5.1.5 Animal Responses Flashcards
What is the role of the central nervous system?
Co-ordination of impulses
What is the role of peripheral nervous system?
Sensing stimuli from environment and controlling the effectors’ response
What is the functional organisation of the nervous system?
Somatic and Autonomic
What is the function of the somatic nervous system?
Under conscious control of voluntary motor movements and processing sensory stimuli
Carries impulses to muscle
What is the function of the autonomic nervous system?
Subconscious control - automatic movements.
Carries impulses to glands, smooth muscle and cardiac muscle
Describe the neurones in the parasympathetic nervous system
Long pre-ganglionic neurone
Short post-ganglionic neurone
Releases acetylcholine at neurotransmitter
Describe the neurones in the sympathetic nervous system
Short pre-ganglionic neurone
Long post-ganglionic neurone
Releases noradrenaline at neurotransmitter
Describe the gross structure of the brain
Protected by skull and surrounded by meninges (protective membranes)
What are the five main areas of the brain?
- Cerebrum
- Medulla oblongata
- Cerebellum
- Hypothalamus
- Pituitary gland
Describe, and state the function of, the cerebrum
Structure: The main part of the brain (split into 2 hemispheres) - highly convoluted, with an outer lining (cerebral cortex).
Function: co-ordinates voluntary, and some involuntary, movements. Different areas receive sensory input from receptors in sense organs and pass on info to association areas
State the function of the cerebellum
Co-ordinates muscular movement, balance and posture. Receives input from ears and muscles & tendons, then relays to the motor cortex in cerebrum
State the function of the medulla oblongata
Contains many regulatory systems (e.g. blood glucose conc) that control involuntary actions. Also involved in control of voluntary movements and relaying signals to CNS
State the function of the hypothalamus
Main controlling region for the ANS - has two centres for parasympathetic and sympathetic systems.
- Controls complex behaviours (e.g. sleeping, eating)
- Monitors contents of blood (glucose conc)
- Produces hormones
State the function of the pituitary gland
Controls most glands in the body, divided into 2 sections:
Anterior - produces hormones involved in growth, sexual development and skin pigmentation e.g. FSH
Posterior - stores and releases hormones made in hypothalamus - ADH, Oxytocin
State and describe an example of a spinal reflex
Knee Jerk: 1) Tap causes patellar tendon to stretch
2) Reflex arc occurs - extensor muscle on top of thigh contracts whilst flexor muscle relaxes
3) Leg kicks
For maintaining balance and posture
State and describe an example of a cranial reflex
Blinking: 1) Cornea irritated (touch) - triggers impulse to lower brain stem
2) Impulse initiates closing of eyelids (consensual response - both eyelids close)
Reflex indicates functioning of lower brain stem
What is the survival value of reflexes?
- They’re involuntary - brain can focus on complex responses
- Present from birth - immediate protection
- Extremely fast
- Many control everyday actions - e.g. staying upright and digestion
Describe the fight/flight response in response to acute stress
- Hypothalamus activates SNS
- Uses neuronal pathways to activate glands/smooth muscle (nervous) or activates adrenal medulla (hormonal)
- Release of adrenaline and noradrenaline from adrenal medulla
Describe the fight/flight response in response to chronic stress
- Hypothalamus activates adrenal-cortical system through release of CRF
- Pituitary gland secretes ACTH
- ACTH triggers release of 30 hormones at adrenal cortex
Describe the second messenger model of adrenaline
- Adrenaline binds to receptor site on target cell membrane - activates adenylyl cyclase
- Enzyme triggers ATP conversion to cAMP
- Increase in cAMP activates protein kinases that activate more enzymes (cascade effect)
Explain the hormonal control of heart rate
Stress hormones (adrenaline and noradrenaline) increase the heart rate by increasing frequency of impulses by SAN
Explain the nervous control of heart rate
Two centres in Medulla Oblongata: One INCREASES heart rate - impulse to SNS via accelerator nerve
One DECREASES heart rate - impulse to PNS via vagus nerve
What are chemoreceptors? Explain their role in controlling heart rate.
Receptors sensitive to chemical changes e.g. pH. Located in carotid artery, aorta and medulla.
CO2 levels INCREASE - pH DECREASE - MORE impulses to medulla oblongata and for SAN stimulation
CO2 levels DECREASE - pH INCREASE - LESS impulses for SAN stimulation and to medulla oblongata
What are baroreceptors?
Receptors sensitive to (blood) pressure changes.
Located in carotid artery, aorta and vena cava.
BP INCREASE - reduced frequency of SAN stimulation
BP DECREASE - greater frequency of SAN stimulation
Describe the structure of skeletal muscle
Striated, multi-nucleated muscle fibres bundled together, surrounded by plasma membrane (sarcolemma). Muscle fibres made up of myofibrils (made up of actin and myosin filaments). Shared cytoplasm is sarcoplasm.
Parts of sarcolemma fold in to form T tubules to help spread impulses through sarcoplasm at same time
What is the function of skeletal muscle?
Conscious control of voluntary muscle
Responsible for locomotion
Describe the structure of cardiac muscle?
Specialised striated, uni-nucleated fibres - cells branch and interconnect for simultaneous contraction. Much fainter striations than skeletal muscle
What is the function of cardiac muscle?
Maintain involuntary regular heart rate (myogenic)
Describe the structure of involuntary (smooth) muscle
Non-striated, uni-nucleated, spindle shaped fibres - no regular arrangement.
What is the function of involuntary (smooth) muscle?
Allow for control of essential mechanisms without conscious thought, e.g. peristalsis, breathing (blood vessel walls)
What is the difference between slow and fast twitch muscle?
Slow - uses oxygen as fuel for continuous contractions e.g. legs
Fast - uses anaerobic metabolism for fuel - appear less red than slow twitch e.g. eyelids
What are some similarities between the action of synapses and neuromuscular junctions?
- Release neurotransmitters across synaptic gap
2. Enzymes present that break down neurotransmitter
What are some differences between the action of synapses and neuromuscular junctions?
- Neuromuscular junctions have more receptors on post-synaptic membrane
- Action potential from neuromuscular junction always triggers a response, synapse could be inhibitory
- Neuromuscular junction causes muscular contraction, synapse causes nerve impulse
- One muscle fibre for each neuromuscular junction, but synapses could provide neurotransmitters to multiple post-synaptic neurones
Describe the action of neuromuscular junctions
- Acetylcholine released by synaptic vesicles into synaptic cleft - binds to receptors on sarcolemma of muscle fibre
- Binding causes opening of Na+ channels - depolarises muscle fibre, spreads along sarcolemma and down T-tubules
- Action potential triggers release of Ca2+ from sarcoplasmic reticulum
- Acetylcholine esterase breaks down acetylcholine into choline and acetyl (ethanoic acid) - diffuse back into neurone
Describe the sliding filament model
- Without enough Ca2+ present, tropomyosin blocks actin binding sites - myosin head can’t attach
- Ca2+ (released from sarcoplasmic reticulum) binds to troponin - changes tertiary structure, resulting in tropomyosin not blocking the binding site
- ATP is bound to myosin - hydrolyses to ADP and Pi for energy for ‘cocked’ positioning of head
- Cross-bridges form between actin and myosin head
- Release of Pi causes conformational change in head - moves actin along (power stroke)
- ADP released, ATP binds to myosin head - detaches from binding site
- ATP hydrolysed to ADP and Pi, so head moves back to original position
What occurs when the stimulation of the muscle stops?
Without the release of acetylcholine, Ca2+ is transported back into the sarcoplasmic reticulum. Tropomyosin blocks active sites again
How does creatine phosphate maintain the ATP supply?
Acts as a reserve of Pi - binds with ADP to form ATP and creatine. Only for short bursts of vigorous exercise - store used up quickly. Replenished when relaxed - Pi from ATP hydrolysis
What are the sources of creatine phosphate?
- Meat
2. Internal production by liver and kidneys
What changes occur in the sarcomere when contracted?
H zone narrows
Dark (A) band remains the same, Light (I) band shortens
Z lines are closer together
What’s the difference between actin and myosin’s connection to the Z line?
Actin connects directly to Z line
Titin molecules connect myosin to Z-line
