human nervous system and endocrine system

what do relay neurones do and where are they found?

They are found in the CNS and they allow sensory and motor neurones to communicate

what is the pathway of the reflex arc?

stimulus—> receptor—>sensory neurone—>relay neurone/CNS—>motor neurone—>effector—>response

what is the synapse?

the site of transmission of electric nerve impulses between two neurones

what is a reflex action?

a rapid, unconscious, automatic movement in response to stimuli to protect the body from harm

what is an effector?

muscles or glands which bring about changes that restore optimum levels

what is the reflex arc?

term for the neurone pathway that underlies our unconscious reflexes

what is a receptor?

organs or cells that detect stimuli

define a reflex action, then describe the reflex arc involved in the blinking response to a flashing light

• a reflex action is a quick, unconscious movement

• the flashing light is detected by receptors in the back of the eye(retina)

• then the electrical impulse goes along to the sensory neurone

• when the impulse from the sensory neurone arrives at the synapse with a relay neurone, chemicals are released

• then the chemicals diffuse across to the relay neurone where it sets off a new electrical impulse that travels along the relay neurone (the synapse transmits the signal to the spinal cord where there it synapses with the relay neurone)

• when the impulse reaches the synapse between the relay neurone and the motor neurone chemicals are released and

• again the chemicals diffuse across the synapse starting a new electrical impulse along the motor neurone

• which sends the impulse to the effector

• in this case the effector is the muscles in the eyelids which contract to enable you to blink

what is the CNS and its function(central nervous system)

it’s made up of the brain and spinal cord, it takes in sensory info, decides what needs to be done, then sends out orders to the rest of the body

how are nerve cells adapted for their function?

• multiple dendrites allowing each neurone to connect to many others

• the axon is long allowing the neurone to transmit electrical impulses across large distances very quickly

• the axon is coated in an insulating myelin sheath to insulate the axon and allows electrical impulses to travel faster and more efficiently

how does an electrical impulse travel from neuron to neuron?

the electrical impulse travels along the neuron’s axon rapidly and once it reaches the nerve ending it causes the release of some chemical messengers called neurotransmitters which diffuse across the synapse to the next nerve cell where they trigger another electrical impulse

what is the endocrine system

consists of glands found throughout the body ; all these glands secrete hormones

what are hormones

small chemical molecules released from glands into the bloodstream that travel to certain tissues to trigger a change inside cells

what is the pituitary gland

the master gland, found in next to the brain, that tells other glands to release their hormones

compare the endocrine system and the nervous system

1. endocrine system relies on hormones BUT nervous system relies on electrical impulses

2. hormones are transported by blood BUT electrcial impulses are transported by nerve cells

3. hormones spread more slowly BUT electrical impulses act very fast

4. hormones effects last longer BUT electrical impulses effects don’t last very long

5. hormones act more generally BUT electrcial impulses are precise

where is adrenaline secreted from

adrenal glands

when is adrenaline produced

during the fight or flight response when you get scared, stressed or need to excercise

what does adrenaline do

1. increases heart rate

2. increases blood pressure

3. increases blood flow to muscles

4. increases blood sugar levels by stimulating the liver to break down glycogen into glucose

where is thyroxine produced

thyroid gland

what does thyroxine do

growth and development, increases metabolic rate

how is the production of thyroxine regulated

by the hypothalamus and pituitary gland

what happens if thyroxine levels are too low

the pituitary gland releases TSH, this then stimulates the thyroid gland to release more thyroxine, so thyroxine levels in the blood increase back up to normal

what happens if thyroxine levels are too high?

the thyroxine will inhibit the pituitary gland from producing TSH, less TSH means that the thyroid gland won’t release as much thyroxine so thyroxine levels in the blood fall back to normal

what is a negative feedback loop

Mechanism to lower raised levels of something, and to raise reduced levels of something.