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Innervates smooth muscle, cardiac muscle and glands Helps to maintain homeostasis Also called the involuntary or visceral motor system THE AUTONOMIC NERVOUS.

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Presentation on theme: "Innervates smooth muscle, cardiac muscle and glands Helps to maintain homeostasis Also called the involuntary or visceral motor system THE AUTONOMIC NERVOUS."— Presentation transcript:

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2 Innervates smooth muscle, cardiac muscle and glands Helps to maintain homeostasis Also called the involuntary or visceral motor system THE AUTONOMIC NERVOUS SYSTEM

3 Regulation –By brainstem, spinal cord, hypothalamus and parts of the cerebrum THE AUTONOMIC NERVOUS SYSTEM

4 The motor units of the ANS consist of two neurons: –Preganglionic Neuron Cell body is in the CNS Synapses with another neuron before reaching the effector The synapse occurs in an autonomic ganglion outside the CNS (The somatic motor unit consists of one neuron with its cell body in the CNS and its axon extending to the effector) –Postganglionic Neuron Extends from the autonomic ganglion in the PNS to the effector AUTONOMIC GANGLIA AND CIRCUITS

5 AUTONOMIC GANGLIA AND CIRCIUTS CNSPNS Effector

6 THE AUTONOMIC NERVOUS SYSTEM

7 Fight or flight system activated in emergency situations Effects: –Increases heart rate –Dilates bronchial tubes and pupils –Constricts blood vessels –Stimulates secretion of epinephrine and norepinephrine from the adrenal gland –Stimulates sweat glands –Inhibits digestion –Aids in ejaculation in males DIVISIONS OF THE ANS: The Sympathetic System (see table 14.4)

8 THE SYMPATHETIC SYSTEM Neurons –Emerge through the ventral roots of spinal nerves T 1 through L 2 (thoracolumabar outflow)

9 THE SYMPATHETIC SYSTEM Preganglionic Sympathetic Neurons –Preganglionic bodies are in the lateral horns of the spinal cord at the T 1 through L 2 levels –Preganglionic sympathetic axons are short –Preganglionic fibers pass through the ventral root into the white rami communicantes

10 THE SYMPATHETIC SYSTEM Preganglionic Sympathetic Neurons –Preganglionic sympathetic neurons synapse with a postganglionic neuron in the paravertebral chain ganglia Paravertebral chain ganglia run lateral to the spinal cord on both sides There are 22 to 23 pair of paravertebral ganglia on both sides of the vertebral column

11 THE SYMPATHETIC SYSTEM Preganglionic Sympathetic Neurons –Preganglionic fibers may ascend or descend within the chain to synapse within a ganglion at a different level –Some sympathetic preganglionic fibers pass through the chain ganglion without synapsing These are called sympathetic splanchnic nerves

12 THE SYMPATHETIC SYSTEM Preganglionic Sympathetic Neurons –Sympathetic splanchnic nerves synapse in ganglia anterior to the vertebral column (near the aorta) –These ganglia are called prevertebral or collateral ganglia –Sympathetic splanchnics innervate smooth muscles of the abdominal and pelvic viscera and their blood vessels

13 THE SYMPATHETIC SYSTEM Postganglionic Sympathetic Neurons –Post ganglionic sympathetic axons are long –Post ganglionic sympathetic neurons exit the paravertebral ganglia via the gray rami communicantes (unmyelinated) and re- enter the spinal nerve –From here they continue on to the effector (viscera, blood vessels, sweat glands)

14 All sympathetic preganglionic neurons release acetylcholine as a neurotransmitter (cholinergic) Sympathetic postganglionic neurons release norepinephrine (adrenergic) with the exception of neurons to blood vessels and sweat glands (cholinergic) THE SYMPATHETIC SYSTEM

15 Adrenal Medulla –Preganglionic sympathetic neurons innervate the adrenal medulla –Cause release of epinephrine and norepinephrine into the bloodstream –Has the same effect as the sympathetic system only lasts 5 to 10 times longer THE SYMPATHETIC SYSTEM

16 Norepinephrine & Epinephrine –Norepinephrine and epinephrine both have similar effects on the body –Epinephrine has a greater effect on cardiac stimulation, raising B.P. and increasing metabolic rate –Both are secreted by the adrenal medulla in response to sympathetic stimulation –Same effect as stimulating organs via sympathetic nerves only lasts 5 to 10 times longer THE SYMPATHETIC SYSTEM

17 Effects: –Constricts the pupils and bronchi –Restores gland and digestive system activity –Slows heartrate THE PARASYMPATHETIC SYSTEM

18 Neurons: –Emerge with the cranial nerves (III, VII, IX and X) –Some emerge with the sacral spinal nerves –Craniosacral outflow C.N. III C.N. VII C.N. IX C.N. X uNeuron cell bodies for the fibers traveling with cranial nerves are in the brainstem uCell bodies for the fibers traveling with the sacral spinal nerves are in the lateral gray horns of spinal levels S 2 -S 4

19 THE PARASYMPATHETIC SYSTEM Preganglionic Parasympathetic Neurons –Preganglionic neurons are long –Preganglionic neurons travel from the CNS almost all the way to the effector before synapsing with a postganglionic neuron

20 THE PARASYMPATHETIC SYSTEM Postganglionic Parasympathetic Neurons –Postganglionic parasympathetic neurons are short –Postganglionic neurons synapse with preganglionics on or near the effector organ in terminal ganglia (collectively called intramural ganglia) –Postganglionic neurons travel from the terminal ganglia to the effector cells

21 THE PARASYMPATHETIC SYSTEM Cranial OutflowCranial Outflow –With C.N. III, VII, IX and X –Preganglionic fibers travel with each cranial nerve –Postganglionic fibers for C.N. III, VII and IX travel with C.N. X for distribution to the face C.N. III C.N. VII C.N. IX C.N. X uVagus nerve accounts for 90% of all preganglionic parasympathetic fibers in the body uParasympathetic fibers from the Vagus nerve supply almost every thoracic and abdominal organ

22 THE PARASYMPATHETIC SYSTEM Sacral Outflow –Axons run from the spinal cord with the ventral rami of S 2 -S 4 –Fibers branch into pelvic splanchnic nerves –Most fibers go on to synapse in intramural ganglia near the effector organ –Pelvic splanchnics innervate the distal large intestine, urinary bladder, ureters and reproductive organs

23 Cholinergic Receptors –Activated by acetylcholine (Ach) –Two types: Muscarinic –Found on all effector cells stimulated by postganglionic cholinergic fibers (all parasympathetic target organs and some sympathetic) Nicotinic –Found on motor end plates of skeletal muscle –Found on all postganglionic neurons (sympathetic and parasympathetic) –Found on the hormone producing cells of the adrenal medulla ANS RECEPTORS

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25 Adrenergic Receptors –Activated by epinephrine and norepinephrine –Two types: Alpha (  ) –Epinephrine has a greater effect on these than norepinephrine –Found on all sympathetic target organs except the heart –Usually stimulatory when NE or Epinephrine binds to them Beta (  ) –Found in the heart, adipose tissue and most sympathetic organs –Usually inhibitory when either hormone binds to them (except in the heart) –Cause dilation of blood vessels ANS RECEPTORS

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27 VISCERAL REFLEXES Visceral Reflex Arcs

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