4. neurons Flashcards
what is the key term for neuron
basic buildings blocks of the nervous system - nerve cells that process and transfer messages through electrical and chemical signals.
what is the key term for synapses
the site of transmission of electric nerve impulses between two nerve cells (neurons or between a neuron and a gland or muscle cell (effector).
what is the key term for myelin sheath
an insulating layer that forms around nerves and allows electrical impulses to transmit quickly and efficiently along the nerve cells.
what is the key term for soma
spherical part of the body that contains the nucleus - cell body connects to the dendrites.
what is the key term for axon
long projection of a nerve cell or neuron (vertebrates) that typically conduct action potentials.
what is the key term for nucleus
command center of the cells - contains chromosomes and genetic information needed for reproduction.
what is the key term for dendrites
projections of neurons that receive signals from other neurons.
what is the key term for nodes of ranvier
gaps in the myelin sheath on the axon that serves to facilitate the rapid conduction of nerve impulses.
what is the key term for terminal bulbs
small knobs at the end of an axon that release neurotransmitters.
name three key facts about neurons
100 billion of these in our bodies - 80% of them are in our brain.
they allow the brain to send electrical impulses and chemical messages around the body.
how do neurons communicate
they receive messages from sensory organs or other neurons.
messages pass between two neurons by neurotransmitters diffusing across the synaptic cleft (gap between neurons).
messages run through neurons by becoming electrical impulses triggered by neurotransmitters reaching the postsynaptic receptor site.
what are the characteristics of the relay neuron
short dendrites and short axons.
what are the functions of the relay neuron
connect the sensory and motor neuron and allow them to communicate.
found in the brain and spinal cord.
allows fast reflex actions to take place by bypassing the brain.
what are the characteristics of the sensory neuron
long dendrites and short axons.
what are the functions of the sensory neuron
found in receptors and carry nerve impulses to the brain and spinal cord. when they reach the brain they are translated into sensations.
however, not all sensory neurons reach the brain as some stop at the spinal cord to allow quick reflex actions.
what are the characteristics of the motor neuron
short dendrites and long axons.
what are the functions of the motor neuron
found in and connect the CNS to effectors (muscles and glands) to control muscle movements.
when motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response - leads to movement.
how can the transmission of messages through the neuron be electric
neuron in resting state = negatively charged.
neuron activated by stimulus = inside of cell becomes positively charged for a split second.
an action potential will pass through the neuron when it is positively charged - allows an electrical impulse to travel down the axon and towards the end of the neuron.
explain the knee jerk response
when a stimulus (hammer) hits the knee - detected by the sense organs found in the PNS which conveys a message along the sensory neuron.
messages reach the CNS where it connects with a relay neuron which transfers messages to a motor neuron - causes muscles to contract and therefore the knee jerks.
