13. Nervous System I Workshop Flashcards
Describe the difference between the central nervous system and the peripheral nervous system
The CNS comprises the brain and spinal cord while the PNS is any nervous tissue outside of the CNS
The nervous system is a _________ of fibres which span the body, co-ordinating a diverse range of voluntary and ___________ actions. It transmits ______ between parts of the body and responds rapidly to changes within the internal and external ___________. It works alongside the _________ system to maintain __________.
network involuntary signals environment endocrine homeostasis
What is the role of the somatic nervous system?
It controls voluntary muscles and transmits sensory information to the CNS
What is being described by the following:
a. Processes sensory information, analyses, stores and makes decisions
b. Detects internal and external environmental changes
c. Produces a response to sensory information to effect change
a. Interneurons
b. Sensory neurons (Chemo-, Baro-, Osmoreceptors)
c. Motor neurons
Which nervous system controls involuntary movements
Autonomic
What effect does the sympathetic nervous system have on the following:
a. Pupil
b. Liver
c. Heart
d. Lungs
e. Gastrointestinal tract
a. Dilation
b. Stimulates the conversion of glycogen to glucose
c. Increase heart rate and blood pressure
d. Causes bronchodilation
e. Decreases motility and secretions
Name the specific body locations where the following branches of the ANS originate:
a. Sympathetic nervous system
b. Parasympathetic nervous system
a. Thoraco-lumbar
b. Cranio-sacral
Explain how the enteric nervous system is linked to the CNS.
Via the sympathetic and parasympathetic nerve fibres of the vagus nerve.
Describe the role of the following in the enteric nervous system:
a. Sensory neurons
b. Motor neurons
c. Interneurons
a. They monitor chemical changes via chemo-receptors and GI tract stretching via stretch-receptors
b. Governs the motility and secretions of the GIT and glands
c. Connects the two plexus
Define the following in terms:
a. Action potential
b. Nerve stimulus
c. Nuclei
d. Ganglia
e. Tracts
f. Nerves
a. The ability to create a nerve impulse
b. Anything that generates an action potential
c. Collections of neuronal cell bodies in the CNS
d. Collections of neuronal cell bodies in the PNS
e. Axon bundles in the CNS are called tracts
f. Axon bundles in the PNS are called nerves
Describe the main role of dendrites.
Dendrites are the receiving portion of the cell that communicates with other neurons/dendrites
Can axons regenerate? Explain.
If injured, axons can regenerate at a rate of 1-2mm per day, if the neuronal cell body is intact.
Describe TWO roles of the myelin sheath
Myelin sheath electrically insulates the axon and increases the speed of nerve conduction
State which vitamin is required as a co-factor in myelin production?
Vitamin B12
Describe ONE key difference between ‘grey matter’ and ‘white matter’.
Grey matter is mostly composed of cell bodies with dendrites and unmyelinated axons. White matter is composed primarily of myelinated axons.
Describe THREE key differences between ‘neurons’ and ‘neuroglial cells’.
Neurons are excitable while neuroglia are non-excitatory. Glial cells are far smaller than neurons and also 50 times more prevalent. They can also multiply and divide, unlike neurons.
List TWO key functions of neuroglial cells.
Surround and hold neurons in place
Supply nutrients and oxygen to neurons
Destroy pathogens and remove dead neurons
Name the different types of neuroglia that are found in the CNS and PNS respectively
CNS: Astrocytes, Microglia, Oligodendrocytes, Ependymal Cells
PNS: Schwann cells, Satellite cells
Name the neuroglial cell that:
a. Contributes to the blood brain barrier
b. Is phagocytic and is mobile in the brain
c. Provides structural support in PNS ganglia
d. Myelinates axons in the CNS
e. Produces cerebrospinal fluid
f. Myelinates axons in the PNS
a. Astrocytes
b. Microglia
c. Satellite cells
d. Oligodendrocytes
e. Ependymal cells
f. Schwann cells
Describe TWO key differences between ‘graded potential’ and ‘action potential’.
Graded potential is for short distance communication, occurs in dendrites and cell bodies and has no threshold. Action potential is for long-distance communication, is propagated along the axon and there is a threshold that has to be reached for it to take place.
Name TWO characteristics that facilitate graded and action potentials.
- Specific ion channels can open and close when stimulated
- Electrical difference accross the cell membrane (resting potential)
Name TWO stimuli that trigger ion channels
- Chemicals (hormones)
- Changes in voltage
- Mechanical pressure
Neurons at rest posess an _____________ gradient across the cell membrane. This is created by the build-up of __________ ions on the inside of the cell membrane relative to the extracellular fluid which contains more ___________ ions. The separation of charges create __________ energy. The resting potential is approximately_________ mV. Cells exhibiting a membrane potential are said to be ____________ or charged.
electrochemical negative positive potential -70 polarised
Describe in detail the resting potential of neurons
The resting potential is created by a build up of negative ions on the inside of the cell membrane, relative to the extracellular fluid:
- The extracellular fluid is rich in Na+ and Cl- ions and carries a positive charge.
- The intracellular fluid is rich in K+ and large negatively charged proteins and phosphates which cannot leave the cell, thus rendering a negative charge inside the cell relative to the outside.
- As the Na+ and K+ try to move back to equalise the charge, the separation of charges is maintained by the sodium-potassium pump which pumps 3 Na+ out for every 2 K+ it pumps in, using ATP.
Describe in detail all steps in the following processes:
a. Depolarisation
b. Repolarisation
a. Depolarisation is triggered by stimulation of a nerve ending. The threshold value of -55mV must be reached in order to generate an impulse. Na+ channels open, allowing Na+ to flood into the cell up to about +30mV, thus letting a positive charge build up inside the cell.
b. K+ channels open much more slowly than Na+ channels, so just as Na+ channels are closing, the K+ channels open, allowing K+ to flood out of the cell, restoring the membrane potential to -70mV.
Explain what is meant by the:
a. Refractory period
b. Absolute refractory period
c. Relative refractory period
a. The period of time after the repolarisation in which a neuron cannot generate another action potential since Na+ and K+ are on the wrong sides of the membrane
b. During the absolute refractory period, not even a strong impulse can generate an action potential
c. During the relative refractory period, a larger than normal stimulus is needed to generate an action potential
Describe the role of the Nodes of Ranvier.
At the nodes of ranvier, there are high concentrations of Na+ gates, causing the current to appear to jump from node to node.
Describe in detail how the ‘synapse’ transmits a signal.
When the action potential arrives at the synaptic end bulb, the depolarisation causes Ca2+ to flood in which causes exocytosis of synaptic vesicles, causing neurotransmitters to be released into the synaptic cleft.
Neurotransmitters diffuse accross the synapse and bind to receptors on the post-synaptic neuron, opening the ion channels, generating an action potential in the post-synaptic nerve.
Explain why ‘ice’ is applied to an injury.
To dampen the pain signals travelling from the site of injury to the brain.
Which category do the following neurotransmitters belong to?
a. GABA
b. Dopamine
c. Acetylcholine
d. Serotonin
a. Amino acid
b. Monoamine
c. Unique molecules
d. Monoamine
Explain TWO differences between ‘excitatory’ and ‘inhibitory’ neurotransmitters.
Excitatory neurotransmitters causes depolaristation of the post-synaptic neuron and causes Na+ ion channels to open, making the inner membrane more positive.
Inhibitory neurotransmitters causes hyperpolarisation of the post-synaptic neuron by causing the K+ ion channels to open and the inner membrane to become more negative.
