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Biology > Reflexes - Module 5 > Flashcards

Reflexes - Module 5 Flashcards

1
Q

What is a reflex action?

A

Involuntary response to a sensory stimulus

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2
Q

What is a reflex arc?

A

Pathway of neurones involved in reflex action

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3
Q

What is the 4 step pathway of a reflex arc?

A
  1. Receptor - detects stimuli and starts action potential in sensory neurone
  2. Sensory neurone - carries impulse to spinal cord
  3. Relay neurone - connects sensory to motor neurone in spinal cord/ brain
  4. Monitor neurone - carries impulse to effector to carry out response
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4
Q

What is a withdrawal reflex?

A

Before the Brian realises, muscles have pulled away form danger

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5
Q

Describe the structure of the spinal cord

A

It is a column of nervous tissues protected by spine
Pairs of neurones emerge at intervals

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6
Q

What are the 4 importance features of reflexes for survival?

A
  1. Involuntary responses - doesn’t overload brain with response that is always the same
  2. Don’t have to be learnt - present from birth and provide immediate protection
  3. Extremely fast - reflex arc is short 1 or 2 synapses
  4. Many reflexes are every day actions like balance
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7
Q

How is the blink reaction used by doctors?

A

It is used to determine weather the lower brain stem is still functioning and subsequently weather someone is Brian dead

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8
Q

When does the blinking relax occur?

A

When the Cornea is stimulated and irritated

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9
Q

What is the purpose of the blink reaction?

A

To stop the damage of the Cornea

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10
Q

On what two other occasions do blink reflexes occur?

A
  1. Loud sound
  2. Very bright light
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11
Q

What is the optical reflex?

A

The blink reaction to very bright light to protect lens and retina

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12
Q

Why is the blink reaction a cranial reflex?

A

It occurs in the brain not the spinal cord

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13
Q

Describe the blinking reflex pathway

A
  1. Stimulus - something touches the cornea
  2. Receptors - sensory nerve endings detect stimulus and send impulse along sensory neurone
  3. CNS - impulse is received from sensory neurone and passed from relay neurone to motor neurone
  4. Effector - motor neurone sends impulse to effectors, in this case the muscle causing the eye to close
  5. The response to close the eye is generated
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14
Q

Describe the knee jerk reflex

A
  1. Stimulus - the quadricep muscle is stretched
  2. Receptors - stretch receipts detect stimulus and send a nerve impulse down sensory neurone
  3. CNS - sensory neurone communicates directly with motor neurone in spinal cord
  4. Effectors - motor neurone carries impulse to quadriceps muscle
  5. Response is quadricep muscle contracts so the lower leg moves forward quickly
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15
Q

What is the function of the knee jerk reflex?

A

Works to quickly straighten leg if body detects stretch in quadriceps maintains posture and balance

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16
Q

What is the 3 types of muscle?

A

Skeletal
Involuntary
Cardiac

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17
Q

What is the role of skeletal muscle?

A

Movement of the body

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18
Q

Is skeletal muscle conscious or involuntary?

A

Conscious

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19
Q

What is the speed and length of skeletal muscle contractions?

A

Rapid and short

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20
Q

What is the arrangement of fibres in skeletal muscle?

A

Striated and regularly arranged so muscle contracts in once direction

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21
Q

Are skeletal muscle cells uninucleate or multinucleate?

A

Multinucleated

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22
Q

Is cardiac muscle involuntary or conscious?

A

Involuntary

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23
Q

What is the structure of cardiac muscle?

A

Specialised striated and cells branch and interconnect

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24
Q

What is the speed and length of cardiac muscle contractions?

A

Intermediate speed and length

25
Q

Are cardiac muscle fibres multinucleated or uninucleated?

A

Uninucleate

26
Q

What is the structure of involuntary muscles?

A

Non striated and have no regular arrangement

27
Q

What is the speed and length of contractions in involuntary muscles?

A

Long and slow contractions

28
Q

Are involuntary muscle fibres uninucleate or multunucleate?

A

Uninucleate

29
Q

What is sarcolemma?

A

The membrane that encloses the muscle fibre

30
Q

Why do skeletal muscles have multiple nuclei?

A

They are much longer than normal cells and are formed from lots of embryonic muscle cells fusing together

31
Q

What is the sarcoplasm?

A

Shared cytoplasm within muscle fibres

32
Q

What are T-tubules?

A

Parts of the sarcolemma that fold inwards to spread electrical impulses evenly across sarcoplasm

33
Q

What is the role of T-tubules?

A

To ensure electrical impulses spread across muscle fibres evenly

34
Q

Why to muscle fibres have lots of mitochondria?

A

To provide ATP for muscle contraction

35
Q

What is special about the endoplasmic reticulum in muscle fibres?

A

They have the sarcoplasmic reticulum which is a modified version that contains calcium ions

36
Q

What are myofibrils?

A

Long cylindrical organelles specialised for contraction

37
Q

Why are myofibrils aligned parallel?

A

To provide maximum force when they contracts as alone they have no power

38
Q

What are the two protein filaments myofibrils consist of?

A
  1. Actin - thinner filament
  2. Myosin - thicker filament
39
Q

Why do myofibrils have a striped appearance?

A

Light and dark bands - the light I bands are where it is just actin and no overlap, and dark A-bands of just myosin present

40
Q

What is a Z line?

A

Line at the centre of each light band

41
Q

What is a sacromere?

A

Distance between adjacent z-lines

42
Q

What is a H zone?

A

Where only myosin is present so it is slightly lighter than the areas where both overlap in the dark bands of myofibrils

43
Q

Describe the structure of myosin?

A

Globular heads which are hinged
Head has binding site for ATP and actin
Lots of myosin tails form the filament

44
Q

What binding sites are present on actin?

A

Actin-myosin binding sites

45
Q

What proteins block the actin-myosin binding sites on actin?

A

TROPOMYOSIN is held in place by TROPONIN

46
Q

What bonds are formed when a muscle contracts?

A

Actin-myosin cross bridges

47
Q

What triggers a muscle contraction?

A

When action potential arrives at a neuromuscular junction

48
Q

What is a neuromuscular junction?

A

Point where a motor-neurone joins the muscle fibre

49
Q

What is a motor unit?

A

All of the muscle fibres supplied by a single motor neurone

50
Q

When the action potential reaches the sarcoplasmic reticulum what is stimulated?

A

Release of calcium ions into sarcoplasm

51
Q

What do calcium ions do to allow muscles contraction to occur?

A

Bind to TROPONIN causing it to change shape and move TROPOMYOSIN away from binding sites on actin allowing actin-myosin bridges to form

52
Q

What happens to ADP once actin is bound to myosin?

A

ADP detaches and ATP molecule binds causing the actin and myosin to detach

53
Q

What enzyme do calcium ions activate?

A

ATPase, which hydrolyses ATP to ADP + Pi which releases energy

54
Q

What are the 3 main sources of ATP in muscle contraction?

A

Aerobic respiration
Anaerobic respiration
Creating phosphate

55
Q

What is creating phosphate?

A

Supply of phosphate readily available for ADP to bind to to make ATP

56
Q

Describe the sliding filament model?

A

Myosin pulls actin towards the centre of the sarcomere, causing the light bands to become narrower, z lines come close together and H zone becomes narrower

57
Q

How does myosin pull actin across the filament?

A

It’s heads which have the binding site will change angle on its hinges

58
Q

What does Myosin use to return its globular head to its original position?

A

ATP

Biology (26 decks)

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