5.3 Neuronal Communication Flashcards
Why are neurones very long?
So that they can transmit an action potential over a large distance
Why does a neurone plasma membrane have many gated ion channels?
To control the entry or exit of Na+ , K+ and Ca2+
Sodium/Potassium pumps use _____ to actively transport Na+ ____ and K+ ____ the cell.
ATP, Na+ out, K+ in
What is the function of a dendrite?
To carry nerve impulses towards the cell body
What is the function of the axon?
To carry nerve impulses away from the cell body
What is the purpose of Shwann cells?
To insulate electrical activity from affecting nearby cells
Where do motor neurones have their cell body?
In the CNS
What is a myelinated neurone?
A neurone insulated by an individual mylein sheath.
Why do motor neurones have an extra long axon?
To carry the action potential from the CNS to an effector.
Where is the cell body of a sensory neurone?
Just outside the CNS
Sensory neurones have a long ______ that carries an action potential from a sensory _______ to the cell body (just outside CNS) then a short _____ carrying the impulse into the CNS.
Long dendrite, sensory receptor, short axon
What are gaps in the myelin sheath called?
Nodes of Ranvier
What is an action potential?
A brief reversal of the potential difference across the membrane at a peak of +40mV
What is resting potential?
When the nerve cell is at rest with a potential difference across the membrane of -60mV
What is the all or nothing principle?
All nerve impulses are identical, independent of the strength of a stimulus.
What value (mV) must be reached before an action potential can be transmitted?
+40mV
What is a Pacinian corpuscle?
A pressure sensory receptor that detects pressure changes on the skin
Sensory receptors are energy _________ that convert energy from one form to the other.
Transducers
What is a corpuscle?
An oval shaped structure that consists of rings of connective tissue wrapped around a nerve cell ending
What is generator potential (receptor potential)?
The change in potential across a receptor membrane
How does a Pacinian corpuscle generate a nerve impulse?
When pressure is applied to the corpuscle it becomes deformed and pushes against the nerve ending, opening Na+ channels
When a neurone is at rest, the inside of the cell is ___________ charged.
Negatively
Why do larger diameter axons send faster impulses?
Have low SA:V so less ions leak out the axon making action potentials easier
What is a local current?
The movement of Na+ along the axon, away from where they came in
What is summation?
When the effect of neurotransmitters can be combined to make the membrane depolarisation reach a threshold allowing an action potential to be generated
What is spacial summation?
When neurones converge each neurone releases a small amount of neurotransmitter and together will be enough to generate an action potential
What is temporal summation?
When nerve impulses arrive in quick succession making action potential more likely because more neurotransmitter is in the synaptic cleft
What is synaptic divergence?
When one neurone connects to many, allowing information to be dispersed to different areas of the body
What is synaptic convergence?
When many neurones connect to one allowing information to be amplified
Why can nerve impulses only be transmitted in one direction?
Because receptors for neurotransmitters are only on the postsynaptic membrane
