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Biology > Chapter 15 - Nervous Coordination And Muscles > Flashcards

Chapter 15 - Nervous Coordination And Muscles Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does the nervous system do?

A

Uses nerve cells to pass electrical impulses to communicate

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2
Q

What does the hormonal system do?

A

Produces chemicals (hormones) that are transported in blood to their target cells to communicate

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3
Q

List the differences between the hormonal and nervous system [3]

A
  1. Hormonal uses chemicals to communicate whereas nervous uses electrical impulses
  2. Transmission is by blood system in hormonal whereas nervous is by nerves
  3. Hormonal transmission is relatively slow compared to very rapid in nervous
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4
Q

What is the nervous system broken down into?

A

Peripheral Nervous System and Central Nervous System

Peripheral = sensory and motor nervous system
Central = brain and spinal cord

Motor = voluntary and autonomic nervous system

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5
Q

Describe what happens when a stimulus stimulates PNS

A
  1. Stimulation of a receptor in periphery of body
  2. Sensory nerves carries sensory info from receptor to spinal cord and brain
  3. Sensory info is processed by the brain
  4. Commands generated in brain
  5. These are sent down spinal cord via motor neurone
  6. Motor neurone transmits the command to an effector
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6
Q

Describe the differences between the voluntary and autonomic nervous system [4]

A
  1. involves voluntary motor neurone compared to autonomic motor neurone
  2. Associated with control of body movements compared to controlling of visceral functions (internal organs)
  3. Motor neurones carry commands to skeletal muscles to initiate movement whereas carry commands to effectors like cells in the organs
  4. Within our control vs out of our control
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7
Q

What is the reflex arc?

A

A completely involuntary and rapid response to a stimulus.

  • reflex is made possible by neural pathways called reflex arcs which can act on an impulse before it reaches the brain
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8
Q

Give an example of the process of a reflex arc

A
  • stimulus detected by a receptor (pin in skin)
  • creates nerve impulses which pass along a sensory neurone into spinal cord
  • impulse then passes to an intermediate neurone
  • Impulse leaves spinal cord, via a motor neurone which stimulates a muscle (effector) resulting in a response
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9
Q

What is a myelinated neurone? Explain its role

A

A neurone that has Schwann cells wrapped around its axon
- Schwann cells contain a protein called myelin

These support cells wrap around so that layers of their membrane build up providing electrical insulation round the axon = myelin sheath

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10
Q

What is resting membrane potential in neurones?

A

The inside of the axon is negatively charged in comparison with the outside

= -70mV difference

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11
Q

What does a voltmeter do?

A

Measures electrical potential (charge difference between 2 points)

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12
Q

What is the difference between cations and anions

A

Cations are positive
Anions are negative

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13
Q

Describe the NA+/K+ pump and its role in resting membrane potential

A
  • 3 Na+ are actively transported out of the cell creating a higher concentration of Na+ on the outside
  • 2 K+ are actively transported into the cell creating a higher concentration of K+ on inside
  • as there is 2 K+ for 3 Na+ = positive on outside and negative on inside by -70mV
  • when there is a charge difference , the axon membrane is POLARISED
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14
Q

What do leak channels do?

A
  • Axon membrane is more permeable to K+ compared to Na+ because there are more leak channels for K+ so more K+ diffuse out of cell
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15
Q

What is an action potential?

A

A change in the membrane potential that spreads along an axon

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16
Q

What are the 2 types of protein channels in axon membrane?

A

Voltage gated sodium ion channels

Voltage gated potassium ion channels

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17
Q

Describe an action potential [8]

A
  1. Stimulus disrupts the resting membrane potential
  2. This stimulates the voltage gated Na+ channels to open
  3. Na+ move into axoplasm from tissue fluid by facilitated diffusion
  4. This movement depolarises the axon membrane to be +40mV in the axoplasm
  5. The depolarisation causes voltage gated Na+ channels to close and voltage gated K+ channels to open
  6. So K+ move out of axoplasm by facilitated diffusion which repolarises the axon membrane
  7. Membrane potential overshoots -70mV leading to hyperpolarisation
  8. Na+/K+ pump helps to restore resting membrane potential
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18
Q

What is the all or nothing law?

A

A specific level of stimulus is required to meet the THRESHOLD value to trigger an action potential

  • if stimulus is too small, threshold wont be met so AP is not generated
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19
Q

What is needed for an action potential to occur?

A
  • stimulus must be big ENOUGH
  • to open ENOUGH voltage gated Na+ channels
  • to let ENOUGH Na+ diffuse in
  • to reach a membrane potential of -55mV (threshold)
  • if threshold is met then more Na+ channels will open (positive feedback) to cause a large inflow of Na+ = depolarisation of membrane and an AP
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20
Q

What is the refractory period?

A

A short phase of time following an AP when another AP cannot be generated

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21
Q

What occurs during the refractory period so no AP’s are generated?

A
  1. Voltage gated Na+ channels are closed and will not open. Voltage gated K+ channels open
  2. So during this time, the threshold cannot be reached and an AP / depolarisation cannot occur (or greater stimulation is required)
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22
Q

What happens in later stage of refractory period?

A

(Hyperpolarisation)

Na+/K+ pump works to redistribute ions for subsequent impulses to be initiated

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23
Q

What is the significance of the refractory period?

A
  • ensures AP’s are propagated in only 1 direction - as the previously depolarised section of membrane is repolarising + in refractory period so AP can only go forwards
  • produces discrete separate signals - AP’s are clearly separated from each other
  • limits how close 2 AP’s are - limits number of AP’s that can pass along an axon at a given time
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24
Q

Movement of substances across cell membrane is affected by membrane structure. Describe how [5]

A
  • phospholipid bilayer allows diffusion of non-polar, lipid soluble substances
  • phospholipid bilayer prevents diffusion of polar/ charged substances
  • carrier proteins allow active transport using ATP
  • carrier/ channel proteins allow facilitated diffusion
  • shape of channel determines which substances move
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25
Q

How is an action potential propagated along an unmyelinated neurone?

A
  1. Depolarisation occurs in one part of axon
  2. This creates a local circuit with the adjacent section of the axon so NA+ diffuses sideways along the local circuit
  3. This disrupts the membrane potential in next adjacent section triggering the opening of voltage gated sodium channels so NA+ diffuses in
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26
Q

Why are impulses conducted faster in a myelinated axon compared to an unmyelinated axon?

A
  • In myelinated the action potential does not occur along the whole length of the axon
  • the action potential can only occur at nodes
  • this impulse jumps from node to node by saltatory conduction
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27
Q

Name and explain the 3 factors affecting the speed of conduction of an action potential

A
  1. Axon diameter - impulses travel faster in wider axons as there is less resistance to ion fatigue
  2. Myelination - impulses travel faster by saltatory conduction
  3. Temperature - low temps slow down transmission in organisms that do not regulate body temp internally (cold blooded) - kinetic energy during diffusion
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28
Q

What is the synapse?

A

The point where one neurone connects with another neurone or an effector (a muscle)

  • they transmit the impulse from one neurone to the next
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29
Q

What is an excitatory synapse? What is the other name for it?

A

They increase the probability of an AP/ depolarisation occurring in post synaptic neurone

  • cholinergic synapse
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30
Q

Describe what occurs at a cholinergic synapse

A
  1. Stimulus arrives which depolarises the pre-synaptic membrane
  2. This causes voltage gated calcium ion channels to open and calcium diffuses in
  3. Calcium ions binds to and causes vesicles to move forward and fuse with pre synaptic membrane. Neurotransmitter (acetylcholine) is then released via exocytosis
  4. Neurotransmitter diffuses across synaptic cleft and binds to protein receptors on post synaptic membrane, causing Na+ channels to open allowing Na+ to diffuse in
  5. If threshold is met, an AP will occur and be propagated along post synaptic neurone
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31
Q

What is the neurotransmitter at a cholinergic synapse?

A

Acetylcholine

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32
Q

What is an inhibitory synapse? What’s the other name for it?

A

Makes it more difficult for an AP/ depolarisation to occur on the post synaptic neurone

  • GABAergic synapse
33
Q

Describe what occurs at a GABAergic synapse

A
  1. Stimulus arrives which depolarises the pre-synaptic membrane
  2. This causes voltage gated calcium ion channels to open and calcium diffuses in
  3. Calcium ions binds to and causes vesicles to move forward and bind with pre synaptic membrane. Neurotransmitter (GABA) is then released via exocytosis
  4. Neurotransmitter diffuses across synaptic cleft and binds to protein receptors on post synaptic membrane, causing K+ channels to open and K+ diffuses out
  5. Also triggers opening of chloride ion channels (Cl-)
  6. Results in hyper polarisation of membrane so threshold is not met and no AP is produced
34
Q

What is the neurotransmitter at a GABAergic synapse?

A

GABA

35
Q

Why is summation sometimes required?

A

In order for an AP to be triggered on post synaptic neurone, the threshold must be exceeded.
- some neurones on their own may not release a sufficient amount of neurotransmitter to open enough Na+ channels to allow enough Na+ to diffuse in to reach threshold

36
Q

What is spatial summation?

A
  • multiple pre synaptic neurones together release enough neurotransmitter to reach threshold + trigger an AP on post synaptic neurone
37
Q

What is temporal summation?

A
  • a single presynaptic neurone releases neurotransmitter many times over a short period of time due to a high frequency of AP’s travelling along the pre synaptic neurone
  • results in release of enough neurotransmitter to reach threshold + trigger an AP on post synaptic neurone
38
Q

How is the signal controlled on a neurone?

A

Removing the neurotransmitter from the synaptic cleft otherwise it will continue to stimulate post synaptic neurone

  1. Some will naturally diffuse away
  2. Degradation by enzymes
  3. Re-uptake into pre-synaptic neurone
39
Q

What do drugs do to the nervous system?

A

Stimulates nervous system by causing more AP’s on post synaptic neurone by:
- mimicking a neurotransmitter = stimulating release of more NT

OR

Inhibiting the enzyme that breaks down the NT/ blocking NT re uptake transporter

40
Q

What do receptors do?

A

Respond to a single specific stimulus - found at the ends of sensory neurones in PNS

41
Q

What do it mean saying that receptors act as transducers?

A

They convert a type of stimulus into an electrical signal (first a generator potential, followed by an AP in sensory neurone)

42
Q

What are the 3 key types of receptors?

A
  1. Pacinian Corpuscle - responds to mechanical pressure
  2. Photoreceptors (rod+cone) - responds to light in retina of eye
  3. Chemo + pressure receptors - control heart rate
43
Q

How does the Pacinian Corpuscle receptor work?

A
  • when a pressure is applied to the skin, this deforms the lamallae on Pacinian corpuscle + sensory neurone membrane = widening +opening of stretch mediated Na+ channels
  • Na+ diffuses in to sensory neurone = depolarisation + a generator potential
  • Na+ diffuses laterally along a local circuit to the first node of ranvier, where it disrupts the resting potential + triggers opening of voltage gated Na+ channels
  • Na+ diffuses in, depolarising the membrane and if threshold is exceeded = an AP
44
Q

What is a generator potential?

A

Initial depolarisation which may or may not reach threshold at first node of ranvier so may or may not trigger an AP.

45
Q

What happens when more pressure is applied to skin?

A

The greater the pressure applied…the more stretch mediated Na+ channel will open… +the more Na+ will diffuse in

46
Q

what are the 2 types of photoreceptors?

A

Rod cells and cone cells

47
Q

Describe how light hits the photoreceptors

A
  • light travels through transparent lens of the eye and hits the fovea (part of retina directly behind lens)
  • fovea has a high concentration of cone cells
  • in periphery, there is a high concentration of rods
  • convert the stimulus to electrical impulse due to breakdown of a pigment = bleaching
  • a generator potential is created in bipolar cell
  • An AP may or may not be generated on ganglion cell (sensory neurone) + leaves eye through optic nerve
48
Q

What are the 2 different types of pigments in photoreceptors?

A

1.Rhodopsin
- high sensitivity to light so low level of light needed to break it down
= used to see in dark

  1. Iodopsin
    - low sensitivity to light so high levels of light needed to break it down
    = used in light
49
Q

What are rod cells used for?

A
  • used to see in low light levels - contain rhodopsin pigment
  • multiple rod cells synapse with a single bipolar cell and sensory neurone = spatial summation/ retinal convergence
  • image seen as black and white as cannot distinguish between different wavelengths of light
50
Q

What are cone cells used for?

A
  • used to see in high light levels - contain iodopsin pigment
  • each cone cell synapses with a single separate bipolar cell and sensory neurone = no summation
  • 3 types of cone cells each sensitive to different wavelengths of light (green, red, blue) so images seen in colour
51
Q

Describe 4 differences between rod and cone cells [4]

A

ROD CONE
1. Located in periphery of retina VS fovea of retina
2. 120 million in each eye VS 6 million in each eye
3. Low visual acuity VS good visual acuity
4. High sensitivity to light VS low sensitivity to light
5. Can’t detect colour VS can detect colour

52
Q

What system of the nervous system are chemo and pressure receptors part of?

A

Autonomic nervous system

  • so they control bodily activities unconsciously e.g. internal organs, muscles, regulating HR etc
53
Q

What are the 2 divisions of the autonomic nervous system?

A
  1. Parasympathetic = motor neurones have a suppressive effect on effectors
  2. Sympathetic = motor neurones have a stimulator effect on effectors
54
Q

Describe the role of chemoreceptors in controlling heart rate during exercise

A
  • during activity you have increased respiration and increased CO2 levels
  • Chemoreceptors detect a decrease in pH of blood
  • send impulses along sensory neurones to medulla oblongata
  • Medulla oblongata increases frequency of impulses along SYMPATHETIC motor neurone to SA node
    = a higher heart rate
55
Q

Describe the role of baroreceptors in controlling heart rate

A
  • baroreceptors detect blood pressure being higher than normal
  • send impulses along sensory neurones to medulla oblongata
  • medulla oblongata increases frequency of impulses along PARASYMPATHETIC motor neurone to SA Node
    = a lower heart rate
56
Q

What is skeletal muscle?

A

Attached to bone via tendons

  • role is to move bones of the skeleton
  • they work under voluntary, conscious control

Also work in antagonistic pairs - when one contracts (agonist), the other relaxes (antagonist)

57
Q

What are tendons made of?

A

Collagen

58
Q

What is within skeletal muscle - break it down into its smaller parts

A
  1. There are bundles of muscles fibres
  2. These contain individual muscle fibres
  3. These contain myofibrils
59
Q

What do repeated units of myofibril make up? List the key parts

A

Sarcomere:

  • sarcolemma = membrane of muscle fibre
  • sarcoplasmic reticulum = like the endoplasmic reticulum
  • T-Tubules
  • sarcoplasm = like the cytoplasm
60
Q

What is the key thing stored in sarcoplasmic reticulum?

A

They store calcium ions (CA2+)

61
Q

Within sarcomeres there are 2 proteins…

What are these called and describe them + what they’re attached to

A

Actin (thin) Filament = 2 strands of small globular proteins twisted around each other - anchored to Z-Lines

Myosin (thick) Filament = long fibrous proteins with bulbous heads bundled together - anchored to M-Lines

62
Q

What are the different bands/lines/zones in a sarcomere?

A

I band - has just the thin filament (actin)

H Zone - has just the thick filament (myosin)

A Band - a bit of both (actin and myosin overlapping)

Z Lines - ends of sarcomere

M Line - the middle of the sarcomere

63
Q

What is the biological definition of a muscle contraction?

A

When a muscle is stimulated by a nerve impulse, it causes simultaneous contraction of all sarcomeres

64
Q

SLIDING FILAMENT THEORY

Describe what it is and what occurs

A

Mechanism for the contraction and relaxation of a sarcomere

  • myosin bulbous heads can bind to myosin binding sites on actin globular proteins + pull actin inwards causing it to slide over myosin
  • This pulls the Z-Lines inwards towards each other causing contraction of sarcomere
65
Q

What happens to each of the bands/ lines/ zones during contraction?

A

Z Line - slides towards each other

A Band - stays same because it is the length of myosin + myosin stays same length

H Zone - disappears as actin slides over myosin

I band - decreases as it contains only actin + actin slides over myosin

66
Q

What is the neuromuscular junction?

A

Junction between a motor neurone and a muscle (like a synapse)

  • there are multiple of these along muscular fibres to ensure rapid contraction
67
Q

Describe how a neurotransmitter crosses a neuromuscular junction

A

STEPS ARE THE SAME AS A SYNAPSE EXCEPT:

  1. Neurotransmitter (always excitatory) crosses a neuromuscular junction
  2. Neurotransmitter binds to receptors on SARCOLEMMA
  3. Na+ diffuses in to SARCOPLASM and a wave of depolarisation spreads across SARCOLEMMA and down T-TUBULES
  4. SARCOLEMMA becomes depolarised
68
Q

What occurs after a wave of depolarisation spreads across the sarcolemma?

A
  • As depolarisation travels down t-tubule, it triggers opening of voltage gated Ca2+ channels on sarcoplasmic reticulum
  • Ca2+ diffuses out into sarcoplasm
  • Ca2+ remain floating in sarcoplasm causing cross bridge cycle
69
Q

What are the 2 proteins on an actin filament?

A

Tropomyosin - covering myosin binding sites

Troponin - globular protein attached to tropomyosin

70
Q

Describe the steps involved in the cross bridge cycle

A
  1. Ca2+ binds to troponin which causes troponin to move position so tropomyosin also moves = exposes myosin binding sites
  2. Myosin heads bind to myosin binding site = crossbridge formation
  3. ADP+Pi get released by myosin head changing angle = power stroke and actin sliding over myosin
  4. Space for ATP to bind to myosin head which triggers myosin heads to detach from myosin binding site
  5. ATP is hydrolysed by ATP hydrolase which allows myosin to go back to original position = cocking of head
71
Q

How is ATP hydrolase activated in crossbridge cycle?

A

It is activated by the calcium ions

72
Q

Why does muscle contraction require ATP?

A
  1. The movement of myosin heads (cocking to original position)
  2. Reuptake of Ca2+ ions into sarcoplasmic reticulum = done by active transport
73
Q

Describe features of a fast twitch muscle fibre

A
  • Anaerobic, pale in colour (due to little myoglobin), low blood supply, fatigue rapidly, low number of capillaries and mitochondria
74
Q

What are fast twitch muscle fibres used for and why?

A

SPRINTERS
- generate most of the ATP for contraction via glycolysis
- leads to rapid contractions however only used for short periods of time as they fatigue quickly
- consume large amounts of glucose from glycogen stored in muscle

75
Q

What is phosphocreatine used for in fast twitch muscle fibres?

A

Used as a reserve supply of ATP (immediately available) to maintain rapid contractions for short periods

76
Q

Describe features of a slow twitch muscle fibre

A
  • aerobic, red in colour (due to lots of myoglobin), high blood supply, fatigue slowly, high number of capillaries and mitochondria
77
Q

What are slow twitch muscle fibres used for and why?

A

MARATHON RUNNERS

  • generated most of ATP for contraction via oxidative phosphorylation in mitochondria
  • requires high oxygen consumption
78
Q

What does myoglobin do?

A

Stores oxygen

Biology (22 decks)

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