nervous and hormonal

• hormonal coordination makes up the endocrine system and have differing response times. hormones are impulses sent from glands that target specific cells.
• response of the nervous system is instantaneous and controlled by central nervous system. It is made up of specialised nerve cells and neurones.
• information is transported through series of electrical impulses along a neurone.
• the nervous system and endocrine system work separately to each other
• neurones are specialised cells that generate and transmit nerve impulses.
• sensory neurone transmits nerve impulses from receptor to relay neurone. it is one long dendron and one axon.
• relay neurone transmits impulses between other neurones. they have short processes
• motor neurone transmits impulse from relay neurone to an effector. have a long axon and short dendrites.
• cell body contains the nucleus and organelles. has large amounts of RER needed to make proteins and neurotransmitters. ribosomes group together to form Nissl granules which make neurotransmitters.
• dendrons are extensions from cell body which sub divide into smaller branched fibres called dendrites. they carry impulses away from cell body.
• axons are single long fibres that transmit impulses away the cell body
• schwann cells surround axons protecting it and providing electrical insulation. they carry out phagocytosis (remove cell debris) and play apart in nerve regeneration. they wrap themselves around the axon many times so their membrane is wrapped around axon in tight spiralled layers.
• myelin sheath is made up of phospholipid membrane of Schwann cells which covers axon. it is rich in lipid myelin.
• node of Ranvier are constrictions between Schwann cells where their is no myelin sheath.
• axon terminals are where the axon divides into branches where synapse arise.
• a nerve impulse is a self propagating wave of electrical activity that travels along the axon membrane. it is a temporary reversal of the electrical potential difference across axon membrane. the reversal is between resting and action potential.
• nerve impulses are recorded and measured with cathode on oscilloscope and pair of microelectrodes. they measure the speed and magnitude at which impulse and can analyse their patterns. it measures potential difference across axon membrane
• electrical charge of a nerve impulse = 50mV
• resting potential = -70mV
• permanently open protein channels are open all the time to allow facilitated diffusion of Na and K ions
• voltage sensitive gates can be open or closed according to the concentration ions which results in voltage across the membrane. different gates will differ in size and or shape to allow ions of different shape and size to fit across.
• axon membrane is more negative inside than outside
• active channels like sodium potassium pump actively transport potassium ions into the axon and sodium ions out.
• during resting potential the membrane is said to be polarised
• how does axon membrane become polarised

  1. Na+ pumped out of axon and K+ in to the axon against concentration gradient by active transport by sodium potassium carrier proteins. this uses ATP
  2. 3 Na+ leave for every 2 K+ that move in
  3. some Na+ diffuse back into axon through open sodium channels
  4. K+ ions diffuse out of axon via open potassium channels
  5. membrane is more permeable to K+ than Na+ as there are more potassium channels open than sodium
  6. the outside of the axon is more positively charged than inside and is now polarised
• when a stimulus is detected by a receptor its energy temporarily reverses the charges on either side of the axon membrane.
• depolarisation changes permeability of membrane towards sodium ions.
• when a neurone transmits a nerve impulse it starts by becomes depolarised and the repolarises to reset resting potential