Nervous System Flashcards
Describe the nervous system.
A network of fibres which span the body, coordinating a diverse range of voluntary and involuntary actions.
The nervous system involves both _____ and ______ actions.
Voluntary and involuntary
The nervous system is divided up into 2 main regions /divisions. Name them.
- Central Nervous System (CNS)
2. Peripheral Nervous System (PNS)
What is the Central Nervous System (CNS) made up of?
The brain and spinal cord.
What is the Peripheral Nervous System (PNS) made up of?
All peripheral nerves (any nervous tissue found outside the brain and spinal cord)
What is the name given to the information being sent to the brain from the peripheral nerves?
Sensory information
The nervous system provides us with 3 key categories of functions. What are they?
- Sensory (detection)
- Integration (processing)
- Motor (responding)
Give an example of sensory information.
Touch, vision, smell
Which region of the brain processes sensory information / input?
The sensory cortex
Define proprioception
Sense of body position
A deficiency in which vitamin, can be the cause of problems with nerve impulses up the spinal cord?
Vitamin B12
List 2 things that vitamin B12 is very important for in the body.
- Producing red blood cells
2. Producing the myelin sheath around nerve fibres
Why might a vitamin B12 deficiency present clinically as a loss of balance.
Because lack of vitamin B12 leads to demyelination (a lack of myelin) around the nerves running up through the spinal cord, which means that messages get to the brain a lot slower.
This means our awareness of where our body is (proprioception) can be compromised and we can be unsteady on our feet as a result.
What is myelin needed for?
To relay electrical signals quickly. It provides an insulating sheath around nerve cells.
List 3 functions of the nervous system.
- Detects internal and external environment changes.
- Processes sensory information
- Produces responses to sensory information.
What is the nervous system made up of?
Brain, spinal cord, peripheral nerves
Name the 3 types of neurons
- Sensory neurons
- Interneurons
- Motor neurons
Which type of neuron connects sensory and motor neurons in creating an output movement?
Interneuron
What does ‘autonomic’ mean?
Involuntary
Is the somatic nervous system voluntary or involuntary?
Voluntary
What can the peripheral nervous system (PNS) be sub-divided into?
The somatic nervous system (voluntary) and autonomic nervous system (involuntary)
What is the role of the peripheral nervous system?
Carrying messages to and from the CNS
What is the CNS?
Central Nervous System
What is the PNS?
Peripheral Nervous System
What is the role of the autonomic nervous system?
Control of involuntary body functions
Which 2 systems can the Autonomic Nervous System be sub-divided into?
Sympathetic and Parasympathetic nervous systems
What is the main role of the spinal cord?
Connecting the brain and the peripheral nervous system
Which is the ‘fight or flight’ part of the autonomic nervous system?
Sympathetic nervous system
Which is the ‘rest and digest’ part of the autonomic nervous system?
Parasympathetic nervous system
Which nervous system is important to regulate homeostasis?
Autonomic nervous system
What has overall control over the autonomic nervous system (ANS)?
The hypothalamus
Which body parts does the autonomic nervous system control / regulate?
Organs, glands, cardiac and smooth muscles.
Which sub-division of the ANS contains the vagus nerve?
The parasympathetic nervous system
Which major nerve is actually a branch off of the brain stem?
The vagus nerve
Which is the biggest nerve in the Autonomic Nervous System (ANS)
The vagus nerve
List one key function of the vagus nerve within the body
- Helps to promote digestion (mechanical and chemical)
Which sub-division of the ANS prepares our body to cope with threats?
The sympathetic nervous system
Where is the nerve origin in the sympathetic nervous system?
Thoraco-lumbar
Where is the nerve origin in the parasympathetic nervous system?
Cranio-sacral
What is the enteric nervous system?
The ‘brain of the gut’. (The gut-brain connection)
How many neurons make up the enteric nervous system?
Around 100 million neurons
What is the other name for the vagus nerve, and why?
The wandering nerve.
Because it has such an extensive anatomical course (it travels all around the thorax and abdomen)
Which key chemical is shared by the brain and the enteric nervous system?
Serotonin
Where is serotonin predominantly found?
In the digestive tract
95% of serotonin is found in the enteric nervous system
Nervous tissue contains 2 types of cells. What are they?
- Neurons
2. Neuroglia (glial cells)
What are neurons?
Electrically excitable cells that transmit electrical currents (information) up and down our nervous system.
What name is given to the structural and functional units of the nervous system?
Neurons
What is unique about neurons from a cell perspective?
They are electrically excitable
What % of our brain volume is made up of neurons?
Only 10%
Which type of cells make up 90% of brain volume?
Neuroglia (glial cells)
What is the role of neuroglia / glial cells?
They nourish, support and protect neurons, and form a mesh/framework that sticks all the neurons together.
“glial” = glue
How many types of glial cells are there?
6 types
How many types of glial cells are found in the CNS?
4
How many types of glial cells are found in the PNS?
2
What is a nerve?
A bundle of one or more neuron axons (in the peripheral nervous system).
List the parts of a neuron
Cell body Dendrites Axon Myelin sheath Nodes of Ranvier Terminal endings
For size perspective, how many neurons (individual cells) could fit on a pinhead?
30,000
What is the name given to the insulating covering that enables nerve impulses to travel quicker?
Myelin sheath
The myelin sheath only covers which part of the neuron?
The axon
What is the name given to the spaces between sections of myelin sheath covering the axon of neurons?
Nodes of Ranvier
What is a stimulus?
Anything able to generate an action potential
What is an ‘action potential’?
The electrical current that travels down the axon of a neuron, towards the terminal endings
Which part of a neuron contains the nucleus and cell organelles?
The cell body
What are dendrites?
The receiving part of the neuron.
The look like little tree branches coming out of the cell body. They communicate with other dendrites/neurons.
What is ‘grey matter’?
‘Grey matter’ describes the appearance of some of the tissue within the Central Nervous System. Grey matter is essentially lots of neuron cell bodies and dendrites, all bundled together.
What makes ‘white matter’ appear white?
The myelin sheath around axons.
What is ‘white matter’?
‘White matter’ describes the appearance of some of the tissue within the Central Nervous System. White matter is essentially lots of neuron axons, all bundled together.
What are ‘ganglia’?
Collections of neuron cell bodies clustered together in the Peripheral Nervous System.
Collections of neuron cell bodies clustered together in the CNS are known as _______.
Nuclei
What is the name given to the thin cylindrical projections within a neuron, which carry nerve impulses away from the cell body, towards another neuron?
Axons
Which part of the neuron carries the action potential?
The axon
Where might we find an axon of more than 1 metre in length (in the PNS)?
Sciatic nerve
What is the biggest nerve in the body?
The sciatic nerve
What is the name given to the membrane that covers axons?
The axolemma
What are axon bundles called in the central nervous system (CNS)?
Tracts
What are axon bundles called in the peripheral nervous system (PNS)?
Nerves
How many sensory tracts do we have going up the CNS to the brain?
2
How many motor tracts do we have going down the CNS from the brain?
1
If the tissue is healthy, at what rate can damaged axons regenerate?
1 - 2mm per day.
Which cells are non-excitable - neurons or neuroglia (glial cells)?
Neuroglia (glial cells)
Which cells in the nervous system are far smaller than neurons but 50x more prevalent?
Glial cells (neuroglia)
Which cells in the nervous system cannot undergo division and are set at birth?
Neurons
Which cells in the nervous system can undergo division?
Glial cells
List 3 functions of neuroglia
- Surround neurons & hold them in place.
- Supply neurons with oxygen & nutrients
- Destroy pathogens
- Remove dead neurons
How many types of neuroglia are there?
6
4 in the CNS, 2 in the PNS
Name the 4 types of glial cells in the CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal Cells
Name the 2 types of neuroglia in the PNS
Schwann Cells
Satellite Cells
Describe the appearance of astrocytes and explain where they’re found
Star-shaped with branching processes
Found in the central nervous system where they wrap around blood vessels.
Which type of glial cell is most numerous and largest?
Astrocytes
List 2 functions of astrocytes?
- Maintain the blood brain barrier
2. Hold neurons to their blood supply (physical support)
Oligodendrocytes are important for the production of ______
Myelin
_________ are the glial cells with immune functions
Microglia
What is the role of ependymal cells?
They produce a fluid called CSF, which bathes the brain and spinal cord.
What is the role of Schwann cells (neuroglia) in the PNS?
Producing the myelin sheath
What is the role of satellite cells (neuroglia) in the PNS
Support and nourishment
Which type of glial cells form the blood brain barrier?
Astrocytes
Name something that can damage astrocytes.
Heavy metals
What is the function of oligodendrocytes?
They myelinate neuron axons in the CNS
Name the phagocytic resident immune cells in the brain.
Microglia
What is CSF and which type of glial cells produce it?
Cerebro Spinal Fluid.
Produced by ependymal cells
Which epithelial glial cells have cilia that beat to circulate cerebro spinal fluid?
Ependymal cells
Which type of glial cell lines the 4 ventricles of the cerebrum and the central canal of the spinal cord?
Ependymal cells
Which type of glial cell repairs damage to axons in the PNS?
Schwann cells
Most dendrite connections and myelination is completed by the age of ____?
3
How many layers of myelin coat an axon / make up the myelin sheath?
Up to 100 layers
Which type of glial cell helps with support of neurons in the PNS and exchange of nutrients into the nervous system?
Satellite cells
What is an ion?
Give an example of one.
An ion is an electrically charged particle. E.g, Na+ (sodium)
Neurons are electrically excitable. What does this mean?
They can conduct an electrical current.
There are 2 types of electrical signal in a neuron. Name them.
- Graded potential
2. Action potential
What is ‘graded potential’?
The electrical signal that travels around the CELL BODY and DENDRITES of the neuron
What is ‘action potential’?
The electrical signal that travels down the AXON of the neuron.
List 3 differences between a graded potential and an action potential.
- Graded potential travels around the neuron cell body & dendrites. Action potential travels down the axon.
- Graded potential is for short distance communication. Action potential is for long distance communication.
- Graded potential will be activated / produce an electrical signal, regardless of the strength of stimulus. Action potential requires a stimulus beyond a certain threshold to be activated.
What 2 characteristics are graded potentials and action potentials facilitated by?
- Specific ion channels that can open and close when stimulated.
- A resting potential
What is ‘resting potential’?
A difference in charge across a neuron cell membrane (a negative charge within the neuron itself).
What is polarity?
Difference in electrical charge
What are ion channels and where are they found?
Transport channels for ions. They are transmembrane proteins.
Found in cell (neuron) membranes.
What are the 2 main ion channels in neuron membranes?
Sodium channels & potassium channels
Ion channels open in response to a stimulus. List 3 stimuli that would open an ion channel.
- Touch
- Change in voltage
- Hormones
What is the charge / resting potential in an axon that is at rest?
-70 mV (minus 70 millivolts)
A negative charge within the neuron.
Which 2 ions is extracellular fluid rich in?
Sodium (Na+) and Chloride (Cl-)
Does extracellular fluid carry a positive or negative charge?
Positive
Intracellular fluid is rich in which ion?
Potassium (K+)
Would you find large, negatively charged proteins inside or outside a nerve cell?
Inside
What does the sodium potassium pump do?
Maintains separation of charges between the inside and outside of a nerve cell (keeps the inside a - negative charge, and the outside a + positive charge).
It pumps 3 sodium (Na+) molecules out of the cell, for every 2 potassium (K+) cells that it pumps back in.
Transport of ions via the sodium potassium pump is an active transport process that requires ATP. True or false?
True
What is the sodium potassium pump?
An ion channel/pump found in neuron cell membranes, which maintains separation of electrical charge between the inside and outside of a nerve cell.
What is an action potential?
The formation of a nerve impulse
What are the 2 phases of an action potential?
- Depolarisation
- Repolarisation
(of the neuron cell membrane)
Explain what happens during the depolarisation phase of an action potential.
The normal (negative) cell membrane potential of -70 mV becomes positive and reaches +30 mV (because sodium ions flood the axon of the cell via sodium channels).
Explain what happens during the repolarisation phase of an action potential.
The normal (negative) cell membrane potential of -70 mV is restored. Potassium moves out of the axon.
What is depolarisation triggered by?
Stimulus of a nerve ending.
What is the threshold value that depolarisation of a neuron must reach (in millivolts), in order to generate an action potential?
-55 mV (minus 55)
Which ion is associated with increasing a charge in the axon of a neuron?
Sodium (Na+)
Which ion is associated with decreasing a charge in the axon of a neuron?
Potassium (K+)
At the peak of the action potential, the inside of the cell membrane is ___ mV more positive than the outside.
30mV
Which ion channels open more slowly - sodium channels or potassium channels?
Potassium channels
What helps to re-establish the resting membrane of an axon?
Movement of potassium out of the axon.
What is a refractory period?
A period of time after re-polarisation, in which a nerve cannot generate another action potential because Na+ and K+ are on the wrong sides of the cell membrane. An action potential is already in progress.
Which pump is busy working to restore the resting potential during the refractory period
The sodium potassium pump
What’s the difference between the absolute refractory period and the relative refractory period?
During the absolute refractory period, even a really strong impulse cannot generate an action potential.
During the relative refractory period, a larger than normal stimulus is needed to generate an action potential.
Why can’t an action potential be generated during the absolute refractory period?
“You can’t fire a gun when it’s already firing!” During the absolute refractory period an action potential is already in progress.
What is ‘conduction’?
The movement of a nerve impulse along the axon of a neuron.
What increases the speed of electrical transmission?
Myelin
Some neurons are unmyelinated. What does this mean?
Unmyelinated = they do not have a myelin sheath around their axons.
Name an unmyelinated nerve.
The olfactory nerve (sense of smell)
Which require more ATP for nerve impulse conduction - myelinated or unmyelinated neurons?
Unmyelinated axons require more ATP as they don’t have any myelin to conduct and speed up the action potential going along them. They are less energy efficient.
What is important/significant about the nodes of Ranvier?
They are the points along the axon at which there are high concentrations of Na gates (and no myelin).
What happens to action potentials at lower temperatures?
They are conducted slower
What are the nodes of Ranvier created by?
Gaps in the myelin sheath
What is the name given to the action potential appearing to jump from node of Ranvier, to node of Ranvier?
Saltatory conduction
What does ‘saltatory’ mean?
Jumping/leaping
Why is ice / cold often effective at reducing pain?
Because the cold temperature reduces the speed of the nerve impulses / pain impulses.
What are the 2 key types of nerve conduction?
- Continuous conduction
2. Saltatory conduction
How do local anaesthetics work?
They block Na+ gates/channels in the cell membrane, preventing them from opening, which stops an action potential being formed. This stops the nerve from transmitting the pain message.
They stop the electrical activity moving up sensory neurons.
If Na+ (sodium) can’t move into an axon, there won’t be an electrical impulse. True or false?
True
What are synapses?
Gaps between neurons / where neurons connect with one another, or a neuron connects with a muscle.
What are the ends of axon terminals called?
Synaptic end bulbs
The space between the synaptic end bulb of one neuron, and the next neuron is filled with __________ fluid.
Interstitial fluid
Do neurons physically touch each other?
No. There is always a small gap between them, filled with interstitial fluid.
What are neurotransmitters?
Nerve chemicals that carry nerve impulses across a synaptic cleft.
Neurotransmitters are stored in ________ vesicles.
Synaptic vesicles
Do neurotransmitters relay a message on, or stop electrical activity at that point?
Both. Neurotransmitters can have either excitatory or inhibitory effects on the post-synaptic (next) neuron.
Explain how a synapse transmits a nerve signal (4 phases).
- An action potential arrives at the synaptic end bulb and calcium channels open, flooding calcium into the synaptic end bulb.
- Increase of calcium concentration causes synaptic vesicles to release neurotransmitters into the synaptic cleft.
- Neurotransmitters diffuse across the synapse and bind to receptors on the next neuron (the post-synaptic neuron).
- The ion channels open in the post synaptic neuron. This results in either the action potential continuing to move down the next axon (excitatory neurotransmitter), or stops the action potential going any further (inhibitory neurotransmitter).
What is a synapse?
The meeting point between 2 neurons
What is a neurotransmitter?
A chemical messenger, released from a pre-synaptic terminal. It causes an effect on the post-synaptic cell.
Neurotransmitters are broadly put into 4 categories. Name these categories.
- Amino Acids
- Monoamines
- Peptides (neuropeptides)
- Unique molecules (i.e, acetylcholine)
List 6 different neurotransmitters.
Acetylcholine Nitric Oxide GABA Dopamine Serotonin Adrenaline / noradrenaline Endorphins Substance P
Following a nerve impulse, neurotransmitters need to be inactivated and removed for the process to be able to start again. This can be done in 3 different ways - list them.
- Reabsorption
- Breakdown by enzymes
- Diffusion
Which enzyme breaks down and causes reabsorption of serotonin?
MAO
Anti-depressants are often MAO inhibitors
Name a major excitatory neurotransmitter in the CNS, that plays a major role in memory and learning.
Glutamate (AKA glutamic acid)
Which major inhibitory neurotransmitter in the brain is formed from glutamate?
GABA
The neurotransmitter glutamate is produced from which amino acid?
Glutamine
The conversion of the neurotransmitter glutamate to GABA is dependant on availability of which vitamin?
Vitamin B6
Which inhibitory neurotransmitter, used by 1/3 of brain synapses, is essential in preventing neural over-activity?
GABA
Which neurotransmitter is enhanced by the allopathic drug diazepam (valium), to prevent anxiety?
GABA
The neurotransmitter serotonin is produced from which amino acid?
Tryptophan
95% of this neurotransmitter is produced in the enteric nervous system. Only 5% is located in the CNS.
Serotonin
The precursor to Serotonin is manufactured from the amino acid tryptophan. What is it called?
5-HTP (5-Hydrocytryptophan)
List 5 reasons that we need serotonin.
- Gut peristalsis (intestinal motility)
- Release of digestive secretions
- Mood regulation
- Pain regulation
- Sleep regulation (conversion to melatonin)
Name 1 thing that can lead to poor production of serotonin.
Poor gut function.
The neurotransmitter Dopamine is synthesised from which amino acid?
Tyrosine
Which key amino acid is needed for the production of thyroid hormones, adrenaline, noradrenaline and dopamine,
Tyrosine
List 2 things that the body uses dopamine for.
- Movement
- Sense of reward
- Regulating muscle tone
An increase in the levels of which neurotransmitter is associated with addiction?
Dopamine
Parkinsons Disease is associated with a lack of which neurotransmitter?
Dopamine
Which neurotransmitter is found in several areas of the brain, including the substantia nigra?
Dopamine
Dopamine depletion is associated with which disease?
Parkinsons Disease
Which neurotransmitter acts as a prolactin inhibitor (stops prolactin being released from the anterior pituitary)?
Dopamine
What group/category of neurotransmitters do adrenaline and noradrenaline fall into?
Monoamines
Name 2 neurotransmitters that are also hormones.
Adrenaline and noradrenaline
Which 2 enzymes break down dopamine?
MAO and COMT
What are neuropeptides?
Small proteins acting as neurotransmitters and hormones.
Which category of neurotransmitters work to influence levels of pain (increase or decrease pain)?
Neuropeptides
Name a type of neuropeptide (neurotransmitter) that works to reduce pain?
Endorphins (natural opioids)
What is an opioid?
A painkiller that works on opioid receptors
Which neuropeptide neurotransmitter amplifies feelings of pain?
Substance P
Which neurotransmitter plays a major excitatory role in the CNS and at neuromuscular junctions?
Acetylcholine (ACH)
Which neurotransmitter is involved in muscle contraction and cognition (the retrieval of memories from the brain)?
Acetylcholine
In which pathology would we see a deficiency in acetylcholine?
Alzheimers Disease
It’s thought that 90% of patients with Alzheimers Disease are deficient in which neurotransmitter?
Acetylcholine
Botox blocks the action of which neurotransmitter?
Acetylcholine
The neurotransmitter nitric oxide is produced from which amino acid?
Arginine
What is the role of the neurotransmitter Nitric Oxide?
Vasodilation
The effects of which neurotransmitter last for less than 10 seconds?
Nitric Oxide
Which neurotransmitter is increased, by the use of a GTN spray to relieve angina?
Nitric Oxide
Name 2 neurotransmitter breakdown enzymes.
- MAO (monoamine oxidase)
2. COMT
Name a natural MAO inhibitor.
St John’s Wort
What is a spinal tract?
An ‘elevator’ between the spine and brain in the CNS.
How many spinal tracts are there?
3.
Two send messages up, one sends messages down.
Perception occurs in the ______
Brain
Spinal nerves carry nerve impulses to and from the _______ _______
Spinal cord
Which structures combine to form peripheral nerves (all of which are individually named, ie, the sciatic nerve)?
Spinal nerves
What is a dermatome?
An area of skin supplied by a single particular spinal nerve.
If a spinal nerve is injured it can cause pain and altered sensation (tingling & numbness) in the associated _______
Dermatome
Do nerve fibres/neurons in the CNS have the ability to regenerate?
No. Once they’re gone, they’re gone.
Do nerve fibres/neurons in the PNS have the ability to regenerate?
Yes, but only if:
a) the cell body is still intact
b) Schwann cells are present
