Lecture 10

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.

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

Lecture Slide Dendrites Cell body Axon Neural Impulse Myelin Sheath Terminal branches of axon

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.

Lecture slide: Vesicles Synaptic gap Neurotransmitters Neurotransmitter receptor presynaptic neuron. postsynaptic neuron.

Lecture slide

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

excitatory neurotransmitter that triggers muscle contraction and stimulates the excretion of certain hormones.

neurotransmitter involved in controlling movement and posture. It also modulates mood and plays a central rolein positive reinforcement and dependency.

inhibitory neurotransmitter that is very widely distributed in the neurons of the cortex.

contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain

excitatory neurotransmitter associated with learning and memory.

that is important for attentiveness, emotions, sleeping, dreaming, and learning.

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.

Early onset Late onset Atypical Unspecified

Age -The risk of developing Alzheimer’s disease increases with age.

• 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

(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

• 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).

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.

Cerebral atherosclerosis Viral encephalitis Side effects of several antipsychotic drugs Environmental factors - Pesticides, herbicides, industrial chemicals

Loss of Dopaminergic (DA) Cells Located in Basal Ganglia causing an imbalance of Ach (excitatory neurotransmitter) and dopamine (inhibitory neurotransmitter) in the basal ganglia

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

Dopamine Decarboxylase Converts L Dopa to Dopamine that gets Released from Basal Ganglia