Upload
muhammad-saim
View
7.937
Download
9
Tags:
Embed Size (px)
DESCRIPTION
Citation preview
FUNCTIONAL ASPECTS OF THE AUTONOMIC NERVOUS SYSTEM
3
AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system is the subdivision of the peripheral nervous system that regulates body activities that are generally not under conscious control
Autonomic nervous system innervate smooth muscle (eg, blood vessels, gut
wall, urinary bladder) cardiac muscle glands (eg, sweat glands, salivary glands)
DIVISION OF ANS
Parasysmpathetic: routine maintenance
“rest &digest”
Sympathetic: mobilization & increased metabolism
“fight, flight or fright”
4
5
WHERE THEY COME FROM
Parasympathetic:craniosacral
Sympathetic:thoracolumbar
PARASYMPATHETIC SYSTEM
6
7
PARASYMPATHETIC OUTFLOW
Cranial outflow III - pupils constrict VII - tears, nasal mucus, saliva IX – parotid salivary gland X (Vagus n) – visceral organs of thorax & abdomen:
Stimulates digestive glands Increases motility of smooth muscle of digestive tract Decreases heart rate Causes bronchial constriction
Sacral outflow (S2-4): form pelvic splanchnic nerves Supply 2nd half of large intestine Supply all the pelvic (genitourinary) organs
SYMPATHETIC SYSTEM
8
9
SYMPATHETIC OUTFLOW“fight, flight or fright”
Also called thoracolumbar system: all its neurons are in lateral horn of gray matter from T1-L2
Lead to every part of the body (unlike parasymp.) Easy to remember that when nervous, you sweat; when
afraid, hair stands on end; when excited blood pressure rises (vasoconstriction): these sympathetic only
Also causes: dry mouth, pupils to dilate, increased heart & respiratory rates to increase O2 to skeletal muscles, and liver to release glucose
10
PRE AND POST GANGLION NEURON
Somatic division: Cell bodies of motor neurons reside in CNS (brain or
spinal cord) Their axons (sheathed in spinal nerves) extend all the
way to their skeletal muscles Autonomic system: chains of two motor neurons
1st = preganglionic neuron (in brain or cord) 2nd = gangionic neuron (cell body in ganglion outside
CNS)
(see next diagram)
11
PRE AND POSTGANGLION FIBER
Axon of 1st (preganglionic) neuron leaves CNS to synapse with the 2nd (ganglionic) neuron
Axon of 2nd (postganglionic) neuron extends to the organ it serves
Note: the autonomic ganglion is motor
12
13
Figure 8-2
SYMPATHETIC AND PARA SYMPATHETIC GANGLIA
Sympathetic ganglia Many lie close to spinal cord(paravertebral) Others lie approximately midway between
spinal cord and effector organ(prevrtebral or collateral)
Parasympathetic ganglia Lie close to or within the walls of effector organ
Figure 8-2
IMPORTANT NEUROTRANSMITTERS
Acetylcholine =Cholinergic Fibers that release acetylcholine are
known as cholinergic fibers All preganglionic neurons of the autonomic
division and all postganglionic neurons of the parasympathetic division are cholinergic
17
Norepinephrine = Adrenergic Neurotransmitter between the sympathetic
postganglionic fiber and the effector cell Fibers that release norepinephrine are
adrenergic fibers
Most postganglionic neurons of the sympathetic division are adrenergic Few are cholinergic(sweat gland,some blood
vessels in skeletal muscle)
CHOLINERGIC RECEPTOR
Nicotinic receptor Nicotinic receptors are found on the
postganglionic cell bodies in all autonomic ganglia.
Response to acetylcholine released from both sympathetic and parasympathetic
18
Muscuranic receptor found on cell membranes of effectors
organ (smooth muscle, cardiac muscle, and glands)
they bind with acetylcholine released from parasympathetic postganglionic nerve fiber
19
ADRENERGIC RECEPTOR
Alpha receptors are located at sympathetic neuroeffector junctions of many organs.
In general, alpha receptors mediate excitation or increased activity of the effector cells.
alpha receptor have greater affinity for norepinephrine
20
TYPES OF -ADRENERGIC RECEPTOR
-adrenergic receptors are adrenergic receptors that respond to norepinephrine
They are subdivided into two types:
1, found in smooth muscle, heart, and liver, with effects including vasoconstriction, intestinal relaxation, uterine contraction and pupillary dilation,
2, found in platelets, vascular smooth muscle, nerve termini, and pancreatic islets, with effects including platelet aggregation, vasoconstriction, and inhibition of norepinephrine release and of insulin secretion.
Beta receptors are also located postsynaptically at sympathetic neuroeffector junctions of many organs.
beta receptors mediate relaxation or decreased activity of the effector cells.
Heart muscle is an important exception to this rule. Activation of beta adrenoceptors in heart increases the automaticity and contractility of all parts of the heart.
-RECEPTOR TYPES -adrenergic receptors respond particularly to epinephrine
and nor epinephrine
There are three known types of beta receptor, designated β1, β2 and β3.
β1-Adrenergic receptors are located mainly in the heart. Sensitive to both EN and NOR EN
β2-Adrenergic receptors are located mainly in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle
sensitive to EN only.
β3-receptors are located in fat cells.
24
25
ADRENAL GLAND IS EXCEPTION
On top of kidneys
Adrenal medulla (inside part) is a major organ of the sympathetic nervous system
26
Adrenal gland is exception
Synapse in gland
Can cause body-wide release of epinephrine and norepinephrine
27
28
29
30
31
32
SYMPATHETIC PARASYMPATHETIC TONE
DUAL INNERVATION MASS DISCHARGE(ALARM OR STRESS
RESPONSE) LOCAL RESPONSE SOME EXCEPTIONS: BLOOD VESSELS
SWEAT GLAND, SALIVARY GLAND33
VISCERAL REFLEXES
These are the simplest functions of the ANS. Each visceral reflex arc consists of a receptor, a sensory
neuron, an interneuron, and two visceral motor neurons. All visceral reflexes are polysynaptic. PS reflexes include : gastric and intestinal reflexes,
defecation, urination, direct light reflexes, swallowing reflex, coughing reflex, baroreceptor reflex and sexual arousal.
S reflexes: cardioaccelaratory reflex, vasomotor reflex, pupillary reflex and ejaculation (in males).
35
VISCERAL REFLEX ARCS
*e.g. “enteric” nervous system: 3 neuron reflex arcs entirely within the wall of the gut
36
Central control of the Autonomic NS
Amygdala: main limbic region for emotions
Hypothalamus: main integration center
Reticular formation: most direct influence over autonomic function