Chapter 13 Flashcards
What is the need for communication and coordination
To increase chances of survival by responding to external conditions and to ensure optimal conditions for metabolism by responding to changes in internal environment
What is cell signalling
Cell signalling is cells releasing chemicals which have an effect on target cell to communicate can be either
Locally EG neurones and synapses
Or across large distances EG hormones
What are sensory neurones and draw a diagram
Sensory neurones transport impulses from sensory receptors to the central nervous system
Should include dendrites myelin sheath around the dendron axon cell body and axon terminal
What are relay neurones and draw a diagram
Relay neurones transmit impulses between sensory and motor neurones
Should include axon terminal cell body axon and dendron and dendrites
What is a motor neurone and diagram
Motor neurones transmit impulses from the central nervous system to an effector
Should include and write cell body note around the apps on my own sheath and axon terminal
How does the myelin sheath work
Made of schwann cells the myelin sheath accident insulator which speeds are electrical impulse conduction this is because between the schwann cells there is a gap called the node of ranvier causing the impulses to jump from one node to the next which speed it up
What are the two main factors of sensory receptors
They are specific to one type of stimulus
They act as transducers they convert energy from one form to another
The four different types of sensory receptors
Mechanoreceptors- pressure and movement
Chemoreceptors- chemicals
Thermoreceptors- temperature
Photoreceptors- light
Explain how the pancinian corpuscle works
1) at resting potential the stretch mediated sodium Ion channels are too narrow to allow them through
2) when pressure is applied the membrane changes shape causing the channels to widen and Sodium ions to diffuse in
3) this depolarise is it creating a generator potential
4) this creates an action potential which is a nerve impulse
What is resting potential
Resting potential is the difference in charge between the inside and outside of an axon when the neurone is not transmitting an impulse
How is a resting potential generated
1) sodium potassium pump actively transport three sodium ions out of every 2 potassium ions in
2) most gated sodium Ion channels are closed so sodium ions cannot diffuse back into the axon down its electrochemical gradient
3) most potassium ion channels are open allowing the potassium ions to diffuse back in
4) there are more positive ions outside the axon creating a resting potential
How is an action potential generated
1) the neurone is at resting potential
2) the energy of a stimulus triggers some sodium voltage gated ion channels to open so sodium ions diffuse into the neurone down the electrochemical gradient
3) depolarisation- the potential difference threshold is reached so more sodium Ion channels open allowing more sodium ions in which is an example of positive feedback
4) repolarization at a potential difference of 40 sodium Ion channels clothes and voltage-gated potassium ion channels open so potassium ions diffuse out down their electrochemical gradient
5) hyper polarisation the potential difference becomes more negative than the resting potential due to potassium ion channels slowly closing
6) the sodium potassium pump returns the membrane to resting potential
How is an action potential transmitted
1) during an action potential Some sodium ions that diffuse in during depolarization diffuse sideways down a concentration gradient
2) this triggers depolarization in the next region and so on known as the wave of depolarization
3) the previous region undergoes a refractory period to return to resting potential
What is saltatory conduction
Myelinated neurons are faster as depolarization can only occur at the nodes of ranvier and this makes the action potential jump from one node known as saltatory conduction
What is the all or nothing principle
The all-or-nothing principle states that if the threshold is reached and action potential of the same size will be triggered a bigger stimulus won’t cause a bigger action potential but it will cause more frequent action potentials
What is a synapse
A synapse is the junction between two neurones or a neurone and an effector
What is a neurotransmitter
A neurotransmitter is a chemical involved in communication across a synapse there are two types
Excitatory neurotransmitters result in the depolarisation of postsynaptic neurons
Inhibitory neurotransmitters result in the hyper polarisation of the postsynaptic membrane
Explain the process of passing an action potential across a synapse at a cholinergic synapse
1) an action potential arrives at the end of the presynaptic neuron depolarising it and causing the calcium ion channels to open and calcium ions to enter
2) calcium ions influx causing synoptic vesicles to fuse with the presynaptic membrane and release the acetylcholine neurotransmitters into the synoptic cleft
3) acetylcholine diffuse across and fuse of receptors on the postsynaptic membrane causing sodium Ion channels to open
4) the influx of sodium Ions generate a new action potential
5) acetylcholine esterase hydrolyses the acetylcholine into choline and ethanoic acid which diffuses back into the presynaptic neurone preventing it from continually generating a new action potential
6) acetylcholine is recombined and stored in vesicles in the presynaptic neuron and the sodium Ion channels close
What is spatial summation
Spatial summation is when neurones converge so as the small amount of neurotransmitter from each can be enough to reach the threshold and trigger an action potential
What is temporal summation
Temporal summation is where two or more nerve impulses arrive in quick succession at the same presynaptic neurone building up neurotransmitters in the synoptic cleft increasing the likelihood of action potential
What is a reflex
Reflex is an involuntary response to a sensory stimulus
Draw the reflex arc
Receptor sensory neuron relay neuron motor neurone
Explain the process of the blinking reflex
1) the cornea is irritated by foreign body
2) is triggers an impulse on a sensory neurone
3) this passes through a relay neurone to the central nervous system
4) a response is sent along the motor neurone to a muscle in the eyelid
5) the eyelid shuts
Explain the process of the knee jerk reflex
1) the leg is taps just below knee cap
2) the patellar tendon detect the muscle being stretched and sends a nerve impulse on a sensory neurone
3) a motor neurone carries the impulse to the effector
4) this causes the extensor muscle to contract and a relay neuron inhabits the motor neurone of the flexor muscle causing it to relax which causes the kick
Draw the organisation of the mammalian nervous system
Mammalian nervous system
CNS (brain and spinal cord) & PNS (sensory and motor neurones)
Somatic (conscious) and autonomic (unconcious)
Sympathetic (noradrenaline fight or flight) and parasympathetic (acetylcholine rest and digest)
Draw a diagram of the brain
Should include
Cerebrum vision hearing learning thinking
Cerebellum coordinates muscles balance and posture
Medulla oblongata controls breathing and heart rate
Pituitary gland controls body glands
Hypothalamus maintains body temperature
Describe skeletal muscle and draw diagram
Skeletal muscle is striated has conscious control has a regular arrangement (so contracts in one direction) Responsible for movement and short rapid contractions
Describe cardiac muscle and draw a diagram
Specialised striated
in voluntary control
irregular branch arrangement (for simultaneous contraction)
Intermediate contractions
Describe involuntary muscle and draw a diagram
Non-striated
involuntary control
no regular arrangement (for multi directional contractions)
slow long contractions
Draw diagram of a sarcomere
Shoukd include H zone myosin sarcomere light band acting and z line
What is the sliding filament theory
During contraction the myosin filaments pull the actin towards the centre of the sarcomere
Describe the structure of myosin
Myosin have globular heads with a binding site for actin and ATP
Describe the structure of actin
Acting have binding sites for myosin heads but they are blocked by trypomyosin and held in place by Tryponin
Describe the process of muscle contraction
1) an action potential from a motor neurone stimulates a muscle cell and depolarizes the sarcolemma
2) this spreads down the t-tubules to the sarcoplasmic reticulum
3) this causes it to release calcium ion into the sarcoplasm
4) calcium ions bind to troponin causing it to change shape pulling the trypo myosin out of the actin myosin binding site
5) this releases ADP so an ATP molecule can bind and provide energy to detach the myosin head
6) calcium ions activate atpase which hydrolyzes ATP to ADP and the head returns to its original position binded by ADP
