Physiology Midterm 1

Topics 1-5

Homeostasis

Processes carried out by all organ systems so that organisms can maintain a dynamic state of equilibrium to function properly

Intracellular fluids (ICF)

Found inside of cells

Extracellular fluids (ECF)

Found outside of cells

3 factors necessary for feedback systems

Receptor, control center, effector

Receptor

Monitors environment and responds to changes

Control center

Determines a set point, analyzes input and determines a response

Effector

Acts upon information from control center

Negative feedback mechanism

Reverses an initial effect (e.g., body temp and blood sugar levels)

Positive feedback mechanisms

Amplify the initial effect and are not homeostatic, also quite rare (e.g., labor contractions, blood clotting)

Salts

contain cations and anions (other than H⁺ and OH⁻), dissociate readily in water

Buffers

molecules that resist abrupt changes in pH

Carbohydrates

Main function is to provide energy- sugars and starches, contain carbon, hydrogen, and oxygen. only make up 2-3% of total body mass

Polysaccharides

Many simples sugars linked together, form in which carbohydrates are found

Homopolysaccharides

Many molecules of one sugar, glycogen, starch, cellulose

Glycogen

Most important homopolysaccharide, used for storage of glucose. Made and stored primarily in the liver, skeletal muscle, and cardiac muscle

Starch

Storage product in plants, most common carbohydrate in human diets. Found in wheat, potatoes, rice

Heteropolysaccharides

Most only contain two types are are associated with proteins, glycoproteins

Lipids

Fatty compounds used for energy storage, protection of organs and structural components of membranes- contain carbon, hydrogen, and oxygen but proportion of oxygen is lower, make up 18-25% of body mass

Fatty Acids

The simplest lipids, are broken down to produce ATP

Triglycerides

Neutral fats, large molecules used for storage found just below the skin

Phospholipids

Modified triglycerides that contain phosphorous found in cell membranes

Proteins

The basic structural material of the body- contain carbon, oxygen, hydrogen, and nitrogen (many also contain sulfur) and make up 12-18% of body mass. Composed of many amino acids

Structural levels of proteins

Primary, secondary, tertiary, quarternary

Primary structure

Amino acids in a polypeptide chain

Secondary structure

Polypeptide chains form spirals or sheets

Tertiary structure

Folded up polypeptide spirals or sheets

Quaternary structure

Two or more chains combine to form a functional protein

Nucleic Acids

The largest molecules in the body, composed of C, O, H, N, P, two classes: DNA and RNA

Nucleotides

The structural unit of nucleic acids, there are five

Purines

Two ring bases, Adenine and Guanine

Pyramidines

One ring bases, Cytosine, Thymine, and Uracil

DNA

Found in the nucleus, replicates itself so it so it is found in most cells, provide information for building all proteins

RNA

Found outside nucleus, carries out orders for protein synthesis, different types carry out different parts of the building process, single strands of nucleic acids

Adenosine Triphosphate (ATP)

Made by glucose, provides energy that is used by cells directly

Integral proteins

embedded in the membrane

Peripheral proteins

Attached to one surface

Cell membrane proteins

Provide structural support, transport molecules, enzyme control, cell receptors, and identifying cell markers

Cell membrane carbohydrates

Primarily attached to outer surface of membrane, negatively charged, affects the activity of regulatory molecules and interactions between cells

Cell to cell adhesion junctions

Tight junctions, desmosomes, gap junctions

Tight junctions

Integral proteins in adjacent cells fuse together making it difficult for anything to pass between cells. Found primarily in sheets of epithelial tissues

Desmosomes

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Act like a zipper to hold cells together (adhering junctions), important in cells where there is mechanical stress

Gap junctions

Used to communicate between adjacent cells, permitting passage of small signaling molecules. Abundant in cardiac and smooth muscle tissue- connexins made up of 6 proteins arranged in hollow tube-like structure

Unassisted membrane transport

Molecules that can penetrate the plasma membrane on their own can be driven by diffusion down a gradient

Diffusion

Solute moves from an area of high concentration to low concentration, molecules will tend to become evenly spaced

Passive diffusion of ions

Substances can diffuse along an electrical gradient, oppositely charges ions will attract each other

Osmosis

Water can readily permeate the plasma membrane because molecules are small enough to slip between bilipid layer. Solute conc. will increase and water conc. will decrease, so water will flow from an area of lower conc. to one of higher solute conc.

Isotonic solution

Same concentration of solute/water inside and outside of cell. Water moves both into and out of cell, no change in cell shape

Hypertonic solution

Higher concentration of solutes outside of the cell, water will flow out of the cell and the cell will shrink

Hypotonic solution

Lower concentration of solutes outside the cell, water flows into cell and the cells expand and burst

Assisted Membrane Transport

The movement of molecules across the plasma membrane, with help. Used when substances/molecules are very large, ions are going against concentration gradient, poorly lipid soluble molecules

Carrier-mediated transport

Type of assisted membrane transport, proteins span the plasma membrane, can have binding sites at either side (ECF/ICF)

Properties of carrier proteins

Specificity, saturation, competition

Specificity

Property in which proteins carry one substance (or a few)

Saturation

Property in which proteins have a limited number of binding sites

Competition

Property in which proteins will have several closely related compounds competing for a ride

Facilitated Diffusion

Uses a carrier to assist the transport of a substance downhill from high to low concentration

Active Transport

Uses a carrier to assists the transport of a substance against concentration gradient, requires energy in the form of ATP

Vesicular transport

Molecules that are too large to cross the membrane are wrapped in a membrane-enclosed vesicle, energy is required

Endocytosis

Moving substances into the cell, 3 types

Exocytosis

Moving substances out of the cell, used to secrete large molecules, and adds components to the plasma membrane

Phagocytosis

Large molecules are internalized, only done by certain cell types, get rid of tissue debris or bacteria

Pinocytosis

A small droplet of extracellular fluid is internalized, carried out by most body cells, gets rid of extra plasma membrane

Receptor-mediated endocytosis

Highly selective, enables cells to import specific large molecules needed by the cell, but can be exploited by certain viruses

Cytoplasm

Consists of cytosol and organelles that carry out specific functions

Cytosol

Semitransparent fluid, mostly water with proteins, salts, sugars, etc.

Mitochondria

Organelle used for energy production

Smooth endoplasmic reticulum

Organelle used in lipid production and detoxification

Rough endoplasmic reticulum

Organelle used in protein production

Golgi Apparatus

Organelle used in protein modification and export

Lysosome

Organelle used in protein destruction

Nucleus

Control center of the cell, provides instructions for building proteins, most cells have more than one. Surrounded by a selectively permeable membrane

Local communication

Gap junctions, cell-to-cell contact, paracrine and autocrine signals

Cell-to-cell contact

Contact-dependent signalling, important during growth and development, some communication requires that surface molecules on one cell bind to those on another

Paracrine signal

Act in immediate vicinity of cell that secreted signal

Autocrine signal

Acts on the cell that secreted signal

Histamine

Type of paracrine signal, released in response to allergic reactions, injury, or infection- blood vessels will dilate and capillaries will become more permeable

Long distance communication

Can be electrical or chemical, endocrine cells use hormones, nervous system uses electrical and chemical signals

Signaling path features

Molecule is a ligand which binds to receptor, ligand-receptor complex is activated, activated receptor activates intracellular molecules, response is initiated

Agonists

Drugs that occupy receptors and activate them

Antagonists

Drugs that occupy receptors but do not activate them, block receptor activation

Hormone disruptors

Can mimic or block a particular hormone resulting in increased or decreased cellular response

Homeostatic Reflex Pathways

Cellular signaling systems responsible for maintaining homeostasis. Involve two control systems, and seven steps.

Stimulus

Disturbance or change that set pathway in motion

Sensor

A multicellular receptor that responds to changes in the environment

Input signal

Will vary depending on type of reflex, not found in endocrine reflex since stimulus acts directly on endocrine cell

Integrating Center

In neural reflexes, integrating center lies within central nervous system, will interpret and initiate a response

Target

Cells or tissues that carry out the response

Response

Cellular response that takes place in target cell, overall change in the organism

Neural reflex- dim light

Signal received from sympathetic nervous system, pupils dilate

Neural reflex- Bright light

Signal received from parasympathetic nervous system, pupils contrict

Central nervous system

Made up of the brain and spinal cord

Peripheral nervous sytem

Made up of neural tissue outside of CNS, sensor and motor neurons

Sensory nervous system

Contains receptors and transmits information from receptors to CNS

Motor nervous system

Transmits information from CNS to rest of body, and sends motor information to effectors

Somatic nerves

Voluntary, usually to skeletal muscle

Autonomic nerves

Involuntary, usually to smooth muscle of body organs or glands

Neuron

Used for reception, transmission, and processing of stimuli. Triggers certain cell activities and releases neurotransmitters

Nerve cells

Extremely variable in shape and size, three categories: multipolar, bipolar, pseudounipolar

Multipolar nerve cells

One axon and many dendrites, have more than two processes

Bipolar nerve cells

One axon and one dendrite