Unit 1 Lecture 5 Flashcards by Emma Carlton

What are the two divisions of the Autonomic nervous system?

Sympathetic and parasympathetic divisions

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What are the characteristics of the sympathetic neurons?

Preganglionic neurons: short axons release ACh

- Postganglionic neurons: long axons release NE

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What are the characteristics of the parasympathetic neurons?

Preganglionic neurons: Long axons release ACh

Postganglionic neurons: short axons release ACh

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Where is the sympathetic division found in the body?

Thoracic and lumbar region of the spine

“thoracolumbar”

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what structure in the spine contains a group of nerves?

Ganglion

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What ganglion in the thoracolumbar spine is home to the sympathetic nervous system?

Superior cervical ganglion, Middle cervical ganglion, and inferior cervical ganglion

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Where does sympathetic nerves go to?

Heart

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Where in the heart is effected by the sympathetic division?

SA/VA node, and ventricular muscle fibers

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Where is the parasympathetic nervous system start in the body?

Brain

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What is the major nerve used in the Parasympathetic division?

CN X

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Where does the Cranial Nerve X supply?

Heart

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What part of the heart is effected by the CN X?

atrial muscle fibers and SA/AV nodes

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Define the cardiac cycle

Everything associated with one heartbeat

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Define systole

heart contraction

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What happens during systole?

ventricular contraction and blood ejection

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Define diastole

heart relaxation

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What happens during diastole?

ventricular relaxation and blood filling

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What is the typical cardiac cycle period at rest?

0.8 seconds at rest

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What is another name for heart rate?

“cardiac frequency”

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How do you measure heart rate?

w/ ECG

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What is the formula for heart rate?

1 beat / Cardiac cycle period in sec X 60 sec/ min

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What system controls heart rate?

autonomic nervous system

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the effects of the ans on heart rate is called what?

chronotropic effects

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What are the 2 ways the ANS can modify heart rate?

circulating hormones

2. higher brain structures

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what are the circulating hormones in the body?

NE, epinephrine, and thyroxine

what do "higher brain structures" do?

influence sympathetic and parasympathetic neurons that send nerve fibers to the heart

Where are the para/sympathetic neurons specifically located in the brain?

CARDIAC CENTERS - in caudal portions of the medulla oblongata

What are the 2 major cardiac centers in the medulla oblongata?

1. Cardioacceleratory center | 2. Cardioinhibitory center

What part of the ans does the cardioacceleratory center control?

sympathetic

What part of the ans does the cardioinhibitory center control?

parasympathetic

What is the path of the sympathetic neurons controlling HR?

1. Neurons in the cardioacceleratory center of medulla oblongata (in brain) go through the lateral grey horns in the thoracic spine 2. Preganglionic neurons synapse on postganglionic neurons in the sympathetic chain ganglion 3. postgang. neurons send axons to the SA node, AV node, and ventricular cardiac muscle fibers

What sympathetic preganglionic neurons release onto postgang neurons?

acetylcholine (ACh)

Where do sympathetic preganglionic neurons synapse to postganglionic neurons?

sympathetic chain ganglion | basically a bugle in the neuron outside of the thoracic spine

What does ACh bind to on post gang neurons?

nicotinic receptors on the dendrites and cell bodies of the post gang neurons

What does the sympathetic post gang neurons synapse onto?

SA node, AV node, and ventricular cardiac muscle fibers

What does the sympathetic postgang neurons release onto the heart cells?

Norepinephrine (NE)

What does NE from sympathetic post gang cells activate in the heart?

beta-1 adrenergic receptors

What does NE do to the pacemaker cells in the SA and AV nodes in the sympathetic division?

increases Na+ concentration into the cell

What does more Na+ do the pacemaker potential in the sympathetic division?

increases rate of depolarization (steeper pacemaker potential)

What happens when there's a steeper pacemaker potential under sympathetic stimulation

pacemaker cells can reach threshold more frequently and HR RISES

What is the path of the neurons in the parasympathetic cardioinhibitory center?

1. Neurons in the cardioinhibitory center of medulla oblongata send signals straight to heart through the Vagus nerve (CN X)

What nerve carries the parasympathetic neurons?

CN X (Vagus)

Where does the parasympathetic postgang neuron synapse?

SA node, AV node and ATRIAL muscle fibers | not ventricular fibers like sympathetic stimulation

What does the parasympathetic neurons release on the heart cells?

ACh

What effect does parasympathetic postgang ACh have on the heart?

slows the heart rate

Why does parasympathetic ACh slow the heart?

ACh increases K+ permeability OUT of pacemaker cells

What happens when a lot of K+ leaves the pacemaker cell?

hyperpolarization (gets more negative)

What happens to pacemaker cells when they hyperpolarize?

it takes more time for pacemaker cells to reach threshold and HR SLOWS

What does hormone levels do to heart rate and contractility?

epinephrine and thyroxine INCREASE heart rate and contractility

What does hypocalcemia do to heart rate and contractility?

reduced ionic Ca DEPRESSES contractility

What does hypercalcemia do to heart rate and contractility?

excess ionic Ca dramatically INCREASES heart irritability and leads to spastic contractions

What does Hypernatremia do to heart rate and contractility?

excess ionic Na+ blocks heart contraction by inhibiting ionic calcium transport

What does hyperkalemia do to heart rate and contractility?

excess ionic K+ leads to heart block and cardiac arrest

What effect does the sympathetic ns have on heart rate?

Increases heart rate

What effect does the parasympathetic ns have on heart rate?

Decreases heart rate

What does sympa postgang neurons release on the heart?

What effect does NE have on the heart?

Causes more Na+ to enter the cell

What effect does Na+ entering the cell have on the heart rate?

Increases the depolarization of the membrane potential -> more frequent heart beats -> INCREASES HEART RATE

What does parasympa postgang neurons release on the heart?

ACh

What effect does ACh have on the heart?

Causes more K+ to LEAVE the cell

what effect does K+ leaving the cell have on the heart rate?

Increases the hyperpolarization of the membrane potentials -> less frequent heart beats -> DECREASES HEART RATE

What effect does K+ leaving the cell have on Na+ and Ca+ entering the cell?

K+ blocks Na+ and Ca+ channels in the atria causing the heart from beating as frequently -> DECREASED HEART RATE