Heart rate control , receptors and nerves

Question 1

Pacinian corpuscle

Answer 1

-Pressure receptor found in skin
-Contains sensory neurone which has stretch mediated sodium channels
-When pressure is applied on these channels the sodium ion channels widen and open which can create a generator potential due to more sodium ions diffusing to sensory neurone

Question 2

Rods

Answer 2

-To create a generator potential , rhodopsin must be broken down by light
-Detect light at low intensity as many rods connect to one sensory neurone this also causes low visual acuity
-low in fovea in lower light zones

Question 3

Cones

Answer 3

-3 types which contain different coloured iodipsin pigments
-iodipisin is only broken down at high light intensities so need high light for action potential
-High visual acuity
-fovea high density

Question 4

Myogenic control of the heart

Answer 4

-SAN releases wave of depolarisation across atria causing contraction
-This wave will then reach the AVN which releases another depolarisation wave
-the wave is prevented from reaching ventricles due to non conductive tissue
-Goes down septum and purkyne fibres
-ventricles will then contract at a small delay as AVN transmits second wave

Question 5

Heart rate control

Answer 5

-Medulla oblongata
-Change because of PH , pressure
-Increase heart rate via sympathetic nervous system
-Decrease heart rate via parasympathetic nervous system

Question 6

How is resting potential established

Answer 6

-Sodium potassium pump + active transport which involves ATP
-Electrochemical gradient where Potassium ions diffuse out and sodium ions diffuse in
-As membrane is more permeable to Potassium ions diffusing out than sodium ions moving in

Question 7

Depolarisation

Answer 7

-Stimuli opens Sodium ion channels so more sodium moves along axon so less negative
-Membrane is more permeable to sodium ions than potassium ions

Question 8

All or nothing principle

Answer 8

-If voltage does not exceed -55mv no impulse is produced but if voltage exceeds -55mv then impulse always produced

Question 9

Importance of refractory period

Answer 9

-Ensures each action potential is separate
-Allows sodium ion channels to recover
-Limits impulses so no overstimulation

Question 10

factors which affect the rate of conduction

Answer 10

-Saltatory conduction , action potentials jump from nodes of Ranvier as action potentials cannot go along insulated myelin sheath , so faster
-Diameter of axon , wider diameter increases speed of conduction as less leakage
-temperature , ions diffuse faster and respiratory enzymes work more optimally to create ATP used in Polarisation

Question 11

How action potential is transported across synaptic cleft

Answer 11

-Action potential arrives at synaptic knob , causing it to depolarise which opens calcium ion channels
-Calcium ions then diffuse into the synaptic knob
-Vesicles containing neurotransmitter fuse with presynaptic membrane , where they are then released into the cleft
-Neurotransmitter diffuses down concentration gradient to post synaptic neurone where it binds to complementary receptor
-Sodium ion channels on post synaptic neurone then open which allows sodium to diffuse in which may create generator potential
This process is unidirectional as
-Concentration gradient only allows diffusion from pre to post synaptic neurone
-complementary receptors are only on post synaptic neurone

Question 12

Summation

Answer 12

-Spatial is where different neurones collectively trigger new action potential by combining neurotransmitters
-Temporal is where one neurone releases lots of neurotransmitters quickly