5.1 Neuronal communication & sensory receptors Flashcards
what must all organisms do?
respond to changes in their internal and external environment
how do animals respond to their environment?
neuronal and hormonal
how do plants respond to their environment?
chemical communication including hormones e.g. auxin
what factors do we respond to in our environment?
humidity temperature sound light intensity blood glucose levels internal temperature cell PH water potential
why is coordination needed?
few body systems can work in isolation
all cells have specialised functions so must coordinate the function of different cells and systems efficiently
(Coordination) give an example of body systems needing to work together? (animals)
muscles contract and need O2
O2 transported in RBCs
RBCs made in bone marrow my haematopoietic stem cells
(coordination) give an example of plant cells needing to coordinate? and how they do it?
flowering plants need to coordinate with the seasons to know when to flower, light sensitive chemicals enable this to happen
(Homeostasis) in multicellular animals different organs have different functions….
….so must be coordinated
(Homeostasis) give examples of a system in which organs must work together:
digestive organs must work together to maintain blood glucose levels
what does nervous and hormonal control rely upon?
communication at cellular level through cell signalling
where can cells transfer signals?
locally - between neurones at synapses
over large distances using hormones
what is AUTOCRINE cell signalling?
where the call targets itself
what is PARACRINE cell signalling?
where cell targets nearby cell
what is ENDOCRINE cell signalling?
where the cell targets a distant cell through the bloodstream
What does cell signalling across gap junctions involve?
a cell targeting another cell which it is connected by gap junctions
what is the nervous system responsible for?
detecting changes in the internal and external environment
what is the pathway a nerve impulse follows?
receptor -> sensory neurone -> relay neurone -> motor neurone-> effector
what are some axons covered in?
a myelin sheath (many layers of plasma membrane)
what sort of cells produce the myelin sheath? how do they do it?
schwann cells
by growing around the axon many times adding a double layer of phospholipid bilayer each time
what is the function of the myelin sheath?
insulation which leads to conducting electrical impulses at faster speeds
what is the function of a motor neurone?
transmitting electrical impulses from the relay neurone (in the CNS) to the effector producing a response
what is the function of a sensory neurone?
transmitting the electrical impulse from receptor cells to a relay neurone, motor neurone or the brain
what is the function of the axon?
to carry nerve impulses away from the cell body
what is multiple sclerosis?
autoimmune disease which affects nerves in the brain and spinal chord
what does multiple sclerosis involve and what does it result in?
thinning of myelin sheath and axon, slow impulses, results in problems with muscle movement and vision
what are sensory receptors?
groups of specialised cells located in sense organs such as the eyes and ears
what do sensory receptors do?
convert the stimulus they detect into nerve impulses called a GENERATOR POTENTIAL which is transmitted to the CNS
what are the two main features of sensory receptors?
specific to a single type of stimulus
acts as a transducer converting a stimulus to a nerve impulse
what are the 4 types of sensory receptors?
photoreceptors
chemoreceptors
mechanoreceptors
thermoreceptors
what stimulus does a mechanoreceptor detect? give an example of a mechanoreceptor and the sense organ:
pressure and movement
pacinian corpuscle (detects pressure)
organ: skin
what stimulus does a chemoreceptor detect? give an example of a chemoreceptor and the sense organ:
chemicals
olfactory receptor (detects smells)
organ: nose
what stimulus does a thermoreceptor detect? give an example of a thermoreceptor and sense organ:
heat
end bulbs of Krause
tounge
what stimulus does a photoreceptor detect? give an example of a photoreceptor and sense organ:
light
cone cell (detects different wavelengths of light)
eye
what are pacinian corpuscle’s?
sensory receptors that detect mechanical pressure
where are pacinian corpuscle’s located?
in the joints and deep within skin
what does the centre of the pacinian corpuscle contain?
the end of the sensory neurone surrounded by layers of connective tissue with each layer being separated by gel
the neurone ending in a pacinian corpuscle has a…
…stretch mediated sodium ion channel
- In resting state the stretch mediated sodium ion channels in the sensory neurones membrane are too narrow to?
allow sodium ions to pass through - it has resting potential
- when pressure is applied to the pacinian corpuscle what does it do?
it changes shape causing the membrane to stretch
- When the membrane stretches what happens to the sodium ion channels?
sodium ion channels widen and sodium can diffuse into the neurone
- what does the influx of positive ions do to the membrane?
changes the potential of the membrane, it becomes depolarised resulting in a generator potential
- what does the generator create?
an action potential that passes along the sensory neurone to the CNS
what do rod cells allow? what is this due to?
vision in dim light
due to the presence of a pigment called RHODOPSIN found in membrane bound vesicles
what happens to rhodopsin when it absorbs light?
Bleaching - it is split into opsin and retinal.
Low levels of light are enough to cause this breakdown
what effect does opsin have on the rod cells permeability to sodium?
changes its permeability to sodium, initiating a generator potential
what are cone cells sensitive to? what is this due to?
high light intensities
due to the presence of the pigment IODOPSIN
what happens to iodopsin in bright light?
broken down into its constituent parts, generating an action potential in the ganglion cell
what does the cell body consist of?
nucleus surrounded by the cytoplasm, which contains large amounts of ER & mitochondria involved in the production of neurotransmitters
what are dendrons?
short extensions from the cell body which divide into dendrites. They transmit electrical impulses toward the cell body.
