Module 2: Section 1 (Introduction to Autonomic Pharmacology)

Question 1

What is the nervous system?

Answer 1

The nervous system is the body’s control and communication system.

Question 2

What does the nervous system consist of?

Answer 2

It consists of the brain, spinal cord, sensory organs, and all the nerves within the body.

Question 3

What does the nervous system control?

Answer 3

The nervous system functions to control all bodily functions, both voluntary and involuntary.

Question 4

What are the 3 basic functions of the nervous system? Provide an example.

Answer 4

1) Recognize: the nervous system recognizes changes in the internal or external environment.
- Ex: a change in the external temperature (28C vs 0C).

2) Process and Integrate: the nervous system perceives the changes in the environment.
- Ex: the body feels hot.

3) React: the nervous system reacts to changes in the environment by producing a response or an action to counteract the change.
- Ex: the body will sweat to compensate for increases in temperature. Once the body compensates for a change, it returns to baseline and prepares to recognize further changes.

Question 5

What are neurons?

Answer 5

Neurons, the functional unit of the brain, are nerve cells capable of generating and transmitting electrical signals.

Question 6

How do neurons commiunicate in the nervous system?

Answer 6

Neurons within the nervous system communicate by way of synaptic transmission (neurotransmission).

Question 7

What is the synaptic transmission (neurotransmission)?

Answer 7

Synaptic transmission is usually chemical in nature, meaning that the release of a substance is required in order to activate the other neuron or pass on the message.

Question 8

What are the steps of neurotransmission?

Answer 8

1) An electrical impulse will travel down the axon of a neuron.
2) When the electrical impulse reaches the end of the presynaptic neuron, it causes the vesicles (which contain neurotransmitters) to fuse with the presynaptic membrane, thereby releasing the neurotransmitters into the synaptic cleft.
3) The neurotransmitters will then diffuse across the synaptic cleft and bind w/ receptors on the postsynaptic membrane.
4) Activation of those receptors will cause a change in the permeability of the membrane, allowing ions such as Ca to move into the post synaptic neuron.
5) This changes the electrical activity of the membrane, thereby generating an electrical impulse, which will then travel down that neuron’s axon.
6) This process continues until the neuronal signal reaches the target organ, causing an effect.

7) The continuous presence of neurotransmitter in the synaptic cleft would prevent other nerve impulses from being communicated, effectively rendering the neuron useless.
- There are 3 mechanisms to remove them.

8) Once the neurotransmitters are removed from the synaptic cleft, the postsynaptic membrane is able to repolarize and prepare for the next neuronal impulse

Question 9

What mechanisms are used to remove neurotransmitters?

Answer 9

The continuous presence of neurotransmitter in the synaptic cleft would prevent other nerve impulses from being communicated, effectively rendering the neuron useless.

1) Neurotransmitters can be taken back up into the presynaptic neuron through transporters.
- Ex: Norepinephrine, dopamine, and serotonin are all removed from the synaptic cleft through transporters.

2) Neurotransmitters can be broken down by enzymes in the synaptic cleft.
- Ex: ACh is broken down by acetylcholinesterase (enzyme) into acetate and choline.

3) The neurotransmitter can be taken up into adjacent glial cells (cells that support neurons).
- Ex: Glutamate is taken up by adjacent glial cells

Question 10

Which one of the mechanisms listed is the most common mechanism by which neurotransmitters are removed from the synaptic cleft?

a) Neurotransmitters can be taken back up into the presynaptic neuron through transporters
b) Neurotransmitters can change conformation after a certain period of time to become inactive
c) Neurotransmitters can be broken down by enzymes in the synaptic cleft
d) Neurotransmitters can be taken up by glial cells

Answer 10

a) Neurotransmitters can be taken back up into the presynaptic neuron through transporters

Question 11

How is the nervous system divided?

Answer 11

• The central nervous system (consists of the brain and spinal cord)
• The peripheral nervous system (contains all the nerve fibres outside of the CNS)

Question 12

How is the peripheral nervous system divided?

Answer 12

The peripheral nervous system (PNS) can be further divided into sensory (afferent) and motor (efferent) divisions.

The motor division consists of the somatic nervous system and the autonomic nervous system (ANS).

The ANS is made up of the parasympathetic and sympathetic nervous system.

Peripheral nervous system 
~ Sensory 
~ Motor 
 - Somatic nervous system 
 - Autonomic nervous system
   • Parasympathetic nervous system
   • Sympathetic nervous system

Question 13

What is the sensory (afferent) division?

Answer 13

Transmits sensory information from the peripheral to the CNS.

Question 14

What is the motor (efferent) division?

Answer 14

Transmits motor commands from the CNS to the periphery.

Question 15

What is the autonomic nervous system?

Answer 15

Involuntary motor control of smooth and cardiac muscle

Question 16

What is the somatic nervous system?

Answer 16

Voluntary motor control of skeletal muscle

Question 17

What is the parasympathetic nervous system?

Answer 17

Rest and digest response

Question 18

What is the sympathetic nervous system?

Answer 18

Fight or flight response

Question 19

What does the autonomic nervous system do?

Answer 19

The ANS is a division of the PNS that controls involuntary responses.

It does so by influencing organs, glands, and smooth muscle, and is often involved in maintaining a stable internal environment.

In other words, the ANS governs vital bodily functions that are normally carried out without conscious effort. The ANS helps to control blood pressure, heart rate, bowel movement, urinary output, and sweating.

Question 20

What neurons are required for the autonomic nervous system (ANS)?

Answer 20

Within the ANS, two neurons are required to reach the target organ.

The first neuron’s cell body is in the CNS, and the second neuron’s cell body is in the ganglion (a mass of nerve cell bodies).

The neuron before the ganglia is termed the preganglionic nerve, while the neuron after the ganglia is termed the postganglionic nerve.

Question 21

What are the two divisions of the ANS?

Answer 21

1) Parasympathetic nervous system: responsible for the “Rest and Relax” response; activated under non-stressful conditions. The effects of the parasympathetic nervous system include pupil constriction, decreased heart rate, and increased digestive intestinal activity.
2) Sympathetic nervous system: responsible for the “Fight or Flight” response; activated under conditions of stress. The effects of the sympathetic nervous system include pupil dilation, and increased sweating, heart rate, and blood pressure.

Question 22

True or false: both the parasympathetic and sympathetic nervous systems have their higher centres in the brain which act to monitor and control the ANS.

Answer 22

True

These two systems normally act in a balanced and opposed fashion.

Question 23

Give some examples of medical conditions that involve an abnormal ANS function.

Answer 23

Hypertension, congestive heart failure, and atrial fibrillation

Question 24

True or false: most organs have dual innervation from both the parasympathetic and sympathetic nervous systems, but not all.

Answer 24

True

Question 25

Which one of these statements is correct?

a) Neurotransmission is usually terminated by diffusion of the transmitter out of the synaptic cleft.
b) Most neurotransmission is chemical in nature.
c) Neurotransmitters have specific binding sites on the cell membrane called retinoids.
d) Neurotransmission is a slow process, taking several minutes.

Answer 25

b) Most neurotransmission is chemical in nature.

Question 26

Which of the organs listed are targets of the autonomic nervous system? Say yes or no for each of a) to d)

a) Cardiac muscle
b) Skeletal muscle
c) Pituitary gland
d) Neurons in the forebrain

Answer 26

a) Cardiac muscle = yes
b) Skeletal muscle = no
c) Pituitary gland = no
d) Neurons in the forebrain = no