S6 - Coordination and Response Flashcards
coordination and response:
-homeostasis is the maintenance of a constant internal environment, for example, mantaining body temperature or body water content
-coordinating responses there needs to be a stimulus (such as heat), a receptor which detects the stimulus (such as the skin on the fingertip) and then an effector which produces the response (such as arms muscles moving the hand away)
tropisms in plants:
-plants need hormones to coordinate and control growth, examples include phototropism, the response to light, and gravitropism or geotropism, the response to gravity
-hormones move from the place they are made where they are needed in order to produce the appropiate response
auxins: positive phototropism
most plants show positive phototropism because they grow towards the light source
-the plant is exposed to light on one side
-auxin, a growth hormone, moves to the shaded side of the shoot
-auxin stimulates cells to grow more here
-this means the shoot bends towards the light
-the plant receives more light, meaning photosynthesis can occur at a faster rate
auxins: negative phototropism
most shoots show negative gravitropism as they grow away from gravity, if a shoot is horizontal:
-auxin moves to the lower side
-the cells of the shoot grow more on the side with most auxin, so it stimulates cells to grow more here
-this makes the shoot bend and grow away from the ground
-this is beneficial as light levels are likely to be higher further away from the ground
auxins: positive gravitropism
most roots show positive gravitropism as they grow towards gravity, if a root is horizontal:
-auxins moves to the lower side
-the cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side
-this makes the root bend and grow downward
-this is beneficial as there are more likely to be increased levels of water and nutrients lower down, and it provides stability for the plant
when the auxin distribution becomes equal on both sides it grows straight in that direction
the human nervous system: nervous vs endocrine system
-the nervous system is made up nerve cells that carry impulses around the body
-the endocrine (hormonal) system is made up of glands that produces hormones that stimulate changes in the body
both systems require stimuli, receptor and effectors and chemicals are involved in both, but there are also key differences between them:
nervous system:
-type of signal: electrical
-transmitter: nerve cells
-speed of response: very fast
-duration of response: short
endocrine system:
-type of signal: chemical
-transmitter: hormones in bloodstream
-speed of response: slower
-duration of response: long
the CNS:
the central nervous system (CNS) consists of the brain and the spinal cord, it allows us to make sense of our surrounding and respond to do it in order to survive
1) receptor cells in sense organs convert a stimulus (such as a bright light) into an electrical impulse
2) this electrical impulse travels along cells called sensory neurons to the central nervous system (CNS)
3) here, the information is processed and the appropiate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors
4) the effectors carry out the response (this may be muscles contracting or glands secreting hormones)
synapses:
-a synapse is the gap between two neurons, transmission of impulses across the synapse is chemical and uses neurotransmitters
-neurotransmitters are the chemical released at one of a nerve fibre
-when an electrical impulse is carried along an axon it triggers the nerve-endings to release neurotransmitters, this is because the electrical impulse cannot directly travel across the synapse (gap) and so needs to be converted to a chemical and then back to an electrical impulse
-the neurotransmitter diffuses across the synapse and bind to receptor molecule on the next neuron, this stimulates the second neuron to transmit the electrical impulse
the reflex arc:
-the reflex arc is a subconscious response to a dangerous stimuli, such as a hot surface, sometimes an extremely quick response is needed and there is not enough time for it to go through the conscious portion of brain so the CNS is involved instead
1) a stimulus is detected by receptors, such as thermoreceptors in fingertips detecting heat
2) impulses are sent along a sensory neuron
3) in the CNS the impulse passes to a relay neuron
4) impulses are sent along a motor neuron
5) the impulse reachers an effector resulting in the appropiate response, such as a contraction of the biceps to move the arm away from the heat source
the eye:
-cornea: the transparent outer part of the eye -> it refracts light to reach the retina
-iris: the coloured part of the eye that does not allow light to go through -> controls how much light enters eye + in bright light, the circular muscles contract and radial muscles relax to make the pupil smaller, avoiding damage to the retina + in dim light, the circular muscles relax and the radial muscles contract to make the pupils larger, so more light can enter to create a better image
-lens: transparent, biconvex disc that attaches to ciliary muscles by the suspensory ligaments + focuses light onto the retina
-retina: contains light receptors -> contains rods (respond to dim light) and cones (respond to colour)
-optic nerve: carries impulses between the eye and the brain
order: conjunctiva, cornea, pupil, iris, lens, ciliary muscle, suspensory ligament, retina, fovea, optic nerve
accomodation of the eye:
near object:
-ciliary muscles contract
-suspensory ligaments slacken
-this allows the lens to become fatter so the light is refracted more
-light converges on the retina
distanct object:
-ciliary muscles relax
-suspensory ligaments stretch
-this allows the lens to become thin so the light is refracted less
-lighy converges on the retina
temperature:
-human body temperature is 37 degrees celcius, the thermoregulatory centre which monitors and controls body temperature to ensure it remains the temperature is found in the brain
-has receptors that monitor the temperature of the blood
-has receptors in the skin that send impulses to the thermoregulatory centre
when it is hot:
-sweat (evaporates from skin surface resulting in increased energy transfer away from body) is produced by sweat glands
-vasodilation means more blood flows closer to the surface of the skin, resulting in increased energy transfer from the body
when it is cold:
-sweating stops
-skeletal muscles contract rapidly (shivering) to generate heat from respiration
-hair stands on end to create an insulating layer, trapping warm air
-vasconstriction means blood does not flow so close to the surface, resulting in less heat lost
the endocrine system:
-hormones are chemical messengers that are secreted by endocrine glands into the bloodstream, where they are transported around the body to receptors on the target organ, the pituitary gland, mentioned before is one of the most important glands: source, roles and effects
-adrenaline: adrenal gland, prepares the body for ‘fight or flight’ response, increases heart rate and breathing rate
-insulin: pancreas, lowers blood glucose levels, converts glucose in the blood into glycogen for storage in muscles and liver
-testosterone: testes, main sex hormone in males, produces secondary sexual characteristics in males (e.g: hair growth, depper voice)
-progesterone: ovaries, mantains pregnancy, mantains the uterus lining so that the fertilised egg can implant
-oestrogen: ovaries, main sex hormone in females, produces secondary sexual characteristics in females, (e.g: breasts developing) and control menstrual cycle
