Homeostasis

4 primary types of tissues

muscle, nervous, epithelial, connective

muscle tissue

for contraction; includes skeletal, cardiac, and smooth muscle

nervous tissue

for signaling (via electrical impulses); includes central and peripheral

epithelial tissue

for exchange between cells and environment; epithelial sheets (form boundaries) and glands (secretion)

connective tissue

structural support; includes tendons, bones, and blood

circulatory system

heart, blood vessels, and blood

digestive system

mouth, esophagus, stomach, intestines, and related organs

respiratory system

lungs and major airways

urinary system

kidneys and associated structures

skeletal system

bones and joints

immune systems

white blood cells and lymphoid organs

muscular system

skeletal muscles

integumentary system

skin and related structures

nervous system

brain, spinal cord, nerves, and sense organs

endocrine system

all hormone-secreting glands

reproductive system

male and femal gonads and related organs

homeostasis

the maintenance of a dynamic steady state in the internal environment; dynamic mechanisms that detect deviations in physiological variables from set range and initate responses to restore variables to optimal range

maintaining homeostasis

cells exchange materials from intracellular fluid, interstitial fluid, and blood (specifically plasma)

homeostatic control system

interconnected network of body components that work together to maintain a given fator relatively constant

sensor

detects deviations from set point/range; usually many throughout different parts or the cell/process

control center

integrates information from sensor

effectors

makes adjustments to restore factor to normal; perform an action to help restore homeostasis

negative feed back

goal: remediate an unwanted change (bring it back to set range); used by both intrinsic and extrinsic control systems

afferent signal

sends info from sensor to control center; sometimes not needed if sensor and control center are the same cell

efferent signal

send info from control center to effectors

negative feedback glucose increases

sensor: B-cells → control center pancreas → effector insulin → makes muscles, fat cells, and others take glucose out of blood

negative feedback: decrease glucose

sensor: a- cells → control center pancrease → effector: glucacagon →liver release glucose into blood

intrinsic control system

local control system in an organ or tissue

extrinsic control system

control systems outside an organ or system; permitting coordinated regulation of several organs; ex: blood pressure, blood glucose, temperature, dehydration, etc

pathophysiology

abnormal functioning of the body associated with disease; severe homeostatic disruptions can lead to death

key to maintain homeostaiss

cells need to communicate with one another

gap junctions

direct intercellular communication; small molecules and ions are exchanged between adjacent cells; can have thousands of gap junctions in a cell; very common communication

transient direct link up of cell’s surface markers

less common direct interceullular communication

paracrine secretion

indirect interceullular communication via extra cellular chemical messengers; cells don’t have to adjacent to each other but they still have to be within the local area to communicate

autocrine signalling

signal and receptor on the same cell (signals itself)

neurotransmitter secretion

indirect interceullular communication via extra cellular chemical messengers; usues electrical signals and neurotransmitters

endocrine signaling

uses hormones and neurohormones to communicate throughout the whole body and if far away cells; hormones circulate the blood stream but only target specific cells (lock and key)

nervous system

wired system (strucutrally arranged between neurons and target cells) uses neurotransmitters released into synaptic cleft; chemical messenger only diffuses a very short distance across synaptic cleft; dependent on close anatomic relationship between neurons and target cells; very rapid response and brief action; main function is to coordinate rapid, precise responses

endocrine system

wirless system ( endocrine glands widely dispersed and not structurally related to target); uses hormones as chemical messenger which travels a long distance (or short) distance by blood; depends on specific target cell binding; generaly slow response and long duration of action; main function is to control activites that require long duration rather than speed

positive feedback

does not contribute to homeostasis but contribues to specific physiological needs; amplifies the inital change; moves the system away from the set point; important during childbirth or firing an action potential

hormones

extracellular signaling molecule that is released into the blood and acts at its receptors in distal tissues to elicit a physiolgical response; targets cells with its specific receptor; they are always present in the body but the amounts can differ

childbirth feed back loop

positive feedback loop; ocytocin → stimulates placenta to make prostalgandins → which induce contractions → contractions induce oxytocin → oxytocin induces more prostaglandins→ etc

feedforward

do not have detectors; activate homestatic mechanisms in response to an anticipated change; ex: anticipated in frequent event or in response to circadian rhythms