13 - Neuronal Communication Flashcards
Why do we need coordination?
Cells have become specialised e.g. organs
Therefore groups of cells all have to work together
What is homeostasis
Functions of organs coordinated to maintain a constant internal environment
Compare nervous cell signalling and hormonal cell signalling
Nervous = neurotransmitters
Faster more targeted
Hormonal is hormones
Long distance
How do plants coordinate
No nervous system
Hormones e.g. auxins
What are stimuli
Changes to internal or external environment
How is the cell body of a neurone specialised to function
Nucleus and cytoplasm
Lots of endoplasmic reticulum And mitochondria for production of neurotransmitters
What is the role of dendrons
Short extensions, divide into dendrites
Transmit impulses towards cell body
What are the structure and role of axons
Transmit impulses away from cell bodies
Singular elongated Nerve fibres
What are the three types of neuron
Sensory
Relay
Motor
What is the structure of a sensory neuron
One dendron one axon
So body in eyeball shaped form in centre
What is the structure of a relay neuron
Many short axons and neurones
What is the function of a relay neuron
Transmit between neurons
What is the function of a motor neurone
Transmit impulses to an effector e.g. muscle or gland
What is the structure of a motor neuron
One long axon many short dendrites
Cell body at end of axon
What is myelin sheath and what is its role
Many layers of plasma membrane made from Schwann cells
Acts as an insulating layer to transmit impulses faster
What are gaps in Mylan sheath called and what are their roles
Node of ranvier
Signals jump over these gaps speeding up transmission
What are the features of sensory receptors
Specific to one type of stimulus
Acts as transducers – convert stimulus into nerve impulse called generator potential
What are the four types of sensory receptors
Mechanoreceptor
Thermoreceptor
Chemoreceptors
Photoreceptor
What is the stimulus for mechanoreceptors. Give an example.
Pressure and movement
Skin
What is the stimulus for thermoreceptors. Give an example.
Temperature
Younger
What is the stimulus for chemoreceptors. Give an example.
Chemicals
Nose
What is the stimulus for photoreceptors. Give an example.
Light
Eye
What is the role of the pacinian corpuscle
Detects mechanical pressure
Deep in skin in joints
Describe the process of a action potential in the pacinian corpuscle
Neurone has resting potential Pressure acts as stimulus Stretch mediated sodium ion channels open Influx of positive ions depolarises so Action potential passes along neurone
How are resting potentials created
Sodium ions actively transported out of axons
Potassium ions actively transported into axon
Three sodium out, two potassium in
Uneven balance creates electrochemical gradient
Sodium ions diffuse in potassium ions diffuse out
However sodium ion channels closed
More positive charge outside (-70mV inside)
How is an action potential created
Sodium ion voltage gated channels open
Sodium ions diffuse down electrochemical gradient
Creates positive feedback and more gates open
Sodium channels shut and potassium builds up inside axon
Describe how repolarisation works
Potassium ion voltage gated channels open
Lets positive eyes out to get back to -70mV
What is the refractory period
Period of hyperpolarisation
Voltage gates both closed
There can be no new action potential
Stops overlapping signals and prevent signals travelling backwards
Describe how action potential is propagated
Sodium ions moving in are attracted to negative charge and diffusion gradient
More positive charge triggers voltage gated channels to open up further down neurone
What is saltatory conduction
Action potentials cannot be created in myelinated areas
Only happen it node of ranvier
Leapfrog
quicker more Efficient
What are the two types of neurotransmitters
Excitatory
Inhibitory
What do excitatory neurotransmitters do. Give an example
Trigger action potential of threshold is reached
EG acetylcholine
What do inhibitory neurotransmitters do. give an example
Prevents action potential being reached
E.g. gaba
Explain how an action potential causes the release of neurotransmitters into a synaptic cleft
Action potential reaches presynaptic knob
Depolarisation causes voltage gated calcium ion channels open
Calcium ions diffuse into presynaptic knob
Causes cytoskeleton to move vesicles, fuse with membrane, releasing neurotransmitters via exocytosis
Explain how neurotransmitters in a synaptic cleft cause the propagation of an action potential
Neurotransmitters diffuse across synaptic cleft
Bind with specific receptor on postsynaptic membrane
Causes sodium channels to open, sodium ions diffuse in, causing action potential
Impulse propagated
Explain what happens to the neurotransmitters after binding to receptors on postsynaptic membrane
Broken down by enzymes
Products taken back to presynaptic knob to be recycled into new neurotransmitters
This also prevents a response from happening again
What are the two systems of structural organisation in neuronal communication (_NS and _NS)
Central nervous system
Brain and spinal cord
Peripheral nervous system
All neurons connected to central nervous system (sensory and motor)
What are the two systems of functional organisation
Somatic nervous system
Conscious control
Automatic nervous system
Subconscious control – works constantly
What are the two subgroups under automatic nervous system? When would they be used? Name a NT for each.
Sympathetic
Fight or flight
Noradrenaline
Parasympathetic
Relaxing responses
Acetylcholine
How is the brain protected
Meninges and skull
What does the cerebrum do
Controls voluntary actions
Learning memory personality conscious thought
What does the cerebellum do
Controls unconscious functions
Posture, balance, involuntary movement
What does the medulla oblongata do
Controls automatic control
Breathing rate, heart rate, coughing, swallowing
What does the hypothalamus do?
Regulatory centre
Temperature, water balance, hormones, blood plasma
What does the pituitary gland do?
Stores and releases hormones
What does the corpus callosum do
Joints to hemispheres of the brain together
What is the structure of Myosin
Globular, hinged heads
Binding site for actin and ATP many many tails form the filament
What is the structure of actin
Have binding sites for Myosin
Blocked by tropomyosin, held in place by tropinin
Describe the steps in the sliding filament model
Calcium ions cause troponin to turn, move tropomyosin out of the way, expose binding sites
Myosin head binding drives actin forward
ATP binds to myosin causing it to detach from Actin
ATP hydrolysed to ADP providing energy for myosin head to move backwards,
binds to actin further down ADP releases
What is the dark bit made up of in the sliding Filament model?
Layers of myosin and actin, length of Myosin
What is the H zone
Lighter banned within dark band where actin has gaps
What is the z-line
Where actin cross links are
What is the sarcomere
Area between two adjacent z-lines
What are the three types of muscle
Cardiac
Smooth
Skeletal
What are three ways of maintaining an ATP supply
Aerobic respiration
Anaerobic respiration
Creatine phosphate
State the difference in arrangement between skeletal, cardiac and smooth muscle
Skeletal – regular arrange so muscle contracts in One Direction
Cardiac - cells branch and interconnect resulting in simultaneous contraction
Smooth – no regular arrangement
State the difference in contraction speed of skeletal cardiac and smooth muscle
Skeletal – rapid
Cardiac – intermediate
Smooth – slow
State the difference in striations In skeletal, cardiac and smooth muscle
Skeletal – striated
Cardiac – specialised striated
Smooth – non-striated
