Homeostasis Flashcards
Definition of homeostasis
Is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
What are the iternal conditions you need to control
Body temperature
Blood glucose concentration
Water levels
Control of homeostasis
Receptors- Cells that detect changes in the internal or external environment. Known as stimuli. Receptors may be part of the nervous or the hormonal control systems of the body
Coordination centres-areas the receive and process the information from the receptors. They send out signals and coordinate the response of body. E.g brain, spinal cord, pancreas
Effectors-muscles and glands that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum levels
What does the human nervous system consist of
Consists of:
-Central nervous system- the brain and spinal cord
- peripheral nervous system- all of the nerves in the body
Adaptations of the nervous system
-neurones have a cell body and cytoplasmic extensions from this body called axons and dendrites
-some human neurones have axons over a metre in length and are far more efficient than having multiple neurones to convey information from CNS to effectors-less time is wasted transferring electrical impulses from one cell to another
-The axon insulated by a fatty myelin sheath with small uninsulated sections along it which the impulse jumps along
How nervous system works
-receptor cells convert stimulus into an electrical impulse
-This electrical impulse travels along cells called sensory neurons to the central nervous system
-Here, information is processed and appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors
-The effectors carry out the response (this may be muscles contracting or glands secreting hormones).
Different types lf neurones
Sensory neurones- The neurones that carry information as electrical impulses from the receptors in the sense organs to the CNS
Relay neurones-The neurones that carry electrical impulses from sensory neurones to motor neurones. They are found in CNS
Motor neurones- The neurones that carry electrical impulses from CNS to the effectors
Pathway through nervous system
Stimulus —> receptor cells—(impulse neurone)–> Central Nervous System (brain and spinal cord)—– (impulse neurone)—> effector (muscle or glands)—-> Response
Different sense organs,coordinators and effectors
Sense organs:
-ear
-skin
-nose
-eye
Coordinators:
-spinal cord
-brain
Effectors:
-pancreas
-salivary gland
-skeletal muscle
Reflex arc process
1) when a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS
2) When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone
3)when the impulses reach a synapse between relay neurone and a motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone
4) the impulses then travel along the motor neurone to the effector (usually a muscle)
5)If the effector is a muscle, it will respond to the impulse by contracting. If it’s a gland, it will secrete a hormone
The neurones lf the reflex arc and differences between them
Sensory neurones carry impulses from sense organs to the CNS (brain or spinal cord)
Relay neurones are found inside the CNS and connect sensory and motor neurones
Motor neurones carry impulses from the CNS to effectors
Looks:
-sensory neurones are long and have cell body branching off the middle of the axon
-relay neurones are short and have a small cell body at one end with many dendrites branching off it
-motor neurones are long and have a large body at one end with long dendrites branching off it
Reflex actions pathway
Stimulus—->receptor cells—-(sensory neurones)–>relay neurone in spinal cord—(motor neurone)—->effectors(muscle/glands)—->response
Synapses
-electrical impulse travels along the first axon
-when an electrical impulse arrives at one end of the axon on the presynaptic neurone,chemical messengers called neurontransmitters are released from vesicles
-the neurontransmitters diffuse across the synaptic gap and bund with the receptor molecules on the membrane of the second neurone
-this stimulates the second neurone to generate an electrical impulse that travels down the second axon
-the neurontransmitter are then destroyed or recycled to prevent continued stimulation of the second neurone which would cause repeated impulses to be sent
-synapses ensure that impulses only one direction
Reaction time experiment-method
Aim: to plan and carry out an investigation into the effect of a factor on human reaction time
You will: -choose factor that you wish to investigate that will have an effect on reaction time. Carry out a number of experiment to measure reaction time
-Reaction time is the time taken to respond to a stimulus; reactions are usually very quick responses typically taking less than a second to occur
-reaction time can be affected by factors such as age, stress or use of drugs
-you can investigate the effect of background noise or consumption of caffeine on how quickly a person catches a ruler
Method:
-person being tested should sit with their arm resting on the edge of a table (this should stop their arm moving up or down during the test)
-hold a ruler vertically between their thumb and forefinger. Make sure that the zero end of the ruler is level with their thumb and finger. Them let go without giving warning
-The person being tested should try to catch the ruler as quickly as they can-as soon as they see it fall
-Reaction time is measured by the number on the ruler where it’s caught, at the top of the thumb-the further down it’s caught, the slower their reaction time
-Repeat the test several time then calculate the mean distance that the ruler fell
-use a conversion table to convert ruler measurements into reaction times
The person being tested should then have a caffeinated drink. After ten minutes, repeat all the steps.
Controlling variables-reaction time
-you should use the same person to catch the ruler each time
-that person should always use the same hand to catch the ruler
-the ruler should always be dropped from the same height
-you should make sure that the person being tested had mot had any caffeine before the start of the experiment
How to improve experiment-reaction time
-possible to carry out reaction time investigation using a computer; this is obviously more precise as it removes human error from measurements
-reaction time can be also recorded in milliseconds which is more accurate than seconds
