synapses, nervous system, reflexes Flashcards
explain how nerve impulses are transmitted between neurones
action potential arrives, depolarises pre synaptic neurone, if this action potential is large enough ca2+ voltage gated channels open and there is an influx of ca2+ ions this causes the vesicles filled with acetylcholine to fuse with the cell membrane, exocytosis occurs and acetylcholine enters the synaptic cleft and diffuses to the post synaptic neurone, it binds to the receptors this causes na+ channels to open and na diffuses in from the synaptic cleft if generator potential reaches threshold level it causes an action potential
what happens to the acetylcholine after its finished binding
acetylcholinesterase breaks it down into acetyl and choline these then go back into the neurone and fuse into another vesicle (acetyl and choline are reused)
excitatory synapse
depolarises the post synaptic membrane causing an action potential if threshold level is reached
inhibitory synapse
hyperpolarises the post synaptic membrane, preventing an action potential
spatial summation
multiple neurons converge release nerve impulses into one response, if GP reaches thresh L AP is produced
temporal summation
one neuron successively releases nerve impulses, GP reaches Thresh L AP produced
how is the nervous system split and what do each of the nervous systems do
CNS and PNS from which somatic and autonomic NS from which sympathetic and para sympathetic,
CNS brain spinal cord
PNS neurones
somatic NS conscious eg moving muscles
autonomic NS unconscious eg digestion
sympathetic NS fight or flight produces noradrenaline
parasympathetic NS rest and digest produces acetylcholine
hypothalamus
regulates homeostasis, body temp
pituitary gland
regulateD by hypothalamus secretes hormones
medulla oblongata
controls heart rate and breathing rate
cerebellum
controls posture and balance
cerebrum
controls voice, hearing and learning
