Neuronal Communication Flashcards
What are sensory receptors?
Specialised cells that can detect changes to the environment.
What are transducers?
A cell that converts one energy into another. - eg- electrical to chemical
What is a nerve impulse?
How the sensory receptors respond to a stimulus by creating a signal in the form of electrical energy.
What detects the change in light intensity?
Rods and cones in the retina- light to electrical
What do temperature detectors in the skin and hypothalamus detects.
Temperature change- heat to electrical
What is a pacinan corpuscle?
A pressure sensor to detect change in pressure on the skin
Describe the Pacinian corpuscle?
Oval shaped
Concentric rings of connective tissue wrapped around the end of a nerve cell
How does the Pacinian Corpuscle work?
When pressure is applied the rings of connective tissue are deformed which push against the nerve endings
What causes the Pacinian Corpuscle to stop responding?
When pressure is constant
What can’t pass through the lipid bilayer?
Charged particles
Describe resting potential?
The sodium ion channels are kept closed
Some potassium gates are kept open
Potassium ions diffuse out the cell
The cell cytoplasm contains negatively charged ions
The inside is more negative that the outside- therefore is polarised
How is a nerve impulse created?
By altering the permeability of the nerve cell to sodium ions- by opening the sodium ion channels
What happens when the sodium ion channels open?
Sodium ions can move across the membrane down their concentration gradient.
What is the potential difference and how is it changed?
It’s the charge which is changed by the movement of ions across the membrane.
What change in potential difference is caused when creating a nerve impulse?
The inside of the cell becomes less negative compared to the outside- depolarisation
What is a generator potential?
The change in potential across a receptor menbrane
What is the relationship between the stimulus and the Sodium ion gates?
The larger the stimulus the more gated channels will open.
When will an action potential be initiated?
When enough Sodium ion gates are open and enough sodium ions enter the cell to change the potential difference across the membrane significantly
What is the initiation of an impulse?
An action potential
What is the ratio between sodium ions and potassium ions?
3 sodium ions are pumped out for every 2 potassium ions pumped in
What is the permeability of the cell membrane to NA/K ions?
More permeable to K ions so are able to leak out
Less permeable to NA ions- not able to leak in
What are motor neurones?
To carry an action potential from the CNS to an effector
Function of relay neurones?
To connect sensory and motor neurones
Give 2 features of neurones?
Very long to transmit the action potential over a long distance
Cell surface has many gated ion channels
What organelles do neurones contain?
Nucleus
Many mitochondria
Ribosomes
Additional structures of neurones?
Dendrites
Axon
Myelin sheath
Function of dendrites?
Connect to other neurones
Carry impulses towards the cell body
Function of axon?
Carries impulses away from the cell body
What cells are associated with the neurone?
Schwann cells
Describe motor neurone?
Have their cell body in the CNS
long axon
Describe sensory neurones?
Long dendron
Cell body positioned outside the CNS
Short axon
Describe the relay neurone?
Many short dendrites
Short axon
Describe the Myelin sheath?
A fatty layer made up of Schwaan cells wrapped tightly around the neurone
What are the gaps in the Myelin sheath called?
Nodes of ranvier
How do the ions move across the neurone membrane?
Jumps from one node to the next as the myelin sheath prevents ions movement
How does the action potential move in non myelinated neurones?
In a wave movement
Advantages of myelination?
Quicker transmission
Carry action potentials over long distance
Can enable a rapid response
When are non-myelinated neurones used?
Coordinating body functions such as breathing and the action of the digestive system
What is the cholinergic synapse?
Uses acetylcholine as the neurotransmitter
What is a synapse?
A junction between 2 or more neurones
What is the gap between a synapse called?
The synaptic cleft
What is the distance of the gap between the synapse?
20nm
What is the pre-synaptic bulb?
The swelling at the end of the pre-synaptic neurone
What does the pre-synaptic bulb contain?
Many mitochondria
A large amount of SER
Large number of vesicles
Calcium gated ion channels on the cell surface membrane
What does the post synaptic membrane contain?
Sodium gated ion channels
What are the sodium channels made of?
5 polypeptides
2 of which have complementary receptors to acetylcholine
By what process does acetylcholine leave and enter the neurones?
Exocytosis
Facilitated diffusion
Transmission across a synapse- 1/4
Upon arrival of action potential calcium ion channels open. The calcium ions cause the vesicles to move and fuse with the membrane
Transmission across a synapse- 2/4
The acetylcholine diffuses across cleft and binds to receptor sites
Transmission across the synapse- 3/4
This causes the NA ion channels to open. NA ions enter the neurone.
Transmission across the synapse- 4/4
This creates a generator potential. Once the potential reaches threshold potential a new action potential is created.
What is the term to describe the jumping from one node to the next?
Saltatory conduction
