Unit 5: Responding to the Environment Flashcards
How do the receptors communicate with the effectors? (2 marks)
1) via the Nervous System
2) via the Hormonal System
Describe the 3 types of NEURONES found in the NERVOUS SYSTEM and their roles:
Sheril Mathew Really?
1) Sensory Neurones - transmit ELECTRICAL IMPULSES from receptors —> CNS
2) Motor Neurones - transmit ELECTRICAL IMPULSES from CNS —> Effectors
3) Relay Neurones - transmit ELECTRICAL IMPULSES between Sensory and Motor Neurones
Describe the entire pathway from when a stimulus is detected to the effector: (6 KEY words)
Stimulus
detected by RECEPTOR cells
electrical impulse sent along SENSORY neurone
chemicals called NEUROTRANSMITTERS take info to the next neurone
the CNS processes this information
impulse sent along MOTOR neurone
to the EFFECTOR
Nervous System Communication is… (3 marks)
LISA SIMPSON ROCKZZZ
- Localised
- Short Lived
- Rapid
Hormonal System Communication is… (3 marks)
- Wide Spread
- Long Lasting
- Slower
Define “Gland”:
a group of CELLS that are specialised to SECRETE a useful substance such as a hormone
e.g. pancreas secretes insuilin
What two factors can stimulate Glands?
1) Change in the CONCENTRATION of another substance e.g. a hormone
2) Electrical Impulses
Which receptors detect PRESSURE in your skin?
Pacinian Corpuscles
the SENSORY NERVE ENDINGS in Pacinian Corpuscles is wrapped around __________ called ________ ?
CONNECTIVE TISSUE
LAMELLAE
What happens when a Pacinian Corpuscle is stimulated?
the LAMELLAE are DEFORMED and PRESS on the SENSORY NERVE ENDING
the deformation of Pacinian Corpuscles’ Lamellae has a knock-on effect, which is…?
deformation of STRETCH-MEDIATED (so DAAAAAYUM) SODIUM CHANNELS
what happens when the STRETCH-MEDIATED SODIUM CHANNELS become deformed? (4 marks)
the SODIUM ion channels OPEN
Sodium ions DIFFUSE into the cell
creating a GENERATOR POTENTIAL
if this generator potential reaches the THRESHOLD, it triggers an ACTION POTENTIAL
What are LIGHT RECEPTORS in your EYE called? And where are they contained?
Photoreceptors
within the RETINA
What is the FOVEA?
an area of the RETINA where there are lots of PHOTORECEPTORS
Purpose of the Optic Nerve?
carries NERVE IMPULSES from the Photoreceptor cells in the Retina ———-> the BRAIN
What is the “Blind Spot”?
where the optic nerve leaves the eye - so there are no photoreceptor cells so it’s not sensitive to light
What are the two types of photoreceptor cells?
RODS and CONES
Where are the rods found and what’s the pigment present?
- in the PERIPHERAL parts of the retina
- rhodopsin
Where are the cones found and each cone ________ with ___ bipolar cell
packed together in the fovea
- synapses
- ONE
3 factors that affect the SPEED of CONDUCTION of Action Potentials?
1) Myelination
2) Axon Diameter
3) Temperature
What is a synapse?
What’s a synaptic cleft?
1) a JUNCTION between a NEURONE and the NEXT CELL
2) tiny gap between cells at a synapse
What is the voltage across the MEMBRANE at Resting Potential?
-70 mV
What is the “Refractory Period” (3 marks)
the refractory period acts as a TIME DELAY between one action potential and the next
so, the refractory period ensures ACTION POTENTIALS don’t overlap, but pass along as DISCRETE IMPULSES
this also makes action potentials UNIDIRECTIONAL
What is meant by “Action Potentials have an ALL or NOTHING nature?” (3 marks)
once the THRESHOLD is reached, an action potential will always fire with the SAME CHANGE IN VOLTAGE.
If threshold ISN’T reached, Action Potential won’t fire
the bigger the STIMULUS, action potentials are fired more FREQUENTLY
What does a Myelin Sheath consist of and what type of conduction occurs in a myelinated neurone?
Schwann cells
Saltatory Conduction
What are “Nodes of Ranvier”
tiny patches of BARE MEMBRANE between Schwann cells
Action potentials are conducted ______ along AXONS with _____ diameters because..,
QUICKER
BIGGER
there’s LESS RESISTANCE to the flow of IONS
As temperature ________ the SPEED of CONDUCTION _________ because…
INCREASES
INCREASES
ions DIFFUSE faster
Where does depolarisation occur?
Nodes of Ranvier
SYNAPTIC KNOB - where is it and what does it contain?
- a SWELLING on the presynaptic NEURONE
- contains SYNAPTIC VESICLES filled with neurotransmitters
How do SYNAPSES make sure impulses are UNIDIRECTIONAL?
receptors are only on the POSTsynaptic membrane
What is Acetylcholine and what does it bind to?
- NEUROTRANSMITTER
- C H O L I N E R G I C
receptors
Define “neuromuscular junction”:
a SYNAPSE between a MOTOR NEURONE and a MUSCLE CELL
what breaks down ACh?
enzyme AChE
Two types of summation?
- SPATIAL summation
- TEMPORAL summation
Skeletal muscles are made up of two types of ______ ______ called:
- Muscle Fibres
- SLOW twitch
- FAAAAAAAAAAAAAAST twitch
How is a nerve impulse transmitted across a cholinergic synapse? (6 marks)
- action potential stimulates volgate-gated CALCIUM👄 ion channels in the PREsynaptic neurone to OPEN
- Calcium ions diffuse into the SYNAPTIC KNOB 🚪
- Ca2+ ions causes synaptic vesicles to FUSE with PREsynaptic neurone’s MEMBRANE
- the vesicles release ACh into synaptic CLEFT
- ACh binds to cholinergic receptors in the POSTsynaptic membrane
- this causes Na+ ion channels to open and influx of Na+ ions causes an ACTION POTENTIAL if THRESHOLD if reached
Define “Sarcolemma” and “Sarcoplasm”
1) the cell MEMBRANE of muscle FIBRE cells
1) the CYPTOPLASM of muscle FIBRE cells
Define “transverse (T) tubules”
☕️↙️
Bits of the sarcolemma that FOLD INWARDS ↙️ and stick into the sarcoplasm. They SPREAD electrical impulses throughout the sarcoplasm so they REACH all parts of the MUSCLE FIBRE
Define “Sarcoplasmic Reticulum”
- internal membranes that runs through the sarcoplasm
* stores and releases Ca+ 👄 ions needed for 💪 contraction
What are the THICK and THIN myofilaments called?
THICK : ME: Myosin
Actin
What makes the Sarcomeres contract?
Myosin and Actin filaments sliding over one another
Actin filaments have binding sites for ______
Myosin HEADS 👲
In a RESTING muscle, what blocks the Actin-Myosin binding sites?
TropoMYOSIN which is held in place by Troponin
• so myofilaments can’t slide past each other
Describe the role of Calcium ions in the contraction of Sacromere:
- they bind with the tropomyosin molecule; so tropomyosin moves away from actin, to reveal binding sites on actin; allowing myosin heads to bind to exposed sites on actin filament
- activates myosin ATP–ase which hydrolyses ATP
Why do Rods give images that are less detailed?
MANY rods CONVERGE to ONE BIPOLAR CELL
Why does it take time for rod cells to recover their sensitivity to light after moving into darkness?
rhodopsin bleached
Why are rod cells less sensitive to white colour?
white has a high proportion of wavelengths to which rhodopsin not sensitive
Where is the cardiovascular centre located?
Medulla
How does an impulse reach the base of the ventricles of the heart from the SAN? (3 marks)
- it spreads through the ATRIA
- to the ATRIOVENTRICULAR NODE
- then through BUNDLE OF His
Explain how nervous control in a human can cause increased cardiac output during exercise:
- coordination via medulla of brain
- inc. impulses along SYMPATHETIC nerve
- to S.A. Node
- release of NORADRENALINE
- more IMPULSES sent from S.A Node
- INC. Heart Rate
IAA: what is it and what does it do?
Indoleacetic Acid
- an auxin that causes plants to elongate
IAA: where is it made?
What does it stand for?
Which part of the plant does it elongate?
- in the tip
- indoleacetic Acid
- SHADY side of plant
GEOTROPISM: What is it? (3 marks)
- IAA collects on LOWER side of SHOOT and ROOT
- IAA SLOWS down growth of lower side of ROOT
- IAA SPEEDS up growth on lower side of SHOOT
PHOTOTROPISM: What is it? (2 marks)
LIGHT causes IAA to accumulate on the SHADY part of the plant
Plant bends TOWARDS the LIGHT
Why grow it in SUCROSE solution rather than distilled water?
used in Respiration
How is Resting Potential of –70 mV maintained? (2 marks)
~ Sodium-Potassium Pump pumps 3 Sodium ions out of AXON and 2 Potassium ions THROUGH ACTIVE TRANSPORT
~ Membrane is MORE PERMEABLE to K+ ions than Na+ ions…so K+ ions DIFFUSE out faster
How does DEPOLARISATION TAKE PLACE?
sodium ION GATES OPEN and sodium ions rush in
What happens during REPOLARISATION?
Sodium ion channels close AND potassium channels OPEN
so potassium IONS flood IN
What is the role of calcium ions in synaptic transmission?
causes synaptic vesicles to FUSE with presynaptic neurone’s membrane
3 functions of the energy released by the mitochondria in the synaptic knob:
- active transport of ions
- reabsorption of Acetylcholine
- production of the enzyme AcetylcholinESTERASE
Why is increased cardiac output an advantage during exercise?
During respiration, MORE RESPIRATION takes place so higher cardiac output means INC. OXYGEN SUPPLY TO MUSCLES and INC. REMOVAL OF CO2 FROM MUSCLES
Why can sodium and potassium ions only cross the axon membrane through proteins?
- can’t pass through phospholipid bilayer
- cos NOT lipid soluble
After a while, you get used to a stimuli and action potentials cease. What’s the biological advantage to this?
avoids response to “background noise” 🎻🎸🎶🎵🎤🎺📢🔔
Why do rod cells require a large number of mitochondria?
- ATP required
- for the synthesis of Rhodopsin
- and to maintain active transport of ions
What’s the role of ATP and phosphocreatine in producing contraction of a muscle fibre?
• ATP allows myosin to form cross-bridge
• ‘Re-cocks’ myosin cross bridge / allows detachment from actin
• Phosphocreatine allows regeneration of ATP withOUT respiration;
Phosphocreatine releases Pi
What to the charges go through: Depolarisation –> Repolarisation –> Hyperpolarisation –> Resting Potential
if -55mV then more sodium ion channels open
Repolarisation = +30mV
Hyperpolarisation = less than -70mV
Resting Potential = -70mV
What is Spatial Summation?
When many neurones connect to one neuron.
- the small amounts of neurotransmitters released from each neurone can be enough, ALTOGETHER to reach threshold and trigger an action potential
What is Temporal Summation?
When 2 or more nerve IMPULSES arrive in quick succession from SAME PREsynaptic neurone so more neurotransmitter released into synaptic CLEFT
Define Taxis:
- directional response to a stimulus, and there’s a specific movement towards or away from this stimulus
Difference between Taxis and Tropism:
Taxis: WHOLE organism moves
Tropism: a growth in response to stimuli
