Stimuli And Responses Flashcards
Define taxis
Directional movement in response to a stimulus eg woodlice
Define kenesis
Non directional movement in response to a stimulus.
What are receptors made of and what do they do
Cells , proteins on cell surface membranes and they detect stimuli
What do baroreceptors do
Detect changes in blood pressure
What are effectors and what do they do
Cells that bring about a response to a stimulus to produce an effect they include muscle cells and cells found in glands eg pancreas
How do receptors communicate with effectors
Via the nervous system or hormonal system of both
What do sensory neurons do
Transmit electrical impulses from the receptors to the CNS
What do motor neurones do
Transmit electrical impulses from the CNS to effectors
What do relay neurones do
Sensory to motor neurones
What is the pathway of nervous communication
Stimulus - receptors - sensory neurone - CNS- motor neurone - effectors - response
Why is the nervous response deprived as localized
Neurotransmitters are secreted directly onto cells
What is a simple reflex
A rapid involuntary response to a stimulus it does not go through conscious part of brain just spinal chord
What is a tropism
The response of a plant to a directional stimulus
What is phototropism and how do shoots and roots react to it
Growth of a plant in response to light shoots are positively phototrophic roots are negatively phototrophic
What is gravitropism and how do roots and shoots react to it
The growth of a plant in response to gravity shoots are negatively gravitropic and roots are positively gravitropic
What do receptors in the nervous system do
Convert the energy of the stimulus into the electrical energy bused by neurones
What is resting potential
Inside of cell is relatively negative to outside of cell this creates a potential difference
What is generator potential
When stimulus is detected the cell membrane is excited and becomes more permeable allowing more ions to move in and out of the cell altering the potential difference, when its due to a stimulus it is generator potential
What is an action potential
When generator potential reaches threshold it’ll trigger an action potential ( electrical impulse alone a neurone )
What is the strength of the stimulus measured by
Frequency of action potentials
What is the pacinian corpuscle
A mechanoreceptor that detect pressure or vibrations
What is the structure of the pacinian corpuscle
Contain the end of a sensory neurone wrapped in loads of layers of connective tissue called lamellae
How is the pacinian corpuscle stimulated
Tap on the sync, lamellae are deformed and press on the sensory nerve ending this causes sensory neurones cell membrane to stretch deforming stretch mediated sodium ion channels so they open and sodium ions diffuse into the cell creating generator potential , this may reach the threshold and create an action potential
What are photorecepors in the eye and how are they controlled
Detect light and muscles of iris control it
What do you call the area of the eye that has the most photoreceptors
Fovea
Where are nerve impulses carried in the eye
Nerve impulses from receptor cells are carried from retina to the brain by the optic nerve ( bundle of neurones )
Where is the blind spot of the eye
Where the optic nerve leaves the eye , there aren’t any photoreceptors so it’s not sensitive to light
How do photoreceptors work?
Light enters the eye , hits photoreceptors and is absorbed by optical pigments. Light bleaches the pigments causing a chemical change altering the membrane permeability to sodium ions. A generator potential is created and if it reaches threshold a nerve impulse is sent along bipolar neurone which connect photoreceptors to the optic nerve which takes impulses to the brain
Where are rods and cones found ?
Rods are in the peripheral parts of the retina and cones are packed together in the fovea
What are the differences between rods and cones ?
Rods - info in black and white , many rods joins 1 bipolar neurone , highly sensitive to light , give low visual acuity
Cones - give info in colour , one joins one bipolar neurone , low sensitivity to light, gives high visual acuity
What’s the difference between the CNS and the peripheral nervous system ?
CNS- brain and spinal chord
Peripheral - made up of neurones that connect the CNS to rest of body
What is the peripheral nervous system ?
Somatic and autonomic.
Somatic controls conscious activities autonomic controls unconscious activities eg digestion
Autonomic is sympathetic and parasympathetic . Sympathetic is “fight or flight “ parasympathetic is “rest and digest “
Cardiac muscle is myogenic what does that mean ?
It can contract and relax without receiving signals from nerves
What is the SAN and what does it do
Small mass of tissue in wall of right atrium that acts as a pace maker by sending refuel waves of electrical impulses to atrial walls which causes right and left atria to contract at same time
What does non conducting collagen tissue do
Prevents waves of electrical activity from being passed directly from the Syria to the ventricles instead they go to AVN
What does the AVN do
Passes waves of electrical activity on to the bundle of His but there is a slight delay before the AVN reacts to make sure the atria have emptied before the ventricles contract.
What is the bundle of his and what does it do
What is purkyne tissue and what does it do
Group of muscle fibers responsible for conducting waves of electrical activity between ventricles to the apex of the heart the bundle splits into finer muscle fibers in the ventricle walls these are the purkyne tissue which carries waves of electrical activity into the muscular walls or lefgcand right ventricles causing them to contract simultaneously from bottom up
What is the route of waves of electrical activity in heart beats
SAN, AVN , bundle of his , purkyne fibers
What controls rate at which SAN generates electrical impulses ?
Medulla
What are pressure receptors and where do you find them
Eg baroreceptors in aorta and carotid arteries stimulated by blood pressure
How is high blood pressure controlled
Baroreceptors - Hugh blood pressure - impulse along sensory neurone - medulla - impulse along parasympathetic neurone - secreted acetylcholine which binds to receptors on SAN - heart rate slows down to reduce blood pressure to normal
How is low blood o2 high co2 or low blood ph levels controlled
Chemoreceptors detect chemical change in blood and sends impulses along sensory neurones to medulla which sends impulses along sympathetic neurones these secrete Noradrenaline which binds to receptors on SAN this causes heart rate to increase to return o2 co2 and pH levels back to normal
