Physiology Lo: Autonomic Nervous System

Front 1

List characteristics of the somatic and autonomic nervous system

Back 1

Somatic: involves 1 neuron, innervates skeletal muscle, ACh is the NT to effector organ, nicotinic receptors on effector, excitation is effector organ response.

Autonomic: involves 2 neurons, innervates smooth & cardiac muscle, glands, GI and other neurons, ACh and NE is the NT to effector organ, muscarinic and adrenergic receptors, effector organ response can be excitatory or inhibitory.

Front 2

On a summary diagram of the autonomic and somatic nervous systems, label all of the parts of the diagram. Include the division of the nervous system, the neurotransmitters, and the receptors stimulated by the neurotransmitters

Back 2

N/A

Front 3

Describe the anatomy, neurotransmitters, and receptors that are characteristic of the sympathetic nervous system. Identify the proportion of norepinephrine and epinephrine that is released from the adrenal medulla.

Back 3

In the thoracolumbar division:

--Preganglionic sympathetic neurons are located in the IML, are myelinated, and secrete ACh. [neurons are short]

--Sympathetic ganglia: located in the sympathetic chain ganglia that lie close to the spinal cord and more distant ganglia (superior and inferior mesenteric ganglia and celiac ganglion)

--Postganglionic sympathetic neurons have their cell bodies located in the sympathetic ganglia. The axons are unmyelinated, and extend to and innervate the effector organs. These neurons primarily secrete norepinephrine as their NT.

--Chromaffin cells are located in the adrenal medulla and they receive innervation from preganglionic sympathetic neurons. Chromaffin cells secrete epinephrine (Epi) and NE in proportions of 80% and 20%.

Front 4

Describe the anatomy, neurotransmitters, and receptors that are characteristic of the parasympathetic nervous system.

Back 4

In the craniosacral division:

--Preganglionic parasympathetic neuron's cell body's are located in either the brain or sacral portion of the spinal cord. These neurons emerge from the CNS as myelinated axons, extend to the parasympathetic ganglia, and release ACh.

--Parasympathetic ganglia are located either directly on the effector organ or in close proximity to the effector organ.

--Postganglionic parasympathetic neurons are unmyelinated and usually located on the effector organ. Postganglionic parasympathetic neurons release ACh as the NT.

Front 5

List the classes of cholinergic receptors, and list the drugs that block each of these classes of receptors.

Back 5

--Nicotinic receptors: stimulated by low doses of nicotine and inhibited by high doses of nicotine. ACh ALWAYS stimulates nicotinic receptors. ACh stimulates nicotinic receptors at the neuromuscular junction (somatic), and at autonomic ganglia which excites the sympathetic and parasympathetic postganglionic neurons.

Curare is a nicotinic antagonist at the neuromuscular junction. And trimethaphan is a nicotinic antagonist at the autonomic ganglia.

--Muscarinic receptors: stimulated by ACh. Excitation of muscarinic receptors can inhibit or excite the effector organ, depending on the specific organ. Atropine is a muscarinic receptor antagonist.

Front 6

List the classes of adrenergic receptors. List examples of drugs that stimulate and block the alpha and beta receptors.

Back 6

--Norepinephrine is the primary NT for sympathetic postganglionic neurons.

--Epinephrine is released from the adrenal medulla but NOT from sympathetic postganglionic nerves.

--Phenylephrine is an alpha receptor agonist

--Phentolamine is an alpha receptor antagonist

--Isoproterenol is a beta receptor agonist

--Propranolol is a beta receptor antagonist

Front 7

Describe the general rules that apply to the actions of adrenergic receptors.

Back 7

Adrenergic receptors are found on effector organs or tissues, and mediate the effects of the sympathetic nervous system or the actions of circulating epinephrine.

Front 8

Define "functional synergism," and provide an example.

Back 8

This occurs in dual innervated organs when the sympathetic and parasympathetic systems work together to produce an effect. Ex: control of heart rate.

Front 9

Define "tonic activity." Explain the significance of tonic activity in the autonomic nervous system.

Back 9

A fundamental characteristic of the autonomic nervous system is the presence of "tonic" or basal resting nerve activity to many organs. This concept refers to a continuous resting level of autonomic neural activity to an organ or tissue. This means that there is almost always some autonomic nerve activity from BOTH the SNS and PNS under all types of conditions.

Front 10

Describe the effects and receptors used by the two divisions of the autonomic nervous system for the following organ systems: eyes, cardiovascular system, lungs, gastrointestinal tract, bladder muscle, reproductive tract in the male, and sweat glands.

Back 10

--Eyes: sympathetic: a1, contract radial muscle (mydriasis). parasympathetic: muscarinic, contract circular muscle (miosis).

--Cardiovascular: Heart: sympathetic: B1, increases HR, conduction velocity, contractility. parasympathetic: muscarinic, decreases HR, conduction velocity and contractility. Blood vessels: sympathetic: a1 &/or 2 constrict coronary, skin & skeletal muscle arterioles, abdominal viscera, and veins. B2 dilates coronary & skeletal muscle arterioles, and veins.

--Lungs: sympathetic: bronchial muscle: B2 dilates. Parasympathetic: muscarinic constricts.

--GI: Salivary glands: sympathetic: a1 increases watery secretion, B increases enzyme secretion. Parasympathetic: muscarinic increases watery secretion. Motility: sympathetic: a1, a2, B2 decrease motility. Parasympathetic: muscarinic increases motility.

--Urinary system: Kidneys: sympathetic: a1, B1 increase renin secretion. Bladder wall: sympathetic: B2, B3 relax. parasympathetic: muscarinic contracts. Bladder sphincter: sympathetic: a1 contracts. parasympathetic: muscarinic relaxes.

--Male reproductive tract: sympathetic: a1, ejaculation. parasympathetic: muscarinic, erection.

--Sweat glands: Eccrine (thermoregulation): sympathetic: muscarinic, secretion. Apocrine (axillae, pubic region): sympathetic: a1, secretion.

Front 11

List in order the sequence of neural events that occurs in the baroreflex for either a decrease or an increase in blood pressure.

Back 11

1. Increase in blood pressure (BP)

2. Increase activity in baroreceptors

3. Increase activity in nucleus of the solitary tract (NTS)

4. Increase activity in caudal ventrolateral medulla (CVLM)

5. Decrease activity in rostral ventrolateral medulla (RVLM)

6. Decrease sympathetic outflow

7. Lower BP

4. Increase activity in nucleus ambiguous (NA)

5. Increase vagal activity to the heart (parasympathetic)

6. Decrease in heart rate (HR)

7. Lower BP

Front 12

Describe five diseases that can result from autonomic nervous system dysfunction.

Back 12

--Hypertension: estimates of the number of hypertensive individuals range between 20-60 million people in the US with 1/3 of these undetected. Hypertension contributes to about 200,000 deaths per year. While there are many causes for hypertension, one contributory mechanism is an increase in the tonic or basal level of sympathetic tone to the heart and/or blood vessels.

Pheochromocytoma: tumor of the chromatin cells in the adrenal gland; only accounts for 0.1% of hypertensive patients.

--Postural (orthostatic) hypotension: this is defined as a drop in the arterial pressure of 30mmHg or more upon standing, and is a problem common to many different physiological problems. Dizziness if felt upon standing due to an inadequate perfusion of the CNS. Orthostatic hypotension is due to inadequate reflex control of blood pressure.

--Horner's syndrome: results from loss of sympathetic innervation to the head; the damage that produces this can occur from hypothalamus to spinal cord and back up the head. Three classic signs of Horner's: 1. Miosis occurs due to unopposed parasympathetic innervation to the iris. 2. Ptosis (drooping of the eyelid) occurs due to loss of sympathetic innervation of the legator palpebrae muscle in the eyelid, which prevents this muscle from assisting in raising the eyelid. 3. Anhydrosis (loss of sweating) is due to loss of sympathetic innervation of sweat glands, and occurs in the head and neck.

--Autonomic diabetic neuropathy: can occur in diabetics due to degeneration of small nerve fibers. This cause is not certain, but may be a problem of adequate blood perfusion and/or metabolic problems in the neurons. A wide variety of problems can result, such as impaired swallowing, delayed gastric emptying, diarrhea, orthostatic hypotension, bladder dysfunction, and erectile dysfunction.

--Autonomic dysreflexia (sympathetic hyperreflexia): some patients with a spinal cord lesion at T6 or above may develop this condition. The major characteristic of this condition is extremely high blood pressure. Multiple stimuli can evoke the hypertension. The most common stimuli are bladder dissension or dissension of the colon and/or rectum, but other stimuli may evoke autonomic dysreflexia. Presumably the plasticity that occurs in the spinal cord after a spinal cord injury allows sensory input to produce an abnormally large sympathetic outflow.