BIO PSYC - NEURONS & NTRS Flashcards
What are the main 3 functions of the nervous system?
- to collect information about eh environment (internal and external)
- to process and integrate theat information
- to send out signals to actuations upon that information
What are the tyo types of nervous system cells
- neurons
- supporting cells (glia and glial cells)
List 5 organelles in a neurone and their function:
- dendrite - recieve the signal
- cell body or soma - metabolic centre of the neuron
- axon - thin fibre which conveys the impulse
- myelin sheath = made by shwann cells is an insulating material with breakes calles nodes of ranvier
- axon terminal - transmits the signal on
What are afferent neutrons? (sensory)
- transmit information about the external and internal body to the CNS
- communicate information about
pain
temperature
hunger
touch/ pressure
What are efferent neurons (motor)
- transmit information FROM the CNS
- carry signals to act to muscles, skin, glands
allows us to move, sweat and eat
What are interneurons?
- connect various neurons within CNS to form complex networks
- integrates information recieved from afferent neurons
Random facts about neurons:
- adult human brain contains 100 billion neurons
- cell body ranges from 0.05mm to 0.1mm in mammals
- the length of an axon can be a meter or more
What is Glia?
- helper cells
- DO NOT transmit information
- smaller and more numerous that neurons (90%)
- help protect, feed and insulate neurons
What is an impulse?
- the way in which messages are sent along neurons
- reception, conduction and transmission of electrochemical signals
- information passes down the axon
- into the axon terminal
- over the synapse
- into the dendrites of the next neutron
What are the three substances taht are key in neuronal transmission?
- sodium
- potassium
- calcium
What is resting potential?
At rest
- no impulse
- positive on the outside (respect to inside)
- more sodium ions outside the axon than potassium
- there is a concentratiuon gradient
- sodium trying to get in
- potassium trying to get out
- some seepage of ions
- this is maintained by a sodium potassium pump
- requires energy
- moves sodium out and potassium into the axon
- ‘artificial’ concentration gradient
- membrane potential in the axon (-70mV)
- net negative charge inside the axon
- membrane said to be polarised
- membrane potential changes when the neuron fires
- causes an action potential
What is depolarisation
- whena. neuron receives a signal it causes sodium channels in the axon to open
- ## sodium ions flow in and the inside of the axon becomes positive with respect to the outside
What is repolarisation?
- sodium channels close and potassium channels open
- potassiumions flow out - movement swaps the polarity
- outside becomes more positive with respect to the outside
What is hyperpolarisation?
- potassium channels open and close very slowly
- too much potassium diffuses out
- the membrane potential drops below -70mV
- this is corrected by the sodium and potassium leaking through the membrane
(membrane back to resting potential) - hyperpolarisation (the refractory period)- no other action potential can occur
Explain the all or nothing law:
- if a stimulus is above -55mV threshold, a neuron will fire
- strength of action poytential is dependent of the intensity of the stimulus that initiated it
How do we gauge stimulus intensity?
- a neuron firing at a faster rate indicates a stronger intensity stimulus
- numerous neurons firing simultaneously or in rapid succession would also indicate a stronger stimulus
How do we determine different sensory inputs?
Different type sof sensory receipt
- smell
- taste
- vision
- auditory
- temperature
- mechanical
- internal
these detect different changes in the environment, but the resulting action potential is always the same
How do anaesthetic drugs work?
- novocain ans xylocaine attatch to the sodium ion channels preventing the sodium ions from entering
- this stops action potentials
- receptions are screaming PAIN but the message is not transmitted
What are myelinated neurons?
- glial cells form myelination
- action potential only occurs at the nodes of ranvier
- faster impulse as it jumps from one node to the next
What are synapses?
- the impulse needs to pass out of the one neurone to another
- over the synaptic gap or cleft
- done via electrical synapses or chemical synapses
What are electrical synapses?
- two neurons are connected by small holes called gap junctions
- allows the action potential to pass from one neuron to the other
What are chemical synapses?
- they have a gap for the action potential to jump
- when action potential reaches the terminal end of the pre synaptic neuron calcium channels open
- calcium flows in
- the calcium causes the synaptic vesicle to. move to and merge with the pre synaptic membrane
- these neurotransmitters fuse with the receptor cells in the post synaptic membrane
What are neurotransmitters?
- important in synaptic transmission
- they are released from the axon by action potentials
- chemical messengers that carry, boost and balance signals
- many different types
- could influence heart rate, sleep, apetite and mood
What are excitatory neurotransmitters?
- increase the likihood that the neuron will fire an action potential
e.g noradrenaline
- attention/ arousal
