5.1.5 animal responses Flashcards
Organisation of mammalian nervous system
split into two main structural systems
The central nervous system and the peripheral nervous system
what is the central nervous system made up of?
the brain and spinal cord
what is the peripheral nervous system made up of?
the neurons that connect the CNS to the rest of the body
What is the peripheral nervous system further organised to
the somatic nervous system
the autonomic nervous system
what does the somatic nervous system control
conscious activities
eg. running
what does the autonomic nervous system control
unconscious activities
eg. digestion
what are the 2 divisions that the autonomic nervous system is spilt into
the sympathetic nervous system
the parasympathetic nervous system
what does the sympathetic nervous system do?
gets the body ready for action, it’s the fight or flight system
What do sympathetic neurones release?
the neurotransmitter noradrenaline
What does the parasympathetic nervous system do?
calms the body down, rest and digest
What do parasympathetic neurones release
the neurotransmitter acetylcholine
what are the 5 structures of the human brain?
cerebrum cerebellum medulla oblongata pituitary gland hypothalamus
Human brain structure - cerebrum (where it is)
largest part of the brain, divided into two halves called cerebral hemispheres
has a thin outer layer, the cerebral cortex, which is highly folded
Human brain structure - cerebellum (where it is)
underneath the cerebrum
also has a folded cortex
Human brain structure - medulla oblongata (where it is)
at the base of the brain, at the top of the spinal cord
Human brain structure - pituitary gland (where it is)
found beneath the hympthalamus
Human brain structure - hypothalamus (where it is)
found just beneath the middle part of the brain
Human brain structure - cerebrum (what it does)
involved in vision, hearing, talking and thinking
Human brain structure - cerebellum (what it does)
important for muscle coordination, posture, and coordination of balance
Human brain structure - medulla oblongata (what it does)
automatically controls breathing rate and heart rate
Human brain structure - pituitary gland (what it does)
controlled by the hypothalamus
it releases hormones and stimulates other glands to release their hormones
Human brain structure - hypothalamus (what it does)
automatically maintains body temperature at the normal level
the hypothalamus produces hormones that control the pituitary gland
outline the knee jerk reflex and its survival benefits
work quickly to straighten your leg if the body detects your quadriceps suddenly stretched
helps maintain posture and balance
- stretch receptors in the quadricep detect the muscle is being stretched
- a nerve impulse is passed along a sensory neuron which communicates directly with a motor neuron in the spinal cord
- the motor neuron carries the nerve impulse to the effector (the quadriceps muscle) causing to to contract so the lower leg moves forward quickly
outline the blinking reflex and its survival benefits
when your body detects something that could damage your eye, you automatically blink (quickly close your eyelid to protect your eye then open it again)
- sensory nerve endings in the cornea (front part of the eye) are stimulated by touch
- a nerve impulse is sent along the sensory neuron to a relay neurone in the CNS
- the impulse is the passed from the relay neuron to motor neurons
- the motor neurons send impulses to the effectors ( the orbicularis oculi) muscles that move your eyelids
- these muscles contract cause your eyelids to close quickly and prevent your eye from being damaged
what coordinates muscular movement?
the central nervous system
- CNS receives sensory information and decides what kind of response is needed
- is the response is movement the CNS sends signals along neurons to tell skeletal muscles to contract
structure of skeletal muscles
made up of large bundles of MUSCLE FIBRES
- cell membrane of muscle fibres = SARCOLEMMA
bits of the sarcolemma fold inwards across the muscle fibre and stick into the SARCOPLASM (muscle’s cells cytoplasm). these folds are TRANSVERSE (T) TUBULES.
- T tubules help spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre
a network of internal membranes called the SARCOPLASMIC RETICULUM runs through the sarcoplasm.
- this stores and release CALCIUM IONS that are needed for muscle contraction
have lots of mitochondria to provide ATP needed for muscle contraction
multinucleate
have long cylindrical organelles called MYOFIBRILS
- made up of proteins and highly specialised for contraction
structure of skeletal muscles - myofibrils
contain thick myosin filaments and thin actin filaments
- when they move past each other the muscle contracts
under a microscope see a pattern of:
- dark bands; thick myosin filaments and some overlapping actin = A-BANDS
- light bands; thin actin filaments only = I-BANDS
a myofibril is made up of many short units called SARCOMERES
the end of each sarcomere are marked with a Z-LINE
in the middle of each sarcomere is a M-LINE (the middle of the myosin filament)
around the m-line is the H-ZONE (only contains myosin filaments)
What theory explains muscle contraction?
the sliding filament theory
myosin and actin filaments slide over each other one another to make sarcomeres contract
(myofilaments themselves dont contract)
the simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract
sarcomeres return to their original length as the muscle relaxes
Muscle contraction - why can myosin filaments move back and forth
myosin filaments have globular heads that are hinged, so can move back and forth
each myosin head has an binding site for actin and a binding site for ATP
actin filaments have binding sites for myosin heads - ACTIN-MYOSIN BINDING SITES
muscle contraction - how are muscles at rest?
the proteins - TROPOMYOSIN and TROPONIN are found between actin filaments (they are attached to each other)
in a resting muscle the ACTIN-MYOSIN BINDING SITE is BLOCKED by TROPOMYOSIN (which is held in place by troponin)
so the myofilaments cannot slide past each other because myosin heads cannot bind to the actin-myosin binding site on the actin filaments
what triggers muscle contraction?
an action potential
muscle contraction - what does the action potential trigger?
triggers an influx of calcium ions
- action potential from motor neuron stimulates a muscle cell, it POLARISES the SARCOLEMMA
- depolarisation spreads down T-TUBULES to the SARCOPLASMIC RETICULUM - this causes the SARCOPLASMIC RETICULUM to RELEASE stored CALCIUM IONS into sarcoplasm
- CALCIUM IONS binds to TROPONIN causing it to CHANGE SHAPE. This pulls the attached TROPOMYOSIN out of the binding site on actin filament
- EXPOSING THE BINDING SITE, myosin head to bind
- the bond formed when a myosin head binds to an actin filament is called an ACTIN-MYOSIN CROSS BRIDGE
muscle contraction - what moves the myosin head (once it is in binding site)
ATP provides energy needed to move the myosin head
- CALCIUM IONS also activate the enzyme ATPase - which breaks down ATP –> Pi + ADP to provide energy needed for muscle contraction
- the energy released from ATP moves the myosin head - which pulls the actin filament along (in a rowing action)
muscle contraction - what breaks the actin-myosin cross bridge
ATP
- ATP provided energy to break the cross-bridge, so the myosin head detaches from the actin filament AFTER it moved
- the myosin head attaches to a different bind site further along the actin filament
- a new actin-myosin cross-bridge is formed and the cycle is repeated (attach, move, detach, reattach..) as long as there is calcium ions bound to troponin
What part of muscle contraction actually causes the muscles to contract?
many cross-bridges form and break very rapidly
pulling the actin filament along - which shortens the sarcomere, causing the muscle to contract
muscle contraction - what happens when excitation stops?
- when muscle stops being stimulated, calcium ions leave their binding sites on troponin
- move back into sarcoplasmic reticulum via active transport (needs ATP) - the troponin molecules return to their original shape. pulling the tropomyosin molecules with them
- this means the actin-myosin binding site is blocked again - muscles are not contracted as no myosin heads are attached to actin filaments (no actin-myosin cross-bridges)
- the actin filaments slide back to their relaxed position, this lengthens the sarcomere
What provides energy for muscle contraction?
ATP and CP
- aerobic respiration - most ATP via oxidative phosphorylation in mitochondria (needs O2)
- anaerobic respiration - ATP made via glycolysis (pyruvate —> lactate via lactate fermentation)
- lactate can build up quickly in muscles and cause muscle fatigue - ATP-Creatine Phosphate (CP) system
- ATP made by phosphorylating ADP - adding a phosphate group taken from creatine phosphate
- CP is stored inside cells and the ATP-CP system generates ATP very quickly
- anaerobic and alactic (doesn’t form any lactate)
what are neuromuscular jucnctions?
synapses between motor neurones and muscles
how do neuromuscular junctions work?
- use the neurotransmitter ACETYLCHOLINE (ACh) - binds to receptors on nicotinic cholinergic receptors
- release neurotransmitter which triggers depolarisation in the postsynaptic cell
- depolarisation of a muscle always causes it to contract if it reaches the threshold level
- Acetylcholinesterase (AChE) stored in clefts in postsynaptic membrane is release to break down ACh after use
How could muscle contraction be stopped and there be fatal?
a chemical (drug) may block the release of the neurotransmitter or affect the way it binds to the receptors on the postsynaptic membrane. - this may prevent the action potential from being passed on to the muscle, so the muscle won't contract
this can be fatal if it affects the muscles involved in breathing (diaphragm and intercostal muscles) if they cant contract ventilation cant take place and the organism can respire aerobically
what are the three types of muscle
skeletal
involuntray
cardiac
involuntary muscles - structure and function
- controlled unconsciously
- called smooth muscle because it doesn’t have the stripped appearance of voluntary muscle
- found in walls of hollow internal organs (gut, blood vessels)
- each muscle fibre has one nucleus, fibres are spindle-shaped with pointed ends, 0.2mm long
- contract slowly and don’t fatigue
cardiac muscle - structure and function
- contracts on its own - myogenic (rate controlled by the autonomic nervous system)
- found in walls of the heart
- made of muscle fibres connected by intercalated discs, which have low electrical resistance so nerve impulses pass easily between cells
- the muscle fibres are branched to allow nerve impulses to spread quickly through the whole muscle
- each muscle fibre has one nucleus, fibres shapes like cylinders, 0.1mm long
- can see some cross-striations but the striped pattern isn’t as stong as voluntary muscle
- the fibre muscles contract rhythmically and don’t fatigue
skeletal muscle - structure and function
also called voluntary muscle
- contraction controlled consciously
- made up of many muscle fibres that have many nuclei, and can be many cm long
- can see regular cross-striations under a microscope
- some muscle fibres contract very quickly - used for speed and strength but fatigue quickly
- some muscle fibres contract slowly and fatigue slowly - used for endurance and posture
what is the fight or flight response?
when an organism is threatened it prepares the body for action
How is the fight or flight response initiated ?
nerve impulses from the sensory neurons arrive at the hypothalamus
- activating both the hormonal system and the sympathetic nervous system
fight or flight response - hormonal system
hypothalamus stimulates the pituitary to release a hormone called ACTH
this causes the cortex of the adrenal gland to release steroidal hormones
fight or flight response - hormonal system response
steroid hormones - cortisol and aldosterone
- long term and short term response to stress
- stimulates the breakdown of proteins and fats into glucose —> this increases the amount of energy available so the brain and muscles can respond to the situation
- increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys
- suppressing the immune system
fight or flight response - sympathetic nervous system
sympathetic nervous system is activated by the hypothalamus
triggering the release adrenaline from the medulla of the adrenal medulla
fight or flight response - sympathetic nervous system response
adrenal medulla releases adrenaline
- heart rate increased —> blood pumped around body faster
- muscles around the bronchioles relax —> so breathing in deeper
- glycogen is converted to glucose —> so more glucose available to respire
- muscles in the arterioles supplying the skin and gut constrict, and muscles in the arterioles supplying heart, lungs and skeletal muscles dilate —> so blood is diverted
- erector pili muscles in the skin contract —> this makes hairs stand on end so the animal looks bigger
control of heart rate involves…..
both hormonal and neuronal systems
control of heart rate - hormonal system
releasing adrenaline
adrenaline binds to specific receptors in the heart
this causes cardiac muscles to contract more frequently and with more force
so heart rate increases and the heart pumps more blood
control of heart rate - nervous system
- the sino-atrial node generates electrical impulses that cause cardiac muscles to contract
- the rate at which the SAN fires is unconsciously controlled by a part of the brain called the medulla
- animals need to alter their heart rate to respond to internal stimuli
- stimuli are detected by pressure and chemical receptors
- electrical impulses from receptors are sent to the medulla along sensory neurones
- the medulla processes the info. and sends impulses to the SNA along motor neurones
control of heart rate - nervous system, receptors
pressure receptors - baroreceptors
- –> in the aorta and vena cava
- —> stimulated by high and low blood pressure
chemical receptors - chemoreceptors
- –> in the aorta and carotid artery
- –> monitor the oxygen level in the blood and also carbon dioxide and pH
control of heart rate - high blood pressure
receptor = baroreceptors
neurone = impulses sent to the medulla, which sends impulses along the vagus nerve
neurotransmitter = secretes acetylcholine
effector = cardiac muscles
response = heart rate slows down to reduce blood pressure back to normal
control of heart rate - low blood pressure
receptor = baroreceptors
neurone = impulses sent to the medulla, which sends impulses along the accelerator nerve
neurotransmitter = secretes noradrenaline
effector = cardiac muscles
response = heart rate speeds up to increase blood pressure back to normal
control of heart rate - high blood O2, low CO2 or high pH levels
receptor = chemoreceptors
neurone = impulses sent to the medulla, which sends impulses along the vagus nerve
neurotransmitter = secretes acetylcholine
effector = cardiac muscles
response = heart rate decreases to return O2, CO2 and pH levels back to normal
control of heart rate - low blood O2, high CO2 or low pH levels
receptor = chemoreceptors
neurone = impulses sent to the medulla, which sends impulses along the acceletator nerve
neurotransmitter = secretes noradrenline
effector = cardiac muscles
response = heart rate increases to return O2, CO2 and pH levels back to normal
action of hormones - 1st messengers
a hormone is a first messenger because it carries the chemical message the first part of the way, from the endocrine gland to the receptor on the target cells
when a hormone binds to its receptor it activates an enzyme in the cell membrane
action of hormones - 2nd messengers
when a hormone binds to its receptor it activates an enzyme in the cell membrane
the enzyme catalyses the reproduction of a molecule inside the cell called a signalling molecule
- this molecule signals to other parts of the cell to change how the cell works
the signalling molecule is called a second messenger because it carries the chemical message the second part of the way
—> from the receptor to other parts of the cell
action of hormones - 2nd messengers activate a cascade
eg. cAMP
the hormone adrenaline is a first messenger
it binds to specific receptors in the cell membranes of many cells
when adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase
activated adenylyl cyclase catalyses the production of a second messenger called cyclic AMP
cAMP activates a cascade (chain of reaction)
- eg. makes more glucose available to the cell by catalysing the breakdown of glycogen into glucose
