Mechanisms Midterm - Lecture 1

course intro

physiology

the study of how the body works -  functions and mechanisms in a living system.

• Focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical and physical functions in a living system

pathophysiology

the study of disorders in physiologic processes that lead to disease states

Chemistry (atoms) -> molecules and macromolecules -> cells -> tissues -> organs -> organ systems -> organism

describe the organization of the body

epithelium

the layer of cells that faces the outside of the body. inside-outisde interface. sheets of cells connected by tight junctions, desmosomes. often polarized - apical and basal sides

basal lamina

what do epithelial cells rest on?

skin, intestine, respiratory tract lining, kidney cells, secretory glands, gut lining

where to find epithelial cells

simple squamous (flat, outside of skin)

simple cuboidal (kidney tubules)

simple columnar (ciliated, line respiratory tree)

stratified squamous (form layers of skin that are impervious to water)

stratified cuboidal

stratified columnar

classifications of epithelium

neurons

electrically excitable cells that send and receive signals. can flip potential across membranes

neuroglia

supportive glia

schwann cells

neuroglia in PNS

oligodendrocytes, astrocytes, microglia, ependymal cells (ependymal cells make CSF).s

neuroglia in CNS

cell body (where metabolism occurs - nucleus and mito), dendrites (send nerve impulses in and contacted by other neurons), axons (send nerve impulses out)

components of neural tissue

muscle cells

electrically excitable cells that contract on excitation and provide movement and stability for the body

actin and myosin

muscle cells: contraction is provided by interlinked fibers of …

skeletal (voluntary - limbs, strength, standing)

cardiac

smooth (voluntary - gut, artery, respiratory tree)

three types of muscle

connective tissue

binds cells and organs together and provides structure and support for the body

collagen, proteoglycans, fibroblasts, adipose tissue, cartilage, bone

connective tissue: cells are dispersed in a matrix containing…

areolar connective tissue (loose, holds organs together, prevents sliding)

adipose tissue (fat, energy storage)

fibrous connective tissue (tendons and ligaments, collagen and other fibrous proteins)

blood

osseus tissue

hyaline cartilage (ear, hert valves, long bone joints, ribs. slippery)

types of connective tissue

homeostasis

the process by which the body maintains a stable equilibrium/steady state in response to changing conditions

stimuls (state change)

sensor (detects change)

control center (interprets signal from sensor)

effector (receives signal from control center and changes physical state)

components of a feedback loop (homeostasis)

decreased calcium: parathyroid glands release PTH → osteoclasts release calcium from bone, calcium reabsorbed from urine by kidneys, calcium absorption in small intestine increases via vitamin D synthesis → calcium level in blood increases

increased calcium: thyroid gland releases calcitonin → osteoclast activity inhibited and calcium reabsorption in kidneys decreases → calcium level decreases

key players: vitamin D, thyroid gland, parathyroid gland, bone, kidney, intestine

describe the maintenance of homeostasis of blood calcium

negative feedback loop (eg. activation of sweat glands in response to increase in body temp)

the effector opposes the change in the physical state. brings change back toward normal

positive feedback loop

the effector augments the change in the physical state. brings change to end point, not back to normal

head of baby pushes against cervix → nerve impulses from cervix transmitted to brain → brain stimulates pituitary gland to secrete oxytocin → oxytocin carried in bloodstream to uterus → oxytocin stimulates uterine contractions

describe labor as a positive feedback loop

diffusion

movement of solutes from area of high to low concentration

osmosis

movement of water from area of low to high solute concentration, where areas are separated by semi-permeable membrane

lipid bilayer

why are cell membranes impermeable to most substances?

aquaporin channels

how water can cross most membranes. driven by osmotic forces and solute concentration

channels or transporters

ionic and hydrophilic molecule require ______ to cross membranes

pumps (rotary ATPase, P-type ATPase that move Na+/K+, sarcoplasmic reticulum calcium ATPase. also ABC transporters like CFTR and ATP binding cassette)

use energy (ATP) to move substance (usually cations) across a membrane against electrochemical gradient. active transport

carriers

bind solutes and change conformation to move solutes across membrane. facilitated diffusion (high to low concentration) and cotransport (against concentration gradient)

facilitated diffusion

high to low concentration. substrate transported along concentration gradient

co-transport/symport

substrate transported against concentration gradient using another ion transported in the same direction to power the transfer

antiport

substrate transported in opposite direction of co-transported ion

channels

provide openings in the membrane that let specific substances through, but do not have binding site for the molecules. passive diffusion, along concentration gradient.

gating

opening and closing according to simuli

pore

how molecule moves through center of channel. narrow, and only a specific ion fits due to size and charge

fraction of time it is open

how is flux through a channel determined?

voltage-gated channel (nerve conduction, muscle contraction, sensory responses)

open and close in response to electric charge (electric potential) across membrane. membranes have potential difference between inside and outside because of differences in ion concentrations

Na+, K+, Ca2+, Cl-

ions transported through voltage-gated channels

ion flux decreases → voltage changes → threshold reached → pores open

general steps for voltage-gated channel

ligand-gated channel

open and close in response to binding of another molecule to channel on either the outside or inside of the membrane

neurotransmitters (acetylcholine, dopamine, glutamate) bind outside of membrane, open Na+ or K+ channels for nerve conduction and muscle contraction

describe neurotransmitters and ligand-gated channels

second messengers (cAMP, cGMP, G protein subunits) bind inside membrane to open or close channels in sensory receptors in nose and eye

describe second messengers in ligand-gated channels

Na+, K+, Ca2+

ions transported through ligand-gated channels

aquaporin (form very small channels which contain many positive charges)

composes pores that allow water to pass in either direction through cell membrane.