BIO169 Unit 1: Endocrine and Cardiovascular System Study Guide

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Endocrine System

Sympathetic Nervous System and Adrenal Medulla

The sympathetic nervous system stimulates the adrenal medulla to release catecholamines (epinephrine and norepinephrine), which prolong the effects of sympathetic activation.

Adrenal medulla: Inner part of the adrenal gland; releases hormones in response to stress.
Lasting effects: Hormones released into the bloodstream act for longer periods than direct neural stimulation.
Example: Increased heart rate and blood pressure during stress.

Hormones: Definition and Types

A hormone is a chemical messenger secreted by endocrine glands, transported by the blood, and acting on distant target organs to regulate physiology and behavior.

Steroid hormones: Derived from cholesterol; lipid-soluble; act on intracellular receptors (e.g., cortisol, estrogen).
Non-steroid hormones: Include protein, peptide, and amino acid-derived hormones; water-soluble; act on cell surface receptors (e.g., insulin, epinephrine).

Anatomy of the Hypothalamus and Pituitary Gland

The hypothalamus is a brain region controlling the pituitary gland, which is divided into anterior (adenohypophysis) and posterior (neurohypophysis) lobes.

Hypothalamus: Produces releasing and inhibiting hormones.
Pituitary gland: Master endocrine gland; anterior lobe produces hormones, posterior lobe releases hypothalamic hormones.

Hormone Functions and Regulation

Each hormone has specific effects; changes in hormone levels can cause physiological or pathological outcomes.

Deficiency: May cause diseases like Addison's (low cortisol), hypothyroidism (low thyroid hormone).
Excess: May cause Cushing's (high cortisol), hyperthyroidism (Grave's disease).
Regulation: Negative feedback loops maintain homeostasis.

Hypothalamic-Pituitary-Endocrine Organ Relationship

The hypothalamus regulates the pituitary, which in turn controls other endocrine glands via a multi-tiered negative feedback system.

Multi-tier control: Hypothalamus → Pituitary → Endocrine gland → Target tissue.
Negative feedback: End product inhibits earlier steps.

Hormone Receptors: Upregulation and Downregulation

Target tissues respond to hormones by adjusting receptor numbers.

Upregulation: Increase in receptor number; enhances sensitivity (e.g., oxytocin during labor).
Downregulation: Decrease in receptor number; reduces sensitivity (common in negative feedback).

Cardiovascular System

Heart Anatomy and Blood Flow

The heart has four chambers: right atrium, right ventricle, left atrium, left ventricle. Blood flows through these chambers, separated by valves, driven by pressure gradients.

Valves: Tricuspid (right AV), pulmonary, mitral (left AV), aortic.
Oxygenation: Blood is oxygenated in the lungs, deoxygenated in systemic tissues.

Layers of the Heart Wall

Epicardium: Outer layer.
Myocardium: Middle, muscular layer.
Endocardium: Inner layer.

Action Potential Phases in Contractile Cardiomyocytes

Cardiac muscle cells undergo distinct phases during action potentials:

Phase 0: Rapid depolarization (Na+ influx).
Phase 1: Initial repolarization (K+ out).
Phase 2: Plateau (Ca2+ influx balances K+ out).
Phase 3: Repolarization (K+ out).
Phase 4: Resting potential.

Coronary Arteries

Right coronary artery and left coronary artery supply oxygenated blood to the heart muscle.

Phases of the Cardiac Cycle

Ventricular filling: Blood flows into ventricles.
Isovolumetric contraction: Ventricles contract, all valves closed.
Ventricular ejection: Blood pumped out of ventricles.
Isovolumetric relaxation: Ventricles relax, all valves closed.

Cardiac Equations

Cardiac Output (CO):
Stroke Volume (SV):
Pulse Pressure (PP):
Mean Arterial Pressure (MAP):

Conductance Pathway and Pacemaker

SA node: Pacemaker; initiates impulse.
AV node: Delays impulse.
Bundle of His, bundle branches, Purkinje fibers: Conduct impulse through ventricles.

ECG Waves

P wave: Atrial depolarization.
QRS complex: Ventricular depolarization.
T wave: Ventricular repolarization.

Heart Sounds

S1: Closure of AV valves.
S2: Closure of semilunar valves.

Heart Adaptations with Training

Increased stroke volume and cardiac efficiency.
Lower resting heart rate in trained individuals.

Blood Vessel Layers and Functions

Tunica intima: Inner layer; smooth lining.
Tunica media: Middle layer; smooth muscle for vasoconstriction/dilation.
Tunica externa: Outer layer; connective tissue for support.

Blood Pressure and Peripheral Resistance

Blood pressure: Force exerted by blood on vessel walls.
Peripheral resistance: Resistance to blood flow; affected by vessel diameter, blood viscosity, and vessel length.

Capillary Types and Functions

Continuous: Tight junctions; found in muscle, skin.
Fenestrated: Pores; found in kidneys, intestines.
Sinusoidal: Large gaps; found in liver, spleen.

Renin-Angiotensin-Aldosterone System (RAAS)

Regulates blood pressure and fluid balance.

Renin: Released by kidneys; converts angiotensinogen to angiotensin I.
Angiotensin II: Vasoconstrictor; stimulates aldosterone release.
Aldosterone: Increases sodium and water reabsorption.

Receptors: Baroreceptors and Chemoreceptors

Baroreceptors: Detect pressure changes; found in carotid sinus, aortic arch.
Chemoreceptors: Detect chemical changes; found in carotid and aortic bodies.

Water Flow Across Capillary Beds

Water movement is governed by hydrostatic and colloid osmotic pressures.

Hydrostatic pressure: Pushes fluid out of capillaries.
Colloid osmotic pressure: Pulls fluid into capillaries.
Net flow: Typically out at arterial end, in at venous end.

Arterial and Venous Pathways

Arteries: Branch from aorta to supply body regions.
Veins: Drain blood from tissues, combine into larger veins, return to vena cavae.

Systemic Circuit Blood Flow

Pathway: Aorta → arteries → arterioles → capillaries → venules → veins → vena cavae.
Pressure: Highest in arteries, lowest in veins.

Sympathetic Nervous System and Vessel Constriction

Sympathetic control: Governs most blood vessel constriction.

Relative Pressure in Vessels

Vessel Type	Relative Pressure
Arteries	High
Capillaries	Medium
Veins	Low

Additional info: Academic context and definitions were added to expand brief study guide points into full explanations.