Paper 2- Topic 5 (homeostasis) Flashcards
What is homeostasis
The regulation of the conditions inside your body to maintain a stable internal environment
What are the three components the automatic control systems are made up of to maintain a steady condition
Receptors
Co-ordination centres (brain,spinal cord , pancreas)
effectors
Negative feedback process
Receptors detects stimulus level is too high/ low
Co- ordination centre receives and processes the information , then organises a response
Effector produces a response which counteracts the change and restores the optimum level
The effectors will just carry on producing the responses for as long as they’re stimulated by the co-ordination centre
Different parts of the nervous system
Central nervous system (CNS)
- in vertebrates this consists of the brain and spinal cord only
- the CNS is connected to the body by sensory and motor neurones
Sensory neurones
- the neurones that carry information as electrical impulses from the receptors to the CNS
Motor neurones
- the neurones that carry electrical impulses from the CNS to effectors
Effectors
- all your muscles and glands which respond to nervous impulses
CNS response system
Stimulus Receptor Sensory neurones CNS Motor neurone Effector Response
Synapses
The connection between two neurones
The nerve signal is transferred by chemicals which diffuse across the gap
These chemicals set off a new electrical signal in the next neurone
What is a reflex
A rapid and automatic response to certain stimuli that doesn’t involve a conscious part of the brain
What is the reflex arc
The passage of information in a reflex (from receptor to effector)
Reflex arc system
Neurones go trough spinal cord or an unconscious part of the brain
When a stimulus is detected by receptors impulses are sent along a sensory neurone to the CNS
When the impulses reach a synapse between the sensory neurone and a relay neurone they trigger chemicals to be released . These chemicals cause impulses to be sent along the relay neurone
When the impulses reach a synapse between the relay and motor neurone the same happens
The impulses then travel along the motor neurone to the effector
The muscle then contracts and moves hand away from stimulus
Investigating reaction time practical
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The brains different regions
Cerebral cortex - responsible for consciousness, intelligence , memory and language
Cerebellum- responsible for muscle co-ordination
Medulla- controls unconscious activities like breathing and heartbeat
Spinal cord
Methods to study the brain
Studying patients with brain damage
Electrically stimulating the brain
MRI scans
Different parts of the eye
Sclera - tough supporting wall of the eye
Cornea - transparent outer layer found at the front of the eye which refracts light into the eye
Iris - contains muscles that allow to control the diameter of be pupil and therefore how much light enters
Lens - focuses light into the retina (which contains receptor cells sensitive to light and colour)
Ciliary muscles and suspensory ligaments - control the shape of the lens
Optic nerve - carries impulses from receptors on the retina to the brain
Iris reflex
When light receptors in the eye detect a very bright light a reflex is triggered that makes the pupil smaller
The circular muscles in the iris contract and the radial muscles relax
This reduces the amount of light that can enter the eye
The opposite process happens in dim light
To look at near objects
The ciliary muscles contract which slackens the suspensory ligaments
The lens becomes fat (more curved)
This increases the amount by which it refracts light
To look at distant objects
The ciliary muscles relax which allows the suspensory ligament to pull tight
This makes the lens go thin (less curved)
So it refracts light by a smaller amount
Long sighted - hyperopia
This occurs when the lens is the wrong shape doesn’t reflect the light enough or the eyeball is too short
The images of their objects are brought into focus behind the retina
Glasses with a convex lens (curve outward) correct it
The lens refracts the light so they focus on to the retina
Short sighted - myopia
This occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long
The image of distant objects are brought into focus in front of the retina
You can use glasses with a concave lens (curve inwards? to correct it so that the light rays focus on the retina
Treatment for vision defects
Contact lenses
Laser eye surgery
Replacement lens surgery
Body temperature controlled by negative feedback
Temperature receptors detect that the core body temperature is too high /too low
The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors immediately
Effectors produce a response and counteract change
When you’re too hot - body changes
Hairs lie flat
Sweat is produced by sweat glands and evaporates form the skin to transfer energy to the environment
Blood vessels supplying the skin dilate so more blood flows close to the surface of the skin . This is called vasodilation which helps transfer energy to the environment
When you’re too cold- body changes
Hairs stand up to trap an insulating layer of air
No sweat is produced
Blood vessels supplying the skin capillaries constrict to close off the skins blood supply which is called vasoconstriction
Shivering needs respiration which transfers some energy to warm the body
What are hormones
Chemical molecules released directly into the blood
Control things in organs and cells that need constant adjustment
Different endocrine glands
Pituitary gland
Thyroid
Ovaries
Adrenal gland
Pancreas
Testes
