nervous communication Flashcards
outline the PNS and CNS
CNS - brain and spinal cord
PNS - relays information from brain to the body
gives some roles of the parasympathetic nervous system
constrict pupils and airways, slow down heart rate and stimulate stomach activity, contract bladder, promote reaction of genitals
what does thr sympathetic nerves do
dilate pupils, increase heart rate, relax airways, inhibit stomach activity, relax bladder and promote contractions/ejaculation of the genitals
what are neurones
nerve cells that transmit information in the form of an electrical impulse, an impulse is activated in response to a stimulus leading to the activation of an effector such as a muscle or a gland.
what are the three types of neurones
sensory - one dendron and one axon. they take impulses from the receptor to the relay neurone or the brain.
relay - transmit impulses between neurones and have one axon and many dendrons. no myelin sheath.
motor neurones - transmit impulses from the brain to the effector, one long axon and many short dendrons.
what does myelinated mean
schwann cells secrete a fatty acid layer known as myelin sheath which covers the axons and increases the rate of impulse transmission known as SALTATORY CONDUCTION
What is multiple sclerosis
autoimmune disease where WBC attacks myelin sheath as it is recognised as being non-self. this slows down the impulse or takes it to the wrong place. it leads to fatigue, uncoordination, visual problems, slower reaction time and speech problems
give some details including examples of sensory receptors
they are specific to particular stimulus’
they act as transducers and convert a stimulus into an electrical impulse
ie mechanoreceptors - Pacinian corpuscle.
what is the Pacinian corpuscle. how does it work
a sensory receptor that responds to pressure and movement found in the skin and joints.
how do synapses in the
How are local currents in the neurone generated
by the sideways movement of sodium ions towards areas of lower conc after an influx
what causes hyperpolarisation at an inhibitory synapse
influx of Cl- ions, accompanied by movement of K+ ions out of the membrane
which phase describes how several presynaptic neurones release enough NT to exceed the threshold value of the postsynaptic neurone
spatial summation
which oragnelles are found in abundance in the presynaptic bulbs so that NT can be produced
mitochondria and RER
synapses allow convergence and divergence. what does this mean
- convergence is when impulses from more then one neurone are passed to a single neurone.
divergence is when impulses from a single neurone are passed to multiple neurones.
