Topic 9 Chemical Control in Animals Flashcards
1
Q
The hormone adrenaline is unable to pass through cell membranes.
When liver and muscle cells are exposed to adrenaline, the enzyme glycogen phosphorylase breaks down glycogen.
Describe how adrenaline causes liver cells to increase the concentration of glucose in the blood. (3 marks)
A
- adrenaline binds to receptors on membrane / cell surface
- second messenger cAMP involved
- activates glycogen phosphorylase
- glucose diffuses out of cells
2
Q
Compare the mechanisms used in hormonal and nervous coordination in mammals. (3 marks)
A
Hormonal / nervous
- chemical / electrical impulses
- transported in blood / via neurones
- slow speed of transmission / fast speed
- long lasting response / short lived
- wide spread effect / localised
3
Q
Given thyroxine is able to enter the cell,
How does thyroxine increase the secretion of adrenaline from adrenal glands? (4 marks)
A
- can enter so it’s hydrophobic
-thyroxine binds to receptors - enters the nucleus
- activates transcription factor / stimulates transcription
- increased protein synthesis
- synthesise more adrenaline
4
Q
What are endocrine glands?
A
Releases hormones
5
Q
What are exocrine glands?
A
Secreting digestive juices like enzymes
6
Q
What is the definition of hormones?
A
Chemical messengers released by glands travelling via blood towards target cell by binding complementary receptors
7
Q
Which parts of the brain will help to coordinate endocrine functions?
A
Hypothalamus and pituitary gland
8
Q
What are the 2 types of hormones?
A
protein based and lipid based
9
Q
What are examples of protein based hormones?
A
Adrenalin
melatonin
FSH
ADH
LH
10
Q
What are examples of lipid based hormones?
A
steroid hormones like
oestrogen
11
Q
Where are steroid (lipid) hormones derived from/made of?
A
cholesterol
12
Q
Where are protein based lipids derived from/made of?
A
multiple amino acid chain
tyrosine and tryptophan
13
Q
Describe the process of hydrophilic hormones
A
- a cascade of reactions
- binds to complementary receptor
- changes shape of G protein
- it becomes complementary to adenylyl cyclase
- breaks down ATP to cAMP
- cAMP is a second messenger, binds to kinase enzyme
- catalyse reaction
14
Q
Do cells have the same genes and how do they have different functions?
A
All have the same 46 chromosomes
but depends on what genes are switched on and off
hence gene expression
15
Q
What do transcription factors do?
A
promote transcription and translation
16
Q
Describe the process of hydrophobic hormones causing synthesis?
A
It can diffuse through the cell membrane
It binds to complementary steroid receptor
Forming hormone receptor complex
Enters nucleus - act as transcription factor
triggers more transcription
17
Q
What are the 3 types of neurons?
A
Sensory
Relay/interneuron
Motor
18
Q
Which 2 systems are the mammalian nervous system composed of?
A
central and peripheral
19
Q
What is the central nervous system made up of?
A
brain and spinal cord
20
Q
What are 2 systems in the peripheral nervous system?
A
- autonomic
- voluntary (under conscious control)
21
Q
What is the structure of the spinal cord?
A
- cylindrical bundle of nerve fibres from brain stem to lower back
- consists of nerve tissues
- 31 pairs of spinal nerves
- grey matter: H shaped regions contained neurons
- white matter: myelinated axons
22
Q
What are the 2 main divisions of autonomic nervous system?
A
- sympathetic (arousing)
- parasympathetic (calming)
act antagonistically
23
Q
Describe the sympathetic nervous system.
A
- usually stimulates effectors (FIGHT OR FLIGHT) (s-s)
- neurotransmitter nonadrenaline
- ganglia located near CNS
24
Q
Describe the parasympathetic nervous system
A
- usually inhibits effectors
- eg neurotransmitter acetylcholine
- ganglia located far from CNS
REST & DIGEST
25
What is the location and main function of the medulla oblongata?
brain stem
control breathing and heart rate
26
What is the location and main function of the cerebellum?
lower back, behind spinal cord
controls balance and coordination of movement
27
what is the location and main function of the cerebrum?
front and top
initiates movement
28
What is the location and main function of the hypothalamus?
above pituitary gland
temperature regulation and osmoregulation
29
Compare the autonomic vs somatic nervous system
autonomic / somatic
both: part of peripheral nervous system
regulate function of internal organs / voluntary movements
we are not in control / in control
30
What are the advantages having both autonomic and voluntary motor nerves?
- leave conscious areas of brain free to make decisions
- voluntary can override autonomic system if necessary
31
what do sensory neurons do?
transmit impulses from receptors
32
what do motor neurons do?
transmit electrical signals from CNS to glands of body
33
what do relay neurons do?
transmit electrical impulses between motor and sensory neurons
34
What is the resting potential of nerve cells?
-70mV
35
What is potential difference?
When there’s a difference in charge
36
What does it mean by polarised in sensory receptors?
When a neurone has resting potential
37
What is the threshold value for sensory receptors?
What then happens?
When potential difference at -50mV
Sodium ion channels open
38
What is the refractory period in sensory receptors?
Time between one action potential and when another action potential can occur
39
How does the sodium/potassium pump used in resting potential ?
Pumps locate in neurone membrane
Pumps **3 Na+ out**
Pumps **2 K+ in**
->Resting potential achieved
More positive ions out
40
Explain how the resting potential is maintained in a neurone. (4 marks)
- sodium potassium pump
- 3 Na+ ions out, 2 K+ ions in
- K+ ions out via potassium channels (leaky)
- sodium channels close, Na+ don't move in
- outside more positive than inside
41
Can action potential increase in size?
NO! Only frequency.
42
What happens in depolarisation?
Action potential has passed the threshold value
So voltage gated sodium channel open, sodium ions flood **in** neurones
Via **facilitated diffusion**
Then diffuse **down** the axon
43
What happens in repolarisation?
Sodium ion channels shut
Potassium ion channels open, potassium ions facilitated diffuse out
+ hyperpolarise
44
Why does hyperpolarisation happen?
Action potential can only travel in one direction
Prevent immediate stimulation again
Refractory period
45
What produces myelin sheath?
Schwann cells
46
What is between myelin sheath?
Nodes of Ranvier
47
Why is conduction in myelinated neurones faster than normal neurones?
Action potentials jump between nodes of Ranvier aka saltatory conduction
(Less space for sodium ions to enter as they cannot travel through myelin sheath)
48
What is the condition without myelin sheath or demyelination?
Multiple sclerosis
49
What is the synapse called?
Synaptic cleft
50
How does action potential travel between two neurones?
1. Action pot travels down pre-synaptic knob
- trigger voltage gated Calcium ion channels to open
2. Calcium ions cause vesicles to exocytose (active)
- release vesicles (that contain neurotransmitters [NT])
3. NT diffuse down the conc grad across synaptic cleft
4. Attaches to complementary receptors on post-synaptic membrane - that is attached to sodium channels
5. Triggers CHEMICALLY gated sodium ion channels to open
- sodium ions facilitated diffuse into post synaptic knob = **depolarisation**
6. EPSP created
7. Neurotransmitters broken down using enzymes into products
8. Products reabsorbed and recycled at presynaptic knob
51
What is EPSP
Excitatory post-synaptic potential
52
Why is it important to digest neurotransmitters on receptors of post-synaptic knobs?
To close the sodium ion channels
So that new action potential can be triggered
If not, will cause paralysis
- make receptors available again, prevent prolonged action potential in post-synaptic membrane
53
What enzyme is used to digest acetylcholine, and what are the products?
Acetylcholinesterase
Into Acetylcholine-CoA + choline
54
Describe and explain the sequence of events that occurs at the synapse, AFTER a neurotransmitter has been released. (5 marks)
- diffuses across synaptic cleft
- binds to complementary receptor on post synaptic membrane
- trigger opening of voltage gated sodium ion channels
- cause depolarisation
- neurotransmitter broken down by enzyme
- so don’t get prolonged action potential in post-synaptic membrane/make receptors available again
55
Which region of the brain only controls breathing and heart rate?
medulla oblongata
56
What type of neurone releases acetylcholine and what is the effect of it?
- parasympathetic neurone
- lowers HR (rest and digest)
57
Describe the events that lead to the release of acetylcholine at a synapse. (3 marks)
- action potential arrives at pre-synaptic knob
- calcium channel opens and influx of calcium ions
- vesicles move to membrane
- vesicles fuse w membrane, release acetylcholine by exocytosis
58
Explain why a person with Alzheimer's disease may show a change in behaviour. (2 marks)
- reduced hippocampus
- so loss of memory
OR
- reduced cerebral cortex
- inability to perform everyday tasks
59
What is the effect of inhibitory drugs? (3 marks)
- Blocks voltage-gated sodium ion channels
- so **no movement of sodium ions into neurone, passing through**
- so prevents depolarisation/action potential
60
Describe the sequence of events that leads to an ESPS in the postsynaptic neurone. (4 marks)
- arrival of action potential at presynaptic knob
- calcium channels open, influx of calcium ions
- vesicles fuse w presynaptic membrane
- neurotransmitter diffuses across synaptic cleft
- attaches to complementary receptor on postsynaptic membrane
61
Is nicotine, Lidocaine and cobra venom excitatory or inhibitory respectively?
excitatory
inhibitory
inhibitory
62
Explain why the speed of nerve impulses along axons is slower without myelination. (3 marks)
- no saltatory transmission
- as no nodes of Ranvier
- so impulse does not jump between nodes
(- sodium channels have to open in every part of membrane)
63
What do IPSPs do?
- open up K+ ion channels
- lead to hyperpolarisation
- K+ ions diffuse out of neurones
- **less likely to pass on action potential** - since potential difference getting more -ve
64
What is the effect of nicotine?
- competitive inhibitor to acetylcholine (v similar effects)
- triggers action potential
- rest and digest effect
65
What are 3 factors affecting speed of neurone transmissions?
- temp
- diameter of axon
- presence of myelin sheath
66
Why does increase in temp increase rate of nervous transmissions?
- Na+/K+ have more KE so can diffuse in and out of neurones faster
- higher enzyme activity (eg ATP synthase and ATP production)
67
Why do axons with larger diameters have higher rates of nervous transmissions?
- the neurone will have smaller SA:V ratio
- so less leakage of Na+/K+ from neurone
(- less resistance as well)
68
Why do non-myelinated neurones require more energy?
- Na+/K+ are pumped in and out across a greater area of membranes (i.e. nodes of Ranvier)
- So more ATP required for pump
69
Why is there a refractory period?
voltage gated Na+ channels are closed
so cant depolarise
As Na+ cannot diffuse into neurone
70
What is the importance of the refractory period?
- ensures action potential only travels in one direction
( and - leave gaps between impulses so brain can translate into sensations)
71
What is the effect of oestrogen on transcription?
1. some cells have oestrogen receptors (ER)
2. have DNA binding site, blocked by inhibitor molecule
3. Oestrogen binds to ER after diffusing into cell
4. activated ER acts at TF
5. binds to specific DNA sequence in promoter region - to promote or inhibit
72
Explain how phospholipid conc affects the neurone structure and transmission of an impulse. (3 marks)
- as phospholipid conc decreases, rate of transmission decreases
- due to fewer Schwann cells/myelin sheath
- affect saltatory **conduction**
- affect action potential an Na+ ion movement
73
Describe the role of rod cells in initiation action potentials to the brain of the mouse. (5 marks)
- rhodopsin is bleached into trans-retinal and opsin
- Na+ channel close
- Na pump continues
- rod cell hyperpolarises
- less glutamate released
- bipolar cell depolarises
74
Describe the differences in the structure of a myelinated sensory neurone and myelinated motor neurone. (3 marks)
sensory / motor
- longer dendron / shorter
- shorter axon / longer
- cell body in the middle / towards the end
75
Compare and contrast the central and peripheral nervous systems. (3 marks)
both
- contain neurones / nerve cells
- contain synapses
CNS / PNS
- no / split into para and sympathetic systems
- no / has sensory input, motor output
- carries out processing of info / no
76
What is the main long fibre in a neurone called?
axon
77
Eugenol can be used to reduce pain. Suggest an explanation for how eugenol affects the movement of calcium ions and reduces pain.
Given that Eugenol inhibits sodium ion movement. (6 marks)
- reduced Ca2+ enter presynaptic knob
- due to V gated Ca2+ channels not opening
- fewer vesicles fuse with presynaptic membrane
- less neurotransmitter released into synaptic cleft
- less NT binds to receptors on post-synaptic knob
- less Na+ channels open
- less depolarisation
- threshold intensity less likely to occur
- pain not being sensed as impulse before entering CNS
78
Why is there no proteins in the filtrate of bowman’s capsule but other ions are found?
Proteins are too big to pass through
Other ions are small enough to pass through
79
How is glucose selectively reabsorbed?
By active transport!!
80
Explain why a higher light intensity is required to produce an action potential to bipolar cells connected to cone cells than rod cells? (3 marks)
- more rod cells connect to one bipolar cell; one cone cell connects to bipolar cell
- so spatial summation occurs
- so depolarisation occurs in bipolar cell
- rod cells have more rhodopsin, that is very sensitive to light
81
What is the condition for production of action potential in postsynaptic neurone?
When EPSP > IPSP
So enough sodium ions enter neurone
82
How are calcium ions taken up in cells?
Facilitated diffusion through **channel proteins**!!
