UNIT 2 Autonomic Nervous System pharm

Nervous System

Functions to control and coordinate activity of all systems in the body
Controls and coordinates all activities in the body.

• Involuntary and voluntary control

Voluntary Control

(You choose to do it)

Things you can control on purpose.

• Walking

• Talking

• Writing

• Raising your hand

Easy memory tip: … = "I decide."

actions you control.

Involuntary Control

(Happens automatically)

Things your body does without you thinking about it.

• Heartbeating

• Breathing

• Digestion

• Blinking

Easy memory tip: … = "Body does it automatically."

actions your body controls automatically.

Two Subdivisions of the Nervous System

• 1. Central Nervous System (CNS)

• 2. Peripheral Nervous System(PNS)

1. Central Nervous System (CNS) 🧠

Made of:

• Brain

• Spinal cord

What does it do?

The … is the control center .

Item:

1. Receives information from the body

2. Interprets (understands) the information

3. Sends instructions back to the body

Example:

You touch a hot stove.

• Skin feels heat 🔥

• Message goes to the brain/spinal cord

• Brain says "That's hot!"

• Brain sends message to move your hand away

Easy memory:
👉 CNS = Control Center

2. Peripheral Nervous System (PNS) 🔌

Made of all the nerves outside the brain and spinal cord.

The PNS is like the telephone wires connecting the body to the CNS.

What does it do?

Carries messages:

• To the CNS

• From the CNS

Easy memory:
👉 … = Pathway of Nerves

• afferent nerves- sensory impulses toward CNS

• efferent nerves-motor impulses away from CNS

• cranial nerves-12 pr.

• spinal nerves-31 pr.

Afferent Nerves

• 2. Peripheral Nervous System(PNS)

Sensory Nerves 👀👂👃

These carry messages TO the CNS .

What are they carrying?

Things you:

• See

• Hear

• Feel

• Smell

• Taste

Example:

You touch ice 🧊

Message travels:

Hand → CNS

Easy memory:
👉 … = Arrives at CNS

• 2. Peripheral Nervous System(PNS)

Efferent Nerves

Motor Nerves 💪

These carry messages AWAY from the CNS .

Example:

Brain tells your arm to move.

Message travels:

CNS → Arm muscle

Easy memory:
👉 … = Exits CNS

Cranial Nerves

• 12 pairs

• Come directly from the brain

They help with:

• Vision 👀

• Hearing 👂

• Smell 👃

• Taste 👅

• Facial movements 😊

Easy memory:
👉 … = Comes from the Cranium (brain/skull)

Spinal Nerves

• 2. Peripheral Nervous System(PNS)

• 31 pairs

• Come from the spinal cord

They send messages between the spinal cord and the rest of the body.

Examples:

• Arms

• Legs

• Chest

• Back

Easy memory:
👉 … = Connect body to spinal cord

Two Subdivisions of the Nervous System

side by side

Term	Easy Meaning
CNS	Brain + spinal cord (control center)
PNS	All nerves outside CNS
Afferent	Sensory messages TO CNS
Efferent	Motor messages AWAY from CNS
Cranial nerves	12 pairs from brain
Spinal nerves	31 pairs from spinal cord

Afferent = Arrives at CNS 🚶➡🧠

Efferent = Exits CNS 🧠➡💪

Somatic Nervous System (SNS) 💪

Think of the …. as the part of the nervous system that lets you move your body on purpose .

What does it do?

It controls your skeletal muscles (the muscles attached to your bones).

Examples:

• Walking 🚶

• Running 🏃

• Writing ✍

• Smiling 😊

• Raising your hand 🙋

These are all movements you choose to make .

1. Somatic Nervous System

"Nerves branch from cranial and spinal motor nerves"

This means:

The nerves that control movement come from:

• Cranial nerves (from the brain)

• Spinal nerves (from the spinal cord)

These nerves carry messages to your muscles.

Example:

You decide to wave your hand.

1. Brain makes the decision 🧠

2. Motor nerves carry the message 📩

3. Hand muscles receive the message 💪

4. Your hand waves 👋

1. Somatic Nervous System
"Innervate skeletal muscle"

Innervate = supply nerves to

Skeletal muscle = muscles attached to bones

So this phrase means:

👉 The somatic nervous system sends nerves to skeletal muscles so they can move.

Example:

• Arm muscles

• Leg muscles

• Finger muscles

All are controlled by the somatic nervous system.

---

"Voluntary control by cerebral cortex" Voluntary

Means you control it on purpose .

Cerebral cortex

The outer part of the brain that helps you:

• Think

• Learn

• Make decisions

• Control movement

Example:

You decide to pick up a pencil.

1. Cerebral cortex says, "Pick up the pencil." 🧠

2. Message travels through nerves 📩

3. Hand muscles move ✏

Somatic Nervous System / PNS

…..

Controls voluntary (intentional) movements of skeletal muscles.

Pathway:

🧠 Brain (cerebral cortex)
➡ Motor nerves
➡ Skeletal muscles
➡ Movement

Examples:

• Walking

• Writing

• Kicking a ball

• Raising your hand

Easy Memory Trick

… = Skeletal muscles = Stuff you choose to do

👉 … = "I move it." 💪🧠

PNS

Autonomic Nervous System (ANS) - Visceral

Think of the ANS as the body's autopilot system .

It controls things that happen without you thinking about them .

Examples:

• Heartbeating ❤

• Digestion 🍔

• Breathing 😮‍💨

• Sweating 💦

• Saliva production 😋

Easy memory:
👉 Autonomic = Automatic

"Visceral"

Visceral means internal organs .

Examples:

• Heart ❤

• Stomach 🍔

• Intestines

• Lungs 🫁

• Bladder

Autonomic Nervous System (ANS) - Visceral/ PNS

"Branches of cranial and spinal motor nerves innervate cardiac and smooth muscle of internal organs and glands"

Innervate = supply nerves to

The ANS sends nerves to:

Cardiac Muscle ❤

• Heart muscle

Smooth Muscle 🫁🍔

Muscles found in organs such as:

• Stomach

• Intestines

• Blood vessels

• Bladder

Glands 💧

Make and release substances:

• Salivary glands

• Sweat glands

What's happening?

The ANS sends messages to these organs so they can work properly.

Autonomic Nervous System (ANS) - Visceral/ PNS

"Involuntary Control"

happens automatically

You do NOT have to think:

❌ "Beat heart now."

❌ "Digest lunch now."

❌ "Make saliva now."

Your body does it automatically.

---

"Regulated by hypothalamus and medulla oblongata"

These are brain areas that help control automatic body functions.

Hypothalamus

Acts like the body's thermostat 🌡

Helps control:

• Body temperature

• Hunger

• Thirst

• Sleep

Medulla Oblongata

Controls life-sustaining functions ❤

Helps control:

• Heart rate

• Breathing

• Blood pressure

Autonomic Nervous System (ANS) - Visceral

Authorhythmicity

contraction without any stimulus"

Means an organ can create its own rhythm.

Example:

❤ Heart

The heart can beat on its own without someone telling it to beat every time.

Easy memory:
👉 Auto = self
👉 Rhythmicity = rhythm

… = self-made rhythm

Autonomic Nervous System (ANS) - Visceral

"Regulates the rate at which these organs work by increasing or decreasing their activity → homeostasis"

The ANS can:

⬆ Speed ​​things up

OR

⬇ Slow things down

Example:

Running 🏃

ANS:

• Increases heart rate ❤⬆

• Increases breathing 🫁⬆

Sleeping 😴

ANS:

• Slow heart rate ❤⬇

• Slow breathing 🫁⬇

Why?

To keep the body balanced.

Autonomic Nervous System (ANS) - Visceral

PNS

side by side

Term	Easy Meaning
ANS	Automatic nervous system
Visceral	Internal organs
Innervate	Supply nerves to
Cardiac muscle	Heart muscle
Smooth muscle	Muscles in organs
Involuntary	Automatic, no thinking
Hypothalamus	Controls temperature, hunger, thirst
Medulla oblongata	Controls heart rate and breathing
Autorhythmicity	Organ creates its own rhythm
Homeostasis	Keeping the body balanced

Autonomic Nervous System = "My body does it automatically." ❤🫁🍔

Autonomic Nervous System (ANS)

1. Ganglia = Relay Stations 🚉

What are ganglia?

Ganglia are groups of nerve cell connections where messages stop briefly before continuing.

Simple idea:

Think of a ganglion as a bus station .

🧠 Spinal Cord → 🚉 Ganglion → ❤ Organ

The message stops at the ganglion and then continues to the organ.

Easy memory:
👉 Ganglia = Relay stations

• Autonomic Nervous System - continued

2. Preganglionic Nerve vs Postganglionic Nerve

Preganglionic nerve

First Neuron 🚶 What does it do?

Carries the message from the spinal cord to the ganglion .

Path:

🧠/Spinal Cord → Preganglionic Nerve → 🚉 Ganglion

Easy memory:
👉 Pre = Before the ganglion

---

3. Postganglionic Nerve = Second Neuron 🚶 What does it do?

Carries the message from the ganglion to the organ or gland .

Path:

🚉 Ganglion → Postganglionic Nerve → ❤ Organ

👉 Post = After the ganglion

Autonomic Nervous System

path

Whole Path Together Example: Heart Rate Control ❤

1. Brain/spinal cord sends message 🧠

2. Preganglionic nerve carries it 🚶

3. Message reaches ganglion 🚉

4. Postganglionic nerve carries it 🚶

5. Heart receives message ❤

6. Heart speeds up or slows down

4. Neurotransmitters (NTs)

Autonomic Nervous System

Chemical Messengers 💌

What are they?

Special chemicals that carry messages from one nerve cell to the next.

Without neurotransmitters, the message would stop.

Think of them as:

💌 "Text messages" between nerve cells

---

What do neurotransmitters do?

They:

1. Carry the message

2. Attach to receptors

3. Cause an action

Example:

Brain wants heart to beat faster ❤

Neurotransmitter is released 💌

It attaches to recipients on the heart 🔑

Heart responds ❤⬆

Receivers = Locks 🔒 Receptors

They are special places on organs that receive neurotransmitters.

Easy way to remember:

🔑 Neurotransmitter = Key

🔒 Receiver = Lock

When the key fits the lock, an action happens.

• Autonomic Nervous System - continued

meaning

• Made up of ganglia-collections of synapses (impulse travels from one neuron to the next) between preganglionic and postganglionic nerves

• Preganglionic nerve- emerges from spinal cord

• Postganglionic nerve- travels from ganglion to internal organ or gland

• Neurotransmitters (NT)- keep impulse going, chemical substance, stimulates internal organ or gland to produce a change/action by binding to receptors

• Autonomic Nervous System - continued
  
  side by side

Term	Easy Meaning
Ganglia	Relay stations where messages stop
Preganglionic nerve	Carries message from spinal cord to ganglion
Postganglionic nerve	Carries message from ganglion to organ
Neurotransmitter (NT)	Chemical messenger
Receptor	Receives the neurotransmitter
Organ response	Action happens (heart beats, gland secretes, etc.)

PRE = Before ganglion
🧠 → Preganglionic → 🚉

POST = After ganglion
🚉 → Postganglionic → ❤

NT = Chemical messenger 💌

Receiver = Lock 🔒

NT + Receiver = Action! ⚡❤🫁🍔

1. Sympathetic Nervous System

ANS

"Fight, Fright, or Flight" 🏃💨

This system turns the body ON during stress, danger, excitement, or emergencies.

What's happening?

❤ Heart rate increases

🫁 Breathing increases

👀 Pupils get bigger

🍔 Digestion slows down

💪 More blood goes to muscles

Example:

You see a big dog running toward you.

Your sympathetic nervous system says:

⚡ "Emergency! Get ready to run!"

Your heart beats faster and your muscles get ready for action.

Your heart beats faster and your muscles get ready for action.

Adrenergic

This means it mainly uses the neurotransmitter norepinephrine (and epinephrine) .

You don't need to memorize much right now—just remember:

👉 Sympathetic = Adrenergic

2. Parasympathetic Nervous System

ANS

"Rest and Digest" 😌🍔

This system calms the body down and helps it conserve energy.

What's happening?

❤ Heart rate slows

🫁 Breathing slows

🍔 Digestion increases

😴 Body relaxes

💧 More saliva is produced

Example:

You just finished eating dinner and are relaxing on the couch.

The parasympathetic nervous system says:

✅ "Everything is safe. Time to relax and digest food."

Cholinergic

This means it mainly uses the neurotransmitter acetylcholine .

👉 … = Cholinergic

Most Organs Receive Both Nerves

Subdivisions of the ANS

Most organs have:

• A sympathetic nerve

• A parasympathetic nerve

These work like a gas pedal and a brake pedal in a car.

Heart Example ❤

Sympathetic
⬆ Speeds heart rate up

Parasympathetic
⬇ Slows heart rate down

The body chooses which one is needed.

Exception: Blood Vessels 🩸

Most blood vessels receive only sympathetic nerves , not both divisions.

This is an important exception to remember.

Sympathetic Nervous System

• fight, fright, flight

  • adrenergic
    

Parasympathetic Nervous System

• rest and digest

  • cholinergic

Sympathetic vs Parasympathetic

Sympathetic	Parasympathetic
Fight, fright, flight	Rest and digest
Emergency mode	Relax mode
Speeds heart up ❤⬆	Slows heart down ❤⬇
Digestion decreases 🍔⬇	Digestion increases 🍔⬆
Adrenergic	Cholinergic

Sympathetic = Stress

"Fight or Flight"
🏃💨❤⬆👀⬆

Parasympathetic = Peace

"Rest and Digest"
😌🍔❤⬇

Sympathetic = Speeds things up ⚡
Parasympathetic = Slows things down and helps digestion 🌿🍔

Adrenergic System

Sympathetic Nervous System

"Fight, Flight, Fright" ⚡🏃

Think of the … System as your body's emergency mode .

When you're stressed, scared, excited, sick, or in danger, this system turns on to help you respond quickly.

What does it do?

It prepares your body to:

🏃 Run away (flight)

🥊 Fight

😨 React to fear (fright)

Example:

A car suddenly swerves toward you.

Your body instantly:

❤ Heart beats faster

🫁 Breathing increases

👀 Pupils get bigger

💪 Muscles get more blood and energy

This is the adrenergic system at work.

"Regulates activity of internal organs and glands during stressful situations"

Adrenergic System

This means the adrenergic system controls organs during stress.

Main organs affected:

❤ Heart

🧠 Brain

🫁 Lungs

It makes them work harder and faster.

---

"Large amount of energy exerted physically and mentally" What does this mean?

Your body uses lots of energy when stressed.

Physically:

🏃 Running

🥊 Fighting

🚴 Exercising

Mentally:

😰 Anxiety

📚 Taking an exam

🚨 Emergency situations

The body burns extra energy to stay alert and ready.

"Whole body will be stimulated"

Adrenergic System:

This is very important!

The adrenergic system affects many organs at the same time .

Not just one body part.

Example:

When scared:

❤ Heart speeds up

🫁 Lungs work harder

👀 Eyes widen

🍔 Digestion slows

Everything happens together.

"Daily stresses, illness, anxiety, crisis"

The adrenergic system doesn't only turn on during emergencies.

It can also be activated by:

📚 Exams

😰 Anxiety

🤒 Illness

🚨 Crisis

🏃 Exercise

"Gandlia are far from the effector organ"

Adrenergic System

Sympathetic Nervous System

Effector organ

= the organ that does the work

Examples:
❤ Heart
🫁 Lungs
🍔 Stomach

Simple idea:

In the sympathetic nervous system, the ganglia (relay stations) are usually closer to the spinal cord and farther from the organ.

Think:

🧠 → 🚉 Ganglion → ➖➖➖➖➖ → ❤ Organ

Long postganglionic nerve.

You mainly need to remember:

👉 …. ganglia are far from the organ.

"Adrenal medulla releases epinephrine and some norepinephrine"

Adrenergic System

Adrenal medulla

Part of the adrenal glands that sit on top of the kidneys.

Think of it as an emergency hormone factory .

What does it release?

⚡ Epinephrine (adrenaline)

⚡ Norepinephrine

These chemicals travel through the blood.

What do they do?

They help create sympathetic responses:

❤ Heart beats faster

🫁 Breathing increases

💪 More energy available

👀 Pupils dilate

"Endocrine function" Endocrine

= hormones released into the bloodstream

Unlike nerves, hormones travel through the blood to reach organs.

Think:

🏭 Adrenal medulla
⬇
⚡ Epinephrine released
⬇
🩸 Bloodstream
⬇
❤🫁💪 Organs respond

Adrenergic System

Sympathetic Nervous System

Term	Easy Meaning
Adrenergic System	Fight, flight, fright system
Purpose	Helps body handle stress
Affects	Heart, lungs, brain, muscles
Whole body stimulated	Many organs respond together
Epinephrine	Adrenaline
Norepinephrine	Sympathetic neurotransmitter
Adrenal medulla	Releases adrenaline
Endocrine	Hormones travel through blood

Adrenergic = Adrenaline ⚡

Stress → Adrenal medulla → Epinephrine → Fight or Flight

😨 ➡ ⚡ ➡ ❤⬆ 🫁⬆ 💪⬆

Adrenergic System = Emergency Mode 🚨🏃💨

Adrenergic System: “Fight, Flight, Fright”
Sympathetic Nervous System

• regulates activity of internal organs and glands during physical and mental stressful situations (heart, brain, lungs)

• large amt of energy exerted physically and mentally

• WHOLE body will be stimulated, not just a part; one neuron acts on many

• daily stresses, illness, anxiety, crisis

• ganglia are far from effector organ

• adrenal medulla releases epinephrine and some norepinephrine that travel to receptor sites and produce sympathetic responses (endocrine function)

Neurotransmission of Sympathetic Nervous System

ACh = At ​​the Ganglion/ cholinergic

• NT released at ganglia from presynaptic nerve endings (both systems)

NE = Nerve Ending to Organ/ adrenergic

• NT released at postganglionic nerve endings

• synthesized from dopamine 

• released by adrenal medulla and neurons

EPI = Emergency Adrenaline/ adrenergic

• acts on adrenergic receptors

• produced by adrenal medulla

• Dopamine (DA)

  • sympathetic and CNS neurotransmitter 

  • precursor to NE 

  • stimulates many receptors (alpha, beta, dopaminergic); different actions based on dose given

DA → NE → EPI

Dopamine → Norepinephrine → Epinephrine ✅

This pathway is one of the most important things to remember for sympathetic nervous system questions.

The One Chart to Memorize 📝

Neurotransmission of Sympathetic Nervous System

Sympathetic Nervous System

🧠

⬇

ACh (at ganglion)

🚉 Ganglion

⬇

NE (at organ)

❤🫁💪

---

Hormone Pathway

🏭 Adrenal Medulla

⬇

Epinephrine (Adrenaline)

⬇

🩸 Bloodstream

⬇

❤🫁💪 Fight-or-Flight Response

Neurotransmitter	Easy Job	Where It Works
ACh	Carries message to ganglion	Preganglionic nerve
NE	Main fight-or-flight chemical	Postganglionic nerve
EPI	Adrenaline; boosts body response	Adrenal medulla → blood
DA	Precursor to NE	CNS & sympathetic system

Sympathetic Pathway

🧠/Spinal Cord

⬇

Preganglionic nerve

⬇ releases Acetylcholine (ACh)

🚉 Ganglion

⬇

Postganglionic nerve

⬇ releases Norepinephrine (NE)

❤🫁💪 Organ

Acetylcholine (ACh) vs Norepinephrine

Acetylcholine (ACh)

First Messenger 📩 What does it do?

ACh carries the message from the preganglionic nerve to the ganglion .

Important:

Both the sympathetic and parasympathetic systems use ACh at the ganglion.

Easy memory:

👉 ACh = At ​​the ganglion

Norepinephrine (NE) = Main Sympathetic Messenger ⚡ What does it do?

After the message reaches the ganglion:

The postganglionic nerve releases norepinephrine

NE then goes to the organ and creates the fight-or-flight response .

Effects:

❤ Heart rate increases

🫁 Breathing increases

👀 Pupils dilate

🍔 Digestion slows

Easy memory:

👉 NE = Nervous system's Emergency chemical

NE Comes from Dopamine

Your body makes NE like this:

Dopamine
⬇
Norepinephrine

Easy memory:

👉 DA → NE

(Dopamine becomes Norepinephrine)

Epinephrine (EPI)

Neurotransmission of Sympathetic Nervous System

…. = Adrenaline ⚡⚡ What is it?

Epinephrine is also called adrenaline .

Where is it made?

🏭 Adrenal medulla (part of the adrenal gland)

What does it do?

Travels through the blood and helps create the fight-or-flight response.

Effects:

❤ Faster heart rate

🫁 Faster breathing

💪 More energy

👀 Larger pupils

Easy memory:

👉 EPI = Emergency Power Increase

4. Dopamine (DA) 🧠

What is it?

A neurotransmitter found in:

🧠Central Nervous System (CNS)

⚡ Sympathetic Nervous System

---

Important Job

Dopamine is the precursor to norepinephrine.

Precursor means:

"Comes before"

Easy pathway:

Dopamine
⬇
Norepinephrine
⬇
Epinephrine

Easy memory:

👉 DA → NE → EPI

Dopamine Can Affect Different Receptors

Neurotransmission of Sympathetic Nervous System

Dopamine can stimulate:

• Alpha receptors

• Beta receptors

• Dopamine receptors

Why is this important?

Different doses of dopamine can cause different effects.

Think of dopamine as a multitool 🛠 that can do different jobs depending on how much is present.

Sympathetic Nervous System: Step-by-Step

Example:

You see a bear 🐻 and get scared.

Your body needs to activate the fight-or-flight response .

Step 1: Brain/Spinal Cord Detects Stress 🧠

Your brain realizes:

⚠ "Danger! We need to react!"

The message starts in the brain/spinal cord.

Step 2: Preganglionic Nerve Carries the Message

The message travels down the preganglionic nerve .

Think of this as the first messenger .

Step 3: Acetylcholine (ACh) Is Released 📩

When the message reaches the ganglion (relay station) :

The preganglionic nerve releases Acetylcholine (ACh) .

Why?

Because ACh helps pass the message to the next neuron.

Think: 🧠 → ACh → 🚉 Ganglion

Step 4: Postganglionic Nerve Receives the Message

The second neuron (postganglionic nerve) receives the message.

Now it must deliver the message to the organ.

Step 5: Norepinephrine (NE) Is Released ⚡

The postganglionic nerve releases Norepinephrine (NE) onto the target organ.

Why?

NE tells the organ: ⚡ "Emergency mode!"

For example: ❤ Heart beats faster, 🫁 Lungs work harder

👀 Pupils get bigger

Think: 🚉 Ganglion → NE → ❤ Organ

Neurotransmission of Sympathetic Nervous System

summary

Imagine you're walking in the woods and seeing a bear:

1. 🧠 Brain senses danger.

2. 🚶 Preganglionic nerve carries message.

3. 📩 ACh released at ganglion.

4. 🚶 Postganglionic nerve carries message.

5. ⚡ NE released at organs.

6. ❤ Heart speeds up, 🫁 breathing increases.

7. 🏭 Adrenal medulla releases epinephrine into blood.

8. ⚡ Whole body goes into fight-or-flight mode.

What You Really Need to Memorize Nerve Pathway

Brain → Preganglionic Nerve → ACh → Ganglion → Postganglionic Nerve → NE → Organ

Hormone Pathway

Adrenal Medulla → Epinephrine → Bloodstream → Organs

Chemical-Making Pathway

Dopamine → Norepinephrine → Epinephrine

Sympathetic Nerve Fibers

steps

Sympathetic = ACh → NE

Neuron 1 → Ganglion

• ACh Releases

• Binds Nicotinic (Nn) receptor

Neuron 2 → Organ

• Releases NE

• Binds Adrenergic receptor

Formula

Brain
⬇
Preganglionic neuron
(ACh)
⬇
Nicotinic (Nn) receptor in ganglion
⬇
Postganglionic neuron
(NE)
⬇
Adrenergic receptor on organ
⬇
Fight-or-flight response

Why is the first neuron short?

The ganglion sits close to the spinal cord.

SW:

• Short preganglionic neuron

• Long postganglionic neuron

This is a hallmark of the sympathetic nervous system .

Quick Quiz

1. What neurotransmitter is released at the ganglion?

   • ACh

2. What receptor is at the ganglion?

   • Nicotinic (Nn)

3. What neurotransmitter is released at the target organ?

   • NE

4. What receptor is on the target organ?

   • Adrenergic receptor

Shortcut for exams:

🟢 ACh → Nicotinic (Nn) → NE → Adrenergic

That's the entire pathway shown in the picture. 🎯

Sympathetic/Adrenergic Receptors

Receptor	Main Effect
α1 (Alpha 1)	SQUEEZE
α2 (Alpha 2)	STOP
β1 (Beta 1)	HEART 1 ❤
β2 (Beta 2)	LUNGS 2 🫁

When NE (norepinephrine) or EPI (epinephrine) is released, it attaches to different receptors.

1. Alpha 1 = SQUEEZE

Sympathetic/Adrenergic Receptors

📍 Found on:

• Blood vessels

• Eyes

• Smooth muscle

What's happening?

The muscles contract (squeeze) .

Results:

✅ Blood vessels constrict (get narrower)

✅ Blood pressure goes UP

✅ Pupils dilate (mydriasis)

Memory Trick

Alpha 1 = 1 word = SQUEEZE

Think:
👉 "Alpha 1 squeezes blood vessels."

α1 = Constrict = ↑ BP

2. Alpha 2 = STOP

Sympathetic/Adrenergic Receptors

📍 Found on nerve endings

What's happening?

Alpha 2 acts like a brake pedal.

It tells the body:

🛑 "Stop releasing so much norepinephrine."

Results:

✅ Less NE released

✅ Blood vessels relax

✅ Blood pressure decreases

Memory Trick

Alpha 2 = Auto Shutoff

Think:

A thermostat shuts itself off when things get too hot.

Alpha 2 does the same thing.

It says:

"Enough NE already!"

α2 = STOP = ↓ NE = ↓ BP

3. Beta 1 = HEART ❤

Sympathetic/Adrenergic Receptors

📍 Found mainly on the heart

What's happening?

It makes the heart work harder.

Results:

✅ Heart beats faster

✅ Heart beats stronger

✅ Electrical conduction increases

Memory Trick Beta 1 = 1 Heart ❤

One heart → Beta 1

β1 = Heart goes FAST and STRONG

Easy Phrase

Beta 1 = Beat 1 Heart

4. Beta 2 = LUNGS 🫁

Sympathetic/Adrenergic Receptors

🫁

📍 Found in:

• Lungs

• Uterus

• Skeletal muscle blood vessels

What's happening?

Causes relaxation.

Results:

✅ Bronchodilation (airways open)

✅ Blood vessels relax

✅ Uterus relaxes

Memory Trick Beta 2 = 2 Lungs 🫁🫁

You have 2 lungs.

Think:

β2 opens the airways.

Beta 2 = Breathe

Sympathetic/Adrenergic Receptors

side by side

Receptor	Think	Effect
α1	SQUEEZE	↑ BP, pupil dilation
α2	STOP	↓ NE, ↓ BP
β1	HEART ❤	↑ HR, ↑ contraction
β2	LUNGS 🫁	Bronchodilation, relaxation

α1 = Constrict α2 = Stop β1 = 1 Heart ❤ β2 = 2 Lungs 🫁🫁

A bear is chasing you 🐻

α1

Blood vessels squeeze
➡ BP goes up

β1

Heart beats faster and stronger
➡ More blood to muscles

β2

Lungs open wider
➡ More oxygen

α2

After things calm down
➡ Tells body to stop releasing extra NE

EPI and NE at Adrenergic Receptors

chart

Effects from Sympathetic Stimulation

side by side

Body Part	What Happens?	Why?
Adrenal gland	Releases epinephrine (adrenaline)	Boosts fight-or-flight
Arteries	Mostly constrict	Raises BP
Heart	Beats faster and stronger	Pumps more blood
Intestines	Slow down	Digestion isn't important during danger
Eyes	Pupils dilate	See better
Lungs	Airways open wider	Get more oxygen
Bladder	Relaxes	Holds urine
Urinary sphincter	Contracts	Prevents urination

Effects from Sympathetic Stimulation

adrenal Medulla vs Arteries

1. Adrenal Medulla What's happening?

Releases:

✅ Epinephrine (Adrenaline)

Think:

🚨 Danger → Adrenaline rush

This helps prepare the whole body for action.

2. Arteries What's happening?

Blood vessels constrict (squeeze).

Think:

🩸 Pipe gets smaller

➡Blood pressure increases

Why?

To send blood where it's needed most.

Exception:
Blood vessels going to:

• Heart ❤

• Skeletal muscles 💪

actually get wider (dilate) so they receive more blood.

Effects from Sympathetic Stimulation

Heart vs Intestines

3. Heart ❤ What's happening?

The heart:

✅ Beats faster

✅ Beats stronger ✅ Conducts electrical signals faster

Think:

🏃 Running from a bear

Your heart needs to pump lots of blood quickly.

Memory Trick

Sympathetic = Speed ​​Up the Heart

4. Intestines 🍔 What's happening?

Digestive activity decreases.

✅ Less movement

✅ Less secretion

Think:

If a bear is chasing you, your body says:

"Forget digesting lunch right now!"

Digestion slows down.

Eyes vs Lungs vs Urinary Bladder

5. Eyes 👀 What's happening?

Pupils dilate (get bigger).

Mydriasis = pupil dilation

Think:

👀 Bigger pupils = more light enters

➡ Better vision during danger

6. Lungs 🫁 What's happening?

Bronchodilation

Bronchi = airways

Dilation = open wider

Think: Airways get bigger

➡ More oxygen enters

➡ More oxygen to muscles

7. Urinary Bladder What's happening?

Bladder relaxes.

Think:

🫙 Relaxed bladder can hold more urine.

Your body doesn't want you stopping to pee during an emergency.

8. Urinary Sphincter What's happening?

Contracts (closes).

Think: 🚪 Door closes ➡ Urine stays in

Sympathetic Nervous System Turns On

❤ Heart beats faster

🫁 Lungs open wider

👀 Pupils get bigger

💪 More blood goes to muscles

🍔 Digestion slows

🚽 Bladder holds urine

⚡ Adrenaline is released

Everything is focused on:

SURVIVE AND RUN

Fight or Flight =

❤ Fast heart

🫁 Open lungs

👀 Big pupils

🍔 Stop digestion

🚽 Hold urine

⚡ Release adrenaline