CVPR 03-28-14 09-10am Autonomic Nervous System Physiology - Felsen Flashcards
1
Q
Role of the autonomic NS
A
To maintain homeostasis in the internal environment amid changing external conditions, via widespread & complementary actions in organs systems in response to sensory stimuli
2
Q
How the ANS works
A
It regulates the physiological systems over which we have only minimal conscious control, such as the cardiovascular, GI, and respiratory systems….. Changes in autonomic control of these systems elicit the responses we associate with stressful stimuli and other emotions.
3
Q
ANS vs. Somatic motor system
A
ANS – involuntary, diffuse projections, slow action, innervates smooth/cardiac muscle & gland cells, disynaptic (pre/postganglionic neurons)…..SMS – voluntary, specific projections, rapid action, innervates skeletal muscle, monosynaptic
4
Q
Autonomic NS – how it works
A
Unlike the somatic (motor) NS, the Autonomic NS is characterized by a 2-neuron link between CNS & peripheral target organ….Preganglionic neurons are located in the CNS (brainstem or spinal cord) and connect to Postganglionic neurons located in autonomic ganglia outside the CNS —> Postganglionic neurons project to the target organ where they innervate smooth muscle, cardiac muscle, or glands
5
Q
Myelination w/in the 2-Neuron System of the ANS
A
Transmission over PREganglionic fibers is relatively fast, b/c they are composed of myelinated fibers….. POST ganglionic fibers are unmyelinated.
6
Q
Autonomic nervous system - Division
A
The ANS consists of the Sympathetic NS & the Parasympathetic NS, as well as the Enteric semi-autonomous control of digestion
7
Q
Ganglion vs. Nucleus
A
Ganglion = cluster of cell bodies in peripheral NS; Nucleus = cluster of cell bodies in CNS
8
Q
Sympathetic vs. Parasympathetic – origin of preganglionic neurons
A
SYMP: thoracic & lumbar spinal cord….. PARA: brainstem & sacral spinal cord
9
Q
Sympathetic vs. Parasympathetic –location of ganglia
A
SYMP: near spinal cord…..PARA: near target organs
10
Q
Sympathetic vs. Parasympathetic – ratio of pre- to post-ganglionic neurons
A
SYMP: 1:10 pre to post…. PARA: 1:3
11
Q
Sympathetic vs. Parasympathetic –Neurotransmitters of preganglionic neurons
A
BOTH: Acetylcholine (ACh)
12
Q
Sympathetic vs. Parasympathetic – Postanglionic
A
SYMP: Norepinephrine (NE) and epinephrine…. PARA: ACh
13
Q
Role of the Sympathetic nervous system
A
Initiates responses to emergency or stressful situations - “fight and flight” responses
14
Q
Organization of the Sympathetic NS – Location of Preganglionic neurons
A
Preganglionic neurons are located in the intermediolateral column of the thoracic & upper lumbar segments of the spinal cord, as well as in splanchnic nerves arising from the lower 7 thoracic spinal level
15
Q
Pathway of Preganglionic Sympathetic neurons located in the thoracic/upper lumbar spinal cord
A
Preganglionic Sympathetic axons exit the spinal cord in the ventral roots of corresponding spinal nerves –> Pass through white ramus communicans (myelinated) —> Enter sympathetic trunk and branch to innervate postganglionic neurons in multiple levels of the spinal trunk
16
Q
Pathway of Preganglionic Sympathetic neurons located in splanchnic nerves
A
Preganglionic parasympathetic axons in splanchnic nerves pass through the spinal trunk to innervate postganglionic sympathetic neurons located in the celiac & mesenteric ganglia
17
Q
Neurotransmitter relased by PREganglionic vs POSTganglionic neurons of the Sympathetic NS
A
Acetylcholine is the neurotransmitter released by preganglionic sympathetic neurons; Postganglionic sympathetic neurons release norepinephrine as their neurotransmitter.
18
Q
Organization of the Sympathetic NS –Location of Postganglionic neurons
A
Located in the ganglia of the sympathetic trunk (paravertebral chain ganglia) and in the celiac & mesenteric ganglia (those involved in GI tract regulation
19
Q
Pathway of Sympathetic Postganglionic neurons located in the paravertebral chain ganglia
A
From the ganglia of the sympathetic trunk (paravertebral chain ganglia). The sympathetic postganglionic axons exit the spinal trunk through the gray rami communicans (unmyelinated) —> travel in spinal nerves to reach sweat glands, peripheral blood vessels, hair follicles, etc
20
Q
Pathway of Sympathetic Postganglionic neurons located in the celiac & mesenteric ganglia
A
Axons from the postganglionic sympathetic neurons in the celiac & mesenteric ganglia form the perivascular plexuses innervating the abdominal viscera —> regulate GI tract
21
Q
Adrenal medulla
A
Specialized component of the sympathetic nervous system; functions as neuroendocrine gland; its postganglionic cells secrete epi (80-90%) & norepi (10-20%), both of which bind to adrenergic receptors, into the blood stream….Thus, rather than acting as neurotransmitters, these agents become hormones to regulate activity of distant target tissues (sympathomimetic but more widespread & slower than normal sympathetic neurons)
22
Q
Innervations of specialized postganglionic cells of the Adrenal medulla
A
Innervated by preganglionic sympathetic neurons located in thoracic levels 6-9 of the spinal cord.
23
Q
Sympathetic NS – what it controls
A
Vasodilation & vasoconstriction are controlled primarily by the SNS….. Increased sympathetic output causes vasoconstriction (as well as increased HR & force of contraction), while decreased sympathetic output causes vasodilation….At rest, sympathetic output maintains the vasculature in an intermediate state between constriction & dilation
24
Q
Role of the Parasympathetic nervous system
A
Involved in conservation & replenishing of resources; Classically associated w/ “rest and digest” responses; The actions of the PNS generally oppose those of the sympathetic NS.
25
Organization of the Parasympathetic NS –Location of Preganglionic neurons
Preganglionic neurons of the PNS are located in brainstem nuclei & in the sacral spinal cord ; characterized by long axons
26
Pathway of Parasympathetic Preganlionic neurons located in the brainstem
The parasympathetic preganglionic fibers located in the brainstem exit in cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus) ---> innervate postganglionic neurons located in ganglia near or in the effector organ.
27
Pathway of Parasympathetic Preganglionic neurons located sacrally
The parasympathetic preganglionic axons exit the sacral portion of the parasympathetic system and travel in the splanchnic nerves to innervate ganglia associated with the colon, rectum, urinary bladder, and genital organs ---> functions to control "emptying" (e.g. urination, defecation, and erection)
28
Organization of the Parasympathetic NS –Location of Postganglionic neurons
Located in/near effector organ, and thus characterized by short axons.
29
Neurotransmitters relased by PREganglionic vs POSTganglionic neurons of the Parasympathetic NS
Both pre- & post-ganglionic parasympathetic neurons use acetylcholine as a neurotransmitter
30
Increased parasympathetic output results in….
Decreased HF & force of contraction; While parasympathetic output may result in some small amount of vasodilation, most vasodilation is controlled by decreased sympathetic output.
31
Neurotransmitters of ANS preganglionic neurons
Usually, preganglionic neurons of sympathetic & parasympathetic system release NT acetylcholine (ACh) ---> ACh acts on nicotinic cholinergic receptors on postganglionic neurons ---> depolarization & firing of postganglionic neuron ---> APs arrive at nerve terminal of postganglionic neuron then cause release of synaptic vesicles containing norepinephrine or ACh via exocytosis…… Co-localized agents (e.g. ATP, peptides) also participate.
32
Neurotransmitters of Sympathetic vs. Parasympathetic Postganglionic neurons
Sympathetic Postanglionic = Norepinephrine (NE); Parasympathetic Postganglionic = ACh
33
Receptor subtypes for ACh: Two types
Two types of cholinergic receptors to which ACh binds & elicits a cholinergic response.: 1. nicotinic (stimulated by nicotine) AND 2. muscarinic (stimulated by muscarine) receptors……. Cellular mechanisms by which ACh produces its effects are very different for nicotinic & muscarinic receptors.
34
Location of ACh receptors - Nicotinic vs. Muscarinic
Nicotinic receptors are mainly present in the cell body of postganglionic neurons of the autonomic ganglia; Muscarinic receptors are present on effector cells of cardiac muscle, smooth muscle, & glands.
35
Nicotinic receptor – what it is & what ACh does to it
A ligand-gated, non-selective cation channel….. When ACh binds it, the ion channel opens & allows rapid movement of Na+ & K+ across the membrane---> depolarization & excitation
36
Muscarinic receptor – what it is & what ACh does to it
Located in cell membrane, linked to a GTP-binding (G) protein….. When ACh binds the extracellular site of the muscarinic receptor protein, a conformational change occurs w/in it ---> "activation" of G protein coupled to the receptor ---> G protein then either stimulates or inhibits other intracellular effectors such as enzymes or ion channels ---> physiological response.
37
Five subtypes of muscarinic receptors
M1-M5; Different muscarinic receptors are coupled to different effectors within a cell….. Thus, simple ACh can produce various physiological responses in different cell types, depending on which muscarinic receptor subtype is activated
38
Muscarinic receptors & hyperpolarization
In Atrial cells, ACh released from vagus nerve binds to muscarinic receptor ---> activates G protein, which opens K channels ---> hyperpolarization & slowing down of HR
39
Muscarinic receptors & depolarization
In some cells, activation of muscarinic receptors causes a different type of K+ channel (than is opened in Atrial cells by ACh binding to muscarinic receptors) to close ---> sustained depolarization of the neuron.
40
Receptors of ACh vs. NE
ACh: nicotinic vs. muscarinic….. NE: alpha- & beta-adrenergic
41
Receptor subtypes for Norepinephrine vs. Epinephrine
Like w/ cholinergic receptors, there are multiple receptor subtypes for NE (NT for adrenergic system)….. Adrenergic receptors consist of alpha (α) and beta (β) receptors, subdivided into α1, α2, β1, and β2….NE only activates α1, α2, and β1 receptors….. Epinephrine (released from adrenal medulla into bloodstream) activates all 4 subtypes.
42
Activity of the autonomic nervous system is regulated by…
…information coming from visceral afferents and from higher CNS centers.
43
Inputs to preganglionic neurons…
Visceral sensory input <-- hypothalamus (in forebrain)
44
Autonomic reflexes – where they are organized
Autonomic reflexes are organized in the spinal cord & brainstem
45
Organization of the Baroreflex (an autonomic reflex)
Baroreflex is organized in the medulla w/afferent info transmitted in glossopharyngeal nerve (cranial nerve IX) from the carotid sinus to the dorsal vagal complex of the medulla, which in turn contains neurons projecting to regions of the medulla that regulate sympathetic & parasympathetic activity.
46
Location of Organization of the respiratory reflexes (autonomic reflexes)
Organized in the pons
47
Location of organization of the pupillary reflexes (autonomic reflexes)
Organized in the midbrain; allow visual system to rxt to different light levels (dilations/constriction); unconscious, involuntary
48
Cardiovascular regulation by nervous system
Sympathetic/parasympathetic control of HR & BP; Humoral response (via bloodsream); Baroreceptor reflex
49
Norepinephrine & Sympathetic regulation of the CV system
Sympathetic stimulation --> increase NE ---> increased BP (increase HR & contractile force; vasoconstriction)
50
Acetylcholine & Parasympathetic regulation of the CV system
Parasympathetic stimulation ---> increase ACh ---> decreased BP (decreased BP & contractile force)
51
Baroreceptor reflex
Low BP ---> relative increase in sympathetic output (send info to medulla)….. High BP ---> relative increase in parasympathetic output
52
Hypothalamus & the ANS
"Head ganglion" of the autonomic nervous system, b/c it integrates info from several brain regions in order to convey the needs of the organism to the preganglionic autonomic centers in the brainstem & spinal cord….. It also coordinates humoral (i.e., hormonal) response via pituitary & somatic motor response….. It also coordinates the visceromotor response via the ANS, in order to maintain homeostasis. [EX: Hypothalamus stimulates the release of vasopressin from the posterior pituitary into the bloodstream, resulting in vasoconstriction.]
53
Humoral regulation via Hypothalamus
Hypothalamus controls release of hormones via pituitary (Posterior pituitary (part of the brain) & Anterior pituitary (a gland))
54
Vasopressin (ADH)
Low BP detected by subfornical organ ---> release of vasopressin from posterior pituitary ---> causes vasoconstriction & increases water retention via kidneys ---> increased BP
55
Renin & angiotensin
Low BP ---> renin released from kidneys ---> angiotensinogen to angiotensin (I --> II) vasoconstriction, increases water retention via kidneys, activates neurons in subfornical organ ---> increased BP
56
Clinical significance of different receptor types in different tissues and differential activation by norepi & epi:
Drugs are available that selectively activate or inhibit the subtypes of adrenergic receptors (EX: To counteract bronchoconstriction in asthma or severe anaphylactic rxns, epi or a more selective β2 agonist is administered to initiate bronchodilation; Beta-blockers are used to treat HTN & CAD)
57
Atropine
Sympathomimetic drug = muscarinic (M2) antagonist in heart ---> increases HR
58
Propranolol
Parasympathomimetic drug = Beta-adrenergic (B1&2) antagonist in heart ---> decreases HR
59
Adrenergic receptor α1 agonist & its effect of agonist
Sympathomimetics….EX: Phenylephrine….Effect: Vasoconstriction in skin
60
Adrenergic receptor α2 agonist & its effect of agonist
Sympathomimetics….EX: Clonidine….Effect: Presynaptic inhibition of Norepi release; Some vasoconstriction
61
Adrenergic receptor β1 agonist & its effect of agonist
Sympathomimetics….EX: Dobutamine….Effect: Increased HR
62
Adrenergic receptor β2 agonist & its effect of agonist
Sympathomimetics….EX: Albuterol….Effect: Increased HR, Vasodilation in skeletal muscle
63
Adrenergic receptor α1 antagonist & its effect of antagonist
Parasympathomimietic….EX: Doxazosin….Effect: Blocks receptor agonist effects of vasoconstricion in the skin
64
Adrenergic receptor α2 antagonist & its effect of antagonist
Parasympathomimietic….EX: Trazodone….Effect: Blocks receptor agonist effects of presynaptic inhibition of NE release & some vasoconstriction
65
Adrenergic receptor β1 antagonist & its effect of antagonist
Parasympathomimietic….EX: Atenolol….. Effects: Block receptor agonist effects of increased HR
66
Adrenergic receptor β2 antagonist & its effect of antagonist
Parasympathomimietic….EX: Butaxamine….. Effects: Blocks receptor agonist effects of increased HR & vasodilation in skeletal muscle
67
Agonists of cholinergic receptors – activity
Parasympathomimetic
68
Antagonists of cholinergic receptors – activity
Sympathomimetic
69
How the ANS works
It regulates the physiological systems over which we have only minimal conscious control, such as the cardiovascular, GI, and respiratory systems….. Changes in autonomic control of these systems elicit the responses we associate with stressful stimuli and other emotions.
70
ANS vs. Somatic motor system
ANS – involuntary, diffuse projections, slow action, innervates smooth/cardiac muscle & gland cells, disynaptic (pre/postganglionic neurons)…..SMS – voluntary, specific projections, rapid action, innervates skeletal muscle, monosynaptic
71
Autonomic NS – how it works
Unlike the somatic (motor) NS, the Autonomic NS is characterized by a 2-neuron link between CNS & peripheral target organ….Preganglionic neurons are located in the CNS (brainstem or spinal cord) and connect to Postganglionic neurons located in autonomic ganglia outside the CNS ---> Postganglionic neurons project to the target organ where they innervate smooth muscle, cardiac muscle, or glands
72
Myelination w/in the 2-Neuron System of the ANS
Transmission over PREganglionic fibers is relatively fast, b/c they are composed of myelinated fibers….. POST ganglionic fibers are unmyelinated.
73
Autonomic nervous system - Division
The ANS consists of the Sympathetic NS & the Parasympathetic NS, as well as the Enteric semi-autonomous control of digestion
74
Ganglion vs. Nucleus
Ganglion = cluster of cell bodies in peripheral NS; Nucleus = cluster of cell bodies in CNS
75
Sympathetic vs. Parasympathetic – origin of preganglionic neurons
SYMP: thoracic & lumbar spinal cord….. PARA: brainstem & sacral spinal cord
76
Sympathetic vs. Parasympathetic –location of ganglia
SYMP: near spinal cord…..PARA: near target organs
77
Sympathetic vs. Parasympathetic – ratio of pre- to post-ganglionic neurons
SYMP: 1:10 pre to post…. PARA: 1:3
78
Sympathetic vs. Parasympathetic –Neurotransmitters of preganglionic neurons
BOTH: Acetylcholine (ACh)
79
Sympathetic vs. Parasympathetic – Postanglionic
SYMP: Norepinephrine (NE) and epinephrine…. PARA: ACh
80
Role of the Sympathetic nervous system
Initiates responses to emergency or stressful situations - "fight and flight" responses
81
Organization of the Sympathetic NS – Location of Preganglionic neurons
Preganglionic neurons are located in the intermediolateral column of the thoracic & upper lumbar segments of the spinal cord, as well as in splanchnic nerves arising from the lower 7 thoracic spinal level
82
Pathway of Preganglionic Sympathetic neurons located in the thoracic/upper lumbar spinal cord
Preganglionic Sympathetic axons exit the spinal cord in the ventral roots of corresponding spinal nerves --> Pass through white ramus communicans (myelinated) ---> Enter sympathetic trunk and branch to innervate postganglionic neurons in multiple levels of the spinal trunk
83
Pathway of Preganglionic Sympathetic neurons located in splanchnic nerves
Preganglionic parasympathetic axons in splanchnic nerves pass through the spinal trunk to innervate postganglionic sympathetic neurons located in the celiac & mesenteric ganglia
84
Neurotransmitter relased by PREganglionic vs POSTganglionic neurons of the Sympathetic NS
Acetylcholine is the neurotransmitter released by preganglionic sympathetic neurons; Postganglionic sympathetic neurons release norepinephrine as their neurotransmitter.
85
Organization of the Sympathetic NS –Location of Postganglionic neurons
Located in the ganglia of the sympathetic trunk (paravertebral chain ganglia) and in the celiac & mesenteric ganglia (those involved in GI tract regulation
86
Pathway of Sympathetic Postganglionic neurons located in the paravertebral chain ganglia
From the ganglia of the sympathetic trunk (paravertebral chain ganglia). The sympathetic postganglionic axons exit the spinal trunk through the gray rami communicans (unmyelinated) ---> travel in spinal nerves to reach sweat glands, peripheral blood vessels, hair follicles, etc
87
Pathway of Sympathetic Postganglionic neurons located in the celiac & mesenteric ganglia
Axons from the postganglionic sympathetic neurons in the celiac & mesenteric ganglia form the perivascular plexuses innervating the abdominal viscera ---> regulate GI tract
88
Adrenal medulla
Specialized component of the sympathetic nervous system; functions as neuroendocrine gland; its postganglionic cells secrete epi (80-90%) & norepi (10-20%), both of which bind to adrenergic receptors, into the blood stream….Thus, rather than acting as neurotransmitters, these agents become hormones to regulate activity of distant target tissues (sympathomimetic but more widespread & slower than normal sympathetic neurons)
89
Innervations of specialized postganglionic cells of the Adrenal medulla
Innervated by preganglionic sympathetic neurons located in thoracic levels 6-9 of the spinal cord.
90
Sympathetic NS – what it controls
Vasodilation & vasoconstriction are controlled primarily by the SNS….. Increased sympathetic output causes vasoconstriction (as well as increased HR & force of contraction), while decreased sympathetic output causes vasodilation….At rest, sympathetic output maintains the vasculature in an intermediate state between constriction & dilation
91
Role of the Parasympathetic nervous system
Involved in conservation & replenishing of resources; Classically associated w/ "rest and digest" responses; The actions of the PNS generally oppose those of the sympathetic NS.
92
Organization of the Parasympathetic NS –Location of Preganglionic neurons
Preganglionic neurons of the PNS are located in brainstem nuclei & in the sacral spinal cord ; characterized by long axons
93
Pathway of Parasympathetic Preganlionic neurons located in the brainstem
The parasympathetic preganglionic fibers located in the brainstem exit in cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus) ---> innervate postganglionic neurons located in ganglia near or in the effector organ.
94
Pathway of Parasympathetic Preganglionic neurons located sacrally
The parasympathetic preganglionic axons exit the sacral portion of the parasympathetic system and travel in the splanchnic nerves to innervate ganglia associated with the colon, rectum, urinary bladder, and genital organs ---> functions to control "emptying" (e.g. urination, defecation, and erection)
95
Organization of the Parasympathetic NS –Location of Postganglionic neurons
Located in/near effector organ, and thus characterized by short axons.
96
Neurotransmitters relased by PREganglionic vs POSTganglionic neurons of the Parasympathetic NS
Both pre- & post-ganglionic parasympathetic neurons use acetylcholine as a neurotransmitter
97
Increased parasympathetic output results in….
Decreased HF & force of contraction; While parasympathetic output may result in some small amount of vasodilation, most vasodilation is controlled by decreased sympathetic output.
98
Neurotransmitters of ANS preganglionic neurons
Usually, preganglionic neurons of sympathetic & parasympathetic system release NT acetylcholine (ACh) ---> ACh acts on nicotinic cholinergic receptors on postganglionic neurons ---> depolarization & firing of postganglionic neuron ---> APs arrive at nerve terminal of postganglionic neuron then cause release of synaptic vesicles containing norepinephrine or ACh via exocytosis…… Co-localized agents (e.g. ATP, peptides) also participate.
99
Neurotransmitters of Sympathetic vs. Parasympathetic Postganglionic neurons
Sympathetic Postanglionic = Norepinephrine (NE); Parasympathetic Postganglionic = ACh
100
Receptor subtypes for ACh: Two types
Two types of cholinergic receptors to which ACh binds & elicits a cholinergic response.: 1. nicotinic (stimulated by nicotine) AND 2. muscarinic (stimulated by muscarine) receptors……. Cellular mechanisms by which ACh produces its effects are very different for nicotinic & muscarinic receptors.
101
Location of ACh receptors - Nicotinic vs. Muscarinic
Nicotinic receptors are mainly present in the cell body of postganglionic neurons of the autonomic ganglia; Muscarinic receptors are present on effector cells of cardiac muscle, smooth muscle, & glands.
102
Nicotinic receptor – what it is & what ACh does to it
A ligand-gated, non-selective cation channel….. When ACh binds it, the ion channel opens & allows rapid movement of Na+ & K+ across the membrane---> depolarization & excitation
103
Muscarinic receptor – what it is & what ACh does to it
Located in cell membrane, linked to a GTP-binding (G) protein….. When ACh binds the extracellular site of the muscarinic receptor protein, a conformational change occurs w/in it ---> "activation" of G protein coupled to the receptor ---> G protein then either stimulates or inhibits other intracellular effectors such as enzymes or ion channels ---> physiological response.
104
Five subtypes of muscarinic receptors
M1-M5; Different muscarinic receptors are coupled to different effectors within a cell….. Thus, simple ACh can produce various physiological responses in different cell types, depending on which muscarinic receptor subtype is activated
105
Muscarinic receptors & hyperpolarization
In Atrial cells, ACh released from vagus nerve binds to muscarinic receptor ---> activates G protein, which opens K channels ---> hyperpolarization & slowing down of HR
106
Muscarinic receptors & depolarization
In some cells, activation of muscarinic receptors causes a different type of K+ channel (than is opened in Atrial cells by ACh binding to muscarinic receptors) to close ---> sustained depolarization of the neuron.
107
Receptors of ACh vs. NE
ACh: nicotinic vs. muscarinic….. NE: alpha- & beta-adrenergic
108
Receptor subtypes for Norepinephrine vs. Epinephrine
Like w/ cholinergic receptors, there are multiple receptor subtypes for NE (NT for adrenergic system)….. Adrenergic receptors consist of alpha (α) and beta (β) receptors, subdivided into α1, α2, β1, and β2….NE only activates α1, α2, and β1 receptors….. Epinephrine (released from adrenal medulla into bloodstream) activates all 4 subtypes.
109
Activity of the autonomic nervous system is regulated by…
…information coming from visceral afferents and from higher CNS centers.
110
Inputs to preganglionic neurons…
Visceral sensory input <-- hypothalamus (in forebrain)
111
Autonomic reflexes – where they are organized
Autonomic reflexes are organized in the spinal cord & brainstem
112
Organization of the Baroreflex (an autonomic reflex)
Baroreflex is organized in the medulla w/afferent info transmitted in glossopharyngeal nerve (cranial nerve IX) from the carotid sinus to the dorsal vagal complex of the medulla, which in turn contains neurons projecting to regions of the medulla that regulate sympathetic & parasympathetic activity.
113
Location of Organization of the respiratory reflexes (autonomic reflexes)
Organized in the pons
114
Location of organization of the pupillary reflexes (autonomic reflexes)
Organized in the midbrain; allow visual system to rxt to different light levels (dilations/constriction); unconscious, involuntary
115
Cardiovascular regulation by nervous system
Sympathetic/parasympathetic control of HR & BP; Humoral response (via bloodsream); Baroreceptor reflex
116
Norepinephrine & Sympathetic regulation of the CV system
Sympathetic stimulation --> increase NE ---> increased BP (increase HR & contractile force; vasoconstriction)
117
Acetylcholine & Parasympathetic regulation of the CV system
Parasympathetic stimulation ---> increase ACh ---> decreased BP (decreased BP & contractile force)
118
Baroreceptor reflex
Low BP ---> relative increase in sympathetic output (send info to medulla)….. High BP ---> relative increase in parasympathetic output
119
Hypothalamus & the ANS
"Head ganglion" of the autonomic nervous system, b/c it integrates info from several brain regions in order to convey the needs of the organism to the preganglionic autonomic centers in the brainstem & spinal cord….. It also coordinates humoral (i.e., hormonal) response via pituitary & somatic motor response….. It also coordinates the visceromotor response via the ANS, in order to maintain homeostasis. [EX: Hypothalamus stimulates the release of vasopressin from the posterior pituitary into the bloodstream, resulting in vasoconstriction.]
120
Humoral regulation via Hypothalamus
Hypothalamus controls release of hormones via pituitary (Posterior pituitary (part of the brain) & Anterior pituitary (a gland))
121
Vasopressin (ADH)
Low BP detected by subfornical organ ---> release of vasopressin from posterior pituitary ---> causes vasoconstriction & increases water retention via kidneys ---> increased BP
122
Renin & angiotensin
Low BP ---> renin released from kidneys ---> angiotensinogen to angiotensin (I --> II) vasoconstriction, increases water retention via kidneys, activates neurons in subfornical organ ---> increased BP
123
Clinical significance of different receptor types in different tissues and differential activation by norepi & epi:
Drugs are available that selectively activate or inhibit the subtypes of adrenergic receptors (EX: To counteract bronchoconstriction in asthma or severe anaphylactic rxns, epi or a more selective β2 agonist is administered to initiate bronchodilation; Beta-blockers are used to treat HTN & CAD)
124
Atropine
Sympathomimetic drug = muscarinic (M2) antagonist in heart ---> increases HR
125
Propranolol
Parasympathomimetic drug = Beta-adrenergic (B1&2) antagonist in heart ---> decreases HR
126
Adrenergic receptor α1 agonist & its effect of agonist
Sympathomimetics….EX: Phenylephrine….Effect: Vasoconstriction in skin
127
Adrenergic receptor α2 agonist & its effect of agonist
Sympathomimetics….EX: Clonidine….Effect: Presynaptic inhibition of Norepi release; Some vasoconstriction
128
Adrenergic receptor β1 agonist & its effect of agonist
Sympathomimetics….EX: Dobutamine….Effect: Increased HR
129
Adrenergic receptor β2 agonist & its effect of agonist
Sympathomimetics….EX: Albuterol….Effect: Increased HR, Vasodilation in skeletal muscle
130
Adrenergic receptor α1 agonist & its effect of antagonist
Parasympathomimietic….EX: Doxazosin….Effect: Blocks receptor agonist effects of vasoconstricion in the skin
131
Adrenergic receptor α2 agonist & its effect of antagonist
Parasympathomimietic….EX: Trazodone….Effect: Blocks receptor agonist effects of presynaptic inhibition of NE release & some vasoconstriction
132
Adrenergic receptor β1 agonist & its effect of antagonist
Parasympathomimietic….EX: Atenolol….. Effects: Block receptor agonist effects of increased HR
133
Adrenergic receptor β2 agonist & its effect of antagonist
Parasympathomimietic….EX: Butaxamine….. Effects: Blocks receptor agonist effects of increased HR & vasodilation in skeletal muscle
134
Agonists of cholinergic receptors – activity
Parasympathomimetic
135
Antagonists of cholinergic receptors – activity
Sympathomimetic
