PULM/HEME EXAM 1 🫁

Voltage (V)

Difference in charge between inside and outside of the cell (membrane potential, Vm).

Membrane Potential (Vm)

Voltage across the cell membrane.

Current (I)

Flow of electric charge over time.

Conductance (g)

How easily ions flow (ease of current flow).

Resistance (R)

Opposition to ion flow.

Nernst Potential (Eion)

Voltage at which only that ion is at equilibrium (no net flow).

Balance of chemical gradient vs electrical gradient for that ion.

Electrochemical Gradient

Combination of voltage difference (electric) + concentration difference (chemical)

0 mV

When all Na+ channels are open

Depolarization

Membrane potential becomes less negative (moves toward +).

Often caused by Na⁺ or Ca²⁺ flowing in.

Hyperpolarization

Membrane potential becomes more negative.

Often caused by K⁺ flowing out.

Na⁺/K⁺ pump

Exchanges 3 Na⁺ out for 2 K⁺ in; uses energy.

The three main types of channels are __________, __________, and __________.

voltage-gated, ligand-activated, inward rectifier.

In most neuronal cells, the relative permeabilities are __________ >> __________ > __________ >> __________.

K⁺ >> Cl⁻ > Na⁺ >> Ca²⁺.

Refractory period

Period after an action potential when it is harder to generate another one because potassium channels remain open.

SNARE mechanism steps

Docking, priming (ATP use), calcium-triggered fusion.

Synaptotagmin

A specialized protein that responds to calcium ions to trigger vesicular exocytosis.

The sympathetic nervous system has a __________ origin.

Thoracic lumbar.

The parasympathetic nervous system has a __________ origin.

Craniosacral.

Sympathetic ganglia include __________ and __________ ganglia.

Paravertebral, prevertebral.

Key Cranial Nerves of ANS

3,7,9,10

Parasymphateic ganglia include __________ and __________ ganglia.

Peripheral; terminal

Parasympathetic postganglionic neurotransmitter

Acetylcholine

Sympathetic postganglionic neurotransmitter

Norepinephrine

Differences between ANS divisions - Parasympathetic outflow

Cranio-sacral (CIII, VII, IX, X; S2 to S4).

Differences between ANS divisions - Sympathetic outflow

Thoraco-lumbar (T1 to T12; L1 to L3).

Parasympathetic ganglia are __________; sympathetic ganglia are __________.

Peripheral or terminal, paravertebral or prevertebral.

Parasympathetic preganglionic fibers are __________ and postganglionic fibers are __________.

Long (myelinated), short (non-myelinated).

Sympathetic preganglionic fibers are __________ and postganglionic fibers are __________.

Short (myelinated), long (non-myelinated).

Parasympathetic stimulation is usually __________; sympathetic stimulation is usually __________.

Localized, generalized.

Sympathetic postganglionic neurotransmitter is usually __________.

Norepinephrine.

**Exception: Sympathetic preganglionic neurons synapse on chromaffin cells, which release epinephrine/norepinephrine.

Parasympathetic postganglionic neurotransmitter is __________.

Acetylcholine.

Sympathetic postganglionic neurons release acetylcholine where?

Sweat glands

Sympathetic preganglionic neurons synapse on chromaffin cells, which release ________

epinephrine/norepinephrine.

Parasympathetic functions include decreases in __________, __________, __________, and __________, and increases in __________ and __________.

Cardiac output, respiration, mental activity, blood glucose; gut motility, pupil constriction.

Sympathetic functions include increases in __________, __________, __________, __________, __________, and __________.

Mental activity, respiratory rate, heart rate, arterial blood pressure, blood glucose and free fatty acids, blood flow.

Single innervation examples

Peripheral blood vessels, spleen, sweat glands, piloerector muscles (sympathetic only).

No innervation examples

Blood vessels with ACh, histamine, angiotensin receptors.

Adrenergic receptor α1

Most postsynaptic, excitatory.

Adrenergic receptor α2

Many presynaptic, inhibitory.

Adrenergic receptor β1

Heart, gut, excitatory.

Adrenergic receptor β2

Remainder, inhibitory.

Adrenergic receptor β3

Fat cells, excitatory.

Chronotropy

heart rate (pace of the SA node)

Inotropy

force of contraction

Parasympathetic vs Sympathetic Heart Control

Parasympathetic: Controls chronotropy

Sympathetic: Controls chronotropy and inotropy

Sympathetic postganglionic nerves to the heart come from which ganglia?

Stellate and inferior cervical ganglia.

Sympathetic heart effects include positive __________ and __________ effects.

Chronotropic, inotropic.

Result: Faster heart rate and more forceful contractions

Parasympathetic postganglionic fibers to the heart terminate in which structures?

SA node, atria, AV node.

The parasympathetic nervous system has no innervation of the __________.

Ventricular muscle.

baroreceptors

detect changes in blood pressure

Baroreceptor reflex - low BP

↑ Sympathetic tone (↑ HR, ↑ contractility, vasoconstriction); ↓ parasympathetic tone.

Baroreceptor reflex - high BP

Opposite of low BP response.

BP drops

Heart rate ↑ (positive chronotropy)

Heart contraction ↑ (positive inotropy)

Vessels constrict ↑ TPVR

Parasympathetic ↓

BP rises (opposite)

Heart rate ↓

Heart contraction ↓

Vessels dilate ↓ TPVR

Parasympathetic ↑

Parasympathetic tone in lung

Bronchoconstriction (M3), more mucus (harder to breathe)

Sympathetic tone in lung

Bronchorelaxation (β2), possibly by suppressing parasympathetic tone.

Sympathetic GI effect

↓ tone, motility, secretion

↑ sphincter activity (keeps things "closed" no time to shit!)

Parasympathetic GI effect

↑ tone, motility, secretion.

Parasympathetic eye effect

Pupil constriction (miosis) via circular muscle contraction.

Sympathetic eye effect

Pupil dilation (mydriasis) via radial muscle contraction.

Enteric Nervous System (ENS)

the gut's own "brain"

Integrates parasympathetic and sympathetic input and local reflexes

Uses multiple chemical mediators to coordinate activity

How does sympathetic function work in the ENS?

Sympathetic mainly works by modulating parasympathetic activity → slows or inhibits gut functions indirectly

Radial (dilator) muscle →

sympathetic stimulation → muscle contracts → pupil gets bigger (mydriasis)

Circular (sphincter) muscle →

parasympathetic stimulation → muscle contracts → pupil gets smaller (miosis)

Like your going to sleep!

excitatory post synaptic potential

the neuron is more likely to fire action potential this is a signal from the previous neuron that just fired an action potential

Parasympathetic lens effect

Ciliary muscle contraction → lens thickens → near vision.

Ligaments pull → lens is flat →

good for seeing far away (sympathetic)

They are strong enough to pull the lens so much that it becomes flat, as you can older this elasticity decreases and you need glasses to see far away.

If you want to see something close

Ciliary muscle contracts

Ligaments loosen

Lens becomes thicker/rounder → focuses near objects

What neurotransmitter is active at all sites of cholinergic transmission?

Acetylcholine (ACh)

Is acetylcholine a good CNS agent? Why or why not?

No, it's a poor CNS agent because it is a charged quaternary nitrogen compound and is broken down by plasma butyrylcholinesterase.

What are the two main types of acetylcholine receptors?

Muscarinic and Nicotinic receptors

How is acetylcholine (ACh) synthesized?

In a single step from choline by adding Acetyl CoA.

What enzyme catalyzes ACh synthesis?

Choline Acetyltransferase (ChAT)

Where does choline for ACh synthesis come from?

Acetylcholinesterase activity

Phosphatidylcholine

Phosphorylcholine

Where does Acetyl CoA for ACh synthesis come from?

Glycolysis

Is ChAT the rate-limiting step in ACh synthesis?

No, choline uptake is the limiting factor.

What do the Gα subunits of muscarinic (M) receptors mainly target?

Adenylyl cyclase (AC) and Phospholipase C (PLC)

Which muscarinic receptors are associated with Gαi?

M2 and M4

What is the effect of M2 & M4 activation via Gαi?

Decreases Adenylyl Cyclase (AC) activity.

What secondary effects can occur from M2 & M4 activation?

Effects via the βγ subunits

Which muscarinic receptors are associated with Gαq?

M1, M3, and M5

What is the effect of M1, M3 & M5 activation via Gαq?

Increases Phospholipase C (PLC) activity

What type of channels are nicotinic receptors?

Direct ligand-gated cation channels

How many acetylcholine (ACh) molecules are required to activate nicotinic receptors?

Two ACh molecules

Which ions pass through nicotinic receptors?

Sodium (Na⁺) and Potassium (K⁺)

What is the net effect of ion passage through nicotinic receptors?

Inward sodium current → depolarization

How fast is ACh binding and release at nicotinic receptors?

Very rapid; effects are transient (<10 ms)

What is the structural composition of nicotinic receptors?

Five subunits, 35-50% homologous; all have two α subunits

Which subunits are responsible for ACh binding?

The α subunits

What happens with long-term exposure to ACh at nicotinic receptors?

Development of a high-affinity receptor in a closed "desensitized" state.

Fast EPSP

Quick depolarization of a neuron via nicotinic receptors and acetylcholine; starts immediately and lasts milliseconds.

Slow EPSP

Gradual increase in neuron excitability via M1 muscarinic receptors and acetylcholine; starts ~1 second after stimulation and lasts up to 30 seconds.

IPSP

Inhibitory postsynaptic potential that hyperpolarizes the neuron, making it less likely to fire; mediated by M2 muscarinic, α-adrenergic, or dopaminergic receptors.

Late slow EPSP

Very long-lasting excitatory effect mediated by peptide neurotransmitters (e.g., Substance P, LHRH); starts after 10-30 seconds and lasts several minutes; regulates long-term neuronal response to repeated stimulation.

Effect of the M2 receptor on the AV node

Decrease conduction velocity

Effect of the M2 receptor on the atrium

Decrease refractory period and contractile force

Effect of the M2 receptor on the ventricle

Decrease in contractility

M3 Receptor Target and Effect

Smooth Muscle Contraction via the Gq pathway

Receptors on the Autonomic Gangila

M1 and Nicotinic Neuron (Obviously it's on the Gangila)

Nicotinic Nm Receptor Location

Skeletal muscle at neuromuscular junction (NMJ