SBI 4UI - Homeostasis

homeostasis

- the way that the body keeps the same internal environemnt even through changes in external environment
- constant physiological adjustments of the body in response to external environemnt changes

receptor/sensor

- organs that detect changes or sense when conditions aren't in normal range
- ex. skin cells

effector

- an organ or cell that acts in response to a stimulus
- ex. sweat

control center/integrator

- organ which processes information and recieves from the receptor and sends signals to the effector
- ex. bran

hormones

- produced by the endocrine system to convey information between organs of the body

pheromones

- chemical signals used to communicate between individuals

neurotransmitters

- chemicals signals between cells of a localized cell

negative feedback mechanisms

- the response counteracts further change in the same direction
- stops when turns back to normal
- ex. blood pressure

positive feedback

- a change in some variable triggers mechanisms that amplify the change
- increases an action
- ex. contractions during child birth

thermoregulation

- the process by which animals maintain an internal temperature within a tolerable range

modes of heat exchange (4)

- radiation
- evaporation
- convection
- conduction

radiation

- the emission of electromagnetic waves by all objects warmer than absolute zero

evaporation

- the removal of heat from the surface of a liquid that is losing some of its molecules as gas

convection

- the transfer of heat by the movement of air or liquid past a surface

conduction

- the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other

insulation - balancing heat loss/gain

- feathers, hair, fat layers (reduces the flow of heat, lowers energy cost of keeping warm)
- goosebumps (raise hair on our bodies to make for insulation layers)
- raising fur or feathers (traps a thick layer of air, increasing its insulating power)

circulatory adaptations - balancing heat loss/gain

- vasodilation (gets bigger)
- vasoconstriction (gets smaller)

evaporative heat loss - balancing heat loss/gain

- heat is carried away with water molecules as they change into gas

adjusting metabolic heat production - balancing heat loss/gain

- shivering and moving (heat produced by muscle activity)
- non-shivering thermogenesis (certain hormones can cause mitochondria to increase metabolic activity)
- brown fat (specialized tissue for rapid heat production, high concentration of mitochondria)

interstital fluid

the fluid that surrounds body cells

extracellular fluid acts as a medium for:

- delivering energy
- transporting chemicals
- eliminating waste

all organ system are coordinated to carry out tasks such as:

- taking in molecules from environemnt & processing/distributing them throughout the body
- synthesizing molecules that are essential for cellular function
- sensing and responding to changes in the external environment

homeostatic mechanism

- s system that monitors internal & external conditions and changes bodily functions to maintain homeostasis

antagonistic effectors

- produce the opposite effect of the change recorded by the sensor
- used by negative feedback mechanisms

homeotherms

an animal that maintains a stable body temperature regardless of the temperature of the external environment

poikilotherms

an animal whose body temperature varies with, and often matches, the temperature of the external environment

endotherms

an animal that maintains its body temperature by internal mechanisms

ectotherms

an animal that maintains its body temperature by absorbing thermal energy from the environment

torpor

a short-term state of reduced metabolic rate and body temperature that reduces the demand for energy during the night or day

hibernation

a state of greatly reduced metabolic rate and activity that enables an animal to survive the winter by reducing the demand for energy when food is unavailable

estivation

a state of torpor that enables an animal to survive the summer by reducing the demand for energy

kidney

- two of them
- principle function is to filter blood and remove metabolic waste

secondary functions of the kidney

- control water balance and pH
- regulate blood levels of sodium, potassium, bicarbonate, and calcium ions
- secretes erythropoietin to stimulate red blood cell production
- activate vitamin D production in skin

renal artery

- from aorta to kidneys
- gives kidney blood

renal vein

- returns blood to heart

renal cortex

- outer layer of the kidney

renal medulla

- inner layer of the kidney
- where filtering takes place

renal pelvis

central space/cavity continuous with ureter (which transports urine to bladder)

nephron

tiny filters

step 1 of urine production: glomerular filtration

- begins in Bowman's capsule
- cells of the Bowman's capsule and the capillaries that surround it from a selectively permeable membrane with spaces wide enough to admit water, ions, small nutrient molecules and nitrogenous waste molecules
- high pressure of the blood in the glomerulus drives the molecules into the capsule (blood cells, platelets, and plasma are to large to pass through and are retained in the capillaries)

step 2 of urine production: tubular reabsorption

- filtrate passes through proximal tubule and is reabsorbed
- in the descending Loop of Henle liquid enters the medulla, and water diffuses into capillaries, concetration of sodium ions hits its max at the bottom of the loop
- the ascending loop of Henle, water isn't permeable and ions diffuse into blood vessels

step 3 of urine production: tubular reabsorption

- in the distal tubule (also apart of tubule reabsorption)
- K+ and H+ are secreted into the distal tube to maintain pH
- regulated by hormones

step 4 of urine production: water reabsorption

- occurs in collecting tube/duct
- passive reabsorption of water by osmosis
- if a person is dehydrated, the permeability of the duct is increased, therefore giving more water back to the body

permeability of distal tubule & collecting duct is controlled by...

- ADH (antidiuretic hormone)
- when body needs to eliminate excess water, ADH is inhibited
- drug, alcohol, and caffeine block the release ADH

Low blood pressure (kidneys)

- detected by juxtaglomerular apparatus which releases the enzyme renin which causes angiotensin to be released

angiotensin

constricts blood vessels and activates aldosterone

aldosterone

acts on nephrons to increase Na+ causing the osmotic gradient to increase

kidneys & pH balance

-Kidneys can secrete more H+ ions and reabsorb more bicarbonate when pH is low

vise-versa when it is high
-Slower than respiratory response, but highly effective

kidney and sugar levels

- kidneys reabsorb sugar from the blood as it is filtered
- when sugar is too high, kidney is unable to filter sugar and it is passed to urine

insulin

- hormones that causes the cells of the muscles, liver and other organs to become permeable to glucose
- triggers cells to increase rate of glucose transport into the cells for use

glucagon

- promotes the conversion of glycogen to glucose, which is released into the blood
- deals with the lack of glucose
- causes the breakdown of glycogen stored in the liver

yype I diabetes

an autoimmune disorder characterized by lack of insulin production by the beta cells of the pancreas

type II diabetes

type of diabetes in which the body produces insulin but the insulin cannot be used by body cells

pancreas

- digestive gland that secretes pancreatic juice to small intestine and insulin to the blood stream
- produces hormones and enzymes in islets of Langerhans
- has two cell types α and β

β cells

- produces insulin (when glucose ↑)
- makes cells more permeable to glucose, therefore, blood glucose decreases in liver, glucose is turned into glycogen (storage)

α cells

- produce glucagon (when glucose ↓)
- causes blood glucose to increase as glycogen is converted from the liver

osmotic pressure

- the pressure that reuslts from a difference in solute concentration between the two sides of a selectively permeable membrane
- the greater the gradient, the greater the osmotic pressure difference

hyperosmotic

- the property of the solution on one side of a selectively permeable membrane that has the lower concentration of water
- water tends to move to the hyperosmotic side

hypoosmotic

- the property of the solution on one side of a selectively permeable membrane that has the higher concentration of water
- water tends to move from the hypoosmotic

osmoregulation

- the process of actively regulating the osmotic pressure of bodily fluids and cells

how do simple organisms expel water

- they use contractile vacuoles that pump water out to maintain balance

how do more complex single organisms expel waste

- they have organs called metanephridia which reabsorbs and eliminates waste

how do insects expel waste

- malpighian tubules
- closed ends are immersed in hemolymph, and open ends empty into the intestines

hormone regulation

- hypothalamus recieves signals from various sensors in the body and releases 'releasing hormones' which stimulate pituitary gland

tropic hormones

- hormones that stimulate endocrine glands to release other hormones
- most hormones released from hypothalamus and pituitary gland

steroid hormones

- lipid-based
- can easily diffuse though the lipid bilayer and binds inside the cells
- binding causes change in the cell

protein hormones

- water-soluble, cannot diffuse through the membrane
- hormones bind to receptor protein on the surface of the cell which causes reactions inside the cell

pituitary gland

- pea sized gland located at the base of the brain, control other endocrine glands
- two lobes posterior and anterior

posterior pituitary

- nervous system, stores hormones made by hypothalamus (ADH and oxytocin)
- fast and direct

anterior pituitary

- hormone production of 6 major hormones that the hypothalamus either stimulates or inhibits release
- makes hormones that act on other structures on the body

thyroid gland produces

Thyroxin (T4), triiodothyronine (T3), and calcitonin

T3 and T4

- metabolism regulation
- hydrophobic and get carried by proteins in the blood
- controlled by anterior pituitary lobe TSH (thyroid-stimulating hormone)
- T3 more effective, T4 more abundant
- difference in the amount of iodine in the molecule

calcitonin

- decrease blood calcium and blood phosphate levels (by getting them deposit in the bones, and stimulating the excretion of them)
- calcitonin stops calcium deposits from occurring

hyperthyroidism

- when the thyroid is over active
- high metabolic rate, hyperactivity, sensitivity to heat, protruding eyes, hard time sleeping
- ex. grave's disease

hypothyroidism

- myxedema (found in adults)
- cretinism (found in infants)
- Hashimoto's disease (hypothyroidism due to an autoimmune problem)
- goiter (no T3 and T4 can be made because not enough iodine was ingested)
- mild hypothyroidism

adrenal glands

- found on top of each kidney
- permeable & lots of blood vessels making the susceptible for attack

adrenal cortex

- outer
- glucocorticoids, mineralocorticoids, sex hormones (androgens)

adrenal medulla

- inner
- produces epinephrine and norepinephrine
- stimulated by neurons at times of stress

aldosterone

- produced within the adrenal cortex
- considered a mineralocorticoid (monitors electrolyte levels, adds sodium when levels are low)

aldosterone is controlled by...

- blood plasma ion concentrations affect its secretion directly
- kidney secretes renin in response to altered electrolyte levels, which triggers angiotensin activation in the blood, which leads to aldosterone secretion
- ACTH (adrenocorticotropic hormone) from the anterior pituitary can cause aldosterone secretion

cortisol

- considered a glucocorticoid
- associated with blood glucose levels
- helps to keep blood glucose concentration within a normal range between meals

Gonadotropin-Releasing Hormone (GnRH)

- stimulates pituitary to release FSH and LH
- secreted by the hypothalamus during puberty

Follicle-Stimulating Hormone (FSH)

- stimulates sperm production

Luteinizing Hormone (LH)

- stimulates the production of testosterone

testosterone

- produced by interstitial cells
- stimulates the production of sperm
- maturation of testes, penis, and sex drive
- facial/body hair, lowering of voice, muscles development, secretion of body oils

female reproductive system & hormones

- estrogen and progesterone are involved in the complex female sexual cycle in which one egg matures approximately every 28 days
- estrogen has positive control of the release of LH - signals ovulation
- ovulation (release of egg from follicle)
- corpus luteum (mass of follicle within ovary that releases estrogen and progesterone)
- ovaries (female sex glands that produce estrogen and progesterone)

neurohormones

- a hormone produced by neurons, that controls the production of other hormones in the pituitary gland

two types of neurohormones:

- releasing hormones
- inhibiting hormones

two divisions of the nervous system

- central nervous system
- peripheral nervous system

central nervous system includes

- nerves of the brain and spinal cord
- coordinating centre for incoming and outgoing information

peripheral nervous system includes

- nerves that carry information between the organs of the body and the CNS
- can be further divided into the somatic and autonomic

somatic nervous system

- controls skeletal muscles, bones, and skin
- voluntary control of bones & muscles
- brings information form external environemnt to the CNS

autonomic nervous system

- special motor nerves that control the internal organs of the body
- involuntary, can operate without concious control
- can be subdivided into the sympathetic and parasympathetic systems

afferent neurons

- a neuron that carries impulses from sensory receptors to the CNS
- sensory receptors
- located in clusters outside the spinal cord

efferent neurons

- relay information to the effectors such as muscles, organs, and glands

interneurons

- a local circuit neuron of the central nervous system that relays impulses between afferent and efferent neurons

cell body

- contains nucleus

dendrites

- receive information
- conduct nerve impulses toward the cell body
- parts of the nerve that connects to the chain

axon

- sends nerve impulses from the cell body to other neurons (ex. effectors)
- long tail