coordinace test Flashcards
what is homeostasis
the maintenance of a constant internal environment
examples of homeostasis:
body water content
body temperature
what does a co-ordinated response require
stimulus, receptor and effector
how does the nervous system control responses
information is sent as electrical impulses down neurones at high speeds allowing rapid responses to stimuli
it coordinates activities of sensory receptors, decision making centers and effectors
it is used to control functions that need instant response
how does the endocrine system control responses
information is sent as chemical substances (eg hormones) in the blood stream and so can circulate the whole body
hormones transmit information from one part of the organism to another and bring about a change (they provide a signal that triggers a response)
they alter the activity of one or more specific target organs
hormones control functions that do not need instant responses
hormones are produced by endocrine glands
differences between the endocrine and nervous system
nervous system is made up of Nerves (bundles of neurones), brain, spinal cord
endocrine system is made up of glands
nervous system sends electrical impulses
endocrine system sends chemical hormones
nervous system is very fast acting
endocrine system is slower acting
nervous system has a short duration of effect
endocrine has a longer duration effect
what does the central nervous system consist of
the brain and spinal cord which are linked to sense organs by nerves
how do rapid responses happen
stimulation of receptors in the sense organs which send electrical impulses along nerves into and out of the CNS
what is the role neurotransmitters at synapses
neurones don’t touch each other
Where the dendrites of two neurones meet (to make a connection between the neurones) a junction known as a synapse is formed
at the synapse there is a very small gap between the neurones (synaptic gap)
the electrical impulses cannot travel directly from one neurone to the other to the next due to the gap
Instead, the electrical signal is briefly converted to a chemical signal that can cross the gap
The chemical signalling molecules used to transfer the signal between neurones at a synapse are known as neurotransmitters
Once these neurotransmitters cross the synaptic cleft and meet the neurone on the opposite side, the signal is converted back into an electrical impulse, which can then pass along the neurone
how is an impulse passed across a synapse
The electrical impulse travels along the axon of the first neurone (known as the presynaptic neurone)
This triggers the end of the presynaptic neurone to release chemicals called neurotransmitters from vesicles
These vesicles fuse with the presynaptic membrane, releasing their contents into the gap
The neurotransmitters diffuse across the synaptic cleft and bind with receptor molecules on the membrane of the second neurone (known as the postsynaptic membrane)
This stimulates the second neurone to generate an electrical impulse (which then travels down the second axon)
The neurotransmitters are then destroyed to prevent continued stimulation of the second neurone (otherwise the neurotransmitters would cause repeated impulses to be sent)
Synapses ensure that impulses only travel in one direction, avoiding the confusion that would be caused within the nervous system if impulses were able to travel in both directions
structure and functioning of a simple reflex arc illustrated by withdrawal of a finger from a hot object
the hot object touching the skin (stimulus)
temperature receptors detect change in temperature (receptor)
sensory neurone sends electrical impulses to the spinal cord (coordinator)
sensory neurone connects a synapse to a relay neurone which then connects to a motor neurone
impulse travels along motor neuron and out of the spinal cord to the arm muscles (effector)
muscle contracts and arm moves off hot object (response)
what is a reflex response
A reflex response (also known as an involuntary response) does not involve the conscious part of the brain as the coordinator of the reaction
Awareness of a response having happened occurs after the response has been carried out
Responses are therefore automatic and rapid – this helps to minimise damage to the body and aids survival
Pain-withdrawal, blinking, and coughing are all examples of reflex responses that help us to avoid serious injury, such as damage to the eye or choking
what is a reflex arc
the pathway of a reflex response (specifically, the pathway taken by electrical impulses as they travel along neurones)
structure and function of the eye as a receptor
Cornea - transparent lens that refracts light as it enters the eye
Iris - controls how much light enters the pupil
Lens - transparent disc that can change shape to focus light onto the retina
Retina - contains light receptor cells – rods (detect light intensity) and cones (detect colour)
Optic nerve - sensory neuron that carries impulses between the eye and the brain
Pupil - hole that allows light to enter the eye
Conjunctiva - a clear membrane that covers the white of the eye and the inside of the eyelids; it lubricates the eye and provides protection from external irritants
Ciliary muscle - a ring of muscle that contracts and relaxes to change the shape of the lens
Suspensory ligaments - ligaments that connect the ciliary muscle to the lens
Sclera - the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye
Fovea - a region of the retina with the highest density of cones (colour detecting cells) where the eye sees particularly good detail
Blind spot - the point at which the optic nerve leaves the eye, where there are no receptor cells
function of the eye in focusing on near and far objects
The lens is elastic and its shape can be changed when the suspensory ligaments attached to it become tight or loose
The changes are brought about by the contraction or relaxation of the ciliary muscles
When an object is close up:
The ciliary muscles contract (the ring of muscle decreases in diameter)
This causes the suspensory ligaments to loosen
This stops the suspensory ligaments from pulling on the lens, which allows the lens to become fatter
Light is refracted more
When an object is far away:
The ciliary muscles relax (the ring of muscle increases in diameter)
This causes the suspensory ligaments to tighten
The suspensory ligaments pull on the lens, causing it to become thinner
Light is refracted less
role of the skin in temperature regulation - too hot
sweat glands - are active, they secrete sweat which evaporates from the skin carrying heat away from the body cooling the skin
muscles - not shivering
hairs - the hair erector muscles in the skin relax , causing the hairs to lie flat which stops them from forming an insulating layer as they can’t trap any air which allows air to circulate over the skin and allows heat loss via radiation
capillaries near skin - dilate due to the shunt vessel constricting so more blood flows closer to the skin allowing more heat loss via radiation (vasodilation)
