Nervous coordination and muscles

Question 1

what are the two main principles of coordination?

Answer 1

– the nervous system
– the hormonal system

Question 2

what is a mammalian motor neurone made up of?

Answer 2

– cell body
– dendrons
– axon
– schwann cells
– myelin sheath
– nodes of Ranvier

Question 3

what is the function of a sensory neurone?

Answer 3

transmit nerve impulses from a receptor to an intermediate or motor neurone. they have one very long dendron and carry impulses towards the cell body

Question 4

what is the function of motor neurones?

Answer 4

transmit nerve impulses from an intermediate or relay neurone to an effector

Question 5

what is the function of a relay neurone?

Answer 5

transmit impulses between neurones.

Question 6

how is the movement of ions across the axon membrane controlled?

Answer 6

– phospholipid bilayer
– channel proteins
– sodium-potassium pump

Question 7

what events cause the resting potential to be produced?

Answer 7

– sodium ions are actively transported out of the axon by the sodium-potassium pump
– potassium ions are actively transported into the axon by the sodium-potassium pumps
– the active transport of sodium ions is greater than that of potassium ions
– although both sodium and potassium ions are positive the outward movement of NA ions is greater than the inward movement of P ions
sodium ions begin to diffuse back naturally into the axon

Question 8

what events cause the action potential?

Answer 8

– at resting potential some potassium voltage-gated channels are open
– energy of the stimulus causes some sodium voltage-gated channel in axon membrane to open
– as sodium ions move in more sodium ion channel open
– once action potential is more the 40mv sodium voltage gates close and potassium ones open
– more potassium ions open and they diffuse out so repolarisation starts
– the outwards movement of potassium ions causes repolarisation

Question 9

how does an action potential pass along an unmyelinated axon?

Answer 9

– at resting potential the concentration of sodium ions outside the axon membrane is high relative to inside overall conc of ions is higher on outside making it positive (polarised)
– stimulus causes sudden influx of sodium ions and reversal of charge on axon membrane occurs
– the localised electrical currents established by the influx of sodium ions cause the opening of sodium voltage-gated channel. This influx causes depolarisation
– depolarisation moves along the membrane
– repolarisation of the axon occurs

Question 10

what are the factors which affect the speed at which an action potential travels?