Nervous coordination

How does the nervous system work

It uses nerve cells to pass electrical impulses along their length

Stimulate their target cells by secreting neurotransmitters, directly on them

Leads to rapid communication between specific parts of an organism .

Reponse produced often rapid,short lived and restricted to localised region of body.

How does the hormonal system work?

-produces hormones that are transported in the blood plasma to their target cells

Target cells have specific receptors on cell surface membrane and the change in concentration of hormones stimulate them .

Results in slower , less specific form of communication between parts of an organism

Reposnses are often long lasting and widespread

What is the difference between nervous system and the hormonal system?

Nervous system :

1.nerve impulse via neurones

2. Transmission = very rapid

3. Nerve impulse to specific parts of the body

4. Response is localised

5. Short lived

6. Temporary and reversible

Hormonal systems :

1.via hormones via blood stream

2. Relatively slow

3. Hormones travel to all parts of the body

4. Widespread

5. Slow

6. Long lasti8ng

7. Permanent and irreversible

What do neurones contain?

1. Cell body - which contains all the usual cell organelles - associated with production of neurotransmitters

2. Dendrons - extension of cell body - dendrites - carry nerve impulse to the cell body

3. Axon- a single long fibre that carry nerve impulses away from cell body

4. Schwann cells- surround the axon , protecting it and providing electrical insulation + carry out phagocytosis +play part in nerve regeneration

5. Myelin sheath- covering to the axon made up of Schwann cells

6. Nodes of ranvier - constriction between adjacent Schwann cells - where no myelin sheath

What is the advantage of a stimulus?

-increases the chance of survival for an organism = the ones that survive have a greater chance of raising offspring and passing the allel - selection pressure

What is taxes in biology?

Taxes is a directional movement by an organism in response to a stimulus, usually towards (positive taxes) or away (negative taxes) from it.

What is kinesis?

Kinesis is a non-directional movement away from or towards a stimulus, characterized by a change in the speed of movement rather than a change in direction and rate at which it changes direction

What is tropism?

Growth of plant in response to directional stimulus

What is the most favourable position for photosynthesis

Positive phototropism + negative gravitropism

How does phototoprism in a flowering plant work?

1. Shoot tips produce IAA = it is then transported down the shoot

2. IAA initially evenly transported through all regions

3. Light cause IAA move from light to shaded

4. Increase in conc of IAA as it builds up on shaded side = elongation of shoot faster rate = bends towards th light

How does gravitropism work ?

1. Cells in root tips produce IAA- initially evenly distributed

2. Gravity causes movement of IAA from Upper side to lower side

3. IAA inhibits elongation so as concentration of iAA increases. Lower side there will be greater elongation on the upper side = root bends down

What is the role of IAA?

Increase in plasticity of cell walls - young cell walls- (before mature and become more rigid )

This can be because of active transport of H ions from cytoplasm in to spaces in the cell walls causing an increase in plastcity= increases elongation by expansion

What is the r meaning of resting potential ans what is the value for it?

1. Membrane is polarised -this is due to the sodium - potassium ion pump

2. This pump moves 3 sodium ions out of the axon is active transport from low to high concentration via the pump

3. And also moves 2 potassium ions into the axon via active transport

4. Needs atp

5. Since more sodium ion are moved out of the axon the outside of the axon is more positively charged and the inside of the axon is less positively charged

6. Alongside with the potassium ion leak channel proteins that are continuously open - enable facilaitated diffusion of more K plus ions out of the axon down conctration gradient

• together this maintains a resting potential of :-0.7V

What is the reflex arc?

Stimulus- receptor - sensory neurone- co-ordination- motor neurone- effector

Table of nervous system

There is the CNS

PNS- sensory +motor neurone

Motor neurones- volountary (somatic) + involuntary (autonomic)

Autonomic- parasympathetic + sympathetic

What are the advantages of a reflex?

1.involountary- requires no desicion making skills of the brain

2. Protect the body from harm

3. Fast- short neurone pathway

4. Rapid- no decision making

What is the sympathetic nervous system?

1.stimualtes the effector + speeds up the activity

so they can cope with stressful situations -heightening awareness = fight or flight

What is the parasympathetic nervous system?

1. inhibits effectors + slows down activity

   • controls activities under normal resting conditions

   • It promotes relaxation and conserves energy, allowing the body to maintain homeostasis.

What is heart rate controlled by ?

myogenic muscle - contraction is initiated from within muscle itself - the heart's pacemaker= the stimulation determines heart beat

• within the wall of the right atrium - sinoatrial node which start the initial contraction stimulus

What are the sequence of events for one heart contraction?

1. The process begins when the sinoatrial (SA) node, known as the heart's pacemaker, generates a wave of electrical excitation. This wave spreads across the atria, causing them to contract and push blood into the ventricles. The contraction occurs due to the depolarization of cardiac muscle cells in the atria. A layer of non-conductive tissue called the atrioventricular (AV) septum prevents the wave from directly crossing to the ventricles, ensuring that the atria contract first.

2. The electrical impulse then reaches the atrioventricular (AV) node, located at the junction between the atria and ventricles. Here, there is a short delay, allowing time for the ventricles to fill with blood from the atria before contraction. After this delay, the impulse travels down the bundle of His. The bundle of His, which branches into left and right bundle branches, conducts the impulse down to the apex of the heart (the bottom) and across the atrioventricular septum.

3. From there, the impulse spreads quickly through the Purkinje fibers, which are specialized muscle fibers that ensure a rapid conduction of the impulse throughout the ventricular muscle. This coordinated pathway allows the ventricles to contract efficiently and simultaneously from the bottom upwards, pumping blood out of the heart through the aorta and pulmonary arteries. The sequence is crucial for maintaining effective circulation.

Why do you modify the resting heartrate?

rate is altered to meet the varying demands for oxygen

what are changes in heartrate controlled by

the medulla oblongata (in the brain)

What are the 2 centres in the medulla oblongata

1. centre = increases heart rate - linked to SAN = by sympathetc nervous system

2. centre = deceases heart rate - linked to SAN= by parasympathetic nervous system

what are the centres stimulated by ?

1. chemicals

2. pressure

how do chemoreceptors work?

1. increase muscular activity leads to more co2 produced = leads to increased respiration = leads to a decrease in ph of blood

2. chemical receptors in the carotid artery arteries increases the frequency of impulses to the medulla oblongata

3. centres in the medulla oblongata that speeds heart rate = leads to an increase in frequency of impulses to the SAN via the sympathetic nervous system

4. SAN to increase the heart rate = increase the blood flow to remove CO2 faster

5. CO2 concentration returns to normal

How do pressure receptors work?

pressure receptors occur within the wall of the carotid arteries and aorta

• when blood pressure increases

1. pressure receptors transmit more nervous impulses to the centre in the medulla oblongata = decrease heart rate

2. centre sends impulses via the parasympathetic nervous system to the SAN = decrease heart rate

• when blood pressure decreases

1. pressure receptors transmit more nervous impulses to centre in medulla oblongata = increases heart rate

2. centre sends impulses via sympathetic nervous system to the SAN - increases heart rate

what are features of the nervous system ?

localised

short- lived

rapid

what are features of the endocrine system?

widespread

longlasting

slower

what is the difference between the hormonal system and nervous system?

hormonal system:

1. communication via hormones

2. transmission through the bloodstream

3. slow and wide spread

4. hormones travel to all parts of the body

5. long lasting

6. effect may be permanent + irreversible

nervous system :

1.communciation is by nerve impulses

2. neurones

3. rapid and localised

4. short lived

5. efffects usually temporary and reversible

what does the axon do

carry nerve impulses away from the cell body

what is the myelin sheath made of ?

schwann cells

it is a lipid- that enable electrical insulation and phagocytosis

what does the cell body of a neurone do ?

assosciation with the production of proteins and neurotransmitters

what is a nerve impulse ?

self propogating wave of electrical activity that travels down along an axon

a temporary reversal of electrical potential difference across axon membrane

what is resting potential

1. Ion Movement: 3 Sodium ions (Na+) are actively transported out of the neuron, while 2 potassium ions (K+) are transported into the neuron by the sodium-potassium pump via active transport

2. Polarization: This movement creates a concentration gradient, resulting in a higher concentration of Na+ outside the neuron and a higher concentration of K+ inside the neuron. more positive outside less positive inside

3. Charge Difference: Due to this ion movement, the inside of the neuron becomes negatively charged relative to the outside, establishing a resting potential typically around -70 mV. or other.

4. Equilibrium: The resting potential reflects a state of equilibrium where no net movement of ions occurs, allowing the neuron to be ready to respond to a new stimulus.

5. also potassium ion leak channel proteins which enable movement of potassium ions out of the axon via facilitated diffusion

why is there a sodium - potassium ion pump

because of the phospholipid bilayer - it prevents sodium and potassium ions from diffusing across it

what is action potential? (along an unmylenated axon)

• stimulus of a sufficient size above threshold - detected by receptors = cause an increase in permeability of axon membrane to sodium ions by opening the sodium ion voltage gated channel proteins .

• this would cause the sodium ions to rapidly diffuse in via facilitated diffusion into the axon down the concentration gradient - this leads to a reversal of potential difference in the membrane = inside of the axon becomes more positive and therefore becomes depolarised

• as sodium ions diffusion in this causes more sodium ion channel proteins to open and increase the influx of sodium ion into the axon

• once an action potential is established voltage specific gated na + channel protein closes

• voltage gated K + channel protein opens and this causes the K+ ions to diffuse out of the Chanel protein - known as re polarisation + (leak channel proteins )

• There is an outward diffusion - temporary overshoot of the electrical gradient - this causes th inside of the axon to become more negative than usual= hyper polarisation - the K + channel proteins then close + activities of the K+- Na+ pump resume

• Resting potential is re established

What must happen before an new action potential occurs

Another action potential cannot occur until a resting potential reached again

What is the passage of an action potential along a mylenated axon

fatty sheath of myelin= acts as an electrical insulator - prevents an action potential from forming

breaks in the myelin insulation - known as nodes of ranvier

1. Action potential can occur at these nodes and it jumps from Node to Node - known as saltatory conduction

2. at each node the membrane is depolarised due to the influx of sodium ions causing action potential to propagate rapidly along axon- there is faster transmission of nerve impulses vs unmylinated

What is the speed of the nerve impulse affected by ?

1. Myelin sheath - saltatory conduction

2. Diameter of the axon - increase diameter = increase in speed of conduction = because there is less leakage of ions from a large axon= leakage makes membrane potential harder to maintain

3. Temperature = affects the rate of diffusion of ions =ncrease faster nerve impulses = K=- NA+ pump = enzymes so can increase up to a point

What is the all or nothing principle

The level of stimulus must be above threshold to trigger an action potential - nerve impulse to occur

What does the size of stimulus affect ?

Larger stimulus = frequency of of impulses generated in a given time increases

What is the refractory period?

The refractory period is the time following an action potential during which a neuron is unable to fire another action potential. It consists of two phases: the absolute refractory period, where no stimulus can trigger another action potential, and the relative refractory period, where a stronger than usual stimulus is needed.

What is the equation including refractory period ?

1/ refractory period = frequency

What is the importance of refractory period?

1. It ensure that action potential is only propagated in one direction ONLY - action potential can only pass form active to resting because actio potential cannot be propagated in a region that is refractory

2. Produces discrete impulses : due to the refractory period new action potential annot be formed immediately behind one another - ensures the action potential is separated from one another

3. Imits the number of action potentials that can pass along an axon in a given time - thus limits the strength fo stimulus that can detected

What is the structure of a synapse ?

• presynaptic neuron

• Post synaptic neuron

• Axon of neuron ends in synaptic knob

• Synaptic vesicle

• Synaptic cleft

What does synaptic knob possess?

• mitochondria

• Increase amount of er

Ths is required to manufacture neurotransmitter

What is the purpose of the synaptic vesicle

Stores neurotransmitter d once it is released from presynaptic neuron is diffuses across to post synaptic neuron which has specific receptors proteins to receive them

What is summation?

Summation is the process by which multiple excitatory and inhibitory signals combine at a postsynaptic neuron to determine whether an action potential will be triggered.

What are the different types of summation and the differences

1. Spatial summation - different presynaptic neuron together release enough neurotransmitter = above threshold of post synaptic = together triggers and action potentials

   2. Temporal - single presynaptic neuron eleases neurotransmitters many times over short time period = cause concentration of NT to be above threshold - trigger action potential

What is inhibition in a synapse

Makes t les likely a new action potential will be created in the post synaptic neuron

What are the taxes of inhibition in a synapse

1. Pre synaptic neuron releases a type of NT that binds to the cl- protein channels on the post synaptic neuroen

2. Cause them to open

3. CL- will move into the pre synaptic neurone via facilitated diffusion

4. The binding of theNT will cause the opening of k+ protein channel

5. K+ ions wil move OUT of tje post synaptic neuron

6. This causes the snide of the post synaptic neuron to become more negative and the outside to become more positive = hyper polarisation = makes it less likely for action potential because a larger influx of NA + ions needed

What are the functions of a synapse ?

• its transmits info from one Nueron to another

• Single impulse along 1 neuron can lead to initiate new impulses a no. Of different neurones at a synapse

  • Essentially single stimulus = no. Of simultaneous responses

• No of pulses can be combined at a synapse = allows nerve impulses from receptors reacting to different stimuli to contribute to one single response

How does the function at a synapse occur ?

1. NT are only ade in the pre synaptic neurone

2. Neurotransmitters stored in presynaptic vesicles

3. When action potential reaches the synaptic knob membranes of synaptic vesicle will fuse with the presynaptic membrane = release the nT

4. Neurotransmitter diffuses across the synpatic clefts binds to a specific receptor protein on the post synaptic neurone = new action potential in the post synaptic neuron = excitatory synapse

How did drugs act on a synapse ?

1. Stimulate the nervous system by creating more action potentials int he post synaptic neurone

   • drugs can do this y mimicking hte NT - stimulate more NT or inhibit the enzyme that causes the breakdown of NT

2. Inhibit the nervous system - by creating fewer action potentials n the pos synaptic neurone

   • Drug will inhibit the actio of excitatory NT which will reduce a particular effect or it will inhibit NT - enhance a particular effect

How does a synapse cause an action potential?

1. Arrival of action potential at the end of presynaptic neurone causes the Ca ion protein channel to open + ener the synaptic knob by facilitated diffusion

2. Influx of CA into the presynaptic neuron causes synpatic vesicles to fuse with the presynaptic membrane releasing acetyl choline

3. Acetylcholine will exocytosis across the synpatic cleft it then wil bind to the receptor site on the Sodium ion protein Channel on the post synaptic neurone which wil then cause them to open and then this enables Na + ions to diffuse in rapidl down the conc gradient = DEPOLARISING THE MOLCUEL

4. Influx of na+ generates a new action potential in the post synaptic neuron

5. Acetylcholinesterase wil hydrolyse the acetylcholine - choline and ethanoic acid which will diffuse back across the synpatic cleft into the presynaptic neuron

6. ATP is released by mitochondria which will recombine the choline and ethanoic acid - this is then stored in synpatic vesicles for future use

7. Sodium ion channels close bc of absence fo acetylcholine in receptor sites

What are the 4 uses of atp at synapse

1. Resynthesis of acetylcholine

2. Actively transport Ca ions back out of synapse

3. Resynthesis of vesicles

4. Actively transport acetylcholine

what is the difference between fast and slow twitch muscles

Slow Twitch:

• contain a large store of myglobin-