Chapter 13- Neuronal Communication Flashcards
How sensory neurone and motor neurone are similar?
Both have
- dendrites
- an axon
- a cell body with nucleus
- myelin sheath covered with Schwann cells
Effect sweating will have on body?
- evaporation will decrease body temperature
- heat is taken from the body and used for evaporation
Why shivering during fever when normal body temp increases?
- the new ‘normal’ body temp has increased
- the body is using shivering to raise the temp of the internal environment
Explain vasodilation?
- results in more blood nearer to the skin surface
- will lose heat + body temp will decrease
Why pacinian corpuscle acts as a transducer?
-converts mechanical energy into electrical energy
Why does deformation of plasma membrane cause tip of neurone become more permeable to Na+?
-causes Na+ channels to open
All or nothing law?
-if stimulus is strong enough, threshold value reached and AP generated
How strength and intensity of stimulus is connected to the brain?
-high frequency of action potentials shows strong impulse
Clothes are first put on. Constant gentle pressure applied. After a short time, action potentials are no longer generated unless there is a change in pressure. Why?
-na+ channels remain open so resting potential is not reestablished
Role of synapses?
- Allow neurones to communicate
- ensure transmission in one direction only
- allows impulses from more than 1 neurone to be passed to a single neurone
- allows impulses from a single neurone to be passed to more than one neurone
Gap in neurones?
Node of Ranvier
Explain difference in speed of conduction of action potential along myelinated and non myelinated neurone?
- conduction faster in myelinated. Action potential can only occur where the VG Na+ channels are present
- ion movement can only take place at the gaps
- so saltatory conduction happens which is the action potential jumps from node to node
How acetylcholine is secreted?
Exocytosis
Part of neurone acetylcholine is secreted?
Synaptic knob
The effect that proteases may have on snare proteins?
- protease may hydrolyse the peptide bonds in snare proteins
- vesicles cannot fuse with CM + acetylcholine not secreted
Part of neurone where transmission of impulses is interfered?
- post synaptic membrane. Prevents attachment of neurotransmitters to its receptor
- pre synaptic knob. Prevents release of neurotransmitter or influx of Ca2+ ions
How resting potential established and maintained?
- sodium potassium pump uses ATP to actively move 3 Na+ out and 2K+ in neurone
- K+ ions diffuse out of leaky K channels
- fewer Na+ channels open
- VG Na+ channels closed
Order of polarisation?
Depolarisation
Repolarisation
Hyperpolarisation
What is -55mV?
Threshold potential
Relationship between strength of stimulus and resulting action potential?
- only stimuli that reach threshold potential will produce action potential
- when stimulated, action potential either occurs or not . All or nothing principle
- action potential is same size no matter how strong stimulus is
Gap between two neurones?
Synaptic cleft
How first neurone communicates with second neurone?
- neurotransmitter released from pre synaptic membrane
- diffuses across synaptic cleft
- attaches to receptors on post synaptic membrane
Importance of synaptic cleft?
- ensures movement of action potential is one direction only
- allows summation
- ensures that only stimulation that is strong enough will be passed on
Hormone that increases metabolic rate and so generates heat?
Adrenaline
Action potentials all have the same?
Magnitude
Function of Schwann cells?
- Schwann cells produce myelin sheath
- acts as an electrical insulator
- prevents depolarisation
- speeds up transmission of action potential as impulses jump from node to node. Saltatory conduction
How acetylcholine travels across synaptic cleft?
Diffusion
How synapses ensure transmission is only one direction?
- only pre synaptic neurone releases acetylcholine
- only pre synaptic neurone has Ca2+ channels
- only post synaptic membrane has receptors
Atropine similar shape to acetylcholine. How this prevents initiation of action potential?
- atropine competes with acetylcholine for receptor on post synaptic membrane
- prevents ACh binding
- na+ channels remain closed
- insufficient depolarisation is does not reach threshold potential
Why x is described as auto immune condition?
- attacked by body’s own immune system
- immune system recognises body cells as foreign
Why damage to some myelin sheath leads to loss of sensation?
-stops Saltatory conduction
-
Why increase in temp results in increased speed of conduction?
-more KE so ions diffuse across nodes quicker
What would happen if temp increased too much?
Channels and pumps denatured
What happens after action potential arrives at synaptic knob?
- calcium channels open
- Ca2+ ions diffuse in
- acetylcholine in vesicles
- vesicles move towards pre synaptic membrane
- vesicles fuse with membrane
- neurotransmitters released by exocytosis into synaptic cleft
Specialised cells in nose and tongue detect what stimuli?
Chemical
Where do sensory neurones transmit their impulses?
CNS
Where do motor neurones transmit impulses?
To effectors
How body detects that your finger has touched a pin?
- touching pin exerts mechanical pressure on skin
- pacinian corpuscle found within skin detects pressure
- pressure changes shape of pacinian corpuscle
- stretch mediated sodium channel in neurone membrane stretches. Channels widen
- Na+ ions diffuse into membrane
- generator potential created
- generator potential creates an action potential
- action potential transmitted along neurones to CNS
Hyperpolarisation?
When potential difference is lower than the resting potential
What would happen if refractory period didn’t exist?
-axon could be immediately depolarised after an action potential so action potential could travel in both directions
What would happen if VG Na+ channels couldn’t open?
- Na+ cannot enter
- prevents depolarisation of membrane
- prevents action potential being generated
- no release of neurotransmitter
Why non myelinated neurone transmits impulses more slowly?
- no nodes of Ranvier
- whole axon needs to be depolarised
CNS?
- brain and spinal cord only
- has coordinating role
PNS?
- role in sensing stimuli
- conduct impulses to and from CNS
- includes somatic/ autonomic/ sympathetic / parasympathetic
Describe function of Schwann cells?
- Schwann cells produce myelins sheath
- electrical insulator
- prevents depolarisation
- action potentials only occur at nodes of Ranvier
- impulse jumps from node to node. saltatory conduction
- speeds up transmission of impulses
Neurotransmitter for sympathetic NS?
noradrenaline
neurotransmitter for paraysmpathetic NS?
acetylcholine
events that occur after adrenaline reaches CMS?
- adrenaline binds to receptor in a complementry fit
- adenyl cyclase activated
- ATP convert to cAMP
- cAMP activates enzymes by altering 3D structure and phosphorylation
How having no. of steps in signalling pathway enables small no. of adrenalije to cause large effects?
- 1 molecule causes activation of many others
- e.g. 1 adrenaline -> many cAMP molecules
- this multiplying step is repated at every step
Which type of molecule can pass directly through CSM?
-Lipid soluble
Where acetylycholine receptors are found?
post synaptic membrane
Where is acetylcholinesterase found?
synaptic cleft
Sympathetic NS?
- short preganglionic neurone
- long post ganglionic neurone
- neurotransmitter: noradrenaline
- fight or flight
Parasympathetic NS?
- long pre ganglionic neurone
- short post ganglionic neurone
- neurotransmitter: acetylcholine
- rest or digest
- more blood flows to smooth muscle
Explain the difference in the speed of conduction of an action potential along myelinated and non-myelinated neurone.
- conduction faster in myelinated
- a.p. can only occur where the V.G NA+ channels are
- in myelinated: nodes of ranvier
- in non: total length of neurone
- myelinated have longer sections with no V.G Na+ channels present
- ion movement can only take place at gaps so a.p jumps from node to node/ saltatory conduction
How nervous system decreases heart rate?
-impulses along the vagus nerve in parasympathetic NS
