9.2 1 Nervous systems and neurones

Question 1

nervous system purpose

Answer 1

communication

Question 2

neurones definition

Answer 2

specialised cells for the rapid transmission of impulses throughout an organism

Question 3

what is the nervous system made up of

Answer 3

interconnected neurones

Question 4

receptor cells definition

Answer 4

specialised neurones that respond to changes in the environment
give information from internal and external environment to neurones

Question 5

effector cells definitions

Answer 5

specialised cells that bring about a response when stimulated by a neurone
muscles or glands

Question 6

simple nervous systems

Answer 6

receptor cells –neurones—nerve endings associated with effectors

Question 7

sense organs definition

Answer 7

groups of receptors working together to detect changes in the environment

Question 8

what do sensory neurones do

Answer 8

neurones that only carry information from internal or external environment into the central processing areas of the nervous system

Question 9

central nervous system (CNS) definition

Answer 9

a specialised concentration of nerve cells where incoming information is processed and from where impulses are sent out through motor neurones which carry impulses to the effector organs

Question 10

what is the CNS in vertebrates

Answer 10

the brain and the spinal cord

Question 11

neurone structure

Answer 11

each has a long nerve fibre that carries the nerve impulse

nerves are bundles of nerve fibres

Question 12

axons

Answer 12

long nerve fibre of a motor neurone which carries the nerve impulse
away from cell body

Question 13

dendron

Answer 13

long nerve fibre of a sensory neurone which carries the nerve impulse
towards the cell body

Question 14

peripheral nervous system

Answer 14

parts of the nervous system that spread through the body and are not involved in the central nervous system

Question 15

motor neurone

Answer 15

long axon 
short dendrites 
connected to an effector 
synaptic bulbs pass on impulse to effector
(see image)

Question 16

sensory neurone

Answer 16

long dendron
cell body not in middle
connected to a receptor
(See image)

Question 17

relay neurone

Answer 17

equal axon and dendron
typical neurone
(see image)

Question 18

nerve impulses definitions

Answer 18

electrical signals transmitted through neurones of the nervous system

Question 19

what is in the cell body and why

Answer 19

cell nucleus , mitochondria , other organelles and the rough endoplasmic reticulum and ribosomes which are needed for the synthesis of neurotransmitter molecules

Question 20

dendrites

Answer 20

slender finger-like processes that extend from the cell body of neurones and connect to neighbouring neurones

Question 21

relay neurones

Answer 21

found in CNS

connect motor and sensory neurones

Question 22

most vertebrate neurones

Answer 22

are associated with another specialised type of cell the Schwann cell
Schwann cell membrane wraps itself repeatedly around the nerve fibre forming the fatty insulating layer called myelin sheath

Question 23

gaps between schwann cells

Answer 23

nodes of Ranvier -enable saltatory conduction

Question 24

why is the myelin sheath important

Answer 24

protects the nerves from damage and speeds up transmission of the nerve impulse

Question 25

myelin sheath consists of

Answer 25

many layers of schwann cell membrane -cytoplasm and nucleus of schwann cell squeezed to outside

Question 26

what does the speed of impulses depend on

Answer 26

the diameter of the nerve fibre - the thicker the fibre the more rapidly the impulses travel along it
presence/absence of myelin sheath -myelinated nerves can carry impulses much faster than unmyelinated ones

Question 27

invertebrates do not

Answer 27

have myelin sheaths on their nerve fibres and have a small nerve diameter so many nerve impulses travel quite slowly
some have developed giant axons to allow to respond quickly to avoid danger

Question 28

research on axon

Answer 28

uses giant axons because easier to work on and fewer ethical issues when working with invertebrates

Question 29

vertebrates contain

Answer 29

both unmyelinated and myelinated nerves
e.g. voluntary motor neurones all are myelinated however autonomic neurones control involuntary muscles can be unmyelinated

Question 30

why is myelin sheath effective

Answer 30

speeds up transmission without the need for giant axons which take up a lot space