nervous system Flashcards
what are the 2 main regulatory systems
central nervous system
hormonal ysystem
what type of singalling is used in nervous vs hormonal control
nervous = electrochemical
hormonal = chemicals
what is the general structure of a neuron
dendrites attached to a cell body
follows in to the axon
reaches axon terminals
how long can an axon be
1mm - 1m
explain the route of an action potential in a neuron
input zone receives incoming signal,
trigger zone initiates action potential,
conducting zone conducts action potentials over long distance,
output zone releases neurotransmitter that influences other cells (including other neurons)
how many neurons can be attached to one neurons output zone
up to 1000
what is the resting potential of all cells
-70mV
what is depolarisation
decrease in potential, membrane is less negative
what is repolarisation
return to resting potential after depolarisation
what is hyperpolarisation
increase in potential, membrane more negative
how does a change in membrane potential actually occur
changes immediately surrounding the membrane trigger voltage-gated ion-channels to open
why does hyperpolarisation occur
potassium channels take longer to close
what happens if the trigger on the membrane is stronger or longer
more channels open so there is more depolarisation
how does depolarisation spread to neighbouring inactive areas
local current flow
what triggers an action potential
graded potentials with significant magnitude
what are the stages of an action potential
- resting potential with channels closed
- Na+ channels open at the threshold, positive feedback
- rapid influx of Na+ into cell
- at peak, Na+ inactivation gate closes and K+ channels open
- efflux of K+ out of cell
- Na+ channels reset
- brief period of hyperpolarisation
- K+ channels shut, returning to resting potential
what is the purpose of the refractory period
stops Na+ opening again
limiting number of action potentials
ensures directionality
what fixes the hyperpolarisation
ATPase pumps
what is the name for unmyelinated areas along the axon and what happens to the action potential as a result
nodes of Ranvier - action potential must jump along these nodes as cannot be transmitted where myelin sheath is present
what is the name for the type of conduction that occurs as a result of the myelin sheath and nodes of Ranvier
saltatory conduction
what are 2 types of synapse
electrical and chemical
what is the speed of transmission at electrical synapses
rapid
what stages happen at a synapse
- action potential reaches axon terminal of presynaptic neuron
- Ca+ enters synaptic knob
- neurotransmitter is released by exocytosis in to synaptic cleft
- neurotransmitters bind to receptors on chemical-gated channels on membrane of postsynaptic membrane
- binding of neurotransmitter opens the channels required and potential is transmitted to next neuron
what 2 things can a neuron attach to
another neuron or muscle
what is centralisation
nerves being central to the body
what is cephalisation
prescence of brain-like tissue
what are the only animals with no nerves or nervous system
sponges
centralisation and cephalisation in the sea anemone
none
do have nerve nets
centralisation and cephalisation in sea stars
no cephalisation
some centralisation due to radical symmetry
centralisation and cephalisation in flatworms
centralisation with ladder like CNS
some cephalisation - brain at anterior
centralisation and cephalisation in the earthworm
true brain (cephalisation) attached to ventral nerve cord (centralisation)
centralisation and cephalisation in the squid
well centralised nervous system dominated by a large brain (compared to relative size)
what does the position of the brain in squid show about cephalisation evolution
independently evolved from mammals as squid brain is wrapped around their tracheae
what do afferent neurons transmit
signals from sensory receptors to CNS
what do efferent neurons transmit and what chemicals do they use to do so
information from CNS to effectors using noradrenaline and acetylcholine
what do interneurons transmit
information between afferent and efferent neurons
what is the most common neuron type
interneurons (>90%)
what types of neuron do not have dendrites
afferent neurons
what is the role of the autonomic nervous system
regulate involuntary physiological processes
what are the 2 pathways of the autonomic nervous system
sympathetic and parasympathetic
what is carried out by the parasympathetic nerves
‘rest and digest’ activities
constrict pupils, slow heartbeat, stimulate activity of stomach and intestines, inhibit release of glucose
what is carried out by the sympathetic nerves
‘fight or flight’
diate pupils, increase heartbeat, relax airways, inhibit stomach and intestine activity
what 2 chemicals are secreted during the sympathetic pathway
epinephrine and norepinephrine
where are norepinephrine and epinephrine secreted from
adrenal medulla
what 2 receptors are triggered by acetylcholine
nicotinic and muscarinic receptors
what receptor is triggered by norepinephrine and epinephrine
andrenergic receptors
number of neurons from origin in CNS to effector organ in the autonomic nervous system
two neuron chain (preganglionic and postganglionic)
number of neurons from origin in CNS to effector organ in the somatic nervous system
single neuron (motor)
what is innervated in autonomic nervous system
cardiac muscle, smooth muscle, exocrine and some endocrine glands
what is innervated in the somatic nervous system response
skeletal muscle
what neurotransmitter is present in somatic nervous system
acetylcholine
what neurotransmitters are present in autonomic nervous system
acetylcholine = parasympathetic
norepinephrine = sympathetic
