homeostasis and reponse

What is homeostasis?

Maintenance of a stable internal environment

Why is homeostasis important?

Keeps conditions optimal for enzyme function and cellular processes

What is a stimulus?

A change in the environment that triggers a response

What is a receptor?

Cell or organ that detects a stimulus

What is an effector?

Muscle or gland that brings about a response

What is a coordinator?

Brain or spinal cord that processes information and coordinates response

What is the nervous system made up of?

Central nervous system (brain and spinal cord) and peripheral nervous system

What is the function of the central nervous system?

Processes information and coordinates responses

What is a neurone?

Specialized cell that carries electrical impulses

Name the three types of neurone.

Sensory, motor, relay

What is the function of sensory neurones?

Carry impulses from receptors to CNS

What is the function of motor neurones?

Carry impulses from CNS to effectors

What is the function of relay neurones?

Connect sensory and motor neurones in the CNS

What is a synapse?

Gap between two neurones

How do impulses cross synapses?

Neurotransmitters are released and diffuse across the gap

What is a reflex action?

Automatic, rapid response to a stimulus

Why are reflex actions important?

Protect from harm, don't require conscious thought

What is a reflex arc?

Pathway of neurones in a reflex action

What is the order of the reflex arc?

Receptor → sensory neurone → relay neurone → motor neurone → effector

Give an example of a reflex action.

Knee-jerk, blinking, withdrawing hand from heat

What is reaction time?

Time taken to respond to a stimulus

Name factors that affect reaction time.

Age, tiredness, drugs, alcohol, caffeine

How can you measure reaction time?

Ruler drop test, computer reaction test

What is the endocrine system?

System of glands that secrete hormones

What are hormones?

Chemical messengers carried in the blood

How do hormones differ from nervous responses?

Slower, longer-lasting, affect target organs

What is the pituitary gland?

'Master gland' that controls other endocrine glands

What does the thyroid gland produce?

Thyroxine

What does thyroxine control?

Metabolic rate, growth, development

What does the pancreas produce?

Insulin and glucagon

What does insulin do?

Lowers blood glucose levels

What does glucagon do?

Raises blood glucose levels

What is diabetes?

Disease where blood glucose cannot be controlled properly

What is Type 1 diabetes?

Pancreas produces little or no insulin

What is Type 2 diabetes?

Body becomes resistant to insulin

How is Type 1 diabetes treated?

Insulin injections, diet control

How is Type 2 diabetes treated?

Diet control, exercise, sometimes medication

What are the adrenal glands?

Glands above kidneys that produce adrenaline

What does adrenaline do?

Prepares body for 'fight or flight' response

What are the effects of adrenaline?

Increases heart rate, breathing rate, blood flow to muscles

What are the ovaries?

Female reproductive organs that produce oestrogen and progesterone

What are the testes?

Male reproductive organs that produce testosterone

What is negative feedback?

Control system that reverses changes to maintain steady state

Give an example of negative feedback.

Blood glucose regulation, body temperature control

What is the normal human body temperature?

37°C

How does the body respond to being too hot?

Sweating, vasodilation, reduced muscle activity

How does the body respond to being too cold?

Shivering, vasoconstriction, increased muscle activity

What is vasodilation?

Widening of blood vessels near skin surface

What is vasoconstriction?

Narrowing of blood vessels near skin surface

What controls body temperature?

Thermoregulatory centre in the brain

What is the normal blood glucose level?

Around 90mg per 100cm³ of blood

What happens when blood glucose is too high?

Pancreas releases insulin, glucose converted to glycogen

What happens when blood glucose is too low?

Pancreas releases glucagon, glycogen converted to glucose

Where is glycogen stored?

Liver and muscles

What is osmoregulation?

Control of water content in the body

What do the kidneys do?

Filter blood, remove waste, control water balance

What is urea?

Waste product from breakdown of proteins

How is urea removed from the body?

In urine via kidneys

What is ADH?

Anti-diuretic hormone that controls water reabsorption

What happens if you're dehydrated?

More ADH released, more water reabsorbed, less urine produced

What happens if you drink lots of water?

Less ADH released, less water reabsorbed, more urine produced

What is dialysis?

Treatment for kidney failure using a machine to filter blood

What is a kidney transplant?

Surgical replacement of failed kidney with healthy donor kidney

What is the menstrual cycle?

Monthly cycle in females preparing for pregnancy

How long is the average menstrual cycle?

28 days

What is ovulation?

Release of egg from ovary

When does ovulation occur?

Around day 14 of cycle

What is menstruation?

Shedding of uterus lining

What hormones control the menstrual cycle?

FSH, LH, oestrogen, progesterone

What does FSH do?

Stimulates egg development and oestrogen production

What does LH do?

Triggers ovulation

What does oestrogen do?

Builds up uterus lining, inhibits FSH

What does progesterone do?

Maintains uterus lining

What is contraception?

Methods to prevent pregnancy

What is the contraceptive pill?

Contains hormones to prevent ovulation

How does the contraceptive pill work?

Inhibits FSH and LH production

What are barrier methods of contraception?

Condoms, diaphragms - prevent sperm reaching egg

What is IVF?

In vitro fertilisation - fertilisation outside the body

When is IVF used?

When couples have fertility problems

What is fertility treatment?

Hormones given to stimulate egg production

What is the eye?

Sense organ that detects light

What is the cornea?

Transparent layer at front of eye that refracts light

What is the iris?

Coloured part of eye that controls pupil size

What is the pupil?

Hole in iris that lets light through

What is the lens?

Transparent structure that focuses light onto retina

What is the retina?

Light-sensitive layer at back of eye

What is accommodation?

Changing shape of lens to focus on near/far objects

How does the eye focus on near objects?

Ciliary muscles contract, lens becomes more curved

How does the eye focus on far objects?

Ciliary muscles relax, lens becomes less curved

What is myopia?

Short-sightedness - cannot focus on distant objects

What causes myopia?

Eyeball too long or lens too curved

How is myopia corrected?

Concave lens

What is hyperopia?

Long-sightedness - cannot focus on close objects

What causes hyperopia?

Eyeball too short or lens not curved enough

How is hyperopia corrected?

Convex lens

What is the brain?

Organ that controls and coordinates body functions

What is the cerebrum?

Largest part of brain controlling conscious activities

What is the cerebellum?

Part of brain controlling balance and coordination

What is the medulla?

Part of brain controlling unconscious activities like breathing

How is the brain studied?

MRI scans, electrical stimulation, studying patients with brain damage