Topic 6- Responding to changes in environment Flashcards
what is a stimulus?
change in the internal or external environment of an organism
what is a receptor?
detects the stimulus to coordinate a response
what is taxis?
directional response to a stimulus
positive- towards
negative- away
what is kinesis?
non- directional response to stimulus
central nervous system
made of brain and spinal cord
peripheral nervous system
pairs of nerves originating from the brain or spinal cord
sensory neurones
carry nerve impulses from receptors to CNS
motor neurones
carry nerve impulses away from the CNS to receptors
voluntary nervous system
carries nerve impulses to body muscles and is under conscious control
autonomic nervous system
carries nerve impulses to glands, smooth muscle and cardiac muscle and is carried out subconsciously
simple reflex arc
stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
importance of reflex arcs
1) involuntary meaning brain is left to carry out more complex responses
2) protect body from harm
3) fast due to very few synapses
pacinian corpuscle
detects mechanical pressure (mechanoreceptor)
at resting potential when sodium ion channels are too narrow for Na+ to pass through
when pressure is applied, the layers are distorted and stretch-mediated sodium ion channels open
influx of Na+ depolarises the membrane producing a generator potential therefore producing an action potential
where are rod and cone cells found?
fovea (cone)
retina (rod)
rod cells
~ higher density
~ cannot distinguish between different wavelengths meaning colour can’t be seen
~ multiple rod cells attached to one bipolar neurone leading to retinal convergence
~ higher chance of threshold being reached
~ help us to see when light is low
~ contain rhodopsin
~ low visual acuity
cone cells
~ three types each responding to different wavelengths meaning we can see in colour
~ lower density
~ each cone cell attached to a bipolar neurone leading to high visual acuity
~ contain pigment iodopsin
~ can only respond to high light intensity
sympathetic nervous system
stimulates effectors
fight or flight response
parasympathetic nervous system
inhibits effectors
conserving nearby and replenishing the body’s reserves
why is the heart myogenic?
contraction initiated from inside rather than by nervous impulses
sequence of steps that control heart rate
1) wave of electrical excitation spreads from SAN across atria causing them to contract
2) atrioventricular septum prevents wave crossing into ventricles
3) wave of excitation enters AVN
4) AVN conveys wave between ventricles through purkyne tissue which makes up the bundle of His
5) wave conducted down to base of ventricles where it’s released from the purkyne tissue causing ventricles to contract
what part of the brain controls changes to heart rate?
medulla oblongata
centre that increases heart rate- linked to SAN by sympathetic nervous system
centre that decreases heart rate- linked to SAN by parasympathetic nervous system
chemoreceptors
found in aorta and carotid artery
detect changes in blood pH
process of blood pH control
1) carbon dioxide conc. increases meaning blood pH decreases
2) detected by chemoreceptors which increases impulses to the centre in the medulla oblongata which increases heart rate
3) increases frequency of impulses via sympathetic nervous system to the SAN which will increase heart rate
4) increased blood flow removes more carbon dioxide so blood pH rises to normal
baroreceptors
detect blood pressure
in aorta and carotid arteries
process when blood pressure is high
barocreceptors send more impulses to centre of medulla oblongata that decrease heart rate
sends impulses via parasympathetic nervous system to SAN decreasing the heart beats
two types of coordination in animals
nervous system- transported by neurones, fast, short-lived
hormonal system- transported by blood, slow, long-lasting