nervous coordination and muscles
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How do nerve cells stimulate their target cells
by secreting neurotransmitters directly on to them
what does secreting neurotransmitters directly on to target cells result in
rapid communication between specific parts of an organism
response produced by nerve cells
-short-lived -restricted to a localised region of body
how does hormonal system transport chemicals (hormones)
in blood plasma to target their cells
what do target cells have
specific receptors on their cell surface membrane
what does a change in conc of hormones stimulate
specific receptors on cell surface membrane
results of hormonal system
-slower -less specific form of communication between parts of an organism
response of hormonal system
long lasting widespread
cell body
-contains usual organelles -RER > production of proteins and neurotransmitters
what are neurones specialised to do
specialised cells adapted to rapidly carry electrochemical changes (nerve impulses) from one part of body to another
dendrons
-extensions of cell body which divide into dendrites -carry nerve impulses TOWARDS cell body
axon
single long fibre that carries nerve impulses away from cell body
Schwann cells
-surround axon > protecting it and providing electrical insulation -carry out phagocytosis -play part in nerve regeneration -wrap themselves around axon many times > layers of their membrane build up around it
myelin sheath
-made of membranes of Schwann cells -membranes are rich in lipid (myelin)
what are neurones with myelin sheath called
myelinated neurones
nodes of Ranvier
-constrictions between adjacent Schwann cells where there’s no myelin sheath
um of constrictions of nodes of Ranvier
• 2-3 um long -occur every 1-3mm in humans
sensory neurone
-transmit nerve impulses from receptors to an intermediate or motor neurone
structure of sensory neurone
-1 dendron thats often very long -carries the impulse towards cell body and 1 axon that carries it away from cell body
motor neurone
transmit nerve impulses from an intermediate or relay neurone to effector
structure of motor neurones
-long axon -many short dendrites
intermediate neurone
-transmit impulses between neurones eg sensory > motor -have numerous short processes
define resting potential
potential difference across an axon membrane at rest (inside -65mV compared with outside)
How does phospholipid bilayer control Na+ and K+ across axons membrane
-phospholipid bilayer of axons plasma membrane prevents Na+ and K+to diffuse across it