HN220 Midterm 1

What are the levels of organization of the body?

1) cells

2) tissues

3) organ

4) organ system

What is a cell?

Basic unit of life

What is tissue made of?

Group of cells

What is an organ made of?

A group of tissues that work together

What is an organ system made of?

multiple organs working together

What is an organism made of?

multiple organ systems

What four groups can cells be classified into?

1) Neurons

2) Muscle cells

3) Epithelial cells

4) Connective tissue cells

What are neurons?

nerve cells

- excitable cells that transmit electrical signals

What are muscle cells?

Specialised cells that can contract and relax

What are the three types of muscle cells?

1) Skeletal

2) Cardiomyocytes

3) Smooth muscle

What are cardiomyocytes?

heart muscle cells

What are epithelial cells?

Cells that line organs and tubes

What are connective tissue cells?

Cells that make up any structure whos primary function is to provide physical support for other structures, anchor them, or link them together

- e.g. blood cells, skin cells, bone cells

What is the most diverse type of cell?

connective tissue cells

What are the four major types of tissue?

1) nerve tissue

2) muscle tissue

3) epithelium (epithelial tissue)

4) connective tissue

What is homeostasis?

The body's ability to maintain a constant internal environment

what are the components of the internal environment that are regulated?

1) temperature

2) volume

3) composition

What are afferent signals

signals arriving to the brain

- travel from receptors to the control center in the brain

- sensory signals

what are efferent signals

signals travelling from the brain

- travel from control center to effectors

- motor signals

What is generated when skeletal muscle contracts?

heat

What are some examples of receptors?

1) thermoreceptors

2) chemoreceptors

3) baroreceptors

What are thermoreceptors?

detect changes in temperature

What are chemoreceptors?

Chemically sensitive cells

- serve as sensory receptors

What are baroreceptors?

pressure and stretch receptors

What is a common example of where baroreceptors are found?

Your heart and blood vessels

- helps with blood pressure

What do integrating centers do?

orchestrates an appropriate response

- many integrating centers are found in the brain

- can be the cell itself

Where are effectors?

muscles and glands

- respond to nerve impulses

What are signals?

allow components to communicate

- neurotransmitters and hormones

Explain the pathway of achieving homeostasis

- receptor send an input signal to an integrating center (afferent)

- integrating center sends an output signal to an effector (efferent)

How many cells are in the human body

75 trillion

What are the 2 basic types of ways cells communicate with each other

- Electrical signals

Involves changes in membrane potential

- Chemical signals

What is the most common way cells communicate with each other

-Most common way cells communicate with each other in the human body is using chemical signals

Describe chemical signaling in terms of communication between cells in the body

-Secretion of a chemical

-Chemical messengers in the form of cytokines, hormones, amino acids, neurotransmitters, etc circulate with the body locally and allow them to communicate near adjacent and distant cells

-Secreted into the Extracellular fluid

Fill in the blank:

Cells responding in cell to cell communication are called ________ __________

Target cells

What are the fundamental stages to signal transduction?

1. Reception

2. Transduction

3. Response

Describe Reception in Signal Transduction

Signal molecule has an affinity to bind to a protein

Key and Lock model

Describe Transduction in Signal Transduction

Cell won't understand what the chemical signal is after Reception stage

It converts/transduces it into a message that causes a response within a cell

Ex. Kinases can phosphorylate proteins within the cell which triggers a response in the cell

How do Cells communicate locally?

Using special junctions

WHat are the types of special junctions

Tight Junctions

Desmosomes

Gap junctions

How do cells communicate long distance?

-Combination of electricala nd chemical signals

Electrical via nerve cells

Chemical via blood (hormones)

Where are tight junctions found

Found in epithelium

Fill in the blank:

The binding in tight junctions between adjacent cells are formed by proteins called ________

Occludins

What are occludins

-Integral proteins that fuse adjacent cells in TIGHT JUNCTIONS

-Form a nearly impermeable barrier

-Forces a molecule to cross the epithelial cell layer

Describe the steps communication occurs in tight junctions

Lumen (apical membrane) --> Epithelial cell cytosol --> Basolateral membrane (ECF)

Describe Desmosomes

-Provide adherence between adjacent cells

- Filamentous junction between cells

-Bind cells together for strength

-Found in tissue subject to mechanical stress

Ex. Smooth muscle cells and cardiac muscle cells

Describe Gap Junctions

- Link the cytosol of 2 adjacent cells

-Ions and molecules moving between cells acts as a signal

-Direct communication between cells

-Composed of membrane proteins

What proteins are associated with gap junctions?

Connexins

What are Connexins

-Gap junction protein

-Spans membrane creating a channel

-When channel is open, cells act as 1

-20 diff types of connexins

Intercellular communication coordinates cell activity for _______

Homeostasis

How is direct intercellular communication achieved?

-Gap junctions

Ex. cAMP, Ca2+

How is indirect intercellular communication achieved

- Chemical messengers in the form of neurotransmitters impart their effect on end target cells

True or False:

Indirect intercellular communication via neurotransmitters always impart their effect on other neurons

False

Can go to another neuron but it can also be other cells such as a skeletal muscle cell

What are the 2 ways local communication occurs

-Autocrine signals

-Paracrine signals

What are autocrine signals

Act on the same cell that secreted them

Ex. Immune cells do this

What are paracrine signals

Secreted by one cell and diffuse to adjacent cells as long as the the target cell have the receptors for that particular messenger

How does the peripheral nervos system illicit long distance communication between cells

Via neurotransmitters, released at axon terminals

Ex. Acth and norepinephrine

What are neurotransmitters

Chemicals secreted by neurons that diffuse across a small gap to the target cell

What are neurohormones

Chemicals released by neurons int the blood for action at distant targets

Usually derived from neurally derived tissue as opposed to endocrine tissue

Ex. Epinephrine released by specialized neural tissue in adrenal glands

What do membranes do

-Separate material between the intercellular fluid and extracellular fluid

-Allow exchange of material between ICF and ECF

Why is transport across membranes important

-Allows us to obtain oxygen and nutrients while also getting rid of waste products

Non-polar molecules are ______ transported across the membrane

Easily trasnported

Via simple diffusion

Ex. O2, CO2, Fatty acids

Ions and polar molecules are normally _________ across the membrane

Normally not transported across the membrane

They need help

Ex. Glucose, Proteins, Na+

Is K+ higher in concentration in the ICF or ECF

ICF

Is Na+ higher in concentration in the ICF or ECF

ECF

Is Ca2+ higher in concentration in the ICF or ECF

ECF

Is Cl- higher in concentration in the ICF or ECF

ECF

True or False

Amino acids and proteins are positively charged and have a higher concentration in the ECF

False

Amino acids and proteins are negatively charged and have a higher concentration in the ICF

What factors determine the direction of transport

Chemical Forces

Electrical Forces

Both= Electrochemical forces

Describe Passive transport

- Spontaneous

-Downhill movement (simple diffusion)

-High to low concentration

Describe Active transport

-Needs energy (ATP) to happen

-Not spontaneous (requires pumps)

-Uphill movement

-Against the concentration gradient (Low to high)

What is the chemical driving force based on

Concentration gradients

Moves molecules from high concentration to low concentration

What 2 factors does the direction of the electrical driving force depend on?

1) polarity of the cell

2) charge on the particle

Does the ICF have more anions or cations?

anions

- has a negative charge

Does the ECF have more anions or cations?

cations

- has a positive charge

What is the equation for the total force?

chemical + electrical forces

If the forces act in the same direction, what is the equation of the magnitude?

magnitude = chemical + electrical force

If the forces act in the same direction, what direction will the force be?

the same direction of each force

If the forces act in the opposite direction, what is the equation of the magnitude, and what direction will the force be?

magnitude = larger force - smaller force

If the forces act in the opposite direction, what direction will the force be??

of the stronger force

True or false: an ions equilibrium potential is a membrane potential in which the electrical force = the chemical force

true

If Vm = Ex, then force =?

force = 0

What do you need to determine which force is larger?

an ions equilibrium potential

What direction does the electrochemical force follow? (How do you know which way an ion will move across the membrane?)

It will favour the force which will bring the membrane to the equilibrium potential

- It will move in the direction that will lead to Vm = Ex

If a chemical gradient existed, under which conditions would a particle not be transported across a membrane even if it is permeable to that particle?

when the electrical force is equal to, but opposite in direction to the chemical force

true or false: an ions equilibrium potential is a membrane potential in which the electrical force and chemical force act in opposite directions

true

true or false: equilibirum is achieved when the Vm is equal to the equilibirum potential

true

What creates a membrane potential?

1) ion concentration gradients between ECF and ICF

- difference in charge

2) selectively permeable cell membrane

What are the 2 principles of the elctrical driving force?

1) opposites attract

2) like charges repel

chemical force + electrical force = ?

electrochemical force

What should you consider when determining the direction of the electrochemical force for a particular ion?

1) the membrane potential

2) the equilibrium potential

3) direction of the chemical and electrical forces

What is the equilibrium potential of an ion?

the membrane potential at which the ions movement will be at equilibirum

- 0 flux

What is permeability

Determines what moves in and out of cell

Cell membranes are selectively permeable

Selective permeability restricts materials based on:

- Size

-Molecular shape

-Electrical charge

-Lipid solubility

What is bulk flow

-Type of Transport process

-Movement of fluids (gases and liquids)

-Uses pressure gradients

Ex. Blood through circulatory system (blood has dissolved solutes and blood cells)

Describe other forms of transport

Diffsuion

Protein mediated transport

Vesicular transport (vesicle)

True or False:

Diffusion will continue until equilibrium is reached

True

True or False

If a system is already at equilibrium, there is no concentration gradient, thus diffusion cannot occur

True

Describe Passive Transport

- Spontaneous

-No cell E required

-Downhill movement

What are the types of passive transport

- Simple diffusion

-Facilitated diffusion (protein structure facilitates movement)

-Diffusion through channels (Channels that have pores which allow movement of ions to travel through)

True or False

Simple diffusion uses membrane proteins

False