chapter 11- Neural communication Flashcards
Explain the need for communication systems in multicellular organisms - 5.1.1a
- Animals and plants need to be able to respond to changes in their internal+ external environment and coordinate the activities of their different organs
- Have different control and communication systems in order to function effectively and ensure internal conditions are kept constant
- physiological control systems maintain the inertial environment within narrow limits through process of homeostasis
Define homeostasis and the need for it - 5.1.1a
The maintenance of an organisms internal environment in response to changes in the internal/external environment within narrow limits.
- ensures maintenance of optimal conditions for enzyme action and cell function
- Needed for suitable temp, ph, an aqueous environment + freedom for toxins/inhibitors
Describe communication between cells by cell signalling - 5.1.1b
One cell releases a chemical which has an effect on another target cell.
-transfers signals locally (neurones at synapses)
-transfers signal across large distances (hormones)
what is the role of mammalian sensory receptors? - 5.1.1c
Detect change in external environment- convert stimulus into nerve impulse- through nervous system into CNS- Brain- required response coordinated- impulse sent to effector- desired response
What do mechanoreceptors do + example - 5.1.1c
Stimulus: pressure and movement
E.g: pacinian corpuscle
organ: skin
What do chemoreceptors do + example - 5.1.1c
Stimulus: Chemicals
E.g: olfactory receptor(detects smell)
organ: nose
What do thermoreceptors do + example - 5.1.1c
Stimulus: heat
E.g: end-bulbs of Krause
organ: tongue
What do photoreceptors do +example - 5.1.1c
stimulus: light
e.g; cone cells (detects different light wavelengths)
organ: eye
What is a transducer? - 5.1.1c
Detects a range of different stimuli- converts stimulus into a nervous impulse (generator potential)- change from one form of energy to another
- sensory receptors are transducers.
What is the pacinian corpuscle and function: 5.1.1c
A specific receptor that detects mechanical pressure
- located deep in skin; fingers, soles of feet and joints
- so we know which joints are changing direction
- within the membrane of neurone there are sodium ion channels- responsible for transporting sodium ions across the membrane
- the neuron ending in the pacinian corpuscle has a special type of sodium channel, stretch- mediated sodium channel
- when channel changes shape- permeability to sodium ions changes
How does a pacinian corpuscle convert mechanical pressure into nervous impulse? (6 steps)
1) resting state- stretch mediated sodium ion channels in sensory neuron are too narrow for sodium ions to pass through
2) Pressure applied to corpuscle- changes shape- membrane surrounding its neurone stretches
3) When membrane stretches, sodium ion channels widen- sodium ions can now diffuse into neurone
4) Influx of positive sodium ions changes the potential difference of the cell membrane- becomes depolarised- results in a generator potential\
5) generator potential creates an action potential (nerve impulse)- passes along the sensory neurone
6) Action potential transmitted across neurones to the CNS.
What is the sodium-potassium pump and what does it do?
For every two potassium ions that are pumped into membrane, 3 sodium ions are pumped out- resting state- creates a potential difference of -70mv - outside is more positive electrochemical gradient than inside
What is the resting potential?
The difference in the electrochemical gradient (-70mv)
- when neurone is NOT transmitting an impulse
- membrane is said to be polarised
- phospholipid bilayer prevents ions from diffusing across membrane
- need to be transported via protein channels, some are gated and some remain open
K+= leaky
What are the events that result in the creation of a resting potential?
1) Na+ ions are actively transported out of axon and K+ ions actively transported into axon by specific intrinsic proteins, the sodium potassium pump
- Every 3 sodium out, 2 potassium in
2) Result: more sodium ions outside membrane than inside axon cytoplasm, more potassium inside cytoplasm than outside axon, more positively charged ions outside than inside the cell
- Therefore sodium ions diffuse back down the electrochemical gradient+ potassium ions diffuse out of axon.
3) Most of the ‘gated’ sodium ion channels are closed- prevents movement of sodium ions
- potassium ion channels open- allowing K+ ions to diffuse OUT of axon
- Therefore more positively charged ions outside the axon than in cell
- Creates the resting potential across the membrane of -70mv
- Inside is negative in relativity to the outside
When does an action potential occur?
When protein channels in the axon membrane changes shape- results in change of voltage across membrane
- change in shape of protein results in channel opening/closing
channels known as voltage-gated ion channels
