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Chapter 6

PHAR 100 Chapter Notes - Chapter 6: Peripheral Nervous System, Neuromuscular Junction, Autonomic Nervous System


Department
Pharmacology and Toxicology
Course Code
PHAR 100
Professor
Bill Racz
Chapter
6

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Lesson B.1 Physiological and Pharmacological Aspects of the Central and Peripheral Nervous
System
Objectives:
- Describe the components of the neuron
- Describe the process of synaptic transmission
- Describe the organization of the nervous system
- List some of the common transmitters in the brain
- Describe the organization of the peripheral nervous system
- List the transmitters in the autonomic nervous system, including their location and the receptors
which mediates their responses
Central nervous system: brain, spinal cord
- Controls all bodily functions
- The brain and spinal cord linked by peripheral nerve fibres
- Sensory nerve fibers carry messages from tissues to the brain or spinal cord
- Motor nerve fibres carry messages from the brain or spinal cord to the tissue
- The Forebrain:
o Cerebral cortex (cerebrum)
The largest part of the brain, rich in nerve cells
Composed of grey matter (outside) and white matter (inside)
Divided into 2 hemispheres containing lobes/regions of specific functions
Functions include: sensory and motor coordination, mental processes, intelligence,
memory, vision, judgment, thought, speech, emotions, consciousness
Can be stimulated or depressed by drugs
o Thalamus
Relay/impulse center
Coordinates information and painful sensations
o Hypothalamus
Control of involuntary functions (regulation of the heart, blood pressure, body
temperature, metabolism)
Controls feeding, drinking, sexual and emotional responses
Important influence on the limbic system
Neurons release factors which travel to the pituitary gland
o Pituitary
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Gland at the base of the brain which secretes hormones that control growth,
behaviour and metabolism of the body
Includes: follicle-stimulating hormone, thyroid stimulating hormone etc.
- The Midbrain:
o Links the forebrain with the hindbrain; relays information from the visual and auditory
stimuli
- The Hindbrain:
o Medulla (bulb)
Site of origin of many cranial nerves
Regulation of respiration (breathing center) and regulation of heart and blood
pressure
Controls some involuntary activity
Many drugs which depress respiration and blood pressure will do so by depressing
the medulla (ie. barbiturates)
o Cerebellum
Large, highly convoluted structure connected to the brain stem by large fibre tracts
Involved in coordination and posture
Influenced by drugs that cause ataxia (drunkenness) ie. Alcohol
Neurons functional unit of the brain (~10 billion nerve cells)
- Soma (cell body) contains a nucleus, cytoplasm, rough ER, smooth ER, many vesicles
(characteristic of active protein synthesis and secretion of substances
- Dendrites project from the soma and receive information from nearby neurons, usually short with
a highly complex branching pattern. Receptors are located on the membrane, when activated the
initiate an electric current down the axon
- Axon is a fibre that extends from the cell body, carrying an electrical impulse towards the synapse
- Synaptic Transmission:
o Junction between two neurons is called the synapse the synapse is commonly formed by
contact of the axon to the dendrites or cell body of another neuron. Transmission is
usually chemical in nature via synaptic transmitter or neurotransmitter involvement
o Transmission is unidirectional
o The nerve impulse (electrical activity) passes down a nerve axon and releases a chemical
substance in the synaptic cleft. The postsynaptic membrane contains receptors which bind
with the released compound to provoke a change in the permeability of the membrane
initiating ion (calcium) movement causing another electric wave down the postsynaptic
neuron
o The chemical transmitter is removed by processes involving (1) reuptake or (2) breakdown
via enzymes
- The specificity of receptors (proteins inserted in the cell membrane initially produced in the rough
ER) are specific to different endogenous transmitters these characteristics are exploited by drugs
- A drug stimulant is called an agonist, a drug inhibitor is called an antagonist
- There are many different types of receptors and receptor subtypes including:
- Acetylcholine:
o Cholinergic synapses and receptor
o Located in the peripheral nervous system (neuromuscular junction, autonomic ganglia,
parasympathetic postganglionic synapses), brain and spinal cord
o Nicotinic receptors are stimulated by nicotine: located in all autonomic ganglia, at
neuromuscular junctions, certain regions of the brain
o Muscarinic receptors are stimulated by alkaloids: located in regions of the brain
(involved in learning, memory and cognitive function)
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