ANIMAL RESPONSES

What two systems is the nervous system split into

- The central nervous system: made up of the brain and the spinal cord

- The peripheral nervous system: made up of the that connect the CNS to the rest of the body\####What are the two functional systems of the peripheral nervous system?

- The somatic nervous system: controls conscious activities, eg. running and playing video games

- The autonomic nervous system: controls unconscious activities, eg. digestion\####What are the two divisions of the autonomic nervous system?

- The sympathetic nervous system: gets the body ready for action. It's the 'fight or flight' system.

- The parasympathetic nervous system calms the body down.\####What do sympathetic nerves do?

raise heart rate by secreting noradrenaline\####What do parasympathetic nerves do?

- It's divided into two parts called cerebral hemispheres

- The cerebrum has a thin outer layer called the cerebral cortex, which is highly folded

- The cerebrum is involved in hearing, vision, learning and thinking\####Where is the hypothalamus found in the brain and what is it's function?

- The hypothalamus is found just beneath the middle part of the brain. It monitors temperature of blood flowing through it. The hypothalamus produces hormones that control the pituitary gland\####Where is the medulla oblongata found in the brain and what is it's function?

- It automatically controls breathing rate and heart rate\####Where is the cerebellum found in the brain and what is it's function?

- Found underneath the cerebrum and it also has a folded cortex

- It's important for muscle coordination, posture and coordination of balance\####What is a reflex?

responses to the environment that are not processed by the brain\####Explain the blinking reflex

- A nerve impulse is sent along the sensory neurone in the trigeminal nerve to a relay neurone in the medulla oblongata

- The impulse is then passed from the relay neurone to the motor neurones in the oculomotor nerve. this sends impulses to the superior levator neurone.

- The motor neurones also sends impulses to the orbicularis oculi muscles from the facial nerve root that move your eyelids

- These muscles contract causing your eyelids to clsoe quickly and prevent your eye from being damaged\####what are the two effectors in the blinking reflex?

orbicularis oculi muscle - pulls eyes inward

superior levator palpebrae - lowers the eyelid\####Explain the knee-jerk reflex

- Stretch receptors in the quadriceps muscle detect that the muscle is being stretched

- A nerve impulse is passed along a sensory neurone, which communicates directly with a motor neurone in the spinal cord (there is no relay neurone involved)

- The motor neurone carries the nerve impulse to the effector (the quadriceps muscle) causing it to contract so the lower leg moves forwards quickly\####How do the nervous and hormonal systems coordinate 'fight or flight'?

- Nerve impulses from sensory neurones arrive at the hypothalamus activating both the hormonal system and the sympathetic nervous system

- The pituitary gland is stimulated to release a hormone called ACTH. This causes the cortex of the adrenal gland to release steroidal hormones

- The sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region of the adrenal gland

- Heart rate is increased so blood is pumped round the body faster

- The muscles around the bronchioles relax, so breathing is deeper

- Glycogen is converted to glucose, more respiration

- Erector pili muscles contract, making hairs stand on end so that the animal looks bigger

- Muscles in the arterioles supplying the skin and blood constrict, and muscles in the arterioles supplying the heart, lungs and skeletal muscles dilate\####How does the nervous system help control heart rate?

- The sinoatrial node (SAN) generates electrical impulses that cause the cardiac muscles to contract

- The rate at which the SAN fires (heart rate) is unconsciously controlled by a part of the brain called the medulla

- Animals need to alter their heart rate to respond to internal stimuli eg. to prevent fainting due to low blood pressure

- Stimuli are detected by pressure receptors and chemical receptors, eg. baroreceptors in the aorta and vena cava which are stimulated by high and low blood pressure\####How does the medulla respond to high/low blood pressure?

- High blood pressure: detected by baroreceptor. Impulses are sent to the medulla, which sends impulses along the vagus nerve. This secretes acetylcholine, which binds to receptors on the SAN

- Low blood pressure: detected by baroreceptor. Impulses are sent to the medulla, which sends impulses along the accelerator nerve. This secretes noradrenaline, which binds to the receptors on the SAN\####How does the medulla respond to high/low pH levels?

- High pH: detected by chemoreceptors. Impulses are sent to the medulla which sends impulses along the vagus nerve. This secretes acetylcholine, which binds to receptors on the SAN

- Low pH: detected by chemoreceptors. Impulses are sent to the medulla which sends impulses along the accelerator nerve. This secretes noradrenaline, which bines to receptors on the SAN\####What is the student's t-test used for?

It is used to find out whether there is a significant difference between the means of 2 data sets\####When would you reject the null hypothesis in the student's t-test?

- So you'd reject the null hypothesis\####what is the impact of adrenaline

increases heart rate and stroke volume, causes enzymes to convert glycogen into glucose in liver cells, decrease blood flow to the gut by vasoconstriction, increase blood flow to the heart and muscles by vasodilation, increase width of bronchioles by causing smooth muscles to relax.

causes heart to contract more and harder.\####What are skeletal muscles made from?

- Large bundles of long cells called muscle fibres

- The cell membrane of muscle fibre cells is called the sarcolemma

- Bits of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm (a muscle cells cytoplasm). These folds are called transverse (T) tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre

- A network of internal membranes called the sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction

- Muscle fibres have lots of mitochondria to provide the ATP that's needed for muscle contraction

- They are multinucleate (contain many nuclei)

- Muscle fibres have lots of long, cylindrical organelles called myofibrils. They're made up of proteins and are highly specialised for contraction\####What are microfibrils made up of?

- Myofibrils contain bundles of thick and thin myofilaments that move past each other to make muscles contract

- Thick myofilaments are made of the protein myosin

- Thin myofilaments are made of the protein actin\####What does a microfibril look like under a microscope?

- Dark bands contain the thick myosin filaments and some overlapping thin actin filaments. These are called A-bands

- Light bands contain thin actin filaments only. These are called I-bands\####What are sarcomeres?

Sarcomeres are short units that make up microfibrils\####What is the Z-line?

- Around the M-line is the H-zone

- The H-zone only contains myosin filaments\####Describe the sliding filament theory

- Myosin and actin filaments slide over eachother to make the sarcomeres contract, the myofilaments themselves don't 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\####What happens to the different bands in the sarcomere as it contracts?

- The A-band stays the same length

- The I-band gets shorter

- The H-zone gets shorter\####What are some features of myosin filaments?

- Myosin filaments have globular heads that are hinged, so they can move back and forth

- Each myosin head has a binding site for actin and a binding site for ATP

- Actin filaments have binding sites for myosin heads, called actin-myosin binding sites

- Two other proteins called trpomyosin and troponin are found between actin filaments

- These proteins are attached to eachother and they help the myofilaments move past eachother\####What happens to the binding sites of resting muscles?

- In a resting muscle, the actin-myosin binding site is blocked by tropomyosin, which is held in place by troponin

- So myofilaments can't slide past each other because the myosin heads can't bind to the actin-myosin binding site in the actin filaments\####How does an action potential trigger muscle contraction?

- When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma

- Depolarisation spreads down the T tubules to the sarcoplasmic reticulum

- This causes the sarcoplasmic reticulum to release stored calcium ions into the sarcoplasm

- Ca2+ ions bind to troponin, causing it to change shape. This pulls the attached tropomyosin out of the actin-myosin binding site on the actin

- This exposes the binding site, allowing the myosin head to bind

- The bond formed when the myosin head binds to an actin filament is called an actin-myosin cross bridge

- Ca2+ ions also activate the enzyme ATPase, which breaks down ATP to provide the energy needed

- The energy released from ATP moves the myosin head, which pulls the actin filament along in a kindof rowing action

- ATP also provides the energy to breaks the actin-myosin cross bridge, so that the myosin detaches itself from the actin once it's moved

- The myosin head then reattaches to a different binding site further along the actin filament

- Many cross bridges form and break very rapidly, pulling the actin along, which shortens the sarcomere, causing the muscle to contract

- The cycle will continue as long as calcium ions are present and bound to troponin\####What happens when the muscle stops being stimulated?

- Calcium ions leave their binding sites on the troponin molecules and are moved by active transport back into the sarcoplasmic reticulum

- The troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them

- This means the tropomyosin molecules block the actin myosin binding sites again

- The actin filaments slide back to their relaxed position, which lengthens the sarcomere\####What is a neuromuscular junction?

- It's a synapse between a motor neurone & a muscle cell

- Neuromuscular junctions use the transmitter acetylcholine (ACh), which binds to receptors called nicotinic cholinergic receptors

- Neuromuscular junctions work in the same way as synapses between neurones, they release a neurotransmitter, which triggers depolarization in the postsynaptic cell

- Depolarisation of a muscle cell always causes it to contract (if the threshold level is reached)

- Acetylcholinesterase (AChE) stored in clefts on the postsynaptic membrane is released to break down acetylcholine after use

\#####What happens when a chemical (eg. a drug) blocks the release of a neurotransmitter or blocks the receptor site?

- This may prevent the action potential from being passed onto the muscle, so the muscle won't contract

- This can be fatal if it affects the muscles involved in breathing, eg. the diaphragm and intercostal muscles

- If they can't contract, ventilation can't take place and the organism can't respire aerobically\####What is the structure & function of skeletal muscles?

- Skeletal muscle is also called voluntary muscle

- This is because the contraction of skeletal muscles is controlled consciously

- It's made up from muscle fibres that have many nuclei

- You can see regular cross-striations (a striped pattern) under a microscope

- Some muscle fibres contract very quickly, they're used for speed & strength but fatigue quickly

- Some muscle fibres contract slowly and fatigue slowly, they're used for endurance & posture\####What is the structure & function of involuntary muscle?

- Involuntary muscle is also called smooth muscle, this is because it doesn't have the striped appearance of skeletal muscles

- Involuntary muscle contraction is controlled unconsciously

- It's found in the walls of your hollow internal organs, eg. the gut, blood vessels. Your gut smooth muscles contract to move food along (peristalsis) and your blood vessel smooth muscles contract to reduce the flow of blood

- Each muscle fibre has one nucleus

- The muscle fibres are spindle-shaped with pointed ends and are only about 0.2mm long

- The muscle fibres contract slowly and don't fatigue\####How could you monitor muscle fatigue?

- Monitor electrical signals

- Muscles contract in response to electrical signals (nerve impulses)

- Electrical signals in muscles can be detected by electrodes placed on the skin

- The elctrodes are conncted to a computer to allow the electrical signals to be monitored

- The procedure is called electromyography and the reading it generates is called an electromyogram\####How would you carry out an electromyography procedure?

- Attach two electrodes to places on the muscle you want to record from

- A third electrode electrode goes on an inactive point (eg. the bony wrist area) to act as a control

- Switch off any other electrical equipment that you don't need as this generates 'noise' that interferes with the electrical signal from the muscle

- Connect the electrodes to an amplifier & a computer

- Keep the muscle relaxed, you should see a straight line on the electromyogram

- Then contract the muscle, you should see spikes in the graph as motor units (motor neurone & the muscle fibres it connects to) are activated to contract the msucle

- If the muscle is used to lift a weight you will see the muscle fatigue by the spikes on the trace increasing in amplitude.

- This is because your brain is trying to activate more motor units to generate the force needed to hold the weight up\####What are baroreceptors?

pressure receptors in the aorta and vena cava. they detect high or low blood pressure and send nerve impulses along sensory neurones to cardioregulatory centres in the medulla oblongata.\####what is the vagus and accelerator nerve?

2. anaerobic respiration

3. ATP-CP system\####how do action potentials trigger contraction of muscles?

1. trigger depolarisation of sarcolemma

2. electrical impulse travels down transverse tubules towards sarcoplasmic reticulum.

3. the sarcoplasmic reticulum triggers release of calcium ions.

4. calcium ions bind to troponin, causing it to change shape. this pulls the tropomyosin out of actin-myosin binding site.\####How do calcium ions initiate contraction in skeletal muscle fibers?

activates ATPase which breaks down ATP into ADP and P to release energy that moves myosin head.\####What is a sarcomere?

H zone - only contains myosin

Z line - consists of protein discs that hold microfilaments in place

A band - overlap of actin/ myosin. darker\####how does the actin-myosin binding happen?

tryomyosin is held in place by troponin molecules. when calcium ions are released by the sarcoplasmic reticulum, it binds to the troponin molecules. this causes the troponin to change the shape and release tropomyosin to expose the myosin-binding site. the myosin head already contains ATP which is converted to ADP and P. this allows it to move back into the extended position ready to spring into action. it then binds to actin and changes shape, pulling the actin and shortenining the sacromere. whilst actin and myosin are still binded, it unbinds with ADP so it can bind to a fresh ATP. it changes shape and releases actin.\####what are differences between the NMJ and synaspes