Nervous System Introduction Flashcards
Describe the role of the NS in homeostasis
When signals are sent through the NS which trigger responses to bring the system back to the normal range of functioning.
What are the two main subdivisions of the NS
Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
List the structures involved in the CNS and PNS
CNS - Brain and Spinal Cord
PNS - Cranial and Spinal Nerves
Describe a Neuron
- Neurons conduct nerve impulses
- Electrically excitable
- Connect all regions of the body to the brain and spinal cord through the generation and conduction of nerve impulses
Describe Neuroglia cells
They support, nourish, insulate and protect neurons. They are smaller bur significantly more numerous than neurons
Describe a Tract
A bundle of axons located in the CNS having the same origin, termination and function
Identify the structural components of a neuron
Dendrites, the trigger zone, the axon, myelin sheath a synaptic end bulb
What is Grey Matter and where is it found?
Neuronal cell bodies, dendrites, unmyelinated axons, axon terminals and neuroglia. It is found in the brain and spinal cord
What is White Matter and where is it found?
White matter is made of axons connecting different parts of grey matter to each other. It is found in the brain and transverse plane in the spinal cord
What are aged related changes in the NS
- Your brain and spinal cord lose nerve cells and weight
- Nerve cells can begin the passing of messages more slowly
- Slowing of memory, thought and thinking
- Reduced or lost reflexes or sensations
- Loss of synaptic connections
How is a nerve impulse generated?
When signals move across the synapse. The place where the icon of one neuron meets the dendrite of another neuron, using chemicals called neurotransmitters.
What are the two main ions involved in the generation of a nerve impulse?
Sodium Na and Potassium K+
What is continuous conduction?
A progressive gradual depolarization and repolarization
What is saltatory conduction
Impulse ‘boosted’ between nodes therefore increasing the speed of conduction.
What are the components and function of the synapse
This is the place where signals are transmitted from one neuron (presynaptic) to another neuron (postsynaptic). This can be chemical or electrical
What makes up a chemical synapse?
A synaptic knob, a synaptic cleft and the plasma membrane of a postsynaptic neuron
What is a chemical synapse?
A gap between two neurons where info passes chemically in the form of neurotransmitter molecules
What is an electrical synapse?
It is a gap that has channel proteins connecting the two neurons so the electrical signal can travel straight over the synapse
What is a neurotransmitter?
It is a chemical substance used by neurons to communicate with other neurons, muscles and glands
Excitatory Postsynaptic potential
generates a nerve impulse
Inhibitory Postsynaptic potential
less chance of nerve impulse being generated
What are the 4 types of Neuroglia in the CNS
Astrocytes, microglia, oligodendrocytes, ependymal cells
What are Astrocytes?
They physically support/barce anchor neurons. They help create the BBB. They maintain a chemical environment for generation of nerve impulse
What are the Microglia?
Function as phagocytes within the CNS
What are ependymal cells?
help to produce cerebrospinal fluid
What are oligodendrocytes?
They form and maintain myelin around axons in the CNs
A resting nerve fiber is polarized because?
The concentration of Na+ is higher on the outside and K+ is higher on the inside
At a synapse, the neuron sending the signal is called the _______ neuron.
presynaptic
What happens during depolarization of a neuron
Na+ moves into the cell
what happens in myelinated nerves
An action potential occurs at each node of Ranvier
Masses of myelinated nerve fibers appear what colour?
White
Saltatory conduction occurs only where?
occurs only on myelinated fibers
Sensory impulses are carried to the central nervous system by?
afferent neurons
Which ions are rapidly moving into the cell during the depolarization period of an action potential?
Sodium
The dendrites of a neuron are what?
are the main receiving region of a neuron
