IB Bio HL Year 2

Homeostasis

Homeostasis

is the biological state of equilibrium that results from many different processes. Cells are able to respond to changes in order to maintain this balance.

• Voluntary vs. involuntary actions → this is involuntary, the body does it naturally.

steps to return to homeostasis

Start out at balance. Imbalance when (1) stimulus produces change in variable

2. receptors detect change

3. input: information sent along the afferent pathway to the control center (brain)

4. output: information sent along the efferent pathway to the effector (response for what happened)

5. response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level.

hormones

chemical signals used to regulate cell activity throughout the body. There is a wide variety of hormones, each having an effect on different organs or tissues.

• secreted directly into the blood

• carried to target tissues (place of intended action)

• change is monitored by feedback

endocrine system

a set of glands that release hormones that regulate all biological processes in the body

• The development of the brain and nervous system

• The growth and function of the reproductive system

• Control of metabolism and blood sugar

most hormonal changes result in…

negative feedback loop (tell the body to slow down)

Negative feedback loop (ex: sweating)

A negative feedback loop occurs in biology when the product of a reaction leads to a decrease in that reaction. In this way, a negative feedback loop brings a system closer to a target of stability or homeostasis.

• ex: sweat is thermal regulation and a negative feedback loop. Stimulus = feeling too hot, sweat decreases your temperature and ends with lowered body temperature

• antagonistic response

Hypothalamus

• controls many homeostatic processes including hunger, thirst, and temperature.

• Secretes hormones to regulate other glands including the pituitary gland.

• Links in the nervous and endocrine systems.

• NOT A GLAND

Pituitary Gland

master gland, the pituitary is important in controlling growth and development and the functioning of the other endocrine glands

• Oxytocin (uterus contractions in labor, ejection of milk in breasts)

• regulates water intake by kidneys

• secretes FSH and LH

  • Follicle-stimulating hormone and Luteinizing Hormone

  • secreted and releases estrogen or testosterone so the lining of the uterus thickens (no fertilization = menstrual cycle)

Thyroid

produces hormones that regulate metabolism and temperature - produces Thyroxin

Positive feedback loop

stimulating response in which there is a stimulus, a signal is released, and there is a response

Leptin

A hormone secreted by fat cells in adipose tissues. It targets cells in the hypothalamus and helps control appetite. When food is eaten, leptin increases which inhibits hunger.

• Increased levels of leptin can result in resistance to the hormone making appetite hard to control.

• Lack of leptin can also cause obesity because no hunger control

Adrenal glands

• Produces adrenaline (aka epinephrine) and provides the ‘fight or flight’ for stress

• There are two, one on each kidney (could be the case of another added)

• Epinephrine dilates blood vessels in response to stress and is released by adrenal glands

4 parts of control of blood sugar levels (glucose, insulin, glucagon, glycogen)

• Glucose = used for energy

• Insulin = hormone released by the pancreas (beta cells) tells cells to uptake glucose, released when glucose levels high

• Glucagon = hormone released by the pancreas (alpha cells) tells cells to release stored glucose (glycogen), released when glucose levels are low

• Glycogen = stored form of glucose, long chains of glucose molecules (= polymer. Goal is to break down into monomer to ingest and use properly→ the pancreas breaks it down)

After a meal (blood sugar is high)

(1) glucose from food enters the bloodstream.

(2) blood glucose concentrations rise above the threshold.

(3) beta cells in the pancreas synthesize and secrete insulin into the bloodstream.

(4) Insulin attaches to receptor cell so glucose channels open the glucose enters (adipose, muscle, and skeletal cells for conversion into ATP); At high levels makes the liver convert extra glucose into glycogen for future use.

(5) decrease in the concentration of glucose in the blood and return to stable conditions = NEGATIVE feedback loop

After exercise (blood sugar is low):

(1) glucose in muscle, adipose, & liver cells is converted & used as ATP

(2) Blood glucose levels drop below threshold

(3) alpha cells of pancreas synthesize and secrete glucagon into the bloodstream

(4) Glucagon hormone stimulates breakdown of stored glycogen to glucose in liver cells

(5) glucose is released in the bloodstream and blood glucose levels return to stable conditions

what is diabetes? what are the two types?

• when feedback mechanisms are unable to maintain conditions, diseases such as diabetes mellitus can result

• Diabetes Mellitus = metabolic disorder result persistent high blood glucose levels

  • Type 1: autoimmune disorder where beta cells are attacked, failure to produce insulin. Treatment = insulin injections

  • Type 2: deficiency of insulin receptors due to poor diet and lack of exercise, adult-onset diabetes (often >65 years old). Treatment = control what eat in relation to CO2

Type 1 diabetes IDDM (Insulin-Dependent Diabetes Mellitus)

* usually occurs during childhood (early onset)

* body does not produce sufficient insulin

* caused by the destruction of beta cells (autoimmune)

* requires insulin injections to regulate blood glucose

*autoimmune disorder where beta cells are attacked, failure to produce insulin

Type II Diabetes NIDDM (Non-Insulin-Dependent Diabetes Mellitus)

* usually occurs during adulthood (late onset)

* body does not respond to insulin production

* caused by the down-regulation of insulin receptors

* controlled by managing diet and lifestyle

*deficiency of insulin receptors due to poor diet and lack of exercise

Pineal Gland

releases hormones that regulate sleep cycles → affects circadian rhythms (internal clock that regulates when you need to sleep)

melatonin

Melatonin

• hormone that makes you sleep

• Body already makes it so you are used to receiving it.

• It controls the body’s circadian rhythms which is a 24-hour cycle.

• Its secretion increases in the evening and decreases at dawn, allowing it to control our sleep-wake cycle.

Testes (Endocrine system)

• testosterone

• secondary sex characteristics

• sperm production

• in scrotum

Ovaries

• produce estrogen and progesterone

• secondary sex characteristics

• maintaining the endometrium lining

Functions of exocrine and endocrine glands in pancreas

• exocrine gland = associated with a duct, secretes enzymes that help digestion

• Endocrine gland = ductless, secretes hormones to regulate blood sugar levels

Thyroxine

• Overall: Regulates metabolism and body temperature, produced in thyroid gland

• Activates nuclear transcription of lots of genes for synthesis and transport of enzymes/proteins

• = It causes an increase in metabolic activities of almost all tissues of the body which also raises body temperature

• Effects:

  • increased rate of utilization of food for energy

  • increased breathing rate to obtain oxygen to get rid of carbon dioxide

  • increased rate of protein synthesis and catabolism

  • increased amount and size of mitochondria in most cells

  • the increased growth rate of children and adolescents

  • growth of development of the brain (fetuses and 1st few years)

  • enhanced carbohydrate and fat metabolism

Excretion

• Excretion is the removal from the body of waste products of metabolism

  • We don’t consider defecation as excretion bc feces is not the waste product of metabolism - it is undigested food

  • Excretion is getting rid of MOLECULES that the body already processed and used and may not need it anymore

• Excretory system = urinary systemKid

Kidney

• cleans the blood and creates urine (blood waste) through filtration.

• Filtration removes nutrients and molecules that the body can’t or doesn’t need to use anymore.

Inferior vena cava (urinary system)

takes clean “filtered” deoxygenated blood to the heart. Also attached to the heart.

Abdominal Aorta

brings blood from the heart and brings “dirty” or unfiltered blood to the kidney.

Urinary Bladder

collects and stores urine.

Urethra

connects the bladder to the outside world, how urine leaves the body

Urethral Orifice

the opening where urine is released

Adrenal Glands (urinary system)

produces hormones to regulate blood pressure, epinephrine, metabolism, etc. waste through filtration

Renal Artery

supply kidney with dirty unfiltered blood

Renal Pelvis

funnels urine to ureters

Renal Vein

comes from the kidney, joins vena cara, transports clean blood ‘filtered’ to the heart

Ureter

tubes that carry urine from the kidney to the bladder

Nephron and Filtration steps

(1) ultrafiltration → bowman’s capsule, urea, salt, water, and glucose are taken out and we retain blood (red, white, proteins) by high-pressure change in areola size

(2) selection reabsorption → proximal convoluted tubule. Amino acids, glucose, vitamins, and hormones along with 80% of water and ions are reabsorbed via passive diffusion into the bloodstream and co-active transport.

(3) osmoregulation → medulla or loop of henle.

• Descending loop: permeable to water, impermeable to Na+

• Ascending loop: impermeable to water, permeable to

• To recover water and NaCl from urine limits the amount of water

Macromolecules

• an important cellular component that performs a wide array of functions necessary for the survival and growth of living organisms

• 4 Major classes of biological macromolecules:

  • carbohydrates (sugars)

  • lipids (fats, oils, waxes, saturated/unsaturated, steroids)

  • proteins (meat, nuts, legumes - amino acids that help build muscle mass)

  • nucleic acids (DNA, RNA)

facts about macromolecules Carbohydrates, Lipids, Protiens, Nucleic Acids

• Carbohydrates

  • Fast source of energy (fast)

  • Monomer = monosaccharide

  • CHO

• Lipids

  • Fats: monomers: fatty acids and glycerol

  • Many functions: insulation, long term source of energy, make up some energy

  • I swim with the spirit of potato chips

  • CHO

• Protiens

  • Muscle building/development, immune system, acting as enzymes, MANY functions

  • DNA codes for proteins

  • Monomer = amino acids

  • CHON

• Nucleic Acid (DNA, RNA)

  • Monomer = nucleotide

  • Involved in coding of your traits

  • CHONP

Alimentary Canal

• primary organs where food travels through digestion actually occurs

• oral cavity, esophagus, stomach, and intestines

• tissue layers form walls of the canal and propels substances through your body by expanding and contrasting = peristaltic wave

Secondary organs (digestive system)

(gallbladder, liver, pancreas) - release enzymes, aid, and release chemicals that help with digestion

Salivary glands

have amylase → breaks down carbohydrates

3 locations- by jaw, mouth, and ear

Liver

uses bile. Gallbladder stores bile until it is time to be released

Large intestines

reabsorption of the excess water

Stomach

Hydrochloric acid (NOT an enzyme)

Protease (enzyme breaks down proteins)

Pepsin (also enzyme that breaks down proteins specifically in the stomach)

type of digestions:

• mechanical has churning wave-like

• chemical with HCl and enzymes in the stomach (pepsin)

Pancreas

Digestive system: Protease, Lipase (enzyme breaks down lipids), some amylase

Endocrine system: helps with blood sugar control - controls the secretion of insulin and glucagon

How are carbohydrates broken down

• Amylase (salivary and pancreatic): starch → maltose

  • Maltase: maltose → glucose and glucose (small intestine)

  • Lactase: Lactose → glucose and galactose (small intestine)

  • Sucrase: sucrose → glucose and fructose (small intestines)

Proteins break down

• Protease is a general term but depends on what kind of protein as to what type of enzyme it binds with and breaks down

• Pepsin in the stomach and Trypsin in small intestines

• Dipeptidase (and peptidase?) are in the pancreas, small intestines, etc. Dipeptides → single amino acids (some in small intestines)

• HCL is NOT AN ENZYME but it does help break down proteins

Small intestines

Trypsin breaks down protiens and peptides

Maltase, Lactase, and Sucrase break down maltose (glucose and glucose), lactose (glucose and galactose) and sucrose (glucose and fructose)

How are lipids broken down?

Lipase - breaks down lipids into small components found in mouth, pancreas, and stomach: not necessarily chemical process (more mechanical)

Mechanical and chemical digestion

• Digestions = turning food into components so we can absorb calories, nutrients, vitamins, and minerals

• (1) mouth and teeth = mechanical digestion because physical breakdown of food into smaller pieces; stomach muscles in stomach keep breakdown.

• Break into smaller molecules that can be absorbed into the bloodstream

Bile (where, type of digestion)

produced by the liver, stored in the gallbladder

Converts fats into Globs (for an easier breakdown in the intestines)

Mechanical (NOT chemical because not changing the state/condition of the fat)

what type of digestion is in the mouth

mechanical: chewing and tongue

chemically: saliva releases amylase to break down carbs

Food, Bolus, Chyme

• Food enters the mouth, intact

• Bolus leaves the mouth down the esophagus and enters the stomach as a ball of food

• Chyme leaves the stomach as a pulpy acidic fluid which passes from stomach to the small intestine as gastric juice and partially digested fluid

Digestion

breakdown of food/the polymer mechanically and chemically into monomers so that we can use them in our body so absorption can happen → then can go to cells in a process called assimilation

where is the final stage of digestion

Duodenum (first part of the small intestine)

Absorption

• digested food products are absorbed into the bloodstream and transported to cells

• takes place in the small intestine so surface area available for more absorption.

• The rate of absorption depends on the surface area available.

• Food monomers broken down by proteins in the stomach and small intestine that are located in small intestine go through the semi-permeable wall of the small intestine into the bloodstream

Assimilation

• when digested food products are converted into the fluid and solid parts of a cell occurs after absorption

• what can cause less surface area and impact assimilation?

  • Ulcer - from stress, eats away at cell wall = causes less surface area

  • Polyps - can grow back and take away surface area from small intestines

  • Or from gene mutation

Peristalic wave

tissue layers form walls of the Alimentary canal and propels substances through your body by expanding and contrasting

a wave of muscle contractions that push food through the gut and mix it with enzymes → pushes it forward and prevents it from going backward

Small intestines function and parts

• Made up of duodenum, jejunum, and ileum

• Helps further digest food coming from the stomach

• Absorbs nutrients (vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be used by the body

Villi

• finger-like projections of mucosa that are found on the inside of the intestine wall.

• They increase the surface area by a factor of 10

• 3 parts of villi: thin epithelium, blood capillary, lacteal

Serosa

the outermost layer of the intestines (layer 1 of intestines)

a smooth membrane consisting of a thin layer of cells that secrete solid fluid and a thin layer of connective tissue

Muscularis

• Layer 2 of intestines

• responsible for gut movement (peristalsis)

  • Longitudinal - pushes in front of the food

  • Circular - pushes behind the food

Submucosa

Connective tissue that supports the mucosa, also joins the mucosa to the bulk of underlying smooth muscle

3rd layer of intestines

Mucosa (part of intestines)

innermost tissue layer of the small intestines and is a mucous membrane that secretes digestive enzymes and hormones.

The intestinal villi are part of the mucosa

Villi parts

• Thin epithelium: with small microvilli increase surface area for absorption. One cell thick to increase diffusion rate

• Blood capillary: absorption of glucose and amino acids (capillary is where red and blue blood vessels come together)

• Lacteal: absorbs fatty acids and glycerols (these are tiny lymphatic vessels) → lymph nodes swell if you are sick sometimes