Nervous system Flashcards
what does the central nervous system-CNS consist of
the brain and the spinal cord
what does the peripheral nervous system-PNS consist of
the nerves leading to and from the CNS
e.g. spinal nerves
what does a typical nerve contain
sensory and motor neurons and ganglia
define neurons
neurons are nerve cells which are specialised to carry impulses
what is the function of sensory neurons
sensory neurons transmit impulses from sense organs toward the central nervous system
what is the function of interneurons
interneurons transmit impulses within the CNS from sensory and motor neurons
what is the function of motor neurons
motor neurons transmit impulses away from the CNS to muscle fibres and glands =effectors
define receptors
receptors are sensory cells that detects stimulus or a change in environment and generate impulses
define effectors
effectors are muscles or glands which are capable of producing a response
description and function of cell body
- it contains nucleus surrounded by cytoplasm and organelles such as mitochondria
- function is it produces neurotransmitter chemicals such as dopamine
description and function of axon
- elongated nerve fibre
- its function is to carry impulses away from the cell body
description and function of dendrites
- branched nerve fibres generally
- its function is to receive and transmit impulses toward the cell body
description and function of myelinsheath
- fatty membrane around the nerves
- both insulates and speeds up impulse transmission
function of schwan cell
-produces the myelin sheath
function of axon terminals
- neurotransmitter swellings release chemicals called neurotransmitters e.g. dopamine
- dopamine is stored in vesicles within the neurotransmitter swelling before being released
what is an impulse
- an impulse is an electrical message
- flow of positive ions carried by a neuron
what does the transmission of a nerve impulse require
- ions
- energy in the form of ATP
what are the characteristics of nerve impulses
- THE THRESHOLD OF SIMULATION
- the threshold is the minimum level of stimulus needed for impulse transmission. below the threshold no impulse is generated.
e. g. lukewarm water is below the threshold so no impulse is generated - THE ALL OR NOTHING EFFECT
- the impulse will travel the entire length or not at all: once started it cannot be stopped - THE REFRACTORY PERIOD
- the timespan after impulse transmission when stimulus fails to cause a response - SPEED OF IMPULSE
- impulses are faster when myelin sheath is present and when the diameter of the nerve fibre is greater
define synapse
the synapse is a region where two neurons come into close contact allowing impulses to pass from one neuron to another
what is a reflex action
is an automatic involuntary response to a stimulus