways in which mammalian and plant hormones operate

A

Mammals - made in endocrine glands
Plants - made in plant tissues
Mammals - move in blood
Plants - move from cell to cell in xylem
Mammals - act on specific tissues
Plants - act on most tissues and in cells where
produced
Mammals - act more rapidly
Plants - act more slowly

54
Q

What is the role of muscles?

A
  • Provide forces that move animals’ bodies
  • Only exert force when they contract (not when they relax and lengthen)
  • Only cause movement in one direction
55
Q

Online the three types of muscle found in the body

A

Skeletal muscle
- Responsible for movement

Cardiac muscle
- Found only in the heart

Smooth (involuntary) muscle
- Found in walls of hollow organs
- e.g. stomach, bladder
- Found in walls of blood vessels and digestive tract

56
Q

Describe the structure of skeletal muscle

A
  • Attaches to bone
  • Causes movement of animal bodies
  • Muscle fibres are multi-nucleated
  • Myofibrils consist of sarcomeres (light and dark bands) giving striped appearance
  • Contain specialised sarcoplasmic reticulum (store of Ca2+ ions)
57
Q

Which proteins make up the myofibrils?

A
  • Actin
  • Myosin
58
Q

What causes the presence of the dark band (A-band)?

A

Myosin

59
Q

What causes the presence of the light band (I-band)?

A

Actin only
- No myosin present

60
Q

What is the H zone?

A
  • Region where only myosin is present
  • No actin
61
Q

What happens to the size of the sacromere when a muscle contracts?

A

shortens

62
Q

What happens to the size of the I-band when a muscle contracts?

A

shortens

63
Q

What happens to the size of the A-band when a muscle contracts?

A

stays the same

64
Q

What happens to the size of the H-zone when a muscle contracts?

A

shortens

65
Q

What is the sarcoplasm?

A

Muscle-fibre cytoplasm

66
Q

What is the sarcolemma?

A

Plasma membrane surrounding muscle fibre

67
Q

What is the role of the sarcoplasmic reticulum?

A

Contains calcium ions

68
Q

What are T-tubules?

A

Inwards folds of sarcolemma

69
Q

What is the role of T-tubules?

A
  • Help spread action potential through sarcoplasm
  • Allows depolarisation of sarcoplasmic reticulum
70
Q

What is the role of troponin and tropomyosin?

A

Block binding sites on actin when muscle is relaxed

71
Q

Explain how an action potential leads to the release of Ca2+ from the sarcoplasmic reticulum

A
  • Action potential arrives at end of motor neurone
  • Neurotransmitter (ACh) released causing action potential across sarcolemma
  • Action potential spreads along T-tubules
  • Action potential causes depolarisation of sarcoplasmic reticulum
  • Calcium ions released from sarcoplasmic reticulum
72
Q

Explain the sliding filament model for skeletal muscle contraction

A
  • Calcium ions released from sarcoplasmic reticulum bind to troponin
  • Moves tropomyosin so binding sites on actin revealed
  • Myosin heads bind to sites on actin to form cross-bridges (1)
  • ADP molecule released from myosin head
  • Myosin heads move actin filaments in a ‘power stroke’ (2)
  • Z-lines pulled towards each other, sarcomeres shortened
  • Binding of new ATP causes release of myosin head from actin (3)
  • Hydrolysis of ATP to ADP and Pi causes myosin heads to reset (4)
  • Cycle repeated
73
Q

What is the role of calcium ions in muscle contraction?

A
  • Calcium ions released from sarcoplasmic reticulum bind to troponin
  • Moves tropomyosin so myosin-binding sites on actin are exposed
  • Myosin heads can now bind to binding sites on actin
74
Q

Explain why a reduction in Ca2+ availability leads to reduced muscle contraction force

A
  • Fewer Ca2+ ions bind to troponin
  • Fewer troponin proteins change shape
  • Fewer tropomyosin proteins move aside
  • Fewer binding sites on actin available
  • Fewer actin-myosin cross bridges form
  • Power stroke reduced
  • Actin filaments pulled past myosin with less force
75
Q

Explain the role of ATP in the contraction of skeletal muscle

A
  • ATP binds to myosin heads
  • ATP binding causes cross bridges between myosin and actin to break
  • ATP hydrolysed to ADP + Pi, causing myosin heads to change angle
  • Myosin heads attach to binding sites on actin filament further along sarcomere
  • ADP + Pi released and myosin heads pull actin filament along (“power stroke”)
76
Q

Outline the function of myosin and actin in muscle contraction

A
  • Myosin binds to actin forming cross-bridges
  • Sliding of actin and myosin filaments shortens sarcomere
  • ATP used to break cross-bridges
  • Myosin heads re-set
  • Contraction ceases when myosin head detaches from the actin filament
77
Q

How is ATP supplied to muscle tissue?

A
  • Aerobic respiration
  • Anaerobic respiration
  • Creatine phosphate
78
Q

Define phosphorylation

A

Addition of a phosphate group
- e.g. ADP + Pi → ATP

79
Q

Explain how ATP is generated using creatine phosphate

A
  • Creatine phosphate stored in muscle
  • Acts as reserve supply of phosphate
  • Available to combine with ADP to form ATP
80
Q

What is the advantage of storing creatine phosphate in muscle tissue?

A
  • Generates ATP rapidly
  • Used for short burst of vigorous exercise
81
Q

What is the disadvantage of creatine phosphate as an energy source?

A
  • Store of phosphate used up quickly
  • Must be replenished using ATP when muscle relaxed

OCR Biology Paper 1 (20 decks)

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