Human Anatomy and Physiology

Alex HarutunianGabriel Alpuerto

Cameron Wheeler

Organ Systems in Humans● Digestive

● Respiratory

● Circulatory

● Endocrine

● Excretory

● Nervous

● Muscular

Digestive System

Digestive System● 2 important functions:

○ digestion- breaking down large molecules○ absorption- diffusion of smaller molecules

● digestive tract is 30 ft. of smooth muscle● peristalsis- process of pushing food along

digestive tract● digestive organs:

○ mouth○ esophagus○ stomach○ small intestine○ large intestine

Mouth and Esophagus● Mouth- tongue and teeth break down food mechanically

○ Omnivores- plants and animals○ 3 types of teeth:

■ incisors- cutting■ canines- tearing■ molars- grinding

○ Salivary amylase- enzyme■ begins chemical breakdown of starch

● Esophagus- tube which leads to stomach○ epiglottis- cartilage in back pharynx (throat)

■ directs food into esophagus

Stomach● secrets gastric juices and begins digestions of

proteins

● stomach lining contains gastric pits

○ Chief cells- secrete pepsinogen

○ Parietal cells- secrete hydrochloric acid

○ Mucous cells- secrete mucus and protect

stomach lining

● lower esophageal sphincter

● pyloric sphincter

Small Intestine● digestion completed in duodenum● bile- produced in liver & stored in gallbladder● released into small intestine and act as an emulsifier● lower small intestine = site of absorption● villi- fingerlike structures, line small intestine

○ absorb nutrients released from digested food○ contain capillaries which absorb amino acids, vitamins, and

monosaccharides○ contain lacteal- small vessel of lymphatic system, absorbs fatty acids

and glycerol● microvilli- microscopic cytoplasmic appendages; increase SA = increase

nutrient absorption

Large Intestine● aka colon● 3 main functions:

○ egestion- removal of undigested waste○ vitamin production○ removal of excess waste

● small and large intestines re-absorb 90% of water leaving body○ too much water removed = constipation○ too much water released = diarrhea

● rectum- last 7-8 inches of GI tract● anus- opening at end of GI tract

Regulation of Digestive System● Gastrin

○ stomach wall○ simulates gastric juice

● Secretin○ doudenum wall○ stimulates pancreas to release

bicarbonate● Cholecystokinin (CCK)

○ doudenum wall○ stimulates pancreas to release

pancreatic enzymes and gallbladder to release bile

Respiratory System

Respiratory System● Path of Air

○ Nasal cavity○ Larynx○ Trachea○ Bronchi (Bronchioles)

● Internal Respiratory Surface○ Diaphragm contracts and lowers○ Negative Pressure draws air into lungs

● Medulla (in brain)○ Control Center for Respiration○ sets breathing rhythm○ monitors CO2 levels

■ CO2 becomes carbonic acid

Respiratory Structures● Nasal Cavity- air is moistened, warmed, and filtered

● Epiglottis- opens up so that air can go into trachea

● Larynx- voice box; protects lungs from foreign objects (cough)

● Trachea- tube which leads air to lungs (windpipe)

● Diaphragm- contracts and lowers to draw air into lungs

● Lungs- two main respiratory structures

● Medulla- sets breathing rate, monitors CO2 levels via pH of blood

○ CO2 becomes carbonic acid

○ blood below pH 7.4 = increased rate of breathing

Lungs● Main Respiratory structures

● Expand due to negative pressure from diaphragm

● Breakup of Lungs

○ Bronchi- smaller air tunnels in

lungs

○ Bronchioles- tiniest and thinnest

parts of bronchi

○ Alveoli- microscopic air sacs;

where diffusion of gases occurs

Hemoglobin● Carries Oxygen through the blood● combines with 4 oxygens to make oxyhemoglobin● allosteric molecule

○ cooperativity: once one O2 binds, molecule changes shape and other O2’s bind more easily

● pH sensitive○ drop in blood pH (more CO2) =

lower affinity of hemoglobin to O2○ actively respiring cells release

more CO2 = lower pH in those regions → hemoglobin releases O2 near cells which need it

Transport of CO2● Little CO2 is carried by hemoglobin

● Majority is carried in plasma of blood

● part of reversible blood buffering carbonic

acid-bicarbonate ion system

○ maintains blood at constant 7.4 pH

○ produced in 2 step reaction

CO2 + H2O → H2CO3 → H2CO3- + H-

Circulatory System

Circulatory System● Closed Circulatory System

○ arteries○ veins○ capillaries

● Bone Marrow:○ develops red and white BC and

platelets○ multipotent stem cells○ stem cells keep dividing

constantly to replenish population of blood cells

● Plasma○ liquid portion of blood;

contains clotting factors, hormones, antibodies, dissolved gases, nutrients, and wastes; maintains proper osmotic potential of blood (300 mosm/l=L)

● Red Blood Cells(Erythrocytes)○ carry hemoglobin and

oxygen; no nucleus formed in marrow; recycled in liver

● White Blood Cells(Leukocytes)○ fight infections; produce

antibodies (b lymphocyte); formed in marrow

● Platelets(Thrombocytes)○ not cells...cell fragments; clot

blood; formed in marrow

Blood

Blood Clotting● Complex mechanism● Begins with release of clotting factors (from platelets and damaged tissue)● Inactive plasma proteins become active● Anticlotting factors circulate in blood to prevent thrombus from forming

Damaged Tissue and Platelets

Thromboplastin + Ca2+

Prothrombin (inactive) Thrombin (active)

Fibrinogen (inactive) Fibrin (Clot) (Active)

Blood Vessels● Artery and Arteriole

○ carry blood from the heart○ made of thick, elastic, and smooth

muscle● Vein and Venule

○ carry blood to the heart○ thin walls with valves○ located within skeletal muscle

● Capillary○ diffusion of nutrients and wastes

between cells and blood○ one-cell thick

Heart● Pumps blood throughout body

● Two Atria- receive blood from body

● Two Ventricles- pump blood out of heart

● Cardiac muscle cells

● Pacemaker- sinoatrial (SA) node

● Blood pressure

○ lowest in veins, highest in arteries

○ systolic- ventricles contract

○ diastolic- heart relaxes

Sinoatrial Node● Pacemaker of heart● Located in wall of right atrium● Generates and sends electrical signals to atrioventricular node● Action potential generated by voltage-gated Ca2+ channels● Impulses sent to His and Purkinje bundle fibers

○ trigger ventricles to contract● Influenced by variety of factors

○ 2 sets of nerves■ speed up or slow down

○ hormones (adrenalin)○ body temperature

Pathway of Blood● Vena Cavae● Right atrium● Right atrioventricular valve--tricuspid● Right ventricle● Pulmonary semilunar valve● Pulmonary artery● Lungs● Pulmonary vein● Left atrium● Left atrioventricular valve--bicuspid● Left ventricle● Aortic semilunar valve● Aorta● Systemic Circuit

Mini-Circulatory Systems● Coronary circulation (Heart)

● Renal Circulation (Kidney)

● Hepatic Circulation (Liver)

● Pulmonary Circulation (Lungs)

Endocrine System

Endocrine System● Simple Endocrine Pathways

○ Environmental stimulus

● Neuroendocrine Pathways

○ Hypothalamus (the Bridge)

○ Posterior Pituitary

○ Anterior Pituitary

● Feedback Regulation in Endocrine Pathways

○ Negative Feedback

○ Positive Feedback

Endocrine cont.● Multiple Effect of Hormones

○ Example

■ Epinephrine

● Glucose in the blood

● Increased blood flow to the muscles

● decreased blood flow to digestion

Excretory System

Excretory System● Removal of metabolic wastes from respiration● Removal of nitrogenous wastes from protein

metabolism● Structures:

○ Skin○ Lungs○ Liver- urea produced○ Large Intestine○ Kidney

● 3 nitrogenous wastes:○ Ammonia○ Urea○ Uric acid

Nitrogenous Wastes1. Ammonia

a. Very soluble in waterb. Generally from water organisms

2. Ureaa. Not as toxic as ammoniab. Excreted by earthworms and humansc. Formed in liver from ammonia (mammals)

3. Uric acida. Pastelike substance; not soluble in waterb. Not very toxicc. Excreted by insects, reptiles, and birdsd. Minimum water loss

Excretory Structures● Skin (minimal role)

○ Sweat Glands○ Perspiration

● Lungs○ Removal of CO2

● Liver○ Detoxifies our bodies○ Ammonia → Urea○ Produces Bile

■ Helps break down fats● Large Intestine

○ Transports wastes to be excreted○ Extracts usable water

Kidney● 2 functions: osmoregulator and

excretory organ● Supplied blood from renal artery and

vein● Humans need minimal water loss● Kidney balances water conservation

and poison excretion● Produces large volume of dilute urine● When salt intake is high, produces

concentrated urine

Nephron● Functional unit of the kidney● Structures:

○ Bowman's capsule■ Glomerulus

○ Renal tubule■ Loop of Henle

○ Collecting Duct● 4 steps of Nephron's job:

○ Filtration○ Secretion○ Reabsorption○ Excretion

Filtration & Secretion● Filtration

○ Blood pressure forces fluid from blood into glomerulus○ Podocytes (specialized Bowman's capsule cells) and slit pores

increase rate of filtration○ Filtration = diffusion; is passive and nonselective○ Filtrate travels into proximal tubule

● Secretion○ Occurs in proximal and distal tubules○ Secretion = active and selective uptake of drugs and toxins○ Picks up what bowman's capsule didn't filter○ Proximal tubule also secretes ammonia

Reabsorption & Excretion● Reabsorption

○ Reabsorbs water and solutes which initially entered tubule○ Transported back into peritubular capillaries○ Proximal convoluted tubule → loop of Henle → collecting tubule○ Loop Henle acts as a countercurrent exchange mechanism○ Longer loop of Henle = more water reabsorbed

● Excretion○ Everything passing through collecting tubule is excreted○ Urine passage:

■ Collecting tubule■ Ureter■ Urinary bladder■ Urethra

Regulation of Kidneys● 3 hormones control the kidney

● Osmolality Regulation

○ Antidiuretic hormone- response to

dehydration

● Blood Pressure Regulation

○ Aldosterone- response to

decrease in blood pressure

○ Renin- converts inactive proteins

into active angiotensin

Nervous System

Nervous System● The Central Nervous System (CNS)

○ brain ○ spinal cord

● The Peripheral Nervous System (PNS)○ all nerves outside CNS○ Sensory System

■ conveys info from sensory receptors or nerve endings

○ Motor System■ Somatic system- controls voluntary

muscles■ Autonomic system- controls

involuntary muscles

Sympathetic System

● Fight or Flight response● Increase heart and breathing rate● Liver converts glycogen to

glucose● Bronchi dilate and increase gas

exchange● Adrenalin raises blood glucose

levels

Parasympathetic System

● Opposes the sympathetic

system

● Calms the body

● Decrease heart/breathing rate

● Enhances digestion

Autonomic System

Neuron● Basic unit of Nervous System● Structures:

○ Cell body (with nucleus)○ Cytoplasmic extensions

■ Dendrites■ Axons

● 3 types of neurons:○ Sensory neuron- receive initial stimulus (from sense organ or another

neuron)○ Motor neuron- stimulates effectors (muscles or glands)○ Interneuron- resides in spinal cord and brain; receives sensory stimuli

and transfers info to brain or a motor neuron

Dendrites and AxonsThe two types of cytoplasmic extensions● Dendrites (sensory)

○ receive messages from other cells and carry the electrical signal to the cell body

○ a neuron can have multiple dendrites

● Axons○ transmit the impulse from the

cell body to other cells○ wrapped in a fatty myelin sheath○ only one axon per neuron

The Reflex Arc● the simplest nervous response

● inborn, automatic, and protective

● Can involve two or three types of neurons

○ two types (Sensory and motor)

■ Example: Knee-jerk reflex

○ three types(sensory,motor,interneuron)

■ Example: Pulling the hand away

from sharp or hot objects

Resting Potential● membrane potential

○ the difference in electrical charge between the cytoplasm (negative)

and the extracellular fluid(positive)

○ between -50 mV and -100 mV

○ resting potential (the polarized state) is about -70 mV

● Sodium-potassium pumps maintain polarization

● To transmit an impulse a stimulus must overcome the resting potential

Gated Channels● open and close in response to a stimulus

● Sodium ion channel

○ when open, sodium flows into the cytoplasm

○ decreases the polarization to -60mV (membrane is depolarized)

○ easier for nerve to fire

● Potassium ion-gated channel

○ when open potassium flows into the cytoplasm

○ increases polarization to -75mV (membrane is hyperpolarized)

○ harder for nerve to fire

Action Potential● only generated in the axon● an all or nothing event

○ Sodium channels open to allow sodium ions into the cell

○ Potassium channels open to allow potassium ions out of the cell

● creates a wave of depolarization (action potential)

● sodium-potassium pumps restore original polarity (refractory period)○ ensures an impulse only moves in

one direction along the axon● strong stimulus=more action potentials

The Synapse● the chemical part of impulse travel● Presynaptic neuron

○ cytoplasm contains many vesicles○ vesicles contain thousands of neurotransmitters○ depolarization causes the rush of Ca++ ions ○ stimulates vesicles to fuse with membrane and

release neurotransmitters through exocytosis● Postsynaptic side

○ receptors bond with neurotransmitters○ inhibitory or excitatory○ esterase destroys neurotransmitters to recycle

them

Organization of the Human Brain● Cerebrum

○ learning, emotion, memory, perception○ right and left hemispheres○ left side interacts with the right ride of the body and vice versa

● Cerebellum○ movement and balance; motor skills○ sensory information on joints and muscles○ monitor and integrates motor commands from cerebrum

● Brainstem (including medulla oblongata)○ automatic homeostatic functions○ receives and integrates sensory information○ transfers information between PNS and brain

The Human Eye● The Lens

○ focuses the light● The Retina

○ Rods (black and white vision)○ cones (colored vision)○ retinal (cis->trans)○ rhodopsin

● Signal transduction pathway (conversion of a stimulus into a cellular response

● amplification cascade (increase in the signal as it is relayed)● G-protein-signaling mechanism

○ closes Na+ channels

Muscular System

Muscular System● 3 types of muscle

○ smooth (involuntary)- make up blood vessels and digestive tract; no striated appearance

○ cardiac- heart muscle; generates its own action potential

○ skeletal (voluntary)- very large and multinucleate; work in pairs--one muscle contracts as the other relaxes

Muscle Composition● bundles of thousands of muscle fibers● each fiber is an individual cylindrical muscle cell● each cell is large and multinucleate● skeletal muscle modified structures:

○ sarcolemma- modified plasma membrane; surrounds each muscle fiber and can propagate action potential

○ sarcoplasmic reticulum (SR)- modified endoplasmic reticulum; contains sacs of Ca++ for muscle contraction

○ T system- system of tubules; runs perpendicular to SR; connects SR to extracellular fluid

○ sarcomere- functional unit of muscle fiber; bounded by Z lines

Sliding Filament Theory● myofibrils

○ in cytoplasm of muscle cells○ fun parallel to length of cell○ consists of thick and thin filaments

■ thin- each thin filament has 2 strands of actin proteins■ thick- each thick filament composed of 2 long chains of myosin

● sarcomere contraction○ troponin○ tropomyosin○ Ca++ ions- needed to form and break cross-bridges

● Muscle contracts as thick and thin filaments slide over each other

Neuromuscular Junctionthe synapse of the motor neuron on a skeletal muscle● acetylcholine

○ binds receptors of the sarcolemma○ depolarizes the muscle cell membrane○ sets up an action potential

● The action potential○ moves along the sarcolemma into the T system○ stimulates the sarcoplasmic reticulum to release Ca++

● Ca++ ions○ troponin-tropomyosin relationship○ muscle contracts

Summation and Tetanus● one action potential

○ twitch

● overlapping action potentials

○ the summation effect

● High enough rate of stimulation

○ Tetanus(not the disease)