The Autonomic Nervous System and the Adrenal Medulla

What are the 3 most important factors controlled in the brain stem?

1- Arterial pressure 2- Heart rate 3- Respiratory Rate

The postganglionic sympathetic nerve fibers to what parts of the body are cholergenic?

1- Sweat glands 2- Piloerector muscles of the hairs 3- Some blood vessels

What are the two major subdivisions of the ANS?

1- Sympathetic 2- Parasympathetic

What happens to acetylcholine after it is released? (3 steps)

1- it persists and function in the tissue for a few seconds. 2- it splits into an acetate ion and choline by acetylcholinesterase in the local connective tissue. 3- The choline is transported back into the terminal nerve ending and is used again for form new acetylcholine.

The sympathetic nerve fibers in skeletal nerves control what 3 things?

1-Blood vessels 2-Sweat Glands 3-Piloerector muscles of the hairs

Organs of the sympathetic nervous system are stimulated in two ways?

1-Directly by sympathetic nerves 2-indirectly by the adrenal medullary hormones

What activates the ANS?

1-Spinal cord 2-Brain Stem 3-Hypothalamus Centers 4-The limbic cortex which can transmit signals to the lower centers 5-Visceral Reflexes

How is the physiological anatomy of the sympathetic nervous system configured?

1-Two paravertebral sympathetic chains of ganglia that are interconnected with the spinal nerves on the side of the vertebral column 2-Two prevertebral ganglia (celiac & hypogastric) 3-Nerves from the ganglia to different internal organs.

What are the 6 major actions of adrenergic alpha receptors?

1-Vasoconstrictor 2-Iris Dilation 3-Intestinal relaxation 4-Intestinal sphincter contraction 5-Pilomotor contraction 6-Bladder sphincter contraction

What are the 10 major actions of beta receptors?

1-Vasodialation 2-Cardioacceleration 3-Increased myocardial strength 4-Intestinal relaxation 5-Uterus relaxation 6-Bronchodilation 7-Calorigenesis 8-Glycogenolysis 9-Lipolysis 10-Bladder wall relaxation

What are the 8 "alarm" or "stress" responses of the sympathetic nervous system?

1. Increased arterial pressure 2. Increased blood flow to active muscles with decreased blood flow to organs not needed for rapid motor activity 3. Increased rates of cellular metabolism 4. Increased blood glucose concentration 5. Increased glycolysis in the liver and in muscle 6. Increased muscle strength 7. Increased mental activity 8. Increased rate of blood coagulation

How is norepinephrine removed from the terminal nerve endings (3 ways)?

1. reuptake into the adrenergic nerve endings by active transport (removes of 50 to 80%) 2. diffusion away from the nerve endings into the surrounding body fluids and then into the blood. (removes most of the remaining part) 3. destruction (small amounts) by tissue enzymes: monoamine oxidase (in nerve endings) and catechol-O-methyl transferase (in all tissues)

Full activation of the sympathetic and parasympathetic never fibers occurs when they discharge at ____ times per second?

10 to 20

How long will it be before cutting the sympathetic nerves to the blood vessels results in maximal vasodilation?

5-30 seconds

How many autonomic motor neurons does conduction from the spinal cord to any visceral effector require?

A tleast 2, a preganglionic and postganglionic neuron.

The sympathetic tone keeps the systemic arterioles constricted how much?

About 1/2 of their maximum diameter. Increasing the degree of sympathetic stimulation above normal constricts the arterioles and decreasing stimulation below normal dilate the arterioles.

What are the two major types of adrenergic receptors?

Alpha (1 and 2) and Beta (1 and 2)

Nicotinic receptors?

Are found in the autonomic ganglia at the synapses between the preganglionic and postganglionic neurons of both the sympathetic and parasympathetic systems.

Muscarinic receptors?

Are found on all effector cells that are stimulated by the postganglionic cholinergic neurons of either the parasympathetic nervous system or the sympathetic system.

The parasympathetic and sympathetic rates (tone) allows for increase or decrease in this activity?

Basal activities

What are varicosities?

Bulbous enlargements where transmitter vesicles of acetylcholine or norepinephrine are synthesized and stored.

What types of nerve fibers does the sympathetic nervous system use?

C fibers

Where do the parasympathetic fibers of the ANS originate?

CN-3,7,9, and 10 Sacral spinal nerves (S2-S4)

What does calcium do to varicosities?

Causes them to empty their contents and secrete transmitter substance

Almost all of the postganglionic neurons of the parasympathetic system are?

Cholergenic

The parasympathetic nerve fibers and almost all of the sympathetic fibers terminate on what?

Connective tissue located adjacent to the cells that are to be stimulated.

What are 6 major things that the ANS generally controls?

Entirely or partially: 1- Arterial Pressure 2- Gastrointestinal motility 3- Gastrointestinal secretion 4- Urinary bladder emptying 5- Sweating 6- Body Temperature

Alpha and beta receptors are excited equally by what?

Epinephrine

Sodium and/or calcium ion channel opening does what to the cell?

Excites

What are the two effects the receptor can have on an effector organ when transmitter substance binds?

Excites or inhibits the cell by: (1) causing a change in permeability to one or more ions or (2) activating or inactivating an enzyme attached to a receptor protein protruding into the interior of the cell

Transection immediately below the medulla causes the arterial pressure to do what?

Fall to less then one-half normal.

What are the segmental distributions of sympathetic nerve fibers to the head, neck, thorax, abdomen, and legs?

Head= T-1 Neck= T-2 Thorax= T-3,4,5,6 Abdomen=T-7,8,9,10,11 Legs= T-12, L-1,2

Transection of the brain stem above the midpontine level allows basal control of arterial pressure to continue as before but prevents its modulation by this structure?

Hypothalamus

Signals from what two CNS structures can affect the activities of almost all the brain stem autonomic functions?

Hypothalamus and Cerebrum

Where do the cell bodies of the preganglionic neurons lie in the sympathetics?

Inermediolateral horn

Potassium ions diffusing out of the cell does what to it?

Inhibits

Where do postganglionic fibers pass back from the sympathetic chain?

Into the spinal nerves through gray rami at all levels of the cord.

Sympathetic stimulation to the adrenal medulla causes what?

Large quantities of epinephrine and norepinephrine to be released into the blood (80% is epi and 20% is nor)

What are the two principle types of Acetylcholine receptors?

Muscarinic and nicotinic

Most of the postganglionic sympathetic neurons secrete what?

Norepinephrine (adrenergic)

Where does CN-9 go from the parasympathetic nervous system?

Parotid Gland

What are the two types of neurons that the sympathetic pathway going from the cord to the stimulated tissue involve?

Preganglionic and postganglionic

What is the general route that they sympathetic nerve fibers take to reach the medulla?

Preganglionic sympathetic nerve fibers pass, without synapsing from the intermedio-lateral horn cells through the sympathetic chains, then the splanchnic nerves, and finally end into the two adrenal medullae on modified neuronal cells that secrete epinephrine and norepinephrine into the blood stream.

Where does CN-3 go front he parasympathetic nervous system?

Pupillary sphincter and ciliary muscle of the eye.

Cholergenic fibers are ones that do what?

Secrete acetylcholine

Adrenergic fibers are ones that do what?

Secrete norepinephrine

What spinal cord segments does the sympathetic nerve fibers originate at?

T-1 to L-2

All preganglionic neurons, in the sympathetics and parasympathetics, share what common feature?

The are cholergenic (secrete ACh)

What do the sacral parasympathetic fibers supply?

The descending colon, rectum, urinary bladder, lower portions of the ureters and the external genitalia to cause erection.

Where does CN-7 go from the parasympathetic nervous system?

The lacrimal, nasal, and submandibular glands.

Where do the nerve fibers of the sympathetic nervous system need to pass before they can go to tissues and organs that are stimulated by the nerves?

The sympathetic chain

Where are the parasympathetic post ganglionic neurons located?

The visceral organ

What is the importance of the autonomic centers in the brain stem?

They act as relay stations for control of activities initiated at higher levels of the brain, especially the hypothalamus.

The preganglionic sympathetic fibers leave the spinal nerve and pass through what to get to the ganglia of the sympathetic chain?

White ramus

Norepinephrine mainly excites this type of receptor, although it can excite this other type to a lesser extent?

alpha, beta (respectively)

Where are 75% of all parasympathetic nerve fibers? What do these fibers supply?

vagus nerves (CN X): it supply the heart, lungs,esophagus, stomach, entire small intestine, proximal half of the colon, liver, gallbladder, pancreas, Kidneys and upper portions of the ureters.