nervous system

CNS

receiving, transmitting and interpreting sigals from nerve impulses

• coordinate responses

brain + spinal cord, located down centre of body

PNS

cranial and spinal nerves

• lies outside CNS

neuron

nerve cell

dendrites

highly branched, receive signals from other neurons

neuron cell body

organelles + nucleus of neuron located here

axons

transmits signals to other cells, often longer than dendrites

synapse

junction/gap between cells

glial cells

nourish neurons + insulare the axons

motor neurons

• from spine outwards

• transmit signals to muscle cells (long axon, short dendrites0

interneurons

in CNS, connect sensory + motor neurons

reflex interneurons

short axon, short dendrite

interneurons to brain

short dendrite, long axon

sensory neurons

• input to spine, transmit information from sensors to brain for processing

• long dendrite, short axon

3 main types of neurons

sensory, motor, interneurons

somatic nervous system

part of PS → controls skeletal muscles (voluntary)

autonomic nervous system

part of PNS —> controls organs (sympathetic + parasympathetic) involuntary

sympathetic nervous system

fight or flight response; uses norepinephrine/noradrenaline as neurotransmittter

parasympathetic nervous system

maintains/establishes “normal” conditions in body; uses acetylcholine as neurotransmitter

cranial nerves

12 pairs; in head, neck, facial region, internal organs

spinal nerves

31 pairs; in specific body areas near the cns

membrane potential

(also called resting potential) - not sending any signals (between -60 and -80mV)

action potential

impulse as it moves along a neuron

arrival of the impulse

step 1 of neurotransmitter transmission

• electron movement of signal ends at axon bulb

• depolarization/repolarization events (Na+/K+ ions) carry signal

movement of ca2+ ions

step 2 of neurotransmitter transmission

• presynaptic membrane becomes permeable to Ca2+

• Ca2+ floods into axon bulb

• causes contractile filaments to shorten → vesicles drawn.to membrane

release of neurotransmitter

step 2 of neurotransmitter transmission

• neurotransmitters released through exocytosis into synapse

• active process (ATP needed)

• mitochondria are often in the region where it’s released

a neurotransmitter’s movement across the synapse

step 4 of neurotransmitter transmission

• neurotransmitter diffuses across the synaptic gap —> moves from high to low concentration

neurotransmitter: binding with receptors

step 5 of neurotransmitter transmission

• neurotransmitter received in post synaptic membrane by receptors (all or none response)

• remaining neurotransmitter (like ach) in synapse can be cleared by enzymes

neurotransmitter firing across a synapse

neurotransitter binds to receptors, causing na+ gates to open, impulse continues along dendrite (electrially)