Stimuli, both internal and external, are detected and lead to a response

What do relay neurones do?

The brain and spinal cord contain relay neurones which link sensory neurones to motor neurones.So they transmit electrical impulses BETWEEN sensory neurones.

The peripheral system ALSO has 2 different systems... what are these?

The conscious/somatic nervous system which controls stuff like running etc. The autonomic system which controls unconscious activites e.g. digestion.

What is potential difference?

The difference in voltage across the membrane.

What is a negative tropism?

The growth away from the stimulus.

What is geotropism?

The growth of a plant in response to gravity.

What is phototropism?

The growth of a plant in response to light.

What is a positive tropism?

The growth towards the stimulus.

how is the heart rate DECREASED? (chemoreceptors)

The increased heart rate decreases the CO2 levels causing an increase in pH. Chemoreceptors are no longer stimulated to...

Discuss the importance of simple reflexes.

The rapid response reduces damage. Ensures many essential homeostatic control mechanisms occur. Conscious regions of the brain are not overloaded with homeostatic control ok.

What do motor neurones do?

These carry impulses away from the brain or spinal cord/ central nervous system, towards the effector.

What do sensory neurones do?

They carry electrical impulses towards the brain or spinal cord/ central nervous system.

what is trichromatic vision and what does it apply to?

Trichromatic vision applies to CONES as they give information in colour.

What are tropisms?

Tropisms are the growth movements of part of a plant in response to a directional stimulus. (This maintains the roots and shoots of flowering plants in a favourable environment.)

How do plants respond to stimuli?

Using growth factors. These are produced in the growing regions of the plants and move to where they are needed.

What is the blind spot?

Where the optic nerve leaves the retina. There are no cones here.

noradrenaline onto the SA node which then sends out...

a greater frequency of impulses across the atria and ventricles, increasing the heart rate.

SA node. The neurones release...

acetylcholine on to the SA node. The SA node sends out a...

the SA node sends out an increased frequency of impulses across the atrial and ventricular muscle causing..

an increase in heart rate.

What is a stimulus?

any change in the internal or external environment.

carbonic acid. therefore reducing...

blood pH. Chemoreceptors in the...

cardioregulatory centre has 2 subcentres. what are these?

cardioinhibitory centre cardioaccelerator centre

decreased frequency of impulses across the atria and ventricles causing a...

decrease in heart rate.

walls of the carotid/aortic arteries detect the decrease in pH and set up...

impulses. an increased frequency of impulses pass to the

what happens in the cardioinhibitory centre?

it decreases the heart rate and is linked to SA node by parasympathetic neurones.

what happens in the cardioaccelerator centre?

it increases heart rate and is linked to SA node by sympathetic neurones.

walls of the carotid arteries are stimulated by the increase in pressure and send an increased frequency of impulses to the inhibitory centre in the...

medulla. The inhibitory centre sends impulses along the parasympathetic neurones to the SA node. The neurone releases..

SA node. the neurones release...

noradrenaline which bind to receptors on SA node.

send impulses to the medulla. This causes the inhibitory centre in the medulla to...

send out an increased frequency of impulses along the parasympathetic neurones to the...

cardioregulatory centre of the medulla and cause an increased frequency of impulses to pass down ...

sympathetic neurones to the...

aorta and carotid arteries send impulses to the cardioaccelerator centre in the medulla. This centre sends impulses along the...

sympathetic neurons to the SA node. The neurone releases...

When blood pressure is high, how is heart rate slowed down? (pressure receptors)

the PRESSURE receptors in the...

What are the 2 diff systems the nervous sytem is split into?

the central nervous sytem (relay neuroens) and the peripheral nervous system (motor neurones)

where is the cardioregulatory centre located?

the medulla of the brain.

what happens when the rhodopsin and iodopsin absorb light?

they are broken down. 'bleached'

How do receptors and effectors communicate?

via the NERVOUS or WHOREMONAL system. or sometimes both

what is the retina described as?

'inverted' because light has to pass through sensory bipolar neurones before it strikes rod/cones.

More about rods and setting up generator potentials:

- In the dark, rods continuously release an inhibitory transmitter which stops an impulse being transmitted by the bipolar neurone. -So, when light strikes the rod, the opsin causes sodium ion channels to close therefore resulting in the membrane becoming hyperpolarized. -The rod then stops releasing the inhibitory neurotransmitter substance and the lack of it causes bipolar neurone to become depolarized. -An impulse continues onto the sensory neurones in the optic nerve and then to the brain.

Differences between chemical mediators and hormones?

- chemical mediators are secreted from cells that are all over the body, not just from glands. - their target cells are right next to where the chemical mediator is produced so they stimulate a local response. -They only have to travel a short distance to their target cells so response is quicker.

hormonal system:

- made up of glands and hormones.

-Discuss Visual acuity in rods and cones.

-Cones give high visual acuity because they are close together. (one cone joins one neurone). So when light from 2 points hits 2 cones, 2 action potentials go to the brain. This is how we distinguish them as 2 s e p e r a t e points. -ROD chix give low visual acuity because many rods join the SAME neurone which means light from 2 objects close together cant be seen as apart.

What are histamines and what do they do?

-Histamine is a chemical mediator that is stored in white blood cells. -It is released in response to the body being injured or infected. -It increases the permeability of capillaries nearby to allow more white blood cell's to move out of blood into the infected or injured area. causes redness and itching.

What is IAA and where is it produced?

-Indoleacetic acid. -It is produced in the tips of shoots in flowering plants. -It moves by diffusion and active transport over short distances. -it moves via the phloem over long distances. -So different parts of the plant have different amounts of IAA and so uneven distribution = uneven growth of plant.

Where are cones distributed?

-Packed together in the fovea. -Fewer at the periphery of the retina.

What are prostaglandins and what do they do?

-Prostaglandins are a group of chemical mediators produced by most cells of the body. -Found in cell membranes. -Cause dilation of small arteries/ioles. -released following injury. -Increase permeability of capillaries. -Affects blood pressure and neurotransmitters.

-Discuss sensitivity in terms of ROD chix and cones.

-ROD chix are v sensitive to light. (because many rods join one neurone, many weak generator potentials combine to reach the threshold and then trigger an action potential) -Cones are not as sensitive as rods. (They only fire action potentials in bright light, compared to RODS who fire action potentials in dim light). One cone joins one neurone so it takes longer and more light to reach the threshold and trigger an action potential.

Where are ROD chix distributed?

-Rods are mainly found in the peripheral parts of the retina. -There are no rods at the fovea/blind spot. -There are more rods AROUND the fovea, less at edges of retina.

What is the generator potential?

-The change in potential difference due to a stimulus. -If the generator reaches a certain level called the threshold level, it will trigger an action potential.

structure of a pacinian corpuscle ?

-The single sensory neurone of a pacininian corpuscle is at the centre of layers of tissue. -They respond to mechanical stimuli like pressure. -They occur deep in the skin,fingers, soles of feet and external genitalia, joints, ligaments and tendons. -The sensory neurone ending at the centre of the pacinian corpuscle has a Na+ channel in its plasma membrane. (the stretch mediated sodium ion channel).

SANAS REALLY COOL EXCITED... RESPONSE.

-a Stimulus is detected by Receptor cells and an electrical impulse is then sent along a senory neurone. When the electricl impulse reaches the end of a neurone, chemicals called NEUROTRANSMITTER CHEMICALS take this info across to next mans neurone. Next mans neurone then sends an electrical impulse. -the CNS processes the information, decides what to do about it and send impulses along motor neurones to an Effector!!!!! Your body responds with the appropriate response.

what is a gland?

-a gland is a group of cells that are specialised to secrete useful substances such, such as a hormone.

how is the heart rate INCREASED? (chemoreceptors)

-higher respiration rate during exercise produces CO2 which forms...

Nervous sytem properties:

1. Reponose is localised. (Because when an electrical impulse reaches the end of a neurone, neurotransmitter are secreted DIRECTLY onto cells.) 2. The response is short-lived. ( Because neurotransmitters are QUICKLY REMOVED once theyve done their job.) 3. Response is rapid. (because electrical impulses are REEEALLY fast.)

Features of sensory reception?

1. The Pacinian corpuscle is used to illustrate that the receptors only respond to specific stimuli. 2. The Pacinian corpuscle is specific to a single type of stimulus. 3. All receptors convert the energy of a stimulus into a nerve impulse, this is known as a generator potential. 4. it produces a generator potential by acting as a transducer (a transducer converts information provided by a stimulus into a form that is understood by nerve impulses.)

How does light striking a rod lead to the impule passing to the brain?

1. When light strikes Rhodopsin in the rods, it is bleached/broken into retinal and opsin. 2. The opsin produced binds to sodium ion channels. 3. Thus causing sodium channels in the rod cell membrane to open, causing sodium ions to diffuse in and depolarize the membrane. Basically, a generator potential is set up.

How does the pacinian corpuscle function?

1. When the neurone of pacinian corpuscle is in resting potential state, stretch mediated sodium ion channels are too narrow to allow sodium ions to pass along them. 2. When pressure is applied to pacinian corpuscle, the PC changes shape and meembrane around it's neurone becomes stretched. 3. The stretching causes NA+ ion channels to widen, NA+ diffuse into neurone. 4.Influx of Na+ causes membrane to become depolarised, producing a generator potential. 5. The generator potential then creates an action potential (IF IT REACHES THE THRESHOLD) that passes along the neurone and then to the CNS.

How to photoreceptors convert light into an electrical impulse?

1.Light enters eye, hits photorecepors, is absorbed by light sensitive pigments. 2. Light bleaches pigments, causing a chemical change and altering the membrane permeability so its more permeable to sodium 3. A generator potential is created and if it reaches the threshold a nerve impulse is sent along a bipolar neurone. 4. The bipolar neurones connect photoreceptors to the optic nerve which takes impulses to the brain.

Hormonal system properties:

1.Slower. (Because the hormones arent released directly onto their target cells - they must travel in the blood to get there) 2. long lasting effect. (because hormones are not broken down as quickly as neurotransitters.) 3. widespread response. Hormones are transported all over the body)

What is gibberellin?

A growth factor that stimulates flowering and seed germination.

What is Kinesis?

A non-directional movement response of the organism where the rate of movement is related to the intensity of the stimulus, not the direction of the stimulus.

What is Taxis?

A simple movement response of the whole organism, the direction of which is determined by the stimulus.

The autonomic system is 'antaganostic.' WHY????????

BCOZ you can respond more rapidly and precisely to changes.

How do organisms increase their chance of survival?

By responding to changes in their environment.

what stimuli does the cardio regulatory centre respond to?

CO2 levels, pH levels, blood pressure.

What are effectors?

Cells that bring about a response to a stimulus to produce an effct. E.g.muscle cells.

What is the PARAsympathetic nervous system?

Controls bodys activities under normal resting conditions so calms body down. [(rest n digest ;)] system.

acetyl choline onto the SA node which then send out...

FEWER impulses across the atria and ventricles therefore decreasing the heart rate.

What happens in the peripheral system?

It is made up of the neurones that connect the central nervous system to the rest of the body.

What is the sympathetic nervous sytem?

It prepares the body for action (used in stressful situations e.g. increasing heart rate) 'fight or flight' system.

What are histamine and prostaglandins?

Local chemical mediators released by some mammalian cells and affect only cells in their immediate vicinity.

what is monochromatic vision and what does it apply to?

Monochromatic vision applies to RODs as they can only give information in black and white.

When a stimulus is detected, the cell membrane is excited and becomes more...

PERMEABLE. Therefore allowing more ions to move in and out of the cell - altering the potential difference.

Roots are...

Positively geotropic so they grow downwards and negatively phototropic so they grow away from light.

Shoots are...

Positively phototropic so they grow toward light and negatively geotropic so they grow upwards.

When blood pressure is low, how is heart rate increased?(pressure receptors)

Pressure receptors in the walls of the...

What are receptors?

Receptors detect stimuli. They can be cells or proteins on cell surface membrances.

The eye. what are rods and cones?

Rods and cones in the retina are light receptors and contain internal membranes called lamellae, which hold the light sensitive pigments.

The autonomic system ALSO has 2 different systems. What are these.

SYMPATHETIC AND PARASYMPATHETIC.

what has a high density of cones?

Fovea.

What are auxins?

Growth factors that stimulate the growth of shoots by cell elongation. (when cells become loose and stretchy so it gets longer). ~But high conc of auxins inhibit growth in roots.~

what are hormones?

Hormones are chemical messengers.

IAA in response to phototropism?

IAA moves to the more shaded parts of the shoots and roots so there is uneven growth. -With the shoot, the IAA causes elongation of cells and so the shoot to bend towards light. -With the root, IAA inhibits growth so the root bends away from the light.

IAA response to geotropism?

IAA moves to the underside of shoots and roots so there is uneven growth. -With the shoot, the cells elongate and so shoot grows upwards. -With the root, growth is ihibited so the root grows downwards.m

-What is the photosensitive pigment in rods and cones?

In cones it is IODOPSIN. In rods it is RHODOPSIN.