Module 5.5 Flashcards
Plant and animal responses
divisions of the nervous system
central nervous system
peripheral nervous system
divisions of the central nervous system
brain spinal cord
division of the peripheral nervous system
sensory system
motor system
divisions of the motor system
somatic nervous system
autonomic nervous system
role of the peripheral nervous system
ensures rapid communication between the sensory receptors the CNS and the effectors
what is the PNS composed of
sensory and motor neurones
what is the brain composed of
mainly relay neurones with multiple connections to allow complex neural pathways
mostly non myelinated (grey matter)
what is the spinal cord composed of
non-myelinated neurones make up the central grey matter
myelinated neurones make up an outer region of white matter to carry action potentials up and down the spinal cord for rapid communication over longer distances
what is the sensory nervous system composed of
sensory neurones conduct action potential from the sensory receptors to the CNS
what is the motor nervous system composed of
motor neurones to conduct action potentials from the CNS to effectors
what is the somatic nervous system composed of
motor neurones that conduct action potentials to effectors under conscious control
mostly myelinated and one single neurone connecting CNS to effector
what is the autonomic nervous system composed of
motor neurones that conduct action potentials from the CNS to effectors not under voluntary control
unmyelinated and at least 2 neurones involved
divisions of the autonomic nervous system
sympathetic nervous system
parasympathetic nervous system
role of the sympathetic nervous system
prepares the body for activity
role of the parasympathetic nervous system
conserves energy
what are the 4 main parts of the brain
cerebrum
cerebellum
hypothalamus and pituitary complex
medulla oblongata
role of the cerebrum
controls higher brain functioning
conscious thought and actions
emotional responses
intelligence, reasoning, judgement and decisions making
factual memory
function of the cerebellum
coordinates fine control of muscular movements
maintaining body position and balance
judging position of objects and limbs
tensioning muscles
coordination contraction and relaxation of antagonistic muscles
function of the hypothalamus
controls homeostatic mechanisms
temperature regulation
osmoregulation
manufactures hormones
function of the pituitary gland
posterior lobe linked to hypothalamus by neurosecretory cells
hormones manufactured in hypothalamus released into blood by pituitary gland
anterior lobe produces and releases its own hormones in response to releasing factors from the hypothalamus
function of the medulla oblongata
controls non-skeletal muscle
regulates many vital processes
heart rate
circulation and blood pressure
rate and depth of breathing
what is a reflex action
a response to changes in the environment that do not involve any processing in the brain to coordinate the movement
the pathway is as short as possible so the reflex is rapid
most consist of 3 neurones
examples of reflexes
blinking
corneal reflex
optical reflex
knee jerk reflex
what type of reflex is the knee jerk reflex
spinal reflex
passes through the spinal cord rather than through the brain
how does the knee jerk reflex work
when muscles at the front of the thigh are stretched specialised stretch receptors called muscle spindles detect the increase in length of the muscle
if the stretching is unexpected a reflex action causes the contraction of the same muscle
role of the knee jerk reflex
enables balance e.g. if standing and body is bending or starting to lean forward the muscle contraction straightens the knee or brings the body back above the legs
why is the knee jerk reflex unusual
nervous pathway only consists of 2 neurones
a sensory and motor neurone
why are reflex actions needed
survival value
may be used to get out of danger avoid damage to a part of the body or to maintain balance
what is the fight or flight response
stimulated by the detection of a threat to survival
leads to a range of physiological changes to prepare the animal for activity
activity may be running away or a direct challenge to the perceived threat
examples of physiological changes associated with the fight or flight response
pupils dilate
HR and BP increase
arterioles to digestive system constricted while those to the muscles and liver are dilated
blood glucose levels increase
metabolic rate increases
endorphins (natural pain killers) released in the brain
examples of receptors to detect threats
external:
eyes, ears, nose
Internal:
decrease in BP, pain
how is the fight or flight response coordinated
input from receptors feed into sensory centres in the cerebrum
signal passed to association centres
if a threat is identified the cerebrum stimulates the hypothalamus which stimulates the nervous and endocrine response
what is the nervous system response in fight or flight
sympathetic nervous system activated
adrenal medulla activated to release adrenaline into the blood stream
glands and smooth muscles activated e.g. HR and BP
what is the endocrine response in fight or flight
hypothalamus secretes releasing hormones to stimulate the pituitary gland
pituitary gland secretes hormones which stimulate the adrenal cortex and thyroid
what releasing hormones does the hypothalamus produce in fight or flight
CRH
TRH
what hormones does the pituitary gland release in fight or flight
ACTH
TSH
what does the adrenal cortex release in fight or flight
corticoid hormones
e.g. cortisol
increases glycogen to glucose conversion
what does the thyroid gland secrete in the fight or flight response
thyroxine
increases metabolic rate
mechanism of adrenaline action
adrenaline (first messenger) binds to adrenaline receptor on plasma membrane
receptor is associated with G protein
G protein stimulated to activate adenyl cyclase
adenyl cyclase converts ATP to cyclic AMP (second messenger)
cAMP causes effect inside the cell
why does heart rate need to be controlled
heart tissue is myogenic so would beat on its own but atrial muscle has a higher myogenic rate than the ventricular muscle
chamber must contract in a coordinate way
where is heart rate controlled
cardiovascular centre in the medulla oblongata
how is heart rate increased
action potentials sent down the accelerans nerve (sympathetic nerve) cause the release of noradrenaline at the SAN
heart rate increases
how is heart rate decreased
action potential sent down the vagus nerve (parasympathetic nerve)
acetylcholine release at the SAN
heart rate decreases
what receptors input to the cardiovascular centre
stretch receptors in muscles
chemoreceptors in the carotid artery
stretch receptors in the walls of the carotid sinus
co2 concentration in the blood
role of muscle stretch receptors in heart rate
if a lot of muscle movement is detected cardiovascular centre is informed extra oxygen may be needed soon
increased HR
role of chemoreceptors in heart rate
detect reduction of pH due to increase of CO2 in the blood
HR increases
role of carotid sinus stretch receptors in heart rate
monitor blood pressure
if BP is too high HR will decrease
what are the 3 type of muscle
involuntary (smooth) muscle
cardiac muscle
skeletal muscle
structure of involuntary muscle
individual cells tapered at both ends
cells contain a nucleus and bundles of action and myosin
function of smooth muscle
unvoluntary muscle contraction
e.g. blood vessels intestine
does not tire quickly
structure of cardiac muscle
individual cells form long fibres which branch to form cross bridges
cells joined by intercalated discs
function of cardiac muscle
makes up the muscular part of the heart
cross bridges ensure electrical stimulation spreads evenly over the walls of the chambers
intercalated discs produce gap junctions that allow free diffusion of ions between the cells
action potentials pass quickly and easily between the fibres
structure of skeletal muscle
cells form fibres
each fibre is multinucleate and surrounded by a membrane called the sarcolemma
divisions of skeletal muscle
muscle fibre
myofibril
sarcomere
what is a neuromuscular junction
junction between the nervous system and the muscle
similar to a synapse
how is muscle contraction stimulate
action potentials at the end of an axon open calcium channels allowing calcium ions into the end of the axon
acetylcholine vesicles fuse with the end membrane the diffuse across the gap to fuse with receptors in the sarcolemma
this opens sodium ion channels
sarcolemma depolarise
wave of depolarisation spreads along the sarcolemma into the muscle fibre
elements of myofibrils
I band
A band
Z line
what is the I band
actin filaments
tropomyosin wound around
troponin attached to tropomyosin
what is the A band
myosin filaments with mobile protruding heads
how is muscle contraction started
action potential passes along the sarcolemma and down the transverse tubule into the muscle fibres
action potential is carried to the sarcoplasmic reticulum which stores calcium ions
calcium ions released into the sarcoplasm
what happens to the actin in muscle contraction
calcium ions bind to the troponin altering its shape
this pulls the tropomyosin aside
binding sites on the actin exposed
what happens to myosin in muscle contraction
myosin heads bind to the actin forming cross bridges between the filaments
myosin heads move pulling the actin filament past the myosin filaments
myosin heads detatch and can bind again further up the actin
role of ATP in muscle contraction
part of the myosin head can hydrolyse ATP to ADP and Pi to release energy
myosin head moving to slide actin requires energy ADP and Pi are released
ATP attaches again to break cross bridge
myosin head goes to original position as ATP is hydrolysed
what is the power stroke
movement of the myosin head to slide the actin filament over itself
how is ATP supply maintained in muscles
ATP from aerobic respiration
ATP for anaerobic respiration
creatine phosphate in the sarcoplasm acts as a reserve store of phosphate groups which can be transferred to ADP molecules to create ATP using creatin phosphotransferase
what are the plant responses to herbivory
chemical defences and folding in response to touch
what chemical defences are used in response to herbivory
alkaloids (feeding deterrent as they taste bitter)
pheromones (can affect the behaviour or physiology of another)
what are tropisms
directional growth responses of plants
types of tropisms
phototropism (light)
geotropism (gravity)
chemotropism (chemicals)
thigmotropism (touch)
what is a positive tropic response
if a plant responds towards a stimulus e.g. growing towards light
what is a negative tropic response
if a plant responds away from a stimulus e.g. shoots growing away from the force of gravity
what is a nastic response
a non-directional response to external stimuli
what plant hormone play a role in leaf loss
cytokinins delay leaf senescence/ageing
auxins inhibit leaf abscission/loss
what plant hormone plays a role is seed germination
gibberellins promote germination
abscisic acid inhibits seed germination
what plant hormone plays a role in stomatal closure
abscisic acid causes stomatal closure when the plant is stressed by low water availability
role of cytokinins
delays leaf senescence/ageing
overcomes apical dominance
role of abscisic acid
inhibits seed germination and growth
causes stomatal closure when the plant is stressed by low water availability
role of auxins
inhibits leaf abscission/fall
inhibits growth of side shoots
role of gibberellins
promotes seed germination
role of ethene
promotes fruit ripening
what is apical dominance
inhibition of lateral bud growth further down the shoot by chemical by the apical bud at the tip of the plant shoot
effect of auxin concentration on apical dominance
normal auxin level in lateral buds inhibits growth
low auxin levels promote growth in lateral buds
example of experimental evidence for the role of auxins
when auxin paste is applied to the cut end of a shoot the lateral buds did not grow
when auxin transport inhibitor is applied below the apex of the shoot the lateral buds grow
effect of gibberellin concentration on stem elongation
stimulates cells division and elongation
how do gibberellins promote seed germination
when seeds absorb water the embryo releases gibberellins which enables the production of amylase to break starch into glucose providing the substrate for respiration so the embryo can grow
commercial uses of plant hormones
control of ripening
rooting powders
hormonal weed killers
how is fruit ripening controlled
ethene can be sprayed on plants to speed up ripening and make all fruits ripen at the same time
fruit can be stored in low temperatures with little oxygen to prevent ethene synthesis to prevent fruit ripening so it can be stored for longer
what is rooting powder
contains auxins to encourage root growth from a cutting
what are hormonal herbicides
auxins
promote shoot growth so much that the stem cannot support itself, buckles and dies
