nervous system

Question 1

what’re the features found in all neurones?

Answer 1

-axon-transmit nerve impulses
-dendrites-form connections with many other neurones
-cell body-contains nucleus and other cellular structures
-axon terminal-has many nerve endings, the nerve endings at the axon terminal allow neurones to connect and receive impulses from other neurones, forming a network easy for easy communication

Question 2

what is the only place where relay neurones are found?

Answer 2

entirely within the CNS

Question 3

relay neurone structure

Answer 3

-short neurones with axons, cell bodies and highly branched dendrites
-generally not myelinated

Question 4

sensory neurone structure

Answer 4

-dendrites attached to receptor cell
-a cell body that branches off in the middle of the axon
-dendron connects axon terminal to cell body/delivers electrical impulse to the cell body
-the section of the NEURONE that connects the cell body to the CNS is the axon

Question 5

motor neurone structure

Answer 5

-large cell body at one end which lies within the spinal chord or brain
-many highly branched dendrites
extending from the cell body, providing many connections with the axon terminals of other neurones

Question 6

stimulus-effector chain of response

Answer 6

-receptor cell detects change in environment/stimuli
-nerve impulses travel along sensory neurones to the cns
-the cns acts as a coordination centre for the impulses that arrive from the receptors determining which part of the body need to respond and sending out a new set of impulses along motor neurones
-motor neurones send out impulses to the effectors to bring about a response

effectors could be glands of muscles

Question 7

circular muscles

Answer 7

contract, constricting the pupil

Question 8

radial muscles

Answer 8

contract dilating the pupil

Question 9

antagonistic pair of muscles

Answer 9

when one set of muscles contracts, the other relaxes

a muscle pulls in one direction at a joint and the other pulls in the opposite direction

Question 10

bright lights sequence of events

Answer 10

bright light-LIGHT RECEPTORS in eyes-sensory neurone-CNS-motor neurone-circular muscles in iris

contraction of circular muscles in the iris causes the pupils to constrict
this limits the amount of light entering the eye
prevents damage to the retina

Question 11

low light sequence of events

Answer 11

low light-light receptors in the eyes-sensory neurone-CNS-motor neurone-radial muscles in the iris

contraction of radial muscles in the iris causes the pupil to dilate
this maximises the amount of light entering the eye, improving vision

Question 12

different states of membrane potential across a neurone cell surface membrane during impulse transmission

Answer 12

-resting potential
-action potential

Question 13

when is a membrane polarised

Answer 13

when there is a difference in charge across a membrane

Question 14

what is the potential difference across a membrane usually when there are no impulses

Answer 14

-70mv

(lower than outside the membrane)

Question 15

what contributes towards establishing and maintaining resting potential

Answer 15

-active transport of sodium and potassium ions
-a difference in membrane permeability to sodium and potassium ions

Question 16

active transport of sodium and potassium ions

Question 17

difference in membrane permeability to sodium and potassium ions