Topic 9 Chemical Control in Animals Flashcards
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)
- adrenaline binds to receptors on membrane / cell surface
- second messenger cAMP involved
- activates glycogen phosphorylase
- glucose diffuses out of cells
Compare the mechanisms used in hormonal and nervous coordination in mammals. (3 marks)
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
Given thyroxine is able to enter the cell,
How does thyroxine increase the secretion of adrenaline from adrenal glands? (4 marks)
- can enter so it’s hydrophobic
-thyroxine binds to receptors - enters the nucleus
- activates transcription factor / stimulates transcription
- increased protein synthesis
- synthesise more adrenaline
What are endocrine glands?
Releases hormones
What are exocrine glands?
Secreting digestive juices like enzymes
What is the definition of hormones?
Chemical messengers released by glands travelling via blood towards target cell by binding complementary receptors
Which parts of the brain will help to coordinate endocrine functions?
Hypothalamus and pituitary gland
What are the 2 types of hormones?
protein based and lipid based
What are examples of protein based hormones?
Adrenalin
melatonin
FSH
ADH
LH
What are examples of lipid based hormones?
steroid hormones like
oestrogen
Where are steroid (lipid) hormones derived from/made of?
cholesterol
Where are protein based lipids derived from/made of?
multiple amino acid chain
tyrosine and tryptophan
Describe the process of hydrophilic hormones
- 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
Do cells have the same genes and how do they have different functions?
All have the same 46 chromosomes
but depends on what genes are switched on and off
hence gene expression
What do transcription factors do?
promote transcription and translation
Describe the process of hydrophobic hormones causing synthesis?
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
What are the 3 types of neurons?
Sensory
Relay/interneuron
Motor
Which 2 systems are the mammalian nervous system composed of?
central and peripheral
What is the central nervous system made up of?
brain and spinal cord
What are 2 systems in the peripheral nervous system?
- autonomic
- voluntary (under conscious control)
What is the structure of the spinal cord?
- 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
What are the 2 main divisions of autonomic nervous system?
- sympathetic (arousing)
- parasympathetic (calming)
act antagonistically
Describe the sympathetic nervous system.
- usually stimulates effectors (FIGHT OR FLIGHT) (s-s)
- neurotransmitter nonadrenaline
- ganglia located near CNS
Describe the parasympathetic nervous system
- usually inhibits effectors
- eg neurotransmitter acetylcholine
- ganglia located far from CNS
REST & DIGEST
What is the location and main function of the medulla oblongata?
brain stem
control breathing and heart rate
What is the location and main function of the cerebellum?
lower back, behind spinal cord
controls balance and coordination of movement
what is the location and main function of the cerebrum?
front and top
initiates movement
What is the location and main function of the hypothalamus?
above pituitary gland
temperature regulation and osmoregulation
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
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
what do sensory neurons do?
transmit impulses from receptors
what do motor neurons do?
transmit electrical signals from CNS to glands of body
what do relay neurons do?
transmit electrical impulses between motor and sensory neurons
What is the resting potential of nerve cells?
-70mV
What is potential difference?
When there’s a difference in charge
What does it mean by polarised in sensory receptors?
When a neurone has resting potential
What is the threshold value for sensory receptors?
What then happens?
When potential difference at -50mV
Sodium ion channels open
What is the refractory period in sensory receptors?
Time between one action potential and when another action potential can occur
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
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
Can action potential increase in size?
NO! Only frequency.
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
What happens in repolarisation?
Sodium ion channels shut
Potassium ion channels open, potassium ions facilitated diffuse out
+ hyperpolarise
Why does hyperpolarisation happen?
Action potential can only travel in one direction
Prevent immediate stimulation again
Refractory period
What produces myelin sheath?
Schwann cells
What is between myelin sheath?
Nodes of Ranvier
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)
What is the condition without myelin sheath or demyelination?
Multiple sclerosis
What is the synapse called?
Synaptic cleft
How does action potential travel between two neurones?
- Action pot travels down pre-synaptic knob
- trigger voltage gated Calcium ion channels to open
- Calcium ions cause vesicles to exocytose (active)
- release vesicles (that contain neurotransmitters [NT])
- NT diffuse down the conc grad across synaptic cleft
- Attaches to complementary receptors on post-synaptic membrane - that is attached to sodium channels
- Triggers CHEMICALLY gated sodium ion channels to open
- sodium ions facilitated diffuse into post synaptic knob = depolarisation
- EPSP created
- Neurotransmitters broken down using enzymes into products
- Products reabsorbed and recycled at presynaptic knob
What is EPSP
Excitatory post-synaptic potential
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
What enzyme is used to digest acetylcholine, and what are the products?
Acetylcholinesterase
Into Acetylcholine-CoA + choline
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 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
Which region of the brain only controls breathing and heart rate?
medulla oblongata
What type of neurone releases acetylcholine and what is the effect of it?
- parasympathetic neurone
- lowers HR (rest and digest)
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
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
What is the effect of inhibitory drugs? (3 marks)
- Blocks voltage gated sodium ion channels
- so no movement of sodium ions into neurone
- so prevents depolarisation/action potential
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
Is nicotine, Lidocaine and cobra venom excitatory or inhibitory respectively?
excitatory
inhibitory
inhibitory
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)
What do IPSPs do?
- open up K+ ions
- lead to hyperpolarisation
- K+ ions diffuse out of neurones
- less likely to pass on action potential - since potential difference getting more -ve
What is the effect of nicotine?
- competitive inhibitor to acetylcholine (v similar effects)
- triggers action potential
- rest and digest effect
What are 3 factors affecting speed of neurone transmissions?
- temp
- diameter of axon
- presence of myelin sheath
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)
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)
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
Why is there a refractory period?
voltage gated Na+ channels are closed
so cant depolarise
As Na+ cannot diffuse into neurone
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)
What is the effect of oestrogen on transcription?
- some cells have oestrogen receptors (ER)
- have DNA binding site, blocked by inhibitor molecule
- Oestrogen binds to ER after diffusing into cell
- activated ER acts at TF
- binds to specific DNA sequence in promoter region - to promote or inhibit
