The Nervous System

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  • Created by: Jade
  • Created on: 06-01-21 14:44
What is the nervous system?
A specialised network of cells in the human body. It is our primary internal communication system.
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What are the two main functions of the nervous system?
To collect, process and respond to information in the environment.

To coordinate the working of different cells and organs in the body.
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What are the two sub-systems of the nervous system?
Central Nervous System (CNS)

Peripheral Nervous System (PNS)
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What does the CNS consist of?
The brain and spinal cord
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What is the main function of the CNS?
It passes messages to and from the brain, and connects nerves to the PNS.
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What does the PNS consist of?
Cranial nerves (carry impulses to and from the brain).

Spinal nerves (carry impulses to and from the spinal cord).
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What is the main function of the PNS?
It transmits messages, via neurons, to and from the CNS.
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What are the subdivisions of the PNS?
The sensory division (afferent) - nerves carry impulses to the CNS from sensory receptors.

The motor division (efferent) - nerves carry impulses from the CNS to effectors (muscles and glands).
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What are the subdivisions of the motor division of the PNS?
Autonomic Nervous System (ANS)

Somatic Nervous System (SNS)
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What is the main function of the ANS?
Governs vital functions in the body, such as breathing, heart rate, digestion, sexual arousal and stress responses.

(Involuntary)
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What are the divisions of the ANS?
Sympathetic - physiologically aroused, e.g. increases heartrate.

Parasympathetic - resting state, e.g. decreases heartrate.
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What is the main function of the SNS?
Controls muscle movement and receives information from sensory receptors.

(Voluntary)
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What does nervous tissue consist of?
Supporting cells (neuroglia)

Neurons
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Give some examples of neuroglia
Astrocytes

Microglia

Ependymal

Oligodendrocytes
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What are the main functions of astrocytes?
They form a living barrier between capillaries and neurons.
They help to protect the neurons from harmful substances, and help control the chemical environment in the brain.
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What are the main functions of microglia?
Monitor the health of nearby neurons, and dispose of debris, such as dead brain cells and bacteria.
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What are the main functions of ependymal?
The beating of their cilia helps to circulate the cerebrospinal fluid that fills those cavities and forms a protective watery cushion around the CNS.
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What are the main functions of oligodendrocytes?
They wrap their flat extensions tightly around the nerve fibers, producing fatty insulating coverings called myelin sheaths.
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What are neurons?
The basic building blocks of the nervous system.

They are nerve cells that process and transmit messages via electrical and chemical signals.
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Describe the general structure of a neuron
The cell body includes a nucleus, which contains the genetic material of the cell. Branch like structures (dentrities) protrude from the cell body; these carry nerve impulses from neighbouring neurons towards the cell body.
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Structure of neuron continued...
The axon carries impulses away from the cell body towards other neurons. The axon is covered in a fatty layer of myelin sheath, which is segmented by gaps called the nodes of ranvier which speed up transmission of impulses.
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Continued...
At the end of the axon, terminal buttons communicate with the next neuron across the synapse.
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What are the three types of neurons?
Motor neurons

Sensory neurons

Association neurons (aka, relay neurons)
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What are sensory neurons?
Neurons that carry impulses from sensory receptors to the CNS.

They have long dendrites and short axons.
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What are motor neurons?
Neurons that carry impulses from the CNS to the viscera and/or muscles and glands.

They have short dendrites and long axons.
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What are association neurons?
They connect motor and sensory neurons in neural pathways.

They have short dendrites and short axons.
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What are the electrical conditions of a resting neuron’s membrane?
The plasma membrane of a resting neuron is polarized - there are fewer positive ions on the inner face of the neuron’s plasma membrane than there are on its outer face.
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What are the stages of a nerve impulse?
1) Resting membrane is polarised
2) Stimulus initiates local depolarization
3) Depolarization and generation of an action potential
4) Propagation of the action potential
5) Repolarization
6) Initial ionic conditions restored
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How are signals transmitted?
Signals within neurons are transmitted electrically.

Signals between neurons are transmitted chemically via synaptic transmission.
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Define "synaptic transmission"
The process by which neighbouring neurons communicate with one another by sending chemical messages across the synapse.
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What is the composition of the synapse?
The synaptic cleft

The presynaptic terminal

The postsynaptic receptor site
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What occurs during synaptic transmission?
When the electrical impulse reaches the presynaptic terminal, it triggers the release of neurotransmitters from synaptic vesicles.
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What are neurotransmitters?
Brain chemicals released from synaptic vesicles that relay signals across the synapse.

They can be broadly divided into those that perform a excitatory function, and those that perform an inhibitory function.
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Define "excitation"
When a neurotransmitter, such as adrenaline, increases the positive charge of the postsynaptic neuron.

This increases the likelihood that the neuron will fire and pass on the electrical impulse.
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Define "inhibition"
When a neurotransmitter, such as serotonin, increases the negative charge of the postsynaptic neuron.

This decreases the likelihood that the neuron will fire and pass on the electrical impulse.
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Describe the basic anatomy of the brain?
The brain is divided into the left and right hemispheres. The left hemisphere controls the right side of the body, and the right hemisphere controls the left side of the body.

The outer layer of both hemispheres is the cerebral cortex.
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What are the subdivisions of the cortex?
The frontal lobe

The parietal lobe

The occipital lobe

The temporal lobe
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What is located at the back of the frontal lobe in both hemispheres?
The motor area - controls voluntary movement in the opposite side of the body.
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What is located at the front of the parietal lobes?
The somatosensory area - where sensory information from the skin is represented.
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What is located in the occipital lobe at the back of the brain?
The visual cortex.
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What can be found in the temporal lobes?
The auditory area - analyses speech-based information
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Where can the language areas of the brain be found?
Frontal lobe in the left hemisphere - Broca's area (responsible for speech production).

Temporal lobe in the left hemisphere - Wernicke's area (responsible for language comprehension).
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Other cards in this set

Card 2

Front

What are the two main functions of the nervous system?

Back

To collect, process and respond to information in the environment.

To coordinate the working of different cells and organs in the body.

Card 3

Front

What are the two sub-systems of the nervous system?

Back

Preview of the front of card 3

Card 4

Front

What does the CNS consist of?

Back

Preview of the front of card 4

Card 5

Front

What is the main function of the CNS?

Back

Preview of the front of card 5
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