13 - Neural Communication Flashcards
What is a stimulus?
A change in the internal or external environment of an organism
What is a sensory receptor?
Specialised nerve cell that is designed to respond to a specific sensory stimulus
What are the two main features of any sensory receptor?
- Acts as a transducer 2. Is specific to a single stimulus
What is a pacinian corpuscle?
They are nerve endings in the skin, responsible for sensitivity to deep pressure touch
What type of energy do sensory receptors convert stimuli into?
Electrical energy
What are the 3 main parts of a neurone?
Cell body, dendrons, axons
Why do Pacinian Corpuscles stop responding when pressure is constant?
They are only sensitive to changes in pressure
What is the structure of a Pacinian Corpuscle?
Oval shaped, with many concentric rings of connective tissue which are wrapped around a nerve ending
How do Pacinian Corpuscles work?
Pressure on the skin deforms the rings of connective tissue, which then press against the nerve ending
What 2 organelles are very prevalent within a neurone’s cell body and why?
Mitochondria and endoplasmic reticulum, in order to produce lots of neurotransmitters
What are dendrons responsible for?
Transmitting electrical impulses towards the cell body
What are axons responsible for?
Transmitting electrical impulses away from the cell body
How many axons and dendrons does a sensory neurone have?
One of each
How many axons and dendrons does a relay neurone have?
Many short ones of each
How many axons and dendrons does a motor neurone have?
One long axon and many short dendrons
What is a myelinated neurone?
One covered in a myelin sheath (many layers of cell membrane)
What is the function of a Schwann Cell?
Produce myelin sheaths by growing around the neurone many times
What is the resting potential of a neuron?
-70mV
How many times quicker can a myelinated neurone conduct a nerve impulse than an unmyelinated neurone?
Up to 100 times quicker
What is the purpose of a myelin sheath?
Electrically insulates the axon of a neuron and increases speed of nerve impulse conduction.
What is a node of Ranvier?
A small gap in the myelin sheath of a nerve, between adjacent Schwann cells.
Why is the transmission of electrical impulses so much faster in myelinated neurones?
The electrical impulse ‘jumps’ between the nodes of Ranvier, which is much quicker than being continuously transmitted along an unmyelinated neurone
What neurones are myelinated in mammals?
Around 1/3 of peripheral neurones
What neurones are not myelinated in mammals?
All of them in the CNS and approximately 2/3 of the peripheral nervous system