nervous system Flashcards
What is the role of the nervous system?
- detects stimuli internally in the body or externally in the environment
- processes this information in the CNS
- initiates a suitable response
what is a stimulus?
a change in the internal or external environment
how is stimuli detected?
using sensory receptors
how is the response to a stimuli brought about?
brought by an effector through a nerve impulse to a muscle or a gland or through hormones via the blood
what are nerve cells?
bundles of neurones
where is white matter located?
the outside of the spinal chord
what does white matter contain?
myelinated neurons
what does grey matter contain?
many nuclei, cell bodies and non-myelinated neurons
where is grey matter located?
closer to the centre of the spinal chord
what are the two parts that make up the nervous system?
the central nervous system (CNS) and peripheral nervous system (PNS)
What is the CNS made up of?
the brain and spinal cord
what type of neurones make up the PNS?
- sensory neurones carry impulses to the CNS from receptors (afferent)
- motor neurones carry impulses from the CNS to effectors (efferent)
what connects the sensory and motor neurones together?
relay neurones
where is the cell body in the sensory neurone?
on the side
what is special about the relay neurone?
can look star shaped as its fibres are so short
what is a special feature of the motor neurone?
very long axon
what direction is the flow of the impulse?
dendron to cell body to axon
What is a simple reflex?
an inborn response to a stimulus and is rapid, automatic and beneficial
Why are the effectors small in simple organisms like the Hydra?
the sense receptors respond to a limited number of stimuli
what do nerve net systems look like in simple organisms like the Hydra?
consists of simple nerve cells with short extensions joined to each other and branching in a number of different directions
What is the purpose of the dendron/many dendrites?
carries the impulse towards the cell body
What is contained within the cell body of the neurone?
nucleus, many ribosomes on RER inside Nissl granules, Golgi body, mitochondria
Why are proteins and membranes needed for neurones?
for renewal of axon or terminals made in the cell body, assembled into vesicles, transported along microtubules down the axon to be used
what is the synaptic terminal?
axons often have thousands of terminal branches, allowing them to connect with many other neurones or effectors
