Unit 6: Response, Heart rate & Nervous cooridination Flashcards
What does coordination involve?
nervous system and endocrine system
How do organisms increase their chance of survival?
by responding to changes in the environment
What is the endocrine system
releases hormones secreted by glands which travel to target cells
what are the divisions of the peripheral nervous system
autonomic
somatic
What is the function of the sensory neurons
possess receptors which are stimulated by a specific stimulus
impulse is transmitted to sensory to CNS
What is the motor neuron
transmit impulses to the effector (muscle/gland)
What is the relay neuron?
act as a link between sensory and motor
found in CNS
What is the function of the cell body
contains nucleus and other cell organelles
what is the axon
conducts nerve impulses
what is the mylein sheath
contains lipids and surrounds the axon
provides electrical insulation
What are the nodes of ranvier?
gaps in the myelin sheath along the axon
What are synaptic knobs
allow communication with other neurons/effectors
What is a reflex
rapid automatic involuntary response to a stimulus
what is a reflex arc
pathway taken by impulses during a reflex action
how many neurons are involved in a simple reflex
3 neurons
What happenes during a simple reflex
- receptors detect stimulus and transmit impulses along the sensory neurons to CNS
- sensory neurone synapses with relay neurone which passes impulse to motor neurone
- impulses are transmitted along motor neurons to the effector
What are the advantages of Reflexs
- prevent damage to tissues
- escape from predators
- detect changes so homeostasis can be achieved
What is a stimulus
a detectable change in the external/internal environment that produces a response in an organism
What are the function of taxes and kineses
maintain mobile organisms in a favourable environment
What is a Taxes
innate behavioural response
- whole animal/cell
What is a taxis
simple response in which direction of movement of the organism is determined by the direction of the stimulus
Which way can organisms move in taxes
towards (+ve) or away (-ve) from a directional stimulus
What is +ve phototaxis
movement of simple photosynthesising organisms towards light
increases their chance of survival
What is chemotaxis
movement towards/away from a high concentration of a particular substance
What is kineses
involves a change in the rate of movement and change in rate of turning
What is a tropism?
the growth of part of a plant in response to a directional stimulus
what phototropism occurs in plant shoots
positive
Shoots grow towards the light so leaves can absorb light for photosynthesis
what phototropism occurs in plant roots?
negative
Roots grow away from the light
what is geotropism?
Grown towards/away from gravity
What geotropism occurs in roots?
positive
roots grow towards gravity
Increases the probability that roots will grow into soil and absorb water and mineral ions
What geotropism occurs in shoots
negative and positive
Shoots grow away OR towords gravity
what is hydrotropism?
growing towards/away from water
what hydrotropism occurs in roots
positive
roots grow towards water
What hydrotropism occurs in shoots?
negative
Shoots grow away from water
what is chemotropism
Growing towards/away from chemicals
what chemotropism occurs in roots?
positive AND negative
Roots grow towards or away from certain chemicals
What is indoleacetic acid (IAA)
auxin
A plant growth factor that stimulates plant growth
Where is IAA produced?
in growing regions of a plant (shoots/tips)
It then diffuses from these growing regions to other tissues
It’s eventually an activated underrated by enzymes
How is IAA produced in the shoot?
cells in the shoot to produce IAA that diffuses down the shoot and is distributed equally stimulating upward growth of the shoot
how is IAA affected by a unidirectional light stimulus on the shoot?
causes the movement of IAA from the illuminated side to the shaded side of the shoot
what happens as the concentration of IAA builds up on the shaded side of the shoot
stimulates greater elongation of the cells on the shaded side
the shaded side grows faster, causing the shoot to bend towards the light
what effect does a high concentration of IAA have on roots?
Inhibits growth
Which part of the route detects a gravitational stimulus?
The root tip
A decapitated root does not show a geotropic response
The heart is myogenic. What does this mean?
Muscular contractions of the heart originate from within the heart muscle itself
What is the function of the heart rate increasing during exercise?
Increases blood to muscles bringing more oxygen/glucose and getting rid of carbon dioxide
what is the sinoatrial note?
act as a pacemaker and initiates the heartbeat
Patch of modified muscle cells in the wall of the right atrium which produces regular waves of electrical impulses
How does the atria contract?
impulses spread rapidly through the walls of the right/left atrium causing the atria to contract together
What happens before atrioventricular node reacts?
there is a 0.15 second delay before the AV node reacts to ensure the atria is empty and ventricles are full of blood and contract after the atria
what happens after the AV node reacts?
impulsive from the AB note travel rapidly through the purkyne tissue in the bundle of his to all parts of the ventricle
What happens when impulses reach the ventricles?
venteicles are stimulated to contract together starting at the bottom of the heart to push to blood up and out into the arteries
What neurotransmitter causes an increase in heart rate
noradrenaline by the sympathetic neurones
what neurotransmitter causes the slowing down of the heart rate
the release of acetylcholine by the parasympathetic neurones
What regulates heartrate
the cardiac centre in the medulla
how is heart rate sped up
medulla sends more impulses along the sympathetic neurone to the SAN
noradrenaline is released from sympathetic neurones stimulating SAN
how is heart rate slowed down
medulla sends more impulses along the parasympathetic neurones to the SAN
acetylcholine is released; inhibiting SAN
What effect does the increase in respiration during exercise have?
increases production of CO2
What is the effect of the increase in CO2 during exercise
CO2 dissolves in blood producing carbonic acid lowering the pH by increasing the conc oh H+ ions
chemoreceptors in the aortic and carotid bodies are stimulated
What are the function of chemoreceptors
transmit more impulses to the cardiac centre in the medulla
this increases heart rate by transmitting more impulses from the medulla via sympathetic neurones to the SAN
What happens when heart rate is returned to resting rate
conc of CO2 in blood had been reduced
fewer impulses are transmitted from chemoreceptors to medulla
What is the respiratory centre?
in the medulla
receives impulses from the chemoreceptors and increases rate of ventilation
What effect does increased blood flow to the heart have on the cardiac muscle?
causes cardiac muscle to contract more strongly pumping out an increased volume of blood
What are baroreceptors
located in wall of aorta and carotid artery
detect increase in blood pressure
What happenes if blood pressure is above normal
baroreceptors send more impulses to medulla stimulating the cardioinhibitory centre and inhibiting the cardioacceleratory centre
How is the heart rate decreased
more impulses are sent from the cardiac centre along parasympathetic neurones to the SAN preventing heart from overworking
What is the value of the resting potential inside the axon?
-70mV
What is the resting potential
the potential difference across the membrane of an axon when an impulse isn’t being transmitted
Which ions are in a polarised neurone?
more sodium ions outside the axon and more potassium ions inside the axon
How is the resting potential maintain
- membrane is differentially permeable
more permeable to the loss of K+ than intake of Na+ - Na/K pump actively transports 3 Na+ out and 2 K+ in against their diffusion gradients ensuring that an electrochemical gradient is maintained
What is a respiratory inhibitor
prevents production of ATP so Na/K pump cant function and conc of these ions will eventually reach equilibrium and the potential difference will be 0
What causes an action potential
when a receptor is stimulates above its threshold
What happens during delolarisation
increase in permeability of the axon to Na+
Na voltage gated channels open and Na+ diffuses down a conc gradient into axon and value increases to +40mV
What happens during repolarisation
Na channels close
K voltage gated channels open and K+ diffuse out of axon making it less + e
How does the Na/K pump restore the resting potential?
actively removes Na+ which have entered and returns K+ back into axon
What happens during hyper polarisation
membrane pitential becomes more negative bc K+ diffuses out slowly
What is the refractory period?
period after the formation of an action potential when a neurone cant generate another action potential
resulting in discrete impulses
ensures that impulse travels in one direction
What is the all or nothing principle
a stimulus must be above a certain threshold level for an impulse to be generated
a strong stimulus above threshold will result in a greater frequency of impulses than a weak stimulus
amplitide of impulses always remain the same
How does temperature affect the speed of conductance?
increase in temperature will increase speed of transmission up to a particular temperature
this is due to an increase in the diffusion of ions inside and out the axon
How does a temperature above optimum affect speed of concordance
denaturation of enzymes and proteins in the plasma membrane would stop the transmission
How does axon diameter affect speed of conductance
greater the diameter the faster less resistance
How does myelination affect speed of conductance?
myelinated neurones increase speed as action potential jumps from one gap (node of ranvier) to another to the next
depolarisation only occurs at the nodes > saltatory conduction
in non myelinated neurones depolarisation occurs along the whole membrane of the axon slowing down transmission
Why does the synaptic knob contain many mitochondria
to provide ATP for the synthesis of the neurotransmitter
What happens during synaptic transmission
- action potential reaches synaptic knob causing depolatisation of PreSM
- stimulated Ca2+ to open in PreSM and diffuse into synaptic knob
- cause vesicles to fuse with preSM and break open
- neurotransmitter acetylcholine is released and diffuses across synaptic cleft
- acetylcholine attatches to specific receptor on postSM
- stimulates entry of Na+ leading to depolarisation of postSM and transmission of an impulse
How is acetylcholine broken down then resynthesised
- broken down in postSM by enzyme acetylcholinesterase making acetyl and choline
- acetyl and choline is taken up into the synaptic knob by active transport and is resynthesised
What is spatial summation?
two or more impulses from different synaptic knobs arrive simultaneously at different regions on the same neurone
mores likely to reach threshold as there are more knobs
What is temporal summation?
two or more impulses arrive at the same place on the axon within a short period of time
more likely to reach threshold than if one impulse arrived
how do synapse give an inhibitory effect on the postSM?
by stimulating influx of negative Cl- ions and by stimulating removal of K+ causing a more -ve charge in the axon
its more difficult to reach threshold than
What is the neuromuscular junction?
The synaptic connection between a neuron and muscle fibre
Many drugs act on the neuromuscular junctions
How do drugs work by mimicking?
drugs have a similar structure to a normal transmitter and have the same effect they bind to receptors and transmission is faster
How do drugs work by blocking?
drugs have a similar structure in a normal transmitter, but do not produce the same effect
They fit into the receptors and prevent the normal transmitter from entering this stop the transmitter from having its effect so transmission is stopped
How do drugs work by preventing?
prevent the release of the transmitter substance from the preSM so that transmission is stopped
How do drugs work by inhibiting?
The inhibit the action of enzymes which hydrolyse neurotransmitters therefore more transmitter is present so transmission is enhanced
