homeostasis and reaponse

Homeostasis

"The maintenance of a constant internal environment despite external changes."

Internal conditions controlled

"Temperature

Negative feedback

"A process where a change triggers a response to reverse the change and restore balance."

Nervous system

"Network of nerve cells transmitting electrical impulses around the body."

Central nervous system (CNS)

"Brain and spinal cord; processes information from sensory neurons."

Sensory neuron

"Carries impulses from receptors to CNS."

Motor neuron

"Carries impulses from CNS to effectors (muscles/glands)."

Relay neuron

"Connects sensory neuron to motor neuron within CNS."

Reflex action

"Rapid

Reflex arc steps

"Receptor → sensory neuron → CNS (relay neuron) → motor neuron → effector."

Advantage of reflexes

"Quick response without conscious thought

Endocrine system

"Glands that secrete hormones into the blood to regulate processes."

Hormone

"Chemical messenger carried by blood to target organs."

Target organ

"Organ that responds to a particular hormone."

Pituitary gland

"‘Master gland’ controlling other glands and growth."

Thyroid gland

"Releases thyroxine to regulate metabolism

Adrenal gland

"Produces adrenaline for ‘fight or flight’ response."

Pancreas

"Produces insulin and glucagon to regulate blood glucose."

Insulin

"Hormone that lowers blood glucose by stimulating uptake into cells and conversion to glycogen in liver."

Glucagon

"Hormone that raises blood glucose by converting glycogen back to glucose."

Type 1 diabetes

"Pancreas produces little or no insulin; treated with insulin injections."

Type 2 diabetes

"Body cells do not respond to insulin; controlled by diet

Kidneys

"Organs that filter blood

Urea

"Toxic waste product from protein breakdown."

Ultrafiltration

"Process in kidney where blood under pressure forces water and small molecules into Bowman's capsule."

Selective reabsorption

"Process in kidney tubules where useful substances like glucose and ions are reabsorbed."

Osmoregulation

"Control of water and ion balance by the kidneys."

ADH

"Hormone controlling water reabsorption in kidney tubules."

Dehydration effect

"High ADH → more water reabsorbed; urine concentrated."

Overhydration effect

"Low ADH → less water reabsorbed; urine dilute."

Temperature regulation

"Maintaining core temperature around 37°C."

Too hot responses

"Sweating

Too cold responses

"Shivering

Negative feedback example

"Blood glucose rises → pancreas releases insulin → glucose stored as glycogen → blood glucose falls."

Another negative feedback example

"Blood glucose falls → pancreas releases glucagon → glycogen converted to glucose → blood glucose rises."

Control of blood water content

"Kidneys adjust water reabsorption; thirst increases if dehydrated."

Control of blood ion content

"Excess ions excreted in urine; ion shortage conserved."

Hormonal coordination of menstrual cycle

"FSH stimulates egg maturation; LH triggers ovulation; oestrogen and progesterone regulate uterus."

FSH

"Follicle Stimulating Hormone; causes egg to mature in ovary."

LH

"Luteinising Hormone; triggers ovulation."

Oestrogen

"Produced by ovary; inhibits FSH; repairs and thickens uterine lining."

Progesterone

"Maintains uterine lining after ovulation."

Contraception hormones

"Oestrogen and/or progesterone used to prevent ovulation."

Other contraception

"Barrier methods (condoms)

Adrenaline effects

"Increases heart rate

Thyroxine effect

"Controls basal metabolic rate and growth."

Auxins (plants)

"Plant hormones controlling growth; cause phototropism and gravitropism."

Required practical: reaction time

"Measure effect of factors on human reaction time (ruler drop test)."

How to reduce bias in reaction time practical

"Same person repeats test multiple times; average results; standardise conditions."

Brain regions

"Cerebral cortex (conscious thought)

Spinal cord role

"Transmits impulses to/from brain and controls reflexes."

Eye structure

"Cornea

Iris reflex

"Controls pupil size in response to light intensity."

Lens accommodation

"Lens changes shape for focusing on near or distant objects."

Focusing on near objects

"Ciliary muscles contract

Focusing on distant objects

"Ciliary muscles relax

Type 1 diabetes treatment

"Insulin injections; monitor diet and exercise."

Type 2 diabetes treatment

"Lifestyle changes; drugs to improve insulin sensitivity or reduce glucose absorption."

Kidney dialysis

"Artificial removal of waste products and excess water from blood."

Homeostasis importance

"Maintains stable conditions for enzyme function and cell survival."

Reflex vs conscious response

"Reflex is rapid

Hormonal vs nervous coordination

"Hormones slower