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Module 5 > Animal Responses > Flashcards

Animal Responses Flashcards

1
Q

What is the Nervous system divided into

A

The Central Nervous system (CNS) - Composed of the brain and spinal cord
The Peripheral Nervous system (PNS) - Sensory and motor nerves connecting the sensory receptors and effectors to the CNS

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2
Q

What is the PNS divided into

A

Motor system (CNS to muscles and glands)
Sensory system (sensory organs to CNS)s

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3
Q

What is the motor system divided into

A

Somatic nervous system: Motor neurones under conscious control
Autonomic nervous system: Motor neurones that control the involuntary responses of the body

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4
Q

What is the autonomic nervous system divided into

A

Sympathetic system: Prepares the body for activity ‘Fight or flight’
Parasympathetic system: Conserves energy ‘Rest and digest’

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5
Q

Brain

A

Receives and processes sensory information, initiates responses, stores, memories, generates thoughts and responses

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6
Q

Brain vs spinal cord

A

Brain - relay neurones - non myelinated
Spinal cord - non myelinated and myelinated
=protected by the vertebral column, between each vertebrae, peripheral nerves enter/leave the spinal cord, which carries the ap to and from the rest of the body

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7
Q

Sensory nervous system

A

Sensory fibres that enter the CNS are dendrons of the sensory neurones
-Neurones carry ap from sensory receptors into CNS
-Neurones have cell body in the dorsal root leading into the spinal cord and a short axon which connects to other neurones in the CNS

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8
Q

The Somatic nervous system

A

Motor neurones that conduct ap from the CNS to the effector are under voluntary control
-Skeletal muscles (effector)
-Myelinated
-Always one or more neurone that connects CNS to the effector

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9
Q

The autonomic nervous system

A

-Not voluntary i.e. glands/ cardiac muscles/ smooth muscle in blood vessels/ airways/ walls of the digestive system
-Non-myelinated
-Two neurones involves in connecting the CNS to the effector
-Can be further divided into the parasympathetic system and the sympathetic system

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10
Q

Where are the neurones in the autonomic nervous system connected

A

Small swellings called the ganglia

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11
Q

What does the autonomic system regulate

A

Homeostasis:
Regulates homeostatic mechanisms and regulates the internal environment of the body

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12
Q

Sympathetic system

A

‘Fight or Flight’
-Prepares body for activity
-Noradrenaline
-Many nerves leading out of the CNS to a separate effector
-Short pre-ganglion nerves
-Ganglia outside CNS
-Increases activity
-Most active = stress

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13
Q

Parasympathetic system

A

‘Rest and digest’
-Conserves energy
-Acetylcholine
-Few nerves which divide and lead to different effectors
-Long pre-ganglion nerves
-Ganglia in effector
-Decreases activity
-Most active = sleep

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14
Q

Relationship between the sympathetic system/ parasympathetic system

A

Antagonistic = action of one system opposes the actions of the other
-At rest: Ap passes out at a low frequency and is controlled by subconscious paths in the brain
-Change in internal environment/ stress: leads to changes in the balance of stimulation between the two systems, which leads to an appropriate response

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15
Q

Sympathetic system effects

A

-Increases heart rate
-Dilates pupils
-Increases ventilation rate
-Reduces digestive activity
-Orgasm

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16
Q

parasympathetic system effects

A

-Decreases heart rate
-Constricts pupils
-Reduces ventilation rate
-Increases digestive activity
-Sexual arousal

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17
Q

What are the different lobes in the brain

A

1) Frontal lobe
2) Parietal lobe
3) Occipital lobe
4) Cerebellum
5) Temporal lobe

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18
Q

Frontal lobe

A

Higher brain functions = decision making, planning consciousness

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19
Q

Parietal lobe

A

Orientation, movement, sensation calculation, types of recognition and memory

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20
Q

Occipital lobe

A

Visual cortex involved in processing information from the eyes

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21
Q

Cerebellum

A

Balance / movement

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22
Q

Temporal lobe

A

Processing auditory info/ memory

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23
Q

4 Main parts of the brain

A

1) Cerebrum
2) Cerebellum
3) Hypothalamus and pituitary complex
4) Medulla oblongata

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24
Q

Cerebrum

A

Region of the brain, which controls higher brain functions such as conscious thought; divided into two cerebral hemispheres

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25
Q

Structure of the cerebrum

A

-Divided into two hemispheres connected via major tracts = corpus callosum
-Cerebral cortex: thin layer of nerve cell bodies on the outer part of the cerebrum

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26
Q

What does the higher brain thought include (Cerebrum)

A

-Conscious thought
-Conscious action (ability to override some reflexes)
-Emotional responses
-Intelligence; reasoning; decision making
-Factual memory

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27
Q

The three areas the cerebral cortex is divided into (Cerebrum)

A

1) Sensory areas
2) Association areas
3) Motor areas

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28
Q

Sensory areas (Cerebrum)

A

Receive ap indirectly from SR
-Size of regions allocated to receive input from different receptors related to sensitivity of area inputs are from

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29
Q

Association areas (Cerebrum)

A

Compare sensory inputs with previous experience, interpret what the input means and judge an appropriate response

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30
Q

Motor area (Cerebrum)

A

Ap to various effectors
Size = related to complexity of movement needed in that part of the body
-Left controls right side of body and vice versa

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31
Q

Cerebellum

A

Involved in movement and balance
-Receives info from Sensory receptors: retina; balance organs in the inner ears; spindle fibres in muscles

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32
Q

Cerebellum coordinates the fine control of muscular movement

A

1) Maintaining body balance when riding a bike
2) Judging the position of objects
3) Tensioning muscles to use tools

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33
Q

Control requires learning (Cerebellum)

A

Nervous pathways are learnt
-Complex activity becomes ‘programmed’ in cerebellum

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34
Q

How are the cerebrum and cerebellum connected

A

By the pons

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35
Q

The hypothalamus

A

-Controls homeostatic mechanisms
-Contains own SR
-Acts by negative feedback to maintain a constant environment

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36
Q

How does the hypothalamus detect change

A

1) Changes in the body’s core temperature
2) Sensory input from temperature receptors in the skin

Responses mediated by NS/HS

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37
Q

How does the hypothalamus monitor the WP

A

-Osmoreceptors in the hypothalamus monitor the WP in the blood
-When WP changes = NF
-Responses mediated by HS via the pituitary gland

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38
Q

Pituitary gland

A

Acts in conjunction with the hypothalamus
Consists of two lobes:
1) Posterior lobe
2) Anterior lobe

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39
Q

Posterior lobe

A

Linked to hypothalamus by specialised neurosecretory cells
-Hormones (i.e. ADH) manufactured in the hypothalamus pass down neurosecretory cells and are released into the blood fromthe pituitary gland

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40
Q

Anterior lobe

A

Manufactures OWN hormones released in response to releasing factors produced by the hypothalamus
RF- only need to diffuse a short distance from hypothalamus to pituitary

RF - stimulate the release of other hormones

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41
Q

What do hormones control

A

A range of physiological processes within the body i.e. stress/ growth/ reproduction

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42
Q

Medulla Oblongata

A

Controls non-skeletal muscles (cardiac muscles/ involuntary smooth muscles) by sending out ap through the autonomic NS

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43
Q

What are the centres in the medulla oblongata and what do they regulate

A

1) Cardiac centre = heart rate
2) Vasometer centre = circulation and BP
3) Respiratory centre = Rate /depth of breathing

-Centres receive sensory info and and coordinate vital functions by negative feedback

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44
Q

Reflex action

A

A response that does not involve any processing by the brain (involuntary movement) although the brain is informed
-Innate = not learnt
-Involuntary = prevents overloading of the brain
-Fast = only two synapses involved

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45
Q

What is a reflex arc

A

Receptor and effector are in the same place

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46
Q

Blinking reflex

A

Causes the eyelids to temporarily close to protect the eyes from damage
Cranial reflex: Blinking reflex passes through parts of the brain although the higher thought processes is not involved

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47
Q

How is the blinking reflex stimulated

A

-Sudden bright light
-Loud sounds
-Sudden movement close to the eye

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48
Q

Types of blinking reflex

A

Corneal reflex - used to check if the patients are brain dead as it is a cranial reflex - won’t work if brain is not involved
Optical reflex

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49
Q

Optical reflex

A

Pupils dilate and constrict in response to light so that the retina is not damaged
-Protects the light -sensitive cells in the retina
-Stimulus detected by the retina
-Reflex is mediated by the optical centre in the cerebral cortex
-A little slower than corneal reflex

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50
Q

Corneal reflex

A

Blink reflex
-Mediated by the sensory neurone from cornea which enters the pons

1) Cornea irritated
2) Triggers impulse along the SN
3) Relay neurone in the lower brain stem passes the impulse along
4) Signal branches in motor neurones to eyelid muscles below and above
5) Both eyes shut as a consensual response

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51
Q

Corneal reflex pathway

A

Sensory - relay - motor - facial muscles - eyelid blinks
=Short and direct = 0.1 seconds

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52
Q

What other pathways does the sensory neurone undergo during the corneal reflex

A

Sensory - myelinated neurones in the pons - sensory region in the cerebral cortex - informs higher brain stimulus has occurred
=Reflex can be overridden by conscious control

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53
Q

Pathway for overriding the corneal reflex

A

Cerebral cortex - inhibitory signals to the motor centre in the pons - myelinated neurones to/from cerebral cortex

=myelinated to/from the cerebral cortex transmit ap more rapidly than the non-myelinated relay neurones in the pons - so can inhibit the ap in motor neurone

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54
Q

Why is overriding the corneal reflex necessary for some people

A

Essential for people who wear contact lenses

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55
Q

Knee jerk reflex

A

Reflex action that straightens the leg when the tendon below the knee cap is tapped
Spinal reflex as nervous pathway passes through the spinal cord
-Involved in coordinated movement and balance

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56
Q

Knee jerk reflex pathway

A

1) Tap the patellar tendon
2) Patellar tendon stretches
3) This stretches the extensor muscle
4) When extensor muscle is stretched it triggers an impulse along the SN
5) Reflex signal goes along one motor neurone and causes the extensor muscle to contract
6) Relay neurone inhibits the other motor neurone of the flexor muscle causing it to relax
7) Leg kicks due to antagonistic muscle action

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57
Q

What is antagonistic muscle action

A

Signal tells extensor to contract and flexor to relax
-Doing opposite

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58
Q

How many neurones does the knee jerk reflex pathway consist of

A

Two: Sensory/motor
-Relay not involved so response is quicker
-No relay so brain cannot inhibit the reflex and no sufficient delay for inhibition

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59
Q

What happens however when the hamstring is contracting

A

Inhibitory ap are sent to the synapse in the reflex arc to prevent the reflex contraction of the opposing muscle

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60
Q

Name short term/ long term responses

A

Short term: Behavioural homeostatic mechanisms
Long-term: Behaviours associated with reproduction

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61
Q

What happens when mammals detect danger

A

the ‘fight or flight’ response is initated

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62
Q

What are the physiological changes in the ‘fight or flight’

A

1) Pupils dilate
2) Heart rate and blood pressure increases
3) Arterioles to the digestive system constrict and pupils dilate
4) Blood glucose levels increase
5) Metabolic rate increases
6) Erector pili muscles in the skin contract
7) Ventilation rate/depth increases
8) Endorphins (natural pain killers) are released into the brain

63
Q

Survival value of the pupils dilating

A

Allows more light to enter the eyes making the retina more sensitive to light

64
Q

Survival value of the heart rate and blood pressure increasing

A

Increases the rate of blood flow to deliver more O2 and glucose to muscles and remove CO2 and other toxins

65
Q

Survival value of the arterioles to the skin and digestive system constricting, while those at the muscles and liver are dilated

A

Diverts blood away from the skin and digestive system and towards muscles

66
Q

Survival value of the blood glucose levels increasing

A

Supplies energy for muscular contraction

67
Q

Survival value of the metabolic rate increasing

A

Converts glucose to usable forms e.g. ATP

68
Q

Survival value of the erector pili muscles in the skin contracting

A

Makes hair stand up - sign of aggression

69
Q

Survival value of the ventilation rate and depth increasing

A

Increases gaseous exchange so that more O2 enters the blood and supplies aerobic respiration

70
Q

Survival value of the endorphins (natural painkillers) being released into the brain

A

Wounds inflicted on the animal to does not prevent activity

71
Q

Coordination of the ‘fight or flight response’ (the cerebrum)

A

1) Inputs feed into the sensory centers in the cerebrum
2) The cerebrum passes signals to the association centres
3) If a threat is recognised, the cerebrum stimulates the hypothalamus
4) The hypothalamus increases activity in the sympathetic NS and stimulates the release of hormones from the anterior pituitaryCoordination of the ‘fight or flight response’ gland

72
Q

Coordination of the ‘fight or flight response’ ( Hypothalamus action) Left side

A

1) Activates SNS

2) Impulses activate glands and smooth muscles
OR
Activates adrenal medulla = secretion of adrenaline = bloodstream

3) Neural activity combines with hormones int he blood stream to constitute fight/flight

73
Q

Coordination of the ‘fight or flight response’ ( Hypothalamus action) Right side hormones

A

Secretes releasing hormones to stimulate pituitary gland

CRH = pituitary secretes ACTH = adrenal cortex secretes corticoid hormones = bloodstream

TRH = pituitary secretes TSH = thyroid gland secretes thyroxine = bloodstream

74
Q

What is the benefit of using the SNS in the fight/fight

A

It will increase the activity of effectors

75
Q

How is a prolonged response in the fight/fight achieved

A

Via the endocrine system - adrenaline

76
Q

How are the releasing hormones released from the hypothalamus

A

Down a portal vessel to the pituitary gland. This stimulates the release of tropic hormones from the anterior part of the pituitary gland
Stimulate activity of a variety of endocrine glands

77
Q

Tropic hormones

A

indirectly affect target cells by first stimulating other endocrine glands

78
Q

Tropic hormones

A

CRH / TRH

79
Q

CRH action

A

CRH = pituitary secretes ACTH = adrenal cortex secretes corticoid hormones = bloodstream

TRH = pituitary secretes TSH = thyroid gland secretes thyroxine = bloodstream

80
Q

Corticoid hormones action

A

Glucocorticoids (cortisol) regulate the metabolism of carbohydrates
-More glucose released from glycogen stores
-New glucose may also be produced from fat/ protein stores

81
Q

Thyroxine hormone action

A

Acts on nearly every cell in the body, increasing the metabolic rate and making cells more sensitive to adrenaline

82
Q

Important roles of the circulatory system

A
  • Transport of O2 and nutrients i.e. glucose/ fatty acids/ amino acids to the tissues
    -Removal of waste products i.e. CO2 from tissues = prevents accumulation, which could become toxic
    -Transport of urea from the liver and kidneys
    -Distribute heat around the body/ deliver it to the skin to be radiated away
83
Q

The circulatory system must adapt to meet the requirements of the tissues
How is the heart action modified to do this

A

-Raising/lowering the heart rate
-Altering the force of contractions of the ventricular walls
-Altering the stroke volume

This is to respond to changes in:
-Blood pressure
-pH of blood
-Stress

84
Q

Myogenic

A

The heart can initiate its own beat at regular intervals

85
Q

Problems with the heart being myogenic

A

The atrial muscle has a higher myogenic rate than the ventricular muscle
-Two pairs must contract in a coordinated fashion or the heart rate will be ineffective
-Needs a coordination mechanism

86
Q

How is the heart beat coordinated at rest

A

SAN (Pacemaker) - initiates own ap
-Overrides the myogenic action of the cardiac muscle

Also directly responds to adrenaline in the blood

87
Q

Cardiovascular centre

A

Part of the medulla oblongata in the brain that controls heart rate and other aspects of circulation
-Can change the frequency of the excitation waves of the SAN - do not initiate a contraction
-Supply the SAN
-Autonomic nervous system
-Ensures output to the SAN is appropriate to the environmental conditions

88
Q

What are the two nerves called, which the cardiovascular centre sends ap down

A

Sympathetic nerve = noradrenlaine
Vagus nerve = acetylcholine

89
Q

How does the cardiovascular centre affect the frequency of heart contractions

A

1) Ap sent down the sympathetic nerve (accelerator nerve) causes the release of the neurotransmitter noradrenaline at the SAN
= This increases heart rate

2) Ap sent down the vagus nerve release the neurotransmitter acetylcholine, which reduces the heart rate

90
Q

Sensory input to the cardiovascular centre includes

A

1) Stretch receptors in the muscles detect movement of the limbs
2) Chemoreceptors in the carotid arteries, the aorta and the brain monitor the pH of the blood.
3) Concentration of CO2 in the blood
4) Stretch receptors in the walls of the carotid sinus monitor blood pressure

91
Q

Sensory input to the cardiovascular centre includes (stretch receptors)

A

Stretch receptors in the muscles detect movement from the limbs. Sends impulses to the CVC informing that O2 may soon be needed - leads to an increased heartrate

92
Q

Sensory input to the cardiovascular centre includes (chemoreceptors receptors)

A

Chemoreceptors in the carotid arteries, the aorta and the brain monitor the pH of the blood.
-When we exercise muscles produce more CO2
-Blood plasma + CO2 = carbonic acid (reduces blood pH) + affects the transport of O2
-sends ap to CVS to increase heart rate

93
Q

Sensory input to the cardiovascular centre includes (CO2 concentration)

A

When we stop exercising concentration of CO2 in the blood falls
-Reduces activity of the accelerator pathway
-Heart rate falls

94
Q

Sensory input to the cardiovascular centre includes (stretch receptors in the walls of the carotid sinus)

A

Monitor blood pressure
-Increase detected by stretch receptors
-if too high sends ap to the CVS leading to a reduction in heart rate

95
Q

Carotid sinus

A

Small swelling in the carotid artery

96
Q

What happens if the mechanism that controls heart rate fails

A

An artificial pacemaker must be fitted
-Pacemaker delivers electrical impulses to the heart muscle
-Implanted under the fat/skin of chest
-Artificial pacemaker may be connected to the SAN or directly to the ventricle muscle

97
Q

What receptors measure changes in BP / pH

A

BP - Baroreceptors
pH - chemoreceptors

98
Q

How do the baroreceptors and chemoreceptors respond when bp gets too high

A

1) Detect change
2) Send impulse to medulla oblongata ( to the CVS)
3) Cardiostimulatory centre triggered to send an impulse along the sympathetic nerve to SAN
4) Heart rate increases
Neurotransmitter: noradrenaline

99
Q

How do the baroreceptors and chemoreceptors respond when bp gets too low

A

1) Detect change
2) Send impulse to medulla oblongata ( to the CVS)
3) Cardioinhibitory centre triggered to send an impulse along the vagus nerve to SAN
4) Heart rate decreases
Neurotransmitter: Acetylcholine

100
Q

What is muscle

A

Muscles are composed of cells arranged to form fibres
-Fibres can contract to become smaller which produces a force

101
Q

How is contraction of muscle achieved

A

Interaction between two protein filaments (actin/myosin) in the muscle cells
-Antagonist (arranged in opposing pairs) (one contracts/the other elongates)

102
Q

What may the antagonist be in some cases

A

Elastic recoil / hydrostatic pressure in a chamber

103
Q

What are the three different types of muscle

A

1) Involuntary (smooth)
2) cardiac
3) Voluntary (skeletal/striated)

104
Q

Involuntary (smooth) muscle

A

Contracts without conscious control

105
Q

Involuntary (smooth) muscle structure

A

-Consists of individual cells tapered at both ends (spindle-shaped)
- At rest, each cell is 500 um long and 5um wide
-Each cell contains a nucleus, bundles of myosin/actin
-Arranged in longitudinal/ circular layers that oppose eachother

106
Q

Involuntary (smooth) muscle function

A

Contracts slowly and regularly
-Controlled by autonomic NS
-Found in tubular structures i.e. digestive system/ blood vessels
-Circular layer runs around the intestine and its contraction causes segmentation
-Longitudinal layer of smooth muscle runs along the intestine; causes wave-like contractions

107
Q

Cardiac muscle

A

Muscle found in the heart walls

108
Q

Cardiac muscle structure

A

-Individual cells form long fibers, which branch to form cross-bridges between the fibers
-Cells are joined by intercalated discs

109
Q

How do the cross bridges in the cardiac muscle structure help with the hearts function

A

-Cross bridges helps ensure electrical stimulation spreads evenly across the four walls of the chambers / make sure when heart contracts it is a squeezing action
- In skeletal muscle the myofibrils/filaments lie longitudinally in the muscle, which means that the muscle can only contract on one direction

110
Q

How do the intercalated discs in the cardiac muscle structure help with the hearts function

A

Intercalated discs are specialized surface membranes fused to produce gap junctions that allow free diffusion of ions between cells
-AP pass easily and quickly along and between the cardiac muscle fibres

111
Q

Cardiac muscle contraction

A

Contracts easily and continuously throughout life
-Contracts powerfully and does not fatigue easily
-Myogenic - can initiate its own contraction - normally controlled by SAN

112
Q

How does cardiac muscle appear under the microscope

A

striped

113
Q

Voluntary (skeletal/striated muscle)

A

Muscle under voluntary control

114
Q

Voluntary (skeletal/striated muscle) structure

A

Skeletal muscle occurs at the joints in the skeleton
-Antagonistic muscle action - when one contracts the other elongates
-Muscle cells form fibers of about 100 um diameter
-Each fibre is multinucleate (contains many nuclei) and is surrounded by a membrane called the sarcolemma

115
Q

Voluntary (skeletal/striated muscle)

What are the cell structures called

A

multinucleate
Plasma membrane: sarcolemma
Cytoplasm: sarcoplasm - specialized to contain many mitochondria
Contains also an extensive sarcoplasmic reticulum

116
Q

Sacromere

A

Basic functional unit

117
Q

Sacrolemma

A

Plasma membrane around fibres

118
Q

Sacroplasm

A

Shared cytoplasm within fibres
-Cytoplasm allows different ions to move across

119
Q

Sarcoplasmic reticulum

A

Endoplasmic reticulum in sarcomere
-Gets depolarised and releases ca+ ions

120
Q

Myofibril

A

Long cylindrical organelles
-brings about muscle contraction
-Consists of myosin and actin

121
Q

Voluntary (skeletal/striated muscle)

How are the fibres arranged

A

-All the myofibrils tubes are wrapped around and stuck together by the sarcolemma to form a fibre
-Myosin is the dark longitdual bands and actin runs through the whole myofibril
-Each myofibril is split into sections called sacromeres

122
Q

Voluntary (skeletal/striated muscle)

Sarcomere structure

A

The sarcomere is between two Z zones
Myosin: thicker filament
Actin: Thinner filament (between each is called the H zone, when the dark band does not overlap)

Actin and myosin are arranged in a banded pattern

Dark bands: A bands (this is where the actin and myosin overlap) (in muscle contraction will stay the same length

Light bands: I band (this is where they don’t overlap) (in muscle contraction will shorten)

123
Q

What are the thick and thin filaments surrounded by

A

A sarcoplasmic reticulum

124
Q

Thin filaments

A

Actin
Consists of two chains of actin subunits twisted around each other:
Wrapped around actin is tropomyosin to which are attached globular molecules of troponin
-Parts of the mechanism to control muscular contraction
-At rest, these molecules cover binding sites to which the thick filaments can bind

125
Q

Troponin

A

Globular molecules attached to tropomyosin
Each troponin complex consists of three polypeptides:
1) One binds to actin
2) One binds to tropomyosin
3) One binds to Ca+ when made available

126
Q

Thick filaments

A

Each thick filament consists of a bundle of myosin molecules
-Each myosin molecule has two protruding heads that stick out at the end of the molecule
-Heads are mobile and can bind to actin when the binding sites are exposed

127
Q

Voluntary (skeletal/striated muscle)

Contraction

A

Quickly and powerfully
Also fatigues quickly

128
Q

How is contraction of the Voluntary (skeletal/striated muscle) stimulated

A

By the somatic NS

129
Q

What is the junction between the NS and a muscle called

A

Neuromuscular junction - synapse between a muscle fibre and neurone
-Used for faster ion diffusion in a neuromuscular impulse so the muscle contracts fast
-Many similarities with a synapse

130
Q

Voluntary (skeletal/striated muscle)

Stimulation of contraction

A

1) Ap arrive at the end of the axon open Ca+ ion channels in the membrane
2) Ca+ ions flood into membrane
3) Vesicles with acetylcholine fuse with the membrane and released by exocytosis
4) Acetylcholine diffuse across the gap and fuse with receptors in the sarcolemma
5) This opens the Na+ ion channels, which allows Na+ to enter and causes a depolarisation of the sarcolemma
6) A wave of depolarisation spreads along the sarcolemma and down transverse tubules into the muscle fibre

131
Q

The motor unit

A

Some motor neurones stimulate single muscle fibres
-Many motor neurones divide and connect to several msucle fibres
-All the muscle fibres contract together, providing a stronger contraction

132
Q

How is the electrical activity of muscles investigated

A

Using an electromyograph (EMG)

133
Q

How does an EMG work

A

1) Muscle stimulated motor neurones create ap in muscle fibres
2) Electrodes applied to he surface of the skin detect the combined effects of these ap
3) Simple contraction is seen as a series of disorganized peaks on the trace however the amplitude of the EMG recording reflects the number and size of motor units involved in the contraction - more powerful contraction = higher amplitude

134
Q

The sliding filament hypothesis

A

During contraction the light band and the H zone get shorter
-Z line moves closer together and the sacromere gets shorter
-During contraction the thick/thin filaments slide past one another

135
Q

The sliding filament hypothesis

The mechanism of contraction - how is the sliding movement caused

A

By movement of the myosin heads
1) When the muscle is stimulated, the tropomyosin is moved aside
2) This exposes the binding sites on the actin
3) The myosin heads attach to the actin and move
4) This causes the actin to slide past the myosin

136
Q

Stage one: stimulation

A

1) ap arrives
2) Ap depolarises sarcolemma and sarcoplasmic reticulum
3) Voltage-gated Ca2+ ion channels on the SR open to release Ca2+ ions into sarcoplasm
4) Ca2+ binds to troponin - conformational change
-Pulls on tropomyosin - exposes actin-myosin binding sites

137
Q

Stage two: Attachment

A

1) Myosin head binds to the A-M binding site and forms cross bridges
2) Myosin filament flexes
-Conformational change
-ADP released
-Pulls actin along

138
Q

Stage three: detachment

A

1) ATP can now bind to the myosin head as ADP has been released
2) This releases the myosin head from the binding site = conformational change
3) Ca2+ ions activate ATPase in the myosin head
4) The ATP attached to the myosin head is hydrolysed to form ADP+pi
5) Energy released from ATP hydrolysis returns the myosin head back to the original position
6) Myosin head attaches to the next A-M binding site and the process repeats itself

139
Q

What is important to note about ATP in the sliding filament model

A

ATP used to return the myosin head back to the original position not to flex it

140
Q

The sliding filament hypothesis

Control of contraction

A

1) When muscle is stimulated the ap passes along the sarcolemma and down the transverse tubules into the muscle fibre
2) ap carried to the sarcoplasmic reticulum
3) Sarcoplasmic reticulum stores/ releases Ca+ ions into sarcoplasm
4) Ca+ bind to troponin and alters the shape pulling the tropomyosin to the side = exposes actin binding sites
5) Myosin heads bind to the actin and forms cross bridges between the filaments
6) Myosin head move, this pulls the actin filament past the myosin filament
7) The myosin heads detach from the actin and can bind again further up the actin filament

141
Q

What happens after contraction has occurred

A

Ca+ ions are pumped back into the sarcoplasmic reticulum, which allows the muscle to relax

142
Q

The role of ATP in muscle contraction

A

-Supplies energy for contraction
-Part of the myosin head acts as ATPase and hydrolyses ATP to ADP+ pi which releases energy

143
Q

ATP being broken down myosin

A

1) Myosin head attaches to the actin filament, which forms a cross bridge
2) Myosin moves (tilts back) which causes the thin filament to slide past the myosin filament
- Power stroke = ADP + pi released from the myosin head
3) A new ATP attaches to the myosin head and breaks the cross bridge
4) Myosin head moves back to original position (tilts forward) as the ATP is hydrolysed
-Releases energy for movement to occur
5) Myosin head can make a new cross bridge further along the actin filament

144
Q

How is the supply of ATP maintained for muscle contraction

A

1) Aerobic respiration in the mitochondria
2) Anaerobic respiration in the sarcoplasm tissue
3) Creatine phosphate in the sarcoplasm

145
Q

How does aerobic respiration in the mitochondria maintain the supply of ATP for muscle contraction

A

Muscle tissue contains many mitochondria so aerobic respiration can occur
-Bohr effect helps to release more O2 from the haemoglobin in in the blood
-However during rigorous activity the rate at which ATP can be produced will be limited by the delivery of O2 to the tissue

146
Q

How does anaerobic respiration in the sarcoplasm of muscle tissue maintain the supply of ATP for muscle contraction

A

Can release a little more ATP from the respiratory substrates
-However leads to the production of lactate which is toxic
-Anaerobic respiration can only last a few seconds before lactic acid build up starts to cause fatigue

147
Q

How does creatine phosphate in the sarcoplasm maintain the supply of ATP for muscle contraction

A

Acts as a reserve store of phosphate groups
-Phosphates can be transferred from the creatine phosphate to ADP molecules, creating ATP more rapidly
-Enzyme creatine phosphotransferase is involved
-Supply of creatine phosphate is sufficient to support muscular contraction for a further 2-4 seconds

148
Q

What is a conformational change

A

Proteins shape has changed, which leads to a substrate binding/ breaking away from the protein

149
Q

Stage 1: Attachment

A

1) Myosin binds to the A-M binding site and forms c

150
Q

Problems with high BP

A

Small blood vessels leak
-Leakage
-Increase pressure
-Cell death as cells cannot respire

151
Q

Why if a person has high BP should you not use a drug that will counteract a blood clot

A

It will make the bleeding worse

152
Q

At rest what would the striated muscle look like

A

H zone wider
Z zone further apart

153
Q

Compare smooth/striated/cardiac muscle

A

Smooth
-no striations
-actin and myosin
-Individual tapered cells joined in a tissue
-No fibres
-Slow continuous contraction
-Involuntary

Striated:
-Striations
-Actin and myosin
-Multinucleate fibres
-Parallel fibres
-Rapid contraction
-Voluntary

Cardiac:
-Striations
-Actin and myosin
-Cells joined by intercalated discs
-Fibres with cross-bridges
-Continuous rhythmic contractions
-Involuntary

Module 5 (10 decks)

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