Topic 5 - Homeostasis and response Flashcards
What is the definition of homeostasis?
Homeostasis:
— The reguation of internal conditions inside the body to maintain a stable internal environment in response to internal and external changes
What are the three main things that homeostasis controls inside the body?
- – Blood glucose concentration
- – Water levels
- – Body temperature
What is the reflex arc?
Stimulus —> receptors which detect stimuli —> sensory neurone —> synapse —> relay neurone in CNS —> synapse —> motor neurone —> effector (muscle or gland) —> response
What are the differences in the responses of the nervous system in comparison to the endocrine system?
Nervous system has fast and automatic responses. Endocrine system has slow responses. The nervous system repsonses act for a short time whereas the endocrine system responses act for a long time. Also the nervous system acts on a specific area whereas the endocrine system acts generally.
What are the functions of the different regions of the brain?
Cerebral cortex:
— Outer part of brain that controls memory, language , consciousness and intelligence
Cerebellum:
— Responsible for muscle coordination
Medulla:
— Responsible for unconscious activities such as breathing, your heartbeat, blinking etc.
What are three methods used to study the brain?
Studying patients with brain damage:
—Doctors look at the patients actions to tell what part of the brain has been damaged as the effects will show.
MRI:
— A detailed picture of the brain is taken using a magnetic resonance imaging scanner. Scientists use it to work out what parts of the brain are active.
Electrically stimulating the brain:
— Scientists electrically stimulate the brain to work out the effect of whatever part they zap with the tiny electrode.
What is the function of each part of the eye?
Lens: focuses light onto the retina
Retina: contains receptors sensitive to light intensity (rod) and colour (cone)
Sclera: tough supporting wall of the eye
Cornea: transparent layer at front of eye that refracts light into the eye
Iris: controls diameter of the pupil and how much light enters
Pupil: the hole in the eye
Ciliary muscles: control shape of lens
Sensory ligaments: control shape of lens
Optic nerve: carries electrical impulses from the receptors on the retina to the brain
How does the eye adapt to bright light and dim light?
When the eye detects a bright light, circular muscles in the iris contracts and the radial muscles relax. This makes the pupil smaller so that not as much light can enter.
When the eye detects a dim light, the circular muscles in the iris relax and the radial muscles contract causing the pupil to dilate and widen to allow more light enter the eye.
How does the eye adapt to focus on near and distant objects?
Near objects:
— Ciliary muscles contract, suspensory ligaments relax, lens becomes fatter to allow more light refract into eye
Distant objects:
— Ciliary muscles relax, suspensory ligaments tightent, lens becomes thinner so light is refracted by a small amount
Explain myopia and hyperopia.
Myopia:
— Eyeball is too long or eye refracts light too much which causes image to be brought into focus in front of the retina. Glasses with concave lens are used for myopia.
Hyperopia:
— Eyeball is too short and light is not refracted enough which causes the imaged to be brought into focus behind the retina. Glass with convex lens are used for hyperopia.
What are three ways to correct vision defects?
Contact lenses:
— Thin lenses to compensate for the fault in the eye. Very lightweight and convenient for sports. Can either have hard or soft lenses. Soft lenses have higher risk of infection.
Laser eye surgery:
— Laser is used to change the shape of the cornea. Complications of infection or surgery going wrong.
Replacement lens surgery:
— Artificial lens is inserted into eye. Risk of complications or damage to retina.
How is body temperature controlled?
Temperature receptors in the skin and blood detect change and send impulses to the thermoregulatory centre.
If body temperature is too hot:
- – Vasodilation which is when blood vessels widen to allow blood to flow closer to the surface of the skin so heat is lose
- – Produce sweat which then evaporates off skin
- – Hairs lay flat
If body temperature is too cold:
- – Vasoconstriction which is when blood vessels constrict so less blood flows at surface of skin
- – Muscles contract which is shivering. It requires respiration so energy is transferred which warms body.
- – Hairs stand up to trap insulating layer of air
- – No sweat produced
What is a general overview of the endocrine system?
Endocrine system:
— Consists of endocrine glands which secretes chemicals called hormones directly into the bloodstream. The bloodstream carries these hormones to their target organs.
Why is the pituitary gland often referred to as the ‘master gland’?
The pituitary gland is sometimes referred to as the ‘master gland’ due to the fact that it secretes several hormones which then act on other glands to secrete other hormones in the endocrine system.
How are blood glucose levels in the body controlled?
After eating, blood glucose levels increase which causes the pancreas to secrete insulin. This causes glucose to move from the bloodstream into the liver and muscle cells. Then excess glucose is converted into glycogen in the liver and blood glucose levels are decreased.
When the blood glucose levels get too low, the pancreas secretes a hormone called glucagon which then converts glycogen in the liver back into glucose which is released into the bloodstream and blood glucose levels increase.
