bio final exam

The sclera and cornea

The sclera and cornea

protect the eye

The pupil is an

opening that allows light to get inside

The iris is a

muscle that changes the size of the pupil

The lens is a

transparent flexible structure

The vitreous body is the

the clear gel that fills the space between the lens and the retina of the eyeball

The retina is the

layer at the back of the eye containing photoreceptors

The macula is the

region of the retina with the highest concentration of photoreceptors

How is light concerted to an action potential?

Activated photoreceptors release neurotransmitters to bipolar cells (neuron), which in turn synapses to another type of neurons called ganglion cells. The signal goes to the optic nerve which is then communicated to the visual cortex

The two types of photoreceptors located in the retina are

rods and cones

Photopigments are

light sensitive proteins which change shape when exposed to light and control how many neurotransmitters a photoreceptor releases

The photopigments in rods are specialized for

dim light

Cones provide

color vision

How many different types of cones are there in humans and what do they detect?

3 different cones that detect red, green, and blue light

Why do multicellular organisms need a circulatory system?

They can’t use diffusion to cycle waste, nutrients, and gases through the body because they have a larger surface area to volume ratio

In an open circulatory system

the blood is not enclosed in the blood vessels but is pumped into a cavity called a hemocoel and is called hemolymph because the blood mixes with the interstitial fluid

In an open circulatory system hemolymph circulates around the organs within the

body cavity and then reenters the heart through openings called ostia. This movement allows for gas and nutrient exchange.

An open circulatory system does not

 use as much energy as a closed system to operate or to maintain; however, there is a trade-off with the amount of blood that can be moved to metabolically active organs and tissues that require high levels of oxygen

In a closed circulatory system

blood is contained inside blood vessels and circulates unidirectionally from the heart around the systemic circulatory route, then returns to the heart again

The circulatory system is an organ system composed of

the heart (pump), blood vessels, and blood

The circulatory system is

an extensive network that supplies the cells, tissues, and organs with oxygen and nutrients, and removes carbon dioxide and waste, which are byproducts of respiration

Blood is a

specialized type of connective tissue composed of plasma and cellular components

Plasma

water, electrolytes (ions), proteins, hormones, nutrients, gases and wastes

Cellular components

red blood cells (RBCs), white blood cells (WBCs), and platelets

blood components can be separated by

hematocrit (centrifugation)

A hematocrit test measures the

proportion of red blood cells

Red blood cells are also called

erythrocytes

Red blood cells transport

oxygen and carbon dioxide

Red blood cells have no _________ and lack most __________

nucleus, organelles

RBCs are packed with

hemoglobin—-a protein which transports oxygen and some carbon dioxide

RBC production is controlled by a

hormone called erythropoietin (EPO)

The negative feedback loop that controls RBC production

• Special cells in the kidney monitor oxygen availability

• If oxygen levels are low these cells secrete EPO

• EPO stimulates the maturation of RBC

• Increase in RBC leads to an increase in oxygen availability, which in turn stops EPO production

Platelets are essential for

blood clotting

Platelets are formed from

megakaryocytes breaking in fragments

The three stages of hemostasis

vascular spasm, platelet plug formation, and coagulation

Vascular spasm

constriction of blood vessels to reduce blood flow

Platelet plug formation

sealing of the ruptured blood vessel

Coagulation

blood changes from liquid to a gel forming a blood clot

Arteries carry blood away from the

heart under enormous pressure

Arteries are

thick walled and have three layers; they lack connective tissue, and the smooth muscle layer is thin

Arteries diverge into smaller vessels called

arterioles

Capillaries exchange

solutes and water with cells of the body

Precapillary sphincters are rings of

smooth muscle that regulate the flow of blood through capillary beds

Capillaries are microscopic

blood vessels that are thin walled (one layer) and porous; the walls consist of a leaky layer of epithelial cells, and the microscopic pores allow for fluids and some material to be exchanged through diffusion

Capillaries converge into smaller vessels called

venules

Veins return blood to the

heart and act as a blood reservoir

Veins have

three layers and are thin walled; they have a larger lumen than arteries and can be stretched

The human heart is surrounded by

a fibrous sac called pericardium

The four layers of the heart

epicardium, myocardium, endocardium, and the septum

The four chambers of the heart are split into

two atria and two ventricles

Blood flow

• the right side of the heart (right atrium) accepts oxygen-depleted venous (from the vein/ vena cava) blood that has already circulated to body cells (muscles, digestive system, etc.)

• blood is pumped out of the right side of the heart (right ventricle) through the pulmonary artery to the lungs

• gas exchange takes place in the lungs; blood picks up oxygen and releases carbon dioxide

• the left side of the heart (left atrium) receives oxygen-rich blood from the lungs (travels through the pulmonary vein to the heart)

• oxygenated blood from the left side of the heart is destined for body cells (leaves left ventricle through the aorta)

• blood reaching the small intestine supplies oxygen and nutrients to intestinal cells and also picks up nutrients from digestion of food

The cardiac cycle is a complete cycle of events in the heart from

the beginning of one heart beat to the beginning of the next heart beat

The cardiac cycle consists of a period of

relaxation (diastole) and contraction (atrial and ventricular systole)

Vertebrate hearts are classified as

multi-chambered

Fish have

two chambered hearts and use gills as a site of gas exchange

Amphibians and most reptiles have

three chambered hearts (1 ventricle and 2 atria)

Many simple organisms are capable of exchanging gas with the environment via

simple diffusion

The tracheal system in insects consists of

a series of epithelial tubes that function as a respiratory organ (spiracles → trachea → air sacs → tracheoles)

Cutaneous gas exchange is a form of

 respiration where gas exchange occurs through the skin

Many vertebrates have both

cutaneous respiration and functional lungs

Gills are thin tissue filaments that are

highly branched and folded with many capillaries for gas exchange

Four types of respiration

tracheal system, cutaneous gas exchange (gills and skin), diffusion, and breathing/ inhalation that takes place in mammals (pulmonary ventilation)

Diffusion across the cell membrane is sufficient for supplying oxygen to the cell in

unicellular organisms

In order for diffusion to be a feasible means of providing oxygen to the cell

 the rate of oxygen uptake must match the rate of diffusion across the membrane (cell can’t be too large/ thick bc diffusion wouldn’t be able to provide oxygen quickly enough to the inside of the cell)

In mammals pulmonary ventilation occurs via

 inhalation (breathing)

Components of the upper respiratory tract

• Nose, nasal passages, sinuses (nasal cavity)

• Pharynx

• Larynx

The nasal cavity and pharynx

• Act as passageway for respiration

• Filter larger foreign material from incoming air, inhaled microorganism are entrapped in mucus

• Moisten and warm incoming air

• Composed mostly of ciliated cells

• Have resonating chambers for voice

The larynx (two important components)

• Epiglottis: flexible flap of cartilage that routes air and food appropriately

• Vocal chords: assist in sound production

Components of the lower respiratory tract

• Trachea

• Bronchi and bronchioles

• Lungs

• Alveoli

Trachea

• Trachea transports air to and from lungs

• Composed of a c-shaped ring of cartilage held together by connective tissue and smooth muscle

• Lined with mucus secreting ciliated epithelium

• Mucus traps foreign particles, bacteria, and other residues and cilia moves them up and out of the lungs

• Cilia are located through the upper and lower respiratory tract

Bronchi and bronchioles

• Trachea branches into two airways-- right and left bronchi

• Bronchi contains ciliated epithelia (cilia), smooth muscle, cartilage

• Bronchioles are the smallest branches (1 mm in diameter)

• Lack cartilage

• Bronchioles lack cilia

• Bronchioles deliver air to tiny sacs called alveoli (singular alveolus)

Lungs

• Composed of supportive tissue enclosing the bronchi, bronchioles, blood vessels, and alveoli

• Each lung is enclosed in two layers of pleural membranes

• Pleural cavity contains fluid that reduces friction as lungs move

Alveoli

• Lungs receive deoxygenated blood from the heart through pulmonary arteries

• Pulmonary capillaries allow blood to come into close proximity with air in alveoli (gas exchange)

• Veins collect the oxygenated blood from alveolar capillaries and return it to the left side of the heart

Air enters and leaves the lungs through

inspiration and expiration (pressure driven)

Inspiration

• diaphragm contracts and lowers

• intercostal muscles contract/ expand chest wall outward (volume of thoracic cavity increases)

• intrapleural pressure drops

• lungs expand and air is draw into the airways

Expiration

• diaphragm and intercostal muscles relax (thoracic cavity volume decreases)

• intrapleural pressure returns to normal

• lungs recoil and airways close; air passively exit the lungs

Steps for breathing

• inspiration occurs as

• air enters through the nasal cavity and is warmed to body temp/ humidified (must be humidified bc dry air can damage respiratory tract)

• foreign material is filtered/ microorganisms are entrapped in mucus/ removed through cilia

• air then passes to the pharynx and larynx and then to the trachea

• trachea transports air to and from the lungs

• trachea is branched into the right and left bronchi which delivers air to the lungs

• bronchi branch into bronchioles

• bronchioles deliver air to alveolar ducts

• alveolar ducts have alveolar sacs which contain alveoli

• gas exchange occurs in the alveoli

• lungs receive deoxygenated blood via pulmonary arteries

• pulmonary capillaries allow blood to come into close contact with with air in alveoli allowing for diffusion to occur (blood becomes oxygenated and releases co2 into alveoli

• expiration moves co2 out of lungs

• veins collect the oxygenated blood and return it to the left side of the heart

Gas exchange during respiration occurs primarily through

diffusion

During diffusion gas molecules move from a region of

high concentration to a region of low concentration

The air in the lungs has a higher concentration of

oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide than blood; this allows for gas exchange between blood and air in the lungs

External respiration

• lungs receive deoxygenated blood through pulmonary artery

• branches into pulmonary capillaries → creates respiratory membrane with alveoli

• as blood in pumped into the capillary network gas exchange occurs

• some oxygen gets dissolved directly into the plasma, but most binds to hemoglobin in RBCs

• pressure gradient between alveoli and blood in capillaries allows for gas exchange

• partial pressure of oxygen in alveoli > partial pressure of oxygen in blood → diffuses down gradient

• carbon dioxide gets released into the alveoli by blood since the partial pressure of carbon dioxide in the blood is > the partial pressure of carbon dioxide in the alveoli

• blood returns to the left side of the heart through pulmonary veins

• carbon dioxide is exhaled

Internal respiration

• gas exchange with body tissues

• partial pressure of oxygen in tissues < partial pressure of oxygen in blood

• oxygen dissociates from hemoglobin, diffuses from blood, crosses interstitial space and enter tissues

• partial pressure of carbon dioxide in blood < partial pressure of carbon dioxide in tissues

• carbon dioxide diffuses from tissues, crosses interstitial space and enters blood

• carbon dioxide gets carried back to the lungs either dissolved in plasma, bound to hemoglobin, or in its converted form

98% of oxygen carried in blood is bound to

hemoglobin in RBCs

2% of oxygen is dissolved in

plasma

70% of carbon dioxide is converted to and transported in

the plasma as bicarbonate (H+ is produced as a byproduct)

10% of carbon dioxide is dissolved in

plasma

20% of carbon dioxide binds to

hemoglobin for transport

Osmosis

the diffusion of water across a semi permeable membrane

Concentration gradient for water

from an area of high water concentration to an area of low water concentration

Concentration gradient for water in terms of solute

from an area of low solute concentration to an area of high solute concentration

Osmolarity

describes the solution's total solute concentration-- water moves from the solution of lower osmolarity through the membrane towards the solution of higher osmolarity

Isotonic solution

osmolarity (concentration of solute) is the same inside and outside of the cell (in equilibrium)

Hypertonic solution

higher osmolarity (concentration of solute) outside the cell (cell shrinks)

Hypotonic solution

low osmolarity outside the cell (concentration of solute is lower outside the cell than inside the cell) (cell swells)

Osmoregulation

 the process of maintenance of salt and water balance (osmotic balance) across membranes within the body's fluids, which are composed of water, plus electrolytes and non-electrolytes

Blood maintains an

isotonic environment

Kidneys

filter blood, removing waste and maintaining osmotic balance

Ureter

urine passes through the ureter to reach the bladder

Kidney protected by tough connective layer called the

renal fascia

Kidney’s layers

outer cortex, medulla in the middle, and renal pelvis in the region called the hilum

The cortex is granular due to the presence of

nephrons