5.1.5 Plant and animal responses Flashcards
CNS made up of and role
central nervous system = brain + spinal cord
coordinating response
brain mostly made out of
non-myelinated relay neurones (grey matter)
spinal cord mostly made out of
myelinated (white) and non-myelinated (grey) relay neurones
PNS made out of and role
sensory and motor neurones
connects receptors to CNS and to effector to bring about response
sensory nervous system structure
connects receptor to CNS
sensory neurones enter spinal cord at dorsal root (where cell body is also)
short axon connects to relay neurones in CNS
motor neurones structure and role
connects CNS and effectors
split into autonomic and somatic nervous systems
somatic nervous system features and role
motor neurones under voluntary control
e.g. controlling skeletal muscles
mostly myelinated neurones (fast)
single motor neurones connect CNS and effectors
autonomic nervous system features and role
motor neurones under involuntary control
mostly non-myelinated neurones (slower)
at least 2 neurones between CNS and effector
examples of actions controlled by autonomic nervous system
controlling glands cardiac muscle smooth muscles in gut eyes blood vessels airways
ganglia obvious features
swelling
sympathetic vs parasympathetic nervous systems in general
sympathetic more active in times of stress whereas parasympathetic in times of rest
how autonomic nervous system is split
sympathetic and parasympathetic
antagonistic to each other
balance depending on internal conditions and stress to bring about appropriate response
sympathetic nervous system features
short preganglionic neurone ganglia near CNS many nerves leave CNS noradrenaline is neurotransmitter active in fight/flight or stress
parasympathetic nervous system features
long preganglionic neurone ganglia near organs few nerves leave CNS then split up to go to effectors acetylcholine is neurotransmitter active in calm
human brain 4 main parts
cerebrum
cerebellum
hypothalamus + pituitary complex
medulla oblongata
cerebrum function
organises most higher thought process e.g.
conscious thought/actions
memory
emotions
intelligence, reasoning, judgement, decision making
cerebellum function
coordinates balance and fine movement e.g. tensioning muscles for playing music, judging positioning of objects while moving
complex nervous pathways become stronger with practice (becomes “second nature”)
hypothalamus structure and role
organises homeostatic responses and control physiological processes
e.g. temperature regulation and osmoregulation
contains own receptors, osmoreceptors, thermoreceptors
regulates feeding and sleeping patterns
medulla oblongata function
coordinates many autonomic responses controls cardiac muscles and smooth muscles by sending action potentials through autonomic nervous system regulates many vital processes e.g. cardiac centre (regulates heart rate) vasomotor centre (regulates circulation + blood pressure) respiratory centre (controls rate + depth of breathing) centres receive sensory information and coordinate vital functions through negative feedback
cerebrum structure
2 cerebral hemispheres connected via major tracts of neurones called corpus callosum
outermost layer consists of thin layer of nerve cell bodies called cerebral cortex
cerebral cortex structure
sensory areas
association areas
motor areas
how cerebrum and cerebellum connected
the pons
pituitary gland structure and role
posterior lobe linked to hypothalamus by specialised neurosecretory glands
secretes hormones (produced in hypothalamus) into blood
anterior lobe produces own hormones (for physiological processes e.g. stress), released in response to releasing factors produced by hypothalamus
sensory area function
receive action potentials from sensory receptors, size related to sensitivity of area to inputs received
association area function
compares and interprets sensory inputs with previous experiences to judge appropriate response
motor area function
send action potentials to effectors, size related to complexity of movements needed in parts of body, left side of brain controls effectors on right side and vice versa
knee jerk reflex definition
reflex action that straightens leg when tendon below kneecap is tapped
reflex action definition
response that doesn’t involve any processing by the brain
why reflex occur
need to be quick for survival
e.g. get out of danger, prevent damage, maintain balance
nervous pathway of reflex actions
sensory neurone -> relay neurone -> motor neurone
cranial reflex definition
reflex where nervous pathway passes through part of the brain but doesn’t involve any thought processes
reflex arc definition
receptor and effector are in the same place
blinking stimulus examples
foreign object touching eye (corneal reflex)
sudden bright light (optical reflex)
loud sounds
sudden movements close to eye
optical reflex
protects light-sensitive cells of retina from damage
stimulus detected by retina
reflex mediated by optical centre in cerebral cortex
slower than corneal reflex
corneal reflex
mediated by sensory neurone from cornea, entering pons
synapse connects sensory to relay neurone, carrying action potential to motor neurone
motor neurone passes back out of brain to facial muscles, causing eyelids to blink
short and direct pathway so very rapid
why corneal reflex can be overridden
sensory neurone involved in corneal reflex also passes action potentials to myelinated neurones in pons
these neurones carry a.p. to sensory area in cerebral cortex
informs higher centres of brain that stimulus has occurred
allows reflex to be overriden by conscious control
myelinated neurones carry a.p. faster than non-myelinated neurones
how knee jerk reflex works
muscle at bottom of thigh contracts to straighten leg
muscle spindle (specialised stretch receptors) detect increase in length of muscle
if unexpected, reflex causes contraction of same muscle to remain balanced
why knee jerk reflex is strange
nervous pathway only involves 2 neurones
sensory neurone -> motor neurone
much quicker as 1 less synapse
spinal reflex definition
nervous pathway passes through spinal cord rather than through brain
why brain cannot inhibit knee jerk reflex
no relay neurone to carry a.p. to brain
sensory neurone stimulates motor neurone directly
insufficient delay to enable inhibition by brain sending inhibitory action potentials to synapse before motor neurone is stimulated
fight or flight response physiological changes
+heart rate and blood pressure (increased blood flow, more O2 and glucose to respiring cells for more respiration)
+breathing rate and depth (faster rate of gas exchange = more O2 in blood = more respiration)
arterioles to skin+digestive system vasoconstrict (less blood to skin and DS, not needed in response)
arterioles to muscles vasodilate (more blood for more respiration, needed in response)
pupils dilate (more light into retina to see better)
+glycogenolysis (more glucose released into blood from liver, more respiration)
+metabolic rate
erector muscles in skin contract (make hairs stand up to look bigger, potentially more intimidating, prevent conflict)
role of brain in fight or flight response
receptor sense threatening stimulus
a.p. sent to sensory centres in cerebrum
then association centres to coordinate response
cerebrum stimulated hypothalamus in response to threat
hypothalamus stimulates sympathetic nervous system + anterior pituitary gland
role of sympathetic nervous system in fight or flight response
increases activity of effectors via nervous impulses (more rapid response)
stimulates adrenal medulla to release adrenaline (which brings about responses in effectors) for longer response
