B10: The Human Nervous System Flashcards
What are the conditions inside our body known as?
Internal Environment
What is homeostasis?
The regulation of internal conditions of a cell or organism to maintain optimum conditions for function.
What are some internal conditions that are controlled? (3)
Body temperature, the water content of the body and blood glucose concentration.
Homeostasis involves c———— and c————-.
Coordination and control.
What are receptors?
Cells that detect changes in the internal or external environment (the changes are called stimuli).
What are coordination centres?
Areas that receive and process the information from the receptors.
What does the brain act as a control centre for?
The nervous system, parts of the hormonal system, the spinal cord and some organs like the pancreas.
What are effectors?
Muscles or glands that bring about responses to the stimulus that has been received.
How fast do electrical impulses move in the nervous system?
Between 1 and 120 metres per second.
What 3 parts do receptors cells have?
Nucleus, cytoplasm and a cell membrane.
How does the nervous system work? (4 steps)
- Sensory receptor detects a stimulus and is sent as an electrical impulse along neurones.
- The impulse travels along the neurone until it reaches the CNS.
- The motor neurones carry the impulses to the right bits of your body (so the effectors can respond).
4.
What is the CNS made up of?
The brain and spinal cord.
What are the cells that carry impulses from sense organs to the CNS called?
Sensory neurones
Effectors may be m——— or g——-.
Muscles or glands
How do muscles respond to the arrival of impulses?
By contracting.
How do glands respond to impulses?
By secreting chemical substances (e.g. salivary glands release extra saliva when you smell food cooking)
How can the nervous system be summed up?
Stimulus➡️receptor➡️CNS➡️
Effector
What are reflexes for?
They help you avoid danger or harm because they happen so fast.
Reflexes do not involve the c————— part of your brain.
Conscious
What 3 types of neurones do simple reflex actions involve?
Sensory neurones, motor neurones and relay neurones.
What are the meninges?
Protective membranes that encase your brain.
What is the purpose of the cerebral cortex?
It’s concerned with consciousness, intelligence, memory and language.
What is the purpose of the cerebellum?
It’s concerned with coordinating muscular activity and balance.
What is the purpose of the medulla?
It’s concerned with unconscious activities (e.g. controlling the heartbeat, movements of the gut and breathing).
What is the purpose of the hypothalamus?
Controlling body temperature.
What is the purpose of the pituitary gland?
It produces many hormones
How does electrically stimulating different parts of the brain do work?
Seeing the effect that electrical stimulation has on someone (experiencing hunger, anger, fear, or thirst).
How do MRI scans work?
A magnetic resonance imaging (MRI) scan will show exactly which part of the brain is affected by a tumour, stroke etc.
What are 4 problems with the brain?
- Complex
- Delicate
- Easily damaged/destroyed
- Drugs don’t always reach the brain
What is the sclera?
The outer white layer of the eye. Tough and strong.
What is the cornea?
Transparent area at the front of the eyeball. Let’s light into the eye.
Why is the cornea curved?
To change the direction of the light rays coming into the eye, making sure they’re focused on the retina.
What is the iris?
Te hole through which light enters the eye. It’s made of muscles to contract or relax to change the size of the pupil and control the amount of light etching the retina.
What is the lens?
A clear disc. It’s held by suspension ligaments and ciliary muscles
What happens when light hits the retina?
Light-sensitive cells are stimulated. Thy send impulses to the brain along the sensory neurones I the optic nerve.
The light that reaches your eye from distant objects is travelling at almost p————- rays
Parallel
The —— makes sure you can see both close and distant objects equally well.
Lens
What is accommodation?
The process of changing the shape of the keys to focus on nearer or distant objects.
Wha happens when you focus on a distant object?
Te ciliary muscles relax so the suspensory ligaments are pulled tight and the lens is pulled flat and thin. It refracts light rays slightly.
What happens when you focus on a near object?
The ciliary muscles contract so the suspensory ligaments loosen. The lens is thicker and more curved. It refracts light rays strongly.
What are two of the most common eye defects?
Myopia (short sightedness) and hyperopia (long sightedness).
What does myopia (short sightedness) involve?
You can see close objects I clear focus, but distant objects look blurred.
Why does myopia happen?
A result of a lens that is too curbed or a particularly long eyeball.
What is the most common way of treating myopia?
Wearing glasses with a concave lens that spread out the light from distant objects before it reaches the eye.
What does hyperopia long sightedness) involve?
You can focus clearly on distant objects but close objects appear blurred.
Why does hyperopia happen?
The result of a lens that is too flat and thin or a particularly short eyeball.
How is hyperopia most commonly treated?
Glasses with a convex lens. The bring the light rays together more fore they reach the eye itself.
What is the purpose of contact lenses?
Placed on the surface of the eye and do the same job as glasses but can’t be seen and make playing sport etc. much easier.
What is the difference in material in hard contact lenses and soft contact lenses?
Hard contact lenses= rigid material lasts a long time.
Soft contact lenses=flexible material, ore comfortable but don’t last as long.
How is laser eye surgery used to treat myopia?
Reducing thickness of the cornea so it refracts the light less strongly.
How is laser eye surgery used to treat hyperopia?
Lasers are used to change the curve of the cornea so it refracts light from close objects more effectively.
