Topic 5 - Homeostasis And Response Flashcards
What is homeostasis ?
The regulation of the internal conditions of an organism to maintain optimum conditions for function in response to internal and external changes
What do all control systems include and what do they do ?
- receptors, which detect stimuli (changes in environment)
- coordination centers (brain, spinal cord, pancreas) that receive and process info from receptors
- effectors, muscles or glands which bring about responses to restore optimum levels
How are neurons adapted to their function ?
- long axon to carry messages over long distances
- axon is insulated by a fatty myelin sheath which increases the speed of the nerve impulses along the neuron
- dendrons at end of neuron which branch further into dendrites which receive incoming nerve impulses from other neurones
What are the structures of the reflex arc and what do they do ?
Stimulus
receptor (detects a stimulus)
sensory neuron (sends electrical impulses to relay neuron)
relay neuron (connects sensory neurons to motor neurons)
motor neuron (sends electrical signals impulses to an effector)
effector (produces a response)
response
What is the CNS and what does it do ?
Central nervous system, (brain and spinal cord) coordinators the response from the effectors
What does the effector do ?
Muscles contracting, glands secreting hormones
What is a reflex action ?
Automatic, rapid, unconscious response to a stimulus
How does an electrical impulse cross a synapse ?
- electrical nerve impulse travels along the first axon
- when it reaches the dendrites neurotransmitters are released
- these chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the second neuron
- the binding of neurotransmitter to the receptors stimulates the second neuron to transmit an electrical impulse along its axon
Plan and carry out an investigation into the effect of a factor on human reaction time
Ruler drop test :
- hold a ruler vertically from one end
- Test subject should have their thumb and finger at either side of the ruler
- drop the ruler and the subject should try and catch it between their finger and thumb as fast as possible
- note down the distance that the ruler has travelled before the subject has caught it
- repeat at least 10-20 times, recording each attempt on a table
- use a table to convert these distances into reaction time
- find a mean reaction time
- repeat this experiment on a subject (who has just had coffee)
- compare reaction times
Independent variable = whether subject has (had caffeine)
Dependent variable = subjects reaction time
Control = distance the finger and thumb are apart, angle, ruler size
What are the 3 main components of the brain ?
Cerebral cortex, cerebellum, medulla
Where is the cerebral cortex and what does it do ?
Outer part of brain which controls consciousness, intelligence, memory and language
Where is the cerebellum and what does it do ?
Rounded structure towards bottom of brain which controls fine movements of muscles
Where is the medulla and what does it do ?
Found in the brain stem at front of cerebellum and controls unconscious actions such as breathing and heart rate
Why is it difficult to investigate brain function and treat brain damage ?
- complex and delicate
- easily damaged
- drugs cannot always reach the brain because of membranes
- not fully understood which part of the brain does what
What are 3 methods neuroscientists can do to map out regions of the brain ?
- studying patients with brain damage and the changes the following damage has caused on a certain area of the brain
- electrically stimulating different parts of the brain (pushing an electrode into the brain) as it might result in a mental or physical change in the individual providing info on its role
- using MRI scanning techniques to create an image of the brain to show which part of the brain is affected by a tumor or which part is active during a specific task
Name the 6 parts of the eye
Retina, optic nerve, sclera, cornea, iris, cilliary muscles and suspensory ligaments
What is the retina and what does it do ?
Layer of light sensitive cells at back of eye
When light hits it the cells are stimulated and impulses are sent to the brain which interprets the info to create an image
What is the optic nerve ?
A nerve that leaves the eye and leads to the brain, it carries the impulses from the retina to the brain to create an image
What is the sclera ?
White outer layer which supports structures inside the eye
What is the cornea ?
The see through layer at the front of the eye which allows light through and bends and focuses light on the retina
What is the iris ?
Muscles that surround the pupil and contract or relax to alter the size of the pupil
What does the iris do in bright light vs dim light ?
Bright : circular muscles contract and radial muscles relax to make the pupil smaller
Dim : circular muscles relax and radial muscles contract to make the pupil larger
What do the ciliary muscles and suspensory ligaments do ?
Hold the lens in place and control its shape
How does the eye focus on a near object ?
Accommodation:
- ciliary muscles contract
- suspensory ligaments looses
- lens is thicker and more curved which refracts light more
