15.1 Neurones and nervous coordination

Question 1

What are the two main forms of coordination

Answer 1

• Nervous system
• Hormonal system

Question 2

What is the nervous system

Answer 2

• Use nerve cells to pass electrical impulses along their length
• They stimulate their target cells by secreting chemicals known as neurotransmitters directly onto them
• Rapid communication between specific parts of an organism, and the responses are short lived and are restricted to a localised region in body

Question 3

What is the hormonal system

Answer 3

• Produces chemicals (hormones) that are transmitted in blood plasma to target cells
• Target cells have specific receptors on their cell surface membrane and the change in concentration of hormones stimulates them.
• So slower, less specific form of communication within an organism. Responses are longer lasting

Question 4

Name 5 differences between nervous and hormonal systems

Answer 4

• Hormonal transmission is in the blood whilst transmission is by neurones in nervous system
• Hormonal transmission and response is slow whilst nervous is rapid
• Hormones travel to all parts of body but only target cells respond whilst nerve impulses only travel to specific parts of the body
• Response is long lasting in hormonal system whilst it is short lived in nervous system
• Hormonal system effect might be permanent and irreversible whilst in nervous system it is temporary and reversible

Question 5

What components is a motor neurone made of

Answer 5

• Cell body
• Dendrons
• Axon
• Schwann cells
• Myelin sheath
• Nodes of Ranvier

Question 6

Describe cell body of a motor neurone

Answer 6

This contains all the usual cell organelles including nucleus and large amounts of rough endoplasmic reticulum.

This is associated with production of proteins and neurotransmitters

Question 7

Describe Dendrons of a motor neurone

Answer 7

Extensions of cell body which each divide into smaller branched fibres called dendrites that carry nerve impulses towards the cell body

Question 8

Describe an axon in motor neurone

Answer 8

Single long fibre that carries nerve impulses away from the cell body

Question 9

Describe Schwann cells in neurone

Answer 9

• Surround the axon, protecting it and providing electrical insulation
• They also carry out phagocytosis and play a part in nerve regeneration
• Schwann cells wrap around the axon many times so layers of their membrane build up around it

Question 10

What does a myelin sheath do in neurone

Answer 10

• Forms a covering to the axon and is made up of the membranes of the Schwann cells
• These membranes are rich in the lipid myelin, so neurones surrounded by this are myelinated neurones

Question 11

What do nodes of ranvier do in neurones

Answer 11

Constrictions between adjacent schwann cells where there is no myelin sheath

Question 12

What are the 3 types of neurone

Answer 12

Sensory neurones
Intermediate neurones
Motor neurones

Question 13

What do sensory neurones do

Answer 13

Transmit nerve impulses from receptor to an intermediate neurons.

They have one dendron which is very long and it carries impulse towards the cell body whilst axon carries it away from cell body

Question 14

What do intermediate neurones do

Answer 14

• Transmit impulses between neurones eg from sensory to motor neurones

Question 15

What do motor neurones do

Answer 15

• Transmit nerve impulses from intermediate neurone to an effector eg gland or muscle.
  Long axon and short dendrites