The NERVOUS SYSTEM Flashcards
master all mntanami
what makes up the CNS
The spinal cord and the brain
what makes up the peripheral nervous system
nerves
what are neurons and how do they function
cells responsible for nervous system signaling
they are specialized for communication.
what are dendrites
be able to identify these Mnumzana
cytoplasmic extensions of the body
they receive information from other neurons and receptors
define an axon and its function
tube of the cell membrane
enclosed with the myelin sheath
it transmits Action Potential away from the cell body
what is the function of Schwann cells
to create fatty myelin sheath in PNS
produce myelin
what are oligodendrocytes
myelinating cells in the CNS
demyelination definition
loss of myelin sheath in the axons
caused by neurodegenerative autoimmune diseases
diseases caused by demyelination of the axons
multiple sclerosis
Guillain Barre Syndrome
Acute encephalomyelitis
what is multiple sclerosis
an autoimmune disease that involves the loss of oligodendrocytes
the immune system attacks the nervous system leading to demyelination
disrupts the CNS from communicating
how is Ms diagnosed?
based on signs and symptoms
supporting imaging and laboratory testing
(neuroimaging is used– which is the analysis of the cerebrospinal fluid and action potentials)
during MS diagnosis using neuroimaging, what is the cerebrospinal fluid tested for
the cerebrospinal fluid is tested for Oligoclonal bands of IgG on electrophoresis( which are inflammation markers found in 75% to 85% of people with MS)
what are the 3 stages of information processing?
- Input( sensory input) gathering of information
- Integration- processing of information
- Motor output- response to the information transmitted
what are the 2 cells that make up the nervous system
neurons(20% of the nervous system)
A-N-D
glia cells
what are the 3 types of neurons
- sensory( afferent) neurons
- Interneurons- connect neurons to specific regions of the CNS
- motor ( efferent) neurons
What are the 4 types of Glia cells
- Microglia
- Astrocytes
- Oligodendrocytes and Schwann cells
- Ependymal cells
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what are glia cells?
glia means glue, and hence these cells can be understood to support the structure of the nervous system
maintain homeostasis
do not generate impulses
neurons initiate action potentials
what is ACTION POTENTIAL?
transient (only lasting for a short time) alteration of the transmembrane voltage across an excitable membrane in an excitable cell
Generated by the activity of voltage-gated ion channels embedded in the membrane.
definition of the resting/membrane potential
the difference in charge between the cell’s membrane and extracellular fluid when the cell is not electrically charged.
it results from ionic gradients
what is the function of the sodium/potassium pump
prevents leaking of ions and also prevents the cell gradients from running down.
the resting potential of neurons is -70mV. the pump maintains this PUMP.
what happens if the resting potential of -70mV changes?
a neuron is triggered to fire and send electrical impulses.
there are two types of ion channels. What are these?
active channels
passive channels
what are graded potentials?
short-lived depolarizations or hyperpolarizations of the membrane
can only act as signals over short distances
what is the difference between action potentials and graded potentials?
basically,
the sum of graded potentials that are enough to reach the triggering threshold is called ACTION POTENTIALS
it is only an action potential if it is greater than the threshold potential
explain what happens during hyperpolarization
membrane potential becomes negative(the cytoplasm/ inside of the membrane) becomes negative
K+ open and increase permeability to K+
hyperpolarization occurs after depolarization. as K+ ions exit, the inside of the cell because less and less positive…the graph goes down.
potential approaches -92mV
explain what happens during depolarization
membrane potential becomes more positive as the opening of Na+ channels increases the permeability of Na+
potential approaches E(Na)= +62mV
the change in the postsynaptic potential can be inhibitory or excitatory
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WHAT ARE THE METHODS BY WHICH IONS ENTER AND EXIT CELLS»>?
- Diffusion
- Ion channels
` passive
` voltage gated-> open in response to voltageLigand-gated--> open in response to chemicals
Stretch-gated—> mechanically transformed - Ion pumps–which expand energy. eg. the sodium/ potassium pump.
what is the role of voltage-gated ion channels in the Action Potential?
regulate the action potential by controlling what exits and enters the cell (Na+ or K+)
Allow Na+ to enter the cell during depolarization
Allow K+ to exit the cell during repolarization and hyperpolarization.
how does the depolarization ( action potential) spread/ travel down the axons?
the influx of positive charges attracts negative charges inside the CELL, and repulses POSITIVE charges.
Because the Na+ channels have closed and the K+ continues to exit the cell, the membrane cannot depolarize again.
The action potential continues to travel down the AXON.
what is saltatory conduction?
The action potential travels down the axon by jumping from Node to Node.
saltatory conduction increases the speed of nerve impulse transmission
unmyelinated= 2,3 m/s Myelinated= 110m/s
what advantage does saltatory conduction prove in nerve impulse transmission?
saves neuron energy, as it Prevents slow inward leak of Na+ and outward leak of K+ because maintaining membrane potential requires ENERGY>
briefly explain how neurotransmitters are released?
Neurotransmitters are stored in synaptic vesicles at the ends of axons
AP reaches synaptic terminal it depolarises the terminal pre-synaptic membrane opening voltage-gated Ca2+ channels. Ca2+ then enters.
Calcium triggers exocytosis of neurotransmitters (held in membrane bound vesicles) into the synapse
Neurotransmitter diffuses across synaptic cleft – effect either direct or indirect
Many receptors for neurotransmitters are ligand-gated channels
what happens to neurotransmitters after they are released from the presynaptic neuron.
- taken back presynaptic neurons and be repackaged into membrane-bound vesicles
- Destroyed by enzymes in the cleft
- diffuse away from the synaptic cleft and into circulation where they are later destroyed.
- Glia cells take up neurotransmitters and use them as a source of energy.
what does the response of postsynaptic cell to neurotransmitter depend on?
- Type of neurotransmitter
- The concentration of the neurotransmitter
- Types of receptors and chemically sensitive ion channels in the postsynaptic membrane.
there are 8 examples that you need to know
what is adrenaline responsible for
flight or fight response
what is noradrenaline(norepinephrine) responsible for?
concentration transmitter
has excitatory or inhibitory effects in CNS and autonomic division of PNS
IN sympathetic nervous system, it increases heart rate, metabolizes fat, and increases muscle readiness
What is dopamine
Pleasure neurotransmitter
feeling of pleasure
affects mood, sleep, appetite, and sexuality
can be both inhibitory or excitatory
found inside the brain, plays a role in motor control, motivation, arousal, reinforcement and reward
motivation, reward and addiction.
Serotonin?
Mood neurotransmitter–
major targets for antidepressant drugs( many are Selective Serotonin Reuptake Inhibitor(SSRIs) increase concentration of serotonin in the synaptic cleft.
eg. Prozac (fluoxetine), Zoloft, Fontex- Enhance effect of serotonin by inhibiting its uptake after release.
what is GABA
calming neurotransmitter
Acetylcholine?
Learning neurotransmitter
most common- muscle simulation, memory and learning
excitatory or inhibitory in CNS depending on the type of receptor.
shortage of ACh leads to alzheimer’s disease, mental imparement
Glutamate?
Memory neurotransmitter
Endorphins?
Euphoria(a feeling or state of intense excitement and happiness) neurotransmitter
what is Botulinum toxin or Botox?
Neuroprotein produced by the bacterium Clostridium botulinum
prevents the vesicle where ACh is stored from binding to the membrane where the neurotransmitter can be released
prevents muscle contraction for 3-4 months.
What are biogenic amines?
derived from amino acids
1.catecholamines- produced by amino acid- tyrosine
they include Epinephrine (adrenaline) , norepinephrine and dopamine.
2. Indolamines- derived from amino acid tryptophan
include serotonin
what is Attention Deficit Hyperactivity Disorder
………..
DOPAMINE DISORDERS
- Parkison’s disease
- Schizophrenia
- Amphetamines and cocaine
- LSD and Mescaline ( psychoactive drugs)
what is Parkinson’s disease????????
Associated with reduced levels of dopamine neurons in the brain.
what is Schizophrenia?
Associated with abnormal levels of dopamine