peripheral nervous system Flashcards
What is the central nervous system
brain and spinal cord
what is the peripheral nervous system
everything but brain and spinal cord
somatic vs autonomic
both in peripheral, somatic-voluntary,
autonomic-involuntary
two subsections of autonomic
sympathetic - fight +flight
parasympathetic - rest+digest
what does sensory system contain
different receptors and sensory neurons, heads in CNS so afferent
what does motor system do
conducts impulses from cns to muscles and glands so efferent
segmental reflex definition
only in one segment of the spinal cord - dont involve brain (no selection of motor response). stimulus detected by sensory nerve - passes through sensory ganglion - enters dorsal horn of spinal cord - synapse on motor neurone in ventral grey matter - motor neurone causes response in motor organ
ganglion definition
collection of neuronal bodies found in pns, synaptic relay stations
difference between dorsal and ventral
dorsal is top, sensory comes in = afferent
ventral is bottom, motor goes out = efferent
grey vs white matter
grey matter contains cell bodies
white matter contains pathways in specific anatomical places
what does cell body contain
nucleus= soma = perikaryon
what is a nissl body
rough er that contains RNA and ribosomes. produces and secretes protiens
what is the axon hillock
connects axon to cell body and generates action potential
define refractory period
time following an action potential where a cell is unable to generate another due to hyperpolarisation of cell membrane
absolute vs relative refractory period
absolute = interval during which another action potential cannot be initiated no matter how big the stiumulus is, as all na channels are inactivated
relative = interval during which initiation of second action potential is inhibited but possible due to some na channels still activated and increased k conductance after hyperpolarisation
saltory conduction
impulse jumps from one node of ranvier to another as myelin sheath blocks entry of na ions, conduction is quicker
4 types of fibres
a, a delta, b and c
difference in types of fibres a, a delta and c
a - large, myelinated = fast transmission, touch and pressure
a delta - small, lightly myelinated = pain transmission
c - small, unmyelinated = slow transmission, sensory and autonomic motor neurones = inflammatory pain
what causes exocytosis of neurotransmitter
influx of ca ions in the presynaptic neurone
what is a neuromuscular junction
synapse between neurone and muscle, muscle membrane starts off slightly more negative
differences between nmj and neurone synapse
skeletal muscle membrane starts off more negative, action potential is slower in muscle fibre as goes through whole muscles rather than just along neurone surface causing muscle to contract. different structure of ca channels in muscle to be released in muscle centre to cause muscle contraction
what effects conduction velocity
fibre diameter
myelination
temperature
what is a synapse
junction between 2 neurones which causes an electrical signal to be passed on due to a chemical transmission
what are the 3 types of ‘pre-synaptic’ calcium channels
l-type, n-type and t-type
blocked by several types of toxins
l-type = main type (slow release - long lasting activation length so higher voltage)
n-type= never terminals and dendrites on neuroendocrine cells
t-type = low voltage but quick activated
order of synapse happenings
1) Ca intake causes acetylcholine to be packaged into vesicles
2) vesicles leave pre-synaptic neurone by exocytosis
3) acetylcholine diffuses across synaptic cleft and bends with post-synaptic membrane
4) causes action potential in post synaptic membrane
5) enzyme breaks down neurotransmitter into choine
6) choline is reuptaken into presynaptic neurone
7) CAT (choline acetlytransferase) remakes acetylcholine
what are the postsynaptic receptors
complex, multi-unit trans-membrane protiens with a central pore. pore diameter is altered when the transmitter binds to receptor pore changes
what are ionotropic receptors
ligand-activated ion channels, undergo a change in shape when neurotransmitter binds causing channel to open. can be excitatory or inhibitory effect depending on ions that can pass through the channel + concentrations inside/outside cell
what is the effect of too much K on membrane potential
hyperkalaemia - cuses depolarisation (more positive), resting membrane potential is closer to threshold so neurons are more excitable = tremors
what is the effect of toolittle K on membrane potential
hypokalaemia - causes hyperpolarisation (more negative) resting membrane potential further from threshold causing skeletal muscle weakness
