biological basis of behavior part 1

Biological basis of behavior(1) Prof .Elham Aljammas May 2015

Biological basis of behavior
Neuronal activity
Activity in the Central nervous system begins at the cellular level, with both electrical and chemical processes. In psychology, we first study the activity of the central nervous system at the cellular level.

Biology+environment--------------behavior

Neuron

Biological basis of behavior

Neurons receive information via the dendrite and pass information down the axon to the synapse.
The basic unit of the nervous system,it hold the secret of how the brain work( nature of consciousness,transmission of impulses ,emotion & thought).
Neurons vary in size,appearance ,neurons of the spinal cord may have an axonof 3-4ft.long,brain neurons may have few thousands of an inch.
The nervous system in addition to the neurons consist of a large no. of non neuronal cells =glial(glue)cells which present in a ratio of 9/1(G/N)its function is to hold the neuron inplace,providing nutrient to neuron,& cleaning of neuronal environment.Uncontolled proliferation of glial cells is the cause of most brain tumors.
In human brain there is 10bil-1tril.N X9=no. of glial cells!
At the synaptic junction more than70 diff neurotransmitters have been identified.

Action Potential:

Excitatory impulses and inhibitory impulses alter a cells internal potential or charge. When a cell's potential reaches a certain level, the cell "depolarizes" or becomes positive, causing an action potential.
Electrical impulses passes along the axon in speed of 2-200miles /hr.

Ion Movement within the Action Potential:
The action potential causes a rush of sodium ions (positive) into the neuron and potassium ions (minus) out of the neuron, The cell "repolarizes" as the ions become balanced, often causing a "hyperpolarization".

Key in a lock

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As a result of the action potential, neurotransmitters are released into the synaptic junction. Specific neurotransmitters bind with specific receptor sites to allow the passage of chemicals into the receptor neuron.

The action potential causes a release of neurotransmitters which bind to the receptor site much like a key in a lock. This triggers a post-synaptic potential, which opens the post-synaptic membrane. Excess neurotransmitters are cleared from the synapse so future action potentials can occur

Biological basis of behavior

Reuptake of Neurotransmitter:
The terminal button of the axon reabsorbs (takes up) the left-over neurotransmitter in the synapse. This reduces the chance of the post-synaptic cell from being re-excited by the initial action potential.

Blocking the Receptor:

Antagonists can block the receptor site, thereby preventing neurotransmitters from binding with receptor sites. Drugs such as Curare, can cause lethal paralysis by preventing activity in motor neurons, including those which control the muscles in the lung. You may be more familiar with Novicaine, a centrally-acting blocker. After being injected with Novicaine at the dentist's office, you experience a loss of feeling, as Novicaine occupies or blocks sensory receptors

Biological basis of behavior

Drugs Acting as Transmitters:
Agonists, can act as neurotransmitters, thereby causing the post-synaptic membrane to "open" or "fire". A drug such as Mescaline mimics the neurotransmitters Dopamine and Norepinephrine which are responsible for initiating and maintaing arousal and alertness.

Drugs which Block Reuptake:

Cocaine, commonly known as a stimulant, blocks the reuptake of dopamine, seratonin, and norepinephrine, which play a role in regulation of mood. Initial use can cause elevated mood, as excess amounts are released. When the reuptake of these transmitters is blockes, the excess dopamine continues to excite the receptor. However, over time the body produces less and less, and the natural stores are depleted, resulting in decreased mood.

synaps

Synapse Overview/Summary
Cells communicate through electrical and chemical interactions.
Electric communication begins with Action Potential
Depolarization causes release of neurotransmitters
Chemical interactions are caused by release of neurotransmitters
Neurotransmitters cause a change in the post-synaptic cell
The post-synaptic cell can also be changed through:
drugs which act as neurotransmitters (agonists)
increase release of neurotransmitter
increase production of neurotransmitter
mimic presence of neurotransmitter
act directly on receptor
drugs which block receptors (antagonists)
drugs which cause neurotransmitters to remain (block re-uptake

thank you