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biology module 5.5 - animal responses, Unknown-1 - Coggle Diagram
biology module 5.5 - animal responses
brain and the nervous system
central nervous system : brain and spinal chord
cerebrum = control of voluntary action - learning, memory, personality
outer layer of cerebrum = cerebral cortex
2 hemispheres of cerebrum (left and right), connected by corpus callosum
cerebellum = control unconscious actions - posture, balance
PONS connects the cerebrum and cerebellum together
medulla oblongata = control non-skeletal cardiac and smooth muscle (heart rate, blood pressure and breathing) , autonomic control
hypothalamus = control of homeostatic measures
pituitary gland =
anterior (front), releases own hormones
protector (back) = release hormones from neurosecrertory cells, link hypothalamus
peripheral nervous system : sensory system and motor system
motor system : somatic and autonomic
autonomic : sympathetic and parasympathetic
sympathetic = increase activity, prepare body for activity
uses noradrenaline
increase heart rate
parasympathetic = decrease activity, conserve energy
uses acetylcholine
decrease heart rate
somatic = control of voluntary action, under conscious control
neurones are mostly myelinated
autonomic = control of involuntary action, under unconscious control
neurones are mostly non-myelinated
reflexes
reflex = a fast, involuntary action in response to a stimulus - response is short lived
reflex pathway : stimulus detected by receptor
action potential travels along sensory neurone
then travels along a relay neoruone
then a motor neurone
reaches an effector (muscle or gland)
blinking reflex
cornea is irritated (detected by receptor)
impulse travels along sensory neurone, transmit impulse to the PONS
motor neurone sends impulses so eyelid muscles
eyelid muscles contract to protect the eye
knee jerk reflex
tap the patella tendon
receptors detect the stretch of patellar tendons (flexor)
impulse send from sensory neurone to the spinal chord, impulse passed onto motor neurone
causes the contraction of extensor = knee jerk
spinal reflex = nervous pathway passes through spinal chord rather than the brain
bending legs when walking/running : action potentials sent to hamstring muscles causing them to contract, inhibitory action potentials prevent the contraction of quadricep muscles (antagonistic)
fight or flight
psychological responses during a fight or flight situation = pupils dilate, HR and BP increase, metabolic rate increases
external receptors (eyes, ears) detect threat
internal receptors (change in BP, pain) detect threat
how does our body co-ordinate a response for flight or fight?
cerebrum recognise threat
hypothalamus increase activity in the sympathetic nervous system
= increases the activity of effectors
= stimulate the production of adrenaline, released into bloodstream
anterior pituitary gland releases 2 hormones :
TSH - thyroid gland to make more thyroxine (increase metabolic rate)
ACTH - adrenal gland to release glucocorticoids (regulate metabolism of carbs, results n more glucose for respiration)
action of adrenaline
adrenaline (first messenger) cannot pass through the lipid layer of the cell membrane - binds to a receptor. This binding activates a G protein. This G protein then activates an effector molecule (adenyl cyclase). An inactive ATP molecule is converted into cAMP (second messenger) which will activate enzymes and molecules within the cell
muscle structure
smooth muscle (autonomic), cardiac muscle (myogenic) and skeletal muscle (somatic)
myofibrils are made up of repeating sarcomeres
sarcomeres are made of actin and myosin protein filaments
actin structure :
thin filament
2 strands of actin sub-monomers
actin-myosin binding sites (blocked by tropomyosin)
troponin and tropomyosin are bound together, troponin holds tropoymyosin in place
myosin structure :
thicker filament
long intertwined rod with bulb heads
have hinged globular heads
has a binding site on each head
tail = myosin neck
head = can hydrolyse ATP (ATPase)
plasma membrane (sarcolemma) folded inwards = T tubule
able to spread elctrical impulse throughout whole msucle fibre, allow for simultaneous contraction
myofibril structure :
I band = lIght zone where actin and myosin do not overlap, there is only actin
A band = where myosin is(part is over lapped with actin)
H zone = dark zone, not as dark, only myosin
Z lines = mark end of sarcomere
during muscle contraction
Z lines move closer together
the H zone becomes smaller
I band becomes shorter
process of an action potential arriving at a neuromuscular junction :
action potential arrives and causes calcium channels to open (calcium flood into cell)
calcium stimulates vesicles containing acetycholine to fuse with the presynaptic membrane
acetycholine diffuses across the cleft and binds to receptors on the sarcolemma
sodium channels open and sodium floods into muscle cell
sarcolemma depolarises and if threshold value is reached, an action potential is generated
this action potential travels down the t tubule into the muscle cell to the sarcoplasmic reticulum
sarcoplasmic reticulum releases stored calcium into the cytoplasm
muscle contraction
during a muscle contraction :
the I band (light) become shorter
Z lines move closer together, sarcomere shortens
H zone becomes shorter
A band (dark) remains the same length, just overlaps more
process of muscle going from relaxed to contracted state :
tropomyosin blocks myosin from binding with actin
a nerve impulse stimulates the release of calcium ions (action potential initiated by neurotransmitter causes the depolarisation of sarcolemma, voltage gated calcium channels open)
calcium ions bind to troponin, changing the shape of tropomyosin
exposes the actin myosin binding site, myosin head can now bind to actin = form a cross bridge
myosin filament flexes and pulls actin forwards = power stroke
ADP released from myosin head
ATP can bind to myosin head, becomes hydrolysed into ADP, Pi and energy
this energy is required to allow the release of myosin head from actin
muscles relax again when the nerve is no longer stimulated, calcium channels close and tropomyosin returns to block the actin-myosin binding sites
control of heart rate
controlled by the autonomic nervous system
increase heart rate = medulla oblongata sends action potential along a sympathetic nerve (accelerant nerve) causing the release of noradrenaline at the SAN
decrease heart rate = medulla oblongata sends action potential along a parasympathetic nerve (vagus nerve) causing the release of acetylcholine
