Neurones and receptors Flashcards
(21 cards)
What are neurones?
Specialised nerve cells vital for transmitting electrical impulses quickly throughout the body enabling organisms to react to environmental changes
What are the key structural components of a mammalian neurone?
- cell body
- dendron
- axon
What is the cell body?
Contains nucleus and cytoplasmic organelles, such as mitochondria and the endoplasmic reticulum crucial in neurotransmitter production
What is a dendron?
Short branches extending from cell body further dividing into highly branched dendrites to receive nerve impulses from many other neurones and transmit them towards the cell body
What is an axon?
Singular long nerve fibre responsible for carrying impulses away from the cell body to other neurones or effectors
What are schwann cells?
Make up the myelin sheath that surrounds the axon
What are the functions of schwann cells?
- membranes form myelin sheath
- remove debris via phagocytosis
- aid regeneration
What is the function of the myelin sheath?
Surrounds parts of the axon acting as an insulator preventing ion passage in or out of the axon at the regions it covers
What is saltatory conduction?
Electrical impulse ‘jumps’ between gaps in the myelin sheath called the nodes of ranvier increasing transmission speed
What is the structure and function of a sensory neurone?
Structure = one axon and one dendron with the dendron leading into several smaller dendrites and a central cell body
Function = carries impulses from sensory receptors to central nervous system
What is the structure and function of a relay neurone?
Structure = numerous short axons and dendrons
Function = carries impulses within the central nervous system between other neurones
What is the structure and function of a motor neurone?
Structure = one long axon and multiple dendrites
Function = carries impulses from the central nervous system to effectors
What is the typical pathway of an impulse?
Receptor → sensory neurone → relay neurone → motor neurone → effector
What are sensory receptors?
Specialised cells that detect stimuli from the environment
What is a transducer?
Converts one form of energy into another
How does a sensory receptor act as a transducer?
Converts the stimulus energy into a nerve impulse that is passed to the central nervous system
What is resting potential?
At rest receptor cell-surface membrane has a voltage across it due to differences in ion concentration in and out the cell
What are the stages of receptor cells functioning?
1) when stimulus is detected the cell-surface membrane becomes more permeable allowing more ions to flow in and out
2) alters membrane’s voltage creating generator potential (receptor potential)
3) larger stimulus results in a bigger change in voltage, producing a larger generator potential
4) If generator potential reaches a threshold level it triggers an action potential
What is the function of the pacinian corpuscles?
Mechanoreceptors in the skin that detect pressure and vibrations
What is the structure of the pacinian corpuscles?
Sensory neurone ending wrapped in layers of connective tissue called lamellae with viscous gel between each layer of tissue
What happens when the pacinian corpuscle is stimulated?
1) lamellae deform pressing on sensory neurone ending
2) stretches neurone’s membrane causing it to change shape
3) opens stretch-mediated sodium ion (Na+) channels in the membrane increasing its permeability to Na+
4) Na+ diffuses into neurone depolarising it resulting in a generator potential
5) If signal reaches the threshold an action potential is triggered
