Homeostasis

Cell Transport

Cell Membrane

• Functions:• Provides protection and support• Provides protection and support.

• Regulates what enters gand leaves the cell.• Takes in food and water.

Eli i t t• Eliminates waste.• Allows the cell to maintain

homeostasis.

The cell membrane is .

S b h h i • Some substances can pass through it, while others cannot.

• Most biological membranes are .

Parts of the Cell Membrane: the core

of the membrane; forms of the membrane; forms a strong barrier between the cell and the outside

: form pumps to move material p pthrough membrane

: identif : identify the cell; on the outside

ConcentrationConcentration

• How many molecules are in a given volume (How • How many molecules are in a given volume. (How crowded the molecules are.)

• Concentration = Amount of solute• Concentration = Amount of soluteVolume of Solution

E ll i d d b li id d h li id • Every cell is surrounded by liquid and has a liquid interior (cytoplasm) that are solutions of many different substances.

High Concentration Low Concentration

: movement from an area of high concentration to areas of lower concentration (getting less crowded)

: molecules th t t l t th h that are too large to pass through the cell membrane go through protein channelsprotein channels

: the diffusion of water: the diffusion of water

: movement from an area of low concentration to areas of higher concentration (getting more crowded)(g g )

: when a vesicle fuses with the cell membrane to take material out

: brings material into h ll h k i h the cell when a pocket in the

membrane breaks off, forming a vesiclevesicle1.) : large particles taken

in2 ) ll ti l t k 2.) : small particles taken

in

Homeostasis & Cells

Cell Specializationp

Cells in multicellular organisms are • Cells in multicellular organisms are interdependent.

• Cells in multicellular organisms are to perform particular functions in the organism.p p g

Cells – Tissues- Organs- Organ Cells Tissues Organs Organ Systems- Organism

Cell• The basic unit of life.

Tissue• A group of cells that perform a particular

functionfunction.• Four types:▫ ConnectiveConnective▫ Epithelial▫ Muscle▫ Nervous

Organsg• A group of tissues working together to perform a

particular functionparticular function.• Examples:▫ HeartHeart▫ Stomach▫ Lungsg

Organ Systemg y• A group of organs working together.

Examples:• Examples:▫ Nervous system▫ Circulatory systemCirculatory system▫ Digestive system

Organismg• Any living thing.

Cell Communication• Cells in a large organism use chemical

i l t i t signals to communicate. ▫Ex: heart muscle contraction

ifi i h ▫Receptor: a specific protein where the chemical signal can bindOn the cell membrane or in the cytoplasm

Fight or Flight

Homeostasis• The relatively constant internal conditions that

organisms maintain despite change in their organisms maintain despite change in their internal and external environments.

• Homeostasis and organ systems:▫ The nervous system sends messages over a system

of neurons in fractions of a second of neurons in fractions of a second. ▫ The endocrine system sends messages using

chemicals (hormones) which takes much longer, b t l t l ll ( i t d )but last longer as well. (minutes-days)

Feedback Systemsy

• When the brain receives messages from th b d b t i t l h it k t the body about internal chance, it works to restore the system to equilibrium

• Two types of feedback loops▫ Negative ▫ Positive

Negative Feedback LoopsNegative Feedback Loops• Ex: maintaining body temperature

rise in temp. -> brain “thermostat” -> message to sweat glands to sweat -> body temp. drops

OR

drop in temp. -> brain “thermostat”-> sends message s to shiver -> body temp. rises

Positive Feedback LoopsPositive Feedback Loops• Ex: childbirth (labor)

pressure from baby’s head -> uterine contractions-> more pressure -> more contractions

Nervous System

The Nervous Systemy

• Collects information about the body’s internal and external environment processes and and external environment, processes and responds to it.

• Two Parts:Two Parts:▫ Peripheral Nervous System▫ Central Nervous Systemy

Peripheral Nervous Systemp y• Consists of nerves and supporting cells.

• Collects information about the body’s external and internal environment and internal environment.

Central Nervous System

i f h b i d i l d• Consists of the brain and spinal cord.

P i f ti f P i h l N • Processes information from Peripheral Nervous System and creates a response, which is sent back out through the PNS back out through the PNS.

PNS C i PNS: Gathers info. & sends it

to CNS

CNS: Processes info. & forms a response

PNS: Carries response to glands & muscles

N C ll i h Neurons: Cells in the nervous system that transmit impulses.

• Cell body: contains nucleus & cytoplasm

• Dendrites: receive impulses from other neurons

• Axon: carries impulses away from the cell body

• Myelin sheath: insulating membrane found on some neurons

Nerve Impulsesp

• An impulse begins when one neuron is stimulated by another neuron or the stimulated by another neuron or the environment.

• Impulses are transferred by the movement of action potential (created by ions), much like p ( y ),electric current through a wire.

Threshold• the minimum level of a stimulus required to

cause an impulse in a neuroncause an impulse in a neuron▫ All stimulus above the threshold trigger the same

impulse, but the frequency of impulses detected by p , q y p ythe brain can change with the sensation. Ex: touching something warm vs. burning yourself

Synapsey p• Point where a neuron transfers an impulse to

another cellanother cell.

• Neurotransmitters: the chemicals that • Neurotransmitters: the chemicals that transmit the impulse across a synapse to another neuron

Video

The nervous system helps maintain homeostasis in the bodyhomeostasis in the body.

Endocrine System

HormonesHormones• Chemicals released by glands to deliver

messages throughout the body messages throughout the body. • Hormones bind to specific receptors on the cell

membrane or within cells.

• target cells: cells with receptors for a particular g p phormone

Glands: organs that produce and Glands: organs that produce and release a substance (secretion)

Hormones help the body maintain Hormones help the body maintain homeostasis.