Nervous System Flashcards
role of nervous system
the nervous system enables different parts of the body to communicate with each other. in addition it allows the body to regulate and control the various parts so that it is able to function collectively
define a voluntary action
When the action is under the control of the will
Define an involuntary action
When the action is an immediate unconscious response to a specific stimuli eg a knee jerk reflex
the nervous system consists of
the central nervous system which is ,add up of the brain and spinal cord and the peripheral nervous system which is made up of nerves that connect the various parts of the body to the cns
The spinal nerves are connected to ?
spinal cord
Cranial nerves are connected to
Brain
The nervous system is designed to
- Detect change in the conditions of environment
- these changes are termed as stimuli the detection occurs through modified neurons called the receptors
-connects each stimulus into electrical signal called nerve impulses that can be transmitted within a fraction of a second
—transmit the impulses to the cns for coordinating a response and transmit impulses from the cns to other specialised cells that produce a response. These cells are called the effectors
Nervous tissue consists of nerve cells known as
Neurons
State the role of neurons
They are responsible for transmitting nerve impulses in the nervous system
State the function of the sensory neurons and state where the cell body is located within the nervous system
Transmits impulses from receptors in the body to the cns and the cell body is often located in specialised areas known as ganglia within the nervous system
state the function and structure of the relay neurons and where it is located
- it transmits nerve impulses from the sensory neuron to the motor neuron
- short dendrons and the axon is unmyelinated
- found within the cns
state function and location of the motor neurons
It conducts impulses from the cns to the effectors such as the muscles and glands
the cell body of a motor neuron is always located within the grey matter of the cns, while its axon is present in one of the nerves of the pns
In the motor neuron what does the cell body contain
The nucleus cytoplasm, cell membrane and mitochondria and other organelles
state exactly what a dendron in a motor neuron
a nerve fibre that transmits nerve impulses towards the cell body
end branches are called dendrites and dendrites receive impulses from other neurons
State what an axon is and what it does
a very elongated nerve fibre that transmits impulses away from the cell body to other neurons or cells of an effector
State what the myelin sheath is and what it’s function
Axon of some neurons is covered by myelin such neurons are termed as myelinated neurons. It insulated the axon, just as a rubber sheath insulates an electrical wire. Schwann cells deposit the myelin by growing round and round the axon
What is the node of Ranvier and what does it do
It is the region where the myelin sheath is absent. It allows nerve impulses to jump from node to node, thus speeding up the rate of transmission of nerve impulses (saltatory conduction)
Define motor end plate
It is formed where the end branch of an axon comes into contact with the muscle fibre. Impulses are transmitted across the motor end plate by chemicals which stimulate the muscle
What is the relationship between the 3 types of neurons
The sensory neurons which are the receptor neurons detect sensory information which then transmits nerve impulses from the sensory organs or receptors to the cns. The relay neurons transmits the nerve impulses from the sensory neuron to the motor neuron which the motor neuron then transmits the nerve impulses to the effectors from the cns
Define a synapse
A junction between two neurons or between a neuron and an effector such as a muscle or gland
Structure of a synapse
Pre synaptic and post synaptic cells are separated by a fluid filled gap, so electrical impulses cannot pass across
This gap is called the synaptic cleft and is only about 20nm wide
Chemicals called neurotransmitters are used to send signals cross synapse
- each synapse uses a specific neurotransmitter. Acetylcholine and dopamine are examples of neurotransmitters
How are nerve impulses transmitted between neurons
They are transmitted between neurons across a synapse
When a nerve impulse arrives at the synapse, neurotransmitters are released into the synaptic cleft
The neurotransmitters diffuse across the synaptic cleft and binds to specific receptors on the post synaptic membrane
This causes the ion channels in the post synaptic membrane to open
A nerve impulse is subsequently generated in the post synaptic neuron
