Biology 5

Homeostasis= regulation of internal conditions of cell/ organism 

-to maintain conditions (respond to internal & external changes)

Human body controls (involves nervous response/ chemical response):

-blood glucose conc

-body temp

-water levels

Control systems:

-Cells called receptors (detect stimuli ---> change in environment)

-coordination centres (brain, spinal cord & pancreas) recieve & process info from receptors

-effectors, muscles & gland (bring about response ---> restore to optimum levels

Nervous system enable human to react & coordinate surrounds & behaviour

Info from receptors --> neurones (as electrical impulses---> CNS

CNS= coordinate response of effectors

stimulus --> receptor --> coordinator --> effector --> response

Reflex actions= automatic & rapid (no conscious part of brain)

Reflex arc:

-sensory neurone

-synapse

-relay neurone

-motor neurone

Brain- controls complex behaviour

-made of millions of interconnected neurones

-different regions = different functions

Parts of brain:

-cerebral cortex

-cerebellum

-medulla

Neuroscientist map regions of brain to function (by studying patients with brain damage)

-uses electrically stimulating parts of brain & MRI scanning

Complexity & delicacy of brain= difficult to investigate & treat brain disorders

Eye= sensory organ with receptors sensitive to light intensity & colour

Structure of brain:

-Retina                                                                     -Optic nerve

-scelera                                                                     -cornea

-iris                                                                            -cilliary muscles

- suspensory ligaments

To focus near ( cillary muscles contract, suspesory ligaments loosen lens thicker & light rays refract strongly)

Defects= myopia (short sighted) & hyperopia (long sighted)--> light rays don't focus on retina

-Treated with spectacle lenses(refract light rays= focus on retina)

-Hard or soft contact lenses, laser surgery (change shape of cornea)

Thermoregulatory centre (in brain)= monitor & control body temp

-contains receptors (sensitive to temp of blood)

Skin(contain temp receptors & send impulses to thermoreg centre)

Body temp high --> vasodillation

-produces sweat (produced in sweat glands)

-transfer energy from skin to enviroment

Body temp low --> vasoconstriction

-sweating stops

-skeletal muscles contract (shiver)

Endocrine system= composed of glands (secrete hormones into bloodstream)

-blood carries hormone to a target organ --> produces effect

-effects are slower than nervous system

Pituitary gland (master gland)=secretes several hormones into blood in response to body conditions

-hormones act on other glands (stimulate other hormones to bring effect)

Parts of the body

-pituitary gland                                         -adrenal gland

-pancreas                                                 -ovary

-thyroid                                                     -testes

Blood glucose conc= monitored & controlled by pancreas

Glucose high --> pancreas produce insulin (gluc move from blood into cells

-Liver &muscle cells excess glucose -->glycogen

Type 1 diabetes= pancreas fails to produce enough insulin

-uncontrolled high levels of gluc (treated with insulin injections)

Type 2 diabetes= body cells no longer respond to insulin (obesity= risk factor)

-treated with carbohydrate controlled diet & exercise regimen

Glucose low--> pancreas produces glucagon--> causes glycogen to convert into glucose (blood)

Water leaves body through lungs (exhalation)

Water, ions & urea lost through skin (sweat)

-no control over water= loss or gain of water (osmosis)--> cells don't work properly

-excess removed via kidney (urine)

Proteins=excess amino acids--> liver deaminates it= ammonia (toxic--> converted to urea= safe)

Kidneys produce urine (via filtrations of blood, reabsorption of useful substances, ions & water)

Water levels conntrolled by ADH (acts in kidney tubules)

-ADH released from pituitary glands when blood is too concentrated= water reabsorbed (controlled by negative feedback)

Kidney failure treated with organ transplant or dialysis

Puberty causes reproductive hormones --> secondary sex characteristics develop

Oestrogen= female reproductive hormone (produced in ovary)

Eggs mature & one released (every 28 days)= ovulation

Testosterone= male reproductive hormone (produced in testes) stimulates sperm production

Menstural cycle (hormones):

-FSH= maturation of egg in ovary

-LH= stimulates release of the egg

-oestrogen & progesterone= maintain uterus lining

Fertility controlled by hormonal or non-hormonal contraceptives

-oral contraceptive= hormones inhibit FSH production (no egg matures)

-injections, implants  or skin patch= inhibits maturation & release of egg for years/ months

-barrier method (condoms/ diaphragms)= prevent sperm reaching egg

-inauterine devices= prevent implantation of an embryo/ release of eggs

-spermicidal agents= kill/ disable sperm

-abstain from intercourse when egg may be in oviduct

-surgical methods of male & female sterilisation

FSH & LH= fertility drug for women (to become pregnant in a normal way)

IVF treatment:

-mother given FSH & LH to stimulate maturation of several eggs

-eggs collected & fertilised with father's sperm

-fertilised eggs-->embryos

-one or two eggs inserted into mother's uterus

Fertility treatment gives women a chance to have a baby but:

-emotionally & physically stressful

-success rate low

-multiple births= risk to mother & baby

Adrenaline produce from adrenal gland (in times of fear/stress)

-increases heart rate

-boosts delivery of oxygen & glucose to brain & muscles (prep for fight or flight)

-POSITIVE FEEDBACK

Thyroxine produced from thyroid gland

-stimulates basal metabolic rate

-plays role in growth & development

-NEGATIVE FEEDBACK

Plants produce hormones to coordinate & control growth & responses to light & gravity

-unequal distribution of auxin = unequal growth rates

Gibberellins= important for initiating seed germination

Ethene= control cell division & ripening of fruits

Plant hormones used in agriculture & horticulture

Auxins

-weed killers

-rooting powder

-promoting growth in tissue culture

Ethene in food industry (control fruit ripening during storage & transport)

Gibberellins

-end food dormancy

-promote flowering

-increase fruit size