Anatomy and Physiology

• consists of a group of glands that produce hormones
• works with nervous system to control and coordinate all other body systems
• affects body systems by chemical stimuli

• chemical messengers with regulatory effects on cells or organs
• released directly into tissue fluids, not through ducts

• two types: amino acid compounds and lipids
• amino acid compounds:
• -proteins or related compounds
• -all hormones except steroids
• lipids:
• -made of fatty acids
• -most are steroids, derived from cholesterol
• -produced in adrenal cortex and sex glands
• -prostaglandins are also lipids

• negative feedback: endocrine gland oversecretes hormone, tissue becomes too active, tissue negatively effects gland to decrease secretion
• positive feedback: hormone response produces more hormone

negative feedback control of hormones

• brain
• kidney
• adipose
• stomach
• small intestine
• atria of heart
• placenta

the endocrine glands

• master gland
• releases hormones that affect working of other glands
• controlled by hypothalamus

the hypothalamus, pituitary gland, and target tissues. Arrows indicate the hormones' target tissues and feedback pathways

• sends releasing hormones (RH) and inhibiting hormones (IH)
• -> hormones stimulate and suppress anterior pituitary secretions
• produces antidiuretic hormone (ADH) and oxytocin
• -> stored in posterior pituitary
• -> nerve impulses stimulate secretions

• growth hormone (GH) or somatropic
• thyroid-stimulating hormone (TSH) or thyrotropic
• adrenocorticotropic hormone
• prolactin (PRL)
• gonadotropins
• -> follicle-stimulating hormone (FSH)
• -> luteinizing hormone (LH)

• antidiuretic hormone (ADH)
• oxytocin

• largest endocrine gland
• lateral lobes on either side of larynx
• connecting band (isthmus)
• enclosed by connective tissue capsule

thyroid gland (anterior view)

• thyroxine (T4)
• -> principle hormone; increases energy and protein metabolism rate
• triiodothyronine (T3)
• -> increases energy and protein metabolism rate
• calcitonin
• -> regulates calcium metabolism; works with parathyroid hormone and vitamin D

• four glands in posterior capsule of thyroid
• secrete parathyroid hormone (PTH) -> works with calcitonin to regulate calcium metabolism

parathyroid glands (anterior view)

• calcitrol (dihydroxycholecalciferol) -> produced by modifying vitamin D in liver then in kidney
• parathyroid hormone
• calcitonin

• two small glands on top of kidneys
• each gland has two parts that act as separate glands -> medulla; cortex

the adrenal gland

fight-or-flight hormones: epinephrine(adrenaline); norepinephrine(noradrenaline)

• glucocorticoids - cortisol or hydrocortisone
• mineralocorticoids - aldesterone
• sex hormones

• Islets of Langerhans are specialized pancreas cells that secrete:
• insulin - lowers blood sugar level; stimulates manufacture of amino acids into protein
• glucagon - increases blood sugar

microscopic view of pancreatic cells

ovaries and testes produce hormones to: develop sexual characteristics; maintain reproductive organs

• male sex hormone - testosterone
• female sex hormones - estrogen, progesterone

• mass of lymphoid tissue in upper chest superior to heart
• important in development of immunity
• produces thymosin -> assists in maturity of T lymphocytes

• cone-shaped structure posterior to midbrain
• produces melatonin -> influences sleep-wake cycles; appears to delay onset of puberty

• group of hormones made by most body tissues
• produced, act, and rapidly inactivated in or close to origin
• constrict structures
• dilate structures
• promote inflammation or reduce inflammation

• growth hormone
• insulin
• adrenal steroids
• epinephrine (adrenaline)
• thyroid hormones
• oxytocin
• androgens
• estrogen and progesterone

• stress response involves both nervous and endocrine system
• hormones released during stress help body cope
• unchecked levels of hormones can harm body

• pancreas - adult-onset diabetes mellitus
• thyroid - decreased hormone secretion
• pituitary - decreased gonadotropic hormones; decreased growth hormone
• gonads - decreased sexual activity; loss of bone mass

• between the lungs
• left of the midline of the body
• in mediastinum
• apex pointed toward left

the heart in position in the thorax (anterior view)

lines the heart's interior - innermost layer of the heart wall

the thickest layer of the heart wall; heart muscle

thin outermost layer of the heart wall

sac that encloses heart; made up of fibrous pericardium and serous membrane

• outermost and heaviest layer of the pericardium
• connective tissue anchors the heart sac to diaphragm, sternum, and other structures to hold it in place

• lines the fibrous pericardium
• parietal layer: outer layer
• pericardial cavity: region between parietal and visceral layer, thin film of liquid reduces friction
• visceral layer (epicardium): thin, outermost layer of heart wall

layers of the heart wall and pericardium

• are lightly striated (striped)
• have single nucleus cells
• are controlled involuntarily
• have intercalated disks
• have branching muscle fibers

cardiac muscle tissue viewed under the microscope (x540)

• right side pumps blood low in oxygen to the lungs (pulmonary circuit)
• left side pumps oxygenated blood to remainder of body (systemic circuit)

• right atrium - receives low-oxygen blood returning from body tissue thorugh superior vena cava and inferior vena cava
• left atrium - receives high-oxygen blood from lungs
• right ventricle - pumps blood from right atrium to lungs
• left ventricle - pumps oxygenated blood to body

• entrance valves
• right atrioventricular (AV) valve (tricuspid valve)
• left atrioventricular (AV) valve (bicuspid valve)

• exit valves
• pulmonary valve
• aortic valve

valves of the heart (superior view from anterior, atria removed)

pathway of blood through the heart

• coronary circulation:
• right coronary artery
• left coronary artery
• coronary sinus

blood vessels that supply the myocardium. Coronary arteries and cardiac veins are shown

opening of coronary arteries in the aortic valve (anterior view). (A) When the left ventricle contracts, the aortic valve opens. The valve cusps prevent filling of the coronary arteries. (B) When the left ventricle relaxes, backflow of blood closes the aortic valve and the coronary arteries fill

• systole - active phase, contraction
• diastole - resting phase

the cardiac cycle

• cardiac output = CO
• stroke volume = SV
• heart rate = HR
• CO = HR (subscript 3) SV

• nodes: sinoatrial (SA) node (pacemaker); atrioventricular (AV) node
• specialized fibers: atrioventricular bundle (bundle of His); Purkinje fibers (conduction myofibers)
• intercalated disks

• 1. sinoatrial (SA) node
• 2. atria
• 3. atrioventricular (AV) node
• 4. internodal pathways
• 5. bundle of His
• 6. bundle branches and Purkinje fibers
• 7. ventricles

conduction system of the heart. The sinoatrial (SA) node, the atrioventricular (AV) node, and specialized fibers conduct the electrical energy that stimulates the heart muscle to contract

• autonomic nervous system
• sympathetic nervous system
• parasympathetic system (cranial nerve X)

autonomic nervous system regulation of the heart

slower heart rate than normal; less than 60 beats/minute

faster heart rate than normal; more than 100 beats/minute

changes in heart rate related to breathing rate changes

extra beat in the heart beat

• heart shrinks
• decreased contraction strength
• valves become less flexible
• murmur develops
• cardiac output decreases
• abnormal rhythms
• heart block