SACE Stage 2 Biology: Homeostasis

Homeostasis

The ability of a body to maintain a stable internal environment

Tolerance Limits

The points just before an organism cannot survive due to environmental conditions.

Tolerance Range

The range between the minimum and maximum tolerance limits

What are some examples of tolerance limits?

Body temperature, water availability, blood glucose levels, carbon dioxide dissolved

Negative Feedback

The response reverses the stimulus

The Stimulus Response Model

Stimulus, sensory receptor, messenger, effector, response

Central Nervous System

Brain and spinal chord

Peripheral Nervous System

Peripheral nerves

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Cell Body

contains nucleus

Axon

At the opposite end of the nerve cell body. It is a long, thin fibre with branches at the end

Myelin Sheath

insulating membrane surrounding the axon in some neurons

Sensory Neuron

Long dendrite, short axon, cell body found outside the spinal cord

Interneurons

Short dendrite, short axon, entirely within CNS

Motor Neuron

Short dendrite, long axon

Synapses

The site of transmission of electric nerve impulses between two nerve cells

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

How does the neurotransmitter leave the axon?

Exocytosis

Hormones

chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues

Steroid Hormones

Lipids which are hydrophobic. Receptors inside the cell.

Peptide/Protein Hormones

Hydrophilic, in the plasma membrane

Amino Acid Derived Hormones

Hydrophilic, found on the surface

Stimulus for CO2 Regulation

Change in pH

Receptor for CO2 Regulation

Chemoreceptor cells in the medulla oblongata

Messenger for CO2 Regulation

Messages send via neurons to respiratory centre in CNS

Effector for CO2 Regulation

Diaphragm and Intercostal Muscles

Response for CO2 regulation

Breathing control

Negative effects for disruption of pH

Kidney disease, enzyme denature

Receptor for Glucoregulation (increase in glucose)

Beta cells in pancreas

Receptor for Glucoregulation (decrease in glucose)

Alpha cells in pancreas

Effectors for Glucoregulation (increase in glucose)

Beta cells produce and release insulin into blood stream

Effectors for Glucoregulation (decrease in glucose)

Alpha cells produce and release glucagon blood stream

Response for Glucoregulation (increase in blood glucose)

Insulin stimulates the uptake of glucose into liver and its storage at glycogen

Response for Glucoregulation (decrease in blood glucose)

Glucagn stimulates the conversion of glycogen in liver to glucose and its release into the blood

Effects of High Glucose &/or Low Insulin

Type 1 or Type 2 diabetes

Type 1 Diabetes

Antibodies destroy cells in the pancreas that produce insulin

Type 2 Diabetes

The body cells become resistant to the effect of insulin

Osmoregulation

Refers to the control of water levels in the blood

High Water Content

Low Osmolarity

Low Water Content

High Osmolarity

Receptor in Osmoregulation

Osmoreceptors in hypothalamus

Message in Osmoreguation (increase in water levels)

Nervous message from hypothalamus to pituitary gland to decrease ADH production which binds to kidneys

Message in Osmoregulation (decrease in water levels)

Nervous message from hypothalamus to pituitary gland to increase ADH production which binds to kidneys

Effectors in Osmoregulation (decrease in water levels)

Tubules and collecting duct found in the kidneys results in a decrease in the amount of water removed from the filtrate

Effectors in Osmoregulation (increase in water levels)

Tubules and collecting duct found in the kidney - results in an increase in the amount of water removed from the filtrate

Decrease in Osmolarity causes...

An increase in ADH causes an increase in the amount of water removed from the filtrate. This increases the amount of water taken into the blood and reduces the solute concentration of the blood.

Increase in osmolarity causes...

A decrease in ADH causes a decrease the amount of water removed from the filtrate. This decreases the amount of water taken into the blood and increases the solute concentration of the blood.

Thermoregulation effectors

Muscles, sweat glands, thyroid gland, adrenal gland

Thermoregulation Receptor

Skin and hypothalamus

Message in Thermoregulation

Nervous and hormonal: nervous to CNS, nervous to sweat glands and adrenal glands, hormonal to thyroid gland

Effector in Thermoregulation (increase in body temp)

Sweat glands begin release of sweat, adrenal glands decrease adrenalin, thyroid gland decreases thyroxin

Metabolism

Biochemical reactions occurring within cells.

Rate of metabolism controls...

Heat production and functioning of cells

Thyroxin

Controls rate of metabolism

Thyroid Stimulating Hormone

Produced by the pituitary gland, control the levels of thyroxine produced by the thyroid gland

Production of thyroxine

Monitored by both the hypothalamus and pituitary gland

Flight or Fight response

Response is a protective mechanism which enables an organism to react quickly

Effects of Adrenaline

Heart rate increases, blood pressure increases, increased metabolic rate, pupil dilation, increased blood glucose

Adrenaline

Increases oxygen exchange with the blood and increases circulation of oxygen to the cells for aerobic respiration which provides the cells with increased levels of ATP

Glucagon

Binds to liver cells and stimulates cells to convert glycogen to glucose

Insulin

Binds to liver cells and stimulates the uptake of glucose and conversion glycogen

Hypotension

Low water levels

Hypertension

High water levels

Nephrons

Which act to filter out excess water and unwanted substances. It also allows for the reabsorption of water back into the blood from the tubules

Aquaporins

Channel proteins which facilitate the rapid movement of water