Lecture 10 Flashcards
Describe the main 3 features of a neuron and their associated function AND synapse
Most neurons have a cell body, an axon, and dendrites.
The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals.
Dendrites extend from the neuron cell body and receive messages from other neurons.
Synapses are the contact points where one neuron communicates with another.
The dendrites are covered with synapses formed by the ends of axons from other neurons.
Define neuron
Neurons are cells within the nervous system that transmit information to other nerve cells, muscle, or gland cells
Basic functional unit of
nervous system
Features:
Excitability or Conductivity
Draw and label a neuron
Lecture Slide Dendrites Cell body Axon Neural Impulse Myelin Sheath Terminal branches of axon
Pre and Post synaptic neuron
Synapse
junction point between two neurons.
typical chemical synapse between two neurons, the neuron from which the nerve impulse is generated and transmitted is called the presynaptic neuron.
The neuron to which the neurotransmitters (chemical messengers) bind is called the postsynaptic neuron.
Draw a synapse
Lecture slide: Vesicles Synaptic gap Neurotransmitters Neurotransmitter receptor presynaptic neuron. postsynaptic neuron.
Draw the diagram of action potential
Lecture slide
Describe the phases of action potential.
Hypo polarisation
initial increase of the membrane potential to the value of the threshold potential
Depolarisation
opens voltage-gated sodium channels and causes a large influx of sodium ions
Overshoot
inside of the cell becomes more and more electropositive, until the potential gets closer the electrochemical equilibrium for sodium of +61 mV.
Repolarisation
• sodium permeability suddenly decreases due to the closing of its channels.
• overshoot value of the cell potential opens voltage-gated potassium channels, which causes a large potassium efflux, decreasing the cell’s electropositivity.
Hyperpolarisation
a state in which the membrane potential is more negative than the default membrane potential
Neurotransmitters: Acetylcholine
excitatory neurotransmitter that triggers muscle contraction and stimulates the excretion of certain hormones.
Neurotransmitters: Dopamine
neurotransmitter involved in controlling movement and posture. It also modulates mood and plays a central rolein positive reinforcement and dependency.
Neurotransmitters: Gamma aminobutyric acid
inhibitory neurotransmitter that is very widely distributed in the neurons of the cortex.
Neurotransmitters: Serotonin
contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain
Neurotransmitters: Glutamate
excitatory neurotransmitter associated with learning and memory.
Neurotransmitters: Norepinephrine
that is important for attentiveness, emotions, sleeping, dreaming, and learning.
Describe Alzheimer’s:
is a syndrome due to disease of the brain, usually of chronic or progressive nature, in which there is impairment of multiple higher cortical functions, including memory, thinking, orientation, calculation, learning capacity, language and judgement.
4 main groups of Alzheimers
Early onset
Late onset
Atypical
Unspecified
Factor that increases risk of alzheimers
Age
-The risk of developing Alzheimer’s
disease increases with age.
Pathology of alzheimers
- extracellular deposition of beta amyloid-Aβ
- causes loss of long term potentiation, damages synapses, and kills neurons.
- shows selective neurotoxicity for the hippocampus and cortex
- intracellular accumulation of tau protein
- interfere with cellular functions by displacing organelles
-distorting the spacing of microtubules, they impair the axonal transport thus affecting the nutrition of axon terminals and dendrites
Genes and Alzheimers
(60% - 80 % of causation all known genes relate to beta amyloid)
Familial - onset less than 60y/o
- Chromosome 1, 14, 21, 50/50 chance
Non-familial (late onset)
- Chromsome 19
MECHANISM of alzheimers
- prevent the breakdown of a chemical messenger (acetylcholine) important for learning and memory
- The synthesis of acetylcholine from choline and acetyl– coenzymeA (Acetyl-coA) in presynaptic neurons is catalysed by the enzyme cholineacetyltransferase.
- When released, acetylcholine’s effects are mediated via pre- and post-synaptic muscarinic and nicotinic receptors.
- Results may be either excitatory or inhibitory. Released acetylcholine is broken down within the synaptic cleft by the enzyme acetylcholinesterase (AChE).
Cholinergic Pharmacology: Purpose of Ach
Ach is the neurotransmitter for
- The entire parasympathetic nervous system
(parasympathetic ganglions & effector cells) - Parts of the sympathetic nervous system (sympathetic ganglions, adrenal medulla, sweat glands)
3.Some neurons in the CNS
4.Somatic nerves innervating skeletal muscle.
4 Etiologies of Parkinsons
Cerebral atherosclerosis
Viral encephalitis
Side effects of several antipsychotic drugs
Environmental factors - Pesticides, herbicides, industrial chemicals
Parkinson disease neurochemistry
Loss of Dopaminergic (DA) Cells Located in Basal Ganglia causing an imbalance of Ach (excitatory neurotransmitter) and dopamine (inhibitory neurotransmitter) in the basal ganglia
Agents that Increase Dopamine functions (5)
Increasing the synthesis of dopamine - l-Dopa
Inhibiting the catabolism of dopamine - selegiline
Stimulating the release of dopamine - amphetamine
Stimulating the dopamine receptor sites directly - bromocriptine
Enhancing the release of dopamine - amantadine
L Dopa Therapy for Parkinsons
Dopamine Decarboxylase Converts L Dopa to Dopamine that gets Released from Basal Ganglia
