CHAPTER 4

Pharmacology

WHAT IS THE DIFFERENCE BETWEEN CNS AND PNS?

• The brain + the spinal cord– The center of integration and control

• The nervous system outside of the brain and spinal cord

• Consists of:– 12 Cranial nerves

» Carry info to and from the brain– 31 Spinal nerves

» Carry info to and from the spinal cord• 2 divisions:

2A. Somatic Nervous System (SNS) (voluntary)2B. AUTONOMIC NERVOUS SYSTEM (ANS) (involuntary)

--> *SANS & **PANS

NERVOUS SYSTEM – A reviewIt is divided into 2 MAJOR categories:

1.THE CENTRAL NERVOUS SYSTEM (CNS)

2. PERIPHERAL NERVOUS SYSTEM (PNS)

DOES THE PNS CONTAIN SENORY, MOTOR OR BOTH?

THE PNS USE NEURONS THAT ARE SPECIALIZED TO CONDUCT INFORMATION

FROM ONE PART OF THE BODY TO ANOTHER.

BOTH

PNS – WHAT DOES THE SOMATIC NERVOUS SYSTEM CONTOL?

CONTROLS VOLUNTARY SKELETAL MUSCLECONDUCTS SENSORY INFORMATION

FIBERS PASS FROM SPINAL CORD DIRECTLY TO THE STRIATED MUSCLES

VOLUNTARY MUSCLE

IS THE ANS VOLUNTARY OR INVOLUNTARY

THE ANS FUNCTIONS AS AN AUTOMATIC MODULATING SYSTEM FOR MANY BODILY

FUNCTIONS.

IT IS THE PART OF PNS CONSISTING OF MOTOR NEURONS THAT CONTROL

INTERNAL ORGANS.

IT CONTROLS THE BODY’S ACTIVITIES THAT YOU DON’T THINK ABOUT:

INVOLUNTARY

INVOLUNTARY

WHAT IS THE FLIGHT AND FIGHT RESPONSE?

• shocks physiologic processes into action during environmental and internal stress

• copes with sudden emergencies

SANS -

WHAT IS MYDRIASIS?

DILATED PUPILS

The SANS stimulates the radial smooth muscles, producing an increase in pupil size

If PANS & SANS could talk…

The afferent (sensory) fibers say: “Hey…What’s happening?”

The central integrating areas exclaim: “Let’s coordinate all this info! Hey what

did you find out?” While, the efferent (peripheral) motor PREGANGLIONIC & POSTGANGLIONIC

fibers could respond like: “Begin sweating! Heart begin palpitating!”

ANS PANS

& SANS

WHAT IS THE SPACE BETWEEN THE PREGANGIOLIC AND

POSTGANGLIONIC FIBERS?

The postganglionic neuron originates in the ganglia and

innervates the effector (or target) organ or tissue

THE SYNAPSE AREA

ARE PREGANGLIONIC FIBERS LONG OR SHORT?

PREGANGLIONIC FIBERS OF THE PANS ARE RELATIVELY LONG AND EXTEND NEAR

TO OR INTO THE INNERVATED ORGAN, WHICH LEADS TO A DISCRETE RESPONSE

POSTGANGLIONIC FIBERS, ORIGINATING IN GANGLIA (GANGLION/SYNAPSE) , ARE

USUALLY SHORT AND TERMINATE ON THE INNERVATED TISSUE

LONG

Let’s talk about SANS • NOTE: there is a difference in the

length on the preganglionic fibers in the SANS vs the PANS

• In the SANS it is OPPOSITE:–Pre-ganglion fiber is short–Post-ganglion fiber is long

• Post-ganglion fibers will terminate at the effector organ or tissue

ANS SANS

SANS originate from the

thoracic to the lumbar

portion of the spinal cord

Preganglionic = short

Postganlionic = long

PANS orginate from

the cranial nerves and

sacral segments of

the spinal cord

Preganglionic = long

Postganlionic = short

WHAT ARE PARASYMPATHOMIMETIC

AGENTS?

1. Cholinergic (parasympathomimetic) agents Classified as either direct or indirect

acting agents.Direct acting drugs act directly on

the parasympathetic receptors (Eg. Pilocarpine acts on Nicotinic).

Indirect acting drugs either cause release of neurotransmitter which then goes to the receptor site OR they inhibit the enzyme cholinesterase (EG: Sarin (nerve gas) HAS no therapeutic use; it was used on a subway in Japan to poison riders) Table 4-3, p.39

(PANS)

WHAT IS BRADYCARDIA?

DECREASED HEARTRATE

WHAT DRUG IS USED IN PARKINSONS DISEASE?

An anticholinergic drug such as benztropine (Cogentin) reduce the tremors and rigidity associated with Parkinson and drug-induced Parkinson disease

used occasionally in combination with levodopa

COGENTIN

WHAT IS USED TO TREAT MOTION SICKNESS?

Scopolamine (CNS depressant action) is used to treat motion sickness

SCOPOLAMINE

WHAT ARE THE NEUROTRANSMITTERS IN SANS?

1. EPINEPHRINE: IS RELEASED WITH STIMULATION FROM THE ADRENAL MEDULLA

AND DISTRIBUTED IN THE BODY VIA THE BLOOD

2. NOREPINEPHRINE (NE) : MAJOR TRANSMITTER RELEASED AT THE TERMINAL ENDINGS OF THE

SANS

3. DOPAMINE: RECEPTORS ARE IMPORTANT IN THE BRAIN AND SPLANCHNIC AND RENAL

VASCULATURE

WHAT ARE ADRENERGIC AGENTS USED FOR IN DENTISTRY?

• Used in dentistry for their vasoconstrictive actions (hemostasis) on blood vessels.

• Added to local anesthetics to prolong the action of the LA, to reduce the risk for systemic toxicity, and to help to create a dry field.

VASOCONSTRICTION

WHAT IS EPINEPHRINE REVERSAL?

(SANS)

Adrenergic Blocking Agents

Clients pretreated with α-adrenergic blocking agents and then given epinephrine

exhibit a predominance of beta effects (vasodilation), which lowers BP

This is called EPINEPHRINE REVERSAL because BP goes down rather than up

α-adrenergic blocking agents