Physio exam 2

Endocrine System

Uses hormones in blood for slow, long-lasting regulation

Hormones

Endocrine vs Nervous

Endocrine = slow/long; Nervous = fast/short

Functions of Endocrine System

Metabolism, growth, reproduction, stress, fluid balance

Endocrine Glands

Made of ductless secretory epithelial cells

Bloodstream Role

Transports hormones to target tissues

Endocrine

Long-distance (blood)

Paracrine

Local cells

Autocrine

Self-target

Negative Feedback

Maintains stability (most common

Positive Feedback

Amplifies process (ex: labor)

Amine

Fast or slow (depends on solubility)

Peptide/Protein

Fast, membrane receptors

Steroid

Slow, affects gene expression

Hypothalamus Role

Controls pituitary via nervous system

Releasing Hormones (RH)

Stimulate anterior pituitary

• CRH → ACTH

• GHRH → GH

Anterior Pituitary (Indirect)

→ Hypothalamus → portal system → hormones → target

Posterior Pituitary (Direct)

→ Hypothalamus makes hormones → stored → released

Anterior Pituitary Hormones; ACTH

Cortisol (stress)

Anterior Pituitary Hormones; TSH

Thyroid hormones (metabolism)

Anterior Pituitary Hormones; GH

Growth + fat breakdown

Anterior Pituitary Hormones; LH

Ovulation/testosterone

Anterior Pituitary Hormones; FSH

Egg + sperm production

Anterior Pituitary Hormones; Prolactin

Milk production

Posterior Pituitary Hormones; Oxytocin

Contractions + milk ejection

Posterior Pituitary Hormones; ADH

Water retention + ↑ BP

Posterior Pituitary Hormones; Supraoptic nucleus

ADH

Posterior Pituitary Hormones; Paraventricular nucleus

Oxytocin

Growth Hormone (HIGH-YIELD); GH

Growth + metabolism

Growth Hormone (HIGH-YIELD); IGF-1

Causes actual tissue growth

Growth Hormone (HIGH-YIELD); Lipolysis

Fat breakdown

Growth Hormone (HIGH-YIELD); Hypertrophy

Muscle growth

Growth Hormone (HIGH-YIELD); Osteoblasts

Build bone

Growth Hormone (HIGH-YIELD); Ghrelin

Increases hunger + GH

Hyperthyroidism

Fast metabolism

Hypothyroidism

Slow metabolism

Muscle Types; Skeletal

Voluntary, bones

Muscle Types; Cardiac

Involuntary, heart

Muscle Types; Smooth

Involuntary, organs

Skeletal Triggers

Motor neuron (ACh)

Cardiac Triggers

SA node (pacemaker)

Smooth Triggers

Hormones, nerves, stretch

Skeletal Calcium Source

SR only

Cardiac Calcium Source

SR + extracellular

Smooth Calcium Source

Mostly extracellular

Troponin

Skeletal + cardiac

Calmodulin

Smooth

Skeletal Muscle Steps

ACh → depolarization → T-tubules → DHP → RyR1 → Ca²⁺ release → troponin → cross-bridge → contraction → ATP resets → SERCA relaxes

Mechanical Coupling

DHP opens RyR1

AChE

Breaks down ACh → stops signal

Cardiac Muscle; SA Node

Starts heartbeat

Cardiac Muscle; Gap Junctions

Spread signal

Cardiac Muscle; CICR

Ca²⁺ entry triggers more Ca²⁺

Cardiac Muscle; NCX

Removes Ca²⁺

Smooth Muscle; Calmodulin + MLCK

Start contraction

Smooth Muscle; MLCP

Stops contraction

Smooth Muscle; Low SR

relies on extracellular Ca²⁺

Latch Mechanism

Maintains contraction with low ATP (important for BP/organs)

Circulatory System

Transports O₂, nutrients, hormones, waste

Heart

Pump

Vessels

Pathways

Blood

Transport fluid

Pulmonary Circuits

Heart ↔ lungs (gas exchange)

Systemic Circuits

Heart ↔ body (delivery + waste)

Vessels; Arteries

Away from heart, high pressure

Vessels; Veins

Toward heart, low pressure, valves

Vessels; Capillaries

Exchange (one-cell thick)

Pressure & Velocity; Arteries

High pressure, fast

Pressure & Velocity; Capillaries

Low pressure, slowest

Pressure & Velocity; Veins

Low pressure, moderate

Capillaries Function

Exchange gases/nutrients

Capillaries Types

• Continuous → tight

• Fenestrated → pores

• Sinusoidal → large gaps

Arterioles Resistance

Control BP (vasoconstrict/dilate)

Blood Distribution; Veins

Store most blood (~60–70%)

Venous Return; Valves

Prevent backflow

Venous Return; Muscle pump

Push blood

Venous Return; Pressure gradient

Pulls blood to heart

Baroreceptors (HIGH-YIELD); Location

Carotid sinus + aortic arch

Baroreceptors (HIGH-YIELD); Function

Detect BP

Baroreceptors (HIGH-YIELD); High BP

↓ HR + vasodilation

Baroreceptors (HIGH-YIELD); Low BP

↑ HR + vasoconstriction

Electrical Conduction (ORDER!!)

SA → AV → Bundle of His → Bundle branches → Purkinje → ventricles contract

Electrical Conduction; AV Delay

Allows filling

ECG; P wave

Atrial contraction

ECG; QRS

Ventricular contraction

ECG; T wave

Ventricular relaxation

Cardiac Cycle; Systole

Contraction

Cardiac Cycle; Diastole

Relaxation

Ventricular Filling (Diastole)

AV open, SL closed, Blood flows passively from the atria into the ventricles, The ventricles are relaxed and filling up.

Atrial Contraction (End of Diastole)

AV Valves: Open (AV = O), Semilunar Valves: Closed (SL = C), The atria contract, pushing the remaining blood into the ventricles to top them off before contraction, This completes ventricular filling.

Isovolumetric Contraction (Start of Systole)

AV Valves: Closed (AV = C), Semilunar Valves: Closed (SL = C), S1 "Lub" sound occurs here as the AV valves close, Ventricles begin to contract, creating tension and pressure; this is the brief moment when the heart muscle stretches but no valves are open yet, Because all valves are closed, no blood enters or exits, so the volume stays the same.

Ventricular Ejection (Mid to Late Systole)

AV Valves: Closed (AV = C), Semilunar Valves: Open (SL = O), Ventricular pressure exceeds arterial pressure, causing the semilunar valves to open and blood is ejected into the aorta and pulmonary arteries.

Isovolumetric Relaxation (Start of Diastole)

AV Valves: Closed (AV = C), Semilunar Valves: Closed (SL = C), S2 "Dub" sound occurs here when semilunar valves close., Ventricles relax but haven't started filling yet ; all valves are shut briefly.

S2[“Dub”]

Closure of semilunar valves

S1[“Dub”]

Closure of AV valves

Autonomic Control; Sympathetic

↑ HR + ↑ force

Autonomic Control; Parasympathetic (Vagus)

↓ HR

Target cell

Cell with specific receptor for a hormone