U2 AOS2 Biology sac - digestive system and regulation of body temperature (homeostasis)

Define digestive system

the collection of specialised tissues and organs responsible for the breakdown of food and absorption of nutrients

Role of the digestive system

Breaks down and processes food to be used by the body. Eliminates food waste that is not digested via egestion.

physical/mechanical digestion

the breakdown of food into smaller pieces by chewing and peristalsis, increasing surface area for digestion and absorption

chemical digestion

the breakdown of food into small absorbable molecules by digestive enzymes and stomach acid, mainly through hydrolysis reactions involving amylases, proteases, and lipases.

what are the 4 steps of digestion?

ingestion, digestion, absorption, elimination

ingestion

the intake of food into the body, where teeth physically break food into smaller pieces and saliva begins chemical digestion to form a soft mass for swallowing.

digestion

Digestion occurs along the digestive tract, where food moves through the body and is broken down physically and chemically by different organs.

absorption

Absorption occurs when small digested molecules pass through the plasma membrane of digestive tract cells into the bloodstream, where their energy can be used by the body.

elimination

Egestion is the removal of undigested food from the digestive tract, which is eliminated from the body as faeces.

What are they key organs of the digestive system?

mouth, oesophagus, stomach, small intestine, large intestine, liver, pancreas

mouth

Purpose is to mechanically digest food from mastication (chewing) by teeth, churning of food by tongue

• makes food smaller and mixes with salivary amylase to make bolus

oesophagus

Purpose is to push food to stomach by perstalic waves of smooth muscle surrounded by epithepial living

• The oesophagus is a hollow tube that carries swallowed food from the mouth to the stomach by peristalsis, while saliva continues mixing with the food.

stomach

Purpose is to mix food with pepsin - pepsin begins chemical digestion

• The stomach stores and churns food, uses protease enzymes and acidic digestive juices to begin protein digestion, and moves partially digested food (chyme) to the small intestine.

small intestine

produces intestinal juice (this contrains amylase, protease, lipase, mucus)

• vili and microvilli increase surface area - more surface area = more absorption of food

• The small intestine (duodenum, jejunum, and ileum) is the main site of nutrient absorption, where enzymes and bile complete digestion and nutrients are absorbed into the circulatory system.

large intestine

Purpose is to absorb water - water becomes deaces

• The large intestine (cecum, colon, and rectum) absorbs water, vitamins, and minerals, while compacting undigested food into faeces for egestion and containing many bacteria

liver

• filters blood and detoxifies chemicals within blood

• produces bile to physically break down fats

• regulates metabolism

• removes toxins

• processes nutrients

• stores excess glucose as glycogen.

pancreas

• purpose is to secrete pancreatic juice

• produces digestive enzymes released into the small intestine, regulates blood sugar levels, and secretes bicarbonate to neutralise acidic chyme.

what is the role of amylase?

a digestive enzyme that breaks down carbohydrates such as starch into smaller sugar molecules

what is the role of protease

a digestive enzyme that breaks down proteins into smaller peptides and amino acids

what is the role of lipase

a digestive enzyme that breaks down lipids (fats) into fatty acids and glycerol

structure of the digestive system in herbivores - link to diet

Herbivores eat plant material containing cellulose, which is difficult and slow to digest. As a result, they have long digestive tracts and high concentrations of gut microbiota to help break down cellulose.

There are two types of herbivore digestive systems:

• Hindgut fermenters — single-chambered stomach and a very large cecum for fermentation

• Foregut fermenters — multi-chambered stomach with fermentation occurring in the large first chamber

Herbivores also have large flat teeth and side-to-side jaw movement for grinding plant material. They graze for long periods to obtain enough energy from their food.

structure of the digestive system in carnivores - link to diet

Carnivores eat meat, which is energy-dense and easier to digest than plant material, so they have relatively short digestive tracts.

They have sharp teeth, including large canine teeth, to rip and tear flesh, and their jaws move up and down for chewing. Although carnivores still contain gut microbiota, less fermentation is needed compared to herbivores.

Food is exposed to acid in the stomach, most nutrient absorption occurs in the small intestine, and the large intestine reabsorbs water.

structure of the digestive system in omnivores- link to diet

Omnivores eat both plant and animal material, so they have digestive systems adapted for a varied diet.

They have both sharp and blunt teeth for tearing meat and grinding plant material. Omnivores also contain gut microbiota, especially in the large intestine.

In humans, food moves from the stomach to the tightly folded small intestine for absorption, then through the large intestine before elimination.

what cells do hormones affect?

cells with the correct receptor

what is the role of glands?

to produce and release hormones

define homeostasis

maintaining internal conditions within set limits

why are stable conditions required for cell function?

Homeostasis maintains stable internal conditions so cells and enzymes can function properly within a narrow range of conditions, such as temperature, pH, blood glucose, ion concentration, and fluid balance, despite changes in the external environment.

5 components of the stimulus response model

stimulus, receptor, modulator, effector, response

define stimulus

a change in the internal or external environment of an organism that can initiate a response

define receptor

a structure that detects a signal or external change, usually a protein

define modulator

location where information from receptors is sent to and compared to a set point, and where molecules altering the functioning of an effector are released

define effector

a molecule, cell, or organ that responds to a signal and produces a response

define response

the action of a cell, organ, or organism caused by a stimulus

what is negative feedback?

a stimulus–response process in which the response counters the stimulus

• used in homeosatasis - the response counters the stimulus to return conditions back to the set point, which is the normal value the body aims to maintain

what is positive feedback?

a stimulus–response process in which the response increases the stimulus

• not apart of homeostasis

difference between negative and positive feedback

Negative feedback is a stimulus–response process where the response counters the stimulus to return the body to its set point, maintaining homeostasis, while positive feedback increases the stimulus and does not maintain homeostasis.

what type of feedback does homeostasis use?

negative feedback

what are the 3 stages of cell signaling?

reception, transduction, response

what are the 4 methods of heat transfer?

conduction, convection, evaporation, radiation

conduction

the transfer of heat through physical contact with another object

convection

the transfer of heat via the movement of a liquid or a gas between the areas of a different temperature

evaporation

the loss of heat via the conversion of water from liquid to gas form

radiation

the transfer of heat via electromagnetic waves (like light)

• doesn’t require physical contact with another object

What are 3 responses to increases body temperature and how does these responses reduce body temperature? - apart of negative feedback thermoregulation

1. Sweat glands produce sweat which evaporate from the skin taking heat energy with it

2. the cerebral cortex causes changes in behaviour, such as seeking shade or removing a layer of clothing

3. small blood vessels in the skin vasodilate, increasing surface blood flow, heat lost to the environment via convention and conduction is increased

What are 3 responses to a decrease in body temperature and how does each response increase body temperature? - apart of negative feedback thermoregulation

1. the cerebral cortex causes changes in behaviour, such as putting on more clothing

2. small blood vessels in the skin constrict (vasoconstriction) decreasing surface blood flow, meaning that less body heat is lost to the environment

3. skeletal muscles are stimulated to cause shivering, a process in which muscle cells are stimulated increasing their metabolism and creating more heat energy

define endotherm

an animal that produces the majority of its own heat via metabolic processes

define ecotherm

an animal that obtains heat primarily from the environment, rather than its own metabolic heat

similarities of endotherm and ecotherm

Both endotherms and ectotherms are animals that obtain heat from both internal metabolic processes and the external environment to regulate their body temperature.

differences of endotherm and ectotherm

Endotherms mainly generate heat internally through metabolic processes, while ectotherms rely primarily on external environmental sources of heat to regulate their body temperature.

define excretory system

the collection of organs and tissues that removes excess fluid and waste minerals from the body

role of the excretory system

Removes waste substances from the blood via excretion. Also assists in the control of water balance in the body.

define endocrine system

the collection of glands in animals responsible for producing hormones that can be transported in the blood stream to regulate distant organs/cells

role of the endocrine system

Responsible for the production and secretion of hormones which control and regulate bodily processes.

cellular signalling - reception

the detection of a stimulus and the transmitting of this stimulus into a mechanical, electrical, or chemical signal

cellular signalling - transduction

the transmission of a signal during cellular signalling

cellular signalling - response

the change in the function of a target cell, organ, or organism