Nerves Flashcards
(32 cards)
Why is a nervous system necessary?
It’s important that organisms respond to changes in the environment, the nervous system coordinates these responses. They respond to stimuli
What constitutes a neurone?
Cell Body, Dendrons and Axon
Describe a cell body
Nucleus surrounded by a cytoplasm, plenty of RER to make neurotransmitters.
What are dendrons?
Short extensions that transmit electrical impules towards the cell body.
What are axons?
Transmit electrical impulses away from the cell body
Describe the structure of an axon
Narrow region of cytoplasm surrounded by a plasma membrane
Role of a sensory neurone
Transmit electrical impulses from sensory receptor cell to a relay neurone, motor neurone or brain
Description of sensory neurone
One axon, one dendron
Role of relay neurone
Transmit impulses between neurones
Description of relay neurone
many short axons and dendrites
Role of motor neurone
Transmit electrical impulses to an effector from a relay or sensory neurone
Description of motor neurone
one long axon and many dendrites
What is myelination
many layers of plasma membrane wrapped around axon- for each wrap a double layer of phospholipid bilayer is laid down
Which cells produces the myelin sheath
Schwann cells
Why is myelination important
faster transmission of electrical impulses
How does the myelin sheath speed up nervous transmission
Electrical impulse has to travel from one node of ranvier to the next- saltatory conduction
Where are sensory receptors located
The sense organs- ears, eyes, nose…
What is the role of sensory receptors
To detect changes in the environment (stimulus)
How do sensory receptors perform their role
they convert the stimulus into an action potential which is then transmitted to the CNS
What does the CNS do with this information
Sends an impulse to an effector, via a motor neurone, to coordinate the appropriate response
Characteristics of sensory receptors
They are specific to the stimulus. They act as transducers.
What is a transducer
Converts stimulus to an electrical impulse- converts energy from X- electrical
Mechanoreceptors
Stimulus: Pressure and Movement
Example: Pacinian Corpuscle
Location: Skin and joints
Chemoreceptors
Stimulus: Chemicals
Example: Olfactory receptor
Location; Nose
