Physiology Exam 2: Lectures 6-10

The autonomic nervous system does not initiate heartbeat it__________

Modulates rhythm and force

Cardiac centers in the reticular formation of the medulla oblongata _______

initiate autonomic output to the heart

Is smooth muscle striated?

No it is not

What does calcium bind to in smooth muscle?

Calmodulin

What helps to anchor actin to the ECM and other smooth muscle fibers?

Dense bodies

Does smooth muscle have z lines?

No it does not

What is the source of calcium in smooth muscle contraction?

the ECF (a fraction from the SR)

What causes smooth muscle contraction? Is it voluntary?

No it is involuntary

Responds to the ANS, stretch, chemicals, temperature

How are smooth muscle contractions characterized?

Slow, sustained, high tension contractions

Is smooth muscle multi or mononucleated?

Mononucleated

In blood vessels where is the smooth muscle found?

Tunica media

Is all smooth muscle directly connected to a neuron?

No

Can smooth muscle undergo hyperplasia and mitosis?

Yes, unlike skeletal muscle it can

What are the neurotransmitters of the postganglionic sympathetic nervous system?

Norepinephrine (ACh only at sweat glands)

What are the neurotransmitters of the postganglionic parasympathetic nervous system?

Acetylcholine

All varicosities of the same nerve will

have the same neurotransmitter

Circular arrangements of smooth muscle will help to

constrict or dilate the lumen (sphincters)

Longitudinal arrangements of smooth muscle will help to

Propel objects up or down its tract

What are the two types of smooth muscle?

Multi unit (A)

Single unit (B)

In multi unit smooth muscle, each cell has

their own autonomic nerve connection

Does multiunit fire spontaneously or in response to stretch?

No it does not fire in response to stretch or spontaneously

Example of a multiunit smooth muscle

Iris

In visceral, or single-unit smooth muscle, describe the contraction

It contracts as a unit due to action potential and gap junctions

Can single unit smooth muscle fire spontaenously?

Yes due to the fluctuating threshold potential

Can stretch cause a single unit smooth muscle to fire ?

Yes, this type is responsive to stretch

What is a key difference between the two types of smooth muscle?

Gap junctions are present in the single unit smooth muscle

During smooth muscle contraction, what is the first step?

Calcium binds to calmodulin

During smooth muscle contraction, what is the second step?

Myosin light chain kinase phosphorylates the myosin neck, activating the ATPase

During smooth muscle contraction, what is the third step?

The activated myosin ATPase initiates cross bridge cycling and power strokes through hydrolysis, and pulls the dense bodies together

What can cause SR release of calcium in smooth muscle?

IP3 or calcium induced calcium release

How is intracellular calcium removed?

Sodium-calcium exchange

Ca++ ATPases

How does smooth muscle relax?

The removal of Ca++

Removal of Pi on myosin necks via phosphatase

How is tone maintained in smooth muscle?

Through tonic contractions achieved through the latch bridge mechanism

Describe the latch bridge mechanism

The myosin will bind to the actin then get its phosphate removed, inactivating the myosin ATPase, which will cause the myosin head and actin to be bound until it is reactivated

The parasympathetic system (craniosacral) arises from

cranial nerves 3, 7, 9, 10 and the sacral portion of the spinal cord

The sympathetic system (thoracolumbar) arises from the

T1-L2/3 spinal cord

Preganglionic neurons are (myelinated or unmyelinated)

Myelinated

Postganglionic neurons are (myelinated or unmyelinated)

Unmyelinated

What do all prenganglionic neurons in the ANS use as a neurotransmitter?

Acetylcholine onto nAChR

What do postganglionic neurons use as a neurotransmitter in the sympathetic nervous system?

Norepinephrine onto adrenergic receptors

What do postganglionic neurons use as a neurotransmitter in the parasympathetic nervous system?

ACh onto muscarinic receptors

Are both divisions of the ANS active at rest? Which one predominates?

Yes

Para dominates @ rest

Some effects of sympathetic excitation

Dilated pupils

Dilates bronchi

Increased HR

CAT release

Inhibits GI and urination

Fuel mobilization

What is a key difference in the preganglionic neurons between the para and symp system?

Parasympathetic preganglionic fibers may extend all the way to the effector organ meanwhile sympathetic fibers pass through the sympathetic chain

A paravertebral ganglion is one that is

including the interface between the pre and postganglionic sympathetic neuron in the ganglion sympathetic chain

A prevertebral ganglion is one that is

Including the interface between the pre and postganglionic sympathetic neurons in the periphery, otherwise known as a PREvertebral ganglion

What is a splanchnic nerve?

Paired autonomic nerves that carry both visceral sympathetic effector fibers and sensory fibers

What is unique about the sweat glands, vascular smooth muscle and the adrenal glands?

THEY ARE ONLY INNERATED BY THE SYMPATHETIC SYSTEM

The cholinergic muscarinic receptor relies on

second messengers

The cholinergic muscarinic receptor relies on

a ligand channel

There are two types of adrenergic receptor, alpha and beta, what do they rely on

second messengers (NOT ion channels)

How is norepinephrine broken down?

Monoamine oxidase and catechol o methyl transferase

MAO and COMT

What do alpha 1 adrenergic receptors control?

Most vascular smooth muscle (CONSTRICTION)

Visceral smooth muscle will constrict or dilate depending on the organ

What do alpha 2 adrenergic receptors control?

located on presynaptic side and inhibits release of CATs , negative feedback (vasodilation)

What do Beta 1 adrenergic receptors control?

Heart, agonists, increase rate and contractility

What do beta 2 adrenergic receptors control?

respiratory, uterine, GI, smooth muscle, skeletal muscle blood vessels, glycogenolysis or GNG Relaxes these (brocnchodilation, skeletal muscle BF dilation, GI inhibition)

What is important to note about the effects of norepinephrine vs epinephrine at Beta 2 receptors?

Epinephrine is more effective here

What are the three characteristics of horner syndrome?

Ptosis

Anhydrosis

Miosis

May result from obstructions of sympathetic nervous system

If a patient is given an alpha 1 blocking drug, what can you expect?

Decreased blood pressure

(Alpha 1 vasoconstricts, blocking it will cause vasodilation and dec bp)

What are some possible symptoms of nerve gases (anti AChesterase drugs)?

Salivation, lacrimation, urination, diarrhea, difficulty breathing, muscle spasms etc

An increase in activation/firing of the carotid and aortic bodies would result in

A decrease in activation of the pressor area

How do you take blood pressure?

Palpation —> Auscultation (korotkoff sounds)

What is the first korotkoff sound indicative of? And the last sound?

Systolic

Diastolic

The vasomotor center of the medulla exerts ________ control over blood vessels throughout the body

sympathetic

What is the pressor area of the vasomotor center responsible for?

Stimulation of vessel vasoconstriction

What is the depressor area of the vasomotor center responsible for?

indirectly stimulating vessels to dilate

There are three autonomic reflexes integrated in the vasomotor center, what are they?

Baroreflexes

Chemoreflexes

Medullary ischemic reflex

Which part of the vasomotor center is always on or “tonically active”

The pressor area

What cranial nerve serves the carotid baroreceptors?

CN 9

What cranial nerve serves the aortic arch baroreceptors?

CN 10

When the baroreceptors fire, what occurs?

Excitation of the depressor area leading to inhibition of the pressor area

Lowering BP

What is the vagal area of the brain otherwise known as?

The cardioinhibitory area

The cardioinhibitory center is activated when the baroreceptors fire, what does it do?

Increase vagus nerve activity —> lower HR —> lower BP

What is a chemoreflex?

An automatic response to changes in blood chemistry, especially pH as well as O2 and CO2 concentrations

What are the names of the specific chemoreceptors in the heart?

carotid bodies and aortic bodies

Local buildup of CO2 can cause

vasodilation at the site of accumulation for inc blood flow

Chemoreflexes are more of a (rescue or day - day) type of thing

rescue or emergency

What is the primary role of chemoreflexes?

Adjust respiration in response to changes in blood chemistry

What is the secondary role of chemoreflexes?

Hypoxemia, hypercapnia and acidosis stimulate chemoreceptors.

Act through the vasomotor center to VASOCONSTRICT, increasing BP, Inc lung perfusion and gas exchange

What is the medullary ischemic reflex?

A automatic response to a drop in perfusion of the brain

Does the medulla oblongota monitor its own blood supply?

Yes it does

If the medullary ischemic reflex detects ischemia, what corrective reflexes will it trigger?

increased sympathetic signaling from cardiac and vasomotor centers to the heart and blood vessels causing

Inc HR and contractility

Widespread vasoconstriction

Raises BP and restores normal perfusion to the brain

What is circulatory shock?

Any state in which cardiac output is insufficient to meet the body’s metabolic needs

What is hypovolemic shock caused by?

Hemorrhage, dehydration, burns

What is cardiogenic shock caused by?

Heart failure

Failure of the pump —> decreased CO —> decreased BP

What is obstructive circulatory shock caused by?

PE, cardiac tamponade (inc ven pressure —> dec Ven retrn —> dec SV —> dec CO)

What are the types of vasogenic circulatory shock?

Neurogenic

Septic

Anaphylactic

Traumatic

What is neurogenic shock?

Loss of vasomotor tone —> Vasodilation

Brain or SCI which inhibits tonic sympathetic activity

What is septic shock?

Bacterial toxins trigger vasodilation and increased cap permeability (edema)

What is anaphylactic shock?

Severe immune reaction to antigen—> histamine release —> generalized vasodilation —> inc cap permeability (edema)

What is traumatic shock?

Cytokine and histamine response from major trauma causing widespread vasodilation

What is the main outcome with all the different vasogenic shock types?

Decreased TPR (Inc vasodilation) leads to dec BP

What are some signs and symptoms of circulatory shock?

Elevated HR

Pale (hypovolemic) or flushed (vasogenic)

Sweaty

Fevers

Weak

Dec BP

Low urine output

Altered mental state

What is compensation?

Redistribute blood flow to vital organs

Reduce venous capacity

Cardiac stimulation
Autotransfusion

Kidneys conserve volume

What is decompensation?

Worsening perfusion leads to more strain on a hard working heart which leads to more demand ischemia

Low flow leads to diffuse coagulation (DIC) which can lead to obstructive shock which dec VR

What does systolic BP do with age?

Increases w/ age

What does diastolic BP do with age?

Inc until age 50 then decreases with age

Pulse pressure will increase as SBP (inc/dec) and DBP (inc/dec)

Inc

Dec

What are some HTN consequences?

Inc risk of stroke, heart attack, atherosclerosis, heart failure, and associated risk of death and disability assoc w each disease

What are some causes of HTN?

Multifactorial

Primary “essential” HTN

Secondary HTN

Primarily due to inc TPR

Baroreceptor is not the cause but it resets at new BP over time