Homeostasis - Chapter 11 Flashcards
What is homeostasis?
The maintenance of constant internal conditions.
This is important as the enzymes in our body work best in these conditions.
What are receptors?
They detect stimuli in internal and external environments
What is a stimulus?
A change in the environment
What is the coordination centre?
Areas that receive and process the information then send out signals and coordinate body response.
This includes brain, spinal cord, and some organs like pancreas.
What is an effector
A muscle or a gland that produces responses to restore internal conditions.
What happens in the nervous system?
- Receptor detects stimuli - information is sent to the CNS via the sensory neuron
- Electrical impulse travels to the CNS to the relay neuron where it coordinates a response
- CNS passes this information using impulses via the motor neurons which go to the effector
- The effector - muscle or gland - responds by contracting (muscle), or secreting a hormone (glands)
What is the flow chart for what happens in the nervous system?
Receptor –> sensory neurone –> CNS (relay neurone) –> motor neurone –> effector
2 ways reaction time can be measured?
- use ruler drop test
- Investigate different factors that affect reaction time such as talking on the phone, listening to music, drinking cola.
What are reflexes?
Automatic, unconscious responses.
Reflexes bypass the conscious part of the CNS.
Reflex Arc Flowchart
Receptor –> sensory –> CNS –> relay (in the spinal cord) –> motor –> effector
You realise you have had a reflex after it happens. How?
An impulse travels up the spinal cord to the conscious part of the brain so you know the reflex has occurred, but only after it’s happened.
What is the 2 things that protect the brain?
- The skull
- It is encased in protective membranes called the meninges
What disease occurs when the meninges get infected?
Meningitis
4 different parts of the brain.
Cerebral Cortex
Cerebellum
Medulla
Hypothalamus
What does the cerebral cortex control?
Consciousness, intelligence, memory and language.
What does the cerebellum do?
Coordinates muscular activity and balance (think of Trisha tiptoeing to ring the koyil bell)
What does the medulla do?
Unconscious activities –> breathing, heartbeat, movements of the gut
What does hypothalamus do?
Controls body temperature, and has the pituitary gland which produces many hormones
How do we learn about the brain?
- MRI Scans (magnetic resonance imaging)
- Comparing a injured person’s brain to a normal brain to see the differences and their possible effects.
Go label an nerve cell
Well done
What is an eye?
A sense organ, which contains many receptors that are sensitive to light intensity and colour.
9 structures of eye.
- Lens
- Cornea
- Pupil
- Iris
- Suspensory ligament
- Ciliary muscles
- Retina
- Sclera
- Optic Nerve
What is the sclera?
- The white outer layer of the eye
- Relatively tough and strong, to avoid damage to the eye
- Sclera=Safety
What is the cornea?
- Transparent area at the front of eyeball.
- Allows light into the eye.
- Has curved surface, which is important for changing the direction of light rays coming into the eye.
- It makes sure that light rays which enter the eye are focused on the retina.
What is the iris?
- Controls the size of the pupil
- Made up of muscles that contract or relax to change the size of the pupil.
- Control the amount of light reaching the retina.
What is the pupil?
The pupil is the opening at the centre of the iris through which light passes.
What happens in bright light?
- Pupil constricts ( gets smaller)
- Circular muscles contract
- Radial muscles relax
BRIGHT LIGHT =PC CC RR
What happens in dim light?
- Pupils dilate ( get bigger)
- Circle muscles relax
- Radial muscles contract
DIM LIGHT = PD CR RC
What happens in the lens?
- Changes the direction of light rays to produce a clear image
What is the lens held in place by?
- Suspensory ligament
- Ciliary muscles
What happens when light rays hit the retina?
- Light sensitive cells are stimulated.
- They send impulses to the brain, along the sensory neurones in the optic nerve.
- When the brain receives these messages, it interprets them as a visual image.
What happens if light is focused behind or in front of the retina?
The image becomes blurry.
How does light get focused?
- Light is focused by refractions, where it changes directions are it passes through the eye.
- The cornea changes the direction of the light rays onto the retina.
What is the process of accommodation?
- The process of changing the shape of the lens of the eye, to focus on near/distant objects.
How can you focus on close object?
- Ciliary muscles contract.
- Suspensory ligaments loosen.
- Lens becomes thicker.
What happens to focus on distant objects?
- Ciliary muscles relax
- Suspensory ligament contract
- Lens become thinner.
What is a myopia?
- Short sightedness
- Distant objects look blurred.
- Caused because light is focused in
front of the retina.
What is hyperopia?
- Long sightedness
- Close-by objects are blurry
- Caused because light is focused
behind the retina.
What can myopia be treated with?
Concave lens glasses
What can hyperopia glasses be treated with?
Convex glasses
What other ways are there to treat eye defects?
- Glasses
- Hard and Soft contact lenses
- Laser surgery
- Replacement lenses in the eye
Go label an eye
Well done
What is the endocrine system?
The hormone system
What are hormones?
chemical messengers (they are also a protein)
What is the endocrine system made up of?
glands that secrete hormones directly into the bloodstream
What does the blood do to the hormones?
The blood takes the hormones to their target organs/cells where it binds to receptors to produce a response
Difference between nervous system responses and hormonal responses?
Hormones can act rapidly, but are a lot slower compared to the nervous system. However hormones have a longer lasting effect
What are examples of rapid hormones?
Insulin and adrenaline
Examples of slow hormones?
Growth hormones and sex hormones
What are all endocrine glands controlled by?
the pituitary gland
What is TSH?
Thyroid stimulating hormone –> this hormone stimulates the thyroid gland to release thyroxine, a hormone that is involved in metabloic activity