5.1.3 - Neuronal Control✅

Question 1

Outline cell signalling?

Answer 1

Nervous and hormonal systems coordinate the activities of whole organisms

• relies on communication at a cellular level
• One cell releases a chemical which has an effect on a target cell
• cells transfer signals locally e.g. between neurones at synapses using a neurotransmitter or long distance with hormones

Question 2

Outline the division of the nervous system?

Answer 2

CNS (brain/spinal cord)
PNS (peripheral nervous system made up of neurones that connect the CNS to rest of body - made up of SMS and ANS)

SMS - somatic nervous system - controls conscious activities
ANS - autonomic nervous system - controls unconscious actives - has 2 divisions

Parasympathetic - calms body down (‘rest and digest’) releases acetylcholine

Sympathetic - gets body ready for fight or flight - releases noradrenaline

Question 3

What are neurones - give structure?

Answer 3

Specialised cells that conduct electrical impulses within the nervous system

• bundle are a nerve
• have long fibre - axon with axon terminal at end with many nerve endings (allow neurones to connect to many neurones - forming a network)
• cell body that contains nucleus

Question 4

Outline the pathway of a nerve impulse - for a voluntary action?

Answer 4

Stimulus - receptor - sensory neurone - CNS - motor neurone - effector

Question 5

Give 3 types of neurons?

Answer 5

• sensory neuron’s - transmit electrical impulses from receptors
• relay neruons (in CNS) - transmit electrical impulses within CNS - connect sensory and motor
• motor neuron’s - transmit electrical impulses from CNS to effector

Question 6

Outline the features of sensory neurones?

Answer 6

• cell body outside CNS
• short axon
• long dendron
• carry action potential to CNS
• myelinated

Question 7

Outline the features of motor neurones?

Answer 7

• cell body in CNS
• long axon
• short dendrites
• carry action potential away from CNS
• myelinated

Question 8

Outline the features of relay neurones?

Answer 8

• many short dendrites
• long axon
• carry impulses from sensory neurones to the cell body and one axon which carries nerve impulses from cell body to motor neurones

Question 9

Explain how neurones are adapted - give 2 points?

Answer 9

• endings are highly branched - thin projections (dendrites) extend from the cell body and communicate with other neurones
• axons of most neurones insulated by layer called the myelin sheath - ensures the impulses travel rapidly along the axon

Question 10

Outline the role and function of the myelination of neurones?

Answer 10

axon is insulated by a myelin sheath with
small uninsulated sections along its length (called nodes of Ranvier)

• myelin sheath formed by specialised cells known as Schwann cells which wrap
  themselves around the axon
• electrical impulses do not travel down the whole axon, but jump from one node - faster

Question 11

What is the purpose of myelination of neurones?

Answer 11

means that electrical impulses do not travel down the whole axon, but jump from
one node to the next so that less time is wasted transferring the impulse from one cell to
another

• small uninsulated sections along its length - called nodes of ranvier
• uninsulated axons (non-myelinated) the impulse move slower, travel entire length

Question 12

Explain the structure of myelin sheath?

Answer 12

Myelin is a fatty substance composed of schwann cells that insulates neuron axons so as to increase the speed at which information travels (impulses jump from one node to the next)

Question 13

Explain the role of unmyelinated neurones?

Answer 13

• Many neurones in the CNS are unmyelinated.
• Unmyelinated neurones make up the grey matter found in the brain and spinal cord
• In a non-myelinated neurone the impulse travels as a wave

Question 14

Explain why action potential travels faster in myelinated neurons?

Answer 14

• Sodium ion channels are concentrated at the nodes of ranvier (just membrane)
• In myelinated neuron, depolarization only happens at the nodes of Ranvier (where sodium ions can get through the membrane)
• The neurone’s cytoplasm conducts enough electrical charge to depolarize the next node, so the impulse ‘jumps’ from node to node.

Question 15

Finnish resting and action potentials