5.1.3 - Neuronal Control✅ Flashcards
Outline cell signalling?
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
Outline the division of the nervous system?
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
What are neurones - give structure?
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
Outline the pathway of a nerve impulse - for a voluntary action?
Stimulus - receptor - sensory neurone - CNS - motor neurone - effector
Give 3 types of neurons?
- 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
Outline the features of sensory neurones?
- cell body outside CNS
- short axon
- long dendron
- carry action potential to CNS
- myelinated
Outline the features of motor neurones?
- cell body in CNS
- long axon
- short dendrites
- carry action potential away from CNS
- myelinated
Outline the features of relay neurones?
- 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
Explain how neurones are adapted - give 2 points?
- 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
Outline the role and function of the myelination of neurones?
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
What is the purpose of myelination of neurones?
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
Explain the structure of myelin sheath?
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)
Explain the role of unmyelinated neurones?
- 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
Explain why action potential travels faster in myelinated neurons?
- 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.
Finnish resting and action potentials
