ANIMAL RESPONSES OCR A LEVEL BIOLOGY 5.1.5

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  • Created by: Davina1st
  • Created on: 12-05-22 17:34
How is the mammalian nervous system structurally organised?
Into two systems, the CNS and the peripheral nervous system.
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What does the CNS consist of?
The brain and your spinal cord.
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What does the peripheral nervous system consist of?
All the neurones that connect the CNS to the rest of the body, sensory neurones from receptors to CNA and motor neurones from CNS to effectors.
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How is the mammalian nervous system functionally organised?
Into the somatic and autonomic nervous system.
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What is the somatic nervous system?
This system is under conscious control - it is used when you voluntarily decide to do something. e.g. when you decide to move a muscle to move your arm. It carries impulses to the body's muscles.
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What is the autonomic nervous system?
Controls the internal environment, and involuntary body functions.
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The autonomic nervous system is further divided into the sympathetic/parasympathetic nervous system. Describe both
Sympathetic - arouses body to expend energy. Parasympathetic - calms body to conserve and maintain energy.
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How does the parasympathetic change behaviour when stimulated?
Decreases heart rate, decrease airway diameter, increased blood flow to gut/stomach
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How does the sympathetic change behaviour when stimulated?
Increases heart rate, increased blood flow to muscles, increased airway diameter.
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What are the 5 main areas of the brain?
Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland.
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What is the cerebrum responsible for?
Controls voluntary actions, such as learning, memory, personality and conscious thought.
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What is the cerebellum responsible for?
Controls unconscious functions e.g. posture, balance and non-voluntary movement.
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What is the medulla oblongata responsible for?
Used in autonomic control, for example, heart rate and breathing rate.
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What is the hypothalamus responsible for?
Regulatory centre for temperature and water balance
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What is the pituitary gland responsible for?
Stores and releases hormones that regulate many body functions.
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What is the sequence of events from stimulus to response for a reflex arc?
Receptor - detects stimulus and creates action potential. Sesnory - carries impulse to spinal cord. Relay - connects to sensory to motor neruone within spinal cord/brain. Motor neurone - carries impulse to effector to carry out response.
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What is a reflex?
Involuntary response to a stimulus that usually protects the body, doesn't have to be learnt, don't involve decision making. Very fast, usually 2/3 synapses.
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How is the knee jerk reflex carried out?
Leg tapped below kneecap (patella), stretches patella tendon=stimulus. Extensor muscle contracts, relay neurone inhibits motor neurone of flexor muscle causing it to relax. Contraction and relaxation of antagonistic flexor hamstring=kick.
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How is the blinking reflex carried out?
Cornea is stimulated by being touched, triggers impulse along sensory neurone, relay neurone in lower brain stem, impulses then sent along branches of motor neurone = close eyes.
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How are reflexes a survival advantage?
Involuntary - brain able to deal with more complex responses, prevents overload. Doesn't have to be learnt =immediate protection. Fast - two synapses.
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What are the three types of muscle in the body? Describe them briefly
Skeletal - attached to bones, work antagonistically to move bones and joints, voluntary. Cardiac- only in heart, involuntary. Smooth - slowest contractions, anywhere that is muscle not under conscious control. e.g. wall of uterus.
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Muscles dont have many mitochondria. True or false?
False - they have large number of mitochondria to provide lots of ATP needed for muscle contraction.
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Describe skeletal muscle. Function, voluntary, striated, multinucleate, myocyte?
Responsible for movement, voluntary, striated, multinucleated, myocyte regularly arranged cylinder/tubular.
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Describe cardiac muscle. Function, voluntary, striated, multinucleate, myocyte?
Found only in heart, myogenic, involuntary, specialised striated, uninucleate, cells branch and inter-connect=simultaneous contraction. Tubular/inter-connecting myocyte shape.
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Describe smooth muscle. Function, voluntary, striated, multinucleate, myocyte?
Involuntary muscle cells, non-striated, uninucleate, no regular arrangement-different cells contract in different directions, spindle shaped myocyte.
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Describe skeletal muscle structure, from muscle to sarcomere.
Muscle, bundle of muscle fibres, single muscle fibre cell (myocyte), myofibril, myofilament, sarcomere.
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What is a sarcomere?
A functional unit of contraction in a myofibril.
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Is actin or myosin thick contractile fibre?
Actin- thin contractile fibres. Myosin - Thick contractile fibres.
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What is the structure and function of the T-tubules of a skeletal muscle fibre cell?
Network of tubules that run between the sarcolemma an sarcoplasmic reticulum. Controls the wave of depolarisation that causes the muscle to contract.
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What are the light and dark bands also known as?
Dark - myosin thick filaments, A band. Light - actin thin filament I-band
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What are the three parts that a thin filament is composed of?
Fibrous actin, tropomyosin - blocks active sites of actin molecules so myosin heads cant bind. Troponin - binds tropmyosi to actin fibre.
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What happens at a neuromuscular junction?
Action potential arrives, Ca2+ open and diffuse in, vesicles of neurotransmitters released by excocytosis, NT binds to receptor on Na+pump, Na+ enter motor end plate, NT diffuse along sarcolemma and open Na+ channel. Na+ enter.
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How does depolarisation of the sarcolemma lead to muscle contraction?
Wave of depolarisation spreads across sarcolemma, conducted aroudn whole myocyte by T-tubules, triggers Ca2+ to open (voltage gated), Ca2+ enter down a conc grad, bind to troponin changes shape so the tropomyosin shifted away from actin active sites.
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How des troponin changing shape expose the myosin binding sites on the actin filament?
When troponin changes shape it moves the tropomyosin away from the active sites in the actin filaments, leaving the actin filaments exposed.
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What is formed when the myosin head binds to the actin filament?
Cross-bridge = actin and myosin protein complex
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What causes the actin-myosin cross-bridge to break?
ATP binds to myosin causing it to be released from actin. ADP + Pi ---->ATP
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Describe the sequence of events that occur when a muscle relaxes
Ca2+ actively transported into the sarcoplasmic reticulum, requiring ATP, makes myosin binding sites unavailable, Cross-bridges cant form/myosin cannot move along the actin-shortening the sarcomere.
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What chnages occur to the sarcomere when the muscle relaxes?
Contract: Z lines, H zone, I band, A band, Length of sarcomere. Relax - M line
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What is ATP energy used for in muscle contraction?
Movement of myosin heads and to enable the sarcoplasmic reticulum to actively reabsorb calcium ions from the sarcoplasm.
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What are the three ways ATP is generated for muscle contraction?
Anaerobic respiration, aerobic respiration and creatine phosphate.
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What is aerobic respiration, how does it work and when is it most likely to be used?
Regenerating ATP from ADP in oxidative phosphorylation. Occurs in the presence of oxygen. Used for long periods of low-intensity exercise.
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What is anaerobic respiration, how does it work and when is it most likely to be used?
Respiration that takes place in the presence of low/no oxygen. When oxygen is used up more quickly than blood can replace it. Used for short periods of high intensity exercise.
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What is Creatine phosphate, how does it work and when is it most likely to be used?
Forms ATP from phosphorlyation of ADP. Creatine phosphate= a reserve which can readily combine with ADP reforming ATP. Used for short rigorous bursts of exercise. e.g. a tennis serve.
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Some stimuli require a complex set of responses where some are fast and short lived whilst others are slower but longer lasting. An example of this is...?
Fight or flight to stressful situations.
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What is the fight or flight response?
Responses of animals to perceived danger, to prepare them for confrontation/escape, which aids survival.
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How does the fight or flight response work? (Briefly from hypothalamus to bloodstream)
Sympathetic nervous system activates adrenal medulla=adrenaline/noradrenaline. Impulses activate glands+smooth muscle. Adrenal cortical system activated by releasing CRF, ACTH secreted from pituitary gland for 30 mins into bloodstream.
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Give three physical responses of the fight/flight response and the purpose?
Heart rate increases = pump more O2 blood around body. Pupils dilate = Take in more light for better vision. Smooth muscle of airways relaxes = more oxygen into lungs.
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Describe the action of adrenaline
Adrenaline binds to receptor on csm = adrenaline receptor complex. Activates the enzyme inside the membrane (adenylyl cyclase). Activated enzyme converts ATP to cAMP (secondary messenger) which activate other enzymes to break down glycogen = glucose.
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Is the fight/flight response involving adrenaline a cascade effect? What does this mean?
Yes it is a cascade effect. Increases the speed of a response. More enzymes can be activated at the same time.
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What are the three types of receptors and wat are they each responsible for?
Baro - aorta, carotid arteries and vena cava, detect blood pressure change. Chemo - carotid arteries, aorta medulla detect change in blood pH, Stretch - detect muscle movement.
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Why is it important that the chemo receptors detect a change in blood ph?
pH is related to carbon dioxide concentration and therefore breathing rate.
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What is the effect of exercise on the cardiac output?
More CO2 from respiring tissue, blood pH lowered, Increased impulses from medulla oblongata to SAN, SAN increases heart rate, increased blood flow removes CO2 faster.
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How is the heart hormonally controlled?
Adrenalin/ noradrenaline released from adrenal medulla, act on SAN to increase the freq of heart muscle contractions.
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What does the CNS consist of?

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The brain and your spinal cord.

Card 3

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Card 4

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How is the mammalian nervous system functionally organised?

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Card 5

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What is the somatic nervous system?

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