Lesson B1 - PHYSIOLOGICAL AND PHARMACOLOGICAL ASPECTS OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM

Question 1

The nervous system can be divided into two main components

Answer 1

the central nervous system (the brain and spinal cord) and the peripheral nervous system

Question 2

afferent or sensory nerve fibres which carry messages to the brain, and efferent nerve fibres which carry messages

Answer 2

from the brain and spinal cord to tissues.

Question 3

The efferent system is divided into motor nerves which innervate skeletal muscle, and

Answer 3

the autonomic nervous system.

Question 4

The central nervous system (CNS) controls

Answer 4

all bodily functions

Question 5

It consists of a central part, the

brain and spinal cord, linked to

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a peripheral part, nerve fibres

Question 6

The sensory nerve fibres carry

messages from tissues to the brain or spinal cord, and the motor nerve fibres carry messages

Answer 6

from the brain or spinal cord to the tissues.

Question 7

Three main parts of the brain

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1. Forebrain
2. Midbrain
3. Hindbrain

Question 8

The forebrain: cerebral cortex =

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This is the largest part of the brain which is very rich in nerve cells. It is composed of grey matter (outside) and white matter (inside); it is divided
into lobes or regions, each with specific functions

Question 9

The forebrain: Thalamus:

Answer 9

A relay centre; from here impulses are relayed to the cerebral cortex

Question 10

The forebrain:Hypothalamus:

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A very important area; consists of various specialized regions of nuclei
located near the base of the skull. The functions are to control the involuntary functions of
the body that are necessary for living, e.g. regulation of heart, blood pressure, body
temperature, and metabolism

Question 11

The forebrain: Pituitary

Answer 11

A small gland located at the base of the brain which secretes hormones that
control growth, behaviour and metabolism of the body through the action of these
hormones on peripheral tissues

Question 12

The Midbrain

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The midbrain is the area that links the forebrain with the hindbrain.

Question 13

The Hindbrain

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Medulla (the bulb): This is the site of origin of many cranial nerves. It is where
regulation of respiration (breathing centre) and regulation of heart and blood pressure
occurs

Cerebellum: The cerebellum is a large, highly convoluted structure connected to the brain
stem by large fibre tracts. It is responsible for coordination and posture

Question 14

The functional unit of the brain

Answer 14

is the neuron

Question 15

each nerve cell or neuron has three

parts:

Answer 15

The cell body or soma contains a nucleus and surrounding cytoplasm which is packed with
rough endoplasmic reticulum, a network of smooth endoplasmic reticulum, and abundant
vesicles which can be secreted.

The dendrites function as the receiving antennae for incoming information, are usually
short, and can have highly complex branching patterns.

The axon, a single fibre that extends from the cell body and ends at a synapse. The axon
carries signals away from the cell body.

Question 16

In order for the brain to function properly, the nerve cells (neurons)

Answer 16

must communicate with each

other.

Question 17

The junction between two neurons is called the

Answer 17

synapse

Question 18

The synapse is commonly formed by contact of the

Answer 18

axon belonging to one neuron with a dendrite or

the cell body of another neuron.

Question 19

The passage of a signal from one neuron to

another neuron is called

Answer 19

synaptic transmission

Question 20

Synaptic transmission is usually

Answer 20

chemical in nature

Question 21

Substances mediating synaptic transmission are

Answer 21

synaptic transmitters

Question 22

In chemical transmission, the

release of a transmitter substance is required in order to

Answer 22

activate the other cell or pass on the

message.

Question 23

The nerve impulse (electrical activity) passes down a nerve axon and releases

Answer 23

a chemical substance into the synaptic cleft.

Question 24

The postsynaptic membrane contains binding sites for the

chemical transmitter. These binding sites are called

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receptors

Question 25

The binding of the chemical transmitter to the receptor usually provokes a change in the permeability of the membrane and ions (calcium) move across the membrane, causing

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a change in electrical activity of the | membrane and this electrical activity is passed along to the next cell

Question 26

. To | prevent the synapses from becoming non-functional, the chemical transmitter is

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removed by one of two major mechanisms: broken down by enzymes or taken back up into the presynaptic structure.

Question 27

, after release into the synaptic cleft, the neurochemical transmitter or messenger binds to specific molecules known as

Answer 27

receptors

Question 28

Receptors are

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proteins synthesized in the rough endoplasmic reticulum, transported to different parts of the cell and inserted into the cell membrane of the cell body, dendrites and axons.

Question 29

each endogenous transmitter usually has its own

Answer 29

specific receptor

Question 30

When the transmitter binds to | the receptor, it

Answer 30

elicits a specific response.

Question 31

Drugs can either stimulate a receptor

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called agonist, or inhibit action on a receptor (called antagonists)

Question 32

Acetylcholine:

Answer 32

. Cholinergic receptors have two broad classifications. Those that are stimulated by nicotine are called nicotinic receptors. Nicotinic receptors are found in all autonomic ganglia, at the neuromuscular junction, and in certain regions of the brain. Muscarinic receptors are stimulated by the alkaloid, muscarine, and are found in a wide array of the regions of the brain.

Question 33

Serotonin:

Answer 33

Serotonin and its receptors are found in the upper brain stem, with significant amounts in the pons and medulla, hypothalamus, hippocampus, and cerebral cortex

Question 34

Dopaminergic pathways occur predominantly in three areas:

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hypothalamus, basal ganglia and | brain stem, and midbrain

Question 35

Dopaminergic pathways are involved in control of some hormonal systems (hypothalamus), motor coordination (basal ganglia), and motivation and

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reward

Question 36

There are several subclasses of dopamine receptors. The two most important are D1 and D2. D1 receptors, when activated by dopamine, are excitatory and D2

Answer 36

receptors are inhibitory.

Question 37

Norepinephrine pathways originate in the brain stem and send projections to the cerebral cortex, hypothalamus, limbic system, and the

Answer 37

cerebellum.

Question 38

There are a large number of receptor types for | norepinephrine. The two main classes are α and β. Activation of these receptors usually leads to

Answer 38

excitation of the cell, but one of the subclasses of these receptors, when activated, is inhibitory.

Question 39

Glutamate: Glutamate or glutamic acid is one of the more important

Answer 39

amino acid | neurotransmitters in the brain.

Question 40

Gamma-aminobutyric acid (GABA): GABA is the main inhibitory neurotransmitter in the

Answer 40

CNS

Question 41

GABAergic neurons and receptors are found in high concentrations in the cerebral cortex, hippocampus and

Answer 41

cerebellum.

Question 42

A number of CNS depressants (e.g. barbiturates and | benzodiazepines) bind to the

Answer 42

GABA receptor.

Question 43

Opioid peptides: There are three main classes of opioid peptides:

Answer 43

enkephalins, endorphins, and | dynorphins.

Question 44

They have varying degrees of selectivity for one of the opioid receptors

Answer 44

mu (μ), delta (δ) or kappa (κ).

Question 45

The μ opioid receptor subtype is most abundant in the cerebral cortex, hypothalamus, brain stem, and part of the spinal cord. This distribution is consistent with their involvement

Answer 45

in pain regulation.

Question 46

The δ opioid receptor is concentrated in the olfactory system and various limbic structures where they play an important role in

Answer 46

olfaction, motor integration (coordination), | reward, and cognitive (thinking) functions

Question 47

The κ receptors are abundant in the caudate-putamen and hypothalamic sites and are involved in regulation of food intake, water balance, pain perception, and

Answer 47

control of the endocrine system.

Question 48

The efferent component of the peripheral nervous system consists of the motor nerves and

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the autonomic nervous system.

Question 49

The autonomic nervous system (ANS) is involved in maintaining a

Answer 49

stable internal environment

Question 50

the autonomic nervous | system is often called the

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involuntary nervous system

Question 51

The Autonomic Nervous system has two distinct parts.

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1. Sympathetic (system) | 2. Parasympathetic (system)

Question 52

The parasympathetic and sympathetic systems normally act in a

Answer 52

balanced and opposite fashion

Question 53

Parasympathetic system: General stimulation of this system promotes or increases

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the vegetative functions of the body.

Question 54

At rest, the parasympathetic type of activity is the predominant activity. The sympathetic activity is largely

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inhibited.

Question 55

Sympathetic system: General stimulation of this system results in the mobilization of resources to prepare the body to

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meet emergencies.

Question 56

The mass sympathetic discharge results in increased | activity of many functions of the body, including

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increased heart rate, blood pressure, blood | supply to the tissues, rate of cell metabolism, and blood glucose

Question 57

As it is stress that usually excites the sympathetic system, it is frequently said that the sympathetic system provides extra energy to the body for a state of stress, and this is often called the

Answer 57

alarm reaction or stress reaction

Question 58

Acetylcholine is the

Answer 58

transmitter at all autonomic ganglia and the receptors are designated as nicotinic

Question 59

The transmitter at the postganglionic parasympathetic nerve ending is acetylcholine and the synapse

Answer 59

is cholinergic

Question 60

The transmitter at the postganglionic sympathetic nerve ending is norepinephrine and these receptors have been

Answer 60

designated adrenergic

Question 61

It is prudent to consider three of these types of adrenergic receptors. Alpha (α) receptors are located predominantly on

Answer 61

smooth muscle, e.g. blood vessels, gastrointestinal | muscle, and uterus.

Question 62

Beta (β) receptors can be sub-divided into β1 and β2. β1 receptors are found in the heart, and when activated, increase the force and rate of contraction of the heart. β2 receptors are found in the lungs, blood vessels, gastrointestinal muscle and uterus, and activation of these receptors leads to

Answer 62

muscle relaxation